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991.
Harray Yserentant 《Numerische Mathematik》1997,76(1):87-109
Summary. Particle methods are numerical methods designed to solve problems in fluid mechanics and related problems in continuum mechanics.
A general approach to the construction of such particle methods is presented in this article. The particles are no mass points
but possess a finite extension. They can rotate in space and have a spin. The conservation of mass is automatically guaranteed
by the ansatz. The forces of interaction between the particles are derived in a canonical way from the force laws of continuum
mechanics and are directly based on a regularized stress tensor. In the absence of external forces and of heat sources and
sinks, momentum, angular momentum, and energy are conserved as in the continuum case.
Received February 17, 1995 / Revised version received December 28, 1995 相似文献
992.
Robert S. Van Dyck Jr. Steven L. Zafonte Paul B. Schwinberg 《Hyperfine Interactions》2001,132(1-4):163-175
Based on the use of a single ion, isolated at the center of a cryogenically cooled Penning trap, an environment is produced
which makes this mass spectrometer remarkably free of systematic errors. The most notable developments in our quest for an
ultra-high accuracy instrument were (a) the compensation of the trapping potential, (b) the discovery that motional sidebands
could manipulate radial energies, (c) the use of multiply-charged ions that could improve signal-to-noise, and (d) the use
of an ultra-stable superconducting magnet/cryostat system with drift <0.010 ppb/h. The dominant systematic errors are associated
with radial electric fields caused by image charges in the trap electrodes and with the rf-electrical drive field used to
determine the harmonic axial resonance. To illustrate the potential of this improved spectrometer, the four-fold improved
measurement of the proton's mass and the eight-fold improved measurement of oxygen's atomic mass will be described.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
In a previous paper the authors introduced seven complete congruences on the lattice ev(I of e-varieties of regular semigroups of the form
P
:U
P
VPU=PV, whereP is drawn from a small set of e-varieties: left zero, right zero, rectangular bands, groups, left groups, right groups and completely simple semigroups. Four new complete congruences are introduced here of the form
P
:U
P
VPU=PV, whereP is one of the following classes of regular semigroups: left monoids, right monoids, monoids, idempotent generated semigroups. For each complete congruence on ev(I) and eachUev(I), the -class ofU is an interval [U
,U
] so that there is associated with each such congruence an idempotent operatorUU
on ev(I). This paper establishes numerous results concerning the commutativity of operators of this form.This work was supported in part by NSERC Grant 4044. 相似文献
994.
Hamilton equations based not only upon the Poincaré–Cartan equivalent of a first-order Lagrangian, but also upon its Lepagean equivalent are investigated. Lagrangians which are singular within the Hamilton–De Donder theory, but regularizable in this generalized sense are studied. Legendre transformation for regularizable Lagrangians is proposed and Hamilton equations, equivalent with the Euler–Lagrange equations, are found. It is shown that all Lagrangians affine or quadratic in the first derivatives of the field variables are regularizable. The Dirac field and the electromagnetic field are discussed in detail. 相似文献
995.
996.
M. Karny L. Batist B. A. Brown D. Cano-Ott R. Collatz A. Gadea R. Grzywacz A. Guglielmetti M. Hellstrm Z. Hu Z. Janas R. Kirchner F. Moroz A. Piechaczek A. P
ochocki E. Roeckl B. Rubio K. Rykaczewski M. Shibata J. Szerypo J. L. Tain V. Wittmann A. Whr 《Nuclear Physics A》2001,690(4):45
The Gamow–Teller β decays of the neutron-deficient indium isotopes 104–107In have been investigated by using total absorption γ-ray spectrometry on mass-separated sources. The experimental Gamow–Teller strength, deduced as a function of the excitation energy in the daughter nuclei 104–107Cd, is compared to shell-model predictions. 相似文献
997.
998.
MgB_2超导电性的发现及新一轮高临界温度超导研究热潮 总被引:1,自引:0,他引:1
20 0 1年 1月 10日 ,在日本召开的学术会议上 ,AoyamaGakuin大学的J.Akimitsu教授宣布MgB2 显现超导电性 (Tc=39K) .紧接着的一系列研究工作表明 ,MgB2 属于BCS超导体 .这些发现引起了新一轮高临界温度超导研究热潮 相似文献
999.
Jrg Lambert Stephan Haiber Helmut Herzog 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):175
A new two-dimensional pulse sequence for T2* measurement of protons directly coupled to 13C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a “building block” into any direct or inverse detecting H,C correlation pulse sequence if proton spin–spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given. 相似文献
1000.
An investigation of the electrical properties of reduced ceria, CeO2?x, carried out on single crystals, shows that CeO2?x provides one of the clearest examples of hopping conduction and the small polaron mechanism. Included are conductivity and Seebeck coefficient measurements at constant x, obtained by sealing off the specimen chamber after reduction. The Seebeck coefficient is independent of temperature, suggesting that the number of carriers is constant. On the other hand, the mobility is activated, with activation energy Eh = 0.40 eV at small x and increasing to 0.52 eV at x = 0.25. The results for the mobility preexponential are consistent with the adiabatic theory of small polaron behavior. A puzzling feature of the Seebeck data as a function of x is that, for low x, the data fit the well-known Heikes formula, without a degeneracy factor of 2 for spin. Nevertheless, these data are interpreted to show that the proportion of mobile carriers decreases as x increases, presumably because of the presence of short-range ordered configurations which immobilize some carriers. 相似文献