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   2351211篇
  免费   171725篇
  国内免费   3334篇
耳鼻咽喉   32061篇
儿科学   75948篇
妇产科学   62722篇
基础医学   348369篇
口腔科学   63693篇
临床医学   211553篇
内科学   457545篇
皮肤病学   51734篇
神经病学   185542篇
特种医学   88042篇
外国民族医学   489篇
外科学   353971篇
综合类   47538篇
现状与发展   12篇
一般理论   849篇
预防医学   182859篇
眼科学   54355篇
药学   175175篇
  11篇
中国医学   4575篇
肿瘤学   129227篇
  2021年   19008篇
  2019年   19550篇
  2018年   27085篇
  2017年   20373篇
  2016年   22761篇
  2015年   25658篇
  2014年   36127篇
  2013年   53990篇
  2012年   74747篇
  2011年   79465篇
  2010年   47109篇
  2009年   44598篇
  2008年   74668篇
  2007年   79528篇
  2006年   80341篇
  2005年   77828篇
  2004年   74408篇
  2003年   71732篇
  2002年   69407篇
  2001年   108768篇
  2000年   111488篇
  1999年   93521篇
  1998年   27001篇
  1997年   23671篇
  1996年   24068篇
  1995年   22726篇
  1994年   20905篇
  1993年   19723篇
  1992年   72045篇
  1991年   70110篇
  1990年   68421篇
  1989年   65695篇
  1988年   60333篇
  1987年   59148篇
  1986年   55243篇
  1985年   53014篇
  1984年   39334篇
  1983年   33414篇
  1982年   19870篇
  1979年   35878篇
  1978年   25668篇
  1977年   21239篇
  1976年   20354篇
  1975年   21828篇
  1974年   26173篇
  1973年   24822篇
  1972年   23229篇
  1971年   22056篇
  1970年   20274篇
  1969年   19329篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Preclinical and clinical investigations currently underway are employing novel strategies for combining vaccines with conventional and experimental anticancer therapies. To date, the FDA has not approved a therapeutic cancer vaccine. However, the results of recent investigations suggest an increasing role for vaccines in new models of combination therapy for many types of cancer. This article reviews and discusses therapeutic cancer strategies that employ vaccines in combination with local radiation, chemotherapy, hormone therapy, and anti-CTLA-4 mAb. Preclinical studies have shown that certain anticancer agents have immune modulatory effects that result in up-regulation of surface expression of MHC molecules, tumor-associated antigens, or Fas on malignant cells, rendering them more susceptible to immune destruction. Preliminary results of clinical studies using combination strategies have demonstrated a postvaccination antigen cascade, prolonged time to disease progression, and improved overall survival. Several larger randomized trials are ongoing, and more are required to support these findings.  相似文献   
992.
The synthesis of barbituric acid derivatives containing α-phenylskatyl residues substituted at C(5) is described. The initial compound was α-phenylnorgramine, which had been previously successfully used for the alkylation of a series of CH-acids, in particular, for the synthesis of diethyl-1H-indol-3-yl(phenyl)methylmalonate. This compound has been used to obtain a series of 2-thiobarbituric acid derivatives, which are expected to possess antioxidant, membrane protector, and radioprotector properties.__________Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 1, pp. 29 – 33, January, 2005.  相似文献   
993.
Abstract: We have designed and synthesized a new series of azapeptides which act as potential inhibitors of cathepsin B and/or cathepsin K. Their structures are based upon the inhibitory sites of natural cysteine protease inhibitors, cystatins. For the synthesized azapeptides, the equilibrium constants for dissociation of inhibitor–enzyme complex, Ki, were determined. Comparison of these values indicated that all of the azainhibitors act much stronger toward cathepsin B. Z‐Arg‐Leu‐His‐Agly‐Ile‐Val‐OMe ( 7 ) proved to be approximately 500 times more potent for cathepsin B than for cathepsin K. To be able to explain the obtained experimental values we used the molecular dynamics procedures to analyze the interactions between cathepsin B and compound 7 . We also determined the structure of the most potent and selective cathepsin B azainhibitor by means of NMR studies and theoretical calculations. In this report, we describe SAR studies of azapeptide inhibitors indicating the influence of the conformational flexibility of the examined compounds on inhibition of cathepsins B and K.  相似文献   
994.
Diesters based on isosteviol and dicarboxylic acids were synthesized and tested for antituberculous activity. Isosteviol and some of its derivatives exhibit appreciable tuberculostatic properties in vitro, the activity being dependent on the length of the polymethylene spacer connecting two ent-beyeran fragments. The mechanism of the antituberculous action of isosteviol derivatives are discussed. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 9, pp. 12–13, September, 2006.  相似文献   
995.
996.
It is usual at the end of a year for top tens to feature large in our collective consciousness. These inevitably include the occasional controversial selection and without fail will overlook a number of gems, whether in the field of literature, art, or science. The approaches to such compilations include personal selections, convening expert committees through to letting the market decide. However, it is well recognised that experts can be wrong and markets distorted. A novel approach to identifying the key publications in the field of medicine, Faculty of 1000 Medicine (http://www.f1000medicine.com), uses faculty evaluations to assign ratings to published papers within topics and categories, bringing a flavour of the dynamism of post hoc peer review to biological sciences that exists in other fields of scholarship. Archives of Disease in Childhood has also developed a market led system of peer evaluation through its web based top ten most read articles feature.  相似文献   
997.
BACKGROUND: Alternaria alternata is one of the most important allergenic fungi worldwide. Mannitol dehydrogenase (MtDH) has previously been shown to be a major allergen of Cladosporium herbarum and cross-reactivity has been demonstrated for several fungal allergens. OBJECTIVE: The present study's objective was to clone the MtDH from an A. alternata cDNA library, express and purify the recombinant non-fusion protein and test its IgE-binding properties. Methods A cDNA library prepared from A. alternata hyphae and spores was screened for mannitol dehydrogenase by DNA hybridization with the radioactively labelled C. herbarum homologue as a probe. The resulting clone was sequenced and heterologously expressed in Escherichia coli as a recombinant non-fusion protein, which was purified to homogeneity and analysed for its IgE-binding capacity. RESULTS: The coding sequence of the full-length cDNA clone comprises 798 bp encoding a protein with a molecular mass of 28.6 kDa and a predicted pI of 5.88. Protein sequence analysis revealed an identity of 75% and a homology of 86% between the MtDHs of A. alternata and C. herbarum. The functional mannitol dehydrogenase was expressed in the E. coli strain BL21(DE3) transformed with the vector pMW172 and purified to homogeneity. The enzyme catalyses the NADPH-dependent conversion of d-fructose to d-mannitol. In IgE-ELISA and immunoblots, MtDH is recognized by 41% of A. alternata-allergic patients. In vivo immunoreactivity of the recombinant MtDH was verified by skin prick testing. Finally, inhibition-ELISA experiments confirmed cross-reactivity between the MtDHs of A. alternata and C. herbarum. CONCLUSION: Mannitol dehydrogenase (Alt a 8) represents an important new allergen of the ascomycete A. alternata that might be suitable for improving diagnostic and therapeutic procedures.  相似文献   
998.
999.
1000.
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