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   1324438篇
  免费   116183篇
  国内免费   1391篇
  1442012篇
  2021年   17821篇
  2020年   12626篇
  2019年   16128篇
  2018年   17546篇
  2017年   16298篇
  2016年   27950篇
  2015年   42342篇
  2014年   50386篇
  2013年   76682篇
  2012年   35507篇
  2011年   23521篇
  2010年   43090篇
  2009年   44523篇
  2008年   22489篇
  2007年   20565篇
  2006年   25902篇
  2005年   26964篇
  2004年   26075篇
  2003年   23774篇
  2002年   22096篇
  2001年   35049篇
  2000年   32403篇
  1999年   31920篇
  1998年   25249篇
  1997年   25176篇
  1996年   24758篇
  1995年   22888篇
  1994年   22720篇
  1993年   21732篇
  1992年   27624篇
  1991年   25905篇
  1990年   24346篇
  1989年   25143篇
  1988年   23055篇
  1987年   21604篇
  1986年   20410篇
  1985年   22293篇
  1984年   22152篇
  1983年   19681篇
  1982年   20170篇
  1981年   19396篇
  1980年   18062篇
  1979年   18138篇
  1978年   17210篇
  1977年   16459篇
  1976年   15657篇
  1975年   15194篇
  1974年   15387篇
  1973年   15747篇
  1972年   13395篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
961.
Methods for production of containerized seedlings ofAlnus species were developed which permit nitrogen-fixing nodules to form on the root systems prior to outplanting, in order to provide an early nitrogen input during seedling establishment. The methods are based on procedures for inoculating root systems with suspensions ofFrankia (Actinomycetales), applied either directly in the container cell as a soil drench at the time of seeding, or as a root dip for seedlings transplanted into the containers. Germination of dried, stored seed was enhanced by light and by presoaking for 16 h in water. Pretreatments to overcome seed dormancy or to eliminate fungal pathogens did not further enhance germination. Some loss of seedlings was recorded in the early stages of growth shortly after germination, which is a factor in calculating projected seedling yield. Nodulation and seedling growth were evaluated in terms of growth media characteristics. Seedlings performed well in peat-vermiculite, at soil pH between 5.5 and 8.0.  相似文献   
962.
963.
964.
Andrew C. Harper 《CMAJ》1980,123(5):400-401
  相似文献   
965.
J. E. Devitt 《CMAJ》1980,122(5):505-506
  相似文献   
966.
Rainbow trout, Salmo gairdneri , were experimentally infected with Cryptobia salmositica . The parasitaemia was associated with increases in the size of the spleen, liver and heart (% body weight). The splenomegaly was pronounced and was often 600-fold larger. The amounts of blood lactic acid and lactic dehydrogenase in the infected and control fish were similar. However, glycogen levels of the liver, heart and epaxial muscle declined. Liver glycogen levels were most affected and decreased to values which represented 20% of the control values. The pattern of the glycogen levels of the liver, heart and epaxial muscle declined to rise to normal values by day 56 post-inoculation. Thus, the glycogen levels both paralleled the acute parasitaemia and the subsequent partial recovery of the infected fish as they tolerated a low chronic parasitaemia.  相似文献   
967.
968.
969.
The cavernicolous crustacean Antromysis juberthiei showed unexpected behavior when presented with food extract : it avoids the area of odor inflow. This avoidance reaction is reduced by removal of various combinations of antennae and disappears almost with bilateral removal of the first antennae (the aesthetasc-bearing antennules).  相似文献   
970.
Pairs of radioimmunoassays, each of which include a two-dimensional matrix of standards, have been previously employed to resolve specificity problems in steroid immunoassay. In this study the bivariate radioimmunoassay principle has been applied to simultaneous measurement of plasma antidiuretic hormone, arginine vasopressin, and the synthetic antidiuretic agent 1-deamino-8-D-arginine vasopressin (desmopressin), by utilizing two arginine vasopressin antisera which show significantly different cross-reactivities with the synthetic analog. Data processing consists of mathematical representation of two curved dose-response surfaces followed by solution of this pair of nonlinear simultaneous equations for the unknown arginine vasopressin and desmopressin concentrations. Details of numerical procedures are given in the Appendix. The assay appears entirely adequate in terms of sensitivity, accuracy, and precision for measurement of these antidiuretic agents in clinical samples. No evidence of significant covariance in estimated concentrations could be detected but precision of estimation is (not unexpectedly) a function of the concentration of both agents. The plasma disappearance half-time of desmopressin (probably the second of a biphasic disappearance) was estimated as 37 min in one normal subject, which is in good agreement with a previously reported value of 30 min.  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