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41.
Zhongzhi Zhang Shuigeng Zhou Lichao Chen Jihong Guan Lujun Fang Yichao Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):99-107
We propose a geometric growth model for weighted
scale-free networks, which is controlled by two tunable parameters.
We derive exactly the main characteristics of the networks, which
are partially determined by the parameters. Analytical results
indicate that the resulting networks have power-law distributions of
degree, strength, weight and betweenness, a scale-free behavior for
degree correlations, logarithmic small average path length and
diameter with network size. The obtained properties are in agreement
with empirical data observed in many real-life networks, which shows
that the presented model may provide valuable insight into the real
systems. 相似文献
42.
Inevitable self-similar topology of binary trees and their diverse hierarchical density 总被引:1,自引:0,他引:1
K. Paik P. Kumar 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):247-258
Self-similar topology, which can be characterized
as power law size distribution, has been found in diverse tree
networks ranging from river networks to taxonomic trees. In this
study, we find that the statistical self-similar topology is an
inevitable consequence of any full binary tree organization. We show
this by coding a binary tree as a unique bifurcation string. This
coding scheme allows us to investigate trees over the realm from
deterministic to entirely random trees. To obtain partial random
trees, partial random perturbation is added to the deterministic
trees by an operator similar to that used in genetic algorithms. Our
analysis shows that the hierarchical density of binary trees is more
diverse than has been described in earlier studies. We find that the
connectivity structure of river networks is far from strict
self-similar trees. On the other hand, organization of some social
networks is close to deterministic supercritical trees. 相似文献
43.
Z.-Q. Jiang L. Guo W.-X. Zhou 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):347-355
A phenomenological investigation of the endogenous and
exogenous dynamics in the fluctuations of capital fluxes is carried
out on the Chinese stock market using mean-variance analysis,
fluctuation analysis, and their generalizations to higher orders.
Non-universal dynamics have been found not only in the scaling
exponent α, which is different from the universal values 1/2
and 1, but also in the distributions of the ratio η=
σexo / σendo of individual stocks. Both
the scaling exponent α of fluctuations and the Hurst exponent
Hi increase in logarithmic form with the time scale Δt
and the mean traded value per minute 〈fi 〉,
respectively. We find that the scaling exponent αendo
of the endogenous fluctuations is independent of the time scale.
Multiscaling and multifractal features are observed in the data as
well. However, the inhomogeneous impact model is not verified. 相似文献
44.
Effective Relaxations and Partitioning Schemes for Solving Water Distribution Network Design Problems to Global Optimality 总被引:2,自引:0,他引:2
Hanif D. Sherali Shivaram Subramanian G.V. Loganathan 《Journal of Global Optimization》2001,19(1):1-26
In this paper, we address the development of a global optimization procedure for the problem of designing a water distribution network, including the case of expanding an already existing system, that satisfies specified flow demands at stated pressure head requirements. The proposed approach significantly improves upon a previous method of Sherali et al. (1998) by way of adopting tighter polyhedral relaxations, and more effective partitioning strategies in concert with a maximal spanning tree-based branching variable selection procedure. Computational experience on three standard test problems from the literature is provided to evaluate the proposed procedure. For all these problems, proven global optimal solutions within a tolerance of 10–4% and/or within 1$ of optimality are obtained. In particular, the two larger instances of the Hanoi and the New York test networks are solved to global optimality for the very first time in the literature. A new real network design test problem based on the Town of Blacksburg Water Distribution System is also offered to be included in the available library of test cases, and related computational results are presented. 相似文献
45.
There is wide acceptance of the need for a more holistic approach to sustainability. However, practical solutions remain elusive and tend to exhibit underlying conflicts between different paradigms and their associated methodologies. This paper argues the need to wield analytical tools that themselves embody the principles of systemic, ecological thinking. We present here a theoretical framework based on complexity science – focused on organisational and second order cybernetics – that highlights our understanding of the concept of sustainability. The paper goes on to reflect upon how current practice would benefit from such an approach. 相似文献
46.
给出由关于规则后件单增的模糊蕴涵算子构造的乘积推理机、"单点"模糊化方法和中心平均解模糊化方法设计的模糊系统, 并分析了它对紧集上连续可微函数的逼近特性.结果表明: 当模糊蕴涵算子θ满足θ(a,1)=1时, 模糊系统不具有逼近能力; 当θ(a,1)=p(a)(当0相似文献
47.
This paper focuses on dynamic, continuous-time production control problems in the fashion industry. Similar to the classical news-vendor problem, we consider a single product-type and the cumulative demand for items is not known until the end of the production horizon and therefore must be forecasted. Since there are periodic updates before a single selling season, actual demand during a period of time can only be determined by the end of the period. If the overall demand is overestimated, excessive inventory holding and production costs are paid and surpluses are sold at low prices at the end of the production horizon. If it is under-estimated, then sales are lost. The objective is to dynamically determine production orders which minimize overall expected costs. Since the optimal feedback for such a problem is characterized by thresholds evolving with time and system states, there is a significant computational burden in determining them. With the aid of the variational analysis and a decomposition, we derive a closed-form solution for the thresholds. A numerical study carried out to compare the decomposition and straightforward simulation-based solutions indicates the high accuracy of the suggested approach while the computational burden is dramatically reduced. 相似文献
48.
APPROXIMATEINERTIALMANIFOLDSFORTHESYSTEMOFTHEJ-JEQUATIONSAPPROXIMATEINERTIALMANIFOLDSFORTHESYSTEMOFTHEJ-JEQUATIONS¥CaiRizeng(... 相似文献
49.
A detailed study of the electrochemical oxidation of Benzo[a]pyrene (BaP) at the glassy carbon and pencil graphite electrodes was carried out in aqueous and nonaqueous media. Using square‐wave stripping mode, the compound yielded a well‐defined voltammetric response at pencil graphite electrode in acetate buffer, pH 4.8 at +1.13 V (vs. Ag/AgCl) (a preconcentration step being carried out at a fixed potential of +0.70 V for 180 s). The process could be used to determine BaP concentrations in the range 0.25–1.25 μM, with a detection limit of 0.027 μM (6.82 μg L?1). The applicability to assay of spiked human urine samples was also illustrated. 相似文献
50.
SE‐30 Graphite Composite Electrode: An Alternative for the Development of Electrochemical Biosensors
A new graphite composite electrode was constructed by mixing graphite powder with chromatography stationary phase, SE‐30, as the binder. The electrochemical behavior of the new electrode has been evaluated and compared with that of traditional carbon paste electrode (CPE). The proposed electrode provides a remarkable increase in the rate of electron transfer of biomolecules such as nicotinamide adenine dinucleotide (NADH), cysteine, ascorbic acid and catechol and shows a low surface fouling effects. The electrode shows highly promising results when used as an amperometic sensor for biocompounds such as NADH. 相似文献