首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8890篇
  免费   572篇
  国内免费   50篇
林业   546篇
农学   449篇
基础科学   79篇
  1561篇
综合类   627篇
农作物   452篇
水产渔业   675篇
畜牧兽医   4189篇
园艺   132篇
植物保护   802篇
  2023年   82篇
  2022年   145篇
  2021年   265篇
  2020年   261篇
  2019年   325篇
  2018年   294篇
  2017年   320篇
  2016年   339篇
  2015年   233篇
  2014年   334篇
  2013年   522篇
  2012年   511篇
  2011年   549篇
  2010年   282篇
  2009年   310篇
  2008年   431篇
  2007年   433篇
  2006年   387篇
  2005年   370篇
  2004年   338篇
  2003年   300篇
  2002年   340篇
  2001年   246篇
  2000年   245篇
  1999年   208篇
  1998年   66篇
  1997年   62篇
  1996年   58篇
  1995年   58篇
  1994年   38篇
  1993年   45篇
  1992年   81篇
  1991年   57篇
  1990年   65篇
  1989年   66篇
  1988年   63篇
  1987年   51篇
  1986年   46篇
  1985年   58篇
  1984年   38篇
  1983年   43篇
  1982年   30篇
  1980年   24篇
  1979年   37篇
  1978年   21篇
  1977年   21篇
  1974年   23篇
  1973年   25篇
  1972年   24篇
  1970年   26篇
排序方式: 共有9512条查询结果,搜索用时 15 毫秒
41.
42.
Conjugated linoleic acids (CLA), 9-cis:11-trans and 10-trans:12-cis, have been shown to be able to modify some immune cells parameters and plasma lipids in a variety of experiment models. Since lymphocytes and polymorphonuclear cells (PMNC) have a large spectrum functions in the immune response, the knowledge in this field has to be expanded. Beagle dogs were fed a control diet or a CLA supplemented diet for nine months. Blood was collected for biochemical analysis and lymphocyte and PMNC isolation. PMNC were assayed for lysosome content, phagocytic activity and superoxide anion production. A lymphocyte proliferation capacity assay was done. The CLA fed dogs had a 34% reduction in total cholesterol (P < 0.05), 28% in LDL (P < 0.05) and 28% non-HDL-cholesterol (P < 0.05). Neither of the PMNC parameters evaluated demonstrated significant alteration. Lymphocytes from CLA group increased by 45% their mitotic capacity (P < 0.05). Our study demonstrates that CLA can successfully modify the lipid profile of dogs (monogastrics) when fed at reasonable levels, but did not significantly alter inflammatory function as would generally predicted. Further, we had some indication that CLA modulated T cell responsiveness.  相似文献   
43.
This article serves as a quick reference for metabolic alkalosis. Guidelines for analysis and causes, signs, and a stepwise approach are presented.  相似文献   
44.
Between 1995 and 1997 a neurological condition in pheasant poults from 24 sites in England and Scotland was investigated. Affected birds showed varying degrees of ataxia and incoordinated movements and, in severe cases, recumbency, but generally remained alert with their heads held upright. The condition characteristically affected poults from seven weeks of age and the incidence on any one site was low. No significant bacteria were isolated consistently from brain tissue. The condition was characterised histologically by a non-suppurative meningoencephalitis, in which lesions were found predominantly in the cerebellum in 61 of 81 samples examined (75.3 per cent). A non-suppurative myelitis was recorded in 16 of 20 spinal cords examined. No lesions were recorded in peripheral neural tissue and lesions were rare in other tissues. The condition appeared not to have been recorded previously in pheasants. A viral aetiology was suspected but Newcastle disease virus was not involved.  相似文献   
45.
46.
A recent survey reported an increased risk of injury in dogs participating in agility, a competitive canine sport involving different jumping activities. The aim of this study was to quantify the kinetic parameters during jump landing for commonly used obstacle types. It was hypothesised that with increasing obstacle height, the vertical force and vertical and accelerative horizontal impulse will increase as a result of a lengthened aerial phase, a more acute landing angle and the need to convert potential into forwards kinetic energy. Simultaneous kinetic and kinematic data were recorded from 11 competition agility dogs jumping over obstacle combinations of different height and inter-obstacle distance. Speed and landing angle of the second of the two consecutive jumps were successfully controlled by obstacle height and distance between obstacles. Statistical analysis showed differences between obstacles for peak vertical force, vertical impulse and accelerative horizontal impulse (increasing values with more acute landing angles). Extremely high peak vertical force was observed in the forelimbs (4.5 times bodyweight) when landing from a hurdle jump at high speed. Further detailed studies into the consequences for internal limb structures are warranted in order to clarify how this might be related to injury.  相似文献   
47.
48.
49.
50.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号