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   419969篇
  免费   43635篇
  国内免费   196篇
  463800篇
  2016年   4515篇
  2015年   5949篇
  2014年   7052篇
  2013年   10619篇
  2012年   11481篇
  2011年   11960篇
  2010年   8143篇
  2009年   7473篇
  2008年   10683篇
  2007年   11334篇
  2006年   10672篇
  2005年   10151篇
  2004年   10248篇
  2003年   10013篇
  2002年   9815篇
  2001年   17346篇
  2000年   17390篇
  1999年   14051篇
  1998年   4977篇
  1997年   5286篇
  1996年   5011篇
  1995年   4727篇
  1994年   4632篇
  1993年   4629篇
  1992年   12266篇
  1991年   12071篇
  1990年   12083篇
  1989年   11856篇
  1988年   11165篇
  1987年   10500篇
  1986年   9819篇
  1985年   10238篇
  1984年   8439篇
  1983年   7275篇
  1982年   5613篇
  1981年   5020篇
  1980年   4694篇
  1979年   8082篇
  1978年   6300篇
  1977年   5940篇
  1976年   5672篇
  1975年   6130篇
  1974年   6697篇
  1973年   6568篇
  1972年   6122篇
  1971年   5535篇
  1970年   4767篇
  1969年   4782篇
  1968年   4453篇
  1967年   3808篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
981.
982.
In dried oriented samples of purple membrane isolated from Halobacterium halobium, the photoelectric activity decreases and the light adaptation vanishes when the water content of the sample is lowered. In the photocycle the first steps of the proton movement were accelerated with decreasing humidity, while the last steps of the photocycle could not be observed. From the analysis of the photoelectric signal we conclude that at low humidities the protons move forward in the L decay and return to their original place during M decay.  相似文献   
983.
Summary Two varieties of tomato (Pusa Rubi and Selection 120) positively responded to algal inoculation in terms of the yield of fruits and shoots, but there was no significant effect on the vitamin C content of the fruits. A combined application of urea and algae was more effective than the application of urea alone.  相似文献   
984.
D.G. McGowan 《CMAJ》1985,132(9):1005-1006
  相似文献   
985.
In the mesenterium of rats it was found that an overacidity of the blood flowing in the area of microcirculation and caused by irrigation with acid media may be objectively represented in the clearing of venols measurable by means of video technique. The cause of this clearing process is the swelling of erythrocytes setting in at lower pH-values. According to in-vitro findings this swelling of erythrocytes will lead to an increase of the apparent viscosity of the blood fluid or blood cell suspension respectively in conformity with the increase of hematocrit connected with it.  相似文献   
986.
Efferent neuronal projections of the mesencephalic locomotor region were investigated in cats using a horseradish peroxidase retrograde axonal transport technique. It was found that neurons located within the locomotor area form ascending and descending projections to many structures of the spinal cord and the brain but that short-axon connections running to the reticular formation of the midbrain and the medulla predominate. Small numbers of long-axon fibers may merge into the locomotor strips of the medulla and the spinal cord. The locomotor regions of the two halves of the midbrain are interlinked.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 117–125, January–February, 1986.  相似文献   
987.
The effect of alkyl resorcin isolated from the cells of Azotobacter chroococcum and of its structural analog devoid of the alkyl chain (resorcin) on liver microsomes and brain synaptosomes of the rat as well as on rabbit skeletal muscle sarcoplasmic reticulum fragments during activation of lipid peroxidation was studied. Alkyl resorcin was shown to produce a much more potent antioxidant effect as compared with resorcin, since it inhibited lipid peroxidation in all the three types of membranes under study at much lower concentrations. Both alkyl resorcin and resorcin which inhibit lipid peroxidation prevented lipid peroxidation-induced structural-functional damages of synaptosomal and sarcoplasmic reticulum fragment membranes. Unlike resorcin, alkyl resorcin exerted an additional effect on brain synaptosomal membranes which consisted in the stabilization of barrier functions of membranes during incomplete inhibition of lipid peroxidation. The cumulative data suggest that stabilization necessitates the presence of both resorcin radical and alkyl chain in the alkyl resorcin molecule.  相似文献   
988.
989.
The nephropathy induced by mercuric chloride was assessed in unilaterally nephrectomized (NPX) and sham-operated (SO) rats using histological and urinalysis techniques. This assessment was carried out in order to test whether or not rats are more susceptible to the nephrotoxic effects of mercuric chloride after unilateral nephrectomy and a period allowing for compensatory renal growth. Twelve days after surgery both NPX and SO rats were given a single 1.5, 2.0 or 2.5 mumol/kg dose of mercuric chloride (i.v.). Twenty-four hours after the 1.5 or 2.0 mumol/kg dose of mercuric chloride was administered, cellular and tubular necrosis in the pars recta segments of proximal tubules in the outer medulla was more severe in NPX rats than in SO rats. Moreover, the urinary excretion of a number of cellular enzymes (e.g. lactate dehydrogenase) and plasma solutes (e.g. albumin) was greater in NPX rats than in SO rats. At the 2.5 mumol/kg dose of mercuric chloride, renal tubular damage was quite extensive in both groups of rats; to such an extent that possible differences in renal tubular damage between the NPX and SO rats could not be determined histologically. However, the urinary excretion of alanine aminopeptidase was greater in the NPX rats than in the SO rats. Therefore, based on the aforementioned findings, rats that have undergone and adapted to a reduction in renal mass (i.e. unilateral nephrectomy) appear to be more vulnerable to the nephrotoxic effects of mercuric chloride than rats with two normal kidneys.  相似文献   
990.
Anabol and blastolysin preparations obtained from L. bulgaricus may contain surface structural components of the initial strain with adhesion activity; of these, one is similar in specificity to L. casei adhesin and the other, to L. plantarum adhesin. The antigenic activity of anabol and blastolysin, evaluated in the immunodiffusion test, does not correlate with their capacity for binding the receptors of susceptible bacterial cells, determined in the Lactobacillus-induced hemagglutination inhibition test.  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