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   237030篇
  免费   17797篇
  国内免费   6565篇
耳鼻咽喉   3008篇
儿科学   3829篇
妇产科学   4867篇
基础医学   33530篇
口腔科学   4694篇
临床医学   25599篇
内科学   41983篇
皮肤病学   5193篇
神经病学   16137篇
特种医学   10857篇
外国民族医学   53篇
外科学   29877篇
综合类   12906篇
现状与发展   26篇
一般理论   100篇
预防医学   14601篇
眼科学   7187篇
药学   21460篇
  67篇
中国医学   5644篇
肿瘤学   19774篇
  2023年   2177篇
  2022年   5786篇
  2021年   8687篇
  2020年   5389篇
  2019年   6303篇
  2018年   7313篇
  2017年   5610篇
  2016年   6598篇
  2015年   9136篇
  2014年   11247篇
  2013年   12100篇
  2012年   18238篇
  2011年   18333篇
  2010年   10987篇
  2009年   8882篇
  2008年   13162篇
  2007年   12913篇
  2006年   12325篇
  2005年   11789篇
  2004年   9686篇
  2003年   8531篇
  2002年   7298篇
  2001年   6124篇
  2000年   5757篇
  1999年   5285篇
  1998年   2579篇
  1997年   2237篇
  1996年   1899篇
  1995年   1752篇
  1994年   1510篇
  1993年   1116篇
  1992年   2162篇
  1991年   2059篇
  1990年   1818篇
  1989年   1641篇
  1988年   1518篇
  1987年   1319篇
  1986年   1257篇
  1985年   1091篇
  1984年   772篇
  1983年   646篇
  1982年   440篇
  1981年   427篇
  1980年   363篇
  1979年   580篇
  1978年   428篇
  1977年   399篇
  1976年   355篇
  1974年   385篇
  1973年   345篇
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
71.
本研究拟探讨染料木黄酮对前列腺癌细胞LNCaP和CWR22RV1的增殖、迁移和侵袭能力的影响。一、材料与方法1.材料:前列腺癌细胞株LNCaP和CWR22RV1(中国科学院上海生命科学研究院);Genistein(天津科瑞泰科技有限公司);RPMI 1640、胎牛血清(FBS)、胰蛋白酶(美国Gibco公司);E-钙黏蛋白(E-cadherin)、N-钙黏蛋白(N-cadherin)、波形蛋白(Vimentin,Abcam公司);聚氰基丙烯酸正丁酯(BCA)试剂盒、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)上样缓冲液(×5)及蛋白质印迹法(Western blot)试剂盒(上海市碧云天生物公司);2.实验方法:采用噻唑蓝(MTT)实验、划痕实验和Transwell实验检测Genistein对细胞增殖、迁移及侵袭能力的影响。采用Western blot检测E-cadherin、N-cadherin、Vimentin、CD44和Oct-4的表达水平。  相似文献   
72.

Background

Bone mineral density (BMD) has been found to improve after parathyroidectomy (PTX) in patients with primary hyperparathyroidism. There are few data on the effect of PTX on BMD in normocalcemic and normohormonal primary hyperparathyroidism.

Methods

A retrospective analysis of 92 primary hyperparathyroidism patients who underwent PTX between 2004 and 2012 with pre- and post-PTX dual-energy x-ray absorptiometry was performed. Within-person changes in BMD pre- and post-PTX were analyzed using log linear mixed models, stratified by biochemical status.

Results

Bone mineral density increased post-PTX in the whole cohort at the lumbar spine (+2.5%), femoral neck (+2.1%), and total hip (+1.9%) and decreased at the one-third radius (–0.9%). On comparison of BMD changes by profile, BMD increased in those with the typical profile at the lumbar spine (3.2%), femoral neck (2.9%), and total hip (2.9%) but declined at the one-third radius (–1.5%). In contrast, BMD improved only at the femoral neck (4.3%) in the normohormonal group and did not change at any site in the normocalcemic group. The typical group had a greater increase in BMD over time at the femoral neck and total hip compared with normocalcemic patients.

Conclusion

Our results indicate that the skeletal benefit of PTX was attenuated in normocalcemic and normohormonal patients, suggesting that skeletal changes after PTX may depend on biochemical profile.  相似文献   
73.
74.

Introduction

For never-smokers (smoked <100 lifetime cigarettes), lung cancer (LC) has emerged as an important issue. We aimed to investigate the effects of prevalence changes in tobacco smoking and particulate matter (PM) 2.5 (PM2.5) levels on LC in Taiwan, in relation to contrasting PM2.5 levels, between Northern Taiwan (NT) and Southern Taiwan (ST).

Methods

We reviewed 371,084 patients with LC to assess smoking prevalence and correlations between the incidence of adenocarcinoma lung cancer (AdLC) and non-AdLC. Two subsets were selected to assess different AdLC stage trends and the effect of PM2.5 on survival of patients with AdLC.

Results

From 1995 to 2015, the proportion of male adult ever-smokers decreased from 59.4% to 29.9% whereas the female smoking rate remained low (3.2% to 5.3%). AdLC incidence in males and females increased from 9.06 to 23.25 and 7.05 to 24.22 per 100,000 population, respectively. Since 1993, atmospheric visibility in NT improved (from 7.6 to 11.5 km), but deteriorated in ST (from 16.3 to 4.2 km). The annual percent change in AdLC stages IB to IV was 0.3% since 2009 (95% confidence interval [CI]: -1.9%–2.6%) in NT, and 4.6% since 2007 (95% CI: 3.3%–5.8%) in ST; 53% patients with LC had never smoked. Five-year survival rates for never-smokers, those with EGFR wild-type genes, and female patients with AdLC were 12.6% in NT and 4.5% in ST (hazard ratio: 0.79, 95% CI: 0.70–0.90).

Conclusions

In Taiwan, greater than 50% of patients with LC had never smoked. PM2.5 level changes can affect AdLC incidence and patient survival.  相似文献   
75.
76.
77.

Background

Observational studies of the relative effectiveness of influenza vaccines are essential for public health decision making. Their estimates, however, are subject to bias due to unmeasured confounders. Instrumental variable (IV) methods can control for observed and unobserved confounders.

Methods

We used linked electronic medical record databases in the Veterans Health Administration (VHA) as well as Medicare administrative files to examine the relative vaccine effectiveness (rVE) of high-dose influenza vaccine (HD) versus standard-dose influenza vaccines (SD) in preventing hospitalizations among VHA-enrolled Veterans ≥65?years of age during 5 influenza seasons (2010–2011 through 2014–2015). Using multivariable IV Poisson regression modeling to address unmeasured confounding and bias, we analyzed the data by each season and through longitudinal analysis of all five seasons.

Findings

We included 3,638,924 person–influenza seasons of observation where 158,636 (4%) were among HD vaccine recipients and 3,480,288 (96%) were among SD vaccine recipients. Of the 1,728,562 Veterans, 1,702,824 (98.5%) were male and 1,299,412 (75%) were non-Hispanic white. Based on the longitudinal analysis of all five seasons, the IV-adjusted rVE estimate of HD vs. SD was 10% (95% CI, 8–12%) against all-cause hospitalization; 18% (95% CI, 15–21%) against cardiorespiratory-associated hospitalization; and 14% (95% CI, 6–22%) against influenza/pneumonia-associated hospitalization. The findings by season were similar.

Interpretation

Our analysis of VHA clinical data collected from approximately 1.7 million Veterans 65?years and older during five seasons demonstrates that high-dose influenza vaccine is more effective than standard-dose influenza vaccines in preventing influenza- or pneumonia-associated hospitalizations, cardiorespiratory hospitalizations, and all-cause hospitalizations.  相似文献   
78.

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   
79.
It is hypothesized that persons who use drugs (PWUD) in Vietnam who are also HIV-positive may face additional challenges in psychosocial outcomes, and these challenges may extend to their family members. In this study, we examined depressive symptoms, stigma, social support, and caregiver burden of HIV-positive PWUD and their family members, compared to the outcomes of HIV-negative PWUD and their family members. Baseline, 3-month, and 6-month assessment data were gathered from 83 PWUD and 83 family members recruited from four communes in Phú Th? Province, Vietnam. For PWUD, although we observed a general decline in overall stigma over time for both groups, HIV-positive PWUD consistently reported significantly higher overall stigma for all three periods. Depressive symptoms among family members in both groups declined over time; however, family members of HIV-positive PWUD reported higher depressive symptoms across all three periods. In addition, family members of HIV-positive PWUD reported lower levels of tangible support across all three periods. Caregiver burden among family members of HIV-positive PWUD increased significantly over time, whereas the reported burden among family members of HIV-negative PWUD remained relatively unchanged. The findings highlight the need for future interventions for PWUD and family members, with targeted and culturally specific strategies to focus on the importance of addressing additional stigma experienced by PWUD who are HIV-positive. Such challenges may have direct negative impact on their family members' depressive symptoms, tangible support, and caregiver burden.  相似文献   
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