全文获取类型
收费全文 | 5927篇 |
免费 | 399篇 |
国内免费 | 1篇 |
出版年
2023年 | 38篇 |
2022年 | 86篇 |
2021年 | 147篇 |
2020年 | 100篇 |
2019年 | 125篇 |
2018年 | 139篇 |
2017年 | 128篇 |
2016年 | 204篇 |
2015年 | 306篇 |
2014年 | 341篇 |
2013年 | 457篇 |
2012年 | 539篇 |
2011年 | 461篇 |
2010年 | 308篇 |
2009年 | 273篇 |
2008年 | 377篇 |
2007年 | 368篇 |
2006年 | 324篇 |
2005年 | 276篇 |
2004年 | 242篇 |
2003年 | 240篇 |
2002年 | 193篇 |
2001年 | 47篇 |
2000年 | 60篇 |
1999年 | 55篇 |
1998年 | 32篇 |
1997年 | 30篇 |
1996年 | 45篇 |
1995年 | 33篇 |
1994年 | 27篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有6327条查询结果,搜索用时 15 毫秒
1.
2.
Filippo Genovese Stefania Ferrari Giambattista Guaitoli Monica Caselli M. Paola Costi Glauco Ponterini 《Protein science : a publication of the Protein Society》2010,19(5):1023-1030
An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency. 相似文献
3.
Sequence complexity and diversity of polyadenylated RNA molecules transcribed in human myeloid cells
4.
Amy Chapman Gonzalo Gonzales Wayne R. Burrowes Paul Assanah Bernadette Iannone Michael K. Leung George B. Stefano 《Cellular and molecular neurobiology》1984,4(2):143-155
In Mytilus and Leucophaea the high-affinity binding site density is significantly lower in old animals than in young animals, whereas the low-affinity site density remains unchanged. In Mytilus the estimated met-enkephalin and met-enkephalin-Arg6-Phe7 levels are significantly higher in old than in young animals. In Leucophaea only the met-enkephalin level can be determined, and it is also higher in old animals. The decrease in the high-affinity binding site density and the corresponding increase in endogenous enkephalin levels suggest the existence of an opioid compensatory mechanism associated with the aging process. In Mytilus there is a demonstrated decrease with age in intraganglionic dopamine levels in response to applied opiates. In addition, the inhibition of dopamine-stimulated adenylate cyclase activity by opiates also decreases in older animals. In Leucophaea the sex difference in opioid binding densities diminishes with age. 相似文献
5.
It has long been debated whether the mind consists of specialized and independently evolving modules, or whether and to what extent a general factor accounts for the variance in performance across different cognitive domains. In this study, we used a hierarchical Bayesian model to re-analyse individual level data collected on seven primate species (chimpanzees, bonobos, orangutans, gorillas, spider monkeys, brown capuchin monkeys and long-tailed macaques) across 17 tasks within four domains (inhibition, memory, transposition and support). Our modelling approach evidenced the existence of both a domain-specific factor and a species factor, each accounting for the same amount (17%) of the observed variance. In contrast, inter-individual differences played a minimal role. These results support the hypothesis that the mind of primates is (at least partially) modular, with domain-specific cognitive skills undergoing different evolutionary pressures in different species in response to specific ecological and social demands. 相似文献
6.
7.
8.
9.
Romano Gellini Filippo Bussotti Davide Bettini Paolo Grossoni Alessandro Bottacci 《Plant biosystems》2013,147(3-4):481-504
Abstract We propose a study of the main species belonging to the genus Quercus in Italy, characterized and identified by means of leaf surface observation, with special attention devoted to waxes, trichomes and stomata. Comparing our results with the classification proposed by SCHWARZ (1984), we find that species belonging to Schwarz's subgenus Quercus are recognizable because their waxes are structured in vertical scales; the two other subgenera (Sclerophyllodrys and Cerris) present smooth wax structures, their distinctive feature being the shape of the stomatal rima, which is roundish in Sclerophyllodrys and elliptical in Cerris. The study characterizes Quercus pubescens Willd. and Quercus petraea Liebl. by analyzing some morphometric traits; but the authors feel that further research is needed on these critical taxonomic entities. Lastly, the study examines forms of was degeneration correlated to the phenomenon known as oak decline. 相似文献
10.
Cristina Cereda Emanuela Leoni Pamela Milani Orietta Pansarasa Giuliano Mazzini Stefania Guareschi Elena Alvisi Andrea Ghiroldi Luca Diamanti Stefano Bernuzzi Mauro Ceroni Emanuela Cova 《PloS one》2013,8(10)
Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease. 相似文献