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   199968篇
  免费   4288篇
  国内免费   505篇
耳鼻咽喉   2843篇
儿科学   7484篇
妇产科学   5870篇
基础医学   25709篇
口腔科学   5798篇
临床医学   15424篇
内科学   36664篇
皮肤病学   4878篇
神经病学   11885篇
特种医学   10905篇
外国民族医学   97篇
外科学   30483篇
综合类   1106篇
一般理论   1篇
预防医学   16331篇
眼科学   4312篇
药学   13658篇
  2篇
中国医学   149篇
肿瘤学   11162篇
  2018年   3650篇
  2017年   3982篇
  2016年   3289篇
  2015年   5000篇
  2014年   4465篇
  2013年   3616篇
  2012年   10142篇
  2011年   5080篇
  2010年   2378篇
  2009年   4008篇
  2008年   2348篇
  2007年   3154篇
  2006年   3393篇
  2005年   11516篇
  2004年   12988篇
  2003年   8577篇
  2002年   3828篇
  2001年   4378篇
  2000年   1719篇
  1999年   5895篇
  1998年   608篇
  1995年   447篇
  1992年   6891篇
  1991年   7129篇
  1990年   7365篇
  1989年   6981篇
  1988年   6497篇
  1987年   6257篇
  1986年   5972篇
  1985年   5251篇
  1984年   3597篇
  1983年   2923篇
  1982年   1013篇
  1981年   776篇
  1980年   847篇
  1979年   3836篇
  1978年   2371篇
  1977年   1787篇
  1976年   1565篇
  1975年   2483篇
  1974年   3111篇
  1973年   2742篇
  1972年   2759篇
  1971年   2743篇
  1970年   2557篇
  1969年   2468篇
  1968年   2240篇
  1967年   2165篇
  1966年   1898篇
  1965年   1131篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
171.
172.
The efficiency of the Racal Airstream helmet respirator in improving peak expiratory flow rates (PEFR) and symptoms (dyspnea, wheezing, and cough) in aluminum potroom workers with respiratory complaints was assessed in 19 workers. Peak expiratory flow readings and symptom recording from a 2-week working period with use of the respirator were compared with a period when the 3M 9906 disposable mask was used. The study was designed as a randomized, parallel, cross-over study with five or six daily measurements of PEFR and daily symptom recording. A significant number of workers (15) had a higher mean peak flow in the helmet period than in the nonhelmet period (p less than 0.01); symptoms did not improve significantly in the helmet period. Objective evidence of respiratory protection was observed for the group of workers as a whole, but the effect on symptoms as well as individual effect on peak flow was minor in the majority of the workers.  相似文献   
173.
Serum digoxin-like factor was detected in infants of diabetic mothers who were insulin-dependent or diet controlled. No statistical difference was found between the serum digoxin-like factor levels of the infants of diabetic mothers and the controls.  相似文献   
174.
The question of the necessity of in-patient facilities of the area of (child and) adolescent neuropsychiatry is to be discussed further. The extremely optimistic views on this question of approximately 20 years ago cannot be maintained for the examined area and the examination time. In the LNKH Valduna/Vorarlberg, an establishment that was intended exclusively for adults until 1987, from 1980-1984 (evaluated in detail) and from 1984-1987 a further 60 minors were admitted. The exact evaluation shows that the conspicuousnesses of behaviour of a main group was so clear each time that it could not be treated elsewhere and certainly not in outpatient facilities. In the examined group the amount of patients with behaviour and socialization disorders outweighed by far the psychoses, also a high percentage of patients was multi morbid and/or had multiple handicaps. The resulting conclusion seems to us to be the necessity of setting-up a specific in-patients treatment unit for this group of patients with sufficient infrastructure.  相似文献   
175.
176.
Surgically-obtained tissue specimens from 41 patients with ventricular aneurysm were studied electron microscopically. The tissue from the resected aneurysms showed substantially varied morphological differences. In some, there were extensive regions of scar containing increased fibrotic material and few cells, in others there were also larger contiguous regions of myocardium with an essentially normal appearance. In the preserved myocardial regions, the cardiac cells showed moderate hypertrophy. There was an increase in contractile substance in parallel with an increase in mitochondria and enlargement of the nucleus with frequent waves and invaginations in the cell membrane. The cells at the marginal regions between fibrous tissue and preserved myocardium were frequently isolated from adjacent cells. In particular, when the isolated cells were completely surrounded by fibrous tissue, clear degeneration was apparent. These cells showed mainly a fibrillolysis with dissolution of the cross-bands and loss of the entire contractile apparatus. In compensation, occasionally there was proliferation of other cell structures, especially the free sarcoplasmatic reticulum. The hypertrophy of the still intact myocardial cells is considered compensatory for the infarct-incurred loss of tissue. The degenerative appearance is mainly attributable to fibrous tissue invasion. The diminished oxygen supply, compromised or abolished impulse conduction, loss of function and passive stretch during systole may be regarded as causes of the degeneration.  相似文献   
177.
A prospective study was performed on seven male and eight female patients with normal hepatobiliary findings to investigate the effect of 20 mg nifedipine on cholecystokinin-induced gallbladder contraction. Each patient received 1 IDU (Ivy dog unit) cholecystokinin per kg body weight intravenously on two consecutive days, with additional administration of 20 mg nifedipine sublingually on the second day. Gallbladder volumes were assessed by ultrasonography over a period of 25 minutes. Cholecystokinin induced a maximal reduction in the mean initial volume of 56.8 +/- 3.6%. After nifedipine, this volume change was significantly reduced to 30.9 +/- 5.1% (p less than 0.001). Thus our data suggest for the first time that the calcium-channel-blocking agent nifedipine can have an effect on human gallbladder kinetics.  相似文献   
178.
Effect of respiratory training with a mouth-nose-mask in tetraplegics   总被引:1,自引:0,他引:1  
Ten tetraplegics, 8 males and 2 females, with a median age of 32 years participated in a scheduled 6 weeks training programme with a respiratory muscle training mouth-nose-mask (RMT-mask) with a fixed expiratory and an increasing inspiratory resistance set by the tetraplegic in accordance to his/her increasing ability during the training period. During the 6 weeks the tetraplegics required to use the RMT-mask for 15 minutes three times a day. Before and after each training session they measured peak flow (PEF). Lung volumes, ventilatory and diffusion capacity were measured before and after the 6 weeks training period. The training resulted only in a significant change in the PEF, which increased with 11% from 371 l/min before to 412 l/min in average after the 6 weeks of training (p less than 0.025). This statistically significant increase was confirmed by the measurements of PEF performed by the tetraplegics themselves during the training period. In addition there was an increase in PEF from before to immediately after each 15 minutes training session, this trend reached statistically significance (p less than 0.025) in the third '2 weeks period'. These results might indicate a possibility of improving the tetraplegics ability to cough by use of a simple RMT-mask, which in turn might prevent certain lung complications including pneumonia, and atelectasia.  相似文献   
179.
180.
In the operative treatment of appendicitis the so called negative appendectomy is an important issue because of its increased morbidity. From the hypothesis that the intestinal diamine oxidase activity is a suitable marker of mucosal integrity, the distribution pattern of the enzyme in appendices histologically classified as inflamed or not inflamed was studied. Histologically apparent inflammation of the appendix was connected with a significant reduction of diamine oxidase activity. The determination of this enzymic activity may be a simple and sensitive test for mucosal inflammation of the appendix even at a very early state. This could reduce the rate of negative appendectomies and influence thereby risk-cost-benefit calculations.  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