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   893796篇
  免费   73429篇
  国内免费   1923篇
耳鼻咽喉   13362篇
儿科学   25619篇
妇产科学   25736篇
基础医学   128173篇
口腔科学   25980篇
临床医学   78616篇
内科学   169840篇
皮肤病学   17405篇
神经病学   73253篇
特种医学   36587篇
外国民族医学   171篇
外科学   142142篇
综合类   25308篇
一般理论   302篇
预防医学   69359篇
眼科学   20949篇
药学   67242篇
中国医学   1625篇
肿瘤学   47479篇
  2018年   8348篇
  2015年   8689篇
  2014年   12478篇
  2013年   18616篇
  2012年   25832篇
  2011年   26995篇
  2010年   15609篇
  2009年   14641篇
  2008年   25223篇
  2007年   27324篇
  2006年   27118篇
  2005年   26799篇
  2004年   25999篇
  2003年   25047篇
  2002年   23961篇
  2001年   36103篇
  2000年   36586篇
  1999年   30948篇
  1998年   9050篇
  1997年   8210篇
  1996年   8056篇
  1995年   8224篇
  1994年   7897篇
  1992年   26814篇
  1991年   26266篇
  1990年   25730篇
  1989年   24785篇
  1988年   23338篇
  1987年   22975篇
  1986年   21830篇
  1985年   21184篇
  1984年   16465篇
  1983年   14045篇
  1982年   8949篇
  1981年   8282篇
  1980年   7715篇
  1979年   16755篇
  1978年   12130篇
  1977年   10191篇
  1976年   9318篇
  1975年   10131篇
  1974年   12620篇
  1973年   12133篇
  1972年   11534篇
  1971年   10684篇
  1970年   10209篇
  1969年   9901篇
  1968年   8902篇
  1967年   8239篇
  1966年   7648篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4 weeks (TM perforations had fully sealed after 2 weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10 dB) at low frequencies and more dramatic loss at high frequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.  相似文献   
2.
3.
AIDS and Behavior - Transactional sex increases HIV risk among adolescent girls and young women (AGYW). Understanding the individual and dyadic nature of transactional sex may provide evidence for...  相似文献   
4.
5.
6.
7.
Purpose

To examine cross-sectional associations between food insecurity and 12-month eating disorders, mood disorders, and anxiety disorders among U.S. adults.

Methods

This study used data collected between 2001 and 2003 from 2914 participants in the National Comorbidity Survey-Replication, a nationally representative sample of U.S. adults (mean age = 44.9 years; 53.4% female). Twelve-month food insecurity was assessed with a modified version of the Short Form U.S. Household Food Security Scale. Twelve-month DSM-IV diagnoses of mental disorders were based on the World Health Organization Composite International Diagnostic Interview. Modified Poisson regression models were conducted, adjusting for age, sex, race/ethnicity, education, and income-to-poverty ratio.

Results

Food insecurity was experienced by 11.1% of participants. Food insecurity was associated with greater prevalence of bulimic-spectrum eating disorders (prevalence ratio [PR] = 3.81; 95% confidence interval [CI] 2.26–6.42), mood disorders (PR = 2.53; 95% CI 1.96–3.29), and anxiety disorders (PR = 1.69; 95% CI 1.39–2.07).

Conclusion

Results indicate that food insecurity is associated with a range of internalizing mental disorders, though these findings should be confirmed with contemporary data to reflect DSM-5 diagnostic updates and the economic effects of the COVID-19 pandemic. Findings from this study emphasize the need to expand food insecurity interventions and improve access to mental health services for food-insecure populations.

  相似文献   
8.
9.
10.
Breast Cancer Research and Treatment - The NSABP B-36 compared four cycles of doxorubicin and cyclophosphamide (AC) with six cycles of 5-fluorouracil, epirubicin, and cyclophosphamide (FEC-100) in...  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