全文获取类型
收费全文 | 402篇 |
免费 | 23篇 |
专业分类
林业 | 13篇 |
农学 | 9篇 |
基础科学 | 4篇 |
42篇 | |
综合类 | 46篇 |
农作物 | 24篇 |
水产渔业 | 13篇 |
畜牧兽医 | 231篇 |
园艺 | 12篇 |
植物保护 | 31篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1968年 | 5篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1902年 | 1篇 |
1896年 | 1篇 |
排序方式: 共有425条查询结果,搜索用时 0 毫秒
411.
412.
N S Matthews S M Miller S M Hartsfield M R Slater 《Journal of the American Veterinary Medical Association》1992,201(4):559-563
Recovery from isoflurane anesthesia was shorter, with no difference in quality, compared with halothane anesthesia in 2 groups of horses. In 1 group, 12 horses scheduled for elective arthroscopy were randomly assigned to receive halothane or isoflurane for maintenance of anesthesia during surgery. In the other group, 6 horses received anesthesia only, on 2 occasions, with halothane on 1 occasion, and isoflurane on the other. Difference in the quality of recovery was not seen between isoflurane and halothane anesthesia in either group. In the group that had surgery, recovery to sternal position was significantly shorter when isoflurane was used. In the group not treated surgically, recovery to sternal and standing positions was significantly shorter with isoflurane. 相似文献
413.
414.
The economics of agroforestry systems can be approached in a purely analytical fashion with mathematical equations and diagrams explaining the principles of analysis. This paper argues that such an approach may be useful for teaching purposes but has little practical relevance. There is an urgent need for a practical tool with which multi-disciplinary teams can asses agroforestry systems. The simplest and most common approaches to the economic analysis of farm management problems are various forms of budgeting. Recent advances in micro-computer technology provide the means by which the principles of partial budgeting can be adapted to the needs of agroforestry taking account of its multiple component nature, seasonal variability and long life span. The paper sets out the specifications for such an approach and indicates how it might be used. 相似文献
415.
416.
Fisher AD Knight TW Cosgrove GP Death AF Anderson CB Duganzich DM Matthews LR 《Australian veterinary journal》2001,79(4):279-284
OBJECTIVE: To compare the effects of surgical and latex banding methods of castration in 14- and 9-month-old bulls. DESIGN: Two randomised, controlled experiments. PROCEDURE: In Experiment 1, following administration of local anaesthetic, 14-month-old bulls were castrated by either surgical or banding methods, or left entire. Behavioural, plasma cortisol, plasma haptoglobin and bodyweight responses were recorded. A group of steers from the same mob was used as an additional comparison for bodyweight data. In Experiment 2, following administration of local anaesthetic, 9-month-old bulls were castrated by either surgical or banding methods and cortisol, haptoglobin and bodyweight responses were recorded. Entire bulls from the same group were used as an additional comparison for bodyweight data. RESULTS: In Experiment 1, surgical castrates exhibited more leg stamping and tail swishing than banded or entire animals in the hours after castration. Surgical castrates in both experiments also showed an increase in plasma haptoglobin, which resolved after 4 days. Plasma cortisol was generally not affected by castration. Surgical castrates grew more slowly than entire bulls, but faster than banded animals, in the 56 days after treatment. In Experiment 1, after 56 days, the bodyweights of surgical and banded castrates were not different from the bodyweights of the steers. Fourteen-month-old banded cattle developed persistent wounds above the latex band which remained for several weeks after scrotal dehiscence, but this did not occur in the 9-month-old animals. CONCLUSION: The banding procedure produced fewer acute effects, but a greater suppression of growth than surgical castration and induced prolonged wound formation in the older age group, suggesting that this procedure may not be as suitable for yearling cattle. 相似文献
417.
HTLV-III/LAV-neutralizing antibodies to an E. coli-produced fragment of the virus envelope 总被引:87,自引:0,他引:87
S D Putney T J Matthews W G Robey D L Lynn M Robert-Guroff W T Mueller A J Langlois J Ghrayeb S R Petteway K J Weinhold 《Science (New York, N.Y.)》1986,234(4782):1392-1395
Immunization with either an Escherichia coli recombinant segment of the human T-cell lymphotropic virus (HTLV-III/LAV) envelope protein (gp 120) or with deglycosylated gp 120 envelope protein produced antibodies that neutralize HTLV-III/LAV infection in vitro. Virus neutralization titers of these antisera were equivalent to those obtained with purified native gp120 as immunogen. This localizes at least one class of neutralizing epitopes to the carboxyl-terminal half of the molecule. In addition, native gp120 prevented HTLV-III/LAV--mediated cell fusion, whereas the recombinant gp120 fragment did not. This shows that although glycosylation is not required for induction of neutralizing antibodies, it may be important for interaction with CD4, the virus receptor. A segment of the HTLV-III/LAV envelope produced in E. coli may be an important ingredient of a vaccine for acquired immune deficiency syndrome. 相似文献
418.
Control of enzyme activity by an engineered disulfide bond 总被引:19,自引:0,他引:19
A novel approach to the control of enzyme catalysis is presented in which a disulfide bond engineered into the active-site cleft of bacteriophage T4 lysozyme is capable of switching the activity on and off. Two cysteines (Thr21----Cys and Thr142----Cys) were introduced by oligonucleotide-directed mutagenesis into the active-site cleft. These cysteines spontaneously formed a disulfide bond under oxidative conditions in vitro, and the catalytic activity of the oxidized (cross-linked) T4 lysozyme was completely lost. On exposure to reducing agent, however, the disulfide bond was rapidly broken, and the reduced (non-cross-linked) lysozyme was restored to full activity. Thus an enzyme has been engineered such that redox potential can be used to control catalytic activity. 相似文献
419.
420.