全文获取类型
收费全文 | 134篇 |
免费 | 9篇 |
专业分类
林业 | 6篇 |
农学 | 2篇 |
基础科学 | 2篇 |
5篇 | |
综合类 | 22篇 |
农作物 | 4篇 |
畜牧兽医 | 95篇 |
园艺 | 3篇 |
植物保护 | 4篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有143条查询结果,搜索用时 31 毫秒
71.
72.
To evaluate the sufficiency of US federal critical habitat designations and a proposed conservation plan in promoting the long-term persistence of the endangered plant Astragalus albens, patterns of genetic diversity and landscape connectivity were examined. A. albens harbors substantial genetic variation and shows no evidence of historic bottlenecks, suggesting little risk of extinction due to genetic homogeneity (A = 2.40; P = 0.50) or inbreeding (f = −0.08) within occurrences. Low genetic differentiation among occurrences (θp = 0.01) indicates relatively high gene flow or little genetic drift. The 91 patches of A. albens were connected into a single network at a distance of 2100 m; 94% of patches were <1000 m from at least one other patch. Managing ecological conditions that maintain large population sizes and connectivity among populations throughout the species’ ecological and geographic ranges will most likely conserve existing diversity. Both reserve networks partially accomplish these goals by including most extant occurrences and >89% of the aerial extent of the species, including the largest populations, and capturing all detected alleles. However, both conservation networks fail to conserve occurrences from one portion of the species’ range, possibly speeding loss of unique local adaptations. In addition, connectivity of the whole network is reduced with the 65 patches designated as critical habitat being connected at a distance of 6200 m and the proposed reserve sites being connected at a distance of 9500 m. Although total network connectivity would be reduced, connectivity at scales most relevant to gene flow (e.g., <1000 m) remains sufficiently in tact to provide a relatively promising outlook for species persistence. 相似文献
73.
Inhibition of development of gastro-intestinal trichostrongylid worms was studied using successive groups of tracer calves and groups of continuously grazed calves over one year in the Tully area of North Queensland lowland wet tropics. The results, assessed by means of worms from these calves recovered at necropsy 3 weeks after their removal from pastures, showed inhibition in the development of Haemonchus placei and Cooperia punctata at the early fourth stage at the approach to and during the relatively dry period in the area. Inhibition was however minor and inhibited larvae formed but only a small percentage of worm burdens in both categories of calves, indicating that they were not in any way of major epidemiological importance. It was suggested that the minor nature of inhibition was due to the mild climatic conditions which could not produce appropriate conditioning treatment, or caused only mild selection pressure for inhibition in the area. 相似文献
74.
Cowgill E Neel J 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2003,32(3):147-149
A 12-year-old neutered male Shar-Pei was presented to the North Carolina State University Veterinary Teaching Hospital cardiology service with a 2-week history of coughing and a 2-day history of lethargy and anorexia. Pleural effusion and a mediastinal mass were detected with thoracic radiographs. Ten mL of fluid were removed via thoracocentesis, and cytologic examination of the fluid revealed marked eosinophilic inflammation and few atypical mast cells. Mast cell neoplasia was suspected. Aspirates of the mediastinal mass, abdominal lymph nodes, and bone marrow contained similar pleomorphic mast cells and increased numbers of eosinophils. The dog was diagnosed with systemic (visceral) mastocytosis, a rare form of neoplasia in dogs, and was euthanized. These tumors carry a poor to grave prognosis and the etiology is uncertain. 相似文献
75.
76.
C.?M.?FeldhakeEmail author J.?P.?S.?Neel D.?P.?Belesky E.?L.?Mathias 《Agroforestry Systems》2005,65(3):231-239
The Appalachian region is characterized by hilly topography and a humid temperate climate. In most areas agriculture is limited
to pasture although the native climax vegetation is a species-diverse forest. Silvopasture systems can help diversify and
increase farm income. Information is needed on the yield response of forage grown as an understory crop among trees. The light
environment of a conifer silvopasture was characterized by three methods, a hand-held photosynthetically active radiation
(PAR) meter for quick measurements over a large area, fixed PAR meters recorded using data loggers for a large number of measurements
over time, and hemispherical photography with software to calculate seasonal direct beam radiation. Light data were considered
in terms of forage yield. Plots were harvested when forage reached 20–25 cm in height after which the entire area was grazed
by sheep. There were limitations to all methods of quantifying radiation environment for predicting yield. Yield decreased
linearly with decreased PAR; however, data variability was high and correlations, while statistically significant, were weak.
Grazed silvopastures are dynamic with shifting yield patterns in response to the interactions between the spatially variable
soil, changing seasonal environment, and spatially variable animal impacts for each grazing event. 相似文献
77.
Microsite conditions influence plant development and resource allocation of Dactylis glomerata L. (orchardgrass), a traditional pasture species with potential as an understory crop in woodlots. A field experiment was
conducted to determine how open (O), shaded woodland (W) and open-to-shaded woodland transition zone (EO, EW) microsites influenced the quantity and distribution of nonstructural carbohydrate (TNC) and crude protein (CP) among plant
parts of defoliated orchardgrass. Plants established in spring (SP) or late summer (LS) were clipped each time mean sward
height reached 20 cm. Microsite conditions influenced nutritive value of herbage. Nutritive value was acceptable when not
more than 45–50% light attenuation (as a function of shading by nearby trees) occurred relative to open pasture. Twice as
much TNC accumulated in stembases of LS compared to SP plants. Concentrations of TNC were least in plants growing at W, regardless
of planting time. Stembase TNC depletion occurred in SP plants, regardless of microsite, and LS plants growing at W. CP concentrations
were greater in herbage from W compared to O sites, suggesting the N needs of the plant were met with minimal fertilizer N
inputs. The ratio of C:N and thus herbage energy expressed as total digestible nutrients (TDN), relative to CP declined as
shade increased. Increased protein content is offset by lower fiber, lower nonstructural carbohydrate and the possibility
of reduced preference by grazers. Nutritive value is improved by modest amounts of shade relative to plants growing in full
sunlight, and allowing cool temperate origin grasses to vernalize is beneficial in terms of productivity, nutritive value,
and persistence.
Ths US Government’s right ot retain a non-exclusive, royaltyfree license in and to any copyright is acknowledged. 相似文献
78.
Duckett SK Neel JP Sonon RN Fontenot JP Clapham WM Scaglia G 《Journal of animal science》2007,85(10):2691-2698
Angus-cross steers (n = 198; 270 kg; 8 mo) were used in a 3-yr study to assess the effects of winter stocker growth rate and finishing system on 9-10-11th-rib composition, color, and palatability. During the winter months (December to April), steers were randomly allotted to 3 stocker growth rates: low (0.23 kg/d), medium (0.45 kg/d), or high (0.68 kg/d). At the completion of the stocking phase, steers were allotted randomly within each stocker growth rate to a high concentrate (CONC) or to a pasture (PAST) finishing system. All steers were finished to an equal time endpoint to minimize confounding due to animal age. At the end of the finishing phase, steers were transported to a commercial packing plant for slaughter and a primal rib (NAMP 107) was removed from 1 side of each carcass. The 9-10-11th-rib section was dissected into lean, fat, and bone, and LM samples were analyzed for palatability and collagen content. Hot carcass weight and 9-10-11th-rib section weight were greater (P = 0.01) for high than low or medium. Winter stocker growth rate did not alter 9-10-11th rib composition. The percentage of fat-free lean, including the LM and other lean trim, was greater (P = 0.001) for PAST than CONC. Total fat percentage of the 9-10-11th-rib section was 42% lower (P = 0.001) for PAST than CONC due to lower percentages of s.c., intermuscular, and i.m. fat. The percentage of total bone in the 9-10-11th-rib section was greater (P = 0.001) for PAST than CONC. Finishing beef cattle on PAST increased (P = 0.001) the percentage of lean and bone and reduced (P = 0.001) the percentage of fat in the carcass based on published prediction equations from 9-10-11th rib dissection. Stocker growth rate did not influence the objective color scores of LM or s.c. fat. Longissimus muscle color of PAST was darker (lower L*; P = 0.0001) and less red (lower a*; P = 0.002) than CONC. Juiciness scores were greater (P = 0.02) for CONC than PAST. Initial and overall tenderness scores as well as Warner-Bratzler shear force values did not differ (P > or = 0.28) among finishing systems. Beef flavor intensity was lower (P = 0.0001) and off-flavor intensity greater (P = 0.0001) for PAST than CONC. Total collagen content was greater (P = 0.0005) for PAST than CONC; however, there were no differences in percentage soluble or insoluble collagen. Growth rate during the winter stocker period did not influence rib composition, color, or beef palatability. Finishing steers on forage reduced fat percentages in the rib and LM without altering tenderness of beef steaks. 相似文献
79.
Snyder LA Tarigo JL Neel JA 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2007,36(4):379-381
A 9-year-old spayed female German Shepherd dog with a history of orthopedic disease was presented to the North Carolina State University Veterinary Teaching Hospital for evaluation of recent, progressive, bilateral, hindlimb ataxia. Analysis of cisternal and lumbar cerebrospinal fluid (CSF) samples revealed normal total nucleated cell counts and a mild increase in protein concentration in the lumbar sample. In cytocentrifuged specimens of both CSF samples, aggregates of refractile, angular to irregular, pale blue to colorless, crystalline material were observed in the background. Some of the material appeared birefringent under polarized light. Differentials for the material included contrast agent, epidural anesthetics or other pharmacologic agents, or artifact introduced through sample processing, collection, or handling. Based on investigation of clinical and laboratory processes it was determined that tubes used to collect CSF in the hospital recently had been changed from additive-free glass tubes to silica-coated shatter-resistant plastic tubes (BD Vacutainer Plus serum tubes, silicone-coated, Becton Dickinson). A cytocentrifuged preparation of saline placed in a silica-coated tube contained crystalline material identical to that observed in the CSF samples; saline placed in an additive-free glass tube contained no material. In this case, we document the microscopic appearance of highly concentrated silica particles in cytocentrifuged preparations of CSF and underscore the importance of recognizing and identifying this artifact in cytologic preparations. 相似文献
80.
Dogs with and without lymphoma have undergone hematopoietic cell transplantation in a research setting for decades. North Carolina State University is currently treating dogs with B- and T-cell lymphoma in a clinical setting with autologous peripheral blood progenitor cell transplants, using peripheral blood CD34+ progenitor cells harvested using an apheresis machine. Complete blood counts were performed daily for 15 to 19 days posttransplantation to monitor peripheral blood cell nadirs and subsequent CD34+ cell engraftment. This study documents the hematologic toxicities of total body irradiation in 10 dogs and the subsequent recovery of the affected cell lines after peripheral blood progenitor cell transplant, indicating successful CD34+ engraftment. All peripheral blood cell lines, excluding red blood cells, experienced grade 4 toxicities. All dogs had ≥ 500 neutrophils/μl by day 12, while thrombocytopenia persisted for many weeks. All dogs were clinically normal at discharge. 相似文献