全文获取类型
收费全文 | 9183篇 |
免费 | 1480篇 |
国内免费 | 1522篇 |
专业分类
化学 | 5756篇 |
晶体学 | 42篇 |
力学 | 548篇 |
综合类 | 85篇 |
数学 | 1024篇 |
物理学 | 4730篇 |
出版年
2024年 | 16篇 |
2023年 | 120篇 |
2022年 | 298篇 |
2021年 | 318篇 |
2020年 | 373篇 |
2019年 | 352篇 |
2018年 | 291篇 |
2017年 | 336篇 |
2016年 | 337篇 |
2015年 | 357篇 |
2014年 | 462篇 |
2013年 | 763篇 |
2012年 | 546篇 |
2011年 | 582篇 |
2010年 | 478篇 |
2009年 | 582篇 |
2008年 | 632篇 |
2007年 | 629篇 |
2006年 | 624篇 |
2005年 | 528篇 |
2004年 | 496篇 |
2003年 | 424篇 |
2002年 | 343篇 |
2001年 | 275篇 |
2000年 | 320篇 |
1999年 | 236篇 |
1998年 | 228篇 |
1997年 | 209篇 |
1996年 | 139篇 |
1995年 | 119篇 |
1994年 | 112篇 |
1993年 | 98篇 |
1992年 | 96篇 |
1991年 | 77篇 |
1990年 | 56篇 |
1989年 | 41篇 |
1988年 | 50篇 |
1987年 | 36篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Multi-reference configuration-interaction calculations on multiply charged ions of carbon monosulfide 下载免费PDF全文
The potential energy curves for neutrals and multiply charged ions of carbon monosulfide are computed with highly correlated multi-reference configuration interaction wavefunctions.The correlations of inner-shell electrons with the scalar relativistic effects are included in the present computations.The spectroscopic constants,dissociation energies,ionization energies for ground and low-lying excited states together with corresponding electronic configurations of ions are obtained,and a good agreement between the present work and existing experiments is found.No theoretical evidence is found for the adiabatically stable CSq+(q>2) ions according to the present ab initio calculations.The calculated values for 1st-6th ionization energies are 11.25,32.66,64.82,106.25,159.75,and 224.64 eV,respectively.The kinetic energy release data of fragments are provided by the present work for further experimental comparisons. 相似文献
43.
An ultra-high vacuum(UHV) compatible electron spectrometer employing a double toroidal analyzer has been developed. It is designed to be combined with a custom-made scanning tunneling microscope(STM) to study the spatially localized electron energy spectrum on a surface. A tip–sample system composed of a piezo-driven field-emission tungsten tip and a sample of highly ordered pyrolytic graphite(HOPG) is employed to test the performance of the spectrometer.Two-dimensional images of the energy-resolved and angle-dispersed electrons backscattered from the surface of HOPG are obtained, the performance is optimized and the spectrometer is calibrated. A complete electron energy loss spectrum covering the elastic peak to the secondary electron peaks for the HOPG surface, acquired at a tip voltage of-140 V and a sample current of 0.5 pA, is presented, demonstrating the viability of the spectrometer. 相似文献
44.
《Physics letters. A》2014,378(16-17):1085-1090
The formations of n-order two-soliton bound states (TSBSs) in the Bose–Einstein condensates with spatiotemporally modulated nonlinearities are studied. Exact analytical expressions of the n-order TSBSs are derived by means of the similarity transformations. Further, the numerical simulations are carried out, consistent with the analytical results very well. The stability analysis shows that the solutions can be stable. Our results indicate that the attractive spatiotemporal inhomogeneous nonlinearities can support n-order TSBSs, which has the potential applications to the generation of matter-wave bright solitons in harmonic traps. 相似文献
45.
Uulke A. van der Heide Marc A. M. J. Zandvoort Ernst van Faassen Gijs van Ginkel Yehudi K. Levine 《Journal of fluorescence》1993,3(4):271-279
Measurements of fluorescence depolarization decays are widely used to obtain information about the molecular order and rotational dynamics of fluorescent probe molecules in membrane systems. This information is obtained by least-squares fits of the experimental data to the predictions of physical models for motion. Here we present a critical review of the ways and means of the data analysis and address the question how and why totally different models such as Brownian rotational diffusion and wobble-in-cone provide such convincing fits to the fluorescence anistropy decay curves. We show that while these models are useful for investigating the general trends in the behavior of the probe molecules, they fail to describe the underlying motional processes. We propose to remedy this situation with a model in which the probe molecules undergo fast, though restricted local motions within a slowly rotating cage in the lipid bilayer structure. The cage may be envisaged as a free volume cavity between the lipid molecules, so that its position and orientation change with the internal conformational motions of the lipid chains. This approach may be considered to be a synthesis of the wobble-in-cone and Brownian rotational diffusion models. Importantly, this compound motion model appears to provide a consistent picture of fluorescent probe behavior in both oriented lipid bilayers and lipid vesicle systems. 相似文献
46.
Viscous potential flow analysis of Kelvin-Helmholtz instability with heat and mass transfer has been studied. A dispersion relation has been obtained. Stability criterion is given by a critical value of relative velocity. It has been found that heat and mass transfer has destabilizing effect on relative velocity when lower fluid viscosity is low while it has stabilizing effect when lower fluid viscosity is high. Various graphs have been plotted for relative velocity and growth rate. In statically unstable situation viscosity has stabilizing effect while in statically stable situation it has destabilizing effect. 相似文献
47.
Solution of Dirac equation for Eckart potential and trigonometric Manning Rosen potential using asymptotic iteration method 下载免费PDF全文
The Dirac equation for Eckart potential and trigonometric Manning Rosen potential with exact spin symmetry is obtained using an asymptotic iteration method. The combination of the two potentials is substituted into the Dirac equation,then the variables are separated into radial and angular parts. The Dirac equation is solved by using an asymptotic iteration method that can reduce the second order differential equation into a differential equation with substitution variables of hypergeometry type. The relativistic energy is calculated using Matlab 2011. This study is limited to the case of spin symmetry. With the asymptotic iteration method, the energy spectra of the relativistic equations and equations of orbital quantum number l can be obtained, where both are interrelated between quantum numbers. The energy spectrum is also numerically solved using the Matlab software, where the increase in the radial quantum number nr causes the energy to decrease. The radial part and the angular part of the wave function are defined as hypergeometry functions and visualized with Matlab 2011. The results show that the disturbance of a combination of the Eckart potential and trigonometric Manning Rosen potential can change the radial part and the angular part of the wave function. 相似文献
48.
Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1∏ of 7LiH 下载免费PDF全文
The reasonable dissociation limit of the second excited singlet state
B1∏ of 7LiH molecule is obtained. The accurate dissociation energy and
equilibrium geometry of the B1\Pi state are calculated using a
symmetry-adapted-cluster configuration--interaction method in full active space. The
whole potential energy curve for the B1∏ state is obtained over the
internuclear distance ranging from about 0.10nm to 0.54nm, and has a least-square
fit to the analytic Murrell--Sorbie function form. The vertical excitation energy is
calculated from the ground state to the
B1∏ state and compared with previous theoretical results. The
equilibrium internuclear distance obtained by geometry optimization is found to be
quite different from that obtained by single-point energy scanning under the same
calculation condition. Based on the analytic potential energy function, the harmonic
frequency value of the B1∏ state is estimated. A comparison of the
theoretical calculations of dissociation energies, equilibrium interatomic distances
and the analytic potential energy function with those obtained by previous
theoretical results clearly shows that the present work is more comprehensive and in
better agreement with experiments than previous theories, thus it is an improvement
on previous theories. 相似文献
49.
利用气体放电双探针法研究了等离子体的I-V曲线中的电流I相对于电压V轴交点的不对称性,并提出2种可能的解释:一认为是由于两探针表面积不同引起的;二认为是由于探针所在处等离子体电位不等引起的.本文利用仪器的工艺误差和调换放电管电压的方法,对提出的2种可能原因分别进行验证,并指出第二种解释的合理性,并对其进行了理论分析. 相似文献
50.