全文获取类型
收费全文 | 1649篇 |
免费 | 189篇 |
国内免费 | 111篇 |
专业分类
化学 | 870篇 |
晶体学 | 4篇 |
力学 | 4篇 |
综合类 | 7篇 |
数学 | 23篇 |
物理学 | 1041篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 26篇 |
2020年 | 43篇 |
2019年 | 28篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 39篇 |
2015年 | 48篇 |
2014年 | 53篇 |
2013年 | 74篇 |
2012年 | 54篇 |
2011年 | 56篇 |
2010年 | 45篇 |
2009年 | 60篇 |
2008年 | 91篇 |
2007年 | 173篇 |
2006年 | 98篇 |
2005年 | 56篇 |
2004年 | 42篇 |
2003年 | 61篇 |
2002年 | 88篇 |
2001年 | 85篇 |
2000年 | 72篇 |
1999年 | 78篇 |
1998年 | 63篇 |
1997年 | 34篇 |
1996年 | 22篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 29篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1976年 | 16篇 |
1975年 | 24篇 |
1974年 | 8篇 |
1973年 | 11篇 |
排序方式: 共有1949条查询结果,搜索用时 15 毫秒
51.
52.
1 INTRODUCTION The interfaces between metals and oxide play a vital role in many industrial applications: hetero- geneous catalysis, microelectronics, thermal barriers, corrosion protection, metal processing and so on[1]. In catalysis, the choice of metal and oxide support is critical in order to obtain a desired reactivity and selectivity[2]. This is due in part to the inherent reac- tivity of the two components. Also the size and shape of the metal particle, which depend on the choice… 相似文献
53.
Yong Li 《Theoretical chemistry accounts》2007,117(1):163-165
We present the theoretical results for the positions and widths of the initial anticrossing between Stark manifold n and n + 1 in sodium, obtained by using the method of diagonalization in which zero-field wave functions are chosen from a kind of atomic potential model. These results can provide the quantitative information for understanding the microwave ionization process, whose rate-limiting step is probably the n to n + 1 transition performed at the first crossing between the outermost states of these two manifolds. 相似文献
54.
We have calculated the positions of the avoided level crossings between (n+2)s, np states and nd, k Stark states in the Rydberg Stark states of the potassium atom with principal quantum number n comprised between 12 and 17. We have also studied the adiabatic electric field ionization thresholds for the above Rydberg
states. Both the ionization thresholds and the positions of avoided crossings have been calculated using the recently developed
Stark-adapted quantum defect orbital (SQDO) formalism. The presently reported values appear to be in very good agreement with
the available theoretical and experimental data. 相似文献
55.
P. Goy 《International Journal of Infrared and Millimeter Waves》1982,3(2):221-234
This paper describes experimental results obtained with a packaged GaAs Schottky barrier diode in contact with a coaxial connector and placed across waveguides for bands Ka, V, E, W or F. Among the microwave sources used for calibration were 9 carcinotrons in the frequency interval 51–490 GHz. As soon as the frequency F is above the waveguide cut-off frequency, the different characteristics do not depend critically on the waveguide size for V, E, W and F bands. The video detection sensitivity, of several 100 mV/mW at 50 GHz and below, decreases as F–4 in the range 51–500 GHz. Coupling an X-band centimeter frequency via the coaxial connector and a millimeter frequency via the waveguide permits harmonic mixing in the diode. Between 36 and 490 GHz, the harmonic mixing number varies from 3 up to the very large value 40 with conversion losses from 18 to 88 dB. The minimum detectable signal in the 100 kHz band can be as low as –90 dBm at 80 GHz. A noticeable millimeter power is available at the waveguide output from injected centimeter power by harmonic generation. Starting for instance with 100 mW around 11.5 GHz, we have measured 0.1 mW at 80 GHz and 0.1 W at 230 GHz. To illustrate the possibility of creating usable millimeter and submillimeter wave without heavy equipment (such as carcinotrons or millimeter klystron) we report spectroscopic experiments in Rydberg atoms. Resonances have been observed up to 340 GHz by harmonic generation (28th harmonic) from an X-band klystron). 相似文献
56.
Pavel M. Polestshuk 《Journal of computational chemistry》2013,34(3):206-219
The approach for the integration over a region covered by zero‐flux surface is described. This approach based on the surface triangulation technique is efficiently realized in a newly developed program TWOE . The elaborated method is tested on several atomic properties including the source function. TWOE results are compared with those produced by using well‐known existing programs. Absolute errors in computed atomic properties are shown to range usually from 10?6 to 10?5 au. The demonstrative examples prove that present realization has perfect convergence of atomic properties with increasing size of angular grid and allows to obtain highly accurate data even in the most difficult cases. It is believed that the developed program can be bridgehead that allows to implement atomic partitioning of any desired molecular property with high accuracy. © 2012 Wiley Periodicals, Inc. 相似文献
57.
基于Hanbury Brown-Twiss(HBT)实验,我们借助于两个单光子计数模块,一个50/50分束器和一个快速计数卡(FastCom-P7888)研究了不同光场的二阶相干度。我们首先制备了脉冲相干光,连续相干光以及单原子发出的单光子源,并测量这几种不同光场的二阶相干度g(2)(τ)。我们通过测量俘获在磁光阱(MOT)和远失谐偶极阱(FORT)中的单原子在近共振连续激光激发下所辐射的荧光的二阶相干度,分别得到了g(2)(τ=0)=0.08和g(2)(τ=0)=0.09,借助于实验中产生的脉冲光与单原子,接下来我们将进行触发式单光子源的实验研究。 相似文献
58.
Prof. James S. M. Anderson Prof. Juan I. Rodríguez Prof. Paul W. Ayers Daniel E. Trujillo-González Dr. Andreas W. Götz Prof. Jochen Autschbach Prof. Fray L. Castillo-Alvarado Prof. Koichi Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2538-2544
The topology of the molecular electron density of benzene dithiol gold cluster complex Au4−S−C6H4−S′−Au′4 changed when relativistic corrections were made and the structure was close to a minimum of the Born–Oppenheimer energy surface. Specifically, new bond paths between hydrogen atoms on the benzene ring and gold atoms appeared, indicating that there is a favorable interaction between these atoms at the relativistic level. This is consistent with the observation that gold becomes a better electron acceptor when relativistic corrections are applied. In addition to relativistic effects, here, we establish the sensitivity of molecular topology to basis sets and convergence thresholds for geometry optimization. 相似文献
59.
Alberto Fernández-Alarcón Dr. José Manuel Guevara-Vela José Luis Casals-Sainz Dr. Aurora Costales Dr. Evelio Francisco Dr. Ángel Martín Pendás Dr. Tomás Rocha Rinza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17035-17045
The development of chemical intuition in photochemistry faces several difficulties that result from the inadequacy of the one-particle picture, the Born–Oppenheimer approximation, and other basic ideas used to build models. It is shown herein how real-space approaches can be efficiently used to gain valuable insights in photochemistry through a simple example of red and blue shift effects: the double hypso- and bathochromic shifts in the low-lying valence excited states of (H2O)2. It is demonstrated that 1) the use of these techniques allows the perturbative language used in the theory of intermolecular interactions, even in the strongly interacting short-range regime, to be maintained; 2) one and only one molecule is photoexcited in each of the addressed excited states and 3) the electrostatic interaction between the in-the-cluster molecular dipoles provides a fairly intuitive rationalisation of the observed batho- and hypsochromism. The methods exploited and illustrated herein are able to maintain the individuality and properties of the interacting entities in a molecular aggregate, and thereby they allow chemical intuition in general states, at any geometry and using a broad variety of electronic structure methods to be kept and built. 相似文献
60.