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981.
电力系统是一个由多个子系统构成的综合性系统,作为一个能够实现海量数据处理同时具有高实时性、高可靠性的管理控制平台,需要电力系统能够实现对所辖多个子系统进行复杂、细密、大范围的访问控制,这些条件要求能够设计出合理有效的访问控制模型。为了实现安全、可靠、高效的电力系统访问控制提出了将传统电力系统同云存储平台相结合的访问控制方案,通过云存储平台对数据进行存取可以达到大数据量、均衡负载、安全可靠的目的;通过添加可信度因子构建访问控制模型,根据不同用户的可行度计算值分配给以不同的权限,匹配其可操作的资源,实现了对于用户操作对象的细化识别。 相似文献
982.
Laura García-Cansino María ngeles García María Luisa Marina 《Molecules (Basel, Switzerland)》2021,26(17)
The different activity and toxicity that the enantiomers of agrochemicals may have requires the development of stereoselective analytical methodologies enabling the individual determination of each enantiomer. The aim of this work was to develop the first Electrokinetic Chromatography methodology enabling the simultaneous enantiomeric separation of carfentrazone-ethyl herbicide and its hydrolysis metabolite carfentrazone. The use of an anionic cyclodextrin as chiral selector (captisol at 2.5% (w/v)) in a 25 mM acetate buffer, at a temperature of 30 °C, and an applied voltage (reverse polarity) of −30 kV, allowed the simultaneous separation of the four enantiomers of the two compounds studied in 6.8 min with enantiomeric resolutions of 5.0 for carfentrazone-ethyl and 5.1 for carfentrazone. Analytical characteristics of the developed method were evaluated and found adequate to achieve the quantitation of carfentrazone-ethyl and carfentrazone. Analysis of a commercial herbicide formulation showed the potential of the method for the quality control of these agrochemical products. Degradation studies for carfentrazone-ethyl revealed that no significant degradation took place in cleaned sand samples while a significant but not stereoselective degradation took place in soils for the whole period of time considered (seven days). 相似文献
983.
984.
985.
Moradian F Khajeh K Naderi-Manesh H Ahmadvand R Sajedi RH Sadeghizadeh M 《Applied biochemistry and biotechnology》2006,134(1):77-87
Two Bacillus sp. strains, HR-08 and KR-8102, isolated from soil of the west and north parts of Iran were screened on gelatin agar medium
for their ability to produce alkaline protease. The enzymes were active in a wide pH range (6.0–11.0) and stable in the alkaline
range (7.0–12.0). The optimum temperatures for the protease from HR-08 and KR-8102 were 65 and 50°C, respectively. The irreversible
thermoinactivation of HR-08 and KR-8102 proteases showed that the stability of HR-08 enzyme was higher than that of KR-8102
and the half-lives of these enzymes were 95 and 32 min at 50°C, respectively. In the presence of 10 mM Ca2+, HR-08 retained 100, 90, and 20% of its initial activity after heating for 30 min at 50, 60, and 70°C, respectively. Enzymes
were inhibited by phenylmethylsulfonyl fluoride and iodoacetate. After inhibition by iodoacetate, both enzymes were reactivated
by dithiothreitol. These data show that the enzymes seem to be thiol-dependent serine alkaline proteases. The enzymes especially
from HR-08 were stable in the presence of H2O2, surfactants, and local detergents; their activities were enhanced in the presence of 5 mM Fe2+; and the presence of 5mM metal ions such as Mg2+, Cu2+, and Mn2+ produced almost no effect. 相似文献
986.
987.
Dominik Janzing 《Journal of statistical physics》2006,122(3):531-556
A heat engine is a machine which uses the temperature difference between a hot and a cold reservoir to extract work. Here
both reservoirs are quantum systems and a heat engine is described by a unitary transformation which decreases the average energy of the bipartite system. On the molecular scale, the ability of implementing a (good) unitary heat engine
is closely connected to the ability of performing logical operations and classical computing. This is shown by several examples:
相似文献
(1) | The most elementary heat engine is a SWAP-gate acting on 1 hot and 1 cold two-level systems with different energy gaps. |
(2) | An optimal unitary heat engine on a pair of 3-level systems can directly implement OR and NOT gates, as well as copy operations. The ability to implement this heat engine on each pair of 3-level systems taken from the hot and the cold ensemble therefore allows universal classical computation. |
(3) | Optimal heat engines operating on one hot and one cold oscillator mode with different frequencies are able to calculate polynomials and roots approximately. |
(4) | An optimal heat engine acting on 1 hot and n cold 2-level systems with different level spacings can even solve the NP-complete problem KNAPSACK. Whereas it is already known that the determination of ground states of interacting many-particle systems is NP-hard, the optimal heat engine is a thermodynamic problem which is NP-hard even for n non-interacting spin systems. This result suggests that there may be complexity-theoretic limitations on the efficiency of molecular heat engines. |
988.
We present a parallel algorithm for the overlapping domain decomposition boundary integral equation method for two dimensional partial differential equations. In addition to the improvement of the ill-conditioning and the computational efficiency achieved by domain partitioning, using a parallel computer with p processors can offer up to p times efficiency. Assuming direct solution is used throughout, partitioning the domain into p subregions and employing a processor for each subproblem, overall, result in p2 times efficiency over using a single domain and a single processor, taking into account that a sequential algorithm of the underlying method can improve the computational efficiency at least p times over using a single domain. Some numerical results showing the efficiency of the parallel technique will be presented. 相似文献
989.
Improvements in the treatment of stress constraints in structural topology optimization problems 总被引:1,自引:0,他引:1
J. París F. Navarrina M. Casteleiro 《Journal of Computational and Applied Mathematics》2010,234(7):2231-2238
Topology optimization of continuum structures is a relatively new branch of the structural optimization field. Since the basic principles were first proposed by Bendsøe and Kikuchi in 1988, most of the work has been dedicated to the so-called maximum stiffness (or minimum compliance) formulations. However, since a few years different approaches have been proposed in terms of minimum weight with stress (and/or displacement) constraints.These formulations give rise to more complex mathematical programming problems, since a large number of highly non-linear (local) constraints must be taken into account. In an attempt to reduce the computational requirements, in this paper, we propose different alternatives to consider stress constraints and some ideas about the numerical implementation of these algorithms. Finally, we present some application examples. 相似文献
990.
We propose a molecular simulation method using genetic algorithm (GA) for biomolecular systems to obtain ensemble averages efficiently. In this method, we incorporate the genetic crossover, which is one of the operations of GA, to any simulation method such as conventional molecular dynamics (MD), Monte Carlo, and other simulation methods. The genetic crossover proposes candidate conformations by exchanging parts of conformations of a target molecule between a pair of conformations during the simulation. If the candidate conformations are accepted, the simulation resumes from the accepted ones. While conventional simulations are based on local update of conformations, the genetic crossover introduces global update of conformations. As an example of the present approach, we incorporated genetic crossover to MD simulations. We tested the validity of the method by calculating ensemble averages and the sampling efficiency by using two kinds of peptides, ALA3 and (AAQAA)3. The results show that for ALA3 system, the distribution probabilities of backbone dihedral angles are in good agreement with those of the conventional MD and replica-exchange MD simulations. In the case of (AAQAA)3 system, our method showed lower structural correlation of α-helix structures than the other two methods and more flexibility in the backbone ψ angles than the conventional MD simulation. These results suggest that our method gives more efficient conformational sampling than conventional simulation methods based on local update of conformations. © 2018 Wiley Periodicals, Inc. 相似文献