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   18162篇
  免费   1754篇
  国内免费   35篇
耳鼻咽喉   147篇
儿科学   641篇
妇产科学   1179篇
基础医学   1969篇
口腔科学   156篇
临床医学   5374篇
内科学   2792篇
皮肤病学   253篇
神经病学   1392篇
特种医学   315篇
外科学   1383篇
综合类   122篇
一般理论   17篇
预防医学   2089篇
眼科学   124篇
药学   906篇
中国医学   12篇
肿瘤学   1080篇
  2023年   226篇
  2022年   109篇
  2021年   270篇
  2020年   257篇
  2019年   287篇
  2018年   476篇
  2017年   397篇
  2016年   520篇
  2015年   502篇
  2014年   676篇
  2013年   990篇
  2012年   1103篇
  2011年   1252篇
  2010年   751篇
  2009年   845篇
  2008年   1209篇
  2007年   1224篇
  2006年   1185篇
  2005年   1127篇
  2004年   1081篇
  2003年   989篇
  2002年   1003篇
  2001年   220篇
  2000年   140篇
  1999年   243篇
  1998年   329篇
  1997年   253篇
  1996年   239篇
  1995年   207篇
  1994年   175篇
  1993年   149篇
  1992年   136篇
  1991年   123篇
  1990年   141篇
  1989年   92篇
  1988年   91篇
  1987年   76篇
  1986年   74篇
  1985年   84篇
  1984年   68篇
  1983年   82篇
  1982年   91篇
  1981年   78篇
  1980年   62篇
  1979年   35篇
  1978年   51篇
  1977年   35篇
  1976年   37篇
  1975年   24篇
  1974年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
We have examined the actions of vasoactive intestinal peptide (VIP) and certain other known immune modulators on a nuclear pool(s) of protein kinase C (PKC) in isolated rat splenocyte nuclei. Rat splenocyte nuclei pure by enzymatic and electron microscope criteria demonstrated a time- and concentration-dependent activation of nuclear PKC (nPKC) by VIP. A biphasic pattern of three bell-shaped curves was observed with peak phosphorylation at 10−15, 10−9 and 10−6M VIP. The phosphorylation of endogenous nuclear substrates was characterized as a PKC-mediated event by use of three known PKC inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), sphingosine, and staurosporine, which produced similar phosphate incorporation measurements. Also, this activity was blocked with the addition of a monoclonal antibody to PKC. Inhibitors of the ability of VIP to activate nPKC included somatostatin, 8-bromo-cAMP, peripheral benzodiazepine receptor modulators, and the PKC inhibitors, sphingosine and staurosporine. These data have direct relevance to our knowledge of cell-mediated immunity.  相似文献   
72.
73.
OBJECTIVE: To examine factors that affect pelvic muscle response to 12 weeks of pelvic muscle exercise. DESIGN: Repeated measures design in which intravaginal pressures during pelvic muscle contractions were recorded at baseline and after four exercise levels. SETTING: College of Nursing research site in Gainesville, Florida. PARTICIPANTS: Eighty-five parous, community-dwelling women, aged 35-78 years and without incontinence as a primary concern. INTERVENTIONS: A 12-week graded program of regular (three times per week, every other day) pelvic muscle exercise at home. MAIN OUTCOME MEASURES: The hypotheses were that younger age, lower parity, higher baseline intravaginal pressures, and adherence to the pelvic muscle exercise program each would result in significant improvement in maximum intravaginal pressures. RESULTS: The only factor showing significance in predicting a successful outcome was age (t = -2.29, df = 41, one-tail probability = .0136). CONCLUSIONS: Regular, graded exercise over several weeks is needed to build pelvic muscles, and some women who exercise do not improve. Although the reasons for not improving are unclear, age is a significant factor.  相似文献   
74.
The following article reports on the results of service needs assessments of a cohort of youths released from a state psychiatric facility as perceived by service providers and families/caregivers. Families as well as service providers consistently agreed on three service areas of high need—psychotherapy for the child, family therapy and parent skill training. However, families perceived a need for a number of other services that are not traditionally provided by the mental health system such as after school recreation activities and self-help and support groups for the child. The discrepancies between service providers and families' perceptions of assessed needs may lead to families dropping out of service due to the unresponsiveness of the services in meeting their perceived needs. Steps that service providers need to take to be more responsive to the needs of families are discussed.This study was funded by a grant from the Office of Program Evaluation and Research, Ohio Department of Mental Health.  相似文献   
75.
76.
77.
Metastasis (the spread of cancer from a primary tumor to secondary organs) is responsible for most cancer deaths. The ability to follow the fate of a population of tumor cells over time in an experimental animal would provide a powerful new way to monitor the metastatic process. Here we describe a magnetic resonance imaging (MRI) technique that permits the tracking of breast cancer cells in a mouse model of brain metastasis at the single-cell level. Cancer cells that were injected into the left ventricle of the mouse heart and then delivered to the brain were detectable on MR images. This allowed the visualization of the initial delivery and distribution of cells, as well as the growth of tumors from a subset of these cells within the whole intact brain volume. The ability to follow the metastatic process from the single-cell stage through metastatic growth, and to quantify and monitor the presence of solitary undivided cells will facilitate progress in understanding the mechanisms of brain metastasis and tumor dormancy, and the development of therapeutics to treat this disease.  相似文献   
78.
BACKGROUND: In a previous investigation we reported on magnetic forces in the static magnetic field of a 1.5 Tesla MRI system. The aim of the present investigation was to assess forces on orthodontic wires in a high field strength MRI system at 3 Tesla. MATERIALS AND METHODS: Thirty-two different orthodontic wires (21 archwires, eight ligature wires and three retainer wires) were investigated in a 3 Tesla high field strength MRI system (Intera, Philips Medical Systems, Best, The Netherlands). Translational forces were measured by the deflection angle test (ASTM F2052-02), and rotational forces assessed on a 5-point qualitative scale. RESULTS AND CONCLUSION: Translational forces ranged between 43.5 mN and 136.1 mN for retainer wires and between 0.6 mN (Noninium) and 208.4 mN (Orthos Stainless Steel) for steel archwires. Translational forces were up to 53.8 times as high as gravitational forces for retainer wires and up to 54.5 times as high for steel archwires, associated with marked rotational forces for the most part. Archwires manufactured from nickel-titanium, titanium-molybdenum and cobalt-chromium and different ligature wires showed no or negligible forces in the magnetic field. Carefully ligated wires should not present a risk due to translational and rotational forces in the high field MRI system at 3 Tesla.  相似文献   
79.
80.
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