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   21885篇
  免费   1783篇
  国内免费   71篇
耳鼻咽喉   173篇
儿科学   615篇
妇产科学   714篇
基础医学   3235篇
口腔科学   293篇
临床医学   2141篇
内科学   4431篇
皮肤病学   762篇
神经病学   2371篇
特种医学   727篇
外科学   2350篇
综合类   163篇
一般理论   3篇
预防医学   2049篇
眼科学   458篇
药学   1478篇
中国医学   63篇
肿瘤学   1713篇
  2023年   198篇
  2022年   241篇
  2021年   616篇
  2020年   426篇
  2019年   607篇
  2018年   592篇
  2017年   500篇
  2016年   552篇
  2015年   582篇
  2014年   713篇
  2013年   1130篇
  2012年   1508篇
  2011年   1496篇
  2010年   833篇
  2009年   725篇
  2008年   1229篇
  2007年   1193篇
  2006年   1153篇
  2005年   1024篇
  2004年   1023篇
  2003年   908篇
  2002年   862篇
  2001年   366篇
  2000年   379篇
  1999年   376篇
  1998年   225篇
  1997年   160篇
  1996年   158篇
  1995年   156篇
  1994年   143篇
  1993年   126篇
  1992年   242篇
  1991年   262篇
  1990年   220篇
  1989年   247篇
  1988年   222篇
  1987年   216篇
  1986年   174篇
  1985年   196篇
  1984年   168篇
  1983年   126篇
  1982年   118篇
  1981年   99篇
  1980年   79篇
  1979年   121篇
  1978年   98篇
  1977年   97篇
  1975年   78篇
  1974年   82篇
  1973年   78篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
The retroviral protease of human immunodeficiency virus (HIV) is an excellent target for antiviral inhibitors for treating HIV/AIDS. Despite the efficacy of therapy, current efforts to control the disease are undermined by the growing threat posed by drug resistance. This review covers the historical background of studies on the structure and function of HIV protease, the subsequent development of antiviral inhibitors, and recent studies on drug-resistant protease variants. We highlight the important contributions of Dr. Stephen Oroszlan to fundamental knowledge about the function of the HIV protease and other retroviral proteases. These studies, along with those of his colleagues, laid the foundations for the design of clinical inhibitors of HIV protease. The drug-resistant protease variants also provide an excellent model for investigating the molecular mechanisms and evolution of resistance.  相似文献   
5.
6.
Background: Egyptian street youth use substances including tobacco, illicit drugs, and pharmaceutical drugs. To understand the circumstances, including adverse childhood experiences, that place adolescents at risk for engaging in substance use, we conducted in-depth interviews among a sample of Egyptian street children. Methods: From youth residing at or attending Caritas, a non-profit organization, which provides shelter and education to street youth, seven girls and twelve boys, aged 12–18 years, participated in open-ended, in-depth interviews. Results: Eight out of the 19 participants reported family history (early exposure) to substance use; and seven of them were initiated by either a family member (sibling), friend or coworker. Most of the participants reported a history of conflict with or abuse (verbal or physical) by their parents or siblings, or stressful situations at home; they used substance(s) to alleviate their stress. Few attended school, and some were forced to work and help their family. Conclusions: Among Egyptian youth, adverse childhood experiences, such as poverty, child abuse, and family substance use, challenge somewhat susceptible youths and lead them to the path of substance use and addiction. Prevention intervention should be multifaceted, culturally adaptable, and primarily targeting the social environment during childhood.  相似文献   
7.
8.
9.

Objectives

Short successive periods of skeletal muscle disuse have been suggested to substantially contribute to the observed loss of skeletal muscle mass over the life span. Hospitalization of older individuals due to acute illness, injury, or major surgery generally results in a mean hospital stay of 5 to 7 days, during which the level of physical activity is strongly reduced. We hypothesized that hospitalization following elective total hip arthroplasty is accompanied by substantial leg muscle atrophy in older men and women.

Design and participants

Twenty-six older patients (75 ± 1 years) undergoing elective total hip arthroplasty participated in this observational study.

Measurements

On hospital admission and on the day of discharge, computed tomographic (CT) scans were performed to assess muscle cross-sectional area (CSA) of both legs. During surgery and on the day of hospital discharge, a skeletal muscle biopsy was taken from the m. vastus lateralis of the operated leg to assess muscle fiber type–specific CSA.

Results

An average of 5.6 ± 0.3 days of hospitalization resulted in a significant decline in quadriceps (?3.4% ± 1.0%) and thigh muscle CSA (?4.2% ± 1.1%) in the nonoperated leg (P < .05). Edema resulted in a 10.3% ± 1.7% increase in leg CSA in the operated leg (P < .05). At hospital admission, muscle fiber CSA was smaller in the type II vs type I fibers (3326 ± 253 μm2 vs 4075 ± 279 μm2, respectively; P < .05). During hospitalization, type I and II muscle fiber CSA tended to increase, likely due to edema in the operated leg (P = .10).

Conclusions

Six days of hospitalization following elective total hip arthroplasty leads to substantial leg muscle atrophy in older patients. Effective intervention strategies are warranted to prevent the loss of muscle mass induced by short periods of muscle disuse during hospitalization.  相似文献   
10.
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