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   50934篇
  免费   2789篇
  国内免费   33篇
林业   2621篇
农学   1538篇
基础科学   220篇
  5747篇
综合类   10156篇
农作物   1956篇
水产渔业   2355篇
畜牧兽医   25471篇
园艺   560篇
植物保护   3132篇
  2019年   450篇
  2018年   737篇
  2017年   790篇
  2016年   688篇
  2015年   640篇
  2014年   772篇
  2013年   1760篇
  2012年   1488篇
  2011年   1668篇
  2010年   1079篇
  2009年   1161篇
  2008年   1635篇
  2007年   1649篇
  2006年   1537篇
  2005年   1466篇
  2004年   1378篇
  2003年   1345篇
  2002年   1281篇
  2001年   1529篇
  2000年   1485篇
  1999年   1218篇
  1998年   456篇
  1997年   474篇
  1996年   470篇
  1995年   523篇
  1994年   470篇
  1993年   483篇
  1992年   926篇
  1991年   921篇
  1990年   911篇
  1989年   919篇
  1988年   869篇
  1987年   902篇
  1986年   890篇
  1985年   897篇
  1984年   723篇
  1983年   652篇
  1979年   647篇
  1978年   540篇
  1977年   459篇
  1976年   463篇
  1975年   503篇
  1974年   691篇
  1973年   605篇
  1972年   675篇
  1971年   673篇
  1970年   598篇
  1969年   591篇
  1968年   451篇
  1967年   511篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
201.
202.
203.
A case of selenium poisoning was suspected following the administration of 325 micromol selenium a day as sodium selenate (25 mg Se) for five consecutive days. The main signs were confined to changes in the integument which were loss of hair from the mane and tail, disintegration of the skin of the anus, lips, prepuce and scrotum, and separation of the hooves from the coronary corium. Periodic analyses of blood, hair and hoof parings from the sole correlated strongly with blood and identified horn and hair as important additional routes of excretion.  相似文献   
204.
The computer-assisted, kinetics-based enzyme-linked immunosorbent assay for coronavirus antibodies in cats was calibrated to the conventional indirect immunofluorescence assay by linear regression analysis and computerized interpolation (generation of "immunofluorescence assay-equivalent" titers). Procedures were developed for normalization and standardization of kinetics-based enzyme-linked immunosorbent assay results through incorporation of five different control sera of predetermined ("expected") titer in daily runs. When used with such sera and with computer assistance, the kinetics-based enzyme-linked immunosorbent assay minimized both within-run and between-run variability while allowing also for efficient data reduction and statistical analysis and reporting of results.  相似文献   
205.
Experimentally-induced cases of sweating sickness in calves were used in an effort to correlate the blood chemistry with some of the known pathological changes. Results showed that the "sweating" associated with necrotic dermatitis did not alter blood electrolyte levels. Laboratory evidence of a disseminated intravascular coagulopathy was found which correlated with the microthrombi described in cases of sweating sickness. A high blood cortisol level was found in one of the animals that died from the disease and could possibly be used as a prognostic indicator in clinical cases. Recommendations are made with regard to the supportive treatment based on the clinical pathological findings.  相似文献   
206.
207.
Globally coherent oscillation modes were discovered in the sun about a decade ago, providing a unique seismological probe of the solar interior. Current observations detect modes that are phase-coherent for up to 1 year, with surface velocity amplitudes as low as 2 millimeters per second, and thousands of mode frequencies have been measured to accuracies as high as 1 part in 10(5). This article discusses the properties of these oscillation modes and the ways in which they are adding to our understanding of the structure and dynamics of the sun.  相似文献   
208.
209.
210.
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