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   2049篇
  免费   262篇
  2022年   16篇
  2021年   23篇
  2020年   15篇
  2019年   14篇
  2018年   20篇
  2017年   24篇
  2016年   37篇
  2015年   58篇
  2014年   55篇
  2013年   67篇
  2012年   95篇
  2011年   114篇
  2010年   55篇
  2009年   71篇
  2008年   113篇
  2007年   83篇
  2006年   88篇
  2005年   87篇
  2004年   74篇
  2003年   82篇
  2002年   74篇
  2001年   71篇
  2000年   69篇
  1999年   54篇
  1998年   34篇
  1997年   21篇
  1996年   16篇
  1995年   23篇
  1994年   28篇
  1993年   31篇
  1992年   35篇
  1991年   45篇
  1990年   34篇
  1989年   39篇
  1988年   28篇
  1987年   35篇
  1986年   30篇
  1985年   23篇
  1984年   22篇
  1983年   27篇
  1982年   22篇
  1980年   14篇
  1979年   16篇
  1975年   16篇
  1974年   13篇
  1973年   15篇
  1972年   14篇
  1970年   20篇
  1969年   12篇
  1966年   15篇
排序方式: 共有2311条查询结果,搜索用时 15 毫秒
231.

Background

In areas where health resources are limited, community participation in the recognition and reporting of disease hazards is critical for the identification of outbreaks. This is particularly true for zoonotic diseases such as monkeypox that principally affect people living in remote areas with few health services. Here we report the findings of an evaluation measuring the effectiveness of a film-based community outreach program designed to improve the understanding of monkeypox symptoms, transmission and prevention, by residents of the Republic of the Congo (ROC) who are at risk for disease acquisition.

Methodology/Principal Findings

During 90 days, monkeypox outreach was conducted for ∼23,860 people in northern ROC. Two hundred seventy-one attendees (selected via a structured sample) were interviewed before and after participating in a small-group outreach session. The proportion of interviewees demonstrating monkeypox-specific knowledge before and after was compared. Significant gains were measured in areas of disease recognition, transmission, and mitigation of risk. The ability to recognize at least one disease symptom and a willingness to take a family member with monkeypox to the hospital increased from 49 and 45% to 95 and 87%, respectively (p<0.001, both). Willingness to deter behaviors associated with zoonotic risk, such as eating the carcass of a primate found dead in the forest, remained fundamentally unchanged however, suggesting additional messaging may be needed.

Conclusions/Significance

These results suggest that our current program of film-based educational activities is effective in improving disease-specific knowledge and may encourage individuals to seek out the advice of health workers when monkeypox is suspected.  相似文献   
232.

Background

The purpose of this study was to assess the relationship between one's sense of control and visceral adipose tissue.

Methods

This cross-sectional study recruited 571 subjects (45 years and older) who were asymptomatic of CHD from Fort Worth, Texas from 2006 to 2008. Subjects completed a questionnaire, body measurements, a multi-slice computed tomography scan to assess for visceral adipose tissue (VAT) centered at the L4L5 spinal interspace, and serum chemistries. The natural log of L4L5 VAT (lnVAT) was used in all analyses to achieve normality of the data with final analyses including 506 participants. Linear regression was used to estimate unadjusted and adjusted beta-coefficients and standard errors for the association between sense of control and lnVAT.

Results

A total of 506 participants were used in the data after adjusting for normality of the data. An increase in sense of control was associated with a decrease in lnVAT in the unadjusted (p < 0.001) and adjusted (p = 0.03) models. Other factors significantly associated with lnVAT in the adjusted model include age, BMI, male gender, non-Hispanic African American, and diet.

Conclusions

Sense of control remained as an independent factor associated with visceral adiposity despite adjusting for traditional cardiovascular risk factors, including BMI. Future studies should focus on establishing a causal relationship between sense of control and visceral adiposity.  相似文献   
233.
The use of Parafilm membranes for in-vitro feeding of northern fowl mites, Ornithonyssus sylviarum (Canestrini & Fanzago), is described. A membrane stretched in two perpendicular directions, folded, heat-sealed, inflated, and twisted at the ends to form a sphere allowed a high percentage (greater than 80%) of surviving adult female mites to feed on whole chicken blood. A high percentage (7 of 10) of protonymphs also fed through the membrane. Mites were able to feed from the same sac for 3 d and oviposited on the sac. This technology has potential applications for use in rearing O. sylviarum and other hematophagous arthropods, and for physiological experimentation.  相似文献   
234.
Homologous recombination provides an effective way to repair DNA double-strand breaks (DSBs) and is required for genetic recombination. During the process of homologous recombination, a heteroduplex DNA structure, or a ‘Holliday junction’ (HJ), is formed. The movement, or branch migration, of this junction is necessary for recombination to proceed correctly. In prokaryotes, the RecQ protein or the RuvA/RuvB protein complex can promote ATP-dependent branch migration of Holliday junctions. Much less is known about the processing of Holliday junctions in eukaryotes. Here, we identify RecQL1 as a predominant ATP-dependent, HJ branch migrator present in human nuclear extracts. A reduction in the level of RecQL1 induced by RNA interference in HeLa cells leads to an increase in sister chromatid exchange. We propose that RecQL1 is involved in the processing of Holliday junctions in human cells.  相似文献   
235.
Responses of host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say and lone star tick, Amblyomma americanum (Linnaeus) (Acari: Ixodidae) to the repellents N,N-diethyl-3-methylbenzamide (deet) and (1S, 2'S)-2-methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) were studied using fingertip laboratory bioassays. Ethanol solutions of both compounds applied to the skin strongly repelled both species of ticks at 0.8 and 1.6 micromole of compound/cm2 skin. The ticks were also repelled when two layers of organdie cloth covered the portion of a finger treated with either deet or SS220. Gas chromatographic analyses of the outer layer of cloth that had covered skin treated with 1.6 micromole compound/cm2 skin revealed only 0.1 nmole SS220/cm2 cloth and 2.8 nmole deet/cm2 cloth. However, in bioassays in which a single layer of cloth was treated with a dose of deet or SS220 equivalent to the amount found in the outer layer of cloth, ticks were not repelled. Results unequivocally demonstrated that these ticks responded to the repellents in the vapour phase when repellent treated skin was covered with cloth to obviate tactile contact with them, and made it clear that the ticks detect the repellents by olfactory sensing. Heretofore, the mode of action of deet and SS220 was unclear.  相似文献   
236.
237.
Phenotypic mechanisms that enhance bacterial UVR survival typically include pigmentation and DNA repair mechanisms which provide protection from UVA and UVB wavelengths, respectively. In this study, we examined the contribution of pigmentation to field survival in Clavibacter michiganensis and evaluated differences in population dynamics and leaf colonization strategies. Two C. michiganensis pigment-deficient mutants were significantly reduced in UVA radiation survival in vitro; one of these mutants also exhibited reduced field populations on peanut when compared to the wild-type strain over the course of replicate 25-day experiments. The UVR-tolerant C. michiganensis strains G7.1 and G11.1 maintained larger epiphytic field populations on peanut compared to the UVR-sensitive C. michiganensis T5.1. Epiphytic field populations of C. michiganensis utilized the strategy of solar UVR avoidance during leaf colonization resulting in increased strain survival on leaves after UVC irradiation. These results further demonstrate the importance of UVR tolerance in the ability of bacterial strains to maintain population size in the phyllosphere. However, an examination of several bacterial species from the peanut phyllosphere and a collection of environmental Pseudomonas spp. revealed that sensitivity to UVA and UVC radiation was correlated in some but not all of these bacteria. These results underscore a need to further understand the biological effects of different solar wavelength groups on microbial ecology.  相似文献   
238.
239.
240.
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