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   2349982篇
  免费   171615篇
  国内免费   3331篇
耳鼻咽喉   32049篇
儿科学   75908篇
妇产科学   62710篇
基础医学   348213篇
口腔科学   63633篇
临床医学   211360篇
内科学   457297篇
皮肤病学   51727篇
神经病学   185280篇
特种医学   88012篇
外国民族医学   489篇
外科学   353879篇
综合类   47511篇
现状与发展   12篇
一般理论   848篇
预防医学   182745篇
眼科学   54326篇
药学   175126篇
  11篇
中国医学   4577篇
肿瘤学   129215篇
  2021年   18986篇
  2019年   19539篇
  2018年   27061篇
  2017年   20360篇
  2016年   22752篇
  2015年   25639篇
  2014年   36102篇
  2013年   53961篇
  2012年   74687篇
  2011年   79421篇
  2010年   47063篇
  2009年   44571篇
  2008年   74619篇
  2007年   79491篇
  2006年   80308篇
  2005年   77786篇
  2004年   74370篇
  2003年   71697篇
  2002年   69369篇
  2001年   108743篇
  2000年   111456篇
  1999年   93500篇
  1998年   26991篇
  1997年   23660篇
  1996年   24057篇
  1995年   22717篇
  1994年   20895篇
  1993年   19713篇
  1992年   72002篇
  1991年   70070篇
  1990年   68392篇
  1989年   65665篇
  1988年   60306篇
  1987年   59126篇
  1986年   55218篇
  1985年   53005篇
  1984年   39312篇
  1983年   33397篇
  1982年   19858篇
  1979年   35869篇
  1978年   25656篇
  1977年   21232篇
  1976年   20335篇
  1975年   21816篇
  1974年   26149篇
  1973年   24803篇
  1972年   23201篇
  1971年   22037篇
  1970年   20247篇
  1969年   19315篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
A survey of research activity of American academic child psychiatrists was completed in February, 1989. The survey demonstrated an increase in research activity since the 1983 report in the Current Status of Child Psychiatry. A definition of a researcher was derived from a study of internists and general psychiatrists and applied to the 488 respondents (78.5% of sample), and it was found that males outnumber females and that researchers contribute significantly more to the literature and education than nonresearchers. Early research exposure and mentoring are important influences on a research career. Recommendations by researchers for future training of researchers are presented. Periodic surveys are encouraged.  相似文献   
972.
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   
973.
In a vertically slotted 0.022 X 0.028 inch edgewise system, the use of a two-dimensional ribbon arch--0.022 X 0.016 inch from lateral incisor to lateral incisor and 0.016 X 0.022 inch from the canine to the molars--plus an uprighting spring on the canine maintained incisor position while unilaterally protracting a molar-premolar unit by means of sliding mechanics. Five degrees of labial crown torque was placed in the incisor portion of the wire and the uprighting spring exerted a force of 200 to 250 g. The intra-arch force applied to protract the molar--premolar unit was 300 to 350 g.  相似文献   
974.
975.
976.
Of 299 patients who presented with superficial bladder cancer (Ta, T1), 60 were treated by intravesical chemotherapy (Epodyl, methotrexate or mitomycin C). The rate of tumour progression to muscle invasion or metastases was identical for each intravesical regime. There was no evidence that mitomycin C promoted tumour progression. Carcinoma in situ in non-tumour-bearing urothelium was the most significant predictive factor for progression to muscle invasion or metastases.  相似文献   
977.
Bilateral simultaneous Achilles tendon ruptures are rare, with only ten cases reported in the English literature. Our case is that of a 44-year-old woman, along with a review of the literature. Affected persons usually are on chronic steroid treatment and in the fifth to seventh decades of life. The patient may have concomitant systemic disease, and the injury occurs with relatively mild trauma. The goals of treatment are mainly preventative, i.e., cessation of steroids as soon as possible and protective bracing of the remaining intact Achilles tendon.  相似文献   
978.
The expression of ras oncogene in normal and pathological liver disease   总被引:1,自引:0,他引:1  
Activation of the ras oncogene is associated with overproduction of the normal gene product (p21). Ninety one paraffin-embedded specimens were used to map the distribution of the normal form of p21 in normal, inflamed, cirrhotic and carcinomatous liver parenchyma. Monoclonal antibodies (Mo-RAP) were raised against the normal form of the ras-oncogene product and histological sections were stained by the peroxidase-antiperoxidase technique. Normal, inflamed and cirrhotic liver showed either minimal or moderate cytoplasmic staining. By contrast primary (n = 13) and secondary (n = 41) liver carcinomas exhibited intense staining. The differential pattern observed in p21 distribution could have useful clinical applications.  相似文献   
979.
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   
980.
The authors describe an original application of real time transducers--initially intended for intracavitary sonography--in thoraco-abdominal scanning. The stic-form probe can be easily slipped under the patient. It is then possible to realize a scan with an upward beam. In the postero-anterior scan, the patient is placed in a supine position. He is motionless. We achieve a better visualization of the liquid collections, since their accumulation is declivious. The method allows a wider sonographic window for thoraco-abdominal and diaphragmatic investigation in sonography.  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