全文获取类型
收费全文 | 2720篇 |
免费 | 215篇 |
出版年
2021年 | 43篇 |
2020年 | 19篇 |
2019年 | 37篇 |
2018年 | 30篇 |
2017年 | 32篇 |
2016年 | 48篇 |
2015年 | 96篇 |
2014年 | 124篇 |
2013年 | 130篇 |
2012年 | 189篇 |
2011年 | 153篇 |
2010年 | 117篇 |
2009年 | 105篇 |
2008年 | 167篇 |
2007年 | 132篇 |
2006年 | 161篇 |
2005年 | 141篇 |
2004年 | 140篇 |
2003年 | 124篇 |
2002年 | 140篇 |
2001年 | 51篇 |
2000年 | 37篇 |
1999年 | 42篇 |
1998年 | 49篇 |
1997年 | 27篇 |
1996年 | 21篇 |
1995年 | 22篇 |
1994年 | 17篇 |
1993年 | 26篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 36篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1971年 | 8篇 |
1969年 | 9篇 |
排序方式: 共有2935条查询结果,搜索用时 31 毫秒
31.
Central American squirrel monkeys (Saimiri oerstedi) appear to recognize the modified leaves that phyllostomid bats utilize for diurnal roost sites. The monkeys visually and manually search these bat tents for both bats and insects. Adult males are the most successful at capturing bats. Nonvolant juvenile bats are more vulnerable to monkey predation than are adults. Bats that escape monkey predation frequently are captured by doubletoothed kites (Harpagus bidentatus) that tend foraging troops of monkeys. Predation by squirrel monkeys, coupled with that of double-toothed kites, may be a significant source of mortality for tent-making bats. 相似文献
32.
Attempts to quantitate metabolism in the lung and other tissues using radioactive precursors may be subject to significant errors arising from inappropriate assumptions regarding precursor metabolism, compartmentation and specific radioactivity. This article reviews the type and magnitude of error which may complicate such measurements by presenting specific data from experiments using radioactive amino acids to estimate the rate of protein synthesis. The applicability of these observations to other metabolic systems is discussed briefly in order to develop a more general awareness of the errors which may result from incomplete validation of experimental measurements using radioisotopes. 相似文献
33.
Ajith Anand Emily Wu Zhi Li Sue TeRonde Maren Arling Brian Lenderts Jasdeep S. Mutti William Gordon‐Kamm Todd J. Jones Nicholas Doane Chilcoat 《Plant biotechnology journal》2019,17(8):1636-1645
An efficient Agrobacterium‐mediated site‐specific integration (SSI) technology using the flipase/flipase recognition target (FLP/FRT) system in elite maize inbred lines is described. The system allows precise integration of a single copy of a donor DNA flanked by heterologous FRT sites into a predefined recombinant target line (RTL) containing the corresponding heterologous FRT sites. A promoter‐trap system consisting of a pre‐integrated promoter followed by an FRT site enables efficient selection of events. The efficiency of this system is dependent on several factors including Agrobacterium tumefaciens strain, expression of morphogenic genes Babyboom (Bbm) and Wuschel2 (Wus2) and choice of heterologous FRT pairs. Of the Agrobacterium strains tested, strain AGL1 resulted in higher transformation frequency than strain LBA4404 THY‐ (0.27% vs. 0.05%; per cent of infected embryos producing events). The addition of morphogenic genes increased transformation frequency (2.65% in AGL1; 0.65% in LBA4404 THY‐). Following further optimization, including the choice of FRT pairs, a method was developed that achieved 19%–22.5% transformation frequency. Importantly, >50% of T0 transformants contain the desired full‐length site‐specific insertion. The frequencies reported here establish a new benchmark for generating targeted quality events compatible with commercial product development. 相似文献
34.
Da Sun Jia Chen Wei Wu Ju Tang Li Luo Kun Zhang Libo Jin Sue Lin Yitian Gao Xiaoqing Yan Chi Zhang 《Journal of cellular and molecular medicine》2019,23(4):2863-2871
Obesity is associated with significant microvascular complications including renal injuries and may induce end‐stage renal disease. Emerging studies have demonstrated microRNAs (miRNAs) are potential mediators in the pathophysiological process of nephropathy. The present study aimed to investigate the role of miR‐802 in obesity‐related nephropathy and potential molecular mechanisms. Through utilizing obese mouse model and human subjects, we explored the therapeutic benefits and clinical application of miR‐802 in protecting against nephropathy. Renal miR‐802 level was positively correlated with functional parameters, including blood urea nitrogen and creatinine in obese mice. Specific silencing of renal miR‐802 improved high fat diet (HFD)‐induced renal dysfunction, structural disorders and fibrosis. The up‐regulated inflammatory response and infiltrated macrophages were also significantly decreased in miR‐802 inhibitor‐treated obese mice. Mechanistically, miR‐802 directly bond to 3?‐UTR of NF‐κB‐repressing factor (NRF) and suppressed its expression. In clinical study, the circulating miR‐802 level was significantly increased in obese subjects, and positively correlated with plasma creatinine level but negatively correlated with creatinine clearance. Taken together, our findings provided evidence that miR‐802/NRF signalling was an important pathway in mediating obesity‐related nephropathy. It is a possible useful clinical approach of treating miR‐802 inhibitor to combat nephropathy. 相似文献
35.
Shirin Moossavi Shadi Sepehri Bianca Robertson Lars Bode Sue Goruk Catherine J. Field Lisa M. Lix Russell J. de Souza Allan B. Becker Piushkumar J. Mandhane Stuart E. Turvey Padmaja Subbarao Theo J. Moraes Diana L. Lefebvre Malcolm R. Sears Ehsan Khafipour Meghan B. Azad 《Cell host & microbe》2019,25(2):324-335.e4
36.
37.
Steven A. Li Melissa M. Cadelis Kenneth Sue Marine Blanchet Nicolas Vidal Jean Michel Brunel Marie-Lise Bourguet-Kondracki Brent R. Copp 《Bioorganic & medicinal chemistry》2019,27(10):2090-2099
The combination of increased incidence of drug-resistant strains of bacteria and a lack of novel drugs in development creates an urgency for the search for new antimicrobials. Initial screening of compounds from an in-house library identified two 6-bromoindolglyoxylamide polyamine derivatives (3 and 4) that exhibited intrinsic antimicrobial activity towards Gram-positive bacteria, Staphylococcus aureus and S. intermedius with polyamine 3 also displaying in vitro antibiotic enhancing properties against the resistant Gram-negative bacterium Pseudomonas aeruginosa. A series of 6-bromo derivatives (5–15) were prepared and biologically evaluated, identifying analogues with enhanced antibacterial activity towards Escherichia coli and with moderate to excellent antifungal properties. Polyamine 3, which includes a spermine chain, was the most potent of the series – its mechanism of action was attributed to rapid membrane permeabilization and depolarization in both Gram-positive and Gram-negative bacteria. 相似文献
38.
Nicole E. Choquette Funda Ogut Timothy M. Wertin Christopher M. Montes Crystal A. Sorgini Alison M. Morse Patrick J. Brown Andrew D. B. Leakey Lauren M. McIntyre Elizabeth A. Ainsworth 《Global Change Biology》2019,25(12):4327-4338
Ozone is the most damaging air pollutant to crops, currently reducing Midwest US maize production by up to 10%, yet there has been very little effort to adapt germplasm for ozone tolerance. Ozone enters plants through stomata, reacts to form reactive oxygen species in the apoplast and ultimately decreases photosynthetic C gain. In this study, 10 diverse inbred parents were crossed in a half‐diallel design to create 45 F1 hybrids, which were tested for ozone response in the field using free air concentration enrichment (FACE). Ozone stress increased the heritability of photosynthetic traits and altered genetic correlations among traits. Hybrids from parents Hp301 and NC338 showed greater sensitivity to ozone stress, and disrupted relationships among photosynthetic traits. The physiological responses underlying sensitivity to ozone differed in hybrids from the two parents, suggesting multiple mechanisms of response to oxidative stress. FACE technology was essential to this evaluation because genetic variation in photosynthesis under elevated ozone was not predictable based on performance at ambient ozone. These findings suggest that selection under elevated ozone is needed to identify deleterious alleles in the world's largest commodity crop. 相似文献
39.
Wade Ruth N. Donaldson Sarah M. Karley Alison J. Johnson Scott N. Hartley Sue E. 《Plant and Soil》2022,477(1-2):69-81
Plant and Soil - Silicon (Si) accumulation in plant tissues plays a vital role in alleviating biotic and abiotic stresses, including drought. Temperate regions are predicted to experience... 相似文献