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31.
Deep-level diagnostic value of the rDNA-ITS region 总被引:14,自引:0,他引:14
The similarity of certain reported angiosperm rDNA internal transcribed
spacer (ITS) region sequences to those of green algae prompted our analysis
of the deep-level phylogenetic signal in the highly conserved but short
5.8S and hypervariable ITS2 sequences. We found that 5.8S sequences yield
phylogenetic trees similar to but less well supported than those generated
by a ca. 10-fold longer alignment from rDNA-18S sequences, as well as
independent evidence. We attribute this result to our finding that,
compared to 18S, the 5.8S has a higher proportion of sites subject to vary
and greater among-site substitution rate homogeneity. We also determined
that our phylogenetic results are not likely affected by intramolecular
compensatory mutation to maintain RNA secondary structure nor by evident
systematic biases in base composition. Despite historical homology, there
appears to be no ITS2 primary sequence similarity shared sufficient
similarity to cluster correctly on the basis of alignability. Our results
indicate that groups, however, share sufficient similarity to cluster
correctly on the basis of alignability. Our results indicate that ITS
region sequences can diagnose organismal origins and phylogenetic
relationships at many phylogenetic levels and provide a useful paradigm for
molecular evolutionary study.
相似文献
32.
Production of Serine Proteases by the Oyster Pathogen Perkinsus marinus (Apicomplexa) In Vitro 总被引:1,自引:1,他引:0
JEROME F. LA PEYRE DORIS Y. SCHAFHAUSER ESAM H. RIZKALLA MOHAMED FAISAL 《The Journal of eukaryotic microbiology》1995,42(5):544-551
ABSTRACT. Analysis of the cell-free supernatants of Perkinsus marinus cultures by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining revealed the presence of as many as 17 bands ranging in molecular weight from 239 to 32 kDa. These bands were not present in un-inoculated medium. Moreover, P. marinus produces extracellular proteins that possess proteolytic activities; the cell-free supernatants of P. marinus cultures could digest a variety of proteins including gelatin, casein, fibronectin and laminin. Oyster plasma was also digested by cell-free culture supernatants. The proteolytic activity in cell-free culture supernatants was detected 24 h post-inoculation, while no proteolytic activity could be detected in cell lysates. The proteolytic activities were characterized using substrate-impregnated sodium dodecylsulfate-polyacrylamide gels and had approximate molecular weights ranging from 55 to 35 kDa. The proteolytic activity of cell-free culture supernatants was inhibited by the serine protease inhibitors phenylmethylsulphonyl fluoride, 3,4-dichloroisocoumarin and soybean trypsin inhibitor. In contrast, inhibitors (i.e. trans-epoxysuccinyll-leucylamido(4-guanidino)-butane, 1, 10-phenanthroline, captopril, ethylenediaminetetracetic acid, pepstatin A or diazoacetyl-DL-norleucine methyl ester) from the other three classes of proteases had no effect. It was concluded that the P. marinus proteases in cell-free culture supernatants are serine proteases. 相似文献
33.
Insertional Mutation on Mouse Chromosome 18 with Vestibular and Craniofacial Abnormalities
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C. N. Ting D. Kohrman D. L. Burgess A. Boyle R. A. Altschuler G. Gholizadeh L. C. Samuelson W. Jang M. H. Meisler 《Genetics》1994,136(1):247-254
A dominant mutation was generated in transgenic mice as a consequence of insertional mutation. Heterozygous mice from transgenic line 9257 (Tg(9257)) are hyperactive with bidirectional circling behavior and have a distinctive facial appearance due to hypoplasia of the nasal bone. Morphological analysis of the inner ear revealed asymmetric abnormalities of the horizontal canal and flattening or invagination of the crista ampullaris, which can account for the circling behavior. The sensory epithelium appeared to be normal. The transgene insertion site was localized by in situ hybridization to the B1 band of mouse chromosome 18. Genetic mapping in an interspecific backcross demonstrated the gene order centromere--Tg(9257)--8.8 +/- 3.4--Grl-1, Egr-1, Fgf-1, Apc--14.7 +/- 4.3--Pdgfr. The phenotype and the mapping data suggest that the transgene may be inserted at the Twirler locus. Homozygosity for the transgene results in prenatal lethality, but compound heterozygotes carrying the Tw allele and the transgene are viable. The function of the closely linked ataxia locus is not disrupted by the transgene insertion. This insertional mutant will provide molecular access to genes located in the Twirler region of mouse chromosome 18. 相似文献
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Gopalakrishnan S Boyle D Takemoto L 《Transactions of the Kansas Academy of Science. Kansas Academy of Science》1993,96(1-2):7-12
The alpha crystallins are cytosolic proteins that co-localize and co-purify with actin-containing microfilaments. Affinity column chromatography employing both covalently-coupled actin or alpha crystallin was used to demonstrate specific and saturable binding of actin with alpha crystallin. This conclusion was confirmed by direct visualization of alpha aggregates bound to actin polymerized in vitro. The significance of this interaction in relation to the functional properties of these two polypeptides will be discussed. 相似文献
36.
D. C. Blakey B. E. Valcaccia S. East A. F. Wright F. T. Boyle C. J. Springer P. J. Burke R. G. Melton K. D. Bagshawe 《Cell biochemistry and biophysics》1993,22(1-3):1-8
The F(ab’)2 fragment of the antitumor monoclonal antibody, A5B7, was covalently linked to the bacterial enzyme carboxypeptidase G2 (CPG2). The resulting conjugate was used in combination with a prodrug of a benzoic acid mustard alkylating agent to treat human colon tumor xenografts in a two-step targeting strategy, antibody-directed enzyme produrug therapy (ADEPT). The prodrug, 4-[(2-chloroethyl) (2-mesyloxyethyl) amino]-benzoyl-l-glutamic acid is rapidly converted by CPG2 to a drug that is at least 15x more toxic in vitro against LS174T colorectal tumor cells than the prodrug. Optimal tumor/ blood ratios of the A5B7-CPG2 were achieved 72 h after administration of the conjugate to athymic mice bearing established LS174T tumor xenografts. Significant antitumor activity was seen in LS174T tumor-bearing mice treated with the conjugate followed 3 d later by the prodrug. In contrast, prodrug, conjugate, or active drug alone did not result in any antitumor activity in this tumor model. These studies demonstrate the advantage of a two-step ADEPT system for the treatment of colorectal cancer. 相似文献
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