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   103435篇
  免费   5623篇
  国内免费   69篇
林业   4760篇
农学   3191篇
基础科学   493篇
  11604篇
综合类   19013篇
农作物   3786篇
水产渔业   4710篇
畜牧兽医   53984篇
园艺   1210篇
植物保护   6376篇
  2018年   1449篇
  2017年   1537篇
  2016年   1353篇
  2015年   1283篇
  2014年   1492篇
  2013年   4039篇
  2012年   2875篇
  2011年   3384篇
  2010年   2149篇
  2009年   2208篇
  2008年   3248篇
  2007年   3212篇
  2006年   3012篇
  2005年   2787篇
  2004年   2639篇
  2003年   2647篇
  2002年   2540篇
  2001年   3060篇
  2000年   3014篇
  1999年   2468篇
  1998年   1018篇
  1997年   1022篇
  1996年   957篇
  1995年   1082篇
  1994年   1003篇
  1993年   990篇
  1992年   1993篇
  1991年   2136篇
  1990年   2024篇
  1989年   2019篇
  1988年   1887篇
  1987年   1894篇
  1986年   1950篇
  1985年   1917篇
  1984年   1584篇
  1983年   1452篇
  1982年   954篇
  1979年   1442篇
  1978年   1174篇
  1977年   1094篇
  1976年   1107篇
  1975年   1132篇
  1974年   1436篇
  1973年   1353篇
  1972年   1402篇
  1971年   1298篇
  1970年   1286篇
  1969年   1245篇
  1968年   1044篇
  1967年   1104篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
141.
142.
143.
144.
Fifty six 1,2,3-benzothiadiazoles and related compounds were evaluated as carbaryl synergists against the house fly (Musca domestica). Many of these were excellent synergists, the most active being those containing various combinations of halogen, alkyl, or alkoxy substituents in the 5- and/or 6-positions of the ring.Regression analysis on the data from 14 compounds for which substituents constants were available established that synergistic activity can be satisfactorily described by equations in terms of the hydrophobic bonding constant (π) and the homolytic free radical constant (σ ·).The results with compounds related to the 1,2,3-benzothiadiazoles suggest that synergistic activity is associated primarily with the diazosulfide moiety.  相似文献   
145.
146.
147.
148.
'Meleira', or 'sticky disease', is currently the most damaging papaya disease in the mid-eastern Brazilian growing regions. Consistent disease transmission via latex injection, presence of similar isometric particles in the laticiferous vessels of diseased plants, and detection of double-stranded DNA in naturally and experimentally infected papaya trees suggest that a virus is the causal agent. Conclusive evidence for viral aetiology was previously lacking, mostly because every attempt to purify the putative virus from infected papayas had failed. Following the successful purification and partial characterization of the meleira virus, healthy papaya seedlings injected with purified virus particles later developed typical symptoms of the disease. Negatively stained, isometric, full and 'empty' purified virus particles measured 42 and 38 nm, respectively. The viral genome was a single dsRNA molecule of about 12 kbp. Several capsid proteins, ranging in size from 14·4 to 45 kDa, were consistently revealed by PAGE. Papaya meleira virus (PMeV) appears to represent a novel group of viruses, with no known similar counterpart among known plant-, vertebrate-, invertebrate- or prokaryote-infecting viruses.  相似文献   
149.
Journal of Plant Diseases and Protection - Effect of GCSC-BtA (Germany-China Scientific Cooperation — Bacillus thuringiensis — Abamectin) biocide on abundance and diversity of some...  相似文献   
150.
Plum pox potyvirus (PPV) induces in infected Nicotiana clevelandii cells characteristic crystalline inclusions known as nuclear inclusions (NI) when located in the nucleus and as dense material (Dm) when located in the cytoplasm. Crystalline inclusions contain protease (NIa) and RNA-dependent RNA polymerase (NIb) proteins. It is now well established for all potyviruses that cylindrical inclusions contain CI helicase ATPase protein (Martin et al., 1992). The intracellular location of other non-structural PPV proteins remains unknown. Using Escherichia coli expression vectors, specific antibodies were obtained against P1, P3, 6K2 and NIb PPV proteins for which antibodies were not yet available. As expected, NIb antiserum labelled crystalline inclusions. P1, P3 and 6K2 proteins were present in both types of crystalline inclusions found in the nucleus and in the cytoplasm of PPV-infected leaves of N. clevelandii, suggesting that nuclear inclusions and dense material were composed of the same proteins. This composition is discussed.  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