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   37697篇
  免费   2125篇
  国内免费   56篇
耳鼻咽喉   385篇
儿科学   1149篇
妇产科学   804篇
基础医学   5800篇
口腔科学   273篇
临床医学   3396篇
内科学   9049篇
皮肤病学   850篇
神经病学   3522篇
特种医学   1114篇
外国民族医学   31篇
外科学   4628篇
综合类   77篇
一般理论   6篇
预防医学   2689篇
眼科学   614篇
药学   2534篇
中国医学   68篇
肿瘤学   2889篇
  2023年   202篇
  2022年   130篇
  2021年   529篇
  2020年   315篇
  2019年   589篇
  2018年   1083篇
  2017年   768篇
  2016年   730篇
  2015年   910篇
  2014年   920篇
  2013年   1481篇
  2012年   2577篇
  2011年   2515篇
  2010年   1216篇
  2009年   950篇
  2008年   2311篇
  2007年   2369篇
  2006年   2231篇
  2005年   2313篇
  2004年   2245篇
  2003年   2050篇
  2002年   2008篇
  2001年   1055篇
  2000年   1128篇
  1999年   895篇
  1998年   181篇
  1997年   123篇
  1996年   131篇
  1995年   125篇
  1994年   106篇
  1992年   521篇
  1991年   461篇
  1990年   460篇
  1989年   431篇
  1988年   389篇
  1987年   377篇
  1986年   339篇
  1985年   318篇
  1984年   227篇
  1983年   179篇
  1982年   104篇
  1979年   156篇
  1974年   118篇
  1973年   105篇
  1972年   108篇
  1971年   114篇
  1970年   106篇
  1969年   129篇
  1968年   110篇
  1967年   102篇
排序方式: 共有10000条查询结果,搜索用时 447 毫秒
141.
142.
Summary Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for dopaminergic neurons. Since dopaminergic neurons degenerate in Parkinson's disease, this factor is a potential therapeutical tool that may save dopaminergic neurons during the pathological process. Moreover, a reduced GDNF expression may be involved in the pathophysiology of the disease. In this study, we tested whether altered GDNF production may participate in the mechanism of cell death in this disease. GDNF gene expression was analyzed by in situ hybridization using riboprobes corresponding to a sequence of the exon 2 human GDNF gene. Experiments were performed on tissue sections of the mesencephalon and the striatum from 8 patients with Parkinson's disease and 6 control subjects matched for age at death and for post mortem delay. No labelling was observed in either group of patients. This absence of detectable expression could not be attributed to methodological problems as a positive staining was observed using the same probes for sections of astroglioma biopsies from human adults and for sections of a newborn infant brain obtained at post-mortem. These data suggest that GDNF is probably expressed at a very low level in the adult human brain and its involvement in the pathophysiology of Parkinson's disease remains to be demonstrated. GDNF may represent a powerful new therapeutic agent for Parkinson's disease, however.  相似文献   
143.
Steady-state nerve growth factor (NGF) mRNA levels were estimated in male sex organs of the mouse, rat, and guinea pig by RNA blot hybridization analysis. The abundance of NGF mRNAs was in the order vas deferens greater than epididymis greater than or equal to seminal vesicles much greater than testis. NGF mRNA levels in these organs were compared with those estimated for other rat peripheral tissues and were found to correlate with the density of their sympathetic innervation, with the exception of guinea pig prostate. Castration had no significant effect on NGF mRNA levels in the guinea pig prostate, suggesting that NGF synthesis in this tissue is not under direct androgen control. NGF-like and proNGF-like immunoreactivities were localized by immunohistochemical techniques in the secretory cells of the glandular epithelium of the guinea pig prostate and in germ cells in the seminiferous tubules of the mouse testis.  相似文献   
144.
A 24 year-old patient presented with chronic intracranial hypertension, palsy of both abducens nerves and upward gaze, and right hypoesthesia. CT scan and MRI showed a left thalamic tumor infiltrating the left cerebral peduncle. A stereotactic biopsy revealed a germ cell tumor. Following radiotherapy the patient recovered except for ophthalmoplegia. The tumor totally disappeared on CT scan and MRI.  相似文献   
145.
The authors report 3 cases of slowly progressive aphasia with different language disturbances: anomia, pure word deafness and Broca's aphasia. All patients were independent in daily life activities. Insight, judgement and overall behaviour were intact. There was no major disturbance of other cognitive functions, but psychometric tests showed mild deficits suggesting widespread involvement. CT scans and magnetic resonance imaging showed focal dilatation of the left sylvian fissure. A positron emission tomographic study showed left perisylvian hypometabolism. A review of the literature yielded an increasing number of cases of this degenerative syndrome affecting dominant hemisphere language areas. Our cases confirm the clinical heterogeneity of degenerative aphasia. Postmortem neuropathological examinations are rare and many causes are found: Pick's disease, Alzheimer's disease or aspecific gliosis.  相似文献   
146.
Prolonged increase in serum transaminase activity is usually seen in chronic liver disease. Evaluation in one patient with such a prolonged increase having no evidence of liver disease including histological examination, revealed a limb girdle muscular dystrophy. This case suggests that a muscular disease should be suspected in all children with persistent increase in serum transaminase activity when the liver is apparently normal.  相似文献   
147.
The purpose of this study was to evaluate the merits of the end expiratory lung volume as an indirect ventilatory index of bronchial obstruction and to show an application of continuous monitoring of lung volume in asthmatic patients. The accuracy of the external measurements (IS) of functional residual capacity (FRC) was controlled by comparing them with the helium measurements (DS) obtained during nine methacholine tests (IS = 0.06 + 1.065 DS in litres: R2 = 0.99). Seven asthmatics (18-48 yr) were monitored by measuring rib cage and abdominal perimeter variations. This was done in basal condition, after methacholine-induced bronchoconstriction and after bronchodilation by either salbutamol or oxytropium bromide inhalation. All the subjects were investigated on two separate days and were their own control. Bronchoconstriction produced a significant increase (p less than 0.01) of tidal volume (VT: + 67%), external minute ventilation (VE: + 58%), mean inspiratory flow (VT/TI: + 78%) and FRC (+ 26.5%) while frequency (f) and fractional inspiratory time (TI/TT) fluctuated non significantly. In the group of seven tested subjects, there was a significant correlation (p less than 0.01) between forced expiratory volume in one second (FEV1) and VE, FEV1 and VT/TI, FEV1 and FRC. However, the individual regression line showed a significant relationship only between FEV1 and FRC (R2 = 0.80 +/- 0.04). We therefore conclude that the variation of the end expiratory level can be chosen as an indirect index of bronchoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
148.
The Cobas-Bact (Roche Diagnostics, Basel, Switzerland) new rotor for the identification (ID) in 4 h 20 min of 33 members of the family Enterobacteriaceae to genus and species level was evaluated by testing 444 strains of which 398 belonged to common species and 46 belonged to rare species of Enterobacteriaceae. Each strain was identified by the API 20E system (Analytab Products, Plainview, N.Y.), and additional discriminating tests were set up if necessary. Only first-choice ID were considered in this study and were classified either as high-confidence ID (normalized likelihood, greater than or equal to 80%) or as low-confidence ID (normalized likelihood, less than 80%) requiring additional tests for confirmation. The data were analyzed by two versions of Cobas-Bact software. With the first version of the software (SW8446), the overall accuracy of Cobas-Bact was 95.5% (424 correct ID of 444). When restricted to high-confidence ID it rose to 99.4% (350 of 352) for the common species and 96.9% (31 of 32) for the rare species. Only three strains of the high-confidence group were misidentified. Sixty ID were considered unacceptable because of their low confidence. Using the first software version (SW8446) they represented 12% (46 of 398) of the common species (17 typical strains, 10 Shigella species, 10 inactive Escherichia coli strains, and 9 rare biotypes) and 30% (14 of 46) of the rare species. The same data analyzed by the new version (SW8524) of the Cobas-Bact software resulted in an overall accuracy of 93.9% (417 correct ID). The number of high-confidence ID rose to 401, of which 392 (97.7%) were accurate. The decrease in low-confidence ID (43 versus 60) was mainly due to the Shigella species. In conclusion the accuracy of Cobas-Bact identification system was very good when restricted to high-confidence ID. The Cobas-Bact performance for rare species ID was poorer, but the small number of strains tested does not allow definitive conclusions.  相似文献   
149.
150.
The aim of this study was to estimate the incidence of morbidity and mortality due to injuries in the population over the age of 14 years in Barcelona, Spain. Injury distribution according to sex, age, external cause, place of occurrence of the injury and severity was also obtained. A one-year survey was conducted in the emergency departments of the six main hospitals in Barcelona, based on a multistage sampling. Information was collected prospectively in emergency services by specially trained non-staff interviewers. Mortality data were drawn from death certificates. The incidence rate was 74.7 injury cases per 1,000 person-years over 14 years of age, higher in males than in females. Injury rates were highest in the youngest age-group and progressively lower until people over 75 years of age. Main external causes of injury were falls, being struck or caught by objects, and traffic-related injuries. The leading specific causes of injury mortality were traffic injuries, suicides and poisonings. While the overall admission incidence was 3.34 cases per 1,000 inhabitants, the proportion of hospitalized cases was 45.0 per 1,000 injury cases admitted to emergency rooms, higher for females, for traffic injuries and in the elderly population. Ninety-six percent of injury cases had an ISS value of 8 or less, mean ISS being highest for traffic injuries and falls. Injury morbidity and mortality amongst residents of Barcelona follow sex, age and cause of injury patterns which are, overall, comparable to those observed in other industrialized countries, suggesting that similar etiologic factors might be operating in those areas. The results should enable the orientation of injury prevention policies in the urban environment targeted on the young and the elderly population.  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