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   36519篇
  免费   1889篇
  国内免费   194篇
耳鼻咽喉   371篇
儿科学   833篇
妇产科学   424篇
基础医学   4570篇
口腔科学   979篇
临床医学   2427篇
内科学   9873篇
皮肤病学   834篇
神经病学   2469篇
特种医学   1336篇
外科学   6563篇
综合类   163篇
一般理论   4篇
预防医学   1071篇
眼科学   427篇
药学   2465篇
中国医学   104篇
肿瘤学   3689篇
  2023年   285篇
  2022年   527篇
  2021年   886篇
  2020年   452篇
  2019年   618篇
  2018年   773篇
  2017年   701篇
  2016年   741篇
  2015年   710篇
  2014年   945篇
  2013年   1113篇
  2012年   1814篇
  2011年   1865篇
  2010年   1068篇
  2009年   910篇
  2008年   1640篇
  2007年   1795篇
  2006年   1722篇
  2005年   1795篇
  2004年   1642篇
  2003年   1543篇
  2002年   1409篇
  2001年   1183篇
  2000年   1264篇
  1999年   1095篇
  1998年   419篇
  1997年   296篇
  1996年   299篇
  1995年   275篇
  1994年   234篇
  1993年   248篇
  1992年   770篇
  1991年   705篇
  1990年   668篇
  1989年   729篇
  1988年   643篇
  1987年   600篇
  1986年   542篇
  1985年   520篇
  1984年   336篇
  1983年   283篇
  1979年   261篇
  1978年   184篇
  1977年   161篇
  1974年   154篇
  1973年   169篇
  1972年   166篇
  1971年   156篇
  1970年   155篇
  1969年   143篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Buoyancy and sedimentation of human X- and Y-bearing sperm   总被引:4,自引:0,他引:4  
The buoyant and sedimentation behaviors of human X- and Y-bearing sperm were examined in discontinuous density gradients of Nycodenz. The washed sperm placed at the bottom of the discontinuous density gradients of Nycodenz (23-50% in 3% steps) were centrifuged at 250 x g for various periods. The buoyant velocity of X-bearing sperm was faster than that of Y-bearing sperm. The sedimentation profiles of human sperm in the discontinuous density gradients of Nycodenz (4-20% in 2% steps) showed that X-bearing sperm sedimented faster than Y-bearing sperm. The separation of X- and Y-bearing sperm by means of centrifugation usually have been based on the assumption that smaller Y and larger X chromosomes might provide the difference in their apparent densities. The present results suggest that the separation cannot be due merely to a difference in their densities.  相似文献   
53.
In order to clarify the role of gastric inhibitory polypeptide (GIP) in an enteroinsular axis, 19 healthy mongrel dogs were divided into following groups: 5 normal dogs (N), 4 dogs with gastrojejunostomy (GJ), 5 dogs with duodenal fistula (D) and 5 vagotomized dogs (V). Four weeks after the operation glucose was administered orally or intraduodenally in a conscious state. In group D, glucose administration was repeated under atropine injection (A). Glucose-induced response of plasma GIP was exaggerated in all the groups compared with group N. The regression equation reported by Lauritsen and Moody was obtained in each dog from the ratio of plasma insulin to blood glucose and from plasma GIP. The slope of the regression line was elevated in group GJ and reduced in group V. However, groups D and A did not reveal any difference in the slope of the regression line compared with group N. From the present study, it might be concluded that the B-values in Lauritsen and Moody's equation indicates the sensitivity of the B cell in the pancreatic islet and that GIP secretion plays an important role in the glucose-induced insulin response even in the conditions with various surgical modifications.  相似文献   
54.
When heat-killed Propionibacterium acnes, a gram-positive anaerobe, is intravenously injected into mice followed by an intravenous injection of gram-negative lipopolysaccharide (LPS) 7 days later, most of the mice die of massive hepatic cell necrosis within 24 hours of LPS injection. Using this experimental model, acute hepatic failure was induced in mice, and the tryptophan metabolism in the liver, brain and kidney was studied. As a result, the tryptophan level was remarkably high in all three organs, and the metabolism of both the tryptamine pathway and serotonin pathway was induced. However, in the brain, the tryptamine metabolism was more induced compared to the serotonin, suggesting that the metabolites of tryptamine, may be involved in hepatic encephalopathy.  相似文献   
55.
56.
Patients on long-term hemodialysis (HD) are known to develop amyloid osteoarthropathy, evidenced as cystic radiolucencies on X-rays of the affected joints. To study the relationship between cystic radiolucencies and amyloid osteoarthropathy in 394 patients, we classified the severity of the cystic radiolucencies seen in the wrist joint on a 4-point scale and evaluated the association between lesion severity (grade) and several parameters. Biopsy was performed in 8 patients with 11 bone cysts of the wrist joint who had been operated for carpal tunnel syndrome. HD for 10 years or longer, age 50 or older and the presence of carpal tunnel syndrome were associated with severe cyst rating. There was no association between lesion grade and serum level of PTH-C, aluminum or beta 2-microglobulin (B2M). Ten of the 11 biopsied bone cysts in 8 patients with carpal tunnel syndrome demonstrated amyloid deposits which reacted with B2M. We conclude that a cystic radiolucency observed in the wrist joint of a patient undergoing HD indicates the deposition of amyloid. The cyst grade provides a useful marker for the severity of amyloid osteoarthropathy in HD patients.  相似文献   
57.
The authors examined the relationship between cerebral white matter changes and mental function, blood pressure in 39 neurologically normal aged (21 males, 18 females, mean age 75.0 years) who had no latent lesions on MRI images. The severity of cerebral white matter changes was estimated by T1 value images on MRI and was measured in the bilateral frontal lobe on an axial slice at the level of the basal ganglia and in the bilateral anterior, middle, and posterior portions on axial slices at the level of the body of the lateral ventricle. Mental function was measured by the Hasegawa's dementia rating scale (HDS) and Kohs' block design test (Kohs' test). The severity of cerebral frontal white matter changes increased significantly with age (p less than 0.05). However there was no significant correlation between the severity of cerebral white matter changes and HDS, Kohs' test. The severity of frontal white matter changes correlated with the mean arterial blood pressure (p less than 0.02). These results suggest that the severity of cerebral white matter changes is not related with mental function in the normal elderly, and that the severity of frontal white matter lesions is related with mean arterial blood pressure.  相似文献   
58.
In 195 elderly head-injured patients, Glasgow Coma Scale (GCS) scores (admission and 72 hours) and intracranial pressure (ICP) 0-12 days after injury were compared to 6 month Glasgow Outcome Scores. All patients remaining comatose at least 72 hours after injury died within 6 months. The mortality rate among patients with ICP greater than 20 mm Hg was higher both at 72 hours and at 6 months after injury. The 6 month mortality rate was 75% overall and 90% among patients with elevated ICP. This increased mortality in elderly patients with initially elevated ICP indicates that nurses and other health professionals should consider ICP as well as level of consciousness when counseling patients and families regarding the likely outcome after major head injuries.  相似文献   
59.
Protein kinase C (PKC) activity was examined in the cytosolic and particulate fractions of homogenates obtained from 12 papillary thyroid carcinomas, 12 follicular thyroid adenomas, and the adjacent normal thyroid tissue. Particulate PKC activity was elevated significantly in thyroid carcinomas compared with normal thyroid tissue (P < 0.01) and adenomas (P < 0.05). By contrast, cytosolic PKC activity of carcinomas and adenomas was lower significantly than that of normal thyroid tissue (P < 0.01). The percentage of particulate PKC activity in carcinoma and adenoma was higher than in normal thyroid tissue (carcinoma, P < 0.001; adenoma, P < 0.01). The average particulate PKC activity of carcinomas more than 3 cm in diameter was significantly lower than that of carcinomas less than or equal to 3 cm in diameter (P < 0.05). The average cytosolic PKC activity of carcinomas more than 3 cm also was lower significantly than that of smaller carcinomas (P < 0.05). These results suggest that alterations in PKC activity may be important in the development of papillary thyroid cancer.  相似文献   
60.
Summary A newly designed attachment device of the multipurpose head frame (Sugita) for Neuronavigator (Watanabe) is presented with an illustrative case of glioblastoma in an eloquent area. This has extended the usefulness of the neuronavigator for those who prefer and use the multipurpose head frame, while the requirements for keeping a stereotactic combination and the original concept of the multipurpose head frame, as well as that of the neuronavigator have been kept undisturbed.  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