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   55468篇
  免费   3312篇
  国内免费   280篇
耳鼻咽喉   507篇
儿科学   1581篇
妇产科学   1399篇
基础医学   7497篇
口腔科学   1078篇
临床医学   5490篇
内科学   11586篇
皮肤病学   1254篇
神经病学   5966篇
特种医学   1916篇
外国民族医学   2篇
外科学   7706篇
综合类   276篇
一般理论   19篇
预防医学   4052篇
眼科学   917篇
药学   3471篇
  1篇
中国医学   123篇
肿瘤学   4219篇
  2024年   77篇
  2023年   550篇
  2022年   1071篇
  2021年   1938篇
  2020年   1167篇
  2019年   1598篇
  2018年   1866篇
  2017年   1346篇
  2016年   1505篇
  2015年   1741篇
  2014年   2343篇
  2013年   2986篇
  2012年   4384篇
  2011年   4423篇
  2010年   2283篇
  2009年   2131篇
  2008年   3525篇
  2007年   3480篇
  2006年   3173篇
  2005年   3145篇
  2004年   2647篇
  2003年   2396篇
  2002年   2157篇
  2001年   637篇
  2000年   540篇
  1999年   545篇
  1998年   448篇
  1997年   334篇
  1996年   284篇
  1995年   257篇
  1994年   225篇
  1993年   195篇
  1992年   253篇
  1991年   261篇
  1990年   199篇
  1989年   196篇
  1988年   204篇
  1987年   184篇
  1986年   188篇
  1985年   143篇
  1984年   140篇
  1983年   123篇
  1982年   105篇
  1981年   79篇
  1980年   71篇
  1979年   81篇
  1978年   78篇
  1977年   73篇
  1975年   75篇
  1973年   84篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
PURPOSE: The purpose of this study was to identify the risk factors for severe discomfort after mandibular third molar surgery and to assess the validity of the Postoperative Symptom Severity (PoSSe) scale. PATIENTS AND METHODS: In a 2-year prospective study, a total of 255 unilateral impacted mandibular third molar teeth were surgically removed under local anesthesia by 3 surgeons. Standardized surgical and analgesic protocols were followed. At the review appointment, 1 week after surgery, all patients returned a completed follow-up questionnaire (PoSSe scale) and were evaluated clinically for postoperative pain (number of painkillers taken) and trismus (differences in mouth opening). Sixteen predictive variables were evaluated using stepwise logistic regression analysis to identify the risk factors associated with severe discomfort. RESULTS: Severe postoperative discomfort was predicted by these independent variables: gender, tobacco use, ramus relationship/space available, and antibiotic prophylaxis. Oral contraceptive use and operation time were not identified as risk factors. The patients' perceptions of the severity of symptoms (PoSSe scale score) was strongly correlated with clinical assessment of trismus (r = 0.54) and pain (r = 0.42). CONCLUSION: The PoSSe scale resulted in a valid and responsive measure of the severity of symptoms after surgical extraction of lower third molars and reflected the clinical severity of the postoperative discomfort. From a patient's perspective, operative factors had little bearing on the quality of life after removal of mandibular third molars.  相似文献   
82.
Background: Liver dysfunction as a result of impaired oxygen availability frequently occurs following hemorrhage and contributes to delayed mortality. Artificial oxygen carriers may improve oxygen supply to vital organs while avoiding the need for allogeneic transfusion.

Methods: Rats were subjected to hemorrhagic hypotension (mean arterial pressure = 35-40 mmHg for 120 min) and were subsequently resuscitated with (1) stored whole rat blood, (2) pentastarch, or (3) pentastarch combined with perflubron emulsion (PFE; 2.7 or 5.4 g/kg body weight), a second-generation artificial oxygen carrier. Recovery of liver adenosine triphosphate, hepatocellular injury, and expression of glutamine synthetase 1, a gene that is induced by exposure of hepatocytes to low partial pressure of oxygen, were studied at 4 h of resuscitation.

Results: Stored whole blood or pentastarch failed to restore liver adenosine triphosphate concentrations after prolonged shock as compared to sham controls and resulted in increased gene expression of glutamine synthetase 1. Addition of 2.7 g PFE/kg restored liver adenosine triphosphate to control, whereas 5.4 g PFE/kg resulted in adenosine triphosphate concentrations significantly above control. Improved hepatocellular oxygen supply was also confirmed by restoration of the physiologic expression pattern of glutamine synthetase 1. Serum enzyme concentrations were highest after resuscitation with stored blood, whereas addition of PFE failed to further decrease enzyme concentrations as compared to pentastarch alone.  相似文献   

83.
Little has been done to investigate the biochemical basis of chronic daily headache (CDH). Our group has recently demonstrated an increase in the cerebrospinal fluid (CSF) levels of nerve growth factor (NGF) in CDH patients, supporting the involvement of this growth factor in the abnormal processing of head pain in this pathological condition. Other members of the neurotrophin family, especially brain-derived neurotrophic factor (BDNF), have been hypothesized as being involved in the development of chronic head pain in patients affected by CDH, but so far no data are available on this subject. BDNF, NGF and glutamate levels were determined in the CSF of 25 patients affected by CDH with a previous history of migraine. These levels were compared with those of a group of 20 control subjects, for whom the CSF examination and other instrumental investigations excluded diseases of the central and peripheral nervous systems. Significantly higher levels of BDNF, NGF and glutamate were found in CDH patients compared with control subjects (p<0.0001, p<0.0002 and p<0.001, respectively). A significant positive correlation emerged between CSF values of BDNF and those of NGF (r=0.61, p<0.001) and glutamate (r=0.44, p<0.025) in CDH patients. No significant differences were detected in BDNF, NGF and glutamate levels between CDH patients with analgesic overuse and those without. These results support the involvement of BDNF in CDH through the potentiation of glutamatergic transmission involved in the processing of head pain. The significant correlation between BDNF and NGF levels suggests that NGF-mediated up-regulation of BDNF in central sites involved in long-term sensitization plays a key role in persistent head pain in CDH patients. Correspondence to P. Sarchielli  相似文献   
84.
85.
86.
87.
The present study deals with the induction of teratomas and teratocarcinomas in two strains of mice (C3H/Bln and 129/terSv). 6 to 7 days old egg cylinders were transplanted beneath the kidney capsule of adult syngeneic male and female recipients. Out of 115 grafted embryos 32 gave rise to teratoid tumors. Both the overall tumor incidence (teratomas and teratocarcinomas) and the overall percentage of teratocarcinomas were approximately the same in the strains used. In strain C3H/Bln the gender of the recipient seemed to influence the outgrowth of malignant tumors. Two transplantable C3H-teratocarcinomas could be established (DTC-4, DTC-8). Up to date both have retained their pluripotent differentiation pattern which makes them useful for intended further investigations.  相似文献   
88.
BACKGROUND: Worldwide, fire-related burns are a major cause of unintentional injury, morbidity and mortality, with the majority of deaths occurring in developing countries. In the US, as in other countries, most fatal fires occur in the home. Effective prevention strategies for residential fires are, however, currently underutilized. The news media is one available communication channel to promote such strategies, and analyzing current news coverage is a first step towards incorporating media advocacy into injury prevention efforts related to residential fires. METHODS: Four daily newspapers circulating widely in Maryland were monitored for 1 year. Articles describing residential fires were coded for measures of prominence, content and frame. Analysis focused on measures of issue newsworthiness, reporting of causation and consequences of fires, and inclusion of public health context and conveyance of prevention messages. RESULTS: The data indicate that fires are newsworthy, with 374 relevant news articles in a 1-year period, 32% of which appear on the first page of a section. Coverage generally concerned recent local fire events. Most articles discussed the consequences of fires (88%), and identified a causal factor (58%). Only 36%, however, included prevention information, and less than one-quarter set residential fires in a public health context. CONCLUSION: The newsworthiness of residential fires provides a clear opportunity for widespread communication around injury prevention. Improving media advocacy will entail framing discussion of recent fire events in such a way as to support inclusion of prevention strategies and a public health context in news coverage.  相似文献   
89.
Background Optic disc anomalies are frequently associated with Alagille syndrome. We report here the first case of a patient with Alagille syndrome combined with optic pit and serous macular detachment. Methods A male patient with Alagille syndrome was referred from the pediatric hepatology department for investigation of visual loss in the right eye. Anterior segment examination showed evidence of posterior embryotoxon, confirmed by gonioscopic evaluation. Dilated fundus examination revealed serous macular detachment and optic pit. Results OCT 3 scans confirmed the clinical findings. Conclusions Optic pit is uncommon and should prompt a search for genetic disorders or development abnormalities. The association between the two syndromes in this patient might be due to failure of correct neuroectodermal development, for which a common genetic pathway is likely.  相似文献   
90.
Twenty patients with AIDS who had intracranial lesions underwent both brain biopsy and cerebro-spinal fluid (CSF) examination to compare histological diagnosis with the polymerase chain reaction (CSF-PCR) for the identification of infectious agents. CSF-PCR was performed for herpes simplex virus, varicella zoster virus, cytomegalovirus (CMV), JC virus (JCV), Epstein-Barr virus (EBV), Toxoplasma gondii and Mycobacterium tuberculosis. A definitive diagnosis was obtained by brain biopsy in 14 patients (2 with astrocytoma, 12 with brain infection). CSF-PCR was positive for EBV DNA in 3 of 3 cases of primary cerebral lymphoma, positive for JCV DNA in 6 of 7 biopsy-proven (and one autopsy-proven) cases of progressive multifocal leukoencephalopathy (PML). CSF-PCR was positive for CMV DNA in one biopsy-proven and one autopsy-proven case of CMV encephalitis (the former also had PML) and positive for M. tuberculosis DNA in one case of tuberculous encephalitis. None of the five toxoplasmic encephalitis cases (one definite, four presumptive) were T. gondii DNA positive. There was close correlation between histology and CSF-PCR for CMV encephalitis, PML and PCL. Antitoxoplasma therapy affected the sensitivity of both histological and CSF-PCR methods. Received: 8 November 1995 Received in revised form: 9 July 1996 Accepted: 19 July 1996  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