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11.
Release of Inorganic Phosphate from Irradiated Yeast: Radiation Biodosimetry and Evaluation of Radioprotective Compounds 下载免费PDF全文
When cells of bakers' yeast, Saccharomyces cerevisiae, were irradiated with ionizing radiation, inorganic phosphate, ninhydrin-reactive material, and substances absorbing at 260 mmu were released into the suspending medium. The amount of inorganic phosphate released depended on the radiation dose and on the temperature and pH during irradiation. The concentration of yeast cells did not affect the phosphate yield per milligram of yeast. It is suggested that the release of phosphate may serve as an index of the total radiation environment (i.e., as a biodosimeter) where radiation inactivation of microrganisms is of primary importance, e.g., in radiation preservation of foods. The somewhat limited range of the yeast biodosimeter (ca. 0.5 to 1.75 Mrad) may be extended by use of other more resistant microorganisms, such as bacterial spores. Compounds which have been reported as protecting microorganisms and mammals against the lethal effect of ionizing radiation also inhibited the radiation-induced release of inorganic phosphate from yeast. This phosphate release system is proposed as the basis for an economical, rapid supplement to screening procedures in the evaluation of radioprotective compounds. 相似文献
12.
Nine color and 35 auxotrophic mutants were tested for their virulence, using the ‘Jonathan’ variety of apple; only mutants requiring methionine were avirulent. One tested arginine-requiring and the methionine-requiring mutants were avirulent for the ‘Red Delicious’ variety. In vitro and in vivo, supplementation studies indicated that the avirulence was probably related to the relatively low concentration of the required amino acids at the site of inoculation. One heterocaryon and the corresponding diploid, involving 2 avirulent methionine-requiring mutants, were virulent. Six mutant loci in 3 diploid strains could be assigned to 2 linkage groups by means of the parasexual cycle. 相似文献
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14.
Crystals of threonyl-tRNA synthetase from Thermus thermophilus. Preliminary crystallographic data 总被引:1,自引:0,他引:1
M B Garber A D Yaremchuk M A Tukalo S P Egorova N P Fomenkova S V Nikonov 《Journal of molecular biology》1990,214(4):819-820
Crystals have been obtained of threonyl-tRNA synthetase from the extreme thermophile Thermus thermophilus using sodium formate as a precipitant. The crystals are very stable and diffract to at least 2.4 A. The crystals belong to space group P2(1)2(1)2(1) with cell parameters a = 61.4 A, b = 156.1 A, c = 177.3 A. 相似文献
15.
M B Garber A D Yaremchuk M A Tukalo S P Egorova C Berthet-Colominas R Leberman 《Journal of molecular biology》1990,213(4):631-632
Crystals have been obtained of seryl-tRNA synthetase from the extreme thermophile Thermus thermophilus, using mixed solutions of ammonium sulphate and methane pentane diol. The crystals are very stable and diffract to at least 2 A. The crystals are monoclinic (space group P21) with cell parameters a = 87.1 A, b = 126.9 A, c = 63.5 A and beta = 109.7 degrees. 相似文献
16.
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18.
Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
19.
Three-dimensional structure of the ribosomal translocase: elongation factor G from Thermus thermophilus. 总被引:15,自引:2,他引:13 下载免费PDF全文
A AEvarsson E Brazhnikov M Garber J Zheltonosova Y Chirgadze S al-Karadaghi L A Svensson A Liljas 《The EMBO journal》1994,13(16):3669-3677
The crystal structure of Thermus thermophilus elongation factor G without guanine nucleotide was determined to 2.85 A. This GTPase has five domains with overall dimensions of 50 x 60 x 118 A. The GTP binding domain has a core common to other GTPases with a unique subdomain which probably functions as an intrinsic nucleotide exchange factor. Domains I and II are homologous to elongation factor Tu and their arrangement, both with and without GDP, is more similar to elongation factor Tu in complex with a GTP analogue than with GDP. Domains III and V show structural similarities to ribosomal proteins. Domain IV protrudes from the main body of the protein and has an extraordinary topology with a left-handed cross-over connection between two parallel beta-strands. 相似文献
20.
Crystal structure of a prokaryotic aspartyl tRNA-synthetase. 总被引:3,自引:3,他引:0
M Delarue A Poterszman S Nikonov M Garber D Moras J C Thierry 《The EMBO journal》1994,13(14):3219-3229
The crystal structure of Thermus thermophilus aspartyl tRNA-synthetase (AspRS) refined at 2.5 A resolution is described. This molecular structure is a textbook illustration of the modular organization of aminoacyl-tRNA synthetases. In addition to the three domains found in yeast AspRS, each monomer exhibits a module specific to prokaryotic enzymes, which corresponds to a helix-turn-helix motif in yeast AspRS, a domain implicated in the stabilization of the complex with tRNA. Its topology matches that of the histidine-containing phosphocarrier HPr which has been linked recently to another group of proteins containing the ferredoxin fold. We propose a more extensive alignment of these folds, which involves a circular permutation of the sequences and changes the point of entry of the whole domain. The C-terminal extension, another prokaryotic characteristic, leads to a significant increase in the network of interaction at the dimer interface. Some potential communication pathways suggest how a transfer of information between the two active sites of the homodimer might occur. Most of the residues involved belong to the class II-specific motifs in correlation with the dimeric state of nearly all class II enzymes. The T. thermophilus enzyme exhibits some features not found in any of the six other known AspRSs from mesophilic organisms. 相似文献