全文获取类型
收费全文 | 5595篇 |
免费 | 516篇 |
国内免费 | 1篇 |
出版年
2023年 | 24篇 |
2022年 | 65篇 |
2021年 | 134篇 |
2020年 | 83篇 |
2019年 | 113篇 |
2018年 | 119篇 |
2017年 | 104篇 |
2016年 | 174篇 |
2015年 | 316篇 |
2014年 | 326篇 |
2013年 | 406篇 |
2012年 | 492篇 |
2011年 | 479篇 |
2010年 | 281篇 |
2009年 | 251篇 |
2008年 | 357篇 |
2007年 | 329篇 |
2006年 | 298篇 |
2005年 | 329篇 |
2004年 | 303篇 |
2003年 | 255篇 |
2002年 | 219篇 |
2001年 | 50篇 |
2000年 | 36篇 |
1999年 | 48篇 |
1998年 | 50篇 |
1997年 | 35篇 |
1996年 | 36篇 |
1995年 | 22篇 |
1994年 | 38篇 |
1993年 | 22篇 |
1992年 | 29篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 23篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 25篇 |
1976年 | 12篇 |
1972年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有6112条查询结果,搜索用时 15 毫秒
21.
Chromosome distribution of intracisternal A-particle sequences in the Syrian hamster and mouse 总被引:5,自引:0,他引:5
Edward L. Kuff Joseph E. Fewell Kira K. Lueders Joseph A. DiPaolo Suzanne C. Amsbaugh Nicholas C. Popescu 《Chromosoma》1986,93(3):213-219
Metaphase chromosomes of Syrian hamster and BALB/c mice were hybridized in situ with radiolabeled probes derived from cloned intracisternal A-particle (IAP) genes of the corresponding species. The DNAs of these species are known to contain about 900 and 1,000 copies, respectively, of the retrovirus-like IAP sequence elements per haploid genome. Multiple IAP sequences were found on all chromosomes of both hamster and mouse. In the hamster, more than half of the IAP sequences were located in regions of non-centromeric constitutive heterochromatin, at an average concentration per unit chromosome length 5 times greater than in the euchromatic regions. The other dispersed sequences showed marked local variations in concentration along the chromosome lengths; both discrete foci and large grain clusters were observed as well as regions apparently lacking IAP sequences. Within the resolution of the techniques, IAP sequences appeared to be more evenly distributed over the mouse chromosomes; however, some prominent variations in concentration were seen. The number of potentially active IAP genes in the Syrian hamster, and by extension in the mouse, may be restricted by the preferential location of IAP sequences in genetically inert regions of the genome. 相似文献
22.
Affinity of corticosteroids for mineralocorticoid and glucocorticoid receptors of the rabbit kidney: effect of steroid substitution 总被引:1,自引:0,他引:1
M E Rafestin-Oblin M Lombes P Lustenberger P Blanchardie A Michaud G Cornu M Claire 《Journal of steroid biochemistry》1986,25(4):527-534
Corticosteroid derivatives coupled in the C3, C7 or C17 position with a long aliphatic chain were synthesized in order to select a suitable ligand for the preparation of a biospecific affinity adsorbent for mineralocorticoid receptor purification. The affinity of these derivatives for mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) was explored in rabbit kidney cytosol. In this model, aldosterone bound to a single class of receptors with high affinity (Kd 1 nM) and mineralocorticoid specificity. RU26988, a highly specific ligand for GR, did not compete for these sites. The C7 and C17 positions were found to be of crucial importance in the steroid's interaction with the mineralocorticoid receptors, since the linkage of a long side chain in these positions induced complete loss of affinity. Hence, deoxycorticosterone no longer bound to MR after 17 beta substitution with a 9-carbon aliphatic chain. This loss of affinity was not observed for glucocorticoids. The 17 beta nonylamide derivative of dexamethasone still competed for GR. Increasing the length of the C7 side of the spirolactone SC26304 suppressed its affinity for MR. Finally, C3 was an appropriate position for steroid substitution. The 3-nonylamide of carboxymethyloxime deoxycorticosterone bound to MR but not to GR, and therefore constitutes a suitable ligand for the preparation of a mineralocorticoid adsorbent. 相似文献
23.
D. Christine Sigurdson Robert K. Herman Cynthia A. Horton Claire K. Kari Steven E. Pratt 《Molecular & general genetics : MGG》1986,202(2):212-218
Summary The translocation mnT12(IV;X) is a fusion of holocentric chromosomes IV and X, the breakpoints occurring near the left end of IV and the right end of X. Animals homozygous for mnT12 are viable and fertile; they contain five pairs of chromosomes rather than the normal set of six pairs. The mnT12 chromosome is larger than all wild-type chromosomes and thus identifies linkage groups IV and X cytologically. Hermaphrodites heterozygous for mnT12 show high frequency meiotic nondisjunction both between mnT12 and the X chromosome, which results in a high incidence of male self progeny (27% compared to the wild-type incidence of 0.2%), and between mnT12 and chromosome IV, which results in a high incidence of self progeny essentially trisomic for chromosome IV (karyotype IV/mnT12/mnT12). The viability of chromosome IV trisomics has been confirmed by constructing animals trisomic for only normal copies of chromosome IV; these animals are morphologically wild type. Meiotic chromosome disjunction in mnT12 homozygotes appears to be normal, although the frequency of recombination between markers that are normally X-linked is significantly reduced. Males of genotype IV/mnT12/0 are fertile. They can be thought of as having a neo-X(mnT12) neo-Y(normal IV) karyotype since it is possible to maintain a male-hermaphrodite stock of C. elegans consisting of such males and hermaphrodites carrying two neo-X chromosomes and no neo-Y; the organism is thus converted from an XO:XX type of sex determination to an XX:XX system. 相似文献
24.
T. H. Noel Ellis Claire Domoney Judy Castleton Wendy Cleary D. Roy Davies 《Molecular & general genetics : MGG》1986,205(1):164-169
Summary We describe four genomic clones of pea 7S storage protein gene, one of which corresponds to convicilin, and the others to
vicilin. Hybridization studies exploiting these clones, and previously identified cDNA clones, have enabled us to define six
different loci. Three of these loci have been mapped to positions on chromosome 7. 相似文献
25.
Claire Graham 《BMJ (Clinical research ed.)》1985,291(6511):1790-1791
26.
27.
In order to study their natural killer effect, guinea pig splenic Kurloff cells were fractionated by Percoll discontinuous density gradient centrifugation. Kurloff cells were collected and tested for cytotoxicity in a 24-hr chromium-release test. Comparison of different splenic cellular samples (of males or estrogenized females) with increasing percentage of Kurloff cells, revealed a highly significant positive correlation (r = 0.93, α < 0.01) with the cellular cytotoxicity developed against the K 562 target cells. 相似文献
28.
Genetic analysis and molecular cloning of the Escherichia coli ruv gene 总被引:22,自引:0,他引:22
Claire E. Shurvinton Robert G. Lloyd Fiona E. Benson Paul V. Attfield 《Molecular & general genetics : MGG》1984,194(1-2):322-329
Summary The genetic organisation of the ruv gene, a component of the SOS system for DNA repair and recombination in Escherichia coli, was investigated. New point mutations as well as insertions and deletions were generated using transposon Tn10 inserted in eda as a linked marker for site specific mutagenesis, or directly as a mutagen. The mutations were ordered with respect to one another and previously isolated ruv alleles by means of transductional crosses. The direction of chromosome mobilization from ruv:: Mud(ApR
lac)strains carrying F42lac
+ established that ruv is transcribed in a counterclockwise direction. Recombinant phages able to restore UV resistance to ruv mutants were identified, and the ruv
+ region was subcloned into a low copy number plasmid. The ruv
+ plasmid was able to correct the extreme radiation sensitivity and recombination deficiency of ruv recBC sbcB strains. 相似文献
29.
Changes in ascorbic acid content and ascorbate peroxidase activity during the development of Acetabularia mediterranea 总被引:4,自引:0,他引:4
Federico J. Castillo Geneviève Cotton Claire Kevers Hubert Greppin Thomas Caspar Thérèse Vanden Driessche 《Differentiation; research in biological diversity》1986,33(1):17-23
We cloned ras-related sequences from goldfish genomic libraries constructed as recombinants using the lambda phage. Restriction enzyme mapping of the clones obtained revealed three kinds of ras-related sequences among approximately 350,000 genomic clones. One of these clones was partially sequenced. Comparison with the nucleotide sequences of mammalian ras genes showed that the determined sequences covered the predicted amino acid coding regions and parts of the intervening regions. The predicted amino acid sequences of the cloned ras-related goldfish gene suggested that the coding region is localized separately in DNA, and that its exon-intron boundaries are exactly the same as those of corresponding mammalian genes. The nucleotide and amino acid sequences of the goldfish ras-related gene may have extensive homologies to mammalian p 21 protein. Among the three mammalian ras proteins, the predicted amino acid sequence of the sequenced ras-related goldfish clone is most closely homologous (96%) to the Kirsten ras protein. Differences in the predicted amino acid sequence were greatest in the sequence predicted from the fourth exon; fewer differences were found in the sequence from the third exon, and only slight or no differences were found in the sequence predicted for the first and second exons. The 12th and 61st amino acids from the N-terminal of the protein, which are thought to be critical positions for GTP binding and catalysis, are both conserved in the goldfish protein.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
30.
Differential Recovery of Auxotrophs After Penicillin Enrichment in Escherichia coli 总被引:6,自引:3,他引:3
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Various auxotrophs are recovered from a penicillin enrichment cycle with differing efficiencies. Reconstruction experiments indicate that, under starvation conditions in the presence of penicillin, most auxotrophs undergo some death, whereas prolineless mutants are virtually immune to penicillin-induced killing. 相似文献