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   514035篇
  免费   33359篇
  国内免费   614篇
耳鼻咽喉   6893篇
儿科学   16839篇
妇产科学   13523篇
基础医学   85045篇
口腔科学   14475篇
临床医学   44347篇
内科学   93621篇
皮肤病学   12154篇
神经病学   36182篇
特种医学   18453篇
外国民族医学   63篇
外科学   77038篇
综合类   8476篇
一般理论   118篇
预防医学   38968篇
眼科学   12141篇
药学   40543篇
中国医学   1007篇
肿瘤学   28122篇
  2018年   4931篇
  2015年   4508篇
  2014年   6059篇
  2013年   9544篇
  2012年   12866篇
  2011年   14268篇
  2010年   8299篇
  2009年   7771篇
  2008年   13693篇
  2007年   14699篇
  2006年   14937篇
  2005年   14353篇
  2004年   14048篇
  2003年   13388篇
  2002年   13269篇
  2001年   24074篇
  2000年   25088篇
  1999年   20559篇
  1998年   5426篇
  1997年   4705篇
  1996年   5046篇
  1995年   4629篇
  1994年   4320篇
  1993年   4139篇
  1992年   15727篇
  1991年   16316篇
  1990年   16423篇
  1989年   15804篇
  1988年   14578篇
  1987年   14420篇
  1986年   13599篇
  1985年   12975篇
  1984年   9629篇
  1983年   8247篇
  1982年   4560篇
  1981年   4231篇
  1979年   9419篇
  1978年   6857篇
  1977年   5772篇
  1976年   5602篇
  1975年   6396篇
  1974年   7634篇
  1973年   7131篇
  1972年   6961篇
  1971年   6685篇
  1970年   6173篇
  1969年   5888篇
  1968年   5559篇
  1967年   5013篇
  1966年   4450篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
193.
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   
194.
Pepsinogen II (PG II) is a gastric proenzyme which has previously been found in both human seminal fluid and the prostate gland. However, no regional distribution of PG II has been noted within the prostate nor has it been found in the seminal vesicle. Bouins-fixed sections of central zone, peripheral zone and seminal vesicle, taken from 10 prostates removed at radical prostatectomy or cystectomy, were exposed to antibody against PG II and stained using the A-B-C immunoperoxidase technique. Formalin-fixed tissue from autopsy prostates of four men in the third decade, and six cases with BPH nodules, were also examined for PG II activity. In nine of 10 seminal vesicles, and seven of 10 central zone samples, more than 50 per cent of the cells stained positive for PG II. By contrast, in nine of 10 peripheral zone samples staining was present in five per cent or less of the epithelial cells. Similarly, PG II activity in the four autopsy prostates occurred almost entirely within the central zone and ended abruptly at the boundary between the peripheral and central zones. BPH nodules contained no PG II activity. These findings provide the first evidence that the central and peripheral zones may serve different biological functions. Embryologically it is currently thought that the prostate is of endodermal origin and the seminal vesicle of mesodermal origin. The presence of large amounts of PG II in both the seminal vesicle and central zone lends support to the hypothesis of a common mesodermal origin for these two structures.  相似文献   
195.
Percutaneous transluminal angioplasty is a well established technique with wide application, but its place in the overall management of peripheral vascular disease is not well defined. This study compares similar groups of patients with peripheral vascular disease in 1981 and 1984, before and after the introduction of the technique to a district general hospital. More patients are now being investigated and treated and this is almost entirely due to the availability of angioplasty. The rates for surgery have not changed. Percutaneous transluminal angioplasty should therefore be seen as a new and separate form of treatment for peripheral vascular disease, not necessarily influencing or replacing surgery, and requiring its own allocation of resources in accordance with the increase in the level of care afforded by the technique.  相似文献   
196.
197.
The two stage gravimetric technique used for the measurements of industrial aerosols, in combination with measurements of mass-related concentrations of particles in the air, provided major hygienic information on the sizes (dispersity) of the inhaled particles. The results of the measurements taken in various branches of industry, ore and alluval deposit mines clarified the fundamental properties of the particles' distribution into rough and thin fractions. An express two-stage gravimetric technique for determining ore aerosol dispersal contents was proposed, along with the technical characteristics of the USSR-produced dust counters.  相似文献   
198.
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   
199.
Gestational age determination based on obstetric dating criteria, early pregnancy ultrasound scans, Dubowitz examinations, and ultrasound scans performed shortly before delivery were reviewed for 69 preterm infants requiring neonatal intensive care. The last ultrasound scans underestimated gestational age by a median of 8 days, and by 2 weeks or more in 20 of the 69 cases, as opposed to best dating criteria. Ultrasonic fetal weight estimation was more accurate, but erred by more than 20% in 10% of cases. When obstetric decisions regarding preterm neonates must be made without prior information regarding gestational age, late ultrasound findings must be applied with extreme care.  相似文献   
200.
The amount of protein bound per 1 mL of the perfluorocarbon (PFC) emulsion depends on the emulsifier composition and the particle size. A relationship between the amount of bound protein on the particle surface and the physicochemical parameters of the PFC emulsion interaction with the blood serum, which indirectly characterize the surface properties of the PFC particles, is established. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 12, pp. 40–43, December, 2007.  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