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   235332篇
  免费   14842篇
  国内免费   989篇
耳鼻咽喉   2524篇
儿科学   5990篇
妇产科学   4417篇
基础医学   29329篇
口腔科学   4321篇
临床医学   24060篇
内科学   49635篇
皮肤病学   3226篇
神经病学   23664篇
特种医学   10113篇
外国民族医学   13篇
外科学   37012篇
综合类   2537篇
现状与发展   1篇
一般理论   177篇
预防医学   16546篇
眼科学   5549篇
药学   15487篇
  1篇
中国医学   319篇
肿瘤学   16242篇
  2023年   1335篇
  2022年   2192篇
  2021年   5336篇
  2020年   3043篇
  2019年   5052篇
  2018年   6050篇
  2017年   4442篇
  2016年   4849篇
  2015年   5731篇
  2014年   8348篇
  2013年   11243篇
  2012年   17279篇
  2011年   18011篇
  2010年   10067篇
  2009年   9311篇
  2008年   15865篇
  2007年   16657篇
  2006年   16199篇
  2005年   16059篇
  2004年   15104篇
  2003年   13788篇
  2002年   13184篇
  2001年   1930篇
  2000年   1431篇
  1999年   2007篇
  1998年   2784篇
  1997年   2212篇
  1996年   1924篇
  1995年   1761篇
  1994年   1527篇
  1993年   1495篇
  1992年   982篇
  1991年   929篇
  1990年   793篇
  1989年   753篇
  1988年   680篇
  1987年   626篇
  1986年   646篇
  1985年   682篇
  1984年   911篇
  1983年   788篇
  1982年   1035篇
  1981年   965篇
  1980年   835篇
  1979年   465篇
  1978年   517篇
  1977年   448篇
  1976年   419篇
  1975年   314篇
  1974年   313篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.

Objective

To determine whether differences in combination DTaP vaccine types at 2, 4 and 6?months of age were associated with mortality (all-cause or non-specific), within 30?days of vaccination.

Design

Observational nationwide cohort study.

Setting

Linked population data from the Australian Childhood Immunisation Register and National Death Index.

Participants

Australian infants administered a combination trivalent, quadrivalent or hexavalent DTaP vaccine (DTaP types) between January 1999 and December 2010 at 2, 4 and 6?months as part of the primary vaccination series. The study population included 2.9, 2.6, & 2.3?million children in the 2, 4 and 6?month vaccine cohorts, respectively.

Main outcome measures

Infants were evaluated for the primary outcome of all-cause mortality within 30?days. A secondary outcome was non-specific mortality (unknown cause of death) within 30?days of vaccination. Non-specific mortality was defined as underlying or other cause of death codes, R95 ‘Sudden infant death syndrome’, R96 ‘Other sudden death, cause unknown’, R98 ‘Unattended death’, R99 ‘Other ill-defined and unspecified cause of mortality’ or where no cause of death was recorded.

Results

The rate of 30?day all-cause mortality was low and declined from 127.4 to 59.3 deaths per 100,000 person-years between 2 and 6?month cohorts. When compared with trivalent DTaP vaccines, no elevated risk in all-cause or non-specific mortality was seen with any quadrivalent or hexavalent DTaP vaccines, for any cohort.

Conclusion

Use of routine DTaP combination vaccines with differing disease antigens administered during the first six months of life is not associated with infant mortality.  相似文献   
22.

Background

The optimal noninvasive test (NIT) for patients with diabetes and stable symptoms of coronary artery disease (CAD) is unknown.

Objectives

The purpose of this study was to assess whether a diagnostic strategy based on coronary computed tomographic angiography (CTA) is superior to functional stress testing in reducing adverse cardiovascular (CV) outcomes (CV death or myocardial infarction [MI]) among symptomatic patients with diabetes.

Methods

PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) was a randomized trial evaluating an initial strategy of CTA versus functional testing in stable outpatients with symptoms suggestive of CAD. The study compared CV outcomes in patients with diabetes (n = 1,908 [21%]) and without diabetes (n = 7,058 [79%]) based on their randomization to CTA or functional testing.

Results

Patients with diabetes (vs. without) were similar in age (median 61 years vs. 60 years) and sex (female 54% vs. 52%) but had a greater burden of CV comorbidities. Patients with diabetes who underwent CTA had a lower risk of CV death/MI compared with functional stress testing (CTA: 1.1% [10 of 936] vs. stress testing: 2.6% [25 of 972]; adjusted hazard ratio: 0.38; 95% confidence interval: 0.18 to 0.79; p = 0.01). There was no significant difference in nondiabetic patients (CTA: 1.4% [50 of 3,564] vs. stress testing: 1.3% [45 of 3,494]; adjusted hazard ratio: 1.03; 95% confidence interval: 0.69 to 1.54; p = 0.887; interaction term for diabetes p value = 0.02).

Conclusions

In diabetic patients presenting with stable chest pain, a CTA strategy resulted in fewer adverse CV outcomes than a functional testing strategy. CTA may be considered as the initial diagnostic strategy in this subgroup. (PROspective Multicenter Imaging Study for Evaluation of Chest Pain [PROMISE]; NCT01174550)  相似文献   
23.
24.
25.
26.
ABSTRACT

Objectives: The present study investigated the relationships of enculturation and depressive symptoms with health risk behavior engagement in Mexican-American college students and examined how these relationships differed by gender. Previous research has noted consistent gender differences in health risk behavior (e.g. alcohol use, substance use, and risky sexual behavior) among Latina/os, and emphasized the role of U.S. acculturation in this difference. Research examining the role of heritage cultural retention (i.e. enculturation), and including the added influence of mental health variables, such as depressive symptoms, is currently lacking. This study sought to address this gap.

Design: A large sample (N?=?677) of Mexican-American college students from four universities (located in New York, California, Florida, and Texas) completed an online questionnaire assessing health risk behaviors and corresponding variables.

Results: We found that males who endorsed more behavioral enculturation and depressive symptoms were more likely to engage in health risk behavior than all others in the sample. Contrary to previous literature, no relationship was found between behavioral enculturation and health risk behavior in females.

Conclusion: The current study found behavioral enculturation to be associated with depressive symptoms, and in turn with health risk behaviors among the males in our sample. Additional research will be needed to identify the mechanism underlying the relationship between enculturation and depressive symptoms as well as between depressive symptoms and risky behavior.  相似文献   
27.
28.
29.
30.
HIV risk in vulnerable groups such as itinerant male street labourers is often examined via a focus on individual determinants. This study provides a test of a modified Information-Motivation-Behavioral Skills (IMB) model to predict condom use behaviour among male street workers in urban Vietnam. In a cross-sectional survey using a social mapping technique, 450 male street labourers from 13 districts of Hanoi, Vietnam were recruited and interviewed. Collected data were first examined for completeness; structural equation modelling was then employed to test the model fit. Condoms were used inconsistently by many of these men, and usage varied in relation to a number of factors. A modified IMB model had a better fit than the original IMB model in predicting condom use behaviour. This modified model accounted for 49% of the variance, versus 10% by the original version. In the modified model, the influence of psychosocial factors was moderately high, whilst the influence of HIV prevention information, motivation and perceived behavioural skills was moderately low, explaining in part the limited level of condom use behaviour. This study provides insights into social factors that should be taken into account in public health planning to promote safer sexual behaviour among Asian male street labourers.  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