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41.
We describe genetic and molecular properties of Tc3, a family of transposable elements in Caenorhabditis elegans. About 15 Tc3 elements are present in the genomes of several different wild-type varieties of C. elegans, but Tc3 transposition and excision are not detected in these strains. Tc3 transposition and excision occur at high frequencies, however, in strain TR679, a mutant identified because of its highly active Tc1 elements. In TR679, Tc3 is responsible for several spontaneous mutations affecting the unc-22 gene. Tc3-induced mutations are unstable, and revertants result from precise or nearly precise excision of Tc3. Although Tc3 is very active in TR679, it is not detectably active in several other mutator mutants, all of which exhibit high levels of Tc1 activity. Tc3 is 2.5 kilobases long, and except for sequences near its inverted repeat termini, it is unrelated to Tc1. The termini of Tc3 are inverted repeats of at least 70 base pairs; the terminal 8 nucleotides of Tc3 are identical to 8 of the terminal 9 nucleotides of Tc1. 相似文献
42.
Choroideremia and deafness with stapes fixation: a contiguous gene deletion syndrome in Xq21. 总被引:13,自引:6,他引:7
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D E Merry J G Lesko D M Sosnoski R A Lewis M Lubinsky B Trask G van den Engh F S Collins R L Nussbaum 《American journal of human genetics》1989,45(4):530-540
The study of contiguous gene deletion syndromes by using reverse genetic techniques provides a powerful tool for precisely defining the map location of the genes involved. We have made use of individuals with overlapping deletions producing choroideremia as part of a complex phenotype, to define the boundaries on the X chromosome for this gene, as well as for X-linked mixed deafness with perilymphatic gusher (DFN3). Two patients with deletions and choroideremia are affected by an X-linked mixed conductive/sensorineural deafness; one patient, XL-62, was confirmed at surgery to have DFN3, while the other patient, XL-45, is suspected clinically to have the same disorder. A third choroideremia deletion patient, MBU, has normal hearing. Patient XL-62 has a cytogenetically detectable deletion that was measured to be 7.7% of the X chromosome by dual laser flow cytometry; the other patient, XL-45, has a cytogenetically undetectable deletion that measures only 3.3% of the X chromosome. We have produced a physical map of the X-chromosome region containing choroideremia and DFN3 by using routine Southern blotting, chromosome walking and jumping techniques, and long-range restriction mapping to generate and link anonymous DNA sequences in this region. DXS232 and DXS233 are located within 450 kb of each other on the same SfiI and MluI fragments and share partial SalI fragments of 750 and greater than 1,000 kb but are separated by at least one SalI site. In addition, DXS232, which lies outside the MBU deletion, detects the proximal breakpoint of this deletion. We have isolated two new anonymous DNA sequences by chromosome jumping from DXS233; one of these detects a new SfiI fragment distal to DXS233 in the direction of the choroideremia gene, while the other jump clone is proximal to DXS233 and detects a new polymorphism. These data refine the map around the loci for choroideremia and for mixed deafness with stapes fixation and will provide points from which to isolate candidate gene sequences for these disorders. 相似文献
43.
Differential depuration of poliovirus, Escherichia coli, and a coliphage by the common mussel, Mytilus edulis. 总被引:2,自引:2,他引:0
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The elimination of sewage effluent-associated poliovirus, Escherichia coli, and a 22-nm icosahedral coliphage by the common mussel, Mytilus edulis, was studied. Both laboratory-and commercial-scale recirculating, UV depuration systems were used in this study. In the laboratory system, the logarithms of the poliovirus, E. coli, and coliphage levels were reduced by 1.86, 2.9, and 2.16, respectively, within 52 h of depuration. The relative patterns and rates of elimination of the three organisms suggest that they are eliminated from mussels by different mechanisms during depuration under suitable conditions. Poliovirus was not included in experiments undertaken in the commercial-scale depuration system. The differences in the relative rates and patterns of elimination were maintained for E. coli and coliphage in this system, with the logarithm of the E. coli levels being reduced by 3.18 and the logarithm of the coliphage levels being reduced by 0.87. The results from both depuration systems suggest that E. coli is an inappropriate indicator of the efficiency of virus elimination during depuration. The coliphage used appears to be a more representative indicator. Depuration under stressful conditions appeared to have a negligible affect on poliovirus and coliphage elimination rates from mussels. However, the rate and pattern of E. coli elimination were dramatically affected by these conditions. Therefore, monitoring E. coli counts might prove useful in ensuring that mussels are functioning well during depuration. 相似文献
44.
Membrane attachment of recombinant G-protein alpha-subunits in excess of beta gamma subunits in a eukaryotic expression system 总被引:4,自引:0,他引:4
W F Simonds R M Collins A M Spiegel M R Brann 《Biochemical and biophysical research communications》1989,164(1):46-53
Recombinant cDNAs encoding the alpha-subunits of Gi1, Gi2, Gi3, Go and Gs were transfected into COS cells with the pCD-PS mammalian expression vector. Expression of each G alpha was verified using subtype-specific peptide antisera on immunoblots. Quantitative immunoblotting of alpha and beta subunits indicated: i) that there was no change in expression of endogenous beta subunits, and ii) overexpression of alpha subunits could achieve a ratio of alpha:beta greater than 25:1. Despite the excess of alpha over beta, the G alpha subunits were found predominantly in the membrane fraction. The results demonstrate that G alpha subunits can attach to the membrane independently of beta gamma subunits. 相似文献
45.
J Leszyk D Mornet E Audemard J H Collins 《Biochemical and biophysical research communications》1989,160(3):1371-1378
We have determined the amino acid sequence of a 35 kDa proteolytic fragment ("CaD35") derived from the C-terminus of turkey gizzard caldesmon. This 239-residue peptide contains binding sites for actin and calmodulin. Residues 1-96 of CaD35 comprise "CaD15", an actin-binding subfragment which we previously showed to resemble the tropomyosin-binding segment of troponin T. The remainder of the CaD35 sequence shows no significant similarity to other proteins. Residues 111-128 may form a basic, amphipathic helix which interacts with calmodulin. 相似文献
46.
Immunoliposomes with different acid sensitivities as probes for the cellular endocytic pathway 总被引:1,自引:0,他引:1
By combining dioleoylphosphatidylethanolamine (DOPE) with oleic acid (OA), palmitoylhomocysteine (PHC) or dipalmitoylsuccinylglycerol (DPSG) we have prepared pH-sensitive liposomes with different acid sensitivities. DOPE/OA liposomes are the most acid sensitive, while DOPE/DPSG liposomes are the least acid sensitive. Incubation of DOPE/OA liposomes with mouse L929 cells reduces the pH-sensitivity of these liposomes by altering the lipid composition. Using diphtheria toxin fragment A as a marker for cytoplasmic delivery, we find that the delivery kinetics of pH-sensitive immunoliposomes closely correlates with the modified acid sensitivities of the liposomes. Immunoliposomes encounter pH 6-6.2 with a t1/2 of 5-15 min after internalization. By contrast, acidification of the endosomes to pH 5.0 takes longer (t1/2 approximately 25 min). We also used a whole cell null point technique (Yamishiro and Maxfield (1987) J. Cell Biol. 105, 2713-2721) to directly determine the average pH encountered by the endocytosed immunoliposomes. We find that acidification determined by the null point method proceeds less rapidly than that estimated from DTA delivery data. This is likely due to the fact that the measured DTA delivery is done by those liposomes which first arrive at the endosomes with sufficient acidity. Our data suggests that DOPE/PHC immunoliposomes deliver at the early endosome while DOPE/DPSG immunoliposomes deliver at the late endosomes. The DOPE/OA immunoliposomes, with the altered composition and acid sensitivity, deliver with a kinetics intermediate between the other two immunoliposomes. Thus, pH-sensitive liposomes represent useful probes for studying the kinetics of endosome acidification. 相似文献
47.
48.
49.
Common expression of a tumor necrosis factor resistance mechanism among gynecological malignancies 总被引:2,自引:0,他引:2
C. Bethan Powell David G. Mutch L. Stewart Massad Ming-Shian Kao John Leslie Collins 《Cancer immunology, immunotherapy : CII》1990,32(2):131-136
Summary The efficacy of tumor necrosis factor (TNF) as an anticancer agent is limited. This limitation might be related to the expression of a protein-synthesis-dependent resistance mechanism that prevents the lysis of tumor cells by TNF. To test this possibility eight randomly selected human cell lines, three derived from ovarian carcinomas and five derived from cervical carcinomas, were tested for their in vitro sensitivity to TNF-mediated lysis. The results of this analysis showed that all eight cell lines are normally resistant to lysis by TNF. However, in the presence of inhibitors of protein synthesis, seven of them showed a significant increase in TNF-mediated lysis. Measurement of protein synthesis showed that there is a linear correlation between the level of inhibition of protein synthesis and the level of TNF-mediated lysis. The fact that seven of eight randomly selected cell lines are resistant to TNF because they express a protein-synthesis-dependent resistance mechanism suggests that this mechanism of resistance may be common among gynecological cancers. The results also suggest that a therapy involving TNF and inhibitors of protein synthesis might be useful for the treatment of gynecological malignancies. 相似文献
50.
A H Carey S Roach R Williamson J P Dumanski M Nordenskjold V P Collins G Rouleau N Blin P Jalbert P J Scambler 《Genomics》1990,7(3):299-306
DiGeorge syndrome is a human developmental field defect with the pathological features of an abnormality of embryogenesis at 4 to 6 weeks of gestation. Cytogenetic analyses of patients have revealed a number of instances of monosomy 22q11-pter in this condition. We have analyzed 52 DNA markers that map to 22q11-pter and have found 27 that are deleted in DiGeorge syndrome patients with known monosomy for part of this region and that are duplicated in patients with the der22 syndrome. The set of clones mapping to the DiGeorge region was further assigned to a proximal or a distal location within the deletion. 相似文献