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   390886篇
  免费   35173篇
  国内免费   304篇
  426363篇
  2018年   3951篇
  2017年   3787篇
  2016年   5103篇
  2015年   5458篇
  2014年   6916篇
  2013年   9956篇
  2012年   11075篇
  2011年   12012篇
  2010年   8265篇
  2009年   7417篇
  2008年   10641篇
  2007年   11079篇
  2006年   10498篇
  2005年   9970篇
  2004年   9936篇
  2003年   9625篇
  2002年   9546篇
  2001年   18648篇
  2000年   18870篇
  1999年   14248篇
  1998年   4394篇
  1997年   4533篇
  1996年   4300篇
  1995年   3969篇
  1994年   3828篇
  1992年   11450篇
  1991年   11290篇
  1990年   11171篇
  1989年   10938篇
  1988年   10154篇
  1987年   9587篇
  1986年   8653篇
  1985年   9056篇
  1984年   7267篇
  1983年   6235篇
  1982年   4316篇
  1981年   3952篇
  1980年   3779篇
  1979年   6819篇
  1978年   5247篇
  1977年   4778篇
  1976年   4607篇
  1975年   5331篇
  1974年   5899篇
  1973年   5832篇
  1972年   5302篇
  1971年   4835篇
  1970年   4316篇
  1969年   3999篇
  1968年   3824篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
A patient is presented who had recurrent carpal tunnel syndrome symptoms in his left hand 1 year after having undergone release of the transverse carpal ligament. On exploration, this was found to be due to an aneurysm of a median artery and possibly scarring due to this compression around the branches of the bifurcated median nerve. This represents the first case in the literature to comment on (1) the absence of bilaterality of the anatomic finding and (2) carpal tunnel syndrome relative to median artery aneurysm. With this in mind, a plea is made for careful exploration of the carpal tunnel, maintaining an incision as far to the ulnar side of the median nerve as technically possible with thorough visualization of the contents of the tunnel and any anatomic variance involved. The incidence of the combination of aberrant median artery with high bifurcation of the median nerve is unknown, as is the incidence of aneurysm of the median artery.  相似文献   
922.
26 male F2 hybrids between spontaneously hypertensive (SHR) and normotensive control (WKY) rats (SHRxWKY)F2 were segregated according to their c-src genotype into SS and WW homozygous groups, corresponding to SHR or WKY and WS heterozygous group. Na, K cotransport in erythrocytes in the WW group was equal to that of WKY and differs significantly from that of WS and SS groups (the rate of Na, K cotransport in latter groups was close to that of SHR). Ca content of RBC in WW group was equal to that of WKY, lower than that of WS and SS groups which in turn was significantly lower than in SHR, indicating polygenic control of the trait. Authors conclude that the c-src locus itself or some other loci inherited in conjunction with c-src determines both the increase of Na, K cotransport and calcium content in erythrocytes of SHR.  相似文献   
923.
The behavioral effects of opiate agonists and antagonists were studied on the female aggression model. Mu-agonist buprenorphine more selectively decreased maternal aggression than kappa-agonist tifluadom. Kappa-agonists (bremazocine, tifluadom) increased passive defence in lactating female rats. Ethopharmacological data shows predominant involvement of brain mu-opiate receptor system in the integrative processes of maternal behavior and maternal aggression in particular.  相似文献   
924.
The reaction of leech nervous system after elimination of individual mechanosensory neuron by intracellular Pronase injection were studied. In the motor neurons connected with killed cells at 14-90th days after the operation there were the changes of the resting membrane potential and amplitude of postsynaptic potentials developed by the stimulation of mechanosensory neuron. It is suggested that the leech nervous system serves as the dynamic formation depending on changes of neuronal ensemble structure.  相似文献   
925.
A dual-microelectrode voltage clamp technique was used for recording voltage-dependent calcium current (Ica) in unidentified neurons isolated fromHelix pomatia. Neither intracellular injection of cyclic adenosine monophosphate (cAMP; 10 nA, 5 min) nor intracellular application of dibutyril-cAMP (dcAMP; 1 mM, 10–20 min) induced a change in normal Ica or produce a reversible 10–20% reduction in amplitude. Adding S-100 protein fraction antibodies to the external medium led to the onset of calcium-dependent inactivation of Ica, bringing amplitude of Ica down to 15±12% of its initial level. Either cAMP or dcAMP then restored inhibited Ica to 50±11% of its original level. It was found that the effects of cAMP on Ica of intact neurons depend on level of cytoplasmic Ca2+.Institute for Brain Research, All-Union Center for Mental Health Research, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 247–252, March–April, 1989.  相似文献   
926.
Hemoglobin binding to deglycosylated haptoglobin   总被引:1,自引:0,他引:1  
The carbohydrate portion of polymeric haptoglobin was gradually removed by exoglycosidases in order to investigate its role in complex formation between haptoglobin and hemoglobin. Total removal of sialic acid diminished the haptoglobin-hemoglobin complex formation 15%. Removal of about 25% of the galactose residues from asialohaptoglobin, i.e., about 40% of the total weight of the carbohydrate moiety, totally inhibited the ability of haptoglobin to form complex with hemoglobin and react with haptoglobin-specific antibodies. Liberation of further galactose residues resulted in slow precipitation of the protein. Removal of a similar part of the carbohydrate moiety from haptoglobin-hemoglobin complex did not liberate hemoglobin from it, and the complex reacted with haptoglobin antibodies. The combined data indicate that the carbohydrate portion is essential for the functionally active form of polymeric haptoglobin to complex with hemoglobin, but it hardly has any direct role in the binding event, and other factors are responsible for the stability of the complex.  相似文献   
927.
Signals of translation initiation of operons of Haemophilus influenzae ribosomal proteins were predicted. This process is regulated by the formation of secondary RNA structures to which one of the proteins encoded in a particular operon binds. In some cases, these structures imitate the region of protein binding to rRNA. Predictions are made by comparing with homologous operons of Escherichia coli and analogous regions of rRNA and by estimating the energy of secondary structure formation. It is shown that this regulatory mechanism occurs: in operons L11, S10, S15, spc, and alpha of H.influenzae and, probably, in operon S15 of Helicobacter pylori, Bacillus subtilis, and Mycoplasma genitalium.  相似文献   
928.
929.
930.
O A Smirnova  N V Stepanova 《Biofizika》1975,20(6):1095-1098
A mathematical model of autoimmunity is developed. This model is a system of two nonlinear differential equations, which describe the concentration dynamics of tissue cells and agressive lymphocytes. An analysis of the solutions shows that this model reproduces general behaviour of autoimmune diseases.  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