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951.
Felix Roosen-Runge Marcus Hennig Tilo Seydel Fajun Zhang Maximilian W.A. Skoda Stefan Zorn Robert M.J. Jacobs Marco Maccarini Peter Fouquet Frank Schreiber 《Biochimica et Biophysica Acta - Proteins and Proteomics》2010,1804(1):68-75
We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models. 相似文献
952.
Proton transport inside the biofilm limits electrical current generation by anode-respiring bacteria
Anode-respiring bacteria (ARB) in a biofilm anode carry out an oxidation half-reaction of organic matter, producing an electrical current from renewable biomass, including wastes. At the same time, ARB produce protons, usually one proton for every electron. Our study shows how current density generated by an acclimated ARB biofilm was limited by proton transport out of the biofilm. We determined that, at high current densities, protons were mainly transported out of the biofilm by protonating the conjugate base of the buffer system; the maximum current generation was directly related to the transport of the buffer, mainly by diffusion, into and out of the biofilm. With non-limiting acetate concentrations, the current density increased with higher buffer concentrations, going from 2.21 +/- 0.02 A m(-2) with 12.5-mM phosphate buffer medium to 9.3 +/- 0.4 A m(-2) using a 100-mM phosphate buffer at a constant anode potential of E(anode) = -0.35 V versus Ag/AgCl. Increasing the concentration of sodium chloride in the medium (0-100 mM) increased current density by only 15%, indicating that ion migration was not as important as diffusion of phosphate inside the biofilm. The current density also varied strongly with medium pH as a result of the buffer speciation: The current density was 10.0 +/- 0.8 A m(-2) at pH 8, and the pH giving one-half the maximum rate was 6.5. A j-V curve analysis using 100 mM phosphate buffer showed a maximum current density of 11.5 +/- 0.9 A m(-2) and half-saturation potential of -0.414 V versus Ag/AgCl, a value that deviated only slightly from the standard acetate potential, resulting in small anode-potential losses. We discuss the implications of the proton-transport limitation in the field of microbial fuel cells and microbial electrolytic cells. 相似文献
953.
Eugenio Foresti Marcelo Zaiat Marcus Vallero 《Reviews in Environmental Science and Biotechnology》2006,5(1):3-19
Anaerobic digesters have been responsible for the removal of large fraction of organic matter (mineralization of waste sludge)
in conventional aerobic sewage treatment plants since the early years of domestic sewage treatment (DST). Attention on the
anaerobic technology for improving the sustainability of sewage treatment has been paid mainly after the energy crisis in
the 1970s. The successful use of anaerobic reactors (especially up-flow anaerobic sludge blanket (UASB) reactors) for the
treatment of raw domestic sewage in tropical and sub-tropical regions (where ambient temperatures are not restrictive for
anaerobic digestion) opened the opportunity to substitute the aerobic processes for the anaerobic technology in removal of
the influent organic matter. Despite the success, effluents from anaerobic reactors treating domestic sewage require post-treatment
in order to achieve the emission standards prevailing in most countries. Initially, the composition of this effluent rich
in reduced compounds has required the adoption of post-treatment (mainly aerobic) systems able to remove the undesirable constituents.
Currently, however, a wealth of information obtained on biological and physical-chemical processes related to the recovery
or removal of nitrogen, phosphorus and sulfur compounds creates the opportunity for new treatment systems. The design of DST
plant with the anaerobic reactor as core unit coupled to the pre- and post-treatment systems in order to promote the recovery
of resources and the polishing of effluent quality can improve the sustainability of treatment systems. This paper presents
a broader view on the possible applications of anaerobic treatment systems not only for organic matter removal but also for
resources recovery aiming at the improvement of the sustainability of DST. 相似文献
954.
Here we highlight two ontologically different modes of care and management of endemic stingless bees in Australia. While Indigenous Yolngu and backyard beekeepers both engage in caring for stingless bees, neither way of living with bees would classically be defined as ‘domestication’, yet bees are encompassed within the ‘home’, or domus. This requires a different perspective in relation to the kinds of multispecies connections between humans and other beings. We propose that the key difference between Aboriginal Australians hunting for sugarbag on country and beekeeping in the backyard is in the way bee populations are maintained and in the degree of ecological separation from the surrounding environment. For Yolngu the domus is the bush. Backyard beekeeping involves modes of care that separate bees from outside predators, pests and other detrimental elements, while the Yolngu relationship with bees is primarily concerned with maintaining the integrity of the surrounding ecology, or the homeland. 相似文献
955.
Robert E. Furrow Marcus W. Feldman 《Evolution; international journal of organic evolution》2014,68(3):673-683
Epigenetic variation has been observed in a range of organisms, leading to questions of the adaptive significance of this variation. In this study, we present a model to explore the ecological and genetic conditions that select for epigenetic regulation. We find that the rate of temporal environmental change is a key factor controlling the features of this evolution. When the environment fluctuates rapidly between states with different phenotypic optima, epigenetic regulation may evolve but we expect to observe low transgenerational inheritance of epigenetic states, whereas when this fluctuation occurs over longer time scales, regulation may evolve to generate epigenetic states that are inherited faithfully for many generations. In all cases, the underlying genetic variation at the epigenetically regulated locus is a crucial factor determining the range of conditions that allow for evolution of epigenetic mechanisms. 相似文献
956.
957.
Progestagen-impregnated vaginal sponges + PMSG were used to synchronize oestrus in crossbred adult ewes which were inseminated 56 h after sponge removal with 0.5 ml diluted semen containing 400, 200, 100, 50 or 25 x 10(6) spermatozoa per insemination. The diluent was skim milk-citrate or pooled seminal plasma. There was no difference in reproductive performance due to the insemination medium. Fertility (no. of ewes lambing) after insemination of 400 or 200 x 10(6) spermatozoa was 68% and was similar to that observed after natural service at progestagen-induced oestrus. When less than or equal to 100 x 10(6) spermatozoa were inseminated, fertility fell markedly and the number of lambs per ewe inseminated decreased. A decrease in litter size also occurred. The data indicate that insemination of 200 x 10(6) spermatozoa, i.e. less than 10% of the number in a single ram ejaculate, allows normal conception rates in progestagen-treated ewes. 相似文献
958.
J V Madassery B Gillard D M Marcus M H Nahm 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(3):823-829
To identify surface Ag uniquely expressed on human germinal center B cells, we produced a mouse mAb, HJ6. When tonsillar lymphocytes were examined, HJ6 did not label T cells and labeled only about half of PNA+ B cells that were HK23-. HJ6 did not label mononuclear cells from peripheral blood, splenocytes, and any of 29 cell lines including 23 B cell lines. This binding pattern of HJ6 was very similar to that of a mAb named 5B5. It was shown previously that 5B5 bound a glycolipid named CTH (CD77) and its Ag was expressed on HK23- PNA+ tonsillar lymphocytes and Burkitt's lymphoma cell lines. Despite the similarity, HJ6 differed from 5B5: HJ6 did not stain Burkitt's lymphoma cell lines and stained PNA+ tonsillar lymphocytes in the presence of a large concentration of galactose. When its binding to isolated glycolipids was studied, HJ6 was found to bind globoside and Forssman Ag and not to other glycolipids including CTH. When its binding to neutral glycolipids extracted from tonsillar lymphocytes was studied, HJ6 bound only globoside; Forssman Ag was not detected in tonsillar lymphocytes. Taken together, we conclude that globoside is a B cell Ag expressed on a subpopulation of germinal center B cells. 相似文献
959.
960.
Elizabeth M. Anderson Eileen C. Goodwin Anurag Verma Claudia P. Arevalo Marcus J. Bolton Madison E. Weirick Sigrid Gouma Christopher M. McAllister Shannon R. Christensen JoEllen Weaver Philip Hicks Tomaz B. Manzoni Oluwatosin Oniyide Holly Ramage Divij Mathew Amy E. Baxter Derek A. Oldridge Allison R. Greenplate Scott E. Hensley 《Cell》2021,184(7):1858-1864.e10