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   350105篇
  免费   18661篇
  国内免费   1137篇
  369903篇
  2021年   2076篇
  2018年   14934篇
  2017年   13692篇
  2016年   11410篇
  2015年   4404篇
  2014年   5522篇
  2013年   7565篇
  2012年   12675篇
  2011年   21576篇
  2010年   18090篇
  2009年   13542篇
  2008年   17685篇
  2007年   19434篇
  2006年   8419篇
  2005年   8029篇
  2004年   8607篇
  2003年   8322篇
  2002年   8020篇
  2001年   12013篇
  2000年   11284篇
  1999年   8604篇
  1998年   2693篇
  1997年   2456篇
  1996年   2259篇
  1995年   2022篇
  1992年   6619篇
  1991年   6701篇
  1990年   6593篇
  1989年   6520篇
  1988年   6008篇
  1987年   5675篇
  1986年   5122篇
  1985年   5346篇
  1984年   4179篇
  1983年   3465篇
  1982年   2334篇
  1981年   2004篇
  1979年   3871篇
  1978年   2943篇
  1977年   2722篇
  1976年   2651篇
  1975年   3238篇
  1974年   3596篇
  1973年   3561篇
  1972年   3470篇
  1971年   3354篇
  1970年   2681篇
  1969年   2618篇
  1968年   2401篇
  1967年   2122篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A- and B-type lamins are differentially expressed in normal human tissues   总被引:12,自引:0,他引:12  
 A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel of antibodies specific for the individual lamin subtypes. By use of immunoprecipitation and two-dimensional immunoblotting techniques we demonstrated that these antibodies do not cross-react with other lamin subtypes and that a range of different phosphorylation isoforms is recognized by each antibody. The lamin B2 antibodies appeared to decorate the nuclear lamina in all tissues examined, except hepatocytes, in which very little lamin B2 expression was observed. In contrast to previous studies, which suggested the ubiquitous expression of lamin B1 in mammalian tissues, we show that lamin B1 is not as universally distributed throughout normal human tissues as was to be expected from previous studies. Muscle and connective tissues are negative, while in epithelial cells lamin B1 seemed to be preferentially detected in proliferating cells. These results correspond well with those obtained for lamin B1 in chicken tissues. The expression of A-type lamins is most prominent in well-differentiated epithelial cells. Relatively undifferentiated and proliferating cells in epithelia showed a clearly reduced expression of A-type lamins. Furthermore, most cells of neuroendocrine origin as well as most hematopoietic cells were negative for A-type lamin antibodies. Accepted: 4 February 1997  相似文献   
992.
993.
994.
Inspiratory activity generated by superfusedin situ semi-isolated medullo-spinal preparations of newborn (one-day-old) and four- to five-day-old rats was recorded from then. phrenicus before and after transverse sectioning of the ventrolateral part of the medulla (VLPM) at different levels. Under similar experimental conditions, the frequency of inspiratory discharges (ID) and their integral intensity, reflecting the volume and temporal parameters of inspiration, are much lower in one-day-old rats, as compared with those in four- to five-day-old animals. Specific roles of different VLPM levels in respiration control in young rats are demonstrated. Transection of the VLPM below the most rostral VLPM portion, corresponding to theM chemosensitive zone, caused a significant increase in the ID frequency and a decrease in the ID integral intensity. Transection performed below the intermediate VLPM region, corresponding to theS chemosensitive zone, resulted in a significant decrease in both ID frequency and ID integral intensity, up to total ID blockade in 5 of 12 1-day-old preparations. This finding can be interpreted as an indication of morphofunctional immaturity of the respiratory network in the caudal VLPM regions in newborn animals. Comparative analysis of ID pattern showed that this activity in one-day-old rats is more or less gasping-like, while that in four- to five-day-old animals is eupnoe-like. The results allow us to conclude that the level of maturity of morphofunctional organization of medullary respiratory networks considerably differs in newborn and older animals. The mechanisms responsible for formation and control of respiratory activity in early postnatal period of rats are discussed.Neirofiziologiya/Neurophysiology, Vol. 27, No. 5/6, pp. 387–395, September–December, 1995.  相似文献   
995.
The results of complementation analysis of nitrosoguanidine-induced mutants of F-like drd-plasmid pAP18-1 (Tc, ColV) testified to the existence of at least 3 tra regions (tra1, tra2, tra3) and regulating locus fin V in the genome of this plasmid. By means of molecular cloning of tra2 region and locus fin V of plasmid pAP18-1drd were located in Sall-fragment f5 (3.9 MD).  相似文献   
996.
997.
The article reports experimental data on new bacteria, the so-called ‘stone nannobacteria’. Recent publications in Russia and abroad show that this bacterial species may cause various human ailments, thus being a serious environmental hazard. According to our findings, one of the natural habitats of nannobacteria is water which aggregates the nannobacteria-related ecological problem.  相似文献   
998.
DdeI polymorphism in the HLA-DRA regulatory region   总被引:1,自引:0,他引:1       下载免费PDF全文
  相似文献   
999.
For 35 of 50 patients with rheumatoid arthritis traditional drug therapy was a minor success for a long time. Without any modifications of the drug therapy every patient went through a course of hyperbaric oxygenation (HBO): 21 sessions under 1.7 ata for 40 min. Good clinical results both immediate and remote have been obtained. The effect of HBO on the immune system of the patients has intensified the suppressive function of T-lymphocytes (especially with systemic symptoms of the disease), normalized cell-bound immunity and decreased the serum concentration in immune complexes.  相似文献   
1000.
Recent data and concepts on the structure and functioning of apolipoprotein genes as well as on the role of hereditary factors in pathogenesis of atherosclerosis are reviewed. The most important variants of inherited disorders in the system of apolipoproteins promoting the development of atherosclerosis are considered. Special attention is paid to the RFLP of apolipoprotein genes which serves as a peculiar genetic background, increasing probability of the atherosclerosis development in certain individuals.  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