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   142篇
  免费   39篇
  2022年   2篇
  2021年   1篇
  2019年   3篇
  2018年   2篇
  2017年   1篇
  2016年   3篇
  2015年   7篇
  2014年   5篇
  2013年   10篇
  2012年   7篇
  2011年   10篇
  2010年   3篇
  2009年   3篇
  2008年   3篇
  2007年   1篇
  2006年   8篇
  2005年   7篇
  2004年   8篇
  2003年   10篇
  2002年   5篇
  2001年   6篇
  2000年   7篇
  1998年   5篇
  1997年   3篇
  1996年   5篇
  1995年   3篇
  1994年   10篇
  1993年   6篇
  1992年   9篇
  1991年   3篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1982年   2篇
  1980年   1篇
  1974年   1篇
  1971年   1篇
  1947年   2篇
  1945年   1篇
排序方式: 共有181条查询结果,搜索用时 250 毫秒
21.
The present study investigated the effect of unilateral and bilateral resistance exercise (RE) on maximal voluntary strength, total volume of load lifted (TVLL), rating of perceived exertion (RPE) and blood lactate concentration of resistance-trained males. Twelve healthy men were assessed for the leg extension one-repetition maximum (1RM) strength using bilateral and unilateral contractions. Following this assessment, an RE session (3 sets of repetitions to failure) was conducted with bilateral and unilateral (both limbs) contractions using a load of 50% 1RM. The TVLL was calculated by the product of the number of repetitions and the load lifted per repetition. RPE and blood lactate were measured before, during and after each set. Session RPE was measured 30 minutes after RE sessions. There was a significant difference in the bilateral (120.0±11.9) and unilateral (135.0±20.2 kg) 1RM strength (p < 0.05). The TVLL was similar between both RE sessions. Although the repetitions decreased with each successive set, the total number of repetitions completed in the bilateral protocol (48) was superior to the unilateral (40) protocol (p < 0.05). In both bouts, RPE increased with each subsequent set whilst blood lactate increased after set 1 and thereafter remained stable (p < 0.05). The RPE and lactate responses were not significantly different between both sessions. In conclusion, a bilateral deficit in leg extension strength was confirmed, but the TVLL was similar between both RE sessions when exercising to voluntary fatigue. This outcome could be attributed to the number of repetitions completed in the unilateral RE bout. The equal TVLL would also explain the similar perceptual and metabolic responses across each RE session.  相似文献   
22.
We performed a two-tiered, whole-genome association study of Parkinson disease (PD). For tier 1, we individually genotyped 198,345 uniformly spaced and informative single-nucleotide polymorphisms (SNPs) in 443 sibling pairs discordant for PD. For tier 2a, we individually genotyped 1,793 PD-associated SNPs (P<.01 in tier 1) and 300 genomic control SNPs in 332 matched case-unrelated control pairs. We identified 11 SNPs that were associated with PD (P<.01) in both tier 1 and tier 2 samples and had the same direction of effect. For these SNPs, we combined data from the case-unaffected sibling pair (tier 1) and case-unrelated control pair (tier 2) samples and employed a liberalization of the sibling transmission/disequilibrium test to calculate odds ratios, 95% confidence intervals, and P values. A SNP within the semaphorin 5A gene (SEMA5A) had the lowest combined P value (P=7.62 x 10(-6)). The protein encoded by this gene plays an important role in neurogenesis and in neuronal apoptosis, which is consistent with existing hypotheses regarding PD pathogenesis. A second SNP tagged the PARK11 late-onset PD susceptibility locus (P=1.70 x 10(-5)). In tier 2b, we also selected for genotyping additional SNPs that were borderline significant (P<.05) in tier 1 but that tested a priori biological and genetic hypotheses regarding susceptibility to PD (n=941 SNPs). In analysis of the combined tier 1 and tier 2b data, the two SNPs with the lowest P values (P=9.07 x 10(-6); P=2.96 x 10(-5)) tagged the PARK10 late-onset PD susceptibility locus. Independent replication across populations will clarify the role of the genomic loci tagged by these SNPs in conferring PD susceptibility.  相似文献   
23.
Several lines of evidence support for a role of angiotensin converting enzyme (ACE) in Alzheimer disease (AD). Most genetic studies have focused on an Alu insertion/deletion (I/D) polymorphism in the ACE gene (DCP1) and have yielded conflicting results. We evaluated the association between 15 single-nucleotide polymorphisms (SNPs) in DCP1, including the I/D variant, and AD in a sample of 92 patients with AD and 166 nondemented controls from an inbred Israeli Arab community. Although there was no evidence for association between AD and I/D, we observed significant association with SNPs rs4343 (P = .00001) and rs4351 (P = .01). Haplotype analysis revealed remarkably significant evidence of association with the SNP combination rs4343 and rs4351 (global P = 7.5 x 10(-7)). Individuals possessing the haplotype "GA" (frequency 0.21 in cases and 0.01 in controls) derived from these SNPs had a 45-fold increased risk of developing AD (95% CI 6.0-343.2) compared with those possessing any of the other three haplotypes. Longer range haplotypes including I/D were even more significant (lowest global P = 1.1 x 10(-12)), but the only consistently associated alleles were in rs4343 and rs4351. These results suggest that a variant in close proximity to rs4343 and rs4351 modulates susceptibility to AD in this community.  相似文献   
24.
Genetics of Parkinson disease: paradigm shifts and future prospects   总被引:12,自引:0,他引:12  
Parkinson disease is a complex, multifactorial neurodegenerative disease. Although a heritable basis was originally thought unlikely, recent studies have implicated several genes in its pathogenesis, and molecular findings now allow accurate diagnosis and challenge past criteria for defining Parkinson disease. Most importantly, genetic insights provide the rationale for new strategies for prevention or therapy, and have led to animal models of disease in which these strategies can be tested. Neuroprotective therapies can now be designed to slow or halt disease progression in affected subjects and asymptomatic carriers.  相似文献   
25.
The detailed movements of 32 acoustically tagged broadnose sevengill shark Notorynchus cepedianus were documented in and around north-east Pacific Ocean estuarine embayments from 2005 to 2007. Arrangements of passive acoustic receivers allowed analysis of movement at several spatial scales, with sex and size examined as possible factors influencing the pattern and timing of these movements. Notorynchus cepedianus exhibited a distinctly seasonal pattern of estuary use over three consecutive years, entering Willapa Bay in the spring, residing therein for extended periods of time during the summer and dispersing into nearshore coastal habitats and over the continental shelf during the autumn. Notorynchus cepedianus within Willapa Bay showed spatio-temporal patterns of segregation by size and sex, with males and small females using peripheral southern estuary channels early in the season before joining large females, who remained concentrated in central estuary channels for the entire season. Individuals displayed a high degree of fidelity not only to Willapa Bay (63% were documented returning over three consecutive seasons), but also to specific areas within the estuary, showing consistent patterns of site use from year to year. Cross-estuary movement was common during the summer, with most fish also moving into an adjacent estuarine embayment for some extent of time. Most winter and autumn coastal detections of N. cepedianus were made over the continental shelf near Oregon and Washington, U.S.A., but there were also examples of individuals moving into nearshore coastal habitats further south into California, suggesting the feasibility of broad-scale coastal movements to known birthing and nursery grounds for the species. These findings contribute to a better understanding of N. cepedianus movement ecology, which can be used to improve the holistic management of this highly mobile apex predator in regional ecosystems.  相似文献   
26.
ABSTRACT: BACKGROUND: Approximately 25% of hospitalized patients have a urinary catheter, and catheter associated urinary tract infection is the most common nosocomial infection in the US, causing >1 million cases/year. However, the natural history of the biofilms that rapidly form on urinary catheters and lead to infection is not well described. FINDINGS: We characterized the dynamics of catheter colonization among catheters collected from 3 women and 5 men in a trauma burn unit with different indwelling times using TRFLP and culture. All patients received antibiotic therapy. Results: Colony-forming units increased along the extraluminal catheter surface from the catheter balloon to the urethra, but no trend was apparent for the intraluminal surface. This suggests extraluminal bacteria come from periurethral communities while intraluminal bacteria are introduced via the catheter or already inhabit the urine/bladder. Richness of operational taxonomic units (OTUs) increased over time on the intraluminal surface, but was constant extraluminally. CONCLUSIONS: OTU community composition was explained best by time rather than axial location or surface. Our results suggest that catheter colonization can be very dynamic, and possibly have a predictable succession.  相似文献   
27.

Background

Internet support groups (ISGs) are popular, particularly among people with depression, but there is little high quality evidence concerning their effectiveness.

Aim

The study aimed to evaluate the efficacy of an ISG for reducing depressive symptoms among community members when used alone and in combination with an automated Internet-based psychotherapy training program.

Method

Volunteers with elevated psychological distress were identified using a community-based screening postal survey. Participants were randomised to one of four 12-week conditions: depression Internet Support Group (ISG), automated depression Internet Training Program (ITP), combination of the two (ITP+ISG), or a control website with delayed access to e-couch at 6 months. Assessments were conducted at baseline, post-intervention, 6 and 12 months.

Results

There was no change in depressive symptoms relative to control after 3 months of exposure to the ISG. However, both the ISG alone and the combined ISG+ITP group showed significantly greater reduction in depressive symptoms at 6 and 12 months follow-up than the control group. The ITP program was effective relative to control at post-intervention but not at 6 months.

Conclusions

ISGs for depression are promising and warrant further empirical investigation.

Trial Registration

Controlled-Trials.com ISRCTN65657330  相似文献   
28.
三氧化二砷对食管癌细胞增殖和热休克蛋白70表达的影响   总被引:2,自引:0,他引:2  
目的:研究三氧化二砷(As2O3)对食管癌细胞增殖和热休克蛋白70(HSP70)表达的影响。方法:通过相差显微镜、流式细胞术、免疫细胞化学染色和免疫印迹分析等方法观察As2O3对人食管癌细胞株EC1的作用效果和作用机制。结果:与对照组相比,经2μmol/L和5μmol/Las2O3作用的细胞出现明显的生长抑制,G2/M期细胞比例增加;2μmol/Las2O3作用48h后经Ecl细胞HSP70(heat shock protein70)及HSC70(heat shock cognate protein70)表达均增加。结论:As2O3诱导食管癌细胞G2/M期阻滞抑制细胞增殖和生长;HSP70的升高是细胞对As2O3作用后出现的应激反应,并与细胞周期阻滞相关。  相似文献   
29.
30.
The identification and optimization of a series of acylguanidine-based melanocortin-4 receptor antagonists is discussed.  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