全文获取类型
收费全文 | 79324篇 |
免费 | 361篇 |
国内免费 | 374篇 |
专业分类
化学 | 25122篇 |
晶体学 | 805篇 |
力学 | 6749篇 |
数学 | 32072篇 |
物理学 | 15311篇 |
出版年
2019年 | 36篇 |
2018年 | 10450篇 |
2017年 | 10270篇 |
2016年 | 6086篇 |
2015年 | 876篇 |
2014年 | 305篇 |
2013年 | 382篇 |
2012年 | 3828篇 |
2011年 | 10557篇 |
2010年 | 5666篇 |
2009年 | 6074篇 |
2008年 | 6656篇 |
2007年 | 8821篇 |
2006年 | 293篇 |
2005年 | 1381篇 |
2004年 | 1594篇 |
2003年 | 2016篇 |
2002年 | 1054篇 |
2001年 | 265篇 |
2000年 | 315篇 |
1999年 | 179篇 |
1998年 | 200篇 |
1997年 | 156篇 |
1996年 | 216篇 |
1995年 | 136篇 |
1994年 | 93篇 |
1993年 | 121篇 |
1992年 | 79篇 |
1991年 | 85篇 |
1990年 | 67篇 |
1989年 | 81篇 |
1988年 | 82篇 |
1987年 | 70篇 |
1986年 | 69篇 |
1985年 | 65篇 |
1984年 | 68篇 |
1983年 | 44篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 69篇 |
1979年 | 52篇 |
1978年 | 50篇 |
1977年 | 33篇 |
1973年 | 35篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
261.
Sumanta Chakraborty Soumitra SenGupta 《The European Physical Journal C - Particles and Fields》2017,77(8):573
We show that a possible resolution to the stabilization of an extra spatial dimension (radion) can be obtained solely in the context of gravitational dynamics itself without the necessity of introducing any external stabilizing field. In this scenario the stabilized value of the radion field gets determined in terms of the parameters appearing in the higher curvature gravitational action. Furthermore, the mass of the radion field and its coupling to the standard model fields are found to be in the weak scale implying possible signatures in the TeV scale colliders. Some resulting implications are also discussed. 相似文献
262.
263.
We examine the effect that the magnetic part of the Weyl tensor has on the large-scale expansion of space. This is done within the context of a class of cosmological models that contain regularly arranged discrete masses, rather than a continuous perfect fluid. The natural set of geodesic curves that one should use to consider the cosmological expansion of these models requires the existence of a non-zero magnetic part of the Weyl tensor. We include this object in the evolution equations of these models by performing a Taylor series expansion about a hypersurface where it initially vanishes. At the same cosmological time, measured as a fraction of the age of the universe, we find that the influence of the magnetic part of the Weyl tensor increases as the number of masses in the universe is increased. We also find that the influence of the magnetic part of the Weyl tensor increases with time, relative to the leading-order electric part, so that its contribution to the scale of the universe can reach values of \(\sim \)1%, before the Taylor series approximation starts to break down. 相似文献
264.
Wolfgang Wieland 《General Relativity and Gravitation》2017,49(3):38
Witten’s proof for the positivity of the ADM mass gives a definition of energy in terms of three-surface spinors. In this paper, we give a generalisation for the remaining six Poincaré charges at spacelike infinity, which are the angular momentum and centre of mass. The construction improves on certain three-surface spinor equations introduced by Shaw. We solve these equations asymptotically obtaining the ten Poincaré charges as integrals over the Nester–Witten two-form. We point out that the defining differential equations can be extended to three-surfaces of arbitrary signature and we study them on the entire boundary of a compact four-dimensional region of spacetime. The resulting quasi-local expressions for energy and angular momentum are integrals over a two-dimensional cross-section of the boundary. For any two consecutive such cross-sections, conservation laws are derived that determine the influx (outflow) of matter and gravitational radiation. 相似文献
265.
Andrey V. Kuznetsov 《Central European Journal of Physics》2011,9(1):146-156
This paper formulates a four kinetic state model for fast axonal transport. The paper further develops the Smith-Simmons model
that is based on equations governing intracellular molecular-motor-assisted transport; these equations are extended by considering
four rather than three kinetic states for organelles. The model considers plus-end and minus-end-oriented organelles that
can be either free (suspended in the cytosol) or attached to microtubules (MTs) (in the latter case organelles are transported
by molecular motors). The paper then develops a method for uncoupling differential equations of the proposed model. A perturbation
solution of this problem is obtained. The effect of transition between plus-end-oriented and minus-end oriented organelles
is discussed. The accuracy of the obtained perturbation solution is evaluated by comparing the zero-order and the first-order
results with a high-accuracy numerical solution. 相似文献
266.
Roberto Beneduci 《International Journal of Theoretical Physics》2011,50(12):3724-3736
In the present paper, we review some recent results about commutative positive operator valued measures (POVMs) and single
out some open problems. We introduce a conjecture about the extension of some recent results and prove some important consequences
of such conjecture. In particular, we prove that it implies the universal character of some of the mathematical objects we
introduce, i.e., the fact that they do not depend on the POV measure we are considering. We analyze the relevance of this
result. Finally, we point out that some of the results we present admit a constructive proof and we show the relevance of
this fact to the theory of commutative POV measures. 相似文献
267.
268.
Yu -Qi Li Xiao -Ming Xu Hui -Jun Ge 《The European Physical Journal A - Hadrons and Nuclei》2011,47(5):65
We divide the cross-section for a meson-meson reaction into three parts. The first part is for the quark-interchange process,
the second for quark-antiquark annihilation processes and the third for resonant processes. Master rate equations are established
to yield time dependence of fugacities of pions, rhos, kaons and vector kaons. The equations include cross-sections for inelastic
scattering of pions, rhos, kaons and vector kaons. Cross-sections for quark-interchange-induced reactions, that were obtained
in a potential model, are parametrized for convenient use. The number densities of π and ρ (K and K
* are altered by quark-interchange processes in equal magnitudes but opposite signs. The master rate equations combined with
the hydrodynamic equations for longitudinal and transverse expansion are solved with many sets of initial meson fugacities.
Quark-interchange processes are shown to be important in the contribution of the inelastic meson-meson scattering to the evolution
of mesonic matter. 相似文献
269.
Anatoly F. Nastoyashchiy 《Journal of Russian Laser Research》2011,32(3):238-246
We propose a simple target in the form of a miniature torus, in which the heavy shell is used to confine the plasma spread,
for a solution of the laser-fusion problem. We achieve a significant decrease of heat losses using an external magnetic field
and/or as a result of a self-sustaining magnetic field that is generated in the plasma. We formulate the conditions and determine
the energy of the laser pulse (or of a beam of fast charged particles) required to ignite a thermonuclear DD reaction and
obtain a positive energy yield. We show that the stopping range of α-particles does not exceed the small radius of the torus
within a broad range of the plasma and magnetic-field parameters. 相似文献
270.
Eric Weise 《Czechoslovak Journal of Physics》2005,55(1):A27-A34
COMPASS is a fixed target experiment at CERN studying nucleon spin structure in polarised deep inelastic muon nucleon scattering and hadron spectroscopy using hadron beams. The main goal of the COMPASS spin physics program is the measurement of the helicity contribution of the gluons to the nucleon spin, ΔG. This quantity is accessible via the photon-gluon-fusion process which can be selected by open charm production or production of hadron pairs with large transverse momenta. The spin physics program of COMPASS includes also measurements with a transversely polarised target. These allow to measure the transverse structure function.COMPASS has up to now successfully finished three runs with a muon beam of 160 GeV and a longitudinally polarized6LiD target in the years 2002, 2003 and 2004. An overview of the physics addressed by the muon program, with an emphasis on the ΔG/G measurement will be presented. The status of the analysis of the highpt hadron pairs, open charm, longitudinal and transverse asymmetries will be reviewed. 相似文献