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   1502篇
  免费   95篇
  国内免费   33篇
  2023年   5篇
  2022年   23篇
  2021年   53篇
  2020年   12篇
  2018年   23篇
  2017年   20篇
  2016年   44篇
  2015年   109篇
  2014年   197篇
  2013年   216篇
  2012年   127篇
  2011年   73篇
  2010年   80篇
  2009年   72篇
  2008年   61篇
  2007年   26篇
  2006年   19篇
  2005年   55篇
  2004年   39篇
  2003年   28篇
  2002年   32篇
  2001年   27篇
  2000年   20篇
  1999年   11篇
  1998年   11篇
  1997年   8篇
  1996年   14篇
  1993年   10篇
  1992年   9篇
  1991年   9篇
  1990年   10篇
  1989年   10篇
  1988年   11篇
  1986年   7篇
  1985年   4篇
  1983年   5篇
  1982年   5篇
  1979年   4篇
  1974年   4篇
  1973年   5篇
  1972年   5篇
  1968年   5篇
  1965年   4篇
  1962年   4篇
  1961年   4篇
  1960年   4篇
  1957年   6篇
  1951年   5篇
  1926年   4篇
  1923年   3篇
排序方式: 共有1630条查询结果,搜索用时 15 毫秒
941.

Background

Reliance on national figures may be underestimating the extent of mental ill health in urban communities. This study demonstrates the necessity for local information on common mental disorder (CMD) and substance use by comparing data from the South East London Community Health (SELCoH) study with those from a national study, the 2007 English Adult Psychiatric Morbidity Study (APMS).

Methodology/Principal Findings

Data were used from two cross-sectional surveys, 1698 men and women residing in south London and 7403 men and women in England. The main outcome, CMD, was indicated by a score of 12 or above on the Revised Clinical Interview Schedule. Secondary outcomes included hazardous alcohol use and illicit drug use. SELCoH sample prevalence estimates of CMD were nearly twice that of the APMS England sample estimates. There was a four-fold greater proportion of depressive episode in the SELCoH sample than the APMS sample. The prevalence of hazardous alcohol use was higher in the national sample. Illicit drug use in the past year was higher in the SELCoH sample, with cannabis and cocaine the illicit drugs reported most frequently in both samples. In comparisons of the SELCoH sample with the APMS England sample and the APMS sample from the Greater London area in combined datasets, these differences remained after adjusting for socio-demographic and socioeconomic indicators for all outcomes.

Conclusions/Significance

Local information for estimating the prevalence of CMD and substance use is essential for surveillance and service planning. There were similarities in the demographic and socioeconomic factors related to CMD and substance use across samples.  相似文献   
942.
943.
Suaeda salsa L. is a halophytic species that is well adapted to high salinity. In order to understand its salt tolerance mechanism, we examined the growth and vacuolar H+-ATPase (V-ATPase) response to NaCl within the shoots and roots. The growth of shoots, but not roots, was dramatically stimulated by NaCl. Cl? and Na+ were mainly accumulated in shoots. V-ATPase activity was significantly increased by NaCl in roots and especially in shoots. Interestingly, antisera ATP95 and ATP88b detected three V1 subunits...  相似文献   
944.
945.
Ontario''s program for PKU screening of newborn infants reached 94.5% of the newborn population from 1966 to 1971. There were 70 infants identified by the program, 47 of whom were classical cases and 23 atypical cases of phenylketonuria. The incidence was 1:16,700 live births for classical cases and 1:34,000 live births for atypical cases. Since the beginning of the program 44 children have been identified in infancy as having PKU and have been treated successfully. Retardation has become evident in only three infants, two of whom were missed by the screening program.The cost of identification and care of one child for five years is about $7000, much less than the $250,000 needed to provide lifetime institutional care for one severely retarded individual.  相似文献   
946.
947.
948.
Results of key Soviet-era studies dealing with effects on the immune system and teratological consequences in rats exposed to radiofrequency (RF) fields serve, in part, as a basis for setting exposure limits in the USSR and the current RF standards in Russia. The World Health Organization's (WHO) International EMF Project considered these Soviet results important enough that they should be confirmed using more modern methods. Since the Soviet papers did not contain comprehensive details on how the results were obtained, Professor Yuri Grigoriev worked with Dr. Bernard Veyret to agree on the final study protocol and to conduct separate studies in Moscow and Bordeaux under the same protocol. The International Oversight Committee (IOC) provided oversight on the conduct of the studies and was the firewall committee that dealt with the sponsors and researchers. This paper gives the IOC comments and conclusions on the differing results between the two studies.  相似文献   
949.
The occurrence of spoilage fungi and Aspergillus section Flavi populations, the aflatoxins incidence, the role of insects as vectors of mycotoxin-producing fungi and the AFs-producing ability of the isolated species throughout the peanut (Arachis hypogaea L.) storage period were evaluated. Analyses of fungal populations from 95 peanut seed samples did not demonstrate significant differences between the incidences in each sampling period. Aspergillus section Flavi were isolated during all incubation periods. Cryptolestes spp. (Coleoptera: Cucujidae) were collected in August, September and October with 18, 16 and 28% of peanut samples contaminated, respectively. Insects isolated during August showed 69% of Aspergillus section Flavi contamination. A. flavus was the most frequently isolated (79%) from peanut seeds and from insect (59%). The greater levels of AFB1 were detected in September and October with a mean of 68.86 μg/kg and 69.12 μg/kg respectively. The highest proportion of A. flavus toxigenic strains (87.5%) was obtained in June. The presence of Aspergillus section Flavi and insect vectors of aflatoxigenic fungi presented a potential risk for aflatoxin production during the peanut storage period. Integrated management of fungi and insect vectors is in progress.  相似文献   
950.
An understanding of how broadly neutralizing activity develops in HIV-1-infected individuals is needed to guide vaccine design and immunization strategies. Here we used a large panel of 44 HIV-1 envelope variants (subtypes A, B, and C) to evaluate the presence of broadly neutralizing antibodies in serum samples obtained 3 years after seroconversion from 40 women enrolled in the CAPRISA 002 acute infection cohort. Seven of 40 participants had serum antibodies that neutralized more than 40% of viruses tested and were considered to have neutralization breadth. Among the samples with breadth, CAP257 serum neutralized 82% (36/44 variants) of the panel, while CAP256 serum neutralized 77% (33/43 variants) of the panel. Analysis of longitudinal samples showed that breadth developed gradually starting from year 2, with the number of viruses neutralized as well as the antibody titer increasing over time. Interestingly, neutralization breadth peaked at 4 years postinfection, with no increase thereafter. The extent of cross-neutralizing activity correlated with CD4(+) T cell decline, viral load, and CD4(+) T cell count at 6 months postinfection but not at later time points, suggesting that early events set the stage for the development of breadth. However, in a multivariate analysis, CD4 decline was the major driver of this association, as viral load was not an independent predictor of breadth. Mapping of the epitopes targeted by cross-neutralizing antibodies revealed that in one individual these antibodies recognized the membrane-proximal external region (MPER), while in two other individuals, cross-neutralizing activity was adsorbed by monomeric gp120 and targeted epitopes that involved the N-linked glycan at position 332 in the C3 region. Serum antibodies from the other four participants targeted quaternary epitopes, at least 2 of which were PG9/16-like and depended on the N160 and/or L165 residue in the V2 region. These data indicate that fewer than 20% of HIV-1 subtype C-infected individuals develop antibodies with cross-neutralizing activity after 3 years of infection and that these antibodies target different regions of the HIV-1 envelope, including as yet uncharacterized epitopes.  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