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Svetlana A. Semerikova Vladimir L. Semerikov Martin Lascoux 《Journal of Biogeography》2011,38(2):326-340
Aim The main aim of the present study is to infer the post‐glacial history of Abies species from north‐east Asia and to test the hypotheses that coastal Abies populations suffered less from climatic fluctuations during Pleistocene glacial periods than their more continental counterparts, and that Sakhalin was a major area of introgression. Location Natural ranges of the fir species Abies nephrolepis, Abies sachalinensis and Abies holophylla in the Russian Far East, and of Abies gracilis, which is endemic to the Kamchatka Peninsula. Methods Nineteen populations were sampled for allozyme analysis. Seventeen of these populations were also screened for variation at two paternally inherited chloroplast DNA microsatellite loci (cpSSR) and variation at one maternally inherited mitochondrial marker (nad4‐3/4). Finally a subset of 11 populations was analysed with amplified fragment length polymorphism (AFLP). Comparisons were made with already available Abies sibirica data. For all sets of markers, we estimated genetic diversity and differentiation using an analysis of molecular variance (AMOVA). Population clustering was assessed with a Bayesian approach implemented in structure v.2.3. Results Among the three major species, A. sibirica, A. nephrolepis and A. sachalinensis, A. sachalinensis demonstrated the highest cytoplasmic and nuclear diversity and the most continental species, A. sibirica, the lowest. Both nuclear and mitochondrial DNA markers revealed the presence of a transitional zone on Sakhalin Island between A. nephrolepis and A. sachalinensis of south Sakhalin. The structure analysis delivered very clear results confirming the admixed origin of A. sachalinensis, with a genetic contribution from A. nephrolepis. No variation in cytoplasmic markers was found in A. gracilis, suggesting the occurrence of a recent bottleneck. Main conclusions There is a clear reduction of genetic diversity in Abies species from the Pacific coast into the continent. The higher diversity in A. sachalinensis could have two causes: a larger effective population size in the islands due to relatively stable climatic conditions and consequently less pronounced demographic fluctuations in population size and/or hybridization with continental and Japanese populations. Sakhalin Island is a major transitional zone for conifer species. Finally, the fir from Kamchatka, A. gracilis, should be regarded as a separate species closely related to the A. nephrolepis–A. sachalinensis complex. 相似文献
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Vera G. Doroshenko Rustem S. Shakulov Svetlana M. Kazakova Alexander D. Kivero Tatyana A. Yampolskaya Sergey V. Mashko 《Biotechnology letters》2010,32(8):1117-1121
To construct a Phe-producing Tyr+ Escherichia coli strain, TyrA (chorismate mutase/prephenate dehydrogenase) activity was varied by engineering a proteolytically unstable protein. The tyrA in the E. coli BW25113 was altered to include ssrA-like tags. The tagged tyrA genes, which ensured different growth rates in M9 medium, were introduced into a Phe-producing strain to replace ΔtyrA. Strains with unstable TyrA-(A)ANDENYALAA proteins had a lower biomass yield and a higher Phe accumulation than strains generating the more stable TyrA-(A)ANDENYALDD. The Tyr/Phe ratio produced by the TyrA-tag strains was 10-fold less than that produced by the TyrAwt strain. 相似文献
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Svetlana Trivić Vladimir Leskovac 《Biochemical and biophysical research communications》1976,71(4):1161-1166
Liver glutamate dehydrogenase forms a complex with ethidium bromide in solution; binding parameters of this complex depend on pH and enzyme concentration, but are independent of the ionic strength of solution. Binding of ethidium bromide occurs outside the coenzyme binding site, but appears to be closely related to the oligomer association sites of the enzyme. 相似文献
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Tammy May Svetlana A. Kocherginskaya Roderick I. Mackie Philip E. Vercoe bryan A. White 《FEMS microbiology letters》1996,144(2-3):221-227
Abstract The complete nucleotide sequence of a cryptic plasmid designated pBAW301, from the Gram-positive ruminai bacterium Ruminococcus flavefaciens R13e2, has been determined. This plasmid is 1768 bp in size and has an overall G+C content of 43.5%. Computer analysis of the sequence data revealed an open reading frame, ORF1 (256 amino acids), which is similar to the Rep protein of the Bacillus borstelensis plasmid pHT926. ORF1 is preceded by Shine-Dalgarno and Escherichia coli —10 and —35 like sequences. Nine smaller open reading frames showed no significant homologies to known protein sequences. Analysis of replication intermediates and the nucleotide sequence indicate that the plasmid does not replicate by a rolling-circle mode of replication similar to other plasmids from Gram-positive bacteria. Moreover, sequences typical of theta replication origins were not found in the nucleotide sequence of pBAW301. These data suggest that this plasmid either replicates by an as yet undescribed mechanism, or represents a new class of theta replicating plasmids. 相似文献
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Alex Eyraud Pierre Tattevin Svetlana Chabelskaya Brice Felden 《Nucleic acids research》2014,42(8):4892-4905
The emergence of Staphylococcus aureus strains that are resistant to glycopeptides has led to alarming scenarios where serious staphylococcal infections cannot be treated. The bacterium expresses many small regulatory RNAs (sRNAs) that have unknown biological functions for the most part. Here we show that an S. aureus sRNA, SprX (alias RsaOR), shapes bacterial resistance to glycopeptides, the invaluable treatments for Methicillin-resistant staphylococcal infections. Modifying SprX expression levels influences Vancomycin and Teicoplanin glycopeptide resistance. Comparative proteomic studies have identified that SprX specifically downregulates stage V sporulation protein G, SpoVG. SpoVG is produced from the yabJ-spoVG operon and contributes to S. aureus glycopeptide resistance. SprX negatively regulates SpoVG expression by direct antisense pairings at the internal translation initiation signals of the second operon gene, without modifying bicistronic mRNA expression levels or affecting YabJ translation. The SprX and yabJ-spoVG mRNA domains involved in the interaction have been identified, highlighting the importance of a CU-rich loop of SprX in the control of SpoVG expression. We have shown that SpoVG might not be the unique SprX target involved in the glycopeptide resistance and demonstrated that the regulation of glycopeptide sensitivity involves the CU-rich domain of SprX. Here we report the case of a sRNA influencing antibiotic resistance of a major human pathogen. 相似文献