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   2078654篇
  免费   157760篇
  国内免费   4725篇
耳鼻咽喉   28404篇
儿科学   67968篇
妇产科学   59360篇
基础医学   295138篇
口腔科学   56813篇
临床医学   183040篇
内科学   413067篇
皮肤病学   47006篇
神经病学   169870篇
特种医学   80465篇
外国民族医学   772篇
外科学   316251篇
综合类   47734篇
现状与发展   3篇
一般理论   703篇
预防医学   160441篇
眼科学   47486篇
药学   147330篇
  1篇
中国医学   4557篇
肿瘤学   114730篇
  2019年   16214篇
  2018年   22847篇
  2017年   17656篇
  2016年   19492篇
  2015年   21997篇
  2014年   31320篇
  2013年   47161篇
  2012年   63765篇
  2011年   67746篇
  2010年   40200篇
  2009年   38348篇
  2008年   63304篇
  2007年   67061篇
  2006年   67661篇
  2005年   66008篇
  2004年   63210篇
  2003年   60549篇
  2002年   58805篇
  2001年   100324篇
  2000年   102851篇
  1999年   86143篇
  1998年   24176篇
  1997年   21978篇
  1996年   22000篇
  1995年   20656篇
  1994年   19014篇
  1993年   17908篇
  1992年   65671篇
  1991年   62731篇
  1990年   60738篇
  1989年   58070篇
  1988年   53601篇
  1987年   52473篇
  1986年   49532篇
  1985年   47264篇
  1984年   35794篇
  1983年   30390篇
  1982年   18384篇
  1981年   16211篇
  1979年   32170篇
  1978年   22619篇
  1977年   18902篇
  1976年   17900篇
  1975年   18977篇
  1974年   22822篇
  1973年   21967篇
  1972年   20631篇
  1971年   18888篇
  1970年   18080篇
  1969年   16861篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A percentage of human T lymphocytes forms rosettes with autologous erythrocytes and this property has been considered as a marker for post-thymic precursor suppressor cells capable of providing suppression under the influence of inducer cells. We quantitated autologous rosette-forming T cells (ARFC) in the peripheral blood of 37 patients with chronic HBV infection: 8 healthy carriers, 9 chronic persistent hepatitis (CPH-B) and 20 chronic active hepatitis (CAH-B). Two control groups were studied, one consisting of 26 healthy individuals and the other of 8 individuals with non-HBV-associated CAH. Patients with non-HBV-associated CAH had a significant reduction in the proportion of ARFC, whereas CAH-B patients fell into 2 distinct patterns, one with increased and the other with decreased proportions of ARFC. This was unrelated to the degree of biochemical activity of the disease or to degree of viral replication as defined by HBeAg status and HBV-DNA in the serum. Healthy carriers and CPH-B had no changes in ARFC. Simultaneous quantitation of OKT4 and OKT8+ cells was done and a positive correlation was found between the proportions of ARFC and the proportions of OKT8+ cells. The possible significance of this correlation and the relevance of the bimodal distribution of autologous rosette-forming cells in CAH-B are discussed.  相似文献   
992.
Electrocardiograms were evaluated in 39 children and adolescents before and after the clinical use of imipramine and desipramine. The average increase in PR interval was 0.01 seconds. The PR interval increased by 0.02 seconds in 11 subjects, and a new first-degree atrioventricular block developed in two subjects. These changes were not related to the choice between imipramine and desipramine, the dose, or the method of administration. An increase in PR interval by 0.02 seconds or more did correlate with having an abnormality disclosed on a pretreatment electrocardiogram. The average increase in PR interval was 0.007 seconds for subjects with normal baseline electrocardiograms and 0.019 seconds for subjects with conduction and nonconduction abnormalities disclosed in baseline tracings. None of the electrocardiogram changes resulted in adverse clinical consequences.  相似文献   
993.
Epidemiology of multi-infarct dementia   总被引:2,自引:0,他引:2  
Multi-infarct dementia (MID), thought to result from the cumulative effect of repeated episodes of cerebral infarction, represents a sizable proportion of the dementia cases in the population. The frequency of MID as the cause of dementia is commonly quoted as 12-20%, but a more conservative figure on the order of 10% is suggested from prospective epidemiologic studies. Its prevalence increases steadily with advancing age, and a male predominance has been noted. Geographical variations in prevalence of MID may reflect true geographic/ethnic differences or lack of uniformity in the use of diagnostic criteria. Risk factors possibly associated with dementia after stroke include advancing age, previous cerebral or myocardial infarction, an atherothrombotic stroke mechanism, and cerebral atrophy as detected by imaging studies. In order to clarify the role of cerebrovascular disease as a cause of dementia, future epidemiologic studies should define the entity in precise terms, and place emphasis on clearly establishing the temporal relationship between stroke and dementia; new onset of dementia should be correlated with the clinical and anatomic features of the stroke.  相似文献   
994.
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   
995.
We report a case of mild visuo-spatial neglect consequent upon right-hemisphere stroke. At the time of testing, the patient had a complete left visual field deficit but only a very slight left hemiparesis. Under conventional testing conditions, line bisection performed with the right hand showed more severe left neglect than when performed with the left hand. This pattern of performance could, however, be modified, both quantitatively and qualitatively, by changing the starting position of the patient's hand when bisecting horizontal lines. The results suggest that spatio-motor cueing has a more profound effect upon task performance than does differential hemispheric activation per se. We also provide a demonstration that, in a normal subject, the starting position of the hand is likewise a crucial determinant of task performance. In this case, however, there is also an interaction between the hand (and hence hemisphere) deployed and the position of that hand in space.  相似文献   
996.
The Naval Special Board of Flight Surgeons was established in 1956 for the evaluation of Navy, Marine Corps, and Coast Guard problem aeromedical cases. This paper examines a sample 248 of these cases for the period of 1974-83 with respect to the characteristics of those referred, their referral diagnostic category, and the recommendation of the Special Board regarding return to a flying status. Those cases with a referral diagnostic category of ENT and Ophthalmology were less likely to be returned to flight status. Older, more senior pilots, and pilots with more total flight time were less likely to be returned to unrestricted flying than were their younger, more junior, and less experienced counterparts. Otherwise, no significant difference in outcome based on age, rank, marital status, branch of service, specialty, or flight hours was detected. Overall, 61% of those evaluated by the SBFS were returned to flight status.  相似文献   
997.
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   
998.
The livers of 26 adult males with acquired immune deficiency syndrome (AIDS) were reviewed. The occurrence of portal tracts with diminished lymphocytes, probably reflecting generalized exhaustion of the lymphoid system, was a characteristic morphologic change, and was found in all cases. Kupffer cell hyperplasia was also a frequent finding and probably reflected generalized infection(s). Punched-out clusters of foamy histiocytes filled with acid-fast bacilli, typical for infection with Mycobacterium avium intracellulare (MAC), were found in three patients. In addition, MAC was cultured from two livers without the foamy histiocytic changes. Chronic viral hepatitis (three cases) and deposition of polarizable materials (one case) in the liver might be related to unusual habits of patients with AIDS. In conclusion, livers from patients with AIDS disclosed several kinds of lesions reflecting underlying or associated conditions in AIDS, but these did not contribute to the cause of death in our patients.  相似文献   
999.
1000.
The long-term results of the conservative treatment of wrist fractures were observed in a follow-up study of 297 cases over a period of one and one-half years to six years. The evaluation of the results was based on clinical parameters, both subjective and objective, as well as radiological features. The results were: excellent in 38% of cases, good in 49%, fair in 11.5%, and poor in 1.5%; considerably worse were the subjective results (20% fair to poor). No statistically significant relation could be found between results and type of fracture. Clinical deformities and pain in the area of the distal radioulnar joint were frequent. Decrease in grip strength was observed in 17.8% of cases. A limitation of wrist movement was not frequent. Numerous compressive neuropathies were found (41 in 35 patients), especially of the median nerve. The values relative to the three radiographic parameters under investigation (that is, radial deviation, volar tilt, and radioulnar index) were often found to be out of the normal range. The comparative study of postreduction and follow-up radiograms show the loss of reduction to be frequent, especially as far as the volar tilt is concerned. The frequent radiologic deformities are associated with significantly bad results only in cases of extremely abnormal values. However, fractures of the distal radius are not to be underestimated. Long-term results following conservative treatment may not be as acceptable as is generally assumed.  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