全文获取类型
收费全文 | 1765篇 |
免费 | 114篇 |
专业分类
林业 | 50篇 |
农学 | 15篇 |
基础科学 | 7篇 |
132篇 | |
综合类 | 364篇 |
农作物 | 55篇 |
水产渔业 | 34篇 |
畜牧兽医 | 1163篇 |
园艺 | 18篇 |
植物保护 | 41篇 |
出版年
2021年 | 16篇 |
2020年 | 35篇 |
2019年 | 29篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 30篇 |
2013年 | 67篇 |
2012年 | 61篇 |
2011年 | 67篇 |
2010年 | 42篇 |
2009年 | 55篇 |
2008年 | 67篇 |
2007年 | 76篇 |
2006年 | 76篇 |
2005年 | 67篇 |
2004年 | 64篇 |
2003年 | 74篇 |
2002年 | 62篇 |
2001年 | 43篇 |
2000年 | 52篇 |
1999年 | 35篇 |
1998年 | 35篇 |
1997年 | 20篇 |
1996年 | 12篇 |
1995年 | 21篇 |
1994年 | 18篇 |
1992年 | 43篇 |
1991年 | 42篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 32篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1981年 | 11篇 |
1979年 | 15篇 |
1977年 | 11篇 |
1974年 | 16篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 10篇 |
1970年 | 14篇 |
1969年 | 21篇 |
1968年 | 12篇 |
1967年 | 11篇 |
1966年 | 18篇 |
排序方式: 共有1879条查询结果,搜索用时 265 毫秒
991.
A literature review of reports of the stability and storage of common injectable chemotherapy agents used in veterinary patients 下载免费PDF全文
Many chemotherapy drugs used in human patients are discarded after single use or within 24 h of reconstitution, as per the manufacturer's product label recommendations. This can be wasteful and costly to veterinary clients. This report reviews the published stability and storage data for 19 injectable chemotherapy drugs commonly used in veterinary medicine. Based on these data, storage procedures are presented, assuming aseptic technique and a closed system drug transfer device (CSDTD) are used for drug preparation and handling. Further studies on the risk of microbiological contamination of chemotherapeutics using a CSDTD, and validated high quality drug assays such as stability‐indicating high‐performance liquid chromatography, are required. The authors' intent is not to supersede product label recommendations, but to suggest that longer storage without significant loss of drug efficacy may be possible, thus reducing the costs of chemotherapeutics to some veterinary clients. 相似文献
992.
David J.P. Moore Jia Hu William J. Sacks David S. Schimel Russell K. Monson 《Agricultural and Forest Meteorology》2008,148(10):1467-1477
Modeling how the role of forests in the carbon cycle will respond to predicted changes in water availability hinges on an understanding of the processes controlling water use in ecosystems. Recent studies in forest ecosystem modeling have employed data-assimilation techniques to generate parameter sets that conform to observations, and predict net ecosystem CO2 exchange (NEE) and its component processes. Since the carbon and water cycles are linked, there should be additional process information available from ecosystem H2O exchange. We coupled SIPNET (Simple Photosynthesis EvapoTranspiration), a simplified model of ecosystem function, with a data-assimilation system to estimate parameters leading to model predictions most closely matching the net CO2 and H2O fluxes measured by eddy covariance in a high-elevation, subalpine forest ecosystem. When optimized using measurements of CO2 exchange, the model matched observed NEE (RMSE = 0.49 g C m−2) but underestimated transpiration calculated independently from sap flow measurements by a factor of 4. Consequently, the carbon-only optimization was insensitive to imposed changes in water availability. Including eddy flux data from both CO2 and H2O exchange to the optimization reduced the model fit to the observed NEE fluxes only slightly (RME = 0.53 g C m−2), however this parameterization also reproduced transpiration calculated from independent sap flow measurements (r2 = 0.67, slope = 0.6). A significant amount of information can be extracted from simultaneous analysis of CO2 and H2O exchange, which improved the accuracy of transpiration estimates from measured evapotranspiration. Conversely, failure to include both CO2 and H2O data streams can generate results that mask the responses of ecosystem carbon cycling to variation in the precipitation. In applying the model conditioned on both CO2 and H2O fluxes to the subalpine forest at the Niwot Ridge AmeriFlux site, we observed that the onset of transpiration is coincident with warm soil temperatures. However, after snow has covered the ground in the fall, we observed significant inter-annual variability in the fraction of evapotranspiration composed of transpiration; evapotranspiration was dominated by transpiration in years when late fall air temperatures were high enough to maintain photosynthesis, but by sublimation from the surface of the snowpack in years when late fall air temperatures were colder and forest photosynthetic activity had ceased. Data-assimilation techniques and simultaneous measurements of carbon and water exchange can be used to quantify the response of net carbon uptake to changes in water availability by using an ecosystem model where the carbon and water cycles are linked. 相似文献
993.
Shoshanah M. Inwood Jeff S. Sharp Richard H. Moore Deborah H. Stinner 《Agriculture and Human Values》2009,26(3):177-191
Chefs have been recognized as potentially important partners in efforts to promote local food systems. Drawing on the diffusion
of innovation framework we (a) examine the characteristics of chefs and restaurants that have adopted local foods; (b) identified
local food attributes valued by restaurants; (c) examine how restaurants function as opinion leaders promoting local foods;
(d) explored network linkages between culinary and production organizations; and (e) finally, we consider some of the barriers
to more widespread adoption of local foods in the culinary community. Analyzing quantitative and qualitative data collected
from interviews with individuals from 71 restaurants, we compare and contrast restaurants that utilize relatively large amounts
of locally-produced ingredients with restaurants using few, if any, local products. Results reveal that chefs are most interested
in intrinsic food qualities, such as taste and freshness, and less interested in production standards. As opinion leaders,
chefs utilize signage, wait staff, and cooking classes to promote local foods; however, the diffusion process across restaurants,
and between restaurants and producers, is limited by network associations. Structural barriers such as distribution problems
and lack of convenience were identified as limiting more widespread use of locally-grown foods. We offer several implications
of this research for further work that seeks to engage chefs as opinion leaders who are important to building greater support
for local food systems.
Shoshanah M. Inwood is a Ph.D. candidate in Rural Sociology at The Ohio State University. Her research focuses on sustainable agriculture, organic agriculture, agricultural change at the rural–urban interface, farm succession, and local food system development. Jeff S. Sharp is an associate professor of Rural Sociology at The Ohio State University. His research interests include community and agricultural change at the rural–urban interface. Richard H. Moore is a professor in the Department of Human and Community Resource Development at Ohio State University where he leads the Sugar Creek Research Team. Deborah H. Stinner is a research scientist and the administrative coordinator of the Organic Food and Farming Education and Research Program (OFFER) at The Ohio State University’s Ohio Agriculture Research and Development Center in Wooster, OH. 相似文献
Shoshanah M. InwoodEmail: |
Shoshanah M. Inwood is a Ph.D. candidate in Rural Sociology at The Ohio State University. Her research focuses on sustainable agriculture, organic agriculture, agricultural change at the rural–urban interface, farm succession, and local food system development. Jeff S. Sharp is an associate professor of Rural Sociology at The Ohio State University. His research interests include community and agricultural change at the rural–urban interface. Richard H. Moore is a professor in the Department of Human and Community Resource Development at Ohio State University where he leads the Sugar Creek Research Team. Deborah H. Stinner is a research scientist and the administrative coordinator of the Organic Food and Farming Education and Research Program (OFFER) at The Ohio State University’s Ohio Agriculture Research and Development Center in Wooster, OH. 相似文献
994.
Diagnosis of psittacosis (infection with Chlamydia psittaci) has traditionally been dependent upon culture or demonstration of chlamydiae in tissues by cytochemical stains such as the Gimenez or Macchiavello's stain. In this study, a peroxidase-antiperoxidase (PAP) technique that employs a commercially available monoclonal antibody directed against Chlamydia is used to demonstrate chlamydiae in the necropsy tissues of nine birds. Chlamydiae were identified in air sacs (83%), liver (78%), spleen (78%), small intestines (67%), large intestines (44%), and kidneys (33%). Usually chlamydiae were associated with microscopic lesions, but in 75% of large intestines examined, organisms were identified within the lumen of histologically normal intestine. PAP studies revealed numerous chlamydiae that were inapparent in hematoxylin-and-eosin-stained sections. These results demonstrate the utility and sensitivity of the PAP method in the identification of chlamydiae in microscopic sections. 相似文献
995.
Evaluation of three applanation tonometers in dogs 总被引:1,自引:0,他引:1
D R Priehs G G Gum R D Whitley L E Moore 《American journal of veterinary research》1990,51(10):1547-1550
The Mackay-Marg, Tono-Pen, and Challenger applanation tonometers were evaluated in vivo in 12 clinically normal eyes of 6 dogs. Tonometric measures of intraocular pressure (IOP) were compared with closed manometric IOP measurements from the anterior chamber of anesthetized dogs. The tonometers were evaluated at IOP that ranged from 5 to 100 mm of Hg. The Mackay-Marg tonometer was the most reliable instrument when evaluated at IOP from 5 to 100 mm of Hg (r2 = 0.996) and from 10 to 30 mm of Hg (r2 = 0.962). The Tono-Pen tonometer was also reliable (r2 = 0.967) over the range of IOP, but consistently overestimated IOP at lower pressures and underestimated IOP at higher pressures. The Mackay-Marg and Tono-Pen measurements were essentially linear. When evaluated from 10 to 30 mm of Hg, r2 was 0.828 for the Tono-Pen tonometer. The Challenger tonometer, although reliable over the full range of IOP (r2 = 0.965), proved to be less accurate, as indicated by lack of a good linear equation. 相似文献
996.
Over a 24-month period, serum tumor necrosis factor (TNF) activity was determined in 289 horses with colic attributable to gastrointestinal tract disease. Serum TNF activity was quantitated by use of a modified in vitro cytotoxicity bioassay, using WEHI 164 clone-13 murine fibrosarcoma cells. Causes for colic, determined by clinical and laboratory evaluation, exploratory celiotomy, or necropsy included: gastrointestinal tract rupture (GTR); ileal impaction; small intestinal strangulating obstruction (SIO); proximal enteritis (PE); transient small intestinal distention; large-colon displacement; large-colon volvulus; large-colon impaction; colitis; small-colon obstruction; peritonitis; and unknown. Each diagnosis was placed into 1 of 3 lesion categories: inflammatory disorders (GTR, PE, colitis, peritonitis); strangulating intestinal obstruction (SIO, large-colon volvulus); and nonstrangulating intestinal obstruction (ileal impaction, transient small intestinal distension, large-colon displacement, large-colon impaction, small-colon obstruction, unknown). The prevalence of high serum TNF activity and/or mortality were evaluated. Differences were tested at significance level of P less than 0.05. Approximately 20% of the 289 horses has serum TNF activity greater than that found in clinically normal horses (greater than 2.5 U/ml). Twenty-three horses (8%) had marked increase in serum TNF activity (greater than or equal to 10 U/ml) which was more prevalent among horses with SIO and PE than in horses of other diagnostic groups, except those with GTR. Mortality and marked increase in serum TNF activity were greater in horses with intestinal inflammatory disorders or strangulating intestinal obstruction than in horses with nonstrangulating intestinal obstruction.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
997.
998.
R M Moore R K Schneider J Kowalski L R Bramlage L M Mecklenburg C W Kohn 《Equine veterinary journal》1992,24(6):450-456
Bacterial culture and susceptibility results were analysed from 233 horses with septic arthritis/tenosynovitis or osteomyelitis that developed after fracture repair. Antibiotics were deemed highly effective, effective or ineffective if > or = 85%, 70-84.9% or < 70% of the isolates were susceptible respectively. In total, 424 bacterial types were isolated; 386 were aerobic or facultative and 38 were anaerobic. Enterobacteriaceae (28.8%) were the most common bacterial group isolated, followed by non-beta-haemolytic streptococci (13.0%), coagulase-positive staphylococci (11.8%), beta-haemolytic streptococci (9.4%), and coagulase-negative staphylococci (7.3%). The remainder of the organisms were other Gram-negative (15.8%), other Gram-positive (2.3%) and miscellaneous (2.6%) bacteria. Penicillin and ampicillin were highly effective against beta-haemolytic streptococci, but were ineffective against other bacteria. Ampicillin was no more effective than penicillin against most bacteria. Amikacin was the most effective antibiotic against the wide range of bacteria isolated in this study. Amikacin was highly effective against coagulase-positive staphylococci, Enterobacteriaceae and Pseudomonas and was effective against coagulase-negative staphylococci and Actinobacillus. Gentamycin was not highly effective against any bacterial group; but was effective against coagulase-positive and negative staphylococci, Pseudomonas, Salmonella and Actinobacillus. Kanamycin was ineffective against all bacteria with the exception of Actinobacillus. Cephalothin was highly effective against beta-haemolytic streptococci, coagulase-positive staphylococci and Actinobacillus and was effective against coagulase-negative staphylococci.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
999.
1000.
Using a pump-perfused extracorporeal isolated digital preparation, the effects of a 30-minute infusion of either saline solution (control) or endotoxin on equine digital hemodynamics and microvascular function were determined. Digital blood flow and arterial, venous, and capillary pressures were recorded at 15-minute intervals for 150 minutes. From these data, total vascular resistance and pre- and postcapillary resistances were calculated. Isogravimetric capillary filtration coefficient, vascular compliance, and the osmotic reflection coefficient were determined after the last hemodynamic measurements were taken. Changes in hemodynamic values of control equine digits were not observed. During the 120 minutes after infusion of endotoxin, digital blood flow decreased 43%, and total vascular resistance increased 89%. Precapillary resistance increased 122%, but postcapillary resistance did not change significantly. Changes in vascular compliance or the capillary filtration coefficient were not observed in response to either treatment. The osmotic reflection coefficient, an index of permeability, did not differ significantly between digits of the endotoxin-treated and control groups. These data indicate that the increase in vascular resistance during endotoxemia may have been attributable to arterial/arteriolar constriction and that neither the permeability nor the surface area of the exchange vasculature within the digit was significantly affected by endotoxin. Although marked alterations in vascular function are seen after administration of endotoxin, these changes do not parallel those documented in association with experimentally induced laminitis. 相似文献