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   796527篇
  免费   82457篇
  国内免费   250篇
  879234篇
  2018年   7931篇
  2017年   7585篇
  2016年   10635篇
  2015年   13453篇
  2014年   16027篇
  2013年   23129篇
  2012年   25971篇
  2011年   26757篇
  2010年   18271篇
  2009年   16890篇
  2008年   23913篇
  2007年   24884篇
  2006年   23259篇
  2005年   22366篇
  2004年   22146篇
  2003年   21312篇
  2002年   20812篇
  2001年   34739篇
  2000年   34197篇
  1999年   27572篇
  1998年   10178篇
  1997年   10264篇
  1996年   9839篇
  1995年   9059篇
  1994年   8721篇
  1993年   8752篇
  1992年   22333篇
  1991年   21917篇
  1990年   21369篇
  1989年   20814篇
  1988年   19081篇
  1987年   18323篇
  1986年   17093篇
  1985年   16954篇
  1984年   13934篇
  1983年   12181篇
  1982年   9230篇
  1981年   8355篇
  1980年   7755篇
  1979年   12939篇
  1978年   10204篇
  1977年   9191篇
  1976年   8804篇
  1975年   9819篇
  1974年   10486篇
  1973年   10354篇
  1972年   9479篇
  1971年   8458篇
  1970年   7385篇
  1969年   7255篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
101.
In a multicentre, randomised, prospective trial 89 patients (67 children and 22 adults) with the minimal change nephrotic syndrome were treated with three intravenous pulses of methylprednisolone followed by low dose oral prednisone for six months (group given methylprednisolone) or with high dose oral prednisone for four weeks followed by low dose oral prednisone for five months (control group). Five patients in the group given methylprednisolone and one in the control group did not respond initially. The time to response was shorter in children treated with methylprednisolone. No significant differences between the two groups were observed in the number of patients who relapsed or number of relapses per patient per year. Patients given methylprednisolone tended to relapse earlier than patients in the control group. Side effects related to treatment were significantly fewer in the group given methylprednisolone than in the control group. These data suggest that a short course of methylprednisolone pulses followed by low dose oral prednisone is only marginally less effective than a regimen of high dose oral steroids but can improve the ratio of risk to benefit associated with treatment of the minimal change nephrotic syndrome.  相似文献   
102.
Monosomy 21: a new case confirmed by in situ hybridization   总被引:4,自引:0,他引:4  
Summary A new case of total monosomy 21 in a newborn is described. The diagnosis was first made using the cytogenetic data; it was then confirmed by the dosage of copper-superoxide dismutase (SOD-1) which showed a 50% decrease. In situ hybridization with a probe previously assigned to chromosome 21 was used to rule out the possibility of a partial monosomy with an unbalanced reciprocal translocation.  相似文献   
103.
1. Because L-asparagine augments insulin release evoked by L-leucine, the metabolism of these two amino acids was investigated in rat pancreatic islets. 2. L-Leucine inhibited the uptake and deamidation of L-asparagine, but failed to exert any obvious primary effect upon the further catabolism of aspartate derived from exogenous asparagine. 3. L-Asparagine augmented the oxidation of L-leucine, and effect possibly attributable to activaion of 2-ketoisocaproate dehydrogenase. 4. The association of L-asparagine and L-leucine exerted a sparing action on the utilization of endogenous amino acids, so that the integrated rate of nutrients oxidation was virtually identical in the sole presence of L-leucine and simultaneous presence of L-asparagine and L-leucine, respectively. 5. It is proposed that the enhancing action of L-asparagine upon insulin release evoked by L-leucine is attributable to an increased generation rate of cytosolic NADPH rather than any increase in nutrients oxidation.  相似文献   
104.
105.
Temperature-sensitive (ts) mutations of the G101 phage were isolated after mutagenesis with hydroxylamine. A complementation analysis of 61ts mutants showed that these mutants may be divided into at least 12 complementation groups. Twots mutants probably originated in genes which control lytic functions of the G101 phage. It was shown by three factor crosses that all of the 12ts mutations tested are localized on that side of the “c” region where the probablecI repressor gene is positioned. Sevents mutations is closely linked to thecI 26 clear marker, three exhibit a closer linkage and two do not exhibit any linkage withcI. All mutations isolated until now can be arrange linearly. According to the present knowledge the preliminary genetic map of the G101 phage is linear.  相似文献   
106.
107.
With the use of a patch-clamp technique in the whole-cell configuration, we studied the effects of pinacidil and its fluorine derivatives on A-type potassium current (I A) through the membrane of pyramidal neurons of the rat hippocampus. Hydrogen peroxide (10 mM) exerted no influence on the rate of inactivation ofI A; therefore, this current is probably mediated by Shal Kv4.2 potassium channels. Pinacidil demonstrated the properties of a weakI A blocker: in the 500 μM concentration it blocked about 45% of the current, while 50 μM of pinacidil fluorine derivatives were capable of blocking up to 30% ofI A. The effects of pinacidil and its derivatives showed no dependence on the stimulating potential. A similar pattern of the effects of pinacidil fluorine derivatives, which are an order of magnitude stronger than those of pinacidil itself, allows us to suppose that the imine nitrogen of the tested compounds is significantly more involved in the molecular interaction with the site of an A-type potassium channel than the pyridine nitrogen.  相似文献   
108.
109.
110.
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