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   935篇
  免费   51篇
  国内免费   7篇
耳鼻咽喉   2篇
儿科学   24篇
妇产科学   22篇
基础医学   124篇
口腔科学   13篇
临床医学   60篇
内科学   220篇
皮肤病学   15篇
神经病学   89篇
特种医学   15篇
外科学   87篇
综合类   6篇
预防医学   99篇
眼科学   7篇
药学   146篇
中国医学   18篇
肿瘤学   46篇
  2023年   5篇
  2022年   17篇
  2021年   29篇
  2020年   12篇
  2019年   34篇
  2018年   30篇
  2017年   18篇
  2016年   25篇
  2015年   29篇
  2014年   46篇
  2013年   62篇
  2012年   76篇
  2011年   81篇
  2010年   62篇
  2009年   27篇
  2008年   57篇
  2007年   52篇
  2006年   63篇
  2005年   52篇
  2004年   44篇
  2003年   42篇
  2002年   43篇
  2001年   11篇
  2000年   8篇
  1999年   5篇
  1998年   3篇
  1997年   3篇
  1996年   6篇
  1995年   2篇
  1994年   5篇
  1993年   1篇
  1992年   7篇
  1991年   4篇
  1990年   4篇
  1989年   2篇
  1988年   4篇
  1987年   5篇
  1986年   3篇
  1985年   4篇
  1983年   2篇
  1981年   2篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1968年   2篇
排序方式: 共有993条查询结果,搜索用时 31 毫秒
1.
2.
BACKGROUND & AIMS: Many patients with chronic hepatitis C virus (HCV) have persistently normal serum alanine transaminase (ALT) levels. We compared characteristics of chronic hepatitis C patients with patients with normal and elevated ALT levels using data from 3 randomized phase III trials of peginterferon alfa-2a (40 kDa). METHODS: The characteristics of 480 patients with normal ALT values (on >or=3 occasions without any increases in ALT level over a 6- to 18-month period) and 1993 patients with elevated ALT levels were compared. Sixty-eight of the 480 patients with normal ALT levels were randomized to no treatment and monitored for 72 weeks. RESULTS: More patients with normal ALT levels than patients with elevated ALT levels were women (59% vs 32%; P<.01). The serum HCV RNA titer was significantly lower in patients with normal ALT levels (P<.01 vs in patients with elevated ALT levels). Patients with normal ALT levels had significantly lower inflammation and fibrosis scores on liver biopsy examination than patients with elevated ALT levels, but almost two-thirds had portal fibrosis and 10% had bridging fibrosis. No correlation between baseline ALT activity, HCV RNA level, and liver histology was observed in patients with normal ALT levels. During the 72-week follow-up period, ALT activity elevated above the upper limit of normal in 53% of the untreated patients with normal levels of ALT. None became HCV RNA undetectable. CONCLUSIONS: Chronic hepatitis C patients with normal ALT levels should be evaluated in a similar manner as patients with elevated ALT levels because they are at risk for developing significant liver disease. The decision to treat with peginterferon alfa and ribavirin should be based on multiple factors, rather than on ALT levels alone.  相似文献   
3.
Aims—To investigate whether proteoglycan synthesis is altered in skin fibroblasts in patients with Alzheimer's disease compared with normal subjects.  相似文献   
4.
5.
6.
7.
AIM:To investigate the geographic distributions and time trends of gastric cancer(GC)incidence and mortality in Brazil.METHODS:An ecological study of the DATASUS registry was conducted by identifying hospitalizations for GC between January 2005 and December 2010.The data included information on the gender,age,and town of residence at the time of hospital admission and death.RESULTS:The GC rates,adjusted according to available hospital beds,decreased from 13.8 per 100000in 2005 to 12.7 per 100000 in 2010.The GC rates decreased more among the younger age groups,in which the male-to-female difference also decreased in comparison to the older age groups.Although the lethality rates tended to increase with age,young patients were proportionally more affected.The spatial GC distribution showed that the rates were higher in the south and southeast.However,while the rates decreased in the central-west and south,they increased in the northern regions.A geographic analysis showed higher rates of GC in more urbanized areas,with a coast-toinland gradient.Geographically,GC lethality overlapped greatly with the hospital admission rates.CONCLUSION:The results of this study support the hypothesis of a critical role for environmental factors in GC pathogenesis.The declining rates in young patients,particularly males,suggest a relatively recent decrease in the exposure to risk factors associated with GC.The spatial distribution of GC indicates an ongoing dynamic change within the Brazilian environment.  相似文献   
8.
Azaspiracids (AZAs) are marine biotoxins produced by the dinoflagellate Azadinium spinosum that accumulate in several shellfish species. Azaspiracid poisoning episodes have been described in humans due to ingestion of AZA-contaminated seafood. Therefore, the contents of AZA-1, AZA-2 and AZA-3, the best-known analogs of the group, in shellfish destined to human consumption have been regulated by food safety authorities of many countries to protect human health. In vivo and in vitro toxicological studies have described effects of AZAs at different cellular levels and on several organs, however, AZA target remains unknown. Very recently, AZAs have been demonstrated to block the hERG cardiac potassium channel. In this study, we explored the potential cardiotoxicity of AZA-2 in vivo. The effects of AZA-2 on rat electrocardiogram (ECG) and cardiac biomarkers were evaluated for cardiotoxicity signs besides corroborating the hERG-blocking activity of AZA-2. Our results demonstrated that AZA-2 does not induce QT interval prolongation on rat ECGs in vivo, in spite of being an in vitro blocker of the hERG cardiac potassium channel. However, AZA-2 alters the heart electrical activity causing prolongation of PR intervals and the appearance of arrhythmias. More studies will be needed to clarify the mechanism by which AZA-2 causes these ECG alterations; however, the potential cardiotoxicity of AZAs demonstrated in this in vivo study should be taken into consideration when evaluating the possible threat that these toxins pose to human health, mainly for individuals with pre-existing cardiovascular disease when regulated toxin limits are exceeded.  相似文献   
9.
10.
Objective. To analyze risk factors for Pneumocystis carinii pneumonia (PCP) in kidney transplant recipients. Study design. In a case–control study, 17 PCP cases diagnosed between July 1994 and July 2000 were matched with two controls each (previous and subsequent kidney transplant recipients who did not develop PCP during the same follow‐up period). Demographics, organ origin, human leukocyte antigen (HLA) mismatches, use of poly‐ or monoclonal anti‐CD3 antibodies (Po/MoAb) for induction or rejection treatment, rejection episodes, cumulative steroid dose for rejection treatment, immunosuppressive regimens, and other infections were analyzed. Results. No significant differences were seen in gender (male 10 vs. 15), mean age (39.7 vs. 35.4 years), organ origin (cadaver donor 13 vs. 19), HLA mismatches, or Po/MoAb use in induction treatment. Significant differences were observed in PCP cases for rejection history (P=0.02), and median and total number of rejection episodes (P=0.0018). The relative risks for PCP for 1, 2, and ≥3 rejection treatments vs. no such treatment were 1, 1.05, and 6.30, respectively (P=0.021). The relative risk for PCP for steroid‐resistant rejection was 4.34 (95% confidence interval [CI], 1.04–18.89) (P=0.019), and that for the use of Po/MoAb for rejection treatment was 7.23 (95% CI, 1.28–49.34) (P=0.006). The relative risk for PCP for 0, 1, and ≥2 previous or concomitant cytomegalovirus (CMV) infection vs. no such infections were 1.0, 2.32, and 13.0, respectively (P=0.012). The relative risks for PCP for tuberculosis (TB) was 18 (95% CI, 1.76–852.03), that for bacterial pneumonia was 14.22 (95% CI, 2.16–150.23), and that for hepatitis C virus infection was 5.25 (95% CI, 1.03–28.91). Immunosuppressive regimens with tacrolimus, mycophenolate mofetil (MMF), steroids (P=0.06), and MMF as a single variable (P=0.05) were more frequently used in cases. Primary trimethoprim‐sulfamethoxazole prophylaxis failure was observed in 12 patients in association with heavy immunosuppression and concomitant infections. Conclusions. The risk of PCP in kidney transplant recipients is related to the number and type of rejection treatments. It is also related to the occurrence of CMV infection, and to other immunomodulating infections such as TB and hepatitis C, and might also be increased with the use of newer and more potent immunosuppressive agents. Primary prophylaxis failure may occur in association with some of these risk factors.  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