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   1281306篇
  免费   98260篇
  国内免费   1999篇
耳鼻咽喉   18451篇
儿科学   44428篇
妇产科学   35076篇
基础医学   182621篇
口腔科学   33648篇
临床医学   111496篇
内科学   258840篇
皮肤病学   28143篇
神经病学   100733篇
特种医学   51254篇
外国民族医学   660篇
外科学   196591篇
综合类   27059篇
现状与发展   1篇
一般理论   378篇
预防医学   95964篇
眼科学   27949篇
药学   94977篇
  2篇
中国医学   2428篇
肿瘤学   70866篇
  2018年   13250篇
  2017年   10048篇
  2016年   10996篇
  2015年   12494篇
  2014年   17303篇
  2013年   26357篇
  2012年   36266篇
  2011年   38299篇
  2010年   22926篇
  2009年   21914篇
  2008年   36791篇
  2007年   39382篇
  2006年   39627篇
  2005年   38581篇
  2004年   37688篇
  2003年   36571篇
  2002年   35887篇
  2001年   64015篇
  2000年   66514篇
  1999年   56424篇
  1998年   15141篇
  1997年   13764篇
  1996年   14204篇
  1995年   13464篇
  1994年   12775篇
  1993年   11797篇
  1992年   44559篇
  1991年   43470篇
  1990年   42226篇
  1989年   40115篇
  1988年   36898篇
  1987年   36237篇
  1986年   33622篇
  1985年   32281篇
  1984年   24139篇
  1983年   20268篇
  1982年   11725篇
  1981年   10691篇
  1980年   9518篇
  1979年   21342篇
  1978年   14824篇
  1977年   12532篇
  1976年   11694篇
  1975年   12624篇
  1974年   14662篇
  1973年   14117篇
  1972年   12948篇
  1971年   11730篇
  1970年   11050篇
  1969年   10024篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
As free radicals and lipid peroxidation are involved in the pathogenesis of different inflammatory diseases of the liver, the blood malondialdehyde content, the activity or quantity of free radical eliminating enzymes and the natural antioxidant, vitamin E serum level has been studied in ten patients with chronic active hepatitis and in six subjects with alcoholic liver disease. Thirty healthy volunteers served as controls. The serum malondialdehyde/thiobarbituric acid reactive substance and its concentrations increased significantly in both hepatitis groups. The superoxide dismutase content was also raised in the patients' sera. The serum glutathione peroxidase (GSH-Px) activity was decreased in both groups, while the red blood cell GSH-Px showed a significantly lower activity in the alcoholic hepatitis patients. Serum catalase activity and vitamin E levels in both types of chronic hepatitis were not significantly different from the healthy controls.  相似文献   
994.
This paper models the proximate determinants of school attendance and scores on cognitive and educational achievement tests and on school examinations of over 600 schoolchildren from the Control group of a randomized trial in Tanzania, where children in the Intervention group heavily infected with hookworm and schistosomiasis received treatment. The modeling approach used a random effects framework and incorporated the inter-relationships between school attendance and performance on various tests, controlling for children's health status, socioeconomic variables, grade level, and the educational infrastructure. The empirical results showed the importance of variables such as children's height and hemoglobin concentration for the scores, especially on educational achievement tests that are easy to implement in developing countries. Also, teacher experience and work assignments were significant predictors of the scores on educational achievement tests, and there was some evidence of multiplicative effects of children's heights and work assignments on the test scores. Lastly, some comparisons were made for changes in test scores of treated children in the Intervention group with the untreated children in the Control group.  相似文献   
995.
Brain metastasis is the most common intracranial malignancy in adults. Improvements in modern imaging techniques are detecting previously occult brain metastases, and more effective therapies are extending the survival of patients with invasive cancer who have historically died from extracranial disease before developing brain metastasis. This combination of factors along with increased life expectancy has led to the increased diagnosis of brain metastases. Conventional treatment has been whole brain radiotherapy, which can improve symptoms, but potentially results in neurocognitive deficits. Several strategies to improve the therapeutic ratio are currently under investigation to either enhance the radiation effect, thereby preventing tumor recurrence or progression as well as reducing collateral treatment-related brain injury. In this review article, we discuss new directions in the management of brain metastases, including the role of chemical modifiers, novel systemic agents, and the management and prevention of neurocognitive deficits.  相似文献   
996.
The hormonal compound with the highest cytostatic activity against MCF-7 tumor cells (human breast cancer, BC) and the lowest activity against normal cells (rat skin fibroblasts) was sought among gestagens, androstenes, and antiestrogencytostatics. It was found that antiestrogencytostatics and androstenes had the highest cytostatic activity against tumor cells whereas gestagens and antiestrogencytostatics were least active against fibroblasts. Studies of the activity of the hormonal compounds in combination with doxorubicin on the viability of MCF-7 and rat skin fibroblasts found that all investigated compounds with the exception of dehydroepiandrosterone (DHEA) intensify the cytostatic activity of doxorubicin against tumor cells, the greatest effect seen for antiestrogencytostatics. A chemoprotective effect of androstenes on normal cells was noted. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 7, pp. 3–7, July, 2007.  相似文献   
997.
998.
999.
PURPOSE: This study aims to determine the effect of loss of breast cancer metastasis suppressor 1 (BRMS1) protein expression on disease-free survival in breast cancer patients stratified by estrogen receptor (ER), progesterone receptor (PR), or HER2 status, and to determine whether loss of BRMS1 protein expression correlated with genomic copy number changes. EXPERIMENTAL DESIGN: A tissue microarray immunohistochemical analysis was done on tumors of 238 newly diagnosed breast cancer patients who underwent surgery at the Cleveland Clinic between January 1, 1995 and December 31, 1996, and a comparison was made with 5-year clinical follow-up data. Genomic copy number changes were determined by array-based comparative genomic hybridization in 47 breast cancer cases from this population and compared with BRMS1 staining. RESULTS: BRMS1 protein expression was lost in nearly 25% of cases. Patients with tumors that were PR negative (P=0.006) or HER2 positive (P=0.039) and <50 years old at diagnosis (P=0.02) were more likely to be BRMS1 negative. No overall correlation between BRMS1 staining and disease-free survival was observed. A significant correlation, however, was seen between loss of BRMS1 protein expression and reduced disease-free survival when stratified by either loss of ER (P=0.008) or PR (P=0.029) or HER2 overexpression (P=0.026). Overall, there was poor correlation between BRMS1 protein staining and copy number status. CONCLUSIONS: These data suggest a mechanistic relationship between BRMS1 expression, hormone receptor status, and HER2 growth factor. BRMS1 staining could potentially be used in patient stratification in conjunction with other prognostic markers. Further, mechanisms other than genomic deletion account for loss of BRMS1 gene expression in breast tumors.  相似文献   
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