全文获取类型
收费全文 | 7677篇 |
免费 | 535篇 |
国内免费 | 2篇 |
出版年
2023年 | 45篇 |
2022年 | 79篇 |
2021年 | 137篇 |
2020年 | 80篇 |
2019年 | 114篇 |
2018年 | 139篇 |
2017年 | 134篇 |
2016年 | 233篇 |
2015年 | 381篇 |
2014年 | 433篇 |
2013年 | 484篇 |
2012年 | 717篇 |
2011年 | 686篇 |
2010年 | 437篇 |
2009年 | 404篇 |
2008年 | 564篇 |
2007年 | 468篇 |
2006年 | 453篇 |
2005年 | 362篇 |
2004年 | 388篇 |
2003年 | 364篇 |
2002年 | 340篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 56篇 |
1998年 | 73篇 |
1997年 | 55篇 |
1996年 | 56篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 46篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 27篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有8214条查询结果,搜索用时 15 毫秒
951.
Burgess A Vanella L Bellner L Schwartzman ML Abraham NG 《Prostaglandins & other lipid mediators》2012,97(1-2):1-16
MSCs are considered to be the natural precursors to adipocyte development through the process of adipogenesis. A link has been established between decreased protective effects of EETs or HO-1 and their interaction in metabolic syndrome. Decreases in HO-1 or EET were associated with an increase in adipocyte stem cell differentiation and increased levels of inflammatory cytokines. EET agonist (AKR-I-27-28) inhibited MSC-derived adipocytes and decreased the levels of inflammatory cytokines. We further describe the role of CYP-epoxygenase expression, HO expression, and circulating cytokine levels in an obese mouse, ob/ob(-/-) mouse model. Ex vivo measurements of EET expression within MSCs derived from ob/ob(-/-) showed decreased levels of EETs that were increased by HO induction. This review demonstrates that suppression of HO and EET systems exist in MSCs prior to the development of adipocyte dysfunction. Further, adipocyte dysfunction can be ameliorated by induction of HO-1 and CYP-epoxygenase, i.e. EET. 相似文献
952.
953.
AP Bordon-Graciani LA Dias-Melicio MJ Acorci-Valério JP Araujo AM Soares 《Microbes and infection / Institut Pasteur》2012,14(12):1049-1053
In this study we investigated the role of nitric oxide (NO) in monocyte fungicidal activity against Paracoccidioides brasiliensis. We found that cells primed with IFN-γ, TNF-α or GM-CSF and challenged with a high-(Pb18) or low-virulence (Pb265) strain of the fungus increase their fungicidal activity. Expression of iNOS mRNA was increased after priming cells with each cytokine, and tended to be inhibited by Pb18. Despite up-regulation of iNOS mRNA expression by Pb265, an equivalent increase in NO production was not detected, as metabolite levels were similar in all cultures. The results indicated that high expression of human monocyte iNOS mRNA induced by P. brasiliensis is not correlated with NO concentrations produced. 相似文献
954.
Sperm are the most diverse cell type known: varying not only among- and within- species, but also among- and within-ejaculates of a single male. Recently, the causes and consequences of variability in sperm phenotypes have received much attention, but the importance of within-ejaculate variability remains largely unknown. Correlative evidence suggests that reduced within-ejaculate variation in sperm phenotype increases a male’s fertilization success in competitive conditions; but the transgenerational consequences of within-ejaculate variation in sperm phenotype remain relatively unexplored. Here we examine the relationship between sperm longevity and offspring performance in a marine invertebrate with external fertilization, Styela plicata. Offspring sired by longer-lived sperm had higher performance compared to offspring sired by freshly-extracted sperm of the same ejaculate, both in the laboratory and the field. This indicates that within-ejaculate differences in sperm longevity can influence offspring fitness – a source of variability in offspring phenotypes that has not previously been considered. Links between sperm phenotype and offspring performance may constrain responses to selection on either sperm or offspring traits, with broad ecological and evolutionary implications. 相似文献
955.
JP Souza JG Cecatti SM Haddad MA Parpinelli ML Costa L Katz L Say;Brazilian Network for Surveillance of Severe Maternal Morbidity 《PloS one》2012,7(8):e44129
Objectives
To validate the WHO maternal near-miss criteria and develop a benchmark tool for severe maternal morbidity assessments.Methods
In a multicenter cross-sectional study implemented in 27 referral maternity hospitals in Brazil, a one-year prospective surveillance on severe maternal morbidity and data collection was carried out. Diagnostic accuracy tests were used to assess the validity of the WHO maternal near-miss criteria. Binary logistic regression was used to model the death probability among women with severe maternal complications and benchmark the management of severe maternal morbidity.Results
Of the 82,388 women having deliveries in the participating health facilities, 9,555 women presented pregnancy-related complications, including 140 maternal deaths and 770 maternal near misses. The WHO maternal near-miss criteria were found to be accurate and highly associated with maternal deaths (Positive likelihood ratio 106.8 (95% CI 99.56–114.6)). The maternal severity index (MSI) model was developed and found to able to describe the relationship between life-threatening conditions and mortality (Area under the ROC curve: 0.951 (95% CI 0.909–0.993)).Conclusion
The identification of maternal near-miss cases using the WHO list of pregnancy-related life-threatening conditions was validated. The MSI model can be used as a tool for benchmarking the performance of health services managing women with severe maternal complications and provide case-mix adjustment. 相似文献956.
957.
A Rivero-Juárez J Morgaz A Camacho P Muñoz-Rascón JM Dominguez R Sánchez-Céspedes J Torre-Cisneros A Rivero 《PloS one》2012,7(7):e41557
Background
The objectives of this study were to evaluate the best position and best exploration probe for determining liver stiffness (LS) in dogs using transient liver elastography (TE). Thirteen dogs were used in the study.Methodology/Principal Findings
Morphometric measurements taken were thoracic circumference, weight and height. Elastographic measurements were taken in 4 anatomical positions using two different probes: medium (M) and small (S). The exploration was considered correct when the success rate was above 60% and the interquartile range of the measurements did not exceed 30%. The best measurements were obtained in the middle of the 6th–9th intercostal spaces, with the dog in the left lateral position and using probe M for preference in adults and probe S mandatory for animals <2 years. The correlation between probes was 99%. Intra-observer variability showed an intra-class correlation of 97.6%.Conclusions/Significance
TE is a technique that is reproducible in dogs. 相似文献958.
H Hackstein N Hagel A Knoche S Kranz J Lohmeyer W von Wulffen O Kershaw AD Gruber G Bein N Baal 《PloS one》2012,7(8):e43320
The TLR7 agonist imiquimod has been used successfully as adjuvant for skin treatment of virus-associated warts and basal cell carcinoma. The effects of skin TLR7 triggering on respiratory leukocyte populations are unknown. In a placebo-controlled experimental animal study we have used multicolour flow cytometry to systematically analyze the modulation of respiratory leukocyte subsets after skin administration of imiquimod. Compared to placebo, skin administration of imiquimod significantly increased respiratory dendritic cells (DC) and natural killer cells, whereas total respiratory leukocyte, alveolar macrophages, classical CD4+ T helper and CD8+ T killer cell numbers were not or only moderately affected. DC subpopulation analyses revealed that elevation of respiratory DC was caused by an increase of respiratory monocytic DC and CD11b(hi) DC subsets. Lymphocyte subpopulation analyses indicated a marked elevation of respiratory natural killer cells and a significant reduction of B lymphocytes. Analysis of cytokine responses of respiratory leukocytes after stimulation with Klebsiella pneumonia indicated reduced IFN-γ and TNF-α expression and increased IL-10 and IL-12p70 production after 7 day low dose skin TLR7 triggering. Additionally, respiratory NK cytotoxic activity was increased after 7d skin TLR7 triggering. In contrast, lung histology and bronchoalveolar cell counts were not affected suggesting that skin TLR7 stimulation modulated respiratory leukocyte composition without inducing overt pulmonary inflammation. These data suggest the possibility to modulate respiratory leukocyte composition and respiratory cytokine responses against pathogens like Klebsiella pneumonia through skin administration of a clinically approved TLR7 ligand. Skin administration of synthetic TLR7 ligands may represent a novel, noninvasive means to modulate respiratory immunity. 相似文献
959.
N López Andrés A Tesse V Regnault H Louis V Cattan SN Thornton C Labat A Kakou S Tual-Chalot S Faure P Challande M Osborne-Pellegrin MC Martínez P Lacolley R Andriantsitohaina 《PloS one》2012,7(7):e39235
We aimed to characterize circulating microparticles in association with arterial stiffness, inflammation and endothelial dysfunction in aldosterone-salt-induced hypertension in rats and to investigate the preventive effects of red wine polyphenols. Uninephrectomized male Sprague-Dawley rats were treated with aldosterone-salt (1 µg.h−1), with or without administration of either red wine polyphenols, Provinols™ (20 mg.kg−1.day−1), or spironolactone (30 mg.kg−1.day−1) for 4 weeks. Microparticles, arterial stiffness, nitric oxide (NO) spin trapping, and mesenteric arterial function were measured. Aldosterone-salt rats showed increased microparticle levels, including those originating from platelets, endothelium and erythrocytes. Hypertension resulted in enhanced aortic stiffness accompanied by increased circulating and aortic NO levels and an upregulation of aortic inducible NO-synthase, NFκB, superoxide anions and nitrotyrosine. Flow-induced dilatation was reduced in mesenteric arteries. These effects were prevented by spironolactone. Provinols™ did not reduce arterial stiffness or systolic hypertension but had effects similar to those of spironolactone on endothelial function assessed by flow-mediated vasodilatation, microparticle generation, aortic NO levels and oxidative stress and apoptosis in the vessel wall. Neither the contractile response nor endothelium-dependent relaxation in mesenteric arteries differed between groups. The in vivo effects of Provinols™ were not mediated by mineralocorticoid receptors or changes in shear stress. In conclusion, vascular remodelling and endothelial dysfunction in aldosterone-salt-mediated hypertension are associated with increased circulating microparticles. Polyphenols prevent the enhanced release of microparticles, macrovascular inflammation and oxidative stress, and microvascular endothelial dysfunction independently of blood pressure, shear stress and mineralocorticoid receptor activation in a model of hyperaldosteronism. 相似文献
960.