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   1684篇
  免费   108篇
  国内免费   38篇
  1830篇
  2023年   16篇
  2022年   37篇
  2021年   41篇
  2020年   28篇
  2019年   43篇
  2018年   35篇
  2017年   26篇
  2016年   57篇
  2015年   83篇
  2014年   111篇
  2013年   127篇
  2012年   140篇
  2011年   134篇
  2010年   88篇
  2009年   54篇
  2008年   88篇
  2007年   68篇
  2006年   67篇
  2005年   56篇
  2004年   52篇
  2003年   54篇
  2002年   47篇
  2001年   48篇
  2000年   35篇
  1999年   27篇
  1998年   6篇
  1997年   13篇
  1996年   8篇
  1994年   10篇
  1993年   12篇
  1992年   22篇
  1991年   15篇
  1990年   21篇
  1989年   13篇
  1988年   18篇
  1987年   12篇
  1986年   10篇
  1985年   8篇
  1984年   6篇
  1983年   9篇
  1981年   7篇
  1979年   8篇
  1978年   6篇
  1977年   6篇
  1976年   6篇
  1975年   7篇
  1974年   6篇
  1973年   6篇
  1972年   7篇
  1971年   6篇
排序方式: 共有1830条查询结果,搜索用时 15 毫秒
51.
Previous studies have demonstrated that valosin-containing protein (VCP) is associated with H. pylori-induced gastric carcinogenesis. By identifying the interactome of VCP overexpressed in AGS cells using a subtractive proteomics approach, we aimed to characterize the cellular responses mediated by VCP and its functional roles in H. pylori-associated gastric cancer. VCP immunoprecipitations followed by proteomic analysis identified 288 putative interacting proteins, 18 VCP-binding proteins belonged to the PI3K/Akt signaling pathway. H. pylori infection increased the interaction between Akt and VCP, Akt-dependent phosphorylation of VCP, levels of ubiquitinated proteins, and aggresome formation in AGS cells. Furthermore, phosphorylated VCP co-localized with the aggresome, bound ubiquitinated proteins, and increased the degradation of cellular regulators to protect H. pylori-infected AGS cells from apoptosis. Our study demonstrates that VCP phosphorylation following H. pylori infection promotes both gastric epithelial cell survival, mediated by the PI3K/Akt pathway, and the degradation of cellular regulators. These findings provide novel insights into the mechanisms of H. pylori infection induced gastric carcinogenesis.  相似文献   
52.
In Taiwan, new H1N1 monovalent vaccines without adjuvant and with MF59® adjuvant were used in the nationwide vaccination campaign beginning on November 1, 2009. From November 2009 through February 2010, the authors identified recipients of H1N1 vaccines who were diagnosed with adverse events of special interest (AESIs) in a large-linked safety database, and used the self-controlled case series (SCCS) method to examine the risk of each AESI in the 0–42 days after H1N1 vaccination. Of the 3.5 million doses of H1N1 vaccines administered and captured in the linked database, the SCCS analysis of Guillain-Barré syndrome (GBS) found an incidence rate ratio of 3.81 (95% confidence interval 0.43–33.85) within 0–42 days after nonadjuvanted H1N1 vaccination and no cases after MF59®-adjuvanted H1N1 vaccination. The risks of other AESIs were, in general, not increased in any of the predefined postvaccination risk periods and age groups. The databases and infrastructure created for H1N1 vaccine safety evaluation may serve as a model for safety, effectiveness and coverage studies of licensed vaccines in Taiwan.  相似文献   
53.
Workplace health promotion (WHP) is important to prevent work-related diseases, reduce workplace hazards, and improve personal health of the workers. Health promotion projects were launched through the centers of WHP funded by the Taiwan Bureau of Health Promotion since 2003. Hence, the aim of this study is to evaluate the impact of WHP programs intervention from 2003 to 2007. The intervention group consisted of 838 business entities which had ever undergone counseling of the three centers in northern, central, and southern Taiwan from 2003 to 2007. The control group was composed of 1000 business entities randomly selected from the business directories of the Ministry of Economic Affairs, Taiwan. The questionnaire survey included general company profiles and the assessment of workplace health according to the five action areas of the Ottawa Charter for Health Promotion. We have received 447 (53.3%) questionnaires from the intervention group and 97 questionnaires from the control group. The intervention group was more effective in using the external resources and medical consultation, and they had better follow-up rates of the abnormal results of annual health examinations. Compared to the control group, the intervention group had a significantly decreased smoking rate in 246 companies (61.2%) and a reduced second-hand smoke exposure in 323 companies (78.6%) (p<0.001). By means of the intervention of WHP programs, we can enhance the awareness of the enterprises and the employees to improve worksite health and to create a healthy work environment.  相似文献   
54.
This study combined optical diffusometry and bead-based immunoassays to develop a novel technique for quantifying the growth of specific microorganisms and achieving rapid AST. Diffusivity rises when live bacteria attach to particles, resulting in additional energy from motile microorganisms. However, when UV-sterilized (dead) bacteria attach to particles, diffusivity declines. The experimental data are consistent with the theoretical model predicted according to the equivalent volume diameter. Using this diffusometric platform, the susceptibility of Pseudomonas aeruginosa to the antibiotic gentamicin was tested. The result suggests that the proliferation of bacteria is effectively controlled by gentamicin. This study demonstrated a sensitive (one bacterium on single particles) and time-saving (within 2 h) platform with a small sample volume (~0.5 μL) and a low initial bacteria count (50 CFU per droplet ~ 105 CFU/mL) for quantifying the growth of microorganisms depending on Brownian motion. The technique can be applied further to other bacterial strains and increase the success of treatments against infectious diseases in the near future.  相似文献   
55.
AimsThe aim of the present study is to determine the pooled predictive value of carotid distensibility coefficient (DC) for cardiovascular (CV) diseases and all-cause mortality.BackgroundArterial stiffness is associated with future CV events. Aortic pulse wave velocity is a commonly used predictor for CV diseases and all-cause mortality; however, its assessment requires specific devices and is not always applicable in all patients. In addition to the aortic artery, the carotid artery is also susceptible to atherosclerosis, and is highly accessible because of the surficial property. Thus, carotid DC, which indicates the intrinsic local stiffness of the carotid artery and may be determined using ultrasound and magnetic resonance imaging, is of interest for the prediction. However, the role of carotid DC in the prediction of CV diseases and all-cause mortality has not been thoroughly characterized, and the pooled predictive value of carotid DC remains unclear.MethodsA meta-analysis, which included 11 longitudinal studies with 20361 subjects, was performed.ResultsCarotid DC significantly predicted future total CV events, CV mortality and all-cause mortality. The pooled risk ratios (RRs) of CV events, CV mortality and all-cause mortality were 1.19 (1.06–1.35, 95%CI, 9 studies with 18993 subjects), 1.09 (1.01–1.18, 95%CI, 2 studies with 2550 subjects) and 1.65 (1.15–2.37, 95%CI, 6 studies with 3619 subjects), respectively, for the subjects who had the lowest quartile of DC compared with their counterparts who had higher quartiles. For CV events, CV mortality and all-cause mortality, a decrease in DC of 1 SD increased the risk by 13%, 6% and 41% respectively, whereas a decrease in DC of 1 unit increased the risk by 3%, 1% and 6% respectively.ConclusionsCarotid DC is a significant predictor of future CV diseases and all-cause mortality, which may facilitate the identification of high-risk patients for the early diagnosis and prompt treatment of CV diseases.  相似文献   
56.

Background

CpG islands have been demonstrated to influence local chromatin structures and simplify the regulation of gene activity. However, the accurate and rapid determination of CpG islands for whole DNA sequences remains experimentally and computationally challenging.

Methodology/Principal Findings

A novel procedure is proposed to detect CpG islands by combining clustering technology with the sliding-window method (PSO-based). Clustering technology is used to detect the locations of all possible CpG islands and process the data, thus effectively obviating the need for the extensive and unnecessary processing of DNA fragments, and thus improving the efficiency of sliding-window based particle swarm optimization (PSO) search. This proposed approach, named ClusterPSO, provides versatile and highly-sensitive detection of CpG islands in the human genome. In addition, the detection efficiency of ClusterPSO is compared with eight CpG island detection methods in the human genome. Comparison of the detection efficiency for the CpG islands in human genome, including sensitivity, specificity, accuracy, performance coefficient (PC), and correlation coefficient (CC), ClusterPSO revealed superior detection ability among all of the test methods. Moreover, the combination of clustering technology and PSO method can successfully overcome their respective drawbacks while maintaining their advantages. Thus, clustering technology could be hybridized with the optimization algorithm method to optimize CpG island detection.

Conclusion/Significance

The prediction accuracy of ClusterPSO was quite high, indicating the combination of CpGcluster and PSO has several advantages over CpGcluster and PSO alone. In addition, ClusterPSO significantly reduced implementation time.  相似文献   
57.
58.
59.
60.
稳定的边坡群落是公路边坡生态防护的目标,为探究高速公路生态护坡工程10 a演替后群落特征,该研究以泌桐高速公路为依托,布设自然恢复、单一狗牙根播种和5个不同播种密度的草灌混播生态防护措施,分析不同恢复方式对边坡群落组成、生活型和物种多样性的影响。结果表明:(1)调查样方内共有52种植物,分属于17科49属。禾本科、菊科和豆科植物共26属29种,占种总数的55.77%,表明这三大科植物在边坡群落演替过程中起着重要作用。(2) 10 a演替后不同恢复方式下群落中多年生植物比例高于一年生草本植物。(3)在草灌混播样地中,群落物种多样性指数随着播种密度的增加呈先增加后降低的单峰变化趋势,在播种密度为每平方米500株时达到最大。(4)草灌混播的生态恢复效果优于纯草本种植和自然恢复方式。(5)播种密度对草灌混播群落类型,地上生物量和物种多样性指数没有显著影响。从植物的生长效果及成本方面考虑,初播密度每平方米为500~600株的草灌混播可构建较为稳定的边坡植物群落,实现最佳的边坡恢复效果,可应用于类似区域边坡生态恢复工程。  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