全文获取类型
收费全文 | 2411篇 |
免费 | 132篇 |
国内免费 | 108篇 |
出版年
2023年 | 21篇 |
2022年 | 28篇 |
2021年 | 33篇 |
2020年 | 29篇 |
2019年 | 67篇 |
2018年 | 68篇 |
2017年 | 37篇 |
2016年 | 38篇 |
2015年 | 55篇 |
2014年 | 168篇 |
2013年 | 167篇 |
2012年 | 128篇 |
2011年 | 136篇 |
2010年 | 98篇 |
2009年 | 116篇 |
2008年 | 141篇 |
2007年 | 139篇 |
2006年 | 124篇 |
2005年 | 119篇 |
2004年 | 102篇 |
2003年 | 94篇 |
2002年 | 89篇 |
2001年 | 47篇 |
2000年 | 60篇 |
1999年 | 57篇 |
1998年 | 56篇 |
1997年 | 48篇 |
1996年 | 35篇 |
1995年 | 46篇 |
1994年 | 45篇 |
1993年 | 27篇 |
1992年 | 24篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有2651条查询结果,搜索用时 31 毫秒
1.
Oussama El Far Béatrice Marquèze Christian Leveque Nicole Martin-Moutôt Bethan Lang John Newsom-Davis †Akira Yoshida †Masami Takahashi Michael J. Seagar 《Journal of neurochemistry》1995,64(4):1696-1702
Abstract: In Lambert-Eaton myasthenic syndrome neurotransmitter release is reduced by an autoimmune response directed against the calcium channel complex of the nerve terminal. Autoantibodies were detected by immunoprecipitation assays using solubilized receptors labeled with ligands selective for N-type (125 I-ω conotoxin GVIA) and L-type ([3 H]PN200-110) calcium channels. Sera with a high antibody titer (>3 n M ) against rat brain N-type channels contained autoantibodies that immunoprecipitated neuronal and muscle L-type channels. These IgG fractions stained a 55-kDa protein in immunoblots of purified skeletal muscle dihydropyridine receptor, suggesting that they contain autoantibodies against the β subunit of the calcium channel. A distinct antibody population in the same fractions reacted with a nerve terminal 65-kDa protein that is unrelated to the β subunit and displays properties similar to those of synaptotagmin. 相似文献
2.
Increased Solubility of High-Molecular-Mass Neurofilament Subunit by Suppression of Dephosphorylation: Its Relation to Axonal Transport 总被引:4,自引:1,他引:3
Abstract: To investigate the role of phosphorylation in the turnover and transport of neurofilament (NF) proteins in vivo, we studied their solubility properties and axonal transport in the rat sciatic nerve using phosphatase inhibitors to minimize dephosphorylation during preparation. About 20% of the 200-kDa subunit (NF-H) in the axon was soluble in the 1% Triton-containing buffer under the present conditions, whereas this amount was less and more variable in the absence of phosphatase inhibitors. The 68-kDa subunit (NF-L) was exclusively insoluble and not affected by the inhibitors. Such selective solubilization of NF-H by phosphorylation differed significantly from the in vitro phosphorylation with cyclic AMP-dependent protein kinase, which resulted in NF disassembly. The carboxy-terminal phosphorylation state of NF-H probed with the phosphorylation-sensitive antibodies was also not directly related to solubility. The solubility of NF-H did not differ along the nerve. In contrast, the solubility of l -[35 S]methionine-labeled, transported NF-H was lowest at the peak of radioactivity. Higher solubility at the leading edge, regardless of its location along the nerve, indicates that NF-H solubility is positively correlated with the rate of NF transport. 相似文献
3.
4.
G. Tripodi 《Protoplasma》1980,103(2):163-168
Summary Leaves ofAcanthus kept in an environment with a low concentration of carbon dioxide but connected to plants growing in open air show at electron microscopy level chloroplasts with anomalous stain of the thylakoids. Intra- and interthylakoidal spaces are electron opaque, while the outer protein layers appear formed by electron translucent globular units on which a dark deposit is visible in correspondence of the end-granal membranes and frets. It is suggested that the stain is in some way related to compounds active in light dependent photosynthesis which strongly reduce the osmium tetroxide.Supported by a grant of C.N.R. (Rome). 相似文献
5.
G. Arias‐Robledo T. Stark R. L. Wall J. R. Stevens 《Medical and veterinary entomology》2019,33(1):131-139
The blow fly genus Lucilia is composed largely of saprophages and facultative myasis agents, including the economically important species Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) and Lucilia sericata (Meigen). Only one species is generally recognized as an obligate agent of myiasis, Lucilia bufonivora Moniez, and this is an obligate parasite of toads. Lucilia silvarum (Meigen), a sister species, behaves mainly as a carrion breeder; however, it has also been reported as a facultative parasite of amphibians. Morphologically, these species are almost identical, and historically this has led to misidentification, taxonomic ambiguity and a paucity of studies of L. bufonivora. In this study, dipterous larvae were analysed from toad myiasis cases from the U.K., The Netherlands and Switzerland, together with adult specimens of fly species implicated in amphibian parasitism: L. bufonivora, L. silvarum and Lucilia elongata Shannon (from North America). Partial sequences of two genes, cox1 and ef1α, were amplified. Seven additional blow fly species were analysed as outgroups. Bayesian inference trees of cox1, ef1α and a combined‐gene dataset were constructed. All larvae isolated from toads were identified as L. bufonivora and no specimens of L. silvarum were implicated in amphibian myiasis. This study confirms L. silvarum and L. bufonivora as distinct sister species and provides unambiguous molecular identification of L. bufonivora. 相似文献
6.
Kenneth Lundström 《FEMS microbiology letters》1984,23(1):65-70
Abstract The molecularly cloned gene encoding the vesicular stomatitis virus (VSV) membrane glycoprotein G was modified and joined to a Bacillus subtilis secretion vector constructed from the plasmid pUB110 and containing the promoter and signal sequence regions of the α-amylase (a secretory protein) gene from Bacillus amyloliquefaciens . The regions encoding the NH2 -terminal signal peptide and the COOH-terminal hydrophobic transmembrane domains of the VSV gene were deleted to facilitate the secretion of the G protein in soluble form. The truncated G protein was found to be expressed in B. subtilis . The expression level was low, probably due to rapid proteolytic degradation of the protein and, contrary to what was expected, almost all of the protein remained cell-associated. 相似文献
7.
8.
Although the amino acid glutamate is used as an intercellular signaling molecule for normal bone homeostasis, little is known regarding its possible role in the metabolic disruption characteristic of bone metastasis. We have previously shown in vitro that cancer cell lines relevant to bone metastasis release glutamate into the extracellular environment. This study demonstrates the expression of multiple glutamate transporters in cancer cell lines of non-central nervous system origin. Furthermore, we identify the molecular mechanism responsible for glutamate export and show that this system can be inhibited pharmacologically. By highlighting that glutamate secretion is a common biological feature of cancer cells, this study suggests that tumor-derived glutamate could interfere with glutamate-dependent intercellular signaling in normal bone. Pharmacological interference with cancer cell glutamate release may be a viable option for limiting host bone response to invading tumor cells in bone metastasis. 相似文献
9.
Peptidomimetic analogs of the peptide RRASVA, known as the “minimal substrate” of the catalytic subunit of the cAMP-dependent protein kinase (PKA), were synthesized by consecutive replacement of natural amino acids by their aza-β3 analogs. The peptidomimetics were tested as PKA substrates and the kinetic parameters of the phosphorylation reaction were determined. It was found that the interaction of these peptidomimetics with the enzyme active center was sensitive to the location of the backbone modification, while the maximal rate of the reaction was practically not affected by the structure of substrates. The pattern of molecular recognition of peptidomimetics was in agreement with the results of structure modeling and also with the results of computational docking study of peptide and peptidomimetic substrates with the active center of PKA. It was concluded that the specificity determining factors which govern substrate recognition by the enzyme should be grouped along the phosphorylatable substrate, and such clustering might open new perspectives for pharmacophore design of peptides and peptide-like ligands. 相似文献
10.
Naohito Ohmi Bhargava M. Madhu Irwin M. Arias 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,675(2):276-280
Following administration of phenobarbital to rats, liver ligandin content, bilirubin binding, glutathione-S-transferase and steriod isomerase activities by 150% and the 22 000-dalton subunit was selectively increased. Following adminstration of 3′-methyl-N,N-dimethyl-4-aminoazobenzene, rat liver ligandin content and steroid isomerase decrased by 65%, glutathione-S-transferase incrased by 100%, bilirubin binding was abolished, and the relative proportion of the 22 000- and 25 000-dalton subunits remained unchanged. 相似文献