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81.
We introduce and formalise a scheduling problem that consists in determining an optimum policy (i.e. one that minimises total inventory holding costs) to produce n part-types using a system that is able to share its capacity at all times among these part-types and that switches between an active and an inactive state for pre-known periods of time. Consequently, when active the system must produce enough reserves to meet the demand during the inactive interval. We show that there is always a simple optimum policy in which the production of the part-types is prioritised and, provided the units are properly defined, the optimum priority ordering corresponds to a non-decreasing sequence of the unit holding costs of the part-types. 相似文献
82.
83.
Timothy E. Burrow Raul G. Enriquez William F. Reynolds 《Magnetic resonance in chemistry : MRC》2009,47(12):1086-1094
The effect of various acquisition and processing parameters on the sensitivity of HMBC spectra for typical organic molecules has been systematically investigated. For molecules in the 200–600 molecular weight range, an acquisition time of 0.2 to 0.4 s, a recycle time of no more than 1.0 s, optimization for nJCH = 8 Hz and 512 time increments (with two‐ to fourfold linear prediction) are recommended. Some form of sine bell weighting along f2 and either Gaussian or sine bell weighting along f1 is suggested. The use of a 0.1‐s acquisition time and/or Gaussian or exponential weighting along f2 can result in dramatic sensitivity loss, particularly for correlation peaks involving protons with complex splitting patterns, and should be avoided. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
84.
In this paper, we propose an algorithm named BDS (Bound-Driven Search) that combines features of exact and approximate methods.
The proposed procedure may be seen as a local search algorithm that systematically explores (in a branch-and bound sense)
the most promising nodes, thus preventing solutions from being reevaluated. Additionally, it can be regarded as an exact method
as it may be able to guarantee that the solution found is optimal. We present the application of this new algorithm to a specific
problem domain: the permutation flow shop scheduling problem with makespan objective. The subsequent computational experiments
are encouraging, as the algorithm is able to yield exact or near exact solutions to most instances of the problem. Furthermore,
the algorithm outperforms one of the best state-of-the-art algorithms for the problem. 相似文献
85.
86.
Current work has evaluated uncertainty associated to quantification of several organic compounds present in particulate matter of atmospheric aerosols, setting out the stages of analytical procedure that contribute most to the global uncertainty. Several sources of uncertainty have been identified, which were clustered into five main contributions: sampling, extraction, clean-up, derivatization and analysis. A discussion of the main contributions to the overall uncertainty is reported, allowing authors to locate the largest ones and plan future improvements. Combined uncertainties ranged between 10-18% (alkanes), 12-16% (PAHs), 10-18% (alcohols) and 9-21% (acids). The analytical procedure was validated by analysing a standard reference material (SRM1649a, urban dust). Also, the proposed method was applied to the analysis of four samples of particulate matter. 相似文献
87.
Rodrigo R. O. Barros Raul A. Oliveira Leda Maria F. Gottschalk Elba P. S. Bon 《Applied biochemistry and biotechnology》2010,161(1-8):448-454
Although a number of filamentous fungi, such as Trichoderma and Aspergillus, are well known as producers of cellulases, xylanases, and accessory cellulolytic enzymes, the search for new strains and new enzymes has become a priority with the increase in diversity of biomass sources. Moreover, according to the type of pretreatment applied, biomass of the same type may require different enzyme blends to be efficiently hydrolyzed. This study evaluated cellulases, xylanases, and β-glucosidases produced by two fungi, the thermotolerant Acrophialophora nainiana and Ceratocystis paradoxa. Cells were grown in submerged culture on three carbon sources: lactose, wheat bran, or steam-pretreated sugarcane bagasse, a commonly used cattle feed in Brazil. Xylanase and endo-1-4-β-glucanase (CMCase) highest production were found in A. nainiana growing on lactose and reached levels of 2,200 and 2,016 IU/L, respectively. C. paradoxa showed highest activity for xylanase when grown on wheat bran and for β-glucosidase when grown on steam-treated bagasse, at levels of 12,728 and 1,068 IU/mL, respectively. 相似文献
88.
Garbiñe Álvarez Francisco Alcaide Oscar Miguel Laura Calvillo María Jesús Lázaro Jacob J. Quintana Juan Carlos Calderón Elena Pastor 《Journal of Solid State Electrochemistry》2010,14(6):1027-1034
This paper presents the behavior of ordered mesoporous carbon (OMC)-supported catalysts as anodes for direct methanol fuel
cells (DMFC), fed with an aqueous methanol solution. OMC samples were prepared by the nanocasting method from a polymerized
furan resin using mesoporous silica as a template. Pt and PtRu nanoparticles were supported on OMC with high dispersion, the
particle size being 2.4 nm at PtRu loading of 15 wt.%. The resulting catalysts were analyzed using carbon monoxide stripping
voltammetry, cyclic voltammetry, and chronoamperometry in three-electrode experiments and recording cell voltage vs. current
density curves in practical DMFC. It was found that PtRu-catalyzed technical electrodes exhibited good activity towards methanol
electrooxidation in half-cell experiments under fuel-cell-relevant conditions. Specifically, Pt85Ru15/OMC catalyst showed the highest catalytic enhancement compared to Pt/OMC for the steady-state electrooxidation of methanol
at 60 °C and 0.5 V, by a factor of 22 in 2-M MeOH solution. DMFC single cells yielded an open-circuit voltage of 0.625 V at
60 °C. Polarization curves indicate that DMFC with OMC-supported Pt85Ru15 catalyst at the anode exhibited the best performance. 相似文献
89.
Two papers with similar optimality conditions were published by I. Ginchev, and by D. Bedna?ík and K. Pastor independently in Nonlinear Analysis in 2011. We compare these results. We also show the equivalence of two definitions of ?-stability of vector functions. Moreover, we generalize another result given by I. Ginchev and V. I. Ivanov [J. Math. Anal. Appl. 340 (2008), 646–657] and compare it with the previously mentioned optimality conditions. 相似文献
90.