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201.
Elmasri H Winkler C Liedtke D Sasado T Morinaga C Suwa H Niwa K Henrich T Hirose Y Yasuoka A Yoda H Watanabe T Deguchi T Iwanami N Kunimatsu S Osakada M Loosli F Quiring R Carl M Grabher C Winkler S Del Bene F Wittbrodt J Abe K Takahama Y Takahashi K Katada T Nishina H Kondoh H Furutani-Seiki M 《Mechanisms of development》2004,121(7-8):659-671
The metameric structure of the vertebrate trunk is generated by repeated formation of somites from the unsegmented presomitic mesoderm (PSM). We report the initial characterization of nine different mutants affecting segmentation that were isolated in a large-scale mutagenesis screen in Medaka (Oryzias latipes). Four mutants were identified that show a complete or partial absence of somites or somite boundaries. In addition, five mutations were found that cause fused somites or somites with irregular sizes and shapes. In situ hybridization analysis using specific markers involved in the segmentation clock and antero-posterior (A-P) polarity of somites revealed that the nine mutants can be compiled into two groups. In group 1, mutants exhibit defects in tailbud formation and PSM prepatterning, whereas A-P identity in the somites is defective in group 2 mutants. Three mutants (planlos, pll; schnelles ende, sne; samidare, sam) have characteristic phenotypes that are similar to those in zebrafish mutants affected in the Delta/Notch signaling pathway. The majority of mutants, however, exhibit somitic phenotypes distinct from those found in zebrafish, such as individually fused somites and irregular somite sizes. Thus, these Medaka mutants can be expected to provide clues to uncovering novel components essential for somitogenesis. 相似文献
202.
Dynamics of polymorphism of acidocalcisomes in<Emphasis Type="Italic"> Leishmania</Emphasis> parasites 总被引:2,自引:1,他引:1
Miranda K Docampo R Grillo O Franzen A Attias M Vercesi A Plattner H Hentschel J de Souza W 《Histochemistry and cell biology》2004,121(5):407-418
Growth of Leishmania mexicana amazonensis promastigotes in different culture media resulted in structurally and chemically different acidocalcisomes. When grown in SDM-79 medium, the promastigotes showed large spherical acidocalcisomes of up to 1.2 m diameter distributed throughout the cell. X-ray microanalysis and elemental mapping of the organelles showed large amounts of oxygen, phosphorus, sodium, potassium, magnesium, calcium, and zinc. Immunofluorescence microscopy using antisera raised against a peptide sequence of the vacuolar-type proton pyrophosphatase of Arabidopsis thaliana that is conserved in the Leishmania enzyme, indicated localization in acidocalcisomes. When cells were transferred to Warrens medium, the acidocalcisomes transformed from spherical into branched tubular organelles. The labeling pattern of the vacuolar proton-pyrophosphatase, considered as a marker for the organelle, changed accompanying the structural changes of the acidocalcisomes, and the enzyme showed an apparently lower proton-transporting activity when measured in digitonin-permeabilized promastigotes. X-ray microanalysis and elemental mapping of these structures revealed the additional presence of iron. Together, the results reveal that the morphology and composition of acidocalcisomes are greatly influenced by the culture conditions.Electronic Supplementary Material Supplementary material is available in the online version of this article at 相似文献
203.
A divergent ADP/ATP carrier in the hydrogenosomes of Trichomonas gallinae argues for an independent origin of these organelles 总被引:2,自引:0,他引:2
Tjaden J Haferkamp I Boxma B Tielens AG Huynen M Hackstein JH 《Molecular microbiology》2004,51(5):1439-1446
The evolution of mitochondrial ADP and ATP exchanging proteins (AACs) highlights a key event in the evolution of the eukaryotic cell, as ATP exporting carriers were indispensable in establishing the role of mitochondria as ATP-generating cellular organelles. Hydrogenosomes, i.e. ATP- and hydrogen-generating organelles of certain anaerobic unicellular eukaryotes, are believed to have evolved from the same ancestral endosymbiont that gave rise to present day mitochondria. Notably, the hydrogenosomes of the parasitic anaerobic flagellate Trichomonas seemed to be deficient in mitochondrial-type AACs. Instead, HMP 31, a different member of the mitochondrial carrier family (MCF) with a hitherto unknown function, is abundant in the hydrogenosomal membranes of Trichomonas vaginalis. Here we show that the homologous HMP 31 of closely related Trichomonas gallinae specifically transports ADP and ATP with high efficiency, as do genuine mitochondrial AACs. However, phylogenetic analysis and its resistance against bongkrekic acid (BKA, an efficient inhibitor of mitochondrial-type AACs) identify HMP 31 as a member of the mitochondrial carrier family that is distinct from all mitochondrial and hydrogenosomal AACs studied so far. Thus, our data support the hypothesis that the various hydrogenosomes evolved repeatedly and independently. 相似文献
204.
PURPOSE OF REVIEW: We will discuss the diverse roles of lipoprotein receptors that contribute to the maintenance and integrity of the vascular wall. RECENT FINDINGS: Lipoprotein receptors function not only as transporters for cholesterol and other lipids. They also act as sensors and signal transducers through which the endothelium, macrophages and smooth muscle cells communicate with their environment. SUMMARY: Traditionally, lipoprotein receptors were thought of merely as transporters of cholesterol and triglycerides to specific target cells, either for the purpose of delivery and redistribution of nutrients, or for the destruction or clearance of modified (oxidized) lipids by macrophages. Only recently have we begun to appreciate that the same receptors engage in a much more sophisticated and multi-faceted interaction with their environment. Inasmuch, they not only act as mere transporters, but as surprisingly versatile and adaptive signal transducers and modulators throughout the vessel wall. These recent findings now begin to reshape our thinking of how such structurally different and evolutionarily unrelated lipoprotein receptors orchestrate the response of the vessel wall to mechanical or metabolic damage. 相似文献
205.
206.
Domain movements of elongation factor eEF2 and the eukaryotic 80S ribosome facilitate tRNA translocation 总被引:11,自引:0,他引:11 下载免费PDF全文
Spahn CM Gomez-Lorenzo MG Grassucci RA Jørgensen R Andersen GR Beckmann R Penczek PA Ballesta JP Frank J 《The EMBO journal》2004,23(5):1008-1019
An 11.7-A-resolution cryo-EM map of the yeast 80S.eEF2 complex in the presence of the antibiotic sordarin was interpreted in molecular terms, revealing large conformational changes within eEF2 and the 80S ribosome, including a rearrangement of the functionally important ribosomal intersubunit bridges. Sordarin positions domain III of eEF2 so that it can interact with the sarcin-ricin loop of 25S rRNA and protein rpS23 (S12p). This particular conformation explains the inhibitory action of sordarin and suggests that eEF2 is stalled on the 80S ribosome in a conformation that has similarities with the GTPase activation state. A ratchet-like subunit rearrangement (RSR) occurs in the 80S.eEF2.sordarin complex that, in contrast to Escherichia coli 70S ribosomes, is also present in vacant 80S ribosomes. A model is suggested, according to which the RSR is part of a mechanism for moving the tRNAs during the translocation reaction. 相似文献
207.
208.
Kröger L Henkensmeier D Schäfer A Thiem J 《Bioorganic & medicinal chemistry letters》2004,14(1):73-75
As potential lead structures for a new class of glycosidase inhibitors the novel O-glycosyl amino acid mimetics 3'-O-[2,6-anhydro-D-glycero-L-gluco-heptitol-1-yl]-L-serine 3 and-L-threonine 4 were synthesized, employing regio- and stereoselective aziridine ring opening methodology. They proved to be stable in the presence of glycosidases and showed competitive inhibition of alpha-galactosidase from Aspergillus niger. 相似文献
209.
Geyer J Döring B Failing K Petzinger E 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2004,137(3):317-329
We describe the cloning, functional characterization and tissue localization of a novel membrane transporter of the OATP/Oatp-gene family obtained from liver and kidney of cattle (Bos taurus). The carrier protein exhibits highest sequence identity to the human OATP1A2 (previously called OATP-A) and is, therefore, named bovine Oatp1a2. Bovine Oatp1a2 received the gene symbol Slco1a2 that is identical to the SLC classification of human OATP1A2 (SLCO1A2, previously called SLC21A3) and is likely an orthologue of the human gene. Two different full-length bOatp1a2 cDNAs of 2316-bp and 3504-bp were obtained and encoded for a 666 amino acid membrane protein, which contains twelve putative transmembrane spanning domains. Bovine Oatp1a2 expression was detected in liver, kidney, brain and adrenal gland. Uptake studies in cRNA-injected oocytes demonstrated that bOatp1a2 transports estrone-3-sulfate and taurocholate, with K(m) values of 9.6 microM and 51 microM, respectively, and estradiol-17beta-glucuronide. However, the structurally-related heart glycosides ouabain (1 microM) and digoxin (1 microM) are neither transported by bovine Oatp1a2 nor by human OATP1A2. We conclude that based on the tested substrates bovine Oatp1a2 shows functional homology to human OATP1A2. 相似文献
210.
This paper demonstrates that secondary structure information beyond purely protein secondary structure content can be predicted from FTIR (Fourier transform infrared spectroscopy) spectra of proteins with a high degree of accuracy. Both neural networks and adaptive neuro-fuzzy inference systems (ANFISs) were employed to predict helix/sheet segment information. The best results were achieved using ANFISs with fuzzy subtractive clustering based on normalised, compressed amide I data with an average SEP (standard error of prediction, root mean of squared errors) of 1.51. Predictions for average helix/sheet length based merely on the amide I band maximum position in combination with the full-width at half-height resulted in a comparable average SEP of 1.62. This suggests the importance of information on the position and width of the amide I band maximum for the prediction of helix/sheet segment information. Finally, the most promising pattern recognition approaches found in this study were applied to a protein with an as yet unknown x-ray structure: native a1-antichymotrypsin (a1-ACT). 相似文献