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   26966篇
  免费   1475篇
  国内免费   119篇
耳鼻咽喉   395篇
儿科学   698篇
妇产科学   562篇
基础医学   4661篇
口腔科学   457篇
临床医学   2510篇
内科学   5432篇
皮肤病学   589篇
神经病学   2635篇
特种医学   1118篇
外科学   3660篇
综合类   144篇
现状与发展   1篇
一般理论   11篇
预防医学   1487篇
眼科学   608篇
药学   1777篇
中国医学   40篇
肿瘤学   1775篇
  2023年   87篇
  2022年   196篇
  2021年   410篇
  2020年   258篇
  2019年   424篇
  2018年   523篇
  2017年   371篇
  2016年   518篇
  2015年   540篇
  2014年   730篇
  2013年   957篇
  2012年   1693篇
  2011年   1680篇
  2010年   999篇
  2009年   1007篇
  2008年   1498篇
  2007年   1658篇
  2006年   1696篇
  2005年   1775篇
  2004年   1670篇
  2003年   1514篇
  2002年   1521篇
  2001年   420篇
  2000年   311篇
  1999年   384篇
  1998年   377篇
  1997年   297篇
  1996年   243篇
  1995年   223篇
  1994年   183篇
  1993年   181篇
  1992年   178篇
  1991年   191篇
  1990年   188篇
  1989年   183篇
  1988年   183篇
  1987年   152篇
  1986年   131篇
  1985年   132篇
  1984年   134篇
  1983年   103篇
  1982年   87篇
  1981年   108篇
  1980年   97篇
  1979年   119篇
  1978年   89篇
  1977年   96篇
  1976年   82篇
  1974年   85篇
  1972年   85篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
AIMS: The comparison of three imaging methods to determine which is the most accurate and reliable for the detection of right-to-left shunt. METHODS AND RESULTS: One hundred and seven patients who were hospitalized for stroke underwent: a transthoracic echocardiography (TTE) using second harmonic, a transcranial Doppler (TCD) and a transesophageal echocardiography (TEE) from August 2003 to April 2004. All studies were recorded on a videotape and were studied by a physician blinded to the study. With TTE and TEE, we found 44 (41%) patent foramen ovales. All contrast tests were positive with TCD for these 44 patients. For two patients, the contrast test was positive only with TTE and TCD. We found four false negative contrast tests with TTE. Among the 63 patients who had a negative contrast test with TEE and TTE, the results were the same with TCD for 59 of them; we were not able to determine a cause for the four positive tests. CONCLUSION: This study confirms that transesophageal echocardiography has limitations in the diagnosis of patent foramen ovale. In this study, the negative predictive value of transcranial Doppler was excellent. Therefore, this examination is able to exclude a patent foramen ovale with a high level of confidence.  相似文献   
942.
We here describe 13 patients with non-Hodgkin's lymphoma (NHL) and a translocation t(11:14)(q13:q32). They were part of a series of 163 patients with NHL and an abnormal karyotype, serially referred to our institution between January 1984 and 1990. Patients with t(11:14) seem to present several common and interesting features. Males are more frequently affected than females, and old people more than young. They present at diagnosis with advanced disease and usually show involvement of epithelium and bone marrow. With respect to histologic diagnoses, these patients are usually considered to be of low-grade malignancies. However, most of them do very poorly, have short complete remission and frequent relapses whatever the treatment. As a whole, the median survival rate is rather low. The cytologic, histologic as well as the immunologic patterns tend to be uniform: tumours are composed of small cells and display features of mantle zone/intermediate lymphocytic lymphoma. They express high IgM and low IgD levels and more commonly bear Ig lambda light chains. They also express all pan-B antigens (except CD23) as well as the CD5 antigen, but usually lack the CD10. According to these characteristics, these tumours could be placed in between lymphocytic lymphomas (which usually express CD23) and follicular lymphomas (which commonly lack IgD and CD5 and bear CD10 as well as a t(14:18).  相似文献   
943.
Most of the viruses involved in causing encephalitis are arthropod-borne viruses, with the exception of arenaviruses that are rodent-borne. Even if little information is available, there are indications that, most of these encephalitis-associated viruses could be used by aerosolisation during a bioterrorist attack. Viral transfer from blood to the CNS through the olfactory tract has been suggested. Another possible route of contamination is by vector-borne transmission such as infected mosquitoes or ticks. Alphaviruses are the most likely candidates for weaponisation. The clinical course of the diseases caused by these viruses is usually not specific, but differentiation is possible by using an adequate diagnostic tool. There is no effective drug therapy for the treatment of these diseases and treatment is mainly supportive, but vaccines protecting against some of these viruses do exist.  相似文献   
944.
Several types of biliary tract abnormality of undertermined origin have been described among AIDS patients. The aims of this study are (1) to evaluate whether biliary tree involvement is in fact one or several homogeneous morphological entities, (2) to specify the role of CMV orCryptosporidium sp. infection, and (3) to evaluate the possible efficacy of treatment. Since ultrasound had revealed abnormality in the biliary tree, 26 consecutive AIDS patients underwent cholangiography. Cholangiograms enabled us to distinguish between two types of biliary tract involvement: (1) gradual and regular stenosis of the terminal portion of the common bile duct associated with dilation but without irregularity of the intrahepatic biliary ducts was present in 27% of our cases, and (2) distal stenosis of the extrahepatic biliary ducts combined with diffuse irregularity of the caliber of the intrahepatic bile ducts was present in 73% of our cases. Concomitant infection by CMV orCryptosporidium sp. was significantly more frequent when intrahepatic duct irregularities were present (94%) than when absent (14%,P<0.001). Anti-CMV treatment and sphincterotomy were unsuccessful in treating anomalies of the intrahepatic biliary tract. Conversely, sphincterotomy caused rapid and lasting disappearance of pain in all our patients. In conclusion, biliary tract involvement in AIDS patients is of two types. CMV infection and infection byCryptosporidium sp. are most frequent when the large intrahepatic ducts are implicated.  相似文献   
945.
Human papillomavirus (HPV) XS2 was isolated from warts on an immunosuppressed patient. After HPV vaccination, the warts resolved. HPVXS2 was also found in warts and normal skin of HIV-positive patients and rarely in HIV-negative controls. Further studies should elucidate the mechanisms that lead to wart clearance.  相似文献   
946.
Multidrug-resistant and highly virulent Klebsiella pneumoniae isolates are emerging, but the clonal groups (CGs) corresponding to these high-risk strains have remained imprecisely defined. We aimed to identify K. pneumoniae CGs on the basis of genome-wide sequence variation and to provide a simple bioinformatics tool to extract virulence and resistance gene data from genomic data. We sequenced 48 K. pneumoniae isolates, mostly of serotypes K1 and K2, and compared the genomes with 119 publicly available genomes. A total of 694 highly conserved genes were included in a core-genome multilocus sequence typing scheme, and cluster analysis of the data enabled precise definition of globally distributed hypervirulent and multidrug-resistant CGs. In addition, we created a freely accessible database, BIGSdb-Kp, to enable rapid extraction of medically and epidemiologically relevant information from genomic sequences of K. pneumoniae. Although drug-resistant and virulent K. pneumoniae populations were largely nonoverlapping, isolates with combined virulence and resistance features were detected.  相似文献   
947.

Background

Productivity costs are often ignored in economic evaluations. In order to facilitate productivity cost inclusion, it has been suggested to estimate productivity costs indirectly using quality of life data.

Objective

This study aimed to derive and validate an algorithm for predicting productivity losses on the basis of quality-of-life data using the EQ-5D-3L.

Methods

A large representative sample of the Dutch general public (n = 1,100) was asked in a web-based questionnaire to state their expected level of productivity in terms of absenteeism and presenteeism for multiple EQ-5D health states. Based on these data, two generalized estimating equations (GEE) models were constructed: (1) a model predicting levels of absenteeism and (2) a model predicting presenteeism. The models were validated by comparing model predictions with conventionally measured productivity within a group of low back pain patients.

Results

Predicted absenteeism levels based on EQ-5D health state closely resembled conventionally measured absenteeism levels. Productivity losses related to presenteeism seemed somewhat overestimated by our prediction model. Measured and predicted productivity were moderately but highly significantly correlated.

Conclusions

Overall, it appears possible to make reasonable productivity predictions based on EQ-5D data. Further exploration and validation of prediction algorithms remains necessary, however, especially for presenteeism.  相似文献   
948.
We systematically reviewed randomised controlled trials of peri‐operative melatonin. We included 24 studies of 1794 participants that reported eight peri‐operative outcomes: anxiety; analgesia; sleep quality; oxidative stress; emergence behaviour; anaesthetic requirements; steal induction; and safety. Compared with placebo, melatonin reduced the standardised mean difference (95% CI) pre‐operative anxiety score by 0.88 (0.44–1.33) and postoperative pain score by 1.06 (0.23–1.88). The magnitude of effect was unreliable due to substantial statistical heterogeneity, with I2 87% and 94%, respectively. Qualitative reviews suggested the melatonin improved sleep quality and emergence behaviour, and might be capable of reducing oxidative stress and anaesthetic requirements.  相似文献   
949.
Retroperitoneal soft tissue sarcomas are characterized by a high rate of local recurrence. Complete tumor resection is the only potentially curative therapeutic option. The concept of a systematic compartmental resection is to remove the tumor en bloc with a margin of uninvolved tissue and organs. This is frequently only achieved by multivisceral resection which often includes kidney, colon, pancreas and parts of the diaphragm or the psoas muscle. The adoption of such a policy of multivisceral organ resection improves the proportion of curative resections and, ultimately, results in lower local recurrence rates. The present article comprehensively describes the operative procedures, perioperative treatment and the oncological results of surgery for retroperitoneal sarcomas. The role of surgery in oncological treatment plans and the importance of specialized centres are outlined in detail.  相似文献   
950.
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