全文获取类型
收费全文 | 27865篇 |
免费 | 6039篇 |
国内免费 | 2206篇 |
专业分类
化学 | 19768篇 |
晶体学 | 379篇 |
力学 | 230篇 |
综合类 | 142篇 |
数学 | 934篇 |
物理学 | 14657篇 |
出版年
2024年 | 54篇 |
2023年 | 422篇 |
2022年 | 695篇 |
2021年 | 1166篇 |
2020年 | 1303篇 |
2019年 | 1118篇 |
2018年 | 891篇 |
2017年 | 855篇 |
2016年 | 1525篇 |
2015年 | 1458篇 |
2014年 | 1592篇 |
2013年 | 2306篇 |
2012年 | 1715篇 |
2011年 | 1870篇 |
2010年 | 1559篇 |
2009年 | 1687篇 |
2008年 | 1860篇 |
2007年 | 2040篇 |
2006年 | 1901篇 |
2005年 | 1528篇 |
2004年 | 1383篇 |
2003年 | 1266篇 |
2002年 | 946篇 |
2001年 | 761篇 |
2000年 | 750篇 |
1999年 | 601篇 |
1998年 | 566篇 |
1997年 | 432篇 |
1996年 | 317篇 |
1995年 | 257篇 |
1994年 | 214篇 |
1993年 | 156篇 |
1992年 | 161篇 |
1991年 | 104篇 |
1990年 | 102篇 |
1989年 | 96篇 |
1988年 | 62篇 |
1987年 | 59篇 |
1986年 | 63篇 |
1985年 | 53篇 |
1984年 | 43篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 17篇 |
1979年 | 11篇 |
1978年 | 21篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 644 毫秒
71.
Dimitar I. Pushkarov 《Central European Journal of Physics》2004,2(3):420-455
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon
are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they
turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but
by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation
formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison
with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan
theory is shown. 相似文献
72.
We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field.
Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the
static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge
radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers. 相似文献
73.
Teresa uczak Radosaw Pankiewicz Bogusawa ska Grzegorz Schroeder Maria Betowska-Brzezinska Bogumil Brzezinski 《Journal of Molecular Structure》2006,800(1-3):140-145
Novel self-assembled monolayers were obtained on silver using 4,7-diazaheptyl-trimethoxy-silane (SiN) and vinyl-trialkoxy-silane (SiVA, where the alkyl group is 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60-eicozaoxa- hexaheptaconan). It was shown that thus modified metal surface was protected against electrooxidation. A densely packed monolayer remained stable and did not desorb from the Ag electrode on the potential cycling. The structure of SiN and SiVA as well as their complexes with Li+ cations were calculated and visualised by the AM1d and PM5 semi-empirical methods. 相似文献
74.
Molecular electroactive monolayers have been produced from vinylferrocene (VFC) via light-assisted surface anchoring to H-terminated n- and p-Si(1 0 0) wafers prepared via wet chemistry, in a controlled atmosphere. The resulting Si-C bound hybrids have been characterized by means of XPS and AFM. Their performance as semiconductor functionalized electrodes and their surface composition have been followed by combining electrochemical and XPS measurements on the same samples, before and after use in an electrochemical cell. White-light photoactivated anchoring at short (1 h) exposure times has resulted in a mild route, with a very limited impact on the initial quality of the silicon substrate. In fact, the functionalized Si surface results negligibly oxidized, and the C/Fe atomic ratio is close to the value expected for the pure molecular species. The VFC/Si hybrids can be described as (η5-C5H5)Fe2+(η5-C5H4)-CH2-CH2-Si species, on the basis of XPS results. Electrochemical methods have been applied in order to investigate the role played by a robust, covalent Si-C anchoring mode towards substrate-molecule electronic communication, a crucial issue for a perspective development of molecular electronics devices. The response found from cyclic voltammograms for p-Si(1 0 0) functionalized electrodes, run in the dark and under illumination, has shown that the electron transfer is not limited by the number of charge carriers, confirming the occurrence of electron transfer via the Si valence band. The hybrids have shown a noticeable electrochemical stability and reversibility under cyclic voltammetry (cv), and the trend in peak current intensity vs. the scan rate was linear. The molecule-Si bond is preserved even after thousands of voltammetric cycles, although the surface coverage, evaluated from cv and XPS, decreases in the same sequence. An increasingly larger surface concentration of Fe3+ at the expenses of Fe2+ redox centers has been found at increasing number of cv’s, experimentally associated with the growth of silicon oxide. Surface SiO− groups from deprotonated silanol termination, induced by the electrochemical treatments, are proposed as the associated counterions for the Fe3+ species. They could be responsible for the observed decrease in the electron transfer rate constant with electrode ageing. 相似文献
75.
We propose a unified method for deducing recursive relations for the canonical partition function of a system of noninteracting particles with charge conservation if the particles follow the Bose–Einstein, Fermi–Dirac, or Maxwell–Boltzmann statistics or parastatistics. For all these types of statistics, we find recursive relations for the partition function of a new statistical model of nuclear multifragmentation with electric charge and baryon number conservation, accounting for the internal degrees of freedom of the nuclear fragments. 相似文献
76.
陈海珍 《宁波大学学报(理工版)》2004,17(4):444-448
选用了钛酸丁酯、硬脂酸和乙二醇作为表面活性剂,采用表面化学修饰和表面物理修饰2种方法修饰纳米氧化钛,然后分散在乙二醇溶剂中形成溶胶溶液.并通过红外光谱仪、紫外分光计、原子力显微镜,分析了表面化学修饰后的纳米氧化钛表面化学结构的变化,观测了纳米氧化钛溶胶在乙二醇溶剂中稳定性.试验结果表明表面活性剂与纳米氧化钛的表面的不饱和键之间形成了新的化学结构,粒子表面可能接枝上有机长链,提高了纳米粒子在溶剂中的相容性.表面化学修饰后的纳米氧化钛与乙二醇溶剂形成了较稳定的溶胶体系,而且纳米溶胶粒径较小.表面活性剂添加量与纳米粒子添加量控制在(1~1.2):1时,可以获得纳米溶胶粒径较小,同时溶胶稳定性较好的纳米氧化钛-乙二醇溶胶体系. 相似文献
77.
E. L. Kristallovich A. G. Eshimbetov N. D. Chuvylkin L. I. Belen'kii Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2003,39(5):495-500
The principal types of electronic transitions in absorption spectra of deoxyvasicinone and its 6-amino- and 6-nitro-derivatives were determined by analyzing the electron-density distributions in excited states calculated using ZINDO/S. 相似文献
78.
Andrey Pereverzev 《Foundations of Physics Letters》2003,16(5):411-428
We argue that it may be possible to consistently explain the quantum measurement by assuming that the wave function is in one-to-one correspondence with objective physical reality and has no probabilistic interpretation. In the context of such approach we consider the model of a harmonic oscillator linearly coupled to a heat bath and treat the oscillator as the system being measured. Three classes of initial pure states for the bath are considered. Exact expressions for the average values and variances of the oscillator coordinate and momentum as functions of time are considered for each class of pure states. It is shown that these quantities exhibit different asymptotic behavior for different classes of initial states of the bath. In particular, if each mode of the bath is initially in a coherent state, then for an arbitrary initial state of the oscillator the variances of the oscillator coordinate and momentum asymptotically approach the same values as for a coherent state of the free oscillator, while the averages of coordinate and momentum show a Brownian-like behavior. We argue that such behavior shows several features of the quantum measurement and supports our interpretation of the wave function. 相似文献
79.
V. I. Sakharov 《Fluid Dynamics》2007,42(6):1007-1016
The results of numerical simulation are presented for thermally and chemically nonequilibrium air plasma flows in a plasmatron discharge channel and underexpanded dissociated and partially ionized air jets flowing past a cylindrical model with a blunt leading edge and cooled copper surface under the experimental conditions realized in a VGU-4 100 kW induction plasmatron (Institute for Problems in Mechanics of the Russian Academy of Sciences) (see, for example, [1, 2]). The nonequilibrium excitation of the vibrational degrees of freedom of the molecules in the modal approximation and the difference between the electron and translational heavy-particle temperatures are taken into account in the calculations. The calculated data on the heat transfer and pressure at the stagnation point are compared with the results obtained within the framework of the thermally equilibrium model. Comparison with the experimental data obtained in the Institute for Problem in Mechanics of the Russian Academy of Sciences (Laboratory for interaction between plasma and radiation and materials) and kindly provided for comparison purposes gives satisfactory agreement. 相似文献
80.
E. Rodriguez E. Jimenez G.J. Jacob A.A.R. Neves C.L. Cesar L.C. Barbosa 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):361
Multilayer PbTe quantum dots (QDs) and SiO2 were grown by pulsed laser deposition (PLD) and Plasma enhanced chemical vapor deposition (PECVD) techniques. The crystalline structure, QD size and size dispersion were observed by high-resolution transmission electron microscopy (HRTEM) measurements. This technique allows one to grow PbTe QDs as small as 1.8 nm diameter and 0.6 nm size dispersion. The whole structure can be used in a Fabry–Perot cavity for an optical device operating at the mid-infrared region. 相似文献