全文获取类型
收费全文 | 8141篇 |
免费 | 1070篇 |
国内免费 | 642篇 |
专业分类
化学 | 4272篇 |
晶体学 | 53篇 |
力学 | 574篇 |
综合类 | 48篇 |
数学 | 1038篇 |
物理学 | 3868篇 |
出版年
2024年 | 25篇 |
2023年 | 68篇 |
2022年 | 233篇 |
2021年 | 254篇 |
2020年 | 280篇 |
2019年 | 255篇 |
2018年 | 264篇 |
2017年 | 274篇 |
2016年 | 344篇 |
2015年 | 259篇 |
2014年 | 368篇 |
2013年 | 798篇 |
2012年 | 438篇 |
2011年 | 440篇 |
2010年 | 377篇 |
2009年 | 447篇 |
2008年 | 463篇 |
2007年 | 500篇 |
2006年 | 446篇 |
2005年 | 360篇 |
2004年 | 393篇 |
2003年 | 368篇 |
2002年 | 298篇 |
2001年 | 266篇 |
2000年 | 246篇 |
1999年 | 192篇 |
1998年 | 172篇 |
1997年 | 145篇 |
1996年 | 126篇 |
1995年 | 110篇 |
1994年 | 92篇 |
1993年 | 84篇 |
1992年 | 68篇 |
1991年 | 62篇 |
1990年 | 41篇 |
1989年 | 44篇 |
1988年 | 34篇 |
1987年 | 27篇 |
1986年 | 48篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 7篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有9853条查询结果,搜索用时 0 毫秒
51.
Madalina Deaconu Nicolas Fournier Etienne Tanré 《Methodology and Computing in Applied Probability》2003,5(2):131-158
By continuing the probabilistic approach of Deaconu et al. (2001), we derive a stochastic particle approximation for the Smoluchowski coagulation equations. A convergence result for this model is obtained. Under quite stringent hypothesis we obtain a central limit theorem associated with our convergence. In spite of these restrictive technical assumptions, the rate of convergence result is interesting because it is the first obtained in this direction and seems to hold numerically under weaker hypothesis. This result answers a question closely connected to the Open Problem 16 formulated by Aldous (1999). 相似文献
52.
Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented. 相似文献
53.
《Tetrahedron letters》2003,44(40):7411-7415
The first total synthesis of two E type I phytoprostanes from furan, azelaic acid monomethyl ester and rac-1,2-epoxybutane is described. The key features of our synthetic strategy encompass an enzymatic kinetic resolution of a hydroxycyclopentenone, a Co-salen hydrolytic kinetic resolution of a terminal epoxide and a tandem conjugate addition/diastereoselective protonation sequence to construct the protected phytoprostanes. Mild cleavage of the silyl protective groups followed by enzymatic ester hydrolysis afforded the free E-type phytoprostanes. 相似文献
54.
55.
D. A. Lavis 《Foundations of Physics》2004,34(4):669-688
Simple models have played an important role in the discussion of foundational issues in statistical mechanics. Among them the spin-echo system is of particular interest since it can be realized experimentally. This has led to inferences being drawn about approaches to the foundations of statistical mechanics, particularly with respect to the use of coarse-graining. We examine these claims with the help of computer simulations. 相似文献
56.
Su-Yun Huang Chuhsing Kate Hsiao Ching-Wei Chang 《Annals of the Institute of Statistical Mathematics》2003,55(3):655-670
The article provides a refinement for the volume-corrected Laplace-Metropolis estimator of the marginal likelihood of DiCiccioet al. The correction volume of probability α in DiCiccioet al. is fixed and suggested to take the value α=0.05. In this article α is selected based on an asymptotic analysis to minimize
the mean square relative error (MSRE). This optimal choice of α is shown to be invariant under linear transformations. The
invariance property leads to easy implementation for multivariate problems. An implementation procedure is provided for practical
use. A simulation study and a real data example are presented. 相似文献
57.
I. Capek J. Chudej S. Janí
kov 《Journal of polymer science. Part A, Polymer chemistry》2003,41(6):804-820
The sterically stabilized emulsion polymerization of styrene initiated by a water‐soluble initiator at different temperatures has been investigated. The rate of polymerization (Rp) versus conversion curve shows the two non‐stationary‐rate intervals typical for the polymerization proceeding under non‐stationary‐state conditions. The shape of the Rp versus conversion curve results from two opposite effects—the increased number of particles and the decreased monomer concentration at reaction loci as the polymerization advances. At elevated temperatures the monomer emulsion equilibrates to a two‐phase or three‐phase system. The upper phase is transparent (monomer), and the lower one is blue colored, typical for microemulsion. After stirring such a multiphase system and initiation of polymerization, the initial coarse polymer emulsion was formed. The average size of monomer/polymer particles strongly decreased up to about 40% conversion and then leveled off. The initial large particles are assumed to be highly monomer‐swollen particles formed by the heteroagglomeration of unstable polymer particles and monomer droplets. The size of the “highly monomer” swollen particles continuously decreases with conversion, and they merge with the growing particles at about 40–50% conversion. The monomer droplets and/or large highly monomer‐swollen polymer particles also serve as a reservoir of monomer and emulsifier. The continuous release of nonionic (hydrophobic) emulsifier from the monomer phase increases the colloidal stability of primary particles and the number of polymer particles, that is, the particle nucleation is shifted to the higher conversion region. Variations of the square and cube of the mean droplet radius with aging time indicate that neither the coalescence nor the Ostwald ripening is the main driving force for the droplet instability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 804–820, 2003 相似文献
58.
Keith Jonathan M. Kroese Dirk P. Bryant Darryn 《Methodology and Computing in Applied Probability》2004,6(1):29-53
A recent development of the Markov chain Monte Carlo (MCMC) technique is the emergence of MCMC samplers that allow transitions between different models. Such samplers make possible a range of computational tasks involving models, including model selection, model evaluation, model averaging and hypothesis testing. An example of this type of sampler is the reversible jump MCMC sampler, which is a generalization of the Metropolis–Hastings algorithm. Here, we present a new MCMC sampler of this type. The new sampler is a generalization of the Gibbs sampler, but somewhat surprisingly, it also turns out to encompass as particular cases all of the well-known MCMC samplers, including those of Metropolis, Barker, and Hastings. Moreover, the new sampler generalizes the reversible jump MCMC. It therefore appears to be a very general framework for MCMC sampling. This paper describes the new sampler and illustrates its use in three applications in Computational Biology, specifically determination of consensus sequences, phylogenetic inference and delineation of isochores via multiple change-point analysis. 相似文献
59.
Charging of the surface of an oxide caused by the adsorption of hydrogen ions and ions of inert 1:1 electrolyte was investigated by using grand canonical Monte Carlo simulation technique. In particular, adsorption isotherms of protons as well as of ions of the electrolyte together with the resulting charge density of the surface were obtained for different system parameters. Also, the effect of the surface energetic heterogeneity and the concentration of the background electrolyte on the isotherms and the charge density curves was examined. Furthermore, lateral interactions in the mixed adsorbed phase were taken into account in the modeling of the system behavior. The obtained results, in general, suggest that the three factors mentioned above may have substantial influence on the charging mechanism at the liquid/oxide interface. 相似文献
60.
The edge structure and stability of monolayer-high islands fabricated on Si(001) surfaces by scanning tunneling microscopy have been analyzed theoretically. In contrast to the edges of similar islands grown by depositing Si, the properties of edges of fabricated islands are determined by the length of the trench of dimers that are removed to create the island. We demonstrate the possibility of controlling the edge structure, and thus the stability, through a selective process of atom removal. 相似文献