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31.
Terrance O. Kurtz Drew J. Winston William J. Martin Lowell S. Young William L. Hewitt 《Current microbiology》1980,4(1):21-26
Moxalactam (LY127935), a novel beta-lactam antibiotic, was compared with semisynthetic penicillins, cephalosporins, and aminoglycosides
by the agar dilution method against 5,317 recent clinical isolates of facultative and anaerobic bactria. At 0.5 μg/ml, moxalactam
inhibited 90% of all Gram-negative bacilli tested except forPseudomonas aeruginosa (81% inhibited by 32 μg/ml) andAcinetobacter calcoaceticus (88% inhibited by 32 μg/ml). More than 90% ofBacteroides fragilis andStaphylococcus aureus were inhibited by 4 μg/ml and 8 μg/ml, respectively. Moxalactam was at least 16-fold more active by weight than cephalothin,
cefamandole, and cefoxitin forEscherichia coli, Klebsiella pneumoniae, andEnterobacter species, and 2- to 4-fold more active than cefoxitin forB. fragilis. Moxalactam was 4-fold less active than cefamandole and cephalothin forS. aureus and 2- to 4-fold less active than piperacillin forP. aeruginosa. Moxalactam was as active or more active than the aminoglycosides for all facultative Gram-negative bacilli except forP. aeruginosa. Moxalactam was inhibitory (minimal inhibitory concentration <16 μg/ml) for 20/27 gentamicin-resistant isolates and 8/13
amikacin-resistant organisms. Moxalactam’s in vitro activity against Gram-negative bacilli is markedly superior to presently
available cephalosporins and, except forP. aeruginosa, is comparable to the aminoglycosides. 相似文献
32.
G.J.L. Jones D. Hewitt G.J. Godin W.C. Breckenridge J. Bird M.A. Mishkel G. Steiner J.A. Little 《CMAJ》1980,122(1):37-46
The lipids and lipoproteins — cholesterol (C), triglyceride (TG) and high-density, low-density, very-low-density and sinking pre-β-lipoprotein cholesterol (HDL-C, LDL-C, VLDL-C and SPB-C) — in plasma samples from 1620 fasting white adults and children from the Toronto—Hamilton area were analysed. The mean concentration of HDL-C was about 45 mg/dl in men and about 60 mg/dl in women, and the levels were constant throughout adult life in both sexes. Boys had higher mean HDL-C levels than men, but girls had lower mean HDL-C levels than women. Mean LDL-C levels, like total C levels, increased with age, from about 87 mg/dl in boys to 136 mg/dl in men, and from about 91 mg/dl in girls to 145 mg/dl in women. The mean levels of VLDL-C followed the TG patterns for age and sex, rising from about 7 mg/dl in boys to 26 mg/dl in men, and from about 11 mg/dl in girls to 19 mg/dl in women. SPB-C was detectable visually in 39% of the population and with the aid of densitometry in 54%; the levels were not related to age, sex or oral contraceptive use, and the median level was 3 mg/dl.Prevalence estimates of hyperlipoproteinemia showed that type IV was the most common, and it was found more than three times as often in men as in women. This was in part due to the customary use of plasma TG cut-off points that do not reflect the large difference in TG levels between males and females. Type IIA hyperlipoproteinemia was found in about 2% of the adults and type IIb in a further 1%. Types I, III and V were all rare. The prevalence of types II and IV hyperlipoproteinemia was four times greater in women using oral contraceptives than in nonusers in the same age range. 相似文献
33.
Cultured neural crest cells which are freshly trypsinized require serum or purified fibronectin to attach to collagen substrates of types I–V. Furthermore, neural crest cells migrate in a Boyden chamber in response to fibronectin, and a “checkerboard” analysis demonstrates that fibronectin is both chemotactic and chemokinetic for these cells. It is proposed that collagen serves as a substrate for neural crest cells as they migrate in the early embryo. By mediating the cells' attachment to collagen, fibronectin may influence the movement of the cells. Local differences in fibronectin concentration or availability in the matrix could affect the degree of attachment of the cells to the collagen substrate and could also direct their migration by serving as a chemoattractant. 相似文献
34.
Organization of the Rosy Locus in DROSOPHILA MELANOGASTER: Further Evidence in Support of a CIS-Acting Control Element Adjacent to the Xanthine Dehydrogenase Structural Element 下载免费PDF全文
M. McCarron J. O''Donnell A. Chovnick B. S. Bhullar J. Hewitt E. P. M. Candido 《Genetics》1979,91(2):275-293
The present report summarizes our recent progress in the genetic dissection of an elementary genetic unit in a higher organism, the rosy locus (ry:3--52.0) in Drosophila melanogaster. Pursuing the hypothesis that the rosy locus includes a noncoding control region, as well as a structural element coding for the xanthine dehydrogenase (XDH) peptide, experiments are described that characterize and map a rosy locus variant associated with much lower than normal levels of XDH activity. Experiments are described that fail to relate this phenotype to alteration in the structure of the XDH peptide, but clearly associate this character with variation in number of molecules of XDH per fly. Large-scale fine-structure recombination experiments locate the genetic basis for this variation in the number of molecules of XDH per fly to a site immediately to the left of the XDH structural element within a region previously designated as the XDH control element. Moreover, experiments clearly separate this "underproducer" variant site from a previously described "overproducer" site within the control region. Examination of enzyme activity in electrophoretic gels of appropriate heterozygous genotypes demonstrates the cis-acting nature of this variation in the number of molecules of XDH. A revision of the map of the rosy locus, structural and control elements is presented in the light of the additional mapping data now available. 相似文献
35.
Growth and nitrate reductase activity were measured in Paul's Scarlet rose cell suspensions, cultured in media purified from molybdenum and containing nitrate or urea as sole nitrogen source with or without added Mo. Urea could replace nitrate to yield 80% of the fresh weight in nitrate medium. Nitrate reductase activities were compared by in vivo and in vitro assays. The latter varied due to inactivation during extraction. Compared with activities in cells in complete NO3
- medium, activity in NO3
--Mo cells was reduced to 30% and, in urea-grown cells, to trace amounts. Increases in nitrate reductase activity were found when NO3
- alone was added to NO3
- or urea+Mo cultures. In NO3
--Mo cultures, Mo alone or with NO3
- caused a similar increase in activity, whereas urea-Mo cultures required both NO3
- and Mo for enzyme induction.Abbreviations FAD
flavin adenine dinucleotide
- Mo
molybdenum
- NADH
reduced nicotinamide adenine dinucleotide
- NO3
-+Mo
standard MX1 culture medium
- NO3
--Mo
MX1 medium purified of Mo and used for continuous subculture with nitrate
- NR
nitrate reductase
- PSR
Paul's Scarlet rose
- PVP
polyvinylpyrrolidone
- U
urea
- U+Mo
MX1 medium containing urea instead of nitrate
- U-Mo
MX1 medium containing urea instead of nitrate and also purified of Mo 相似文献
36.
Significance of dimers to the size of newly synthesized DNA in UV-irradiated Chinese hamster ovary cells. 总被引:3,自引:0,他引:3 下载免费PDF全文
DNA synthesized after UV irradiation is smaller than that in unirradiated cells even when pulse-labeling times are increased to compensate for the overall reduction in the rate of DNA replication. By isolating newly replicated DNA, incubating it with dimer-specific endonuclease from Micrococcus luteus, and analyzing it on alkaline sucrose gradients, we have been able to demonstrate that this DNA is synthesized in segments corresponding in size to the interdimer distance on the parental strand. In addition, the same DNA analyzed on neutral gradients shows no reduction in molecular weight as a result of UV irradiation and/or endonuclease digestion. Our data are thus inconsistent with the presence of "gaps" in newly synthesized DNA opposite the dimers on the parental strand. We suggest that if such gaps are produced as a result of delayed synthesis around dimers, they are filled before the growing point reaches the next dimer. 相似文献
37.
Superoxide dismutase in some obligately anaerobic bacteria 总被引:21,自引:0,他引:21
38.
Judi E Hewitt Conrad A Pilditch 《Journal of experimental marine biology and ecology》2004,306(1):95-112
Epifaunal suspension-feeding bivalves can play important roles in marine ecosystems affecting macrobenthic communities, benthic boundary layers and benthic-pelagic coupling, not just by their presence but also by any changes in feeding behaviour. While seston quality and quantity have consistently been found to be important influences on the feeding rates of suspension-feeding bivalves, factors stressing individuals are also likely to be important, as they may affect energy-dependent thresholds of response. We postulated that (1) history of seston quantity would affect how suspension feeders deal with increases in total suspended particulates, and (2) high-seston concentrations would affect feeding rates more in individuals whose energy reserves were low after spawning. Three sites were selected for short-term (1 day) feeding experiments on the pinnid bivalve, Atrina zelandica. At one site, the experiment was run pre-and postspawning. Atrina exhibited high rejection of filtered particles (mostly 75% to 100%) and high organic absorption efficiencies (0.9-1) at all seston levels. Strong differences in the response of feeding behaviour to increased seston concentrations were observed between A. zelandica from the different sites, with lesser differences observed between times. The site-specific feeding responses to seston concentrations observed are likely to affect our ability to model responses of A. zelandica to sediment loading and to influence the importance of A. zelandica to benthic-pelagic coupling. 相似文献
39.
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