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   527146篇
  免费   28225篇
  国内免费   820篇
耳鼻咽喉   7209篇
儿科学   17389篇
妇产科学   14884篇
基础医学   78082篇
口腔科学   13087篇
临床医学   42516篇
内科学   106506篇
皮肤病学   12367篇
神经病学   41737篇
特种医学   18472篇
外国民族医学   142篇
外科学   75294篇
综合类   8729篇
现状与发展   1篇
一般理论   224篇
预防医学   41046篇
眼科学   11532篇
药学   37174篇
中国医学   1465篇
肿瘤学   28335篇
  2021年   5672篇
  2020年   3432篇
  2019年   6098篇
  2018年   11007篇
  2017年   7567篇
  2016年   7966篇
  2015年   9061篇
  2014年   10319篇
  2013年   16474篇
  2012年   25082篇
  2011年   25408篇
  2010年   14128篇
  2009年   11473篇
  2008年   22430篇
  2007年   24159篇
  2006年   22910篇
  2005年   22297篇
  2004年   21167篇
  2003年   19598篇
  2002年   18548篇
  2001年   18980篇
  2000年   19473篇
  1999年   16546篇
  1998年   3889篇
  1997年   3513篇
  1996年   3322篇
  1995年   3174篇
  1992年   11292篇
  1991年   11150篇
  1990年   10815篇
  1989年   10414篇
  1988年   9540篇
  1987年   9148篇
  1986年   8672篇
  1985年   8278篇
  1984年   6101篇
  1983年   5255篇
  1982年   3141篇
  1979年   5590篇
  1978年   4052篇
  1977年   3496篇
  1976年   3132篇
  1975年   3601篇
  1974年   4299篇
  1973年   4339篇
  1972年   4007篇
  1971年   3826篇
  1970年   3672篇
  1969年   3450篇
  1968年   3297篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
142.
After admission to hospital for bed rest, 200 women with multiple pregnancies were randomly allocated to receive either 4 mg of salbutamol orally five times daily, or to receive no drug. After an average of 6 weeks treatment, no difference between the experimental groups could be detected with respect to duration of gestation, birthweight or any other of the outcomes of pregnancy observed.  相似文献   
143.
An endoscopic endonasal approach was performed to remove an intra-suprasellar Rathke's cleft cyst. Rathke's cleft cyst are benign lesions, rarely diagnosed because they are often asymptomatic. To the best of our knowledge, at least 475 cases of Rathke's cleft cysts have been reported. They seem to arise from remnants of Rathke's pouch, an invagination of the stomodeum. A 52-year-old woman, complaining of bilateral frontal headaches, was operated on by using an endoscopic endonasal approach, for an intra-suprasellar tumor. The pre-operative diagnosis was non-functioning pituitary adenoma. Intra-operatively a creamy-coloured viscous tissue was found. After the removal of the cyst contents and of the capsule, the suprasellar structures were seen well. The chiasmatic cistern, the chiasm, the pituitary stalk and the pituitary gland were visualized with 0 and 30 degree endoscopes. The pathological findings showed a well-differentiated cuboidal epithelium. The diagnosis was Rathke's cleft cyst. No post-operative complications were observed. The endoscopic technique was particularly suitable in this case, both for the Rathke's cleft features and for an excellent outcome. The Rathke's cleft cyst was easily removed by suction and the cyst wall was entirely removed with curettes and pituitary punches. The hypophysis was distinguished from the cyst and was preserved. The surgical manoeuvres were all done under direct visual control. The absence of nasal packing and of breathing difficulties made comfortable the post-operative outcome. Thus, the endoscopic endonasal approach can be considered the favourite technique in case of either intra- and/or suprasellar Rathke's cleft cysts.  相似文献   
144.
We have recently reported that ligation of the CD44 cell surface antigen with A3D8 monoclonal antibody (mAb) triggers incomplete differentiation and apoptosis of the acute promyelocytic leukemia (APL)-derived NB4 cells. The present study characterizes the mechanisms underlying the apoptotic effect of A3D8 in NB4 cells. We show that A3D8 induces activation of both initiator caspase-8 and -9 and effector caspase-3 and -7 but only inhibition of caspase-3/7 and caspase-8 reduces A3D8-induced apoptosis. Moreover, A3D8 induces mitochondrial alterations (decrease in mitochondrial membrane potential DeltaPsi m and cytochrome c release), which are reduced by caspase-8 inhibitor, suggesting that caspase-8 is primarily involved in A3D8-induced apoptosis of NB4 cells. However, the apoptotic process is independent of TNF-family death receptor signalling. Interestingly, the general serine protease inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride (AEBSF) decreases A3D8-induced apoptosis and when combined with general caspase inhibitor displays an additive effect resulting in complete prevention of apoptosis. These results suggest that both caspase-dependent and serine protease-dependent pathways contribute to A3D8-induced apoptosis. Finally, A3D8 induces apoptosis in all-trans-retinoic acid-resistant NB4-derived cells and in APL primary blasts, characterizing the A3D8 anti-CD44 mAb as a novel class of apoptosis-inducing agent in APL.  相似文献   
145.
146.
147.
148.
Sex and racial predilection, social history, and histology were analyzed in a biopsy-proven adenocarcinoma of the lower esophagus/esophagogastric junction collected over a 5-year period in two teaching institutions with different patient populations. Adenocarcinoma occurred in 11% of patients with biopsy-proven esophageal cancer. The disease occurred only in males at one center, and in a 7:1 ratio of males to females at the other center. Clear racial predilection was seen, since 12 of 13 patients with adenocarcinoma of the esophagus were white, whereas less than 20% of patients with squamous carcinoma of the esophagus were white. The finding of Barrett's epithelium in eight of the 13 cases strongly supports the theory that in white males, Barrett's epithelium is a precursor lesion of adenocarcinoma of the esophagus/esophagogastric junction.  相似文献   
149.
The permeability of human skin to benzene, ethylene glycol, formaldehyde, and n-hexane was studied using excised skin in a flow-through diffusion cell. The rate of resorption was determined by measuring the amount of substance found in the receptor fluid beneath the skin at steady-state. The rates of resorption (microgram X cm-2 X hr-1) were: benzene 99. ethylene glycol 118, formaldehyde from a concentrated solution of formalin 319, formaldehyde from a solution of 10% formalin in phosphate buffer 16.7, and n-hexane 0.83. The amount of substance in the skin at steady-state and after 0.5 hr of exposure was also determined. For all substances, the sum of the amount in the receptor medium and in the skin at steady-state, were larger than the amount obtained by multiplying the resorption rate by the time of exposure. For benzene, ethylene glycol and n-hexane the amount absorbed during the first half-hour of exposure was considerable larger than the amount resorbed during a same unit of time at steady-state. These data call attention to the fact that the absorption rate is higher before steady state is attained.  相似文献   
150.
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