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   4722篇
  免费   352篇
  国内免费   25篇
耳鼻咽喉   26篇
儿科学   94篇
妇产科学   80篇
基础医学   759篇
口腔科学   100篇
临床医学   449篇
内科学   1013篇
皮肤病学   194篇
神经病学   631篇
特种医学   205篇
外科学   419篇
综合类   21篇
一般理论   5篇
预防医学   361篇
眼科学   62篇
药学   353篇
中国医学   7篇
肿瘤学   320篇
  2024年   2篇
  2023年   60篇
  2022年   117篇
  2021年   184篇
  2020年   139篇
  2019年   172篇
  2018年   198篇
  2017年   163篇
  2016年   174篇
  2015年   198篇
  2014年   213篇
  2013年   288篇
  2012年   428篇
  2011年   429篇
  2010年   262篇
  2009年   224篇
  2008年   343篇
  2007年   285篇
  2006年   284篇
  2005年   227篇
  2004年   183篇
  2003年   176篇
  2002年   130篇
  2001年   30篇
  2000年   20篇
  1999年   30篇
  1998年   38篇
  1997年   24篇
  1996年   20篇
  1995年   10篇
  1994年   6篇
  1993年   8篇
  1992年   5篇
  1991年   4篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1986年   2篇
  1984年   1篇
  1982年   4篇
  1980年   1篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1929年   2篇
  1924年   2篇
排序方式: 共有5099条查询结果,搜索用时 46 毫秒
71.
We present the nature of pathogenic SNP array findings in pregnancies without ultrasound (US) abnormalities and show the additional diagnostic value of SNP array as compared with rapid aneuploidy detection and karyotyping. 1,330 prenatal samples were investigated with a 0.5‐Mb SNP array after the exclusion of the most common aneuploidies. In 2.7% (36/1,330) of the cases, pathogenic chromosome aberrations were found; a microscopically detectable abnormality in 0.7% and a submicroscopic aberration in 2%. Our results show that in addition to the age‐ or screening‐related aneuploidy risk, in pregnancies without US abnormalities, there is a risk of 1:148 (9/1,330) for a (sub)microscopic abnormality associated with an early‐onset often severe disease, 1:222 (6/1,330) for a submicroscopic aberration causing an early‐onset disease, 1:74 (18/1,330) for carrying a susceptibility locus for a neurodevelopmental disorder, and 1:443 (3/1,330) for a late‐onset disorder (hereditary neuropathy with liability to pressure palsies in all three cases). These risk figures are important for adequate pretest counseling so that prospective parents can make informed individualized choices between targeted prenatal testing and broad testing with SNP array. Based on our results, we believe if invasive testing is performed, SNP array should be the preferred cytogenetic technique irrespective of the indication.  相似文献   
72.
Transplantation of neural stem cells (NSCs) appears to be a promising regenerative therapy for a variety of neurological disorders. Nevertheless, NSC engraftment is limited by the number of surviving cells. To maximize stem cell‐mediated effects, timing of implantation and cell number have to be precisely evaluated. Here, a transgenic murine NSC line was optimized for high expression levels of the imaging reporters Luc2 and copGFP. NSCs of 150 000, 75 000, 15 000 or 1500 cells or Hanks buffered salt solution were implanted into the striatum of nude mice. The survival of NSCs was monitored with in vivo bioluminescence imaging (BLI) over 2 weeks and brain sections were histologically analysed for glial cells of the innate immune system. The longitudinal in vivo BLI data revealed a significantly reduced viability with the highest rate for 150 000 engrafted NSCs. The cell loss was not correlated with the number of Iba‐1+ immune cells nor GFAP+ astrocytes. Histological quantification of copGFP+ cells at 14 days postimplantation confirmed the in vivo data with the highest density of copGFP+ cells in the 150 000‐cell graft and the highest survival rate for 1500 cells/graft. In conclusion, regenerative therapies should strictly evaluate the maximal number of stem cells to be transplanted in one location, as the results suggest that there is a critical limit of cells able to survive in the adult brain. Survival is limited by availability of oxygen and nutrients but not the inflammatory response induced by the implantation.  相似文献   
73.

Background:

Given that fine particulate matter (≤ 2.5 μm; PM2.5) is a mixture of multiple components, it has been of high interest to identify its specific health-relevant physical and/or chemical features.

Objectives:

We conducted a time-series study of PM2.5 and cardiorespiratory emergency department (ED) visits in the St. Louis, Missouri–Illinois metropolitan area, using 2 years of daily PM2.5 and PM2.5 component measurements (including ions, carbon, particle-phase organic compounds, and elements) made at the St. Louis-Midwest Supersite, a monitoring site of the U.S. Environmental Protection Agency Supersites ambient air monitoring research program.

Methods:

Using Poisson generalized linear models, we assessed short-term associations between daily cardiorespiratory ED visit counts and daily levels of 24 selected pollutants. Associations were estimated for interquartile range changes in each pollutant. To allow comparison of relationships among multiple pollutants and outcomes with potentially different lag structures, we used 3-day unconstrained distributed lag models controlling for time trends and meteorology.

Results:

Considering results of our primary models, as well as sensitivity analyses and models assessing co-pollutant confounding, we observed robust associations of cardiovascular disease visits with 17α(H),21β(H)-hopane and congestive heart failure visits with elemental carbon. We also observed a robust association of respiratory disease visits with ozone. For asthma/wheeze, associations were strongest with ozone and nitrogen dioxide; observed associations of asthma/wheeze with PM2.5 and its components were attenuated in two-pollutant models with these gases. Differential measurement error due to differential patterns of spatiotemporal variability may have influenced patterns of observed associations across pollutants.

Conclusions:

Our findings add to the growing field examining the health effects of PM2.5 components. Combustion-related components of the pollutant mix showed particularly strong associations with cardiorespiratory ED visit outcomes.

Citation:

Sarnat SE, Winquist A, Schauer JJ, Turner JR, Sarnat JA. 2015. Fine particulate matter components and emergency department visits for cardiovascular and respiratory diseases in the St. Louis, Missouri–Illinois, metropolitan area. Environ Health Perspect 123:437–444; http://dx.doi.org/10.1289/ehp.1307776  相似文献   
74.
75.
76.

Purpose

To test the effectiveness of a central venous catheter (CVC) insertion strategy and a hand hygiene (HH) improvement strategy to prevent central venous catheter-related bloodstream infections (CRBSI) in European intensive care units (ICUs), measuring both process and outcome indicators.

Methods

Adult ICUs from 14 hospitals in 11 European countries participated in this stepped-wedge cluster randomised controlled multicentre intervention study. After a 6 month baseline, three hospitals were randomised to one of three interventions every quarter: (1) CVC insertion strategy (CVCi); (2) HH promotion strategy (HHi); and (3) both interventions combined (COMBi). Primary outcome was prospective CRBSI incidence density. Secondary outcomes were a CVC insertion score and HH compliance.

Results

Overall 25,348 patients with 35,831 CVCs were included. CRBSI incidence density decreased from 2.4/1000 CVC-days at baseline to 0.9/1000 (p < 0.0001). When adjusted for patient and CVC characteristics all three interventions significantly reduced CRBSI incidence density. When additionally adjusted for the baseline decreasing trend, the HHi and COMBi arms were still effective. CVC insertion scores and HH compliance increased significantly with all three interventions.

Conclusions

This study demonstrates that multimodal prevention strategies aiming at improving CVC insertion practice and HH reduce CRBSI in diverse European ICUs. Compliance explained CRBSI reduction and future quality improvement studies should encourage measuring process indicators.
  相似文献   
77.

Background

The majority of Drug Treatment Court (DTC) research has examined the impact of DTCs on criminal recidivism. Comparatively little research has addressed the association between DTC participation and engagement with community-based health and social services. The present study investigated changes in participant involvement with outpatient healthcare and income assistance within a DTC cohort. We hypothesized that involvement with community-based (outpatient) health and social services would increase post-DTC participation, and that service levels would be higher among program graduates and offenders with histories of co-occurring mental and substance use disorders.

Methods

Participants were 631 offenders at the DTC in Vancouver, Canada (DTCV). Administrative data representing hospital, outpatient medical care, and income assistance were examined one-year pre/post program to assess differences over time. Generalized estimating equations were used to investigate the association between changes in service use and program involvement. We also examined the relationship between level of service use and offender characteristics.

Results

Members of the cohort were disproportionately Aboriginal (33 %), had been sentenced 2.7 times in the 2 years preceding their index offence, and 50 % had been diagnosed with a non substance-related mental disorder in the five years preceding the index offence. The mean number of outpatient services post DTCV was 51, and the mean amount of social assistance paid was $5,897. Outpatient service use increased following exposure to DTCV (Adjusted Rate Ratio (ARR)?=?1.45) and was significantly higher among women (ARR?=?1.47), program graduation (ARR?=?1.23), and those previously diagnosed with concurrent substance use and mental disorders (ARR?=?4.92). Overall, hospital admissions did not increase post-program, although rates were significantly higher among women (ARR?=?1.76) and those with concurrent disorders (ARR?=?2.71). Income assistance increased significantly post program (ARR?=?1.16), and was significantly higher among women (ARR?=?1.03), and those diagnosed with substance use disorders (ARR?=?1.42) and concurrent disorders (ARR?=?1.72).

Conclusions

These findings suggest that the DTCV was a catalyst for increased participant engagement with community health and social supports, and that rates of service use were consistently higher among women and individuals with concurrent disorders. Research is needed to investigate the potential link between health and social support and reductions in recidivism associated with DTCs.
  相似文献   
78.
Ebola virus disease (EVD) outbreaks have occurred during the past 5 decades, but none has affected European countries like the 2014 epidemic in West Africa. We used an online questionnaire to investigate risk perceptions in Germany during this epidemic peak. Our questionnaire covered risk perceptions, knowledge about transmission routes, media use, reactions to the outbreak, attitudes toward measures to prevent the spread of EVD and vaccination against EVD, and willingness to volunteer for aid missions. Of 974 participants, 29% indicated that they worried about EVD, 4% correctly stated virus transmission routes, and 75% incorrectly rated airborne transmission and transmission by asymptomatic patients as possible. Many indicated that if a patient were flown to Germany for treatment in a nearby hospital, they would adapt preventive behavior. Although most participants were not worried about EVD at the current stage of the epidemic, misperceptions regarding transmission were common and could trigger inappropriate behavior changes.  相似文献   
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