全文获取类型
收费全文 | 20294篇 |
免费 | 3050篇 |
国内免费 | 2766篇 |
专业分类
化学 | 15599篇 |
晶体学 | 185篇 |
力学 | 393篇 |
综合类 | 108篇 |
数学 | 1034篇 |
物理学 | 4572篇 |
综合类 | 4219篇 |
出版年
2024年 | 86篇 |
2023年 | 279篇 |
2022年 | 1011篇 |
2021年 | 881篇 |
2020年 | 938篇 |
2019年 | 710篇 |
2018年 | 597篇 |
2017年 | 641篇 |
2016年 | 887篇 |
2015年 | 816篇 |
2014年 | 945篇 |
2013年 | 1589篇 |
2012年 | 1185篇 |
2011年 | 1064篇 |
2010年 | 923篇 |
2009年 | 1026篇 |
2008年 | 1136篇 |
2007年 | 1312篇 |
2006年 | 1190篇 |
2005年 | 1088篇 |
2004年 | 1042篇 |
2003年 | 984篇 |
2002年 | 756篇 |
2001年 | 646篇 |
2000年 | 647篇 |
1999年 | 594篇 |
1998年 | 521篇 |
1997年 | 429篇 |
1996年 | 338篇 |
1995年 | 341篇 |
1994年 | 295篇 |
1993年 | 212篇 |
1992年 | 199篇 |
1991年 | 132篇 |
1990年 | 123篇 |
1989年 | 111篇 |
1988年 | 92篇 |
1987年 | 52篇 |
1986年 | 46篇 |
1985年 | 55篇 |
1984年 | 36篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 27篇 |
1980年 | 29篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We give an account of the appearance and first developments of the statistical model of atoms proposed by Thomas and Fermi, focusing on the main results achieved by Fermi and his group in Rome. Particular attention is addressed to the unknown contribution to this subject by Majorana, anticipating some important results reached later by leading physicists. 相似文献
52.
Yasumitsu Matsuo Takehiko Ijichi Hironori Yamada Junko Hatori Seiichiro Ikehata 《Central European Journal of Physics》2004,2(2):357-366
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and
investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current
at around the coercive electric fieldE
c
of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET)
based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than
that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such
devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the
organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the
initial drain current ofE
G
=0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E
c
). From these results, it is suggested that the PEN-FET becomes a memory device. 相似文献
53.
Yu. N. Grigoryev I. V. Ershov 《Journal of Applied Mechanics and Technical Physics》2003,44(4):471-481
The influence of thermal excitation on a finite-amplitude vortex disturbance in a shear flow of a molecular gas is studied in a model problem. The evolution of such vortex structures is typical of both the nonlinear stage of the laminar–turbulent transition and for developed turbulence. Since the excitation level was assumed to be comparatively low, full Navier–Stokes equations for a compressible heat-conducting gas were used in calculations; nonequilibrium was taken into account by the coefficient of bulk viscosity. As the bulk viscosity increases in the range of realistic values, the disturbance-energy damping rate in a weakly compressible flow increases approximately by 10%. The increase in the Mach number enhances the effect of disturbance suppression. 相似文献
54.
A new fluorescent chemosensor with imidazole as ionophore was synthesized by the selective derivation of calixarene, which can effectively recognize Cu2+ and Zn2+ leading to different fluoroscopic behaviors in CH3OH-H2O. This system could be considered as a molecular switch. By modulating the pH of the solution, on-off-on fluorescent switching is carried out upon combinatory addition of acid, base and Cu2+. 相似文献
55.
Silane photoabsorption spectra mear the Si 2p thresholds:the geometry of Si 2p excited SiH4
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Based on the multiple-scattering self-consistent-field method, we have studied the photoabsorption spectra near the Si 2p thresholds of silane. According to our calculations, the clear assignments of the inner-shell photoabsorption spectra are provided. In comparison with the high-resolution experimental spectra, the geometric structure of the Si 2p-excited SiH_{4}^{**} is recommended to be of a C_{2v} symmetry. More specifically, the Si 2p-excited SiH_{4}^{**} have two bond lengths of 2.50 a.u. and another two bond lengths of 2.77 a.u., and the corresponding two bond angles are 104.0° and 112.5° respectively. 相似文献
56.
Idealization of a decomposition theorem 总被引:1,自引:1,他引:0
In 1986, Tong [13] proved that a function f : (X,τ)→(Y,φ) is continuous if and only if it is α-continuous and A-continuous. We extend this decomposition of continuity in terms of ideals. First, we introduce the notions of regular-I-closed sets, A
I-sets and A
I -continuous functions in ideal topological spaces and investigate their properties. Then, we show that a function f : (X,τ,I)→(Y, φ) is continuous if and only if it is α-I-continuous and A
I-continuous.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
57.
氢键分子系统的二分量孤子偶模型中的非谐特性 总被引:1,自引:1,他引:0
成元发 《湖北大学学报(自然科学版)》2002,24(1):33-37
以氢键分子系统中二分量孤子模型为基础,采用直接微扰方法,研究了氢键系统中非谐相互作用下扭结孤子偶的运动特性,获得了3次方到4闪方非谐项古孤子偶的非对称解,计算了源于非谐项下孤子偶的能量,与实验观察相一致。 相似文献
58.
C. Baumgarten B. Braun G. Court G. Ciullo P. Ferretti G. Graw W. Haeberli M. Henoch R. Hertenberger N. Koch H. Kolster P. Lenisa A. Nass S.P. Pod'yachev D. Reggiani K. Rith M.C. Simani E. Steffens J. Stewart T. Wise 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):37-49
The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage
rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of
the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target
gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion
process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation.
Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically.
These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally
it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow
one to determine the possible range of the corresponding density weighted average values along the tube. The calculations
are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target.
Received 9 July 2001 and Received in final form 18 September 2001 相似文献
59.
借助于分子拓扑学探讨了脂肪腈的凝聚型性能与分子结构之间的关系,提出一个结构基础明确的定量关系式.对乙腈到二十一烷腈的计算结果表明,沸点、密度和折光指数的计算值都很接近实验值.应用这一定量关系,不仅能够合理表征脂肪睛结构与凝聚型性能的关系,而且有助于揭示物质结构与性能关系之间的奥秘。 相似文献
60.
阐述了紫外无机非线性光学晶体分子工程学探索方法的基本特点,具体分析深紫外无机非线性光学晶体硼铍酸锶(SBBO)以氟硼铍酸钾(KBBF)为主要参考晶体的分子设计方法,随后根据晶体结构研究、单晶培养、和非线性光学性能测定等实验结果讨论SBBO作为新型深紫外无机晶体的主要优点,即它既具有更短的紫外吸收边(接近155nm)和较大的非线性光学系数(d22(SBBO)=06×d22(BBO)=138pm/V),同时晶体无明显层状习性,并肯有良好的化学稳定性和机械性能 相似文献