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   4253538篇
  免费   330842篇
  国内免费   15204篇
耳鼻咽喉   59204篇
儿科学   132601篇
妇产科学   113693篇
基础医学   647376篇
口腔科学   119873篇
临床医学   384762篇
内科学   767079篇
皮肤病学   106677篇
神经病学   355885篇
特种医学   166988篇
外国民族医学   693篇
外科学   647263篇
综合类   124228篇
现状与发展   24篇
一般理论   2593篇
预防医学   351889篇
眼科学   98358篇
药学   299621篇
  28篇
中国医学   11643篇
肿瘤学   209106篇
  2021年   55682篇
  2019年   58578篇
  2018年   73245篇
  2017年   56074篇
  2016年   61935篇
  2015年   75388篇
  2014年   109712篇
  2013年   175196篇
  2012年   114036篇
  2011年   117562篇
  2010年   122684篇
  2009年   125486篇
  2008年   104883篇
  2007年   111905篇
  2006年   120471篇
  2005年   115705篇
  2004年   117127篇
  2003年   107595篇
  2002年   97593篇
  2001年   148575篇
  2000年   143004篇
  1999年   133811篇
  1998年   69375篇
  1997年   66139篇
  1996年   64085篇
  1995年   59385篇
  1994年   53696篇
  1993年   50003篇
  1992年   97953篇
  1991年   94203篇
  1990年   90546篇
  1989年   89040篇
  1988年   82928篇
  1987年   81128篇
  1986年   77760篇
  1985年   75726篇
  1984年   64546篇
  1983年   57611篇
  1982年   47278篇
  1981年   44064篇
  1980年   41630篇
  1979年   57200篇
  1978年   46891篇
  1977年   41745篇
  1976年   38308篇
  1975年   39000篇
  1974年   43142篇
  1973年   41778篇
  1972年   39719篇
  1971年   36733篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Using hierarchical cluster analysis, applied to 47 cases of Guillain-Barre Syndrome (GBS) incident in South-West Stockholm (SWS) during the period from January 1973 to June 1992, we identified three major clinicoepidemiological subgroups. The first subgroup, 25.5% of the cases (26.7 ± 6.7 years), recorded a peak incidence at ages 20–29 years and presented significant differences from other subgroups, a high proportion of cases with onset at low age preceded by respiratory infection (83.3%) and with normal motor conduction velocity (50.0%). Also found, were less affected biological parameters, a rapidly progressive course and independence in gait at one month after onset. A second subgroup, 27.7% of cases, was severely affected, clinically and functionally. It consisted predominantly of young individuals (22.7 ± 11.1 years), with a high incidence (69.2% of cases) in autumn. A third subgroup, comprising 40.47; of cases, was older (61.1 ± 11.0 years) and, in general, also severely affected. The incidence of this form appeared to be invariant with time.  相似文献   
993.
994.
SUMMARY. Samples from 1828 donations were screened for anti-HBc at seven sites in the UK using kits supplied by 10 manufacturers. Only 10 (0.55%) donations were considered to have true anti-HBc reactivity and these were detected by all 10 kits. Additional markers of HBV infection were found in nine of these 10 donations. Additional reactives were found by all kits, the number ranging from 1 to 43.
In the four more specific kits, the 10 true reactives were clearly distinguished from the 'false reactives' by the strength of the reaction. It is concluded that the reliance on a single ELISA test for anti-HBc diagnosis is unwise. The use of a second test known to be more specific than the screening ELISA is recommended.  相似文献   
995.
In the present study, we examined the effect of CsA on the in vitro production of Ig and on the in vitro production of molecules known to have B-cell growth and differentiation activities, such as IL-6 and sCD23. For the purpose of this study, we developed an experimental In vitro system closely resembling an In vivo model of ongoing B-cell activation. Pre-activated B cells proliferated and produced IgM optimally when they were re-cultured in the presence of IL-2/IL-6. CsA down-regulated the IL-2/IL-6-induced proliferative responses of pre activated B cells by at least 50%., but it up-regulated IgM production in the same experiments. This up regulating effect was not cytokine-related since it was also seen when cells were re-cultured in the absence of any cytokines. Optimal release of sCD23 was observed when SAC-pre-activated B cells were re cultured in the presence of IL-4 or IL-4 plus IL-2 and CsA up-regulated significantly the release of this molecule in these cultures. Finally, CsA was shown to inhibit PHA-induced cell proliferation of PBMC and to up-rcgulate IL-6 production in the same cultures. We conclude that CsA can amplify in vitro both the production of Ig and the release of sCD23 by pre activated B cells. This finding, in combination with the CsA-induced up-regulation of lectin-induced IL-6 production, may have clinical implications in disease states with an ongoing immune activation, where prolonged administration of CsA might be anticipated.  相似文献   
996.
997.
Summary Squamous cell carcinoma of the head and neck is a disease predominantly of males and is due to a variety of known environmental irritants, notably cigarette smoke. Dietary, viral and immunological factors may also be relevant. Head and neck squamous cancers express epidermal growth factor receptors and some show weak levels of oestrogen receptor activity, but a reliable serum marker of tumour burden remains to be identified. The prognosis is found to be less favourable in females, in those with advanced T stage, in association with multiple node involvement, especially where extracapsular spread is present and where the T4/T8 ratio is elevated. Administration of heterologous blood during therapy may also have an adverse effect on prognosis. Interested clinicians must remember that most cases are preventable. Correspondence to: A.G.D. Maran  相似文献   
998.
Data on 232 members of a single pedigree, descended from two pairs of original parents, were made available to the participants of Genetic Analysis Workshop 8 (GAW8). In addition to information concerning age and sex, measurements for 10 quantitative traits and genotypes at 22 polymorphic marker loci were also provided for a subset of 193 of these family members. © 1993 Wiley-Liss, Inc.  相似文献   
999.
1000.
Cultured keratinocytes were used as allografts on burn wounds in two patients. In both patients successful covering of the wounds was obtained. DNA fingerprinting of the epidermis covering the wounds 21 days later showed that the cultured keratinocytes were replaced by the patients' cells.  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