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   379774篇
  免费   24195篇
  国内免费   2817篇
耳鼻咽喉   5187篇
儿科学   8235篇
妇产科学   10079篇
基础医学   53176篇
口腔科学   11778篇
临床医学   30133篇
内科学   78466篇
皮肤病学   8601篇
神经病学   27316篇
特种医学   13922篇
外国民族医学   82篇
外科学   60650篇
综合类   9955篇
现状与发展   1篇
一般理论   64篇
预防医学   17430篇
眼科学   9508篇
药学   31064篇
  1篇
中国医学   2192篇
肿瘤学   28946篇
  2021年   2636篇
  2019年   2738篇
  2018年   4526篇
  2017年   3443篇
  2016年   3534篇
  2015年   4038篇
  2014年   5722篇
  2013年   7406篇
  2012年   10047篇
  2011年   10242篇
  2010年   6203篇
  2009年   5858篇
  2008年   9478篇
  2007年   10310篇
  2006年   10240篇
  2005年   9305篇
  2004年   8821篇
  2003年   8554篇
  2002年   8213篇
  2001年   28257篇
  2000年   28789篇
  1999年   23662篇
  1998年   5169篇
  1997年   4259篇
  1996年   3838篇
  1995年   3488篇
  1994年   3108篇
  1993年   2844篇
  1992年   16064篇
  1991年   14827篇
  1990年   14170篇
  1989年   13975篇
  1988年   12595篇
  1987年   12072篇
  1986年   11123篇
  1985年   10338篇
  1984年   6924篇
  1983年   5607篇
  1982年   2718篇
  1979年   5482篇
  1978年   3348篇
  1977年   2976篇
  1975年   2644篇
  1974年   3067篇
  1973年   2866篇
  1972年   2833篇
  1971年   2773篇
  1970年   2513篇
  1969年   2548篇
  1968年   2252篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
BACKGROUND: Gastric cancer (GC) is the leading cause of cancer deaths in China. Our study prospectively evaluated the impact of repeated endoscopic screens on GC mortality in a high-risk population in China. METHODS: Between 1989 and 1999, a population-based gastroscopic screening was conducted in 4,394 residents of Linqu County, China, a region with the highest rates of GC worldwide. Residents ages 35 to 64 years received initial gastroscopies with biopsies in 1989. Repeated endoscopies were performed in 1994 and 1999. Cancer occurrences and deaths were actively monitored throughout the entire period until July 2000. Mortality from GC was compared with expected values based on mortality rates obtained for Linqu in the 1990-1992 Chinese Cancer Mortality Survey. RESULTS: Between March 1989 and July 2000, 39,303 person-years were accumulated; 85 new GCs occurred, 29 (34.5%) were in early stage. Fifty-eight cases (68%) were identified at one of the screens. The number of observed deaths from GC (37) was close to the expected (36.8). The standardized mortality ratio was 1.01 (95% CI 0.72-1.37) for the entire cohort, 1.13 (95% CI 0.77-1.57) for males, and 0.65 (95% CI 0.26-1.32) for females. CONCLUSIONS: Despite high population coverage with repeated screens, no reduction in GC mortality was observed in this high-risk population in China.  相似文献   
72.
A nationwide survey of transient hyperammonemia in newborns was carried out in Japan. A total of 18 patients, consisting of 12 male and 6 female infants, were reported from 11 facilities. These neonates exhibited hyperammonemia with plasma ammonia levels in the range from 124 to 6256 micrograms/dl. Four newborn infants of the 18 died in the neonatal period, and an additional one died in the early infancy. Among the 13 infants who were alive at the time of this survey, 6 had neurological sequelae, including mental retardation, spastic quadriplegia and epilepsy. The multivariate analysis revealed that the Apgar score at 1 minute, peak plasma ammonia concentration, birth weight and sex were significant factors affecting the prognosis of life.  相似文献   
73.
One of the consequences of increased intracellular calcium in response to a variety of physiological stimuli is the calcium activation of cytosolic proteases. Unlike lysosomal proteases with broad specificity, these calcium-activated neutral proteases show limited proteolysis of a restricted set of substrate proteins suggesting they may play a regulatory role in cellular physiology. In this study we show that the neural cell adhesion molecules NCAM-180 and N-cadherin are substrates for such endogenous calcium-activated neutral proteases. In contrast, a third neural cell adhesion molecule G4/L1 was not susceptible to calcium-activated proteolysis. The threshold for activation of NCAM and N-cadherin proteolysis is in the micromolar range of calcium suggesting that NCAM and N-cadherin are substrates for a mu-type calpain (calpain I). The site recognized by this protease is within intracellular domains of NCAM-180 and N-cadherin which are important for their interaction with cytoskeletal components. These results suggest that calcium-activated proteolysis at these sites in vivo could disrupt the linkage between extracellular ligand binding to these adhesion molecules and the normal intracellular effectors of such extracellular binding events.  相似文献   
74.
We report an 80-year-old Japanese male with four primary malignant tumors: malignant melanoma, prostatic cancer, malignant lymphoma, and renal cell carcinoma, which occurred in that respective order. The combination of malignant melanoma and malignant lymphoma is rare. The patient was treated with BCG after an operation for malignant melanoma. He was also treated with cobalt 60 irradiation after an operation for prostatic cancer. We also discuss other reports of multiple malignant tumors and suggest some possible causes of this patient's primary malignant tumors.  相似文献   
75.
76.
77.
78.
With the increased use of indwelling central venous catheters, increasing numbers of cases of Rhodotorula fungemia have been observed in patients with neoplasia and neutropenia. In most patients with catheter-related Rhodotorula fungemia, the condition has been treated with broadspectrum antibiotics. We report two cases of central venous catheter-related Rhodotorula rubra fungemia that occurred in patients with acute myeloblastic leukemia. Both patients were in a state of neutropenia. One patient was treated with amphotericin B and his central venous catheter was removed, but he died of Klebsiella pneumoniae bacteremia. The other patient was treated with amphotericin B and discharged, with a central venous catheter, after recovery from neutropenia. Although the management of catheter-related Rhodotorula fungemia infections remains controversial, resolution of the underlying disease is more important than catheter removal for recovery from Rhodotorula rubra fungemia. Received: August 22, 2001 / Accepted: October 8, 2001  相似文献   
79.
80.
In rodents, chronic estrogenization has been shown to induce degeneration of dendrites and myelin figures in the hypothalamic arcuate nucleus adjacent to peroxidase-positive astrocyte processes. Because in this brain region estradiol is metabolized to 2-hydroxyestradiol (catecholestrogen), we hypothesized that the latter may be oxidized by the astrocytic peroxidase activity to cytotoxic ortho-semiquinones as occurs in peripheral tissues. Cysteamine induces nonenzymatic peroxidase activity in cultured astroglia identical to that observed in vivo. Using electron spin resonance, we demonstrate robust peroxidase-catalyzed oxidation of 2-hydroxyestradiol and dopamine by cysteamine-pretreated astrocyte cultures relative to untreated controls. These results implicate the peroxidase-positive astrocytes in the pathogenesis of estradiol-related hypothalamic damage, parkinsonism, and other free-radical-related neurologic disorders.  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