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91.
An experimental thermal pulse combustor and a differential equation model of this device are shown to exhibit chaotic behavior under certain conditions. Chaos arises in the model by means of a progression of period-doubling bifurcations that occur when operating parameters such as combustor wall temperature or air/fuel flow are adjusted to push the system toward flameout. Bifurcation sequences have not yet been reproduced experimentally, but similarities are demonstrated between the dynamic features of pressure fluctuations in the model and experiment. Correlation dimension, Kolmogorov entropy, and projections of reconstructed attractors using chaotic time series analysis are demonstrated to be useful in classifying dynamical behavior of the experimental combustor and for comparison of test data to the model results. Ways to improve the model are suggested. (c) 1995 American Institute of Physics. 相似文献
92.
On the convergence of interior-reflective Newton methods for nonlinear minimization subject to bounds 总被引:11,自引:0,他引:11
We consider a new algorithm, an interior-reflective Newton approach, for the problem of minimizing a smooth nonlinear function of many variables, subject to upper and/or lower bounds on some of the variables. This approach generatesstrictly feasible iterates by using a new affine scaling transformation and following piecewise linear paths (reflection paths). The interior-reflective approach does not require identification of an activity set. In this paper we establish that the interior-reflective Newton approach is globally and quadratically convergent. Moreover, we develop a specific example of interior-reflective Newton methods which can be used for large-scale and sparse problems.Research partially supported by the Applied Mathematical Sciences Research Program (KC-04-02) of the Office of Energy Research of the U.S. Department of Energy under grant DE-FG02-86ER25013.A000, and in part by NSF, AFOSR, and ONR through grant DMS-8920550, and by the Advanced Computing Research Institute, a unit of the Cornell Theory Center which receives major funding from the National Science Foundation and IBM Corporation, with additional support from New York State and members of its Corporate Research Institute.Corresponding author. 相似文献
93.
It is the aim of the present work to prove, under appropriate conditions, lower estimates for the dimension of w
1 + ... + w
m
over , wherew
1,...,w
m
are given real numbers. In particular, if this dimension ism, i.e. ifw
1,...,w
m
are linearly independent over , we are also interested in a quantitative version of this fact. Our qualitative theorems generalize a result of Nesterenko. Its formulation is quite similar to the axiomatization of methods for algebraic independence, as it became usual during the last decade. 相似文献
94.
95.
A. D. Al-Rawwas C. E. Johnson M. F. Thomas S. E. Dann M. T. Weiler 《Hyperfine Interactions》1994,93(1):1521-1529
Mössbauer spectra have been recorded at 4.2 and 300 K on the series La1–x
Sr
x
FeO3, wherex varies from 0 to 1.0 in steps of 0.1. Neutron diffraction experiments have shown that the crystal structure is orthorhombic for 0x<0.3, rhombohedral for 0.4x0.7, and cubic for 0.8<x1.0. Mössbauer spectra at 4.2 K are composed of magnetic sextet components arising from different charge states of iron ions. In the orthorhombic and rhombohedral phases, the charge states Fe3+ and Fe5+ coexist. In the cubic phase, iron is present as Fe3+ and Fe4+ states. At 300 K, the samples are magnetically ordered in the range 0 x0.3 and the coexistence of Fe3+ and Fe5+ remains. For samples 0.4x1.0, the samples are paramagnetic. Fits to these spectra require two components, one corresponding to an Fe4+ state, the other being best described as an Fe3+ ion forx0.7 but forx>0.7 having a mean charge state which increases to 3.5 forx=1.0. 相似文献
96.
Michael Meyberg Elvezio Morenzoni Thomas Wutzke Uwe Zimmermann Franz Kottmann Klaus Jungmann Björn Matthias Thomas Prokscha 《Hyperfine Interactions》1994,87(1):1075-1081
At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface
+ (4 MeV) to an energy of 10 eV using appropriate moderators. These
+ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface
+) of the order of 10–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities. 相似文献
97.
98.
Numerical estimates of the Kolmogorov-Sinai entropy based on a finite amount of data decay towards zero in the relevant limits. Rewriting differences of block entropies as averages over decay rates, and ignoring all parts of the sample where these rates are uncomputable because of the lack of neighbours, yields improved entropy estimates. In the same way, the scaling range for estimates of the information dimension can be extended considerably. The improvement is demonstrated for experimental data. (c) 1996 American Institute of Physics. 相似文献
99.
Lazarus EA Navratil GA Greenfield CM Strait EJ Austin ME Burrell KH Casper TA Baker DR DeBoo JC Doyle EJ Durst R Ferron JR Forest CB Gohil P Groebner RJ Heidbrink WW Hong R Houlberg WA Howald AW Hsieh C Hyatt AW Jackson GL Kim J Lao LL Lasnier CJ Leonard AW Lohr J La Haye RJ Maingi R Miller RL Murakami M Osborne TH Perkins LJ Petty CC Rettig CL Rhodes TL Rice BW Sabbagh SA Schissel DP Scoville JT Snider RT Staebler GM Stallard BW Stambaugh RD St John HE Stockdale RE Taylor PL Thomas DM 《Physical review letters》1996,77(13):2714-2717
100.
Progress in semiconductor technology is accompanied by progress in knowledge and control of intrinsic and extrinsic defects in these materials, i.e. of vacancies or self-interstitials and dopant or impurity atoms, respectively. In spite of the large number of different experimental techniques, in particular electrical and optical ones, employed for the characterisation of these defects, there is a shortage of techniques that are able to identify the chemical nature, local structure, and dynamic properties of defects on an atomic scale. The missing sensitivity towards low defect concentrations in the range of 1016 cm–3 excludes many techniques which are known to fulfil these requirements. There is a growing number of experimental techniques, however, having in common the application of radioactive isotopes, so-called probe atoms, that deliver the required information also at low defect concentrations. Among the nuclear techniques, which will be discussed in context of their applicability to semiconductors, are the perturbed angular correlation spectroscopy, Mössbauer spectroscopy, and-nuclear magnetic resonance. But also non-nuclear techniques, such as the classical electrical and optical methods, being highly sensitive to low defect concentrations, will be shown to gain the missing sensitivity to the nature of defects if radioactive atoms are employed. For elemental semiconductors as well as for III–V, II–VI, and IV-IV compounds, it will be illustrated to what extent radioactive probe atoms contribute to delivering the needed knowledge and control of defects. 相似文献