全文获取类型
收费全文 | 870篇 |
免费 | 67篇 |
专业分类
林业 | 39篇 |
农学 | 6篇 |
88篇 | |
综合类 | 118篇 |
农作物 | 26篇 |
水产渔业 | 46篇 |
畜牧兽医 | 542篇 |
园艺 | 9篇 |
植物保护 | 63篇 |
出版年
2023年 | 6篇 |
2021年 | 6篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 17篇 |
2014年 | 16篇 |
2013年 | 48篇 |
2012年 | 35篇 |
2011年 | 34篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 34篇 |
2007年 | 28篇 |
2006年 | 29篇 |
2005年 | 34篇 |
2004年 | 43篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1996年 | 10篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 21篇 |
1986年 | 28篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1979年 | 8篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 9篇 |
1971年 | 12篇 |
1970年 | 5篇 |
1969年 | 12篇 |
1968年 | 7篇 |
1966年 | 6篇 |
排序方式: 共有937条查询结果,搜索用时 15 毫秒
31.
Denise A. Elliott Richard W. Nelson Edward C. Feldman Larry A. Nea 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1997,11(3):161-165
Blood glycosylated hemoglobin (GHb) concentration was quantified in 84 healthy cats, 9 cats with stress-induced hyperglycemia, 37 cats with newly diagnosed diabetes mellitus, and 122 diabetic cats treated with insulin or glipizide. Diabetic control was classified as good or poor in insulin-treated or glipizide-treated cats based on review of history, physical examination findings, changes in body weight, and measurement of blood glucose concentrations. Blood GHb concentration was determined using an affinity chromatography assay. Mean blood GHb concentration was similar for healthy normoglycemic cats and cats with transient, stress-induced hyperglycemia, but was significantly (P < .001) higher in untreated diabetic cats when compared with healthy normoglycemic cats. Mean blood GHb concentration was significantly (P < .001) higher in 84 cats with poorly controlled diabetes mellitus when compared with 38 cats in which the disease was well controlled. Mean blood GHb concentration decreased significantly (P < .01) in 6 cats with untreated diabetes mellitus after insulin and dietary treatment. A similar significant (P < .01) decrease in mean blood GHb concentration occurred in 7 cats with poorly controlled diabetes mellitus after diabetic control was improved by an increase in insulin dosage from 1.1 ± 0.9 to 1.4 ± 0.6 U/kg/ 24 h and by feeding a diet containing increased fiber content and in 6 cats with transient diabetes mellitus 8.2 ± 0.6 weeks after discontinuing insulin treatment. There was a significant (P< .01) stress-induced increase in mean fasting blood glucose concentration and mean blood glucose concentration for 12 hours after administration of insulin or glipizide but no change in mean blood GHb concentration in 5 docile diabetic cats 12.2 ± 0.4 weeks after the cats became fractious as a result of frequent hospitalizations and blood samplings. Results of this study suggest that evaluation of blood GHb concentration may be a clinically useful tool for monitoring glycemic control of diabetes in cats. 相似文献
32.
33.
Research needs for restoring seasonal tropical forests in Thailand: accelerated natural regeneration
Accelerated natural regeneration (ANR) is a relatively cheap method of reforestation, which encourages natural establishment of indigenous trees and shrubs. It requires a low input of labour, but a high input of ecological information. In this paper, the knowledge required to predict and manipulate the natural regeneration of seasonal tropical forest is reviewed and areas in need of further research are identified. Regeneration will be influenced by five groups of potentially limiting factors; site resources (soil and microclimate); competition with weeds; site disturbance; occurrence of established woody plants or their propagules; seed dispersal by wild animals and birds. This paper considers each of these, their interactions with seasons, and each other. Collation of existing information on these topics, combined with the suggested further research, should facilitate the creation of tools that will enable practitioners to judge the regeneration potential of sites and to select the most appropriate ANR techniques. 相似文献
34.
L. Pelligand J. N. King V. Hormazabal P. L. Toutain J. Elliott P. Lees 《Journal of veterinary pharmacology and therapeutics》2014,37(4):354-366
Robenacoxib and ketoprofen are acidic nonsteroidal anti‐inflammatory drugs (NSAIDs). Both are licensed for once daily administration in the cat, despite having short blood half‐lives. This study reports the pharmacokinetic/pharmacodynamic (PK/PD) modelling of each drug in a feline model of inflammation. Eight cats were enrolled in a randomized, controlled, three‐period cross‐over study. In each period, sterile inflammation was induced by the injection of carrageenan into a subcutaneously implanted tissue cage, immediately before the subcutaneous injection of robenacoxib (2 mg/kg), ketoprofen (2 mg/kg) or placebo. Blood samples were taken for the determination of drug and serum thromboxane (Tx)B2 concentrations (measuring COX‐1 activity). Tissue cage exudate samples were obtained for drug and prostaglandin (PG)E2 concentrations (measuring COX‐2 activity). Individual animal pharmacokinetic and pharmacodynamic parameters for COX‐1 and COX‐2 inhibition were generated by PK/PD modelling. S(+) ketoprofen clearance scaled by bioavailability (CL/F) was 0.114 L/kg/h (elimination half‐life = 1.62 h). For robenacoxib, blood CL/F was 0.684 L/kg/h (elimination half‐life = 1.13 h). Exudate elimination half‐lives were 25.9 and 41.5 h for S(+) ketoprofen and robenacoxib, respectively. Both drugs reduced exudate PGE2 concentration significantly between 6 and 36 h. Ketoprofen significantly suppressed (>97%) serum TxB2 between 4 min and 24 h, whereas suppression was mild and transient with robenacoxib. In vivoIC50COX‐1/IC50COX‐2 ratios were 66.9:1 for robenacoxib and 1:107 for S(+) ketoprofen. The carboxylic acid nature of both drugs may contribute to the prolonged COX‐2 inhibition in exudate, despite short half‐lives in blood. 相似文献
35.
36.
Chris Langdon Ford Evans Dave Jacobson Michael Blouin 《Aquaculture (Amsterdam, Netherlands)》2003,220(1-4):227-244
Parental families (G0) in three lines of Pacific oysters were selected based on live weight and meat yields at harvest. The average live weight yield of progeny (G1) from crossing G0-selected lines in seven trials was 9.5% greater than that of nonselected control families and live weight yields were significantly greater (ANOVA, P<0.001) in four out of seven trials. The response to selection was greater if G1 families were tested at the same site as their parents' selection site rather than at a different site, although this effect was only significant for G1 families of cohort 5 (P<0.01) but not cohort 7 (P>0.05). A significant genotype×environment interaction affected yields in both cohort 5 and cohort 7 (ANOVA; P<0.001). In addition, correlation between the yields of the same families planted at both intertidal and subtidal sites was positive but weak (cohort 5, r=0.30; cohort 7, r=0.35), indicating that selection for high yield in one environment would likely result in a low correlated response in a different environment. Nonetheless, it was possible to identify six families in cohort 5 and four families in cohort 7 that were among the top 10 families at both sites. Further evaluation of families across a wider range of environments is needed to determine if it is possible to substantially improve yields by selecting “generalist” families that perform well along the whole Pacific coast, or whether it will be necessary to select lines that are suited to particular sites. 相似文献
37.
1. The impact of land-claim on the intertidal areas of the Forth estuary, eastern Scotland is described. It is shown that in recent times almost 50% of the intertidal area has been destroyed for a variety of purposes, including agriculture, harbours and industrial development. 2. The loss of infaunal invertebrate biomass and production from the intertidal habitat has been calculated for each part of the estuary, and by summation for the whole estuary. The loss is discussed in relation to the total biomass and production, both intertidally and subtidally, of the estuary. It is shown that proportionately more biomass and production may have been lost than area. 3. The impact of land-claim on estuarine fish is calculated. Land-claim has removed 24% of the natural fish habitats in the Forth estuary, and thereby removed 40% of their food supply. 4. The impact of habitat loss on birds was observed for one area where observations continued throughout a period of land-claim. For individual bird species at Torry Bay, land-claim had consequences ranging from neutral to substantially negative. Significant declines were found for overwintering populations of dunlin and bar-tailed godwit. Comparisons of pre- and post-land-claim bird feeding usage of this area, showed that the impact of land-claim on local bird populations differed between species. The large scale loss of habitat on the Forth seems likely to have reduced the size of some shorebird populations which overwinter on the estuary. 5. It is concluded that when considering the impact of land-claim on estuaries that, as found in some previous studies, a simple consideration of area lost may be inadequate to describe the effects of land-claim, and the consequences for animals living within the estuary may differ considerably amongst themselves and from area to area. 相似文献
38.
39.
Surrogate Correlations and Near-Infrared Diffuse Reflectance Sensing of Trace Metal Content in Soils 总被引:1,自引:0,他引:1
Chun-Yu Wu Astrid R. Jacobson Magdeline Laba Bojeong Kim Philippe C. Baveye 《Water, air, and soil pollution》2010,209(1-4):377-390
Near-infrared diffuse reflectance sensing (NIRS) of soils has been the object of considerable interest and research in the last few years. This has been motivated by the prospect that this method seems to provide a cheap, convenient alternative to conventional, time-consuming methods for the measurement of a wide range of soil parameters. In particular, various authors have advocated that NIRS could be used to measure rapidly and non-destructively the concentration of trace metals in surface soils. Correlation analyses between NIRS spectra and trace metal concentration have yielded inconclusive results to date, suggesting that trace metal concentration may belong to a class of “tertiary” soil parameters, linked to NIRS spectra through “surrogate”, or indirect, correlations, involving some other primary or secondary parameter like clay or organic matter content, to which NIRS spectra are very sensitive. To assess the validity of this surrogate correlation hypothesis in the case of trace metals, experiments were carried out with soil samples varying only in the amount of trace metals they contain. Field-aged Hudson and Arkport soil pots spiked with Cu and Zn, freshly spiked samples of the same soils, and samples of a metalliferous peat soil from Western New York naturally rich in Cd and Zn were subjected to NIRS under laboratory conditions. Detailed analysis indicates that the NIR spectrum is sensitive to sample handling, including the orientation of the samples in the NIRS instrument, but that, at the same time, there is no discernable effect of the presence of trace metals on any part of the NIR spectrum. These results provide strong experimental support to the hypothesis of “surrogate” correlation for trace metals, and indicate that trace metals, even in severely contaminated soils, should not interfere with the NIR sensing of primary or secondary parameters, like organic matter content. Further work is needed to determine if this feature of NIR spectra extends to other soil chemical parameters. 相似文献
40.