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61.
62.
We demonstrate the generation of high-energy picosecond pulses directly from a thin-disk laser oscillator by employing a self-imaging active multipass geometry. Stable single-pulse operation has been obtained with an average output power in excess of 50 W, excluding a cw background of 8%, at a repetition rate of 3.8 MHz. Self-starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The maximum pulse energy was 13.4 microJ at a pulse duration of 1.36 ps with a time-bandwidth product of 0.34. Single-pass external frequency doubling with a conversion efficiency of 60% yielded >28 W of average power at 515 nm. 相似文献
63.
64.
Anna Zieleniewska Prof. Dr. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9602-9607
At the focal point of this work is the photophysical characterization of three meso–meso ethene-bridged diporphyrins featuring a diverse metallation pattern. Detailed investigations by means of cyclic voltammetry, absorption, fluorescence, and femto-/nanosecond transient absorption spectroscopy revealed the impact of open-shell nickel(II) on the electronic communication in ethene-bridged heterobimetallic diporphyrins. 相似文献
65.
This paper presents a framework for incorporating arbitrary implicit multistep schemes into the lattice Boltzmann method. While the temporal discretization of the lattice Boltzmann equation is usually derived using a second-order trapezoidal rule, it appears natural to augment the time discretization by using multistep methods. The effect of incorporating multistep methods into the lattice Boltzmann method is studied in terms of accuracy and stability. Numerical tests for the third-order accurate Adams-Moulton method and the second-order backward differentiation formula show that the temporal order of the method can be increased when the stability properties of multistep methods are considered in accordance with the second Dahlquist barrier. 相似文献
66.
Tobias Ullrich Piermaria Pinter Julian Messelberger Philipp Haines Ramandeep Kaur Jun.-Prof. Dr. Max M. Hansmann Dr. Dominik Munz Prof. Dr. Dirk M. Guldi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7980-7988
Herein, we present a new class of singlet fission (SF) materials based on diradicaloids of carbene scaffolds, namely cyclic (alkyl)(amino)carbenes (CAACs). Our modular approach allows the tuning of two key SF criteria: the steric factor and the diradical character. In turn, we modified the energy landscapes of excited states in a systematic manner to accommodate the needs for SF. We report the first example of intermolecular SF in solution by dimer self-assembly at cryogenic temperatures. 相似文献
67.
A short summary of the present status of prompt particle decays in the mass
region is presented. It includes recent results from a GAMMASPHERE experiment, which aimed at the combined high-resolution spectroscopy of light charged particles and
-rays to allow for more detailed studies of known decays and the identification of new cases of discrete prompt proton and
-particle emission from highly and superdeformed states.Received: 10 October 2002, Published online: 17 February 2004PACS:
23.50. + z Decay by proton emission - 23.60. + e
decay - 27.40. + z
- 27.50. + e
相似文献
68.
The Generalized Cross Entropy Method, with Applications to Probability Density Estimation 总被引:1,自引:0,他引:1
Nonparametric density estimation aims to determine the sparsest model that explains a given set of empirical data and which uses as few assumptions as possible. Many of the currently existing methods do not provide a sparse solution to the problem and rely on asymptotic approximations. In this paper we describe a framework for density estimation which uses information-theoretic measures of model complexity with the aim of constructing a sparse density estimator that does not rely on large sample approximations. The effectiveness of the approach is demonstrated through an application to some well-known density estimation test cases. 相似文献
69.
Gamaliel?BléEmail author Víctor?Castellanos Manuel?J.?Falconi 《Bulletin of the Brazilian Mathematical Society》2003,34(2):333-345
In this paper we consider a system whose state
x changes to (x) if a perturbation occurs at the time
t, for
. Moreover, the state
x changes to the new state
(x) at time
t, for
. It is assumed that the
number of perturbations in an interval (0,
t) is a Poisson process. Here
and are measurable maps from a measure space
into itself. We give
conditions for the existence of a stationary distribution of the
system when the maps and commute, and we prove that any
stationary distribution is an invariant measure of these
maps. 相似文献
70.
Bl. Sendov 《Constructive Approximation》1996,12(1):31-65
The problem of finding appropriate mathematical objects to model images is considered. Using the notion of acompleted graph of a bounded function, which is a closed and bounded point set in the three-dimensional Euclidean spaceR 3, and exploring theHausdorff distance between these point sets, a metric spaceIM D of functions is defined. The main purpose is to show that the functionsf∈IM D, defined on the squareD=[0,1]2, are appropriate mathematical models of real world images. The properties of the metric spaceIM D are studied and methods of approximation for the purpose of image compression are presented. The metric spaceIM D contains the so-calledpixel functions which are produced through digitizing images. It is proved that every functionf∈IM D may be digitized and represented by a pixel functionp n, withn pixels, in such a way that the distance betweenf andp n is no greater than 2n ?1/2. It is advocated that the Hausdorff distance is the most natural one to measure the difference between two pixel representations of a given image. This gives a natural mathematical measure of the quality of the compression produced through different methods. 相似文献