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   5905篇
  免费   368篇
  国内免费   4篇
  6277篇
  2023年   28篇
  2022年   46篇
  2021年   116篇
  2020年   55篇
  2019年   73篇
  2018年   100篇
  2017年   85篇
  2016年   137篇
  2015年   244篇
  2014年   259篇
  2013年   334篇
  2012年   347篇
  2011年   357篇
  2010年   238篇
  2009年   168篇
  2008年   292篇
  2007年   273篇
  2006年   248篇
  2005年   252篇
  2004年   250篇
  2003年   222篇
  2002年   190篇
  2001年   77篇
  2000年   68篇
  1999年   77篇
  1998年   51篇
  1997年   41篇
  1996年   41篇
  1995年   62篇
  1994年   59篇
  1993年   54篇
  1992年   73篇
  1991年   78篇
  1990年   71篇
  1989年   69篇
  1988年   52篇
  1987年   53篇
  1986年   47篇
  1985年   70篇
  1984年   62篇
  1983年   47篇
  1982年   52篇
  1981年   46篇
  1980年   35篇
  1979年   41篇
  1978年   41篇
  1977年   44篇
  1975年   35篇
  1974年   34篇
  1973年   30篇
排序方式: 共有6277条查询结果,搜索用时 15 毫秒
1.
Morphological taxonomy of simple Hyphomycetes is complicated by the frequent occurrence of pleoanamorphism. In some groups of yeast-like fungi, uncommon synanamorphs are diagnostic. Differences in conidiogenesis do not always delimit natural groups. Some nomenclatural problems are mentioned, with an emphasis on the need of neotypification. Prospects are sketched for future taxonomic research.  相似文献   
2.
3.
We developed a long-term tagging method that can be used to understand species assemblages and social groupings associated with large marine fishes such as the Sand Tiger shark Carcharias taurus. We deployed internally implanted archival VEMCO Mobile Transceivers (VMTs; VEMCO Ltd. Nova Scotia, Canada) in 20 adult Sand Tigers, of which two tags were successfully recovered (10%). The recovered VMTs recorded 29,646 and 44,210 detections of telemetered animals respectively. To our knowledge, this is the first study to demonstrate a method for long-term (~ 1 year) archival acoustic transceiver tag implantation, retention, and recovery in a highly migratory marine fish. Results show low presumed mortality (n = 1, 5%), high VMT retention, and that non-lethal recovery after almost a year at liberty can be achieved for archival acoustic transceivers. This method can be applied to study the social interactions and behavioral ecology of large marine fishes.  相似文献   
4.
5.
SUMMARY: MIAH is a WWW server for the automatic alignment of new eukaryotic SSU rRNA sequences to an existing alignment of 1500 sequences. AVAILABILITY: http://chah.ucc.ie/MIAH Contact :  相似文献   
6.
7.
8.
Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters.The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed.  相似文献   
9.
10.
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