全文获取类型
收费全文 | 61036篇 |
免费 | 5092篇 |
国内免费 | 52篇 |
出版年
2023年 | 213篇 |
2022年 | 620篇 |
2021年 | 1072篇 |
2020年 | 606篇 |
2019年 | 803篇 |
2018年 | 1217篇 |
2017年 | 987篇 |
2016年 | 1726篇 |
2015年 | 2791篇 |
2014年 | 3138篇 |
2013年 | 3684篇 |
2012年 | 4734篇 |
2011年 | 4477篇 |
2010年 | 2877篇 |
2009年 | 2499篇 |
2008年 | 3633篇 |
2007年 | 3343篇 |
2006年 | 3080篇 |
2005年 | 2765篇 |
2004年 | 2720篇 |
2003年 | 2402篇 |
2002年 | 2057篇 |
2001年 | 1723篇 |
2000年 | 1622篇 |
1999年 | 1292篇 |
1998年 | 584篇 |
1997年 | 513篇 |
1996年 | 440篇 |
1995年 | 434篇 |
1994年 | 346篇 |
1993年 | 330篇 |
1992年 | 716篇 |
1991年 | 569篇 |
1990年 | 525篇 |
1989年 | 519篇 |
1988年 | 435篇 |
1987年 | 420篇 |
1986年 | 345篇 |
1985年 | 365篇 |
1984年 | 292篇 |
1983年 | 241篇 |
1982年 | 206篇 |
1981年 | 177篇 |
1980年 | 176篇 |
1979年 | 240篇 |
1978年 | 217篇 |
1977年 | 189篇 |
1976年 | 187篇 |
1974年 | 211篇 |
1973年 | 171篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
The purpose of this review is to provide an overview of the effects of adenovirus and influenza virus infections on obesity in various experimental models. We reviewed studies that were conducted within the past 10 years and were related to virus infection and obesity prevalence. Here, we discuss a different causal relationship between adenovirus and influenza infections with obesity. Adenovirus infection can cause obesity, whereas obesity can be a risk factor for increasing influenza virus infection and increases the risk of morbidity and mortality. The prevalence of obesity due to adenovirus infections may be due to an increase in glucose uptake and reduction in lipolysis caused by an increase in corticosterone secretion. Adenovirus infections may lead to increases in appetite by decreasing norepinephrine and leptin levels and also cause immune dysfunction. The relationship between obesity and influenza virus infection could be summarized by the following features: decreases in memory T-cell functionality and interferon (IFN)-α, IFN-β, and IFN-γ mRNA expression, increases in viral titer and infiltration, and impaired dendritic cell function in obese individuals. Moreover, leptin resistance may play an important role in increasing influenza virus infections in obese individuals. In conclusion, prevention of adenovirus infections could be a good approach for reducing obesity prevalence, and prevention of obesity could reduce influenza virus infections from the point of view of viral infections and obesity. 相似文献
104.
The 24-h time budget of a takh harem stallion (Equus ferus przewalskii) pre- and post-reintroduction
Lee Boyd 《Applied animal behaviour science》1998,60(4):291-299
Focal animal sampling was used to determine the 24-h time budget of a takh harem stallion (Equus ferus przewalskii) during the 2 weeks prior to, and the two weeks following, reintroduction into the Hustain Nuruu Steppe Reserve, Mongolia. Both before and after release, the stallion spent approximately 47% of his time grazing, 6% standing, and 5% in recumbent rest. The biggest changes to the time budget after release were a 4-fold increase in the amount of time spent moving, and a 50% decrease in the amount of time spent resting in a standing position. During the middle of the day when the temperatures were hottest, the stallion exhibited less grazing and more standing resting behaviour than in the morning or evening hours. Recumbent rest invariably occurred in the hours before dawn. 相似文献
105.
106.
107.
108.
Fluorescamine and trinitrobenzenesulfonate were used as chemical probes to differentially label amino phospholipids in liposomes. At low concentrations, fluorescamine reacts primarily with amino lipids on the external half of the bilayer. Further increase in fluorescamine concentration resulted in a linear increase of labeling indicating penetration and reaction with the internal half of the bilayer. Because of the pH requirements of the fluorescamine reaction, internal labeling was eliminated with a H+ gradient: inside acidic/outside alkaline. Differential labeling was also achieved with trinitrobenzenesulfonate, which is normally not permeable but which can be transported by valinomycin-K+ complex and react with internal amines. Thus, either half of the bilayer can be labeled with the same or different reagents. When liposomes were double-labeled, the fluorescence of fluorescamine was quenched by the trinitrobenzenesulfonate label. This quenching was reversed by solubilizing the liposomes with acidic ethanol. No quenching occurred when fluorescamine-labeled liposomes were mixed with trinitrobenzenesulfonate-reacted liposomes (or trinitrophenylated methylamine) suggesting close proximity of two labels is required for quenching. Conditions which promoted vesicular fusion promptly produced quenching. These differential labeling procedures can be usefully applied to quantitate aminolipids on internal and external vesicular surface, monitor vesicular fusion, and assess liposomal structure. 相似文献
109.
Various features of the settlement stage larva (cyprid) of the barnacle, Balanus balanoides (L.), were studied using scanning and transmission electron microscopy. The cuticle of the valves is pitted and in section has a characteristic ultrastructure. Small sensory setae protrode from the surface of this cuticle and are probably mechanoreceptors able to sense water movement around the larva. Each of the pair of caudla appendages which protrude from between the larval valves posteriorly, is made up of several sensory setae. These appendages are able to sense settlement surface topography. Certain other features of the larva are alos described and their roles discussed; such features include the frontal filaments, antennules and thoracic limbs. 相似文献
110.
Ryan K. Cheu Andrew T. Gustin Christina Lee Luca Schifanella Charlene J. Miller Avie Ha Casey Kim Violeta J. Rodriguez Margaret Fischl Adam D. Burgener Kelly B. Arnold Maria L. Alcaide Nichole R. Klatt 《PLoS pathogens》2020,16(12)
Despite the efficacy of antiretroviral-based pre-exposure prophylactics (PrEP) in men who have sex with men, studies in women have produced widely varying outcomes. Recent evidence demonstrates that vaginal microbial communities are associated with increased HIV acquisition risk and may impact PrEP efficacy. Here, we investigate the mechanisms underlying how vaginal bacteria alter PrEP drug levels and impact HIV infection rates ex vivo. Using cervicovaginal lavages (CVLs) from women with or without bacterial vaginosis (BV), we identified microbial metabolism of PrEP drugs in BV samples through LC-MS/MS analysis of soluble drug levels and metabolite formation in dual T-cell cultures. CVL samples were assessed for microbiome analysis using sequencing of bacterial 16S rRNA genes. We also observed non-Lactobacillus bacteria that are associated with BV may potentially impact PrEP efficacy through increased HIV infection rates in co-cultures containing Lactobacillus or BV bacteria, PrEP drugs, CEM-GFP cells, and HIV-1LAI virus. Finally, we used these data to develop a novel predictive mathematical simulation modeling system to predict these drug interactions for future trials. These studies demonstrate how dysbiotic vaginal microbiota may impact PrEP drugs and provides evidence linking vaginal bacteria to PrEP efficacy in women. 相似文献