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   5569篇
  免费   352篇
  国内免费   15篇
耳鼻咽喉   48篇
儿科学   126篇
妇产科学   46篇
基础医学   818篇
口腔科学   76篇
临床医学   376篇
内科学   1464篇
皮肤病学   239篇
神经病学   394篇
特种医学   174篇
外科学   1125篇
综合类   33篇
预防医学   95篇
眼科学   62篇
药学   353篇
中国医学   16篇
肿瘤学   491篇
  2023年   28篇
  2021年   120篇
  2020年   66篇
  2019年   93篇
  2018年   130篇
  2017年   90篇
  2016年   122篇
  2015年   111篇
  2014年   131篇
  2013年   175篇
  2012年   275篇
  2011年   289篇
  2010年   156篇
  2009年   129篇
  2008年   235篇
  2007年   269篇
  2006年   224篇
  2005年   213篇
  2004年   252篇
  2003年   245篇
  2002年   278篇
  2001年   215篇
  2000年   192篇
  1999年   163篇
  1998年   70篇
  1997年   50篇
  1996年   45篇
  1995年   47篇
  1994年   46篇
  1993年   37篇
  1992年   117篇
  1991年   118篇
  1990年   123篇
  1989年   140篇
  1988年   82篇
  1987年   111篇
  1986年   78篇
  1985年   87篇
  1984年   71篇
  1983年   52篇
  1982年   29篇
  1981年   26篇
  1979年   42篇
  1978年   38篇
  1977年   30篇
  1972年   23篇
  1971年   28篇
  1969年   29篇
  1968年   24篇
  1967年   28篇
排序方式: 共有5936条查询结果,搜索用时 342 毫秒
71.
We report on a 19-month-old girl with a derivative chromosome 9 and a recombinant chromosome 12 resulting from a maternal balanced complex rearrangement involving chromosomes 8, 9, and 12. The karyotype of the phenotypically normal mother was 46,XX,t(8;12) (9;12) (8qter→8p23::12q12→12q15::9q32→9qter;9pter→9q32::12q15→12qter;12pter→12q12::8p23→8pter). The child's karyotype was 46,XX,?9,?12, +der(9) (9pter→9q32::12q15→12qter),+rec(12) (12pter→12q15::9q32→9qter) mat. The child had severe growth retardation, minor anomalies including trigonocephaly, hypertelorism, broad nasal root, apparently low-set and posteriorly angulated ears, triangular face, pectus carinatum, clinodactyly of fifth fingers, and almost normal psychomotor development. To the best of our knowledge, there have been only 3 previous reports of recombination derived from parental complex chromosome rearrangements. In the recombination products, the chromosomes were apparently balanced and the offspring had no clinical abnormalities. The present case exhibited abnormalities and may have a submicroscopic aberration of 12q arising from crossing over during maternal meiotic pairing, although her chromosomes appeared to be balanced. © 1993 Wiley-Liss, Inc.  相似文献   
72.
73.
Cisplatin, cis-dichlorodiamine platinum (II), was incorporated in a needle-type copolymer formulation (0.8 mm diameter, 6 mm long) by radiation-induced polymerization. The copolymer used was copoly(diethylene glycol dimethacrylate/polyethylene glycol #600 dimethacrylate, 80/20 vol%). This copolymer, containing 6 mg of cisplatin, was implanted into the kidney of adult male Wistar rats (420 +/- 20 g). A total of 70 d was required for 100% release of cisplatin in vivo. The kidney tissue surrounding the formulation was strongly necrotized by the action of cisplatin. Two layers of necrosis could be distinguished: necrotic tissue surrounding the formulation and necrobiotic tissue surrounding the necrotic tissue. The amount of necrotic tissue changed markedly over time, but no change was apparent in the amount of necrobiotic tissue. The maximal amounts of necrotized tissue were observed 14 d after implantation: 3100 microns and 600 microns thick for the necrotic and necrobiotic tissues, respectively.  相似文献   
74.
75.
Tumor necrosis factor alpha (TNF-alpha) not only induces apoptotic signals but also causes antiapoptotic and regenerative responses in the liver. However, the molecular mechanism(s) of the latter events remains unclear. In the present study, we examined TNF-alpha-induced genes in Hc human normal (unsensitized) hepatocytes by cDNA microarray analysis. Interleukin-8 (IL-8) induction was the most pronounced of the upregulated genes. The IL-8 protein level was also increased. IL-8 belongs to the ELR-CXC chemokine family and appears to exert mitogenic and antiapoptotic functions in other cell systems. IL-8 expression by TNF-alpha was inhibited when two survival signals, nuclear factor kappaB (NF-kappaB) and phosphatidylinositol 3-kinase (PI3K)/Akt, were inhibited by a mutant form of inhibitor of NF-kappaB (IkappaB); by dominant negative (kinase-dead) Akt; or by treatment with LY 294002, an inhibitor of PI3K. TNF-alpha induced apoptosis in Hc cells that were sensitized by inhibition of NF-kappaB and PI3K activation. IL-8 administration protected mice against concanavalin A-induced hepatitis in vivo. IL-8 also rescued the sensitized Hc cells, at least in part, from TNF-alpha-induced apoptosis in vitro. TNF-alpha inhibited DNA synthesis in unsensitized Hc cells in the absence of serum. Exogenous IL-8 reversed, though anti-IL-8 neutralization antibody enhanced, growth inhibition by TNF-alpha. These results indicate that IL-8, the production of which is stimulated by TNF-alpha, inhibits apoptosis of sensitized hepatocytes and releases normal (unsensitized) hepatocytes from growth inhibition induced by TNF-alpha.  相似文献   
76.
The experimental study of peripheral nerve regeneration has depended heavily on the use of a nerve chamber in which the stumps of the transected nerve are inserted. A large variety of chamber fillings and chamber types have been used in an effort to induce a higher quality of regeneration across the gap initially separating the two stumps. In this study we studied the morphology of nerves regenerated across a 15 mm gap following implantation of a series of five chambers. The chambers were fabricated from type I collagen and possessed identical pore volume fractions as well as average pore diameters, but differed in cross-link density continuously along the series. The residual mass of the implanted chambers at 9 weeks was observed to increase continuously with increasing cross-link density along the series, indicating a continuous decrease in degradation rate. The quality of regenerated nerves, determined by the number of large diameter fibers (A-fibers) per nerve, the average diameter of all axons and the ratio of area occupied by axons (N-Ratio), was superior at an intermediate level of chamber degradation rate. The maximal quality of peripheral nerve regeneration corresponded to an optimal degradation rate with an estimated chamber half-life of approximately 2-3 weeks following implantation. A speculative mechanistic explanation of the observed optimum focuses on the hypothetical role of cell and cytokine traffic that may take place through holes in the chamber generated by the degradation process. The data show the presence of a hitherto unreported optimal chamber degradation rate that leads to regenerated nerves of maximum quality.  相似文献   
77.
An expression of mRNA coding the calcium-activated Cl- channel-1 (CLCA1) in rabbit gastric parietal cells was examined to verify the possibility that the CLCA1 mediates housekeeping Cl- channels in the basolateral membrane. In whole-cell voltage-clamp experiments of rabbit parietal cells, A23187 (2 microM), a Ca2+ ionophore, activated the basolateral Cl- channels. The partial cDNA fragment of rabbit CLCA1 could be amplified from the total RNA of tracheal epithelium. A Northern blot analysis showed that rabbit CLCA1 mRNA of 3.4 kb is highly expressed in the tracheal epithelium, but not in the gastric parietal cells. Even in a more sensitive detection of rabbit CLCA1 mRNA by RT-PCR, no signal could be observed in the gastric parietal cells. These results suggest that the CLCA1 protein may not be a subunit of the housekeeping Ca2+ -dependent Cl- channel in the basolateral membrane of rabbit gastric parietal cells.  相似文献   
78.
I-J as an Inducible T Cell Receptor for Self   总被引:4,自引:0,他引:4  
"Jedenfalls, wenn man davorsteht, dann sieht man sich selbstaber eben nicht wie in einem gewöhnlichen Spiegel, versteht sich. Man sieht nicht sein Äusseres, sondern man sieht sein wahres inneres Wesen. so wie es in Wirklichkeit beschaffen ist. Wer da durch will, der muß - um es mal so auszudrücken -in sich selbst hineingehen."
Die undendliche Geschichte, bei Michael Ende, K. Thiehemanns Verlag, Stuttgart, 1979.  相似文献   
79.
M Ozawa  A Asano  Y Okada 《Virology》1979,99(1):197-202
When HANA protein of HVJ (Sendai virus) was denatured by dithiothreitol treatment, concanavalin A added to the system or influenza virus hemagglutinin reconstituted with treated HVJ-envelope to form hybrid by SM-2 dialysis method could not replace a role of HANA for hemolysis. Binding of the treated samples to erythrocytes was restored by them, however. Thus, a hypothesis is proposed that intactness of not only F but also HANA protein of HVJ is required for envelope-cell fusion, in other words, HANA protein of HVJ may play some positive role other than binding in the process of the virus-induced hemolysis.  相似文献   
80.
Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.  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