全文获取类型
收费全文 | 4674篇 |
免费 | 411篇 |
出版年
2023年 | 41篇 |
2022年 | 80篇 |
2021年 | 205篇 |
2020年 | 85篇 |
2019年 | 122篇 |
2018年 | 136篇 |
2017年 | 126篇 |
2016年 | 200篇 |
2015年 | 349篇 |
2014年 | 367篇 |
2013年 | 387篇 |
2012年 | 503篇 |
2011年 | 465篇 |
2010年 | 266篇 |
2009年 | 191篇 |
2008年 | 264篇 |
2007年 | 242篇 |
2006年 | 197篇 |
2005年 | 180篇 |
2004年 | 129篇 |
2003年 | 149篇 |
2002年 | 128篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1982年 | 5篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 6篇 |
1969年 | 5篇 |
1968年 | 4篇 |
1967年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有5085条查询结果,搜索用时 46 毫秒
1.
2.
Antoine Wystrach Sebastian Schwarz Patrick Schultheiss Guy Beugnon Ken Cheng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):167-179
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants)
to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised
natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through
the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations
between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the
positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants
(translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants
might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of
landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable. 相似文献
3.
zge Karayel Francesca Tonelli Sebastian Virreira Winter Phillip E. Geyer Ying Fan Esther M. Sammler Dario R. Alessi Martin Steger Matthias Mann 《Molecular & cellular proteomics : MCP》2020,19(9):1546-1560
- Download : Download high-res image (63KB)
- Download : Download full-size image
- •MS-based clinical assay that accurately determines phospho Rab10 occupancy.
- •Stable isotope labeled phosphopeptide injected as a standard with endogenous tryptic phospho Rab peptide for accurate ratio determination.
- •Determination of pRab levels in neutrophils of Parkinson disease patients.
- •Relevance of pRab levels as marker of PD.
4.
Krzysztof J. Gorgolewski Dan Lurie Sebastian Urchs Judy A. Kipping R. Cameron Craddock Michael P. Milham Daniel S. Margulies Jonathan Smallwood 《PloS one》2014,9(5)
Although neural activity often reflects the processing of external inputs, intrinsic fluctuations in activity have been observed throughout the brain. These may relate to patterns of self-generated thought that can occur while not performing goal-driven tasks. To understand the relationship between self-generated mental activity and intrinsic neural fluctuations, we developed the New York Cognition Questionnaire (NYC-Q) to assess the content and form of an individual''s experiences during the acquisition of resting-state fMRI data. The data were collected as a part of the Nathan Kline Rockland Enhanced sample. We decomposed NYC-Q scores using exploratory factor analysis and found that self-reported thoughts clustered into distinct dimensions of content (future related, past related, positive, negative, and social) and form (words, images, and specificity). We used these components to perform an individual difference analysis exploring how differences in the types of self-generated thoughts relate to whole brain measures of intrinsic brain activity (fractional amplitude of low frequency fluctuations, regional homogeneity, and degree centrality). We found patterns of self-generated thoughts related to changes that were distributed across a wide range of cortical areas. For example, individuals who reported greater imagery exhibited greater low frequency fluctuations in a region of perigenual cingulate cortex, a region that is known to participate in the so-called default-mode network. We also found certain forms of thought were associated with other areas, such as primary visual cortex, the insula, and the cerebellum. For example, individuals who reported greater future thought exhibited less homogeneous neural fluctuations in a region of lateral occipital cortex, a result that is consistent with the claim that particular types of self-generated thought depend on processes that are decoupled from sensory processes. These data provide evidence that self-generated thought is a heterogeneous category of experience and that studying its content can be helpful in understanding brain dynamics. 相似文献
5.
Sebastian Kalamajski Dominique Bihan Arkadiusz Bonna Kristofer Rubin Richard W. Farndale 《The Journal of biological chemistry》2016,291(15):7951-7960
The hallmark of fibrotic disorders is a highly cross-linked and dense collagen matrix, a property driven by the oxidative action of lysyl oxidase. Other fibrosis-associated proteins also contribute to the final collagen matrix properties, one of which is fibromodulin. Its interactions with collagen affect collagen cross-linking, packing, and fibril diameter. We investigated the possibility that a specific relationship exists between fibromodulin and lysyl oxidase, potentially imparting a specific collagen matrix phenotype. We mapped the fibromodulin-collagen interaction sites using the collagen II and III Toolkit peptide libraries. Fibromodulin interacted with the peptides containing the known collagen cross-linking sites and the MMP-1 cleavage site in collagens I and II. Interestingly, the interaction sites are closely aligned within the quarter-staggered collagen fibril, suggesting a multivalent interaction between fibromodulin and several collagen helices. Furthermore, we detected an interaction between fibromodulin and lysyl oxidase (a major collagen cross-linking enzyme) and mapped the interaction site to 12 N-terminal amino acids on fibromodulin. This interaction also increases the activity of lysyl oxidase. Together, the data suggest a fibromodulin-modulated collagen cross-linking mechanism where fibromodulin binds to a specific part of the collagen domain and also forms a complex with lysyl oxidase, targeting the enzyme toward specific cross-linking sites. 相似文献
6.
7.
Steady state agonist-antagonist relations have been derived for a general version of a cyclic model of glucocorticoid-receptor kinetics. The model was previously shown to account quantitatively for the transient and steady state distribution of hormone-receptor complexes formed in thymus cells by several glucocorticoids. Agonist-antagonist properties of a steroid in the model are expressed quantitatively by its "agonist activity" A, the steady state ratio of nuclear-bound to total complexes it forms. For a pure agonist A = 1, for a pure antagonist A = 0. This ratio is found to be independent of steroid concentration and a function only of the rate constants of reactions involving complexes formed by the steroid. Analysis of the dependence of A on each rate constant reveals how each reaction in the cyclic model--activation, nuclear binding, dissociation of activated and nuclear-bound complexes--influences antagonist properties. The steady state interaction of an antagonist with an agonist is shown to be governed by relations that are indistinguishable from competition relations for the simplest equilibrium system, and to yield dose-response curves that are very similar to those produced by two-state allosteric models of steroid hormone antagonism, despite the fact that the cyclic model includes no allosteric mechanisms. With steroids for which relevant rate constants can be measured, the model is directly testable. Limitations of the model arise from lack of information about the nuclear events that lead to biological activity following binding of activated complexes to the nucleus. 相似文献
8.
Dexamethasone causes translocation of glucose transporters from the plasma membrane to an intracellular site in human fibroblasts 总被引:3,自引:0,他引:3
To investigate the mechanism by which glucocorticoids inhibit glucose transport in peripheral tissues, we have used a monoclonal antibody directed against the human glucose transporter to measure the relative amounts of glucose transporter polypeptide in various cell fractions of human foreskin fibroblasts after treatment with and without dexamethasone. In cells treated for 4 h with 100 nM dexamethasone, a decrease of 48% in glucose transport was accompanied by a decrease of 40% in the amount of glucose transporter polypeptide in a plasma membrane fraction enriched 10-fold in 5'-nucleotidase activity and a 78% increase in the amount of transporter polypeptide in a fraction of putative intracellular membranes, designated P2. There was no significant change in the amount of transporter polypeptide in whole cell lysates. Insulin (200 nM) stimulated glucose transport in basal fibroblasts by only 9%. However, addition of insulin for 30 min to cells that had been treated for 4 h with dexamethasone completely reversed the dexamethasone-induced decrease in glucose transport and also reversed the dexamethasone-induced changes in glucose transporter polypeptide content of the plasma membrane and P2 fractions. From these observations we conclude that dexamethasone decreases glucose transport by causing translocation of glucose transporters from the plasma membrane to an internal location and that insulin reverses the dexamethasone effect by reversing the translocation. 相似文献
9.
Purification and amino-terminal amino acid sequence of an apurinic/apyrimidinic endonuclease from calf thymus. 总被引:7,自引:4,他引:3
An apurinic/apyrimidinic (AP) endonuclease (E.C.3.1.25.2) has been purified 1100 fold to apparent homogeneity from calf thymus by a series of ion exchange, gel filtration and hydrophobic interaction chromatographies. The purified AP endonuclease is a monomeric protein with an apparent molecular weight on SDS-PAGE of 37,000. On gel filtration the protein behaves as a protein of apparent molecular weight 40,000. DNA cleavage by this AP endonuclease is dependent on the presence of AP sites in the DNA. DNA cleavage requires the divalent cation Mg2+ and has a broad pH optimum of 7.5-9.0. Maximal rates of catalysis occur at NaCl or KCl concentrations of 25-50 mM. The amino acid composition and the amino-terminal amino acid sequence for this AP endonuclease are presented. Comparison of the properties of this AP endonuclease purified from calf thymus with the reported properties of the human AP endonuclease purified from HeLa cells or placenta indicate that the properties of such an AP endonuclease are highly conserved in these two mammalian species. 相似文献
10.
Timothy J. Strabala Sebastian Y. Bednarek Gregory Bertoni Richard M. Amasino 《Molecular & general genetics : MGG》1989,216(2-3):388-394
Summary A 1.9 kb clone of the T-DNA region of the Agrobacterium tumefaciens Ti plasmid Bo542 which exhibited homology to the isopentenyl transferase (ipt) locus of pTiA6 was identified by low stringency DNA hybridization. Introduction of this segment of pTiBo542 DNA into cells of Nicotiana tabacum or N. glauca caused tumor formation in vivo, and allowed hormone independent growth in vitro. Furthermore, this DNA segment complemented ipt mutant strains of A. tumefaciens, restoring their ability to cause tumors on Kalanchöe leaves and tomato stems. The complete DNA sequence of this segment has been determined, revealing an open reading frame homologous to other known Agrobacterium ipt genes. 相似文献