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91.
92.
Reshaping of sandstone surfaces by cryptoendolithic cyanobacteria: bioalkalization causes chemical weathering in arid landscapes 总被引:1,自引:0,他引:1
We report a novel weathering mechanism in South African sandstone formations, where cryptoendolithic cyanobacteria induce weathering by substrate alkalization during photosynthesis. As a result, the upper rock part is loosened and then eroded away by physical forces such as wind, water, trampling. This special type of ‘exfoliation’ is widely distributed and affects the geomorphology of whole sandstone mountain ranges and outcrops across several biomes. We show, that this weathering type is initiated by bioalkalization because of the photosynthesis of cryptoendolithic (i.e. those organisms living in small tight open spaces between the sand grains) cyanobacteria causing pH values high enough to enhance silica solution in the cryptoendolithic zone. As modern cyanobacteria are the initial photoautotrophic colonizers of bare rocks in arid and semiarid landscapes, it is possible that they may also have played a significant role in shaping sandstone landscapes in the geological past. 相似文献
93.
The predatory copepod Mesocyclops edax is an important componentof many zooplankton communities where it typically makes extensivedid vertical migrations. To describe the effect of light onadults we measured their photoresponses in the laboratory. Theresponse spectrum is characterized by a wide plateau of greatestsensitivity from about 480 580 nm. These animals areadapted to perceive light during the day since their regionof maximum sensitivity overlaps the spectral region of highestquantal intensity underwater (575 700 nm). The thresholdintensity for positive phototaxis by dark adapted animals wasabout 5 x 101 Wm2 at 540 nm, and they were positivelyphototactic up to an intensity of 5 x 101 Wm2.Above this intensity phototaxis is no longer observed. Light-adaptedanimals were less sensitive than dark-adapted, but their generalpattern of response to light intensity did not differ. Thereis no rhythm in phototaxis. Their photoresponses may providea mechanism for controlling vertical migration so as to minimizeexposure to planktivorous fish.
1Contribution No. 1375-AEL from UM-CEES, Appalachian EnvironmentalLaboratory. 相似文献
94.
The aqueous solution equilibria and solute structure of vitamin B6 compounds and several model compounds have been investigated using 13C-nmr spectroscopy. The unsubstituted α-carbon of these compounds is a very good probe for data which permits assignment of the ionization steps to indicidual groups. While the ionizations of the pyridinium and phenolic groups take place simultaneously in 3-hydroxypyridine, they take place in well-separated steps in pyridoxamine (PM), pyridoxamine phosphate (PMP), and pyridoxal phosphate. It has been established that the ionization with a pKa value of 3.7 is predominantly phenolic in origin in PM and PMP. A zwitterionic structure consistent with the earlier spectroscopic investigations is proposed for the vitamin B6 compounds in neutral aqueous solution. 相似文献
95.
Swift Candice L. Brown Jennifer L. Seppälä Susanna O’Malley Michelle A. 《Journal of industrial microbiology & biotechnology》2019,46(9-10):1427-1433
Journal of Industrial Microbiology & Biotechnology - Anaerobic gut fungi are biomass degraders that form syntrophic associations with other microbes in their native rumen environment. Here,... 相似文献
96.
97.
Benjamin M.C. Swift Emily J. Denton Sophie A. Mahendran Jonathan N. Huxley Catherine E.D. Rees 《Journal of microbiological methods》2013
The aim of this study was to develop a methodology to rapidly detect viable Mycobacterium avium subsp. paratuberculosis (MAP) in clinical blood samples. MAP cells spiked into commercially available blood were recovered using optimised peptide-mediated magnetic separation (PMMS) and detected using a phage-based method, and the identity of the cells detected confirmed using nested-PCR amplification of MAP signature sequences (IS900). The limit of detection was determined to be 10 MAP cells per ml of blood and was used to detect MAP present in clinical bovine blood samples. Using the PMMS-phage method there was no difference when detecting MAP from whole blood or from isolated buffy coat. MAP was detected in animals that were milk-ELISA positive (15 animals) by PMMS-phage and no MAP was detected in blood samples from an accredited Johne's disease free herd (5 animals). In a set of samples from one herd (10 animals) that came from animals with variable milk ELISA status, the PMMS-phage results agreed with the positive milk-ELISA results in all but one case. These results show that the PMMS-phage method can detect MAP present in naturally infected blood. Total assay time is 48 h and, unlike PCR-based detection tests, only viable cells are detected. A rapid method for detecting MAP in blood could further the understanding of disseminated infection in animals with Johne's disease. 相似文献
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99.
Zfy1 is a mouse Y chromosomal gene encoding a zincfinger protein which is thought to have some function during spermatogenesis. Here we show that, when introduced into tissue culture cells, Zfy1 is targeted to the nucleus. Two independent signals are present within the protein for nuclear localization. This nuclear Zfy1 protein is able to bind strongly to DNA-cellulose and, using site-selection assays, we have identified specific Zfy1 DNA binding sites. Taken together these results suggest that Zfy1 is a nuclear-located sequence-specific DNA binding protein which functions during spermatogenesis. 相似文献
100.
Dent A. Earl Kristina D. Louie Carolyne Bardeleben Camm C. Swift David K. Jacobs 《Conservation Genetics》2010,11(1):103-114
The federally endangered tidewater goby, Eucyclogobius newberryi, is the most locally differentiated vertebrate with marine dispersal on the California Coast. It inhabits seasonally closed
estuaries along the California coast; a habitat heavily impacted by anthropogenic filling and artificial opening, and exhibits
varied metapopulation behavior as a consequence of hydrologic variation and anthropogenic impact. We describe 19 taxon-specific
microsatellite loci, and assess genetic variation across the taxon range relative to genetic subdivision. A highly divergent
southern clade, with reduced genetic variation, now confined to Northern San Diego County, appears to merit status as a separate
species. The mid-coast is subdivided into regional groups with overall similarity to, and minor differences from previous
mitochondrial sequence based clades. The northernmost region, although locally differentiated, forms a star phylogeny with
limited geographic structure which we attribute to dispersal during Pleistocene/Holocene sea-level rise followed by increasing
isolation during the Holocene. Bottleneck/founder events are evident in some habitats thought to have experienced (anthropogenic)
extirpation. Further work with more, and larger, samples will be required to assess local and regional differences. Analytical
methods employed include Analysis of Molecular Variance (AMOVA), Neighbor-Joining, Bayesian/STRUCTURE analysis and Principle
Components Analysis (PCA). 相似文献