全文获取类型
收费全文 | 10821篇 |
免费 | 850篇 |
国内免费 | 6篇 |
出版年
2023年 | 67篇 |
2022年 | 144篇 |
2021年 | 280篇 |
2020年 | 155篇 |
2019年 | 282篇 |
2018年 | 310篇 |
2017年 | 276篇 |
2016年 | 399篇 |
2015年 | 623篇 |
2014年 | 633篇 |
2013年 | 822篇 |
2012年 | 954篇 |
2011年 | 899篇 |
2010年 | 556篇 |
2009年 | 537篇 |
2008年 | 649篇 |
2007年 | 660篇 |
2006年 | 558篇 |
2005年 | 501篇 |
2004年 | 444篇 |
2003年 | 400篇 |
2002年 | 368篇 |
2001年 | 94篇 |
2000年 | 60篇 |
1999年 | 83篇 |
1998年 | 93篇 |
1997年 | 67篇 |
1996年 | 61篇 |
1995年 | 67篇 |
1994年 | 62篇 |
1993年 | 42篇 |
1992年 | 55篇 |
1991年 | 41篇 |
1990年 | 29篇 |
1989年 | 42篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 33篇 |
1984年 | 20篇 |
1983年 | 28篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1974年 | 15篇 |
1972年 | 11篇 |
1968年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Fadhlaoui-Zid Karima Cossu Piero Sanna Daria Scarpa Fabio Lai Tiziana Castelli Alberto Casu Marco Maltagliati Ferruccio 《Hydrobiologia》2021,848(18):4225-4240
Hydrobiologia - Recent research hypothesised that the Siculo-Tunisian Strait might fit, at least for some species, the picture of a genetic transitional zone instead of a sharp genetic break... 相似文献
182.
Ischemic heart diseases are a global health problem that requires the search for alternative therapies to the current treatments. Thus, an understanding of how cardiomyogenic signals can affect cellular behavior would allow us to create strategies to improve the cell recovery in damaged tissues. In this study, we aimed to evaluate the effects of the conditioned medium (CM), collected at different time points during in vitro cardiomyogenesis of human embryonic stem cells (hESCs), to direct cell behavior. We assayed different cell types to demonstrate noncytotoxic effects from the collected CM and that the CM obtained at initial time points of cardiomyogenic differentiation could promote the cell proliferation. Otherwise, the secretome derived from cardiac committed cells during cardiomyogenesis was unable to improve angiogenesis or migration in endothelial cells, and ineffective to stimulate the differentiation of cardioblasts or increase the differentiation efficiency of hESC. Therefore, we demonstrated that the effectiveness of the CM response varies depending on the cell type and the differentiation step of hESC‐derived cardiomyocytes. 相似文献
183.
Maglieri Veronica Riccobono Marco Germain Giunchi Dimitri Palagi Elisabetta 《Journal of Ethology》2021,39(3):287-296
Journal of Ethology - By gathering data on people during their ordinary daily activities, we tested if looking at, but not manipulating, smartphones led to a mimicry response in the observer.... 相似文献
184.
185.
186.
Yanny Ritchot Marco FestaBianchet David Coltman Fanie Pelletier 《Ecology and evolution》2021,11(11):6829
In long‐lived polygynous species, male reproductive success is often monopolized by a few mature dominant individuals. Young males are generally too small to be dominant and may employ alternative tactics; however, little is known about the determinants of reproductive success for young males. Understanding the causes and consequences of variability in early reproductive success may be crucial to assess the strength of sexual selection and possible long‐term trade‐offs among life‐history traits. Selective pressures driven by fluctuating environmental conditions may depend on age class. We evaluated the determinants of reproduction in male bighorn sheep (Ovis canadensis) aged 2–4 years using 30 years of individual‐level data. These young males cannot defend estrous ewes and use alternative mating tactics. We also investigated how the age of first detected reproduction was correlated to lifetime reproductive success and longevity. We found that reproductive success of males aged 3 years was positively correlated to body mass, to the proportion of males aged 2–4 years in the competitor pool, and to the number of females available per adult male. These results suggest that reproductive success depends on both competitive ability and population age–sex structure. None of these variables, however, had significant effects on the reproductive success of males aged 2 or 4 years. Known reproduction before the age of five increased lifetime reproductive success but decreased longevity, suggesting a long‐term survival cost of early reproduction. Our analyses reveal that both individual‐level phenotypic and population‐level demographic variables influence reproductive success by young males and provide a rare assessment of fitness trade‐offs in wild polygynous males. 相似文献
187.
188.
Roman Jansen Holger Morschett Dennis Hasenklever Matthias Moch Wolfgang Wiechert Marco Oldiges 《Biotechnology progress》2021,37(4):e3144
In recent years, many fungal genomes have become publicly available. In combination with novel gene editing tools, this allows for accelerated strain construction, making filamentous fungi even more interesting for the production of valuable products. However, besides their extraordinary production and secretion capacities, fungi most often exhibit challenging morphologies, which need to be screened for the best operational window. Thereby, combining genetic diversity with various environmental parameters results in a large parameter space, creating a strong demand for time-efficient phenotyping technologies. Microbioreactor systems, which have been well established for bacterial organisms, enable an increased cultivation throughput via parallelization and miniaturization, as well as enhanced process insight via non-invasive online monitoring. Nevertheless, only few reports about microtiter plate cultivation for filamentous fungi in general and even less with online monitoring exist in literature. Moreover, screening under batch conditions in microscale, when a fed-batch process is performed in large-scale might even lead to the wrong identification of optimized parameters. Therefore, in this study a novel workflow for Aspergillus niger was developed, allowing for up to 48 parallel microbioreactor cultivations in batch as well as fed-batch mode. This workflow was validated against lab-scale bioreactor cultivations to proof scalability. With the optimized cultivation protocol, three different micro-scale fed-batch strategies were tested to identify the best protein production conditions for intracellular model product GFP. Subsequently, the best feeding strategy was again validated in a lab-scale bioreactor. 相似文献
189.
Talles Bruno Oliveira dos Anjos Francesco Polazzo Alba ArenasSnchez Laura Cherta Roberto Ascari Sonia Migliorati Marco Vighi Andreu Rico 《Ecology and evolution》2021,11(9):4046
Pesticides, nutrients, and ecological stressors such as competition or predation co‐occur in freshwater ecosystems impacted by agriculture. The extent to which combinations of these stressors affect aquatic populations and the role of nutrients availability in modulating these responses requires further understanding. In this study, we assessed how pesticides affecting different taxonomic groups and predation influence the response of Daphnia pulex populations under different trophic conditions. An outdoor experiment was designed following a factorial design, with the insecticide chlorpyrifos, the herbicide diuron, and the predation by Notonecta sp. individuals as key stressors. The single impact of each of these stressors, and their binary and tertiary combinations, was evaluated on D. pulex abundance and population structure under mesotrophic and eutrophic conditions for 21 days. Data were analyzed using generalized linear mixed models estimated by means of a novel Bayesian shrinkage technique. Our study shows a significant influence of each of the evaluated stressors on D. pulex abundance; however, the impacts of the herbicide and predation were lower under eutrophic conditions as compared to the mesotrophic ones. We found that binary stressor interactions were generally additive in the mesotrophic scenario, except for the herbicide–predation combination, which resulted in synergistic effects. The impacts of the binary stressor combinations in the eutrophic scenario were classified as antagonistic, except for the insecticide–herbicide combination, which was additive. The tertiary interaction resulted in significant effects on some sampling dates; however, these were rather antagonistic and resembled the most important binary stressor combination in each trophic scenario. Our study shows that the impact of pesticides on freshwater populations depends on the predation pressure, and demonstrates that the combined effect of pesticides and ecological stressors is influenced by the food availability and organism fitness related to the trophic status of freshwater ecosystems. 相似文献
190.
Agnese Brunzini Antonio Gracco Alida Mazzoli Marco Mandolini Steve Manieri Michele Germani 《Computer methods in biomechanics and biomedical engineering》2013,16(13):693-702
AbstractThe paper aims to evaluate the effects caused by a Mandibular Advancement Device (MAD) for Obstructive Sleep Apnoea Syndrome (OSAS) treatment. This study is based on Finite Element Method (FEM) for evaluating the load distribution on temporomandibular joint, especially on the mandibular condyle and disc, and on periodontal ligaments. The stress values on condyle and periodontal ligaments lead authors to consider MAD a safe procedure even for a long period. The obtained results also show the relationship between MAD material and load distribution at the periodontal ligaments. The paper is a step toward future analyses for studying and comparing the effects of MAD features, such as material, shape and dimensions, in order to allow the clinician prescribing the most fitting device. 相似文献