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   938052篇
  免费   66636篇
  国内免费   1367篇
耳鼻咽喉   13037篇
儿科学   24536篇
妇产科学   23401篇
基础医学   133674篇
口腔科学   28342篇
临床医学   81280篇
内科学   184415篇
皮肤病学   19285篇
神经病学   72751篇
特种医学   37417篇
外国民族医学   79篇
外科学   152905篇
综合类   18104篇
现状与发展   1篇
一般理论   238篇
预防医学   62136篇
眼科学   21408篇
药学   72878篇
  3篇
中国医学   2164篇
肿瘤学   58001篇
  2018年   9096篇
  2017年   7134篇
  2016年   7865篇
  2015年   8978篇
  2014年   12143篇
  2013年   17720篇
  2012年   24389篇
  2011年   25449篇
  2010年   15031篇
  2009年   14501篇
  2008年   24959篇
  2007年   26037篇
  2006年   26819篇
  2005年   25728篇
  2004年   24849篇
  2003年   23840篇
  2002年   23365篇
  2001年   54879篇
  2000年   56687篇
  1999年   47071篇
  1998年   10795篇
  1997年   9529篇
  1996年   9643篇
  1995年   8965篇
  1994年   8323篇
  1993年   7627篇
  1992年   35575篇
  1991年   33979篇
  1990年   32833篇
  1989年   31944篇
  1988年   29058篇
  1987年   28305篇
  1986年   26344篇
  1985年   25203篇
  1984年   17884篇
  1983年   15190篇
  1982年   7834篇
  1981年   6803篇
  1979年   15830篇
  1978年   10629篇
  1977年   9077篇
  1976年   7883篇
  1975年   8642篇
  1974年   10500篇
  1973年   9888篇
  1972年   9385篇
  1971年   8874篇
  1970年   8457篇
  1969年   7943篇
  1968年   7220篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
Published data devoted to making and characterization of the properties of polymeric wound dressings with proteolytic action are reviewed. These data are indicative of individual dependence of the physicochemical properties, activity, and stability of each particular enzyme on the type of polymer matrix and the method of immobilization. In order to obtain wound dressings, which are active in physiological medium and retain their activity upon sterilization, it is necessary to optimize the composition and characteristics of a polymer matrix and the enzyme included into its structure. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 8, pp. 24–28, August, 2006.  相似文献   
114.
115.
In chronic myeloid leukaemia, CD34(+) stem/progenitor cells appear resistant to imatinib mesylate (IM) in vitro and in vivo. To investigate the underlying mechanism(s) of IM resistance, it is essential to quantify Bcr-Abl kinase status at the stem cell level. We developed a flow cytometry method to measure CrkL phosphorylation (P-CrkL) in samples with <10(4) cells. The method was first validated in wild-type (K562) and mutant (BAF3) BCR-ABL(+) as well as BCR-ABL(-) (HL60) cell lines. In response to increasing IM concentration, there was a linear reduction in P-CrkL, which was Bcr-Abl specific and correlated with known resistance. The results were comparable to those from Western blotting. The method also proved to be reproducible with small samples of normal and Ph(+) CD34(+) cells and was able to discriminate between Ph(-), sensitive and resistant Ph(+) cells. This assay should now enable investigators to unravel the mechanism(s) of IM resistance in stem cells.  相似文献   
116.
Accurate assessment of the amount and intensity of physical activity in daily life is considered very important due to the close relationship between physical activity level, health, disability and mortality. For this reason, assessment of physical activity in daily life has gained interest in recent years, especially in sedentary populations, such as patients with chronic obstructive pulmonary disease (COPD). The present article aims to compare and discuss the two kinds of instruments more commonly used to quantify the amount of physical activity performed by COPD patients in daily life: subjective methods (questionnaires, diaries) and motion sensors (electronic or mechanical methods). Their characteristics are summarised and evidence of their validity, reliability and sensitivity is discussed, when available. Subjective methods have practical value mainly in providing the patients' view on their performance in activities of daily living and functional status. However, care must be taken when using subjective methods to accurately quantify the amount of daily physical activity performed. More accurate information is likely to be available with motion sensors rather than questionnaires. The selection of which motion sensor to use for quantification of physical activity in daily life should depend mainly on the purpose of its use.  相似文献   
117.
The aim of the current study was to investigate whether alterations in N-terminal pro brain natriuretic peptide (NT-proBNP) reflect changes in right ventricular structure and function in pulmonary hypertension patients during treatment. The study consisted of 30 pulmonary hypertension patients; 15 newly diagnosed and 15 on long-term treatment. NT-proBNP, right heart catheterisation and cardiac magnetic resonance imaging measurements were performed, at baseline and follow-up. There were no significant differences between newly diagnosed patients and those on treatment at baseline or follow-up with respect to NT-proBNP, haemodynamics and right ventricular parameters. Relative changes in NT-proBNP during treatment were correlated to the relative changes in right ventricular end-diastolic volume index (r = 0.59), right ventricular mass index (r = 0.62) and right ventricular ejection fraction (r = -0.81). N-terminal pro brain natriuretic peptide measurements reflect changes in magnetic resonance imaging-measured right ventricular structure and function in pulmonary hypertension patients. An increase in N-terminal pro brain natriuretic peptide over time reflects right ventricular dilatation concomitant to hypertrophy and deterioration of systolic function.  相似文献   
118.
119.
BACKGROUND AND OBJECTIVES: In 1999, our institution began a kidney transplant program with collaboration between the departments of General Surgery/Transplantation and Urology. From the onset, donor nephrectomies were performed laparoscopically and are currently the domain of Urology, which had no prior laparoscopic experience before this undertaking. We reviewed our experience. METHODS: A database of our experience was kept prospectively from June 1999 to November 2004. Records of both donors and recipients were reviewed. Special attention was directed toward our changes in technique and their relationship to outcomes, with emphasis on graft extraction and overall complication rates. RESULTS: We reviewed the records of 205 consecutive procedures. We report excellent donor outcomes, including mean operative time (112 minutes), estimated blood loss (120 mL), and length of stay (2.3 days). Complication (14.1%) and open conversion (1.5%) rates were low. For the recipients, early (98.0%) and 1-year (94.7%) graft survival, and ureteral ischemia (2.4%) rates were also appropriate with contemporary experience. CONCLUSIONS: We report our results on laparoscopic donor nephrectomy in a de novo renal transplant program. Because of this experience, we have ventured into other horizons of urologic laparoscopy and currently produce enough volume to support a laparoscopic fellowship. We feel that a productive donor nephrectomy program can enhance urologic laparoscopic programs and should be taken advantage of when available.  相似文献   
120.
最近提出的关于额叶功能的理论认为前额叶皮质,尤其是其背外侧面在确定适合一项特殊任务的一系列反应中起重要作用,并在选择中使上述反应发生偏差。这些活动事实上是为任何类型的非常规任务而执行,而不考虑内容的差别。本研究旨在通过一项解决“洞察力”问题的测试任务(即火柴杆算术作业),来验证Frith“塑造反应空间”假说的预测效力。从Knoblich等人对健康人不能解决火柴杆问题的解释和Frith关于额叶背外侧皮质作用的理论,作者推导出与直觉相左的预测,即对这些相对复杂的任务,外侧额叶皮质局部损伤的患者可能比1组健康受试者完成得更好。要求35例经CT或MRI扫描证实为单个局部脑损伤的患者(年龄为26—65岁)和23例健康受试者(年龄为34—62岁)完成火柴杆作业。研究结果似乎与理论上的预测相一致,虽然仅有43%的健康受试者能解决最困难的火柴杆问题(“C类”),但是却有82%的额叶外侧损伤患者完成了类似问题(Fisher精确概率检验,P〈0.05)。总之,对Frith和Knoblich等人理论的结合进行了确证。  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