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   5894篇
  免费   499篇
  国内免费   3篇
  6396篇
  2023年   40篇
  2022年   55篇
  2021年   112篇
  2020年   100篇
  2019年   127篇
  2018年   142篇
  2017年   100篇
  2016年   154篇
  2015年   241篇
  2014年   254篇
  2013年   343篇
  2012年   414篇
  2011年   382篇
  2010年   315篇
  2009年   247篇
  2008年   357篇
  2007年   333篇
  2006年   302篇
  2005年   324篇
  2004年   253篇
  2003年   234篇
  2002年   255篇
  2001年   103篇
  2000年   75篇
  1999年   72篇
  1998年   96篇
  1997年   54篇
  1996年   89篇
  1995年   66篇
  1994年   50篇
  1993年   55篇
  1992年   49篇
  1991年   44篇
  1990年   29篇
  1989年   35篇
  1988年   31篇
  1987年   33篇
  1986年   23篇
  1985年   39篇
  1984年   35篇
  1983年   25篇
  1982年   29篇
  1981年   21篇
  1980年   29篇
  1979年   18篇
  1978年   16篇
  1977年   20篇
  1976年   23篇
  1974年   19篇
  1973年   21篇
排序方式: 共有6396条查询结果,搜索用时 15 毫秒
71.
Soil legacy effects are commonly highlighted as drivers of plant community dynamics and species co‐existence. However, experimental evidence for soil legacy effects of conditioning plant communities on responding plant communities under natural conditions is lacking. We conditioned 192 grassland plots using six different plant communities with different ratios of grasses and forbs and for different durations. Soil microbial legacies were evident for soil fungi, but not for soil bacteria, while soil abiotic parameters did not significantly change in response to conditioning. The soil legacies affected the composition of the succeeding vegetation. Plant communities with different ratios of grasses and forbs left soil legacies that negatively affected succeeding plants of the same functional type. We conclude that fungal‐mediated soil legacy effects play a significant role in vegetation assembly of natural plant communities.  相似文献   
72.
73.
74.
75.
Most rabies vaccines are based on inactivated virus, which production process demands a high level of biosafety structures. In the past decades, recombinant rabies virus glycoprotein (RVGP) produced in several expression systems has been extensively studied to be used as an alternative vaccine. The immunogenic characteristics of this protein depend on its correct conformation, which is present only after the correct post-translational modifications, typically performed by animal cells. The main challenge of using this protein as a vaccine candidate is to keep its trimeric conformation after the purification process. We describe here a new immunoaffinity chromatography method using a monoclonal antibody for RVGP Site II for purification of recombinant rabies virus glycoprotein expressed on the membrane of Drosophila melanogaster S2 cells. RVGP recovery achieved at least 93%, and characterization analysis showed that the main antigenic proprieties were preserved after purification.  相似文献   
76.
77.
The extinction debt, delayed species extinctions following landscape degradation, is a widely discussed concept. But a consensus about the prevalence of extinctions debts is hindered by a multiplicity of methods and a lack of comparisons among habitats. We applied three contrasting species–area relationship methods to test for plant community extinction debts in three habitats which had different degradation histories over the last century: calcareous grassland, heathland and woodland. These methods differ in their data requirements, with the first two using information on past and current habitat area alongside current species richness, whilst the last method also requires data on past species richness. The most data‐intensive, and hence arguably most reliable method, identified extinction debts across all habitats for specialist species, whilst the other methods did not. All methods detected an extinction debt in calcareous grassland, which had undergone the most severe degradation. We conclude that some methods failed to detect an extinction debt, particularly in habitats that have undergone moderate degradation. Data on past species numbers are required for the most reliable method; as such data are rare, extinction debts may be under‐reported.  相似文献   
78.
79.
80.
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