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   4747篇
  免费   309篇
  国内免费   35篇
耳鼻咽喉   82篇
儿科学   114篇
妇产科学   45篇
基础医学   567篇
口腔科学   121篇
临床医学   388篇
内科学   1339篇
皮肤病学   31篇
神经病学   323篇
特种医学   199篇
外科学   809篇
综合类   23篇
一般理论   1篇
预防医学   123篇
眼科学   154篇
药学   247篇
中国医学   3篇
肿瘤学   522篇
  2024年   11篇
  2023年   99篇
  2022年   177篇
  2021年   314篇
  2020年   152篇
  2019年   167篇
  2018年   191篇
  2017年   144篇
  2016年   178篇
  2015年   156篇
  2014年   174篇
  2013年   239篇
  2012年   369篇
  2011年   418篇
  2010年   202篇
  2009年   138篇
  2008年   236篇
  2007年   243篇
  2006年   204篇
  2005年   198篇
  2004年   169篇
  2003年   170篇
  2002年   160篇
  2001年   23篇
  2000年   31篇
  1999年   36篇
  1998年   32篇
  1997年   26篇
  1996年   26篇
  1995年   29篇
  1994年   28篇
  1993年   19篇
  1992年   36篇
  1991年   24篇
  1990年   27篇
  1989年   29篇
  1988年   17篇
  1987年   18篇
  1986年   21篇
  1985年   14篇
  1984年   16篇
  1983年   15篇
  1982年   11篇
  1981年   10篇
  1980年   10篇
  1978年   7篇
  1977年   6篇
  1976年   11篇
  1975年   12篇
  1974年   16篇
排序方式: 共有5091条查询结果,搜索用时 15 毫秒
11.
Summary Reinke's crystals in human Leydig cells were analyzed stereologically to assess their functional role. Testicular tissues were taken from seven older men (57–82 years old) with prostatic carcinoma and also from seven younger men (26–38 y.o.) complaining of male infertility. Sections 0.5 m thick, stained with toluidine blue or Heidenhein's iron-hematoxylin were examined by a point-counting method and with a Particle Measurement Computor System (MC). When the patients were grouped by age, the mean crystal volume, the number of crystals per cell, the volume of crystals per cell and the volume ratio of crystals to cell were significantly larger in the older age group than in the younger age group. In particular, the latter three variables correlated well with the age of subjects, with correlation coefficients of r=0.66–0.85. On the other hand, none of these variables had any correlation with the concentration of plasma testosterone. These results indicate that Reinke's crystals can be considered as degenerative products in cell life but not as facultative constituents for testosterone production.Supported in part by a grant from Medical Foundation of Ehime, Japan  相似文献   
12.
Radiotherapy is one of the most effective treatments for cancers. However, external irradiation provides only small doses to deep-seated cancers, and often causes damage to healthy tissues. It has been reported that 20-30 microm diameter 17Y(2)O(3)-19Al(2)O(3)-64SiO(2) (mol%) glass microspheres are useful for the in situ irradiation of cancers. Yttrium-89 (89Y) in this glass can be neutron bombarded to form the beta-emitter 90Y (half-life=64.1h). When injected in the vicinity of the cancer, such activated glass microspheres can provide a large localized dose of beta-radiation. The Y(2)O(3) content of the glass in the microspheres is limited to only 17 mol%. Chemically durable microspheres with a higher Y(2)O(3) content need to be developed. Phosphorus-31 (31P) with 100% natural abundance can also be activated by neutron bombardment to form the beta-emitter 32P (half-life=14.3d). Chemically durable microspheres containing a high phosphorus content are expected to be more effective for cancer treatment. We prepared pure Y(2)O(3) and YPO(4) microspheres using a high-frequency induction thermal plasma melting technique, and investigated the resulting structure and chemical durability. We successfully prepared smooth, highly spherical polycrystalline Y(2)O(3) and YPO(4) microspheres with diameters in the range 20-30 microm. Both the Y(2)O(3) and YPO(4) microspheres showed high chemical durability in saline solutions buffered at pH=6 and 7. These microspheres are expected to be more effective than the conventional glass microspheres for the in situ radiotherapy of cancer.  相似文献   
13.
We developed a novel method of evaluating biofilm architecture on a synthetic material using green fluorescent protein-expressing Escherichia coli and red fluorescence staining of exopolysaccharides. Confocal laser scanning microscopy observation revealed the time course of the change in the in situ three-dimensional structural features of biofilm on a polyurethane film without structural destruction: initially adhered cells are grown to form cellular aggregates and secrete exopolysaccharides. These cells were spottily distributed on the surface at an early incubation time but fused to form a vertically grown biofilm with incubation time. Fluorescence intensity, which is a measure of the number of cells, determined using a fluorometer and biofilm thickness determined from confocal laser scanning microscopy vertical images were found to be effective for quantification of time-dependent growth of biofilms. The curli (surface-located fibers specifically binding to fibronectin and laminin)-producing Escherichia coli strain, YMel, significantly proliferated on fibronectin-coated polyurethane, whereas the curli-deficient isogenic mutant, YMel-1, did not. The understanding of biofilm architecture in molecular and morphological events and new fluorescence microscopic techniques may help in the logical surface design of biomaterials with a high antibacterial potential.  相似文献   
14.
15.
Two cases of meningioma revealing conspicuous plasmo lymphocytic tissue and hyalinized fibrous tissue components are reported. Histopathological examination of the plasmo lymphocytic infiltration was performed. Both lesions showed polyclonality of plasma cells as revealed by positive reactions for 1gG and paraimmunoglobulin χ- and λ light chains, and amyloid infiltration into the fibrous stroma and blood vessel walls. The histochemical and immunohistochemical characteristics of the lesion in relation to its etiology are briefly discussed. Acta Pathol. Jpn. 32: 190∼194, 1989.  相似文献   
16.
17.
18.
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   
19.
20.
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