全文获取类型
收费全文 | 8191篇 |
免费 | 255篇 |
专业分类
化学 | 4268篇 |
晶体学 | 70篇 |
力学 | 163篇 |
数学 | 1804篇 |
物理学 | 2141篇 |
出版年
2023年 | 63篇 |
2021年 | 114篇 |
2020年 | 127篇 |
2019年 | 104篇 |
2018年 | 192篇 |
2017年 | 200篇 |
2016年 | 429篇 |
2015年 | 287篇 |
2014年 | 324篇 |
2013年 | 730篇 |
2012年 | 397篇 |
2011年 | 516篇 |
2010年 | 312篇 |
2009年 | 263篇 |
2008年 | 269篇 |
2007年 | 209篇 |
2006年 | 150篇 |
2005年 | 137篇 |
2004年 | 128篇 |
2003年 | 133篇 |
2002年 | 124篇 |
2001年 | 106篇 |
2000年 | 93篇 |
1999年 | 98篇 |
1998年 | 93篇 |
1997年 | 94篇 |
1996年 | 96篇 |
1995年 | 83篇 |
1994年 | 76篇 |
1993年 | 73篇 |
1992年 | 74篇 |
1991年 | 67篇 |
1989年 | 61篇 |
1988年 | 69篇 |
1987年 | 73篇 |
1986年 | 71篇 |
1985年 | 91篇 |
1984年 | 85篇 |
1983年 | 78篇 |
1982年 | 72篇 |
1981年 | 75篇 |
1980年 | 86篇 |
1979年 | 78篇 |
1978年 | 82篇 |
1977年 | 90篇 |
1976年 | 65篇 |
1974年 | 71篇 |
1973年 | 77篇 |
1966年 | 64篇 |
1965年 | 67篇 |
排序方式: 共有8446条查询结果,搜索用时 15 毫秒
991.
992.
J. Kozánková S. C. Mojumdar J. Chocholoušek J. Kákoš M. Balog L. Krajčová 《Journal of Thermal Analysis and Calorimetry》2005,81(1):191-196
Summary DúThe aim of this work is to prepare a porous filter composed of two porous layers: macro-porous carrier and micro-porous sodium borosilicate (NBS) glass with TiO2 additive (NBST glass), a Vycor-type glass. In the present work we prepared the macroporous support from the same material (NBST glass) as the upper microporous layer and then by sintering both parts to produce the required composite. This work introduces the results of experiments in the preparation of micro-porous filter on NBST glass base, laid on macro-porous carrier. After sintering of scrap NBST glass, porous samples were prepared to be used as carriers for micro-porous samples of phase-separated NBST glass. In other cases, the following carrier materials were used: a) frita SIMAX, b) Al2O3. The properties of the NBST glass and the changes in the glass structure with temperature were studied in order to determine the optimal sintering temperature of the prepared glasses. For the development of the sintered glasses, valuable information was obtained from heating microscopy (HM) and scanning electron microscopy (SEM) studies. The combination of the HM and SEM results with the measurements of the micro-hardness and density directed to the further study of the phase separated NBST glasses. 相似文献
993.
In this first part a straight general wave-guide with a perfectly conducting outer wall and several dielectrics, excited by an electrically generally polarized matter is considered and the electromagnetic field is determined. 相似文献
994.
We consider a model describing finitely many free Fermi gas reservoirs coupled by local interactions and prove the Green–Kubo
formulas and the Onsager reciprocity relations for heat and charge fluxes generated by temperature and chemical potential
differentials.
Submitted: September 2, 2006. Accepted: November 21, 2006. 相似文献
995.
We investigate the dynamics of anN-level system linearly coupled to a field of mass-less bosons at positive temperature. Using complex deformation techniques, we develop time-dependent perturbation theory and study spectral properties of the total Hamiltonian. We also calculate the lifetime of resonances to second order in the coupling. 相似文献
996.
The measurement and analysis of broad nuclear magnetic resonance (NMR) spectra of quasicrystals require experimental methods and theoretical interpretations different from NMR investigations of regular periodic crystals. Frequency- and field-sweep methods for recording quasicrystalline NMR spectra are described and compared with the measurement of27Al NMR spectra of icosahedral AlPdMn and decagonal AlNiCo quasicrystals. The nuclear spin interactions that determine the NMR line shape are the same for both types of the above Al-based quasicrystals, where the electric quadrupolar interaction with the broad distribution of its electric field gradient parameters predominantly determines the shape of the broad satellite “background” intensity. The essential observations are an almost isotropic27Al NMR spectrum of the icosahedral quasicrystals and a strong angular dependence of the spectrum of decagonal quasicrystals. 相似文献
997.
In an earlier paper 3 , we studied cycles in graphs that intersect all edge‐cuts of prescribed sizes. Passing to a more general setting, we examine the existence of T‐joins in grafts that intersect all edge‐cuts whose size is in a given set A ?{1,2,3}. In particular, we characterize all the contraction‐minimal grafts admitting no T‐joins that intersect all edge‐cuts of size 1 and 2. We also show that every 3‐edge‐connected graft admits a T‐join intersecting all 3‐edge‐cuts. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 64–71, 2007 相似文献
998.
An alternative approach to the study of Jordan ideals in associative algebras is considered. The same method can be used when analogous questions in graded algebras are treated. 相似文献
999.
Summary Expanding the range of stationary phases employed in capillary electrochromatography, the development of rigid cellulose-based
micro-beads, their physical-chemical modification and their use in capillary electrochromatography are described. Cellulose-based
stationary phases have been employed in the normal-phase and the reversed-phase modes.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
1000.
A. Smontara A. Bilusić Z. Jagličić A. Zorko J. Dolinšek H. Berger 《Applied magnetic resonance》2005,29(2):261-266
A strong increase of the thermal conductivity is observed at the phase transition (T
c=18.2 K) in Cu2Te2O5Cl2 single crystal. This behavior is compared with that of the spin-Peierls system NaV2O5, where a similar experimental observation has been made, and the conventional spin-Peierls system CuGeO3, where a modest kink in the thermal conductivity curve has been observed. The strong increase of the thermal conductivity
atT
c in Cu2Te2O5Cl2 could be partially attributed to the opening of the energy gap in the magnetic excitation spectrum evident from the magnetic
susceptibility measurements. However, the main reason for the anomaly of the thermal conductivity could be explained by a
strong spin-lattice coupling in this system, which what is in agreement with the preliminary X-band electron spin resonance
measurement. 相似文献