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   32857篇
  免费   2369篇
  国内免费   15篇
  35241篇
  2023年   128篇
  2022年   259篇
  2021年   561篇
  2020年   392篇
  2019年   467篇
  2018年   499篇
  2017年   514篇
  2016年   782篇
  2015年   1246篇
  2014年   1467篇
  2013年   1694篇
  2012年   2248篇
  2011年   2222篇
  2010年   1447篇
  2009年   1365篇
  2008年   1823篇
  2007年   1938篇
  2006年   1669篇
  2005年   1658篇
  2004年   1656篇
  2003年   1576篇
  2002年   1511篇
  2001年   477篇
  2000年   435篇
  1999年   420篇
  1998年   400篇
  1997年   283篇
  1996年   238篇
  1995年   246篇
  1994年   234篇
  1993年   245篇
  1992年   293篇
  1991年   264篇
  1990年   239篇
  1989年   232篇
  1988年   213篇
  1987年   216篇
  1986年   191篇
  1985年   232篇
  1984年   252篇
  1983年   185篇
  1982年   189篇
  1981年   192篇
  1980年   157篇
  1979年   146篇
  1978年   152篇
  1977年   115篇
  1976年   123篇
  1974年   153篇
  1972年   109篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Three cases of xylene poisoning occurred after prolonged inhalation of paint fumes. Analysis showed that xylene comprised more than 90% of the solvent in the paint, the total solvent comprising 34% of the paint by weight. One patient was dead on admission, while the other two recovered after at least 15 hours'' loss of consciousness. Both patients had transient liver cell damage, and one temporary impairment of renal function.  相似文献   
24.
25.
26.
27.
28.
29.
Plant hormone response mutants   总被引:4,自引:0,他引:4  
A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone-insensitive mutant phenotypes with defects in hormone-related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper-responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems.  相似文献   
30.
The excavations at Christ Church, Spitalfields (1984-86) produced a sample of 968 human skeletons which were interred between 1729 and 1859. Of these, 387 were recovered in association with coffin plates stating name, age at death, and date of death. There are 138 adult females in the named sample and the obstetric histories of 94 have been reconstructed from historical documentation. Such variables as birth spacing, number of children, and age at first and last births are known for the majority of this sample. Any individual about whose history there is any doubt has been excluded from the analysis. A middle-class group, they were largely of high nutritional status and, by the standards of the day, lived in sanitary and comfortable conditions. Both males and females have a mean age at death of 56 years. The presence or absence, the typology, the severity, the width and the length of the preauricular sulcus, the presence or absence and the number of pits on the dorsal aspect of the pubic body, sulci along the anterior sacrum adjacent to the auricular facet, and the extension of the pubic tubercle were evaluated in relation to the obstetric histories of these females. Statistical analysis has demonstrated a relationship between the presence of pubic tubercle extension and parity status and between the degree of extension and the number of children borne (P < .02). Statistically there is no significant relationship (P > .05) between either the preauricular sulcus or pubic pitting and parity status. Sacral scarring is significantly associated (P < .05) with parity status, but as it was evident in only eight females it has little practical application. Sample sizes are small, and it must be considered that statistical evaluation of larger samples might detect associations between variables not demonstrated here. There is no significant relationship between any of the cortical variants under consideration and age at death.  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