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   161291篇
  免费   6831篇
  国内免费   8055篇
林业   15851篇
农学   15255篇
基础科学   7296篇
  22386篇
综合类   36023篇
农作物   8474篇
水产渔业   7458篇
畜牧兽医   48641篇
园艺   4036篇
植物保护   10757篇
  2022年   1958篇
  2021年   2962篇
  2020年   2878篇
  2019年   2853篇
  2018年   4909篇
  2017年   5614篇
  2016年   4227篇
  2015年   3916篇
  2014年   3858篇
  2013年   6235篇
  2012年   6626篇
  2011年   8706篇
  2010年   7714篇
  2009年   6655篇
  2008年   7318篇
  2007年   7644篇
  2006年   5915篇
  2005年   5476篇
  2004年   3531篇
  2003年   3429篇
  2002年   2878篇
  2001年   3517篇
  2000年   3809篇
  1999年   3692篇
  1998年   2583篇
  1997年   2270篇
  1996年   2016篇
  1995年   2166篇
  1994年   1824篇
  1993年   1826篇
  1992年   2439篇
  1991年   2339篇
  1990年   2337篇
  1989年   2225篇
  1988年   1975篇
  1987年   1743篇
  1986年   1690篇
  1985年   1592篇
  1984年   1319篇
  1983年   1209篇
  1979年   1265篇
  1978年   988篇
  1975年   914篇
  1974年   1201篇
  1973年   1242篇
  1972年   1256篇
  1971年   1183篇
  1970年   1103篇
  1969年   1007篇
  1967年   908篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
A 2-year-old female Japanese domestic cat weighing 3.6 kg was presented due to marked abdominal distention and was diagnosed as hepatic cyst. The bile acid concentration of the hepatic cyst was as low as the serum bile acid concentration. The membrane of the cysts was excised from the edge of the compressed hepatic tissue and no other surgical manipulation was performed. This surgical procedure is simple and quick compared to hepatic lobectomy, however, it is necessary to evaluate the fluid of the cyst before performing this procedure.  相似文献   
75.
本试验是在PDA培养丛中,添加不同浓度的高美施微肥,通过两个供试菌株的对比试验,选出了适宜各菌抹的最佳高美施生长浓度,结果,不同苗株在不同浓反的高美施培养基中的在现不一致。因此.在制种工作中,要根据平菇不同品种的特征特性来确定其最佳生长的营养条件。高美施在平菇母种制种技术上的应用在国内属首次报道。  相似文献   
76.
A field experiment was conducted during the winter seasons of 1992–93 and 1993–94 at Anand to study the effect of FYM, nitrogen and source of fertilizer on growth and yield of mustard [ Brassica juncea (L.) Czernj & Cosson]. The results showed significant variation in leaf area index (LAI), crop growth rate (CGR), dry matter production and seed yield. The direct effect of farmyard manure (FYM) was conspicuous in improving the growth of mustard. FYM application at 10 tonnes ha−1 significantly increased the LAI, CGR and dry matter accumulation per plant at almost all the stages during first year study (1992–93) and in pooled analysis. Similarly, nitrogen application registered maximum LAI, CGR at 75 kg level and RGR and NAR at 50 kg level at almost all the during both years. Sulphur carrying source (Ammonium sulphate plus single super phosphate) increased all stages growth characters. Maximum dry matter accumulation per plant and seed yield were recorded with highest levels of FYM (20 tonnes ha−1), N (75 kg ha−1) and source having S. Seed yield was strongly associated with LAI and dry matter accumulation per plant at all the stages.  相似文献   
77.
78.
The determination of differentiation and transplantation antigens will be of growing importance in immune diagnosis for individual animals as well as for breeding purposes in populations. Differentiation antigens characterize subsets of cell populations and indicate their functional capacity while transplantation antigens represent markers of individuals of a species. Occurrence and significance of these antigenic systems are briefly reviewed.  相似文献   
79.
80.
Serum antibody (virus neutralisation, complement fixation, IgM and IgG) responses to equine herpesvirus-1 (EHV-1) infection were measured in six foals which were initially free from EHV-1 and EHV-4 infection and maternally-derived antibodies. Following primary infection, high titres of virus neutralisation and complement fixation antibodies were detectable against EHV-1, however, corresponding antibody levels against EHV-4 were low or inapparent, although the two viruses share a number of cross-reactive epitopes. In addition, following the primary infection with EHV-1, IgM levels increased before those of IgG, virus neutralisation and complement fixation antibodies, peaked sooner and thereafter declined. Stimulation of IgM levels was observed on secondary infection with EHV-1 given 61 days later. In contrast, IgG, virus neutralisation and complement fixation antibodies following primary infection were more sustained and no increase in their levels was observed on secondary infection. No consistent changes in IgM or IgG levels were seen after administration of dexamethasone to reactivate latent virus.  相似文献   
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