全文获取类型
收费全文 | 1698篇 |
免费 | 142篇 |
国内免费 | 1篇 |
出版年
2022年 | 12篇 |
2021年 | 26篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 28篇 |
2017年 | 21篇 |
2016年 | 50篇 |
2015年 | 59篇 |
2014年 | 77篇 |
2013年 | 82篇 |
2012年 | 105篇 |
2011年 | 93篇 |
2010年 | 78篇 |
2009年 | 65篇 |
2008年 | 69篇 |
2007年 | 100篇 |
2006年 | 85篇 |
2005年 | 82篇 |
2004年 | 97篇 |
2003年 | 86篇 |
2002年 | 75篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 22篇 |
1995年 | 15篇 |
1994年 | 30篇 |
1993年 | 20篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1974年 | 8篇 |
1972年 | 8篇 |
1970年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有1841条查询结果,搜索用时 185 毫秒
321.
322.
Marcia Ricci 《Biodiversity and Conservation》2006,15(10):3111-3130
Was realized field studies and ex situ propagation on the vascular flora of Juan Fernández Archipelago during 15 year period.
To evaluate the conservation status of a total of 133 species and subspecies of vascular endemic plants I used a IUCN classification
founding: 2 species extinct, 1 extinct in it natural habitat, 52 critically endangered, 37 endangered and 9 vulnerable. Thus,
73.8% are contained in a threat category; only 24 taxon can be considered to be of a lesser conservation concern. The largest
threat of extinction is a reduction in individuals in local populations resulting in small, isolated populations. This habitat
fragmentation and a reduction in endemic flora has also impacted endemic fauna. Besides, during this period was propagated
in nurseries a total of 80 of these species and subspecies (60%). It seem clear the necessity to continue to actions conserve
this particular ecosystem. 相似文献
323.
We investigated the effect of fish oil (FO) treatment on cardiorenal structure of adult offspring from low-protein pregnancies. Three month old offspring were assigned to eight groups (four male groups and four female groups, n=8 each) (NP=normal-protein diet, LP=low-protein diet): NP, LP, NP plus FO, and LP plus FO. Left ventricle and kidney were analyzed with light microscopy and stereology. The both sexes of LP offspring showed 30% lower birth weights than the respective NP offspring and high blood pressure (BP) levels in adulthood which was efficiently reduced by FO treatment. In the heart, FO treated the cardiomyocyte hypertrophy, the vascularization impairment, and decreased the cardiomyocyte loss usually observed in adult LP offspring. In the kidney, FO treated, in the male, the imbalance of the cortex-to-medulla ratio observed in both sexes of LP offspring, and reduced the glomeruli loss in the LP offspring. The positive correlation between the number of cardiomyocyte nuclei later in life and the body mass (BM) at birth was significant only in both sexes of LP offspring and this correlation disappeared in LP plus fish oil offspring. The positive correlation between the number of glomeruli later in life and the BM at birth was significant in NP male offspring and in both sexes of LP offspring. In conclusion, FO supplement, which is a rich source of n-3 fatty acids (DHA and EPA), has beneficial effects on BP control and cardiac and renal adverse remodeling usually seen in offspring of the LP pregnancies. 相似文献
324.
Monoclonal antibodies represent an attractive therapeutic tool as they are highly specific for their targets, convey effector functions and enjoy robust manufacturing procedures. Humanization of murine monoclonal antibodies has vastly improved their in vivo tolerability. Humanization, the replacement of mouse constant regions and V framework regions for human sequences, results in a significantly less immunogenic product. However, some humanized and even fully human sequence-derived antibody molecules still carry immunological risk. to more fully understand the immunologic potential of humanized and human antibodies, we analyzed CD4+ helper T cell epitopes in a set of eight humanized antibodies. the antibodies studied represented a number of different VH and VL family members carrying unique CDR regions. In spite of these differences, CD4+ T cell epitopes were found only in CDR-sequence containing regions. We were able to incorporate up to two amino acid modifications in a single epitope that reduced the immunogenic potential while retaining full biologic function. We propose that immunogenicity will always be present in some antibody molecules due to the nature of the antigen-specific combining sites. A consequence of this result is modifications to reduce immunogenicity will be centered on the affinity-determining regions. Modifications to CDR regions can be designed that reduce the immunogenic potential while maintaining the bioactivity of the antibody molecule.Key words: therapeutic, antibody, immunogenicity, deimmunizing, epitope 相似文献
325.
Sarah M. Camhi Marcia L. Stefanick Peter T. Katzmarzyk Deborah R. Young 《Obesity (Silver Spring, Md.)》2010,18(3):548-554
It is difficult to identify the successful component(s) related to changes in metabolic syndrome (MetS) from lifestyle interventions: the weight loss, the behavior change, or the combination. The purpose of this study is to determine the effects of a weight‐stable randomized controlled trial of low‐fat diet and exercise, alone and in combination, on MetS. Men (n = 179) and postmenopausal women (n = 149) with elevated low‐density lipoprotein cholesterol (LDL‐C) and low high‐density lipoprotein cholesterol (HDL‐C) were randomized into a 1‐year, weight‐stable trial with four treatment groups: control (C), diet (D), exercise (E), or diet plus exercise (D+E). MetS was defined using a continuous score. Changes in MetS score (ΔMetS) were compared between groups using analysis of covariance, stratified by gender and using two models, with and without baseline and change in percent body fat (ΔBF) as a covariate. In men, ΔMetS was higher for D vs. C (P = 0.04), D+E vs. C (P = 0.0002), and D+E vs. E (P = 0.02). For women, ΔMetS was greater for D vs. C (P = 0.045), E vs. C (P = 0.02), and D+E vs. C (P = 0.004). After adjusting for ΔBF, all differences between groups were attenuated and no longer significant. ΔMetS were associated with ΔBF for both men (P < 0.0001) and women (P = 0.004). After adjustment for ΔBF, low‐fat diet alone and in combination with exercise had no effect on MetS. The key component for MetS from low‐fat diet and/or increased physical activity appears to be body fat loss. 相似文献
326.
Background
Costs of tuberculosis diagnosis and treatment may represent a significant burden for the poor and for the health system in resource-poor countries.Objectives
The aim of this study was to analyze patients'' costs of tuberculosis care and to estimate the incremental cost-effectiveness ratio (ICER) of the directly observed treatment (DOT) strategy per completed treatment in Rio de Janeiro, Brazil.Methods
We interviewed 218 adult patients with bacteriologically confirmed pulmonary tuberculosis. Information on direct (out-of-pocket expenses) and indirect (hours lost) costs, loss in income and costs with extra help were gathered through a questionnaire. Healthcare system additional costs due to supervision of pill-intake were calculated considering staff salaries. Effectiveness was measured by treatment completion rate. The ICER of DOT compared to self-administered therapy (SAT) was calculated.Principal Findings
DOT increased costs during the treatment phase, while SAT increased costs in the pre-diagnostic phase, for both the patient and the health system. Treatment completion rates were 71% in SAT facilities and 79% in DOT facilities. Costs per completed treatment were US$ 194 for patients and U$ 189 for the health system in SAT facilities, compared to US$ 336 and US$ 726 in DOT facilities. The ICER was US$ 6,616 per completed DOT treatment compared to SAT.Conclusions
Costs incurred by TB patients are high in Rio de Janeiro, especially for those under DOT. The DOT strategy doubles patients'' costs and increases by fourfold the health system costs per completed treatment. The additional costs for DOT may be one of the contributing factors to the completion rates below the targeted 85% recommended by WHO. 相似文献327.
Isolation by oceanic distance and spatial genetic structure in an overharvested international fishery
下载免费PDF全文
![点击此处可从《Diversity & distributions》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nathan K. Truelove Stephen J. Box Karl A. Aiken Azra Blythe‐Mallett Erik M. Boman Catherine J. Booker Tamsen T. Byfield Courtney E. Cox Martha H. Davis Gabriel A. Delgado Bob A. Glazer Sarah M. Griffiths Kimani Kitson‐Walters Andy S. Kough Ricardo Pérez Enríquez Richard F. Preziosi Marcia E. Roy Iris Segura‐García Mona K. Webber Allan W. Stoner 《Diversity & distributions》2017,23(11):1292-1300
328.
Mitochondrial Sirtuins and Molecular Mechanisms of Aging 总被引:1,自引:0,他引:1
Robert A.H. van de Ven Daniel Santos Marcia C. Haigis 《Trends in molecular medicine》2017,23(4):320-331
329.
Sergio Luiz Montego Ferreira Junior Elis Regina Dalla Costa Paula Gon?alves dos Santos Harrison Magdinier Gomes Marcia Susana Nunes Silva Leonardo Souza Esteves Martha Maria Oliveira Raquel de Abreu Maschmann Afranio Lineu Kritski Philip Noel Suffys Maria Lucia Rosa Rossetti 《Memórias do Instituto Oswaldo Cruz》2014,109(3):307-314
Drug-resistant tuberculosis (TB) threatens global TB control and is a major public
health concern in several countries. We therefore developed a multiplex assay
(LINE-TB/MDR) that is able to identify the most frequent mutations related to
rifampicin (RMP) and isoniazid (INH) resistance. The assay is based on multiplex
polymerase chain reaction, membrane hybridisation and colorimetric detection
targeting of rpoB and katG genes, as well as the
inhA promoter, which are all known to carry specific mutations
associated with multidrug-resistant TB (MDR-TB). The assay was validated on a
reference panel of 108 M. tuberculosis isolates that were characterised by the
proportion method and by DNA sequencing of the targets. When comparing the
performance of LINE-TB/MDR with DNA sequencing, the sensitivity, specificity and
agreement were 100%, 100% and 100%, respectively, for RMP and 77.6%, 90.6% and 88.9%,
respectively, for INH. Using drug sensibility testing as a reference standard, the
performance of LINE-TB/MDR regarding sensitivity, specificity and agreement was 100%,
100% and 100% (95%), respectively, for RMP and 77%, 100% and 88.7% (82.2-95.1),
respectively, for INH. LINE-TB/MDR was compared with GenoType MTBDRplus for 65
isolates, resulting in an agreement of 93.6% (86.7-97.5) for RIF and 87.4%
(84.3-96.2) for INH. LINE-TB/MDR warrants further clinical validation and may be an
affordable alternative for MDR-TB diagnosis. 相似文献
330.