全文获取类型
收费全文 | 5269篇 |
免费 | 437篇 |
国内免费 | 281篇 |
专业分类
5987篇 |
出版年
2024年 | 11篇 |
2023年 | 47篇 |
2022年 | 123篇 |
2021年 | 208篇 |
2020年 | 130篇 |
2019年 | 182篇 |
2018年 | 212篇 |
2017年 | 139篇 |
2016年 | 234篇 |
2015年 | 329篇 |
2014年 | 386篇 |
2013年 | 338篇 |
2012年 | 466篇 |
2011年 | 433篇 |
2010年 | 272篇 |
2009年 | 267篇 |
2008年 | 296篇 |
2007年 | 269篇 |
2006年 | 234篇 |
2005年 | 209篇 |
2004年 | 192篇 |
2003年 | 173篇 |
2002年 | 171篇 |
2001年 | 100篇 |
2000年 | 67篇 |
1999年 | 72篇 |
1998年 | 63篇 |
1997年 | 44篇 |
1996年 | 40篇 |
1995年 | 35篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有5987条查询结果,搜索用时 15 毫秒
71.
An Y Shao Y Alory C Matteson J Sakisaka T Chen W Gibbs RA Wilson IA Balch WE 《Structure (London, England : 1993)》2003,11(3):347-357
Rab GTPases, key regulators of membrane targeting and fusion, require the covalent attachment of geranylgeranyl lipids to their C terminus for function. To elucidate the role of lipid in Rab recycling, we have determined the crystal structure of Rab guanine nucleotide dissociation inhibitor (alphaGDI) in complex with a geranylgeranyl (GG) ligand (H(2)N-Cys-(S-GG)-OMe). The lipid is bound beneath the Rab binding platform in a shallow hydrophobic groove. Mutation of the binding pocket in the brain-specific alphaGDI leads to mental retardation. Strikingly, lipid binding acts through a conserved allosteric switching mechanism to promote release of the GDI-Rab[GDP] complex from the membrane. 相似文献
72.
Van Hemelrijck A Vermijlen D Hachimi-Idrissi S Sarre S Ebinger G Michotte Y 《Journal of neurochemistry》2003,87(1):66-75
The relationship between glutamate and dopamine release, apoptosis and ischaemic damage was studied following induction of transient focal cerebral ischaemia under normothermic (37 degrees C) and postischaemic (resuscitative) mild hypothermic (34 degrees C for 2 h) conditions in sevoflurane anaesthetized male Wistar rats. Focal ischaemia was induced by infusing endothelin-1 adjacent to the middle cerebral artery. In vivo microdialysis was used to sample glutamate and dopamine from striatum and parietal cortex of the ipsilateral hemisphere. The volume of ischaemic damage and the degree of apoptosis were determined 24 h after the insult. In both striatum and cortex of the normothermic group an initial increase in extracellular glutamate and dopamine levels following endothelin-1 infusion was observed. Striatal glutamate levels remained enhanced (250% of baseline) throughout the experiment, while the other neurotransmitter levels returned to baseline values. Hypothermia significantly attenuated the endothelin-1 induced glutamate release in the striatum. It also reduced apoptosis and infarct volume in the cortex. These results indicate that: (i) postischaemic mild hypothermia exerts its neuroprotective effect by inhibiting apoptosis in the ischaemic penumbral region; and (ii) this effect is not associated with an attenuation of glutamate or dopamine release in the cortex. 相似文献
73.
Boudrez A Beullens M Waelkens E Stalmans W Bollen M 《The Journal of biological chemistry》2002,277(35):31834-31841
NIPP1 is a ubiquitously expressed nuclear protein that functions both as a regulator of protein Ser/Thr phosphatase-1 and as a splicing factor. The N-terminal part of NIPP1 consists of a phosphothreonine-interacting Forkhead-associated (FHA) domain. We show here that the FHA domain of NIPP1 interacts in vitro and in vivo with a TP dipeptide-rich fragment of the splicing factor SAP155/SF3b(155), a component of the U2 small nuclear ribonucleoprotein particle. The NIPP1-SAP155 interaction was entirely dependent on the phosphorylation of specific TP motifs in SAP155. Mutagenesis and competition studies revealed that various phosphorylated TP motifs competed for binding to the same site in the FHA domain. The SAP155 kinases in cell lysates were blocked by the Ca(2+) chelator EGTA and by the cyclin-dependent protein kinase inhibitor roscovitine. The phosphorylation level of SAP155 was dramatically increased during mitosis, and accordingly the activity of SAP155 kinases was augmented in mitotic lysates. We discuss how the interaction between NIPP1 and SAP155 could contribute to spliceosome (dis)assembly and the catalytic steps of splicing. 相似文献
74.
Cho SJ Park SR Kim MK Lim WJ Ryu SK An CL Hong SY Lee YH Jeong SG Cho YU Yun HD 《Bioscience, biotechnology, and biochemistry》2002,66(6):1270-1275
A bacterial strain, designated CY22, was isolated from the interior of balloon flower (Platycodon grandiflorum) root in the Republic of Korea. The isolate coproduced an iturin-like antifungal compound and a surfactin-like potent biosurfactant. Analysis of the 16S-rDNA of strain CY22 showed that the isolate was a member of Bacillus. High similarities were observed between strain CY22 and Bacillus sp. TKSP 24, and between strain CY22 and B. subtilis 168. Phylogenetic analysis based on 16S-rDNA sequences showed that strain CY22 was closely related to Bacillus sp. The main whole-cell fatty acids were anteiso-C15:0 (37%), C17:0 (5.1%), and iso-C15:0 (27.7%). DNA G+C content was 54 mol%. Based on phylogenetic inference, phenotypic and chemotaxonomic characteristics, this endophytic strain Bacillus sp. CY22 was assigned to the genus Bacillus. 相似文献
75.
Zhang S Zhou W Ding Y He X Zhang H An J Gao F Heckmann K Liang A Rao Z 《Protein and peptide letters》2002,9(1):81-85
eRF1a, one of the class-I release factors from ciliate Euplotes octocarinatus, has been crystallized by the vapor-diffusion method using polyethylene glycol 4000 as the precipitant at pH 7.5. The crystal belongs to space group P2(1) and the unit-cell parameters are a=90.4, b=107.9, c=114.8A, beta=94.2 degrees. There appear to be four eRF1a molecules in the asymmetric unit. 相似文献
76.
Park SR Cho SJ Kim MK Ryu SK Lim WJ An CL Hong SY Kim JH Kim H Yun HD 《Biochemical and biophysical research communications》2002,291(2):425-430
The phytopathogenic bacterium Pectobacteium chrysanthemi PY35 secretes Cel5Z endoglucanase belonging to the glycoside hydrolase family 5 of EC 3.2.1.4. The mutation of cel5Z::Omega gene was constructed by cloning the 2.0-kb SmaI fragment containing the streptomycin/spectinomycin-resistance gene of pHP45(Omega) into the BalI site of pPY100. The insertion of Omega fragment generated a new stop codon, removing the Ser/Thr-rich linker region and the cellulose binding domain (CBD) in the C-terminal region of cel5Z gene. By subsequent subcloning from this 4.9-kb fragment (pPY1001), a 1.0-kb (pPY1002) fragment was obtained and designated as cel5Z::Omega. The cel5Z::Omega gene had an open reading frame (ORF) of 1011 bp, encoding 336 amino acids, starting with an ATG codon and ending with a new TGA stop codon. The molecular mass of the Cel5Z::Omega protein in E. coli transformant appeared to be 32 kDa by SDS-PAGE analysis in the presence of carboxymethyl-cellulose (CMC). The Cel5Z::Omega protein hydrolyzed CMC with 1.7-fold higher activity than the intact Cel5Z cellulase. 相似文献
77.
Soybean peroxidase (20 mg) catalyzed the oxidative polymerization of cardanol in 2-propanol/phospate buffer solution (25 ml, 1:1 v/v) and yielded 62% polycardanol over 6 h. Cobalt naphthenate (0.5% w/w) catalyzed the crosslinking of polycardanol and the final hardness of crosslinked polycardanol film exceeded 9 H scale as pencil scratch hardness, which shows a high potential as a commercial coating material. In addition, it showed an excellent anti-biofouling activity to Pseudomonas fluorescens compared to other polymeric materials such as polypropylene. 相似文献
78.
Brandalise M Maia IG Borecký J Vercesi AE Arruda P 《Journal of bioenergetics and biomembranes》2003,35(3):203-209
An Arabidopsis thaliana cDNA clone encoding a plant uncoupling mitochondrial protein (AtPUMP1) was overexpressed in transgenic tobacco plants. Analysis of the AtPUMP1 mRNA content in the transgenic lines, determined by Northernblot, revealed variable levels of transgene expression. Antibody probing ofWestern blots of mitochondrial proteins from three independent transgenic lines showed significant accumulation of AtPUMP1 in this organelle. Overproduction of AtPUMP1 in transgenic tobacco plants led to a significantincrease in tolerance to oxidative stress promoted by exogenous hydrogen peroxide as compared to wild-type control plants. These results provide thefirst biological evidence for a role of PUMP in protection of plant cells against oxidative stress damage. 相似文献
79.
Optimizing expression and purification from cell culture medium of trispecific recombinant antibody derivatives 总被引:3,自引:0,他引:3
Willems A Leoen J Schoonooghe S Grooten J Mertens N 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2003,786(1-2):161-176
Antibody fragments offer the possibility to build multifunctional manifolds tailored to meet a large variety of needs. We optimized the production of a manifold consisting of one (bibody) or two (tribody) single-chain variable fragments coupled to the C-terminus of Fab chains. Different strong mammalian promoters were compared and the influence of expression media on production and recovery was investigated. Since the physical and chemical nature of these molecules largely depends on the nature of the antibody building blocks incorporated, a generally applicable process for the purification of recombinant antibody derivatives from serum containing mammalian cell culture medium was designed. To this end we compared protein L, hydroxyapatite, immobilized metal affinity chromatography, cation-exchange chromatography and hydrophobic charge induction chromatography. 相似文献
80.