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   4240篇
  免费   585篇
  国内免费   23篇
耳鼻咽喉   31篇
儿科学   178篇
妇产科学   66篇
基础医学   572篇
口腔科学   117篇
临床医学   479篇
内科学   1019篇
皮肤病学   73篇
神经病学   583篇
特种医学   165篇
外科学   542篇
综合类   11篇
预防医学   352篇
眼科学   119篇
药学   188篇
中国医学   5篇
肿瘤学   348篇
  2024年   8篇
  2023年   66篇
  2022年   68篇
  2021年   120篇
  2020年   128篇
  2019年   102篇
  2018年   170篇
  2017年   177篇
  2016年   169篇
  2015年   185篇
  2014年   215篇
  2013年   300篇
  2012年   268篇
  2011年   265篇
  2010年   197篇
  2009年   263篇
  2008年   238篇
  2007年   239篇
  2006年   219篇
  2005年   217篇
  2004年   184篇
  2003年   153篇
  2002年   169篇
  2001年   56篇
  2000年   42篇
  1999年   52篇
  1998年   64篇
  1997年   63篇
  1996年   62篇
  1995年   47篇
  1994年   37篇
  1993年   36篇
  1992年   40篇
  1991年   27篇
  1990年   9篇
  1989年   22篇
  1988年   10篇
  1987年   18篇
  1986年   14篇
  1985年   16篇
  1984年   15篇
  1983年   12篇
  1982年   9篇
  1981年   9篇
  1978年   6篇
  1977年   8篇
  1975年   7篇
  1974年   6篇
  1973年   6篇
  1971年   6篇
排序方式: 共有4848条查询结果,搜索用时 46 毫秒
991.
992.
993.
In the class II region of the major histocompatibility complex (MHC), four genes implicated in MHC class I-mediated antigen processing have been described. Two genes (TAP 1 and TAP 2) code for multimembrane-spanning ATP-binding transporter proteins and two genes (LMP 2 and LMP 7) code for subunits of the proteasome. While TAP 1 and TAP 2 have been shown to transport antigenic peptides from the cytosol into the endoplasmic reticulum, where the peptides associate with MHC class I molecules, the role of LMP 2/7 in antigen presentation is less clear. Using antigen processing mutant T2 cells that lack TAP 1/2 and LMP 2/7 genes, it was recently shown that expression of TAP 1/2 alone was sufficient for processing and presentation of the influenza matrix protein M1 as well as the minor histocompatibility antigen HA-2 by HLA-A2. To understand if presentation of a broader range of viral antigens occurs in the absence of LMP 2/7, we transfected T2 cells with TAP 1, TAP 2 and either of the H-2Kb, Db or Kd genes and tested their ability to present vesicular stomatitis vires and influenza virus antigens to virus-specific cytotoxic T lymphocytes. We found that T2 cells, expressing TAP 1/2 gene products, presented all tested viral antigens restricted through either the H-2Kb, Db or Kd class I molecules. We conclude that the proteasome subunits LMP 2/7 as well as other gene products in the MHC class II region, except from TAP 1/2, are not generally necessary for presentation of a broader panel of viral antigens to cytotoxic T cells. However, the present results do not exclude that LMP 2/7 in a more subtle way may, or in rare cases completely, affect processing of antigen for presentation by MHC class I molecules.  相似文献   
994.
Abstract: In this study we characterized the haplotypes found in IDDM patients that normally confer resistance to the disease in order to localize the polymorphisms relevant for the protection. We studied 15 DR2-positive subjects with IDDM for their DRB1, DRB5 and DQB1 genes using RFLP, polymerase chain reaction (PCR), oligonucleotide typing, and in some specific cases direct sequencing after allele-specific PCR. In addition we analyzed 39 DR2-positive, IDDM non-associated haplotypes representing those haplotypes that are not inherited to probands and hence are present only in healthy family members. The frequency of the DRB1*1501-DRB5*0101-DQB1*0602 haplotype was slightly decreased among diabetic patients (80% vs. 92%). In addition, two unconventional haplotypes DRB1*1501-DRB5*0101-DQB1*05031 and DRB1*1501-DRB5*0101-DQB1*0502 were found in patients with IDDM while all the control ones were conventional. The sequencing of the DQB1*0602 allele present in IDDM haplotypes showed no differences when compared to the controls. These results support the primary but not absolute role of DQ in the protection against IDDM. An additional role of factors centromeric to DQB1 gene was suggested by findings based on the biallelic TaqI RFLP polymorphism of the DQA2 gene. All DR2-DQB1*0602 IDDM haplotypes were associated with the 2.1-kb fragment while in the control group the 2.1-kb and 1.9-kb fragments were evenly distributed.  相似文献   
995.
996.
Background: The Swedish adjustable gastric band (SAGB) was introduced in 1985 and rapidly gained popularity.Today more than 21,000 gastric banding procedures have been performed in Europe. The reported results of gastric banding operations are mainly good, although the method is not without controversies and risks. We report here our initial experience with the SAGB. Methods: 60 patients (44 women, 16 men) were treated surgically for morbid obesity between the years 1996 and 1999, with SAGB. Median age of the patients was 44 years (range 21-64) and preoperative median Body Mass Index (BMI, kg/m2) was 45 (range 35-55). 3 patients were operated by an open approach, and the remaining 57 laparoscopically. Results:Operative time was 62-206 minutes (median 97 minutes). Only one operation was converted to open approach (1.8%), due to extensive adhesions. No intraoperative complications occurred. At 1 year follow-up, mean weight loss was 30 kg, mean excess weight loss was 50%, and median BMI was 35. 4 patients have been reoperated so far (6.7%) due to slippage of the band (2 patients), infection of the band (1 patient), and leaking of the filling system (1 patient). Median postoperative hospital stay was 3 days (range 2-53). Mortality was 0%. Immediate postoperative mor- bidity-rate was 12% (7/60), although serious morbidity occurred in only 1 patient (1.7%). Conclusions: Laparoscopically placed adjustable gastric band is a good option for the morbidly obese patient.  相似文献   
997.
BACKGROUND: Outcomes of previous health economic evaluations comparing minilaparotomy cholecystectomy and laparoscopic cholecystectomy have been inconsistent. OBJECTIVE: To compare costs for minilaparotomy cholecystectomy and laparoscopic cholecystectomy and to study changes in quality of life induced by these operations. DESIGN: Single-blind, randomized controlled trial, run from 1 March 1997 to 30 April 1999. SETTING: One university hospital and four non-university hospitals in Sweden. MAIN MEASURE: : Cost and perceived health estimation according to the global quality of life instrument EuroQol-5D. RESULTS: Of 1719 cholecystectomy patients at five centres, 724 entered the trial and were treated with minilaparotomy cholecystectomy or laparoscopic cholecystectomy, 362 in each group. Total health care costs were less for minilaparotomy cholecystectomy than for laparoscopic cholecystectomy (median values US$2428 for minilaparotomy cholecystectomy versus US$2613 or US$3006 for laparoscopic cholecystectomy with 100 operations per year and reusable trocars or 50 operations per year and disposable trocars, respectively). There was no significant difference in total costs (including costs due to loss of production) between minilaparotomy cholecystectomy and laparoscopic cholecystectomy with 100 operations per year and reusable trocars in laparoscopic cholecystectomy (US$3731 versus US$3649, respectively). However, in calculations assuming 50 operations per year and disposable trocars in laparoscopic cholecystectomy, this technique was more expensive than minilaparotomy cholecystectomy (US$4042 versus US$3731). Health-related quality of life was slightly but significantly lower for the minilaparotomy cholecystectomy group 1 week after surgery. One month and 1 year postoperatively no difference between the randomized groups was found. CONCLUSION: Total costs did not differ between minilaparotomy cholecystectomy and laparoscopic cholecystectomy with high-volume surgery and disposable trocars, whereas laparoscopic cholecystectomy was more expensive with fewer operations and disposable trocars. The gain in health-related quality of life with laparoscopic cholecystectomy compared with minilaparotomy cholecystectomy was small and of limited duration.  相似文献   
998.
Pedram Sendi  MD  DSc    Maiwenn J. Al  PhD    Frans F. H. Rutten  PhD 《Value in health》2004,7(5):595-601
OBJECTIVES: Portfolio theory has been suggested as a means to improve the risk-return characteristics of investments in health-care programs through diversification when costs and effects are uncertain. This approach is based on the assumption that the investment proportions are not subject to uncertainty and that the budget can be invested in toto in health-care programs. METHODS: In the present paper we develop an algorithm that accounts for the fact that investment proportions in health-care programs may be uncertain (due to the uncertainty associated with costs) and limited (due to the size of the programs). The initial budget allocation across programs may therefore be revised at the end of the investment period to cover the extra costs of some programs with the leftover budget of other programs in the portfolio. RESULTS: Once the total budget is equivalent to or exceeds the expected costs of the programs in the portfolio, the initial budget allocation policy does not impact the risk-return characteristics of the combined portfolio, i.e., there is no benefit from diversification anymore. CONCLUSION: The applicability of portfolio methods to improve the risk-return characteristics of investments in health care is limited to situations where the available budget is much smaller than the expected costs of the programs to be funded.  相似文献   
999.
1000.
Abstract

Purpose: Autism spectrum disorder (ASD) includes core symptoms that affect general and social development. High risk of developing comorbid disorders such as anxiety is prominent. Up to 60% of children with ASD suffer from anxiety disorders which can negatively influence educational, social and general development together with quality of life. This study is the first to investigate the feasibility of the manualised cognitive behavioural therapy (CBT) group programme 'Cool Kids ASD' for anxiety adapted for children with ASD in a general hospital setting.

Methods: Nine children, aged 9–13 years, with ASD and anxiety recruited from a public child psychiatric health clinic were enrolled in the study. Outcome measures were collected from both child and parent pre- and post-treatment and at 3-month follow-up and included scores from a semi-structured anxiety interview, together with questionnaires on anxiety symptoms, life interference, children's automatic thoughts and satisfaction with the programme.

Results: Eight out of nine families found the programme useful and would recommend it to other families in a similar situation. Six families attended all 12 sessions in the programme, two missed one session and one family only managed to attend eight sessions. At follow-up, five children were free of all anxiety diagnoses and a further two out of the nine children no longer met the criteria for their primary anxiety diagnosis.

Conclusions: This study suggests that the transition of the group programme 'Cool Kids ASD' from University Clinics to standard child psychiatric clinical settings is feasible. Further randomised studies are needed to confirm the efficacy of the programme in a larger sample.  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