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   3333篇
  免费   429篇
  国内免费   4篇
耳鼻咽喉   7篇
儿科学   114篇
妇产科学   43篇
基础医学   182篇
口腔科学   68篇
临床医学   274篇
内科学   441篇
皮肤病学   19篇
神经病学   69篇
特种医学   168篇
外科学   186篇
综合类   19篇
一般理论   1篇
预防医学   1934篇
眼科学   18篇
药学   121篇
肿瘤学   102篇
  2023年   31篇
  2022年   51篇
  2021年   32篇
  2020年   95篇
  2019年   31篇
  2018年   105篇
  2017年   108篇
  2016年   107篇
  2015年   99篇
  2014年   98篇
  2013年   192篇
  2012年   66篇
  2011年   61篇
  2010年   134篇
  2009年   137篇
  2008年   68篇
  2007年   73篇
  2006年   109篇
  2005年   74篇
  2004年   74篇
  2003年   54篇
  2002年   108篇
  2001年   113篇
  2000年   88篇
  1999年   159篇
  1998年   164篇
  1997年   199篇
  1996年   212篇
  1995年   134篇
  1994年   62篇
  1993年   130篇
  1992年   43篇
  1991年   36篇
  1990年   28篇
  1989年   51篇
  1988年   48篇
  1987年   36篇
  1986年   49篇
  1985年   33篇
  1984年   30篇
  1983年   24篇
  1982年   25篇
  1981年   22篇
  1980年   14篇
  1979年   17篇
  1978年   13篇
  1977年   14篇
  1976年   24篇
  1975年   12篇
  1971年   10篇
排序方式: 共有3766条查询结果,搜索用时 15 毫秒
71.
Histamine depressed lymphocyte reactivity to phytohemagglutinin and, to a lesser degree, concanavalin A, when administered simultaneously with mitogen to lymphocyte cultures. Addition of histamine at later times to the cultures appeared to have a slightly enhancing effect on the lymphocyte response. Stimulation of lymphocytes with pokeweed mitogen was in some cases enhanced, even by high concentrations of histamine. Lymphocytes from atopic individuals were more sensitive to the inhibitory effect of histamine than lymphocytes from nonatopic individuals. The sensitivity appeared age-dependent, but within each age group histamine evoked significantly more suppression on lymphocytes from atopic than from nonatopic individuals. The possibility that the altered reactivity of lymphocytes to histamine, which appears to be associated with atopic allergy, is of pathogenic importance, is discussed, and a hypothesis for the development of atopic disease is proposed.  相似文献   
72.
Immunoglobulin G (IgG) and T-cell-derived antigen binding molecules (TABM) specific to whole Candida extract and to Candida-derived mannans prepared by both the cetryltrimethylammonium bromide (CTAB) and alkaline degradation (PEAT) methods were measured in the sera of women with vulvovaginal candidiasis and controls. In the patients there were significantly higher levels of IgG to both CTAB and PEAT mannans and of TABM to CTAB mannan. TABM specific to CTAB mannan was purified from the serum of a patient with a high titer of this TABM. The purified TABM bound specifically to CTAB mannan and to other yeast and mold extracts. This TABM preparation was associated with transforming growth factor beta2 (TGF-beta2), and on specific binding to mannan there was a marked increase in the level of detectable TGF-beta2. This increase in TGF-beta2 level was critically dependent on the relative concentrations of the purified TABM and mannan, being smallest when either was in excess. The TABM specific to CTAB mannan was also shown to inhibit Candida-stimulated gamma interferon production. The results suggest that CTAB mannan-specific TABM may increase susceptibility to vulvovaginal candidiasis in association with a shift in the immune response to the Th2 type.  相似文献   
73.
74.
75.
76.
77.
Impaired nutrition status is recognized as a risk factor for worse clinical outcomes in patients with chronic obstructive pulmonary disease (COPD). The aims of this study were to investigate how undernutrition is diagnosed, its prevalence, and whether there is an association between this condition and clinical outcomes in patients with COPD. The search for this systematic review of observational studies (PROSPERO: CRD42020191888) was performed in the PubMed, Embase, and Scopus databases, with no date or language restrictions. The studies had to report data on the diagnosis of undernutrition and its association with mortality, exacerbation, length of hospital stay, or quality of life in adult patients with COPD. A meta-analysis with a random-effects model was performed to combine data. Forty-nine studies were included (20 of them classified as having a low risk of bias), and the most common diagnostic method of undernutrition was body mass index (BMI) (n = 36). The pooled prevalence of undernutrition was equal to 20% (95% CI, 0.15–0.25; I² = 100%), and it was associated with mortality (risk ratio = 1.97; 95% CI, 1.55–2.50; I² = 98%), exacerbation (risk ratio = 1.73; 95% CI, 1.03–2.91; I² = 96%), and poorer quality of life (mean difference = 8.25; 95% CI, 5.40–11.10; I² = 79%). For all outcomes, the certainty of evidence was very low. In conclusion, undernutrition is prevalent and is associated with poorer outcomes in patients with COPD. However, undernutrition is mainly diagnosed by BMI, which underreports its prevalence, and the certainty of the evidence is very low.  相似文献   
78.
79.
80.
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