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排序方式: 共有830条查询结果,搜索用时 15 毫秒
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Alternating currents can increase or decrease the ATP-splitting activity of the membrane enzyme Na,K-ATPase. Either change depends on the AC frequency, and the greatest effect appears to be in the ELF range at about 100 Hz. The threshold for enzyme inhibition by AC was determined, and it is estimated to be an internal electric field circa 5 microV/cm. The corresponding current-density threshold approximates 8 nA/cm2. 相似文献
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Patrick Bongartz Tobias Karmainski Moritz Meyer John Linkhorst Till Tiso Lars M. Blank Matthias Wessling 《Biotechnology and bioengineering》2023,120(5):1269-1287
Bioreactors are the operative backbone, for example, for the production of biopharmaceuticals, biomaterials in tissue engineering, and sustainable substitutes for chemicals. Still, the Achilles' heel of bioreactors nowadays is the aeration which is based on intense stirring and gas sparging, yielding inherent drawbacks such as shear stress, foaming, and sterility concerns. We present the synergistic combination of simulations and experiments toward a membrane stirrer for the efficient bubble-free aeration of bioreactors. A digital twin of the bioreactor with an integrated membrane-module stirrer (MemStir) was developed with computational fluid dynamics (CFD) studies addressing the determination of fluid mixing, shear rates, and local oxygen concentration. Usability of the MemStir is shown in a foam-free recombinant production process of biosurfactants (rhamnolipids) from glucose with different strains of Pseudomonas putida KT2440 in a 3-L vessel and benchmarked against a regular aerated process. The MemStir delivered a maximal oxygen transfer rate (OTRmax) of 175 mmol L−1 h−1 in completely foam-free cultivations. With a high space-time yield (STY) of 118 mgRL L−1 h−1 during a fed-batch fermentation, the effectiveness of the novel MemStir is demonstrated. Simulations show the generic value of the MemStir beyond biosurfactant production, for example, for animal cell cultivation. 相似文献
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Ma Tianli Jiang Yiming Elbehery Ali H. A. Blank Stephan Kurmayer Rainer Deng Li 《Hydrobiologia》2020,847(2):535-548
Hydrobiologia - The disturbing effect of a short-term cooling period during summer on planktonic bacterial community structure of an alpine lake was investigated using 16S rDNA pyrosequencing.... 相似文献
829.
Jeffrey A. Nadeau Robert G. Qualls Robert S. Nowak Robert R. Blank 《Biogeochemistry》2007,82(3):305-320
Increases in the growth rate of plants and microbes in the Mojave Desert in response to predicted increases in precipitation
and CO2 due to global climate change may induce nutrient limitations. This study was designed to measure the pool of potentially
bioavailable nutrients in soils of the Mojave Desert. Soils were collected from shrub and interspace microsites and then subjected
to amendment with buffered solutions of an excess of various enzymes. The products of each enzyme reaction were then measured
and the maximum quantity of hydrolyzable substrates was calculated. In interspace and shrub microsite soils, respectively,
14.5 and 9.7% of the organic C in the form cellulose, 60.0–97.8% and 61.2–100.0% of the organic N in the form protein, and
44.0 and 57.5% of the organic P was hydrolyzable. There were significant differences between microsites for hydrolyzable substrate
using all enzyme amendments, except protease. We propose that accumulations of hydrolyzable organic C, N, and P in the Mojave
Desert could be a result of the persistently dry soil conditions often found in desert ecosystems and the immobilization of
enzymes, which may result in low diffusivity of soil substrates and enzymes and, accordingly, little degradation of organic
C, N, and P. Alternatively, rapid nutrient cycling and immobilization by soil microorganisms could account for accumulations
of organic C, N, and P. Further refinement of the methods used in this study could lead to a valuable tool for the assessment
of potential bioavailability of nutrients in a variety of soils. 相似文献
830.
Summary The pressure-area isotherm and shear resistance of spectrin-actin monolayers indicate a close-packed structure at about 1.0 m2/mg protein. This surface area is equivalent to a thickness of about two monolayers at the erythrocyte membrane inner face. The maximum elasticity (lowest compressibility) occurs at 0.7 m2/mg protein, indicating the limit of reversible compression. The mechanical properties of the monolayers approximate those of the intact membrane, suggesting that the structures are similar and that these monolayers may account for many of thein vivo properties. 相似文献