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21.
Influence of Environmental Factors on Interstrain Competition in Rhizobium japonicum 总被引:11,自引:8,他引:3 下载免费PDF全文
The effect of several biotic and abiotic factors on the pattern of competition between two strains of Rhizobium japonicum was examined. In two Minnesota soils, Waseca and Waukegan, strain USDA 123 occupied 69% (Waseca) and 24% (Waukegan) of the root nodules on Glycine max L. Merrill cv. Chippewa. USDA 110 occupied 2% of the root nodules in the Waseca soil and 12% of the nodules in the Waukegan soil. Under a variety of other growth conditions—vermiculite, vermiculite amended with Waseca soil, and two Hawaiian soils devoid of naturalized Rhizobium japonicum strains—USDA 110 was more competitive than USDA 123. The addition of nitrate to or the presence of antibiotic-producing actinomycetes in the rhizosphere of soybeans did not affect the pattern of competition between the two strains. However, preexposure of young seedings to USDA 110 or USDA 123 before transplantation into soil altered the pattern of competition between the two strains significantly. In the Waseca soil, preexposure of cv. Chippewa to USDA 110 for 72 h increased the percentage of nodules occupied by USDA 110 from 2 to 55%. Similarly, in the Hawaiian soil Waimea, nodule occupancy by USDA 123 increased from 7 to 33% after a 72-h preexposure. 相似文献
22.
Ben J. G. Flik 《Aquatic Ecology》1985,19(2):117-122
Production versus light response curves were made of natural phytoplankton assemblages during the year in an incubator at 8 different light intensities ranging from 60 to 1500 Einstein.m–2.sec–1. The shape of these curves is analyzed in relation to the sensitivity for photo-inhibition. At the end of the month of April, there is a sudden shift in this sensitivity at higher light intensities. The algal assemblage becomes less sensitive for photo-inhibition. The influence of light-adaptation, temperature, nutrient limitation and species composition is discussed. 相似文献
23.
Intergeneric hybrids of Saccharomyces cerevisiae and Zygosaccharomyces fermentati obtained by protoplast fusion 总被引:1,自引:0,他引:1
To obtain strains that are able to efficiently produce ethanol from different carbohydrates, mainly cellulose hydrolysates, several species of the genus Candida and a Zygosaccharomyces fermentati strain were examined for their ability to utilize cellobiose and produce ethanol, as well as for their thermotolerance and the possibility of genetic manipulation. Candida obtusa and Zygosaccharomyces fermentati tolerated the maximal temperature for growth, possessed the highest cellobiase activity, and offered the possibility of genetic manipulation, although neither of them proved to be a good producer of ethanol. Intergeneric hybrids of Saccharomyces cerevisiae and Z. fermentati were obtained after protoplast fusion. They were selected as prototrophic strains, after isolation of auxotrophic mutants from Z. fermentati and fusion with an S. cerevisiae strain which was also auxotrophic. The hybrids, which appeared at a frequency of 2 X 10(-7), presented characteristics of both parents, such as resistance to certain drugs and the ability to grow with either cellobiose or lactic acid as the sole carbon source; they were very stable, even under nonselective conditions. These hybrids may have important industrial applications as good fermenting strains. 相似文献
24.
Ethanol-sensitive mutants of Saccharomyces cerevisiae 总被引:3,自引:0,他引:3
Saccharomyces cerevisiae mutants unable to grow at ethanol concentrations at which the wild type strain S288C does grow, have been isolated. Some of them show additional phenotypic alterations in colony size, temperature sensitivity and viability in ethanol, which cosegregate with the growth sensitivity in ethanol. 21 selected monogenic ethanol-sensitive mutants define 20 complementation groups, denominated ETA1 to ETA20, which indicates that there is a high number of genes involved in the ethanol tolerance/sensitivity mechanism.Out of 21 selected monogenic mutants, 20 are not altered in the glycolytic pathway since, when maintained in glucosesupplemented medium, they can produce as much ethanol as the wild type and at about the same velocity. Nor do any of the mutants seem to be altered in the lipid biosynthetic pathway since, whether grown in the absence or in the presence of ethanol, their concentration of fatty acids and ergosterol is similar to that of the wild type under the same conditions. Therefore growth sensitivity to ethanol does not seem necessarily to be related to carbohydrate or lipid metabolism.Non-common abbreviations YP
yeast extract peptone medium
- YPD
yeast extract peptone dextrose agar or medium
- YPG
yeast extract peptone glycerol agar
- YPDE
yeast extract peptone dextrose ethanol agar or medium
- SD
yeast nitrogen base dextrose agar
- SPO
yeast extract potassium acetate glucose agar
- PD
parental ditype
- NPD
non-parental ditype
- TT
tetratype 相似文献
25.
Competition of Rhizobium japonicum Strains in Early Stages of Soybean Nodulation 总被引:11,自引:8,他引:3 下载免费PDF全文
Renee M. Kosslak B. Ben Bohlool Stephen Dowdle Michael J. Sadowsky 《Applied microbiology》1983,46(4):870-873
The effects of preexposure of soybean (Glycine max L. Merrill) roots to Rhizobium japonicum strains and subsequent establishment of other strains in the nodules were investigated by using combinations of effective strains (USDA 110 and USDA 138) and effective-ineffective strains (USDA 110 and SM-5). Strain USDA 110 was a better competitor than either USDA 138 or SM-5 on cultivars Lee and Peking. However, when either of the two less-competitive strains was inoculated into 2-day-old seedlings before USDA 110 was, their nodule occupancy increased significantly on both cultivars. With USDA 138 as the primary inoculum and USDA 110 delayed for 6, 48, and 168 h, the incidence of USDA 138 nodules increased on cultivar Peking from 6% (at zero time) to 28, 70, and 82% and on cultivar Lee from 17% (at zero time) to 32, 88, and 95% for the three time delays, respectively. Preexposure of 2-week-old roots of cultivar Lee to USDA 138 had essentially the same effect: the incidence of USDA 138 nodules increased from 23% at zero time to 89 and 97% when USDA 110 was delayed for 24 and 72 h, respectively. When the ineffective strain SM-5 was used as the primary inoculum, followed by USDA 110 72 h later, the percentage of nodules containing SM-5 increased from 7 to 76%. These results indicate that the early events in the nodulation process of soybeans are perhaps the most critical for competition among R. japonicum strains. 相似文献
26.
Matthijs G.P. Feenstra Hans Rollema Theo B.A. Mulder Ben H.C. Westerink Alan S. Horn 《Life sciences》1983,32(12):1313-1323
Evidence is presented that a low dose of peripherally administered N, N-dipropylamino-5, 6-dihydroxytetralin (DiPr-5, 6-ADTN) specifically labels dopamine (DA) receptors in rat brain.Concentrations of this potent DA receptor agonist were determined by a highly selective method using reversed phase liquid chromatography and amperometric detection. The binding characteristics satisfy all criteria regarding saturability, stereospecificity, regional distribution and relation with pharmacological effects that are associated with DA receptor interactions. A rough estimation of the density of binding sites in the striatum resulted in values of 60–70 pmol/g. Lesioning the nigrostriatal pathway does not significantly alter the amount of ligand bound, nor do pretreatments with serotonergic, α-adrenergic or β-adrenergic antagonists. DiPr-5, 6-ADTN has thus been shown to be a useful ligand for labeling central DA receptors and a powerful tool in the study of DA-ergic mechanisms. 相似文献
27.
Toxicity to Chicks of Aspergillus and Penicillium Species Isolated from Moldy Pecans 总被引:3,自引:3,他引:0 下载免费PDF全文
Isolates of Aspergillus chevalieri, A. flavus, A. ochraceus, A. repens, and Penicillium funiculosum and complexes of P. citrinum-P. implicatum isolated from moldy pecan meats were toxic to chicks. 相似文献
28.
R. B. Singh Ben W. Smith 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1971,41(8):360-364
Summary Cytogenetic studies were made with particular emphasis on the sex-determining mechanism in Rumex acetosella (6 x = 42) and its hybrids (F
1, F
2, BC
1 and BC
2) with R. hastatulus (synthetic 4 x = 16 = 4 A +4 X = and 4 x = 18 = 4 A + 2 (X Y
1
Y
2) = ). Rumex acetosella was almost strictly dioecious with 5050 male and female. Breeding tests revealed that the males were heterogametic. The longest chromosomes (S), usually two, are the sex chromosomes of this hexaploid species. The S chromosomes are homomorphic in both male and female. The sex chromosome: autosome ratios, and the strong epistatic male effect of the S
M chromosome in the polyploid dioecious species and in the hybrids, are evidence of an X/Y Melandrium type sex-determining mechanism controlled by a single pair of homomorphic sex chromosomes. Thus, the sex chromosome formula of the males was S
F
S
M and that of females was S
F
S
F. The present approach is a new method for resolving the sex-determining mechanism in a dioecious species. 相似文献
29.
30.