全文获取类型
收费全文 | 2576篇 |
免费 | 126篇 |
国内免费 | 3篇 |
专业分类
林业 | 137篇 |
农学 | 59篇 |
基础科学 | 19篇 |
355篇 | |
综合类 | 378篇 |
农作物 | 66篇 |
水产渔业 | 245篇 |
畜牧兽医 | 1247篇 |
园艺 | 54篇 |
植物保护 | 145篇 |
出版年
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 46篇 |
2019年 | 58篇 |
2018年 | 52篇 |
2017年 | 45篇 |
2016年 | 53篇 |
2015年 | 39篇 |
2014年 | 44篇 |
2013年 | 104篇 |
2012年 | 127篇 |
2011年 | 139篇 |
2010年 | 77篇 |
2009年 | 86篇 |
2008年 | 160篇 |
2007年 | 140篇 |
2006年 | 137篇 |
2005年 | 103篇 |
2004年 | 125篇 |
2003年 | 113篇 |
2002年 | 129篇 |
2001年 | 40篇 |
2000年 | 53篇 |
1999年 | 55篇 |
1998年 | 27篇 |
1997年 | 30篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1993年 | 16篇 |
1992年 | 29篇 |
1991年 | 32篇 |
1990年 | 45篇 |
1989年 | 21篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 21篇 |
1977年 | 14篇 |
1975年 | 19篇 |
1973年 | 16篇 |
1972年 | 15篇 |
1971年 | 12篇 |
1970年 | 18篇 |
排序方式: 共有2705条查询结果,搜索用时 8 毫秒
1.
2.
M L van der Leek J B Dame C L Adams K D Gillis R C Littell 《American journal of veterinary research》1992,53(6):877-882
Experimental and field trials were conducted to evaluate an ELISA for its ability to detect Trichinella-infected domestic swine and to compare ELISA results with muscle-digestion test results. The ELISA used was a commercial double-antibody kit, containing an excretory-secretory antigen, and was evaluated principally for epidemiologic use. Experimentally induced infection in swine (4 groups of 3 pigs each; inoculated with 0, 50, 500 or 5,000 larvae) was detected as early as postinoculation week 4, with seroconversion of all inoculated swine by postinoculation week 8. The rate of seroconversion appeared to be affected by initial larval dose, time after inoculation, and immunocompetence of the individual host. Determination of antibody kinetics generally revealed rapidly increasing antibody titer, followed by its steady decrease in most pigs. Once seropositive, however, all pigs remained seropositive for the duration of the 10-week study. Presence of muscle larvae was confirmed in all infected pigs at termination of the study. We recognize that the experimental conditions may not be truly representative of those under which natural infection develops in pigs; however, the ELISA detected an infected pig with muscle larval density of 0.87 larvae/g of tissue. Results of a field trial (n = 310) indicated no muscle digestion test-positive pigs (35 g of diaphragm muscle digested/pig), but 3 samples tested positive by ELISA for specificity of 99.0%. 相似文献
3.
4.
5.
The in vitro metabolism of the chiral isomers of fonofos and fonofos oxon in the presence of mouse liver mixed-function oxidase and serum esterase was investigated. The metabolism of 35S-labeled phenyl-(S)P-fonofos mediated by mixed-function oxidase took place stereoselectively, resulting predominantly in (R)P-fonofos oxon. Similarly, (R)P-fonofos was converted to (S)P-oxon. In each case, however, a significant amount of racemization occurred. Other products were diphenyl disulfide and diphenyl disulfide oxide. In addition to stereospecificity, the oxidative metabolism of (R)P-fonofos proceeded at a rate faster than that of (S)P-fonofos. Stereoselective rate differences also were observed in mouse or rat serum-catalzyed degradation of the fonofos oxon enantiomers, the (S)P isomer being degraded about twofold faster than its enantiomer. The differences in toxicities of the isomers of fonofos and fonofos oxon were consistent with the in vitro metabolism data. 相似文献
6.
7.
The official final action acid hydrolysis method, 14.019, for the determination of fat in foods was successfully applied, with slight modifications, to the analysis of homogenates of food, feces, and animal tissues as well as dry samples of mixed foods. In samples containing sucrose or fructose, it was necessary to carry out a fermentation procedure before acid hydrolysis to avoid problems encountered when these sugars were present. 相似文献
8.
Genetic resistance to race alpha of C. lindemuthianum in the nine varieties of beans studied can be accounted for by dominant alleles at either of two loci, which are unlinked and which behave as duplicate factor loci in the classical sense. A similar system of loci governs reaction to races beta and gamma, with evidence favoring multiple allelism and dominance of alleles conferring susceptibility in certain instances in the case of beta. In addition, for reaction to races beta and gamma, there are distinct systems of complementary factors, again with multiple allelism at the beta loci. Finally, there is genetic linkage between genes of the duplicate factor set governing reaction to gamma and genes of the duplicate factor set, and complementary factor set conditioning reaction to beta. The genes that are members of the set(s) pertaining to any one race alone are independent of each other in a linkage sense.Paper based on work conducted by the senior author in partial fulfilment of requirements for the Doctor of Philosophy degree at Michigan State University and supported by the Rockefeller Foundation.Formerly Rockefeller Foundation Student in Crop Science, now Director, Instituto Nacional de Investigaciones Agricolas, Veracruz, Mexico; Professor of Crop Science, Michigan State University; and Research Pathologist, Crops Research Division, Agricultural Research Service, USDA. 相似文献
9.
10.