全文获取类型
收费全文 | 270386篇 |
免费 | 3629篇 |
国内免费 | 932篇 |
专业分类
化学 | 137262篇 |
晶体学 | 4194篇 |
力学 | 11771篇 |
综合类 | 6篇 |
数学 | 32200篇 |
物理学 | 89514篇 |
出版年
2020年 | 2281篇 |
2019年 | 2421篇 |
2018年 | 3221篇 |
2017年 | 3150篇 |
2016年 | 4987篇 |
2015年 | 3199篇 |
2014年 | 4894篇 |
2013年 | 11952篇 |
2012年 | 9300篇 |
2011年 | 11272篇 |
2010年 | 7943篇 |
2009年 | 7667篇 |
2008年 | 10428篇 |
2007年 | 10368篇 |
2006年 | 9783篇 |
2005年 | 8869篇 |
2004年 | 8087篇 |
2003年 | 7075篇 |
2002年 | 6872篇 |
2001年 | 7810篇 |
2000年 | 5987篇 |
1999年 | 4661篇 |
1998年 | 3946篇 |
1997年 | 3852篇 |
1996年 | 3779篇 |
1995年 | 3466篇 |
1994年 | 3423篇 |
1993年 | 3546篇 |
1992年 | 3688篇 |
1991年 | 3696篇 |
1990年 | 3452篇 |
1989年 | 3368篇 |
1988年 | 3377篇 |
1987年 | 3277篇 |
1986年 | 3098篇 |
1985年 | 4264篇 |
1984年 | 4451篇 |
1983年 | 3568篇 |
1982年 | 3794篇 |
1981年 | 3729篇 |
1980年 | 3621篇 |
1979年 | 3708篇 |
1978年 | 3795篇 |
1977年 | 3710篇 |
1976年 | 3792篇 |
1975年 | 3470篇 |
1974年 | 3484篇 |
1973年 | 3459篇 |
1972年 | 2388篇 |
1971年 | 2014篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
D. Kast A. Jungclaus K.P. Lieb M. Górska G. de Angelis P.G. Bizzeti A. Dewald C. Fahlander H. Grawe R. Peusquens M. De Poli H. Tiesler 《The European Physical Journal A - Hadrons and Nuclei》1998,3(2):115-128
In the neutron deficient isotopes 104,105In lifetimes of high spin states in the range from 0.5 ps to 600 ps have been measured in a coincidence recoil distance Doppler
shift (RDDS) experiment. By combining the Doppler shift attenuation (DSA) and RDDS methods at few μm flight distances, the
problem of delayed feeding has been avoided and very short lifetimes in the range 0.5–0.8 ps have been determined. Shell model
calculations with strong restrictions for the neutron orbitals reveal good agreement with experimental level energies and
still fair agreement for most measured B(M1) and B(E2) values.
Received: 30 June 1998 相似文献
992.
993.
Hans Grabmüller 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1991,42(5):783-805
Rotationally symmetric deformations of a flat annular elastic membrane under a gravitational force are studied, with prescribed radial stresses or horizontal displacements at the edges. The small-finitedeflection theory of Föppl-Hencky as well as a simplified version of Reissner's static first approximation theory of thin shells of revolution are applied which lead to consider a single, second-order, ordinary differential equation for the derivation of the principal stresses in the membrane. Using analytical methods, the range of those boundary data is determined for which the solutions of the differential equation are wrinkle free in the sense that both the radial and the circumferential stress components are nonnegative everywhere. 相似文献
994.
J. M. Pico C. P. Menaut J. Fernández J. L. Legido M. I. Paz Andrade 《Journal of solution chemistry》1991,20(1):115-124
Excess molar enthalpies hE at 25 and 35° C and atmospheric pressure, are reported for the binary mixtures formed by a 2-butanone and 2-pentanone with 1-chlorobutane, 1-chloropentane, 1-chlorohexane, or 1-chlorooctane. The hE values for all the mixtures are positive, increasing as the 1-chloroalkane length increases and as the ketone length decreases. Excess molar enthalpies depend slightly on the temperature. The experimental values together with those from the literature were used to calculate the interaction parameters for the Dang-Tassios version of the UNIFAC model.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990. 相似文献
995.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. E. Stronach M. Davis S. Uchida H. Takagi Y. Tokura Y. Hidaka T. Murakami E. A. Early J. T. Markert M. B. Maple C. L. Seaman 《Hyperfine Interactions》1991,63(1-4):311-317
We report muon spin relaxation/rotation measurements on sintered powder samples of Nd2−x
Ce
x
CuO4−y
and a large single crystal of Nd2CuO4−y
. We find an electronic phase diagram which is quite similar to that of hole-doped superconductors such as La2−x
Sr
x
CuO4−y
, although the doping of electrons into the system is less efficient in destroying the static moments on the copper spins.
Static magnetic order in Nd2CuO4−y
appears below about 250 K, and two spin reorientations are seen atT=75 K andT=35 K. Measurements of the magnetic field penetration depth have been unsuccessful due to the rare-earth paramagnetism of
these materials. 相似文献
996.
P. Di Martino P. Conflant M. Drache J. -P. Huvenne A. -M. Guyot-Hermann 《Journal of Thermal Analysis and Calorimetry》1997,48(3):447-458
The polymorphic forms II and III of paracetamol were obtained by melting the marketed form I. Under the melting and cooling conditions used, it was possible to obtain forms I, II and III. The recrystallization conditions and the physical properties of forms II and III were investigated by means of various techniques: thermomicroscopy, DSC analysis, infrared microspectrometry and X-ray powder diffraction at room temperature and as a function of temperature. Form III was found to be very unstable. However, its formation seems to be an important intermediate step in the preparation of form II. 相似文献
997.
The aim of this article is to define a model that describes the evolution of the yield surface during plasticity. We propose a modelisation that is completely different from the classical approach as far as conception is concerned. It consists of describing the yield surface evolution with the help of velocity. The yield function is not directly known but is obtained by integrating a differential law starting from an initial surface. A very simple evolution law is used; the complexity of the induced anisotropy is obtained by incremental accumulation. 相似文献
998.
The pion cloud renormalises the light-cone wavefunction of the nucleon which is measured in hard, exclusive photon-nucleon reactions. We discuss the leading twist contributions to high-energy exclusive reactions taking into account both the pion cloud and perturbative QCD physics. The nucleon’s electromagnetic form-factor at high Q2 is proportional to the bare nucleon probability Z and the cross-sections for hard (real at large angle or deeply virtual) Compton scattering are proportional to Z2. Our present knowledge of the pion-nucleon system is consistent with Z = 0.7 ± 0.2. If we apply just perturbative QCD to extract a light-cone wavefunction directly from these hard exclusive cross-sections, then the light-cone wavefunction that we extract measures the three valence quarks partially screened by the pion cloud of the nucleon. We discuss how this pion cloud renormalisation effect might be understood at the quark level in terms of the (in-)stability of the perturbative Dirac vacuum in low energy QCD. 相似文献
999.
This study was undertaken to investigate the sorption behavior of chromium hydroxide sol on silica type adsorbent in aqueous solution. Radioisotopic tracer method was used to assess data. This technique allowed sensitive kinetic and equilibrium measurements in both direction: sorption and desorption, which are strongly dependent on solution conditions, such as pH, ionic strength or the presence of complexing species. Total removal of sol particles could not be achieved, even under the most favorable experimental conditions (acidification). 相似文献
1000.
B. Pümpin H. Keller W. Kündig I. M. Savić J. W. Schneider H. Simmler P. Zimmermann E. Kaldis S. Rusiecki C. Rossel 《Hyperfine Interactions》1991,63(1-4):25-31
A systematic μSR study of the local magnetic field distribution in a series of oxygen deficient YBa2Cu3O
x
samples with 6.5⩽x⩽7.0 is reported. Special attention was given to perform the experiments under the same conditions, so that the oxygen content
of the measured samples was the only parameter varied. The behavior of the depolarization rate σ as a function of the oxygen
contentx was found to have strong similarities with the behavior of the critical temperatureT
c
as a function ofx. In particular, two step-like increases of σ were observed abovex=6.7 and 6.9. The temperature dependence of the normalized depolarization rate σ(T)/σ(0) is well described by the two-fluid model forx⩾6.781(1) and clearly deviates from this behavior forx⩽6.704(1). Our results are compared to those obtained by other groups. 相似文献