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   101202篇
  免费   738篇
  国内免费   905篇
  102845篇
  2023年   78篇
  2022年   127篇
  2021年   261篇
  2020年   151篇
  2019年   170篇
  2018年   11993篇
  2017年   10788篇
  2016年   7663篇
  2015年   938篇
  2014年   681篇
  2013年   851篇
  2012年   4753篇
  2011年   13298篇
  2010年   12277篇
  2009年   8462篇
  2008年   10129篇
  2007年   11652篇
  2006年   582篇
  2005年   834篇
  2004年   1226篇
  2003年   1232篇
  2002年   1001篇
  2001年   455篇
  2000年   336篇
  1999年   187篇
  1998年   67篇
  1997年   77篇
  1996年   74篇
  1995年   52篇
  1994年   65篇
  1993年   66篇
  1992年   137篇
  1991年   154篇
  1990年   95篇
  1989年   102篇
  1988年   105篇
  1987年   103篇
  1986年   87篇
  1985年   92篇
  1984年   89篇
  1983年   67篇
  1982年   50篇
  1980年   49篇
  1979年   78篇
  1978年   58篇
  1977年   49篇
  1976年   42篇
  1973年   44篇
  1972年   273篇
  1971年   304篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Journal of Plant Biochemistry and Biotechnology - Plant genomes contain a sizeable fraction, ranging from 14 to 75% of retrotransposons (class I elements), predominantly comprising LTR (Long...  相似文献   
42.

DNA replication, repair, and recombination (DRRR) are the fundamental processes required for faithful transmission of genetic information within and between generations. The DRRR genes protect the cells from potential mutations and damage during the developmental phases and stress conditions. Thus, these genes indirectly regulate diverse important agronomic traits in a crop plant. A genome-wide survey of six DRRR pathway genes, namely, DNA replication, Base Excision Repair, Nucleotide Excision Repair, Homologous Recombination, Mismatch Excision Repair, and Non-Homologous End-Joining, identified 157 DRRR genes in chickpea. Phylogenetic analysis of these genes within the legume clades and model plant Arabidopsis identified 42 conserved DRRR genes exhibiting clade-specific evolutionary patterns. Integrating the gene-based association mapping with differential expression profiling identified the natural alleles of the potential DRRR genes, primarily regulating flowering and maturation time and involved in drought tolerance of chickpea. Identifying and understanding DRRR genes’ roles in regulating yield and stress tolerance traits in a vital grain legume like chickpea is requisite for its future crop improvement endeavors. Manipulation of promising functionally relevant DRRR genes will pave the way for simultaneous improvement in multiple beneficial agronomic traits in chickpea.

  相似文献   
43.
44.
Ethics are a set of moral principles and values a civilized society follows. Doing science with principles of ethics is the bedrock of scientific activity. The society trusts that the results and the projected outcome of any scientific activity is based on an honest and conscientious attempt by the scientific community. However, during the last few decades, there has been an explosion of knowledge and the advent of digital age. We can access the publications of competitors with just a “click”. The evaluation parameters have evolved a lot and are based on impact factors, h-index and citations. There is a general feeling that the scientific community is under a lot of pressure for fulfilling the criteria for upward growth and even retention of the positions held. The noble profession of scientific research and academics has been marred by the temptation to falsify and fabricate data, plagiarism and other unethical practices. Broadly speaking, the breach of ethics involves: plagiarism, falsification of data, redundant (duplicate) publication, drawing far-fetched conclusions without hard data, for early publicity, gift authorship (receiving as well as giving), not giving sufficient attention and consideration to scholars and post-docs as per the norms, self promotion at the cost of team-members, treating colleagues (overall all juniors) in a feudal way and Machiavellianism (cunningness and duplicity in general conduct and push to positions of power and pelf). Misconduct in Indian academics and science is also under a lot of focus. It is important and urgent that science, engineering, and health departments and institutions in our country have in place systems for education and training in pursuit of science with ethics by sound and professional courses in Responsible Conduct of Research. All research and academic institution must have the Office of Ethics for information, guidelines, training and professional oversight of conduct of research with the ethos and ethics of research.  相似文献   
45.
46.
47.
48.
49.
Recent technological advances in Global Positioning System (GPS) telemetry have allowed the production of lightweight devices suitable for use on small mammals. We evaluated the use of GPS bugs on the European hedgehog (Erinaceus europaeus) in a series of static and field tests. Static tests were conducted in five different rural habitats, affording different degrees of obstruction to satellites. GPS bug performance was good in all habitats (fix success rate (FSR): median ≥?66.8 %; location error (LE): mean ≤?13.5 m), except woodland (FSR?=?37.7 %; LE?=?15.6 m), with performance highest in the open pasture habitat (FSR?=?100 %; LE?=?6.4 m). Field tests revealed mean FSR was high (84.6 %), with the use of nesting habitats, the probable cause of most failed fixes. Despite being more expensive, GPS bugs require less survey effort and substantially lower labour costs with unlimited longevity permitting re-use in multiple seasons. We recommend the use of GPS bugs in the spatial ecological study of any small mammal in a rural environment, providing accurate and unbiased movement data. Further performance testing is recommended before deployment on species inhabiting forested habitats where reduced FSR and high LE support the alternative use of very high frequency tracking.  相似文献   
50.
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