全文获取类型
收费全文 | 8976篇 |
免费 | 569篇 |
国内免费 | 541篇 |
专业分类
化学 | 2863篇 |
晶体学 | 88篇 |
力学 | 190篇 |
综合类 | 21篇 |
数学 | 2302篇 |
物理学 | 4622篇 |
出版年
2023年 | 77篇 |
2022年 | 102篇 |
2021年 | 129篇 |
2020年 | 189篇 |
2019年 | 171篇 |
2018年 | 147篇 |
2017年 | 140篇 |
2016年 | 158篇 |
2015年 | 178篇 |
2014年 | 258篇 |
2013年 | 641篇 |
2012年 | 391篇 |
2011年 | 471篇 |
2010年 | 413篇 |
2009年 | 522篇 |
2008年 | 566篇 |
2007年 | 687篇 |
2006年 | 522篇 |
2005年 | 352篇 |
2004年 | 337篇 |
2003年 | 386篇 |
2002年 | 363篇 |
2001年 | 350篇 |
2000年 | 344篇 |
1999年 | 327篇 |
1998年 | 264篇 |
1997年 | 181篇 |
1996年 | 167篇 |
1995年 | 147篇 |
1994年 | 129篇 |
1993年 | 112篇 |
1992年 | 99篇 |
1991年 | 112篇 |
1990年 | 64篇 |
1989年 | 69篇 |
1988年 | 50篇 |
1987年 | 57篇 |
1986年 | 33篇 |
1985年 | 65篇 |
1984年 | 40篇 |
1983年 | 33篇 |
1982年 | 46篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 24篇 |
1976年 | 18篇 |
1974年 | 15篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
This study is the first to explore the possibility of utilizing CuCr LDH decorated on reduced graphene oxide (rGO) and graphene oxide (GO) as sonophotocatalysts for the degradation of dimethyl phthalate (DMP). CuCr LDH and its nanocomposites were successfully fabricated and characterized. Scanning electron microscopy (SEM) along with high-resolution transmission electron microscope (HRTEM) both evidenced the formation of randomly oriented nanosheet structures of CuCr LDH coupled with thin and folded sheets of GO and rGO. The impact of diverse processes on the degradation efficiency of DMP in the presence of the so-prepared catalysts was compared. Benefiting from the low bandgap and high specific surface area, the as-obtained CuCr LDH/rGO represented outstanding catalytic activity (100 %) toward 15 mg L−1 of DMP within 30 min when subjected to light and ultrasonic irradiations simultaneously. Radical quenching experiments and visual spectrophotometry using an O-phenylenediamine revealed the crucial role of hydroxyl radicals compared to holes and superoxide radicals. Overall, outcomes disclosed that CuCr LDH/rGO is a stable and proper sonophotocatalyst for environmental remediation. 相似文献
952.
The paper provides some results concerning the numerical study of the strongly transient gasdynamic processes in a pressure-wave
refrigerator (PWR). A hierarchical set of numerical models from the simplest one-dimensional to a fully three-dimensional
formulation is introduced. The computations show that one-dimensional solutions give a reasonable foundation for the understanding
of PWR operational principles but cannot satisfactorily predict the refrigeration efficiency. Good agreement with experiment
is achieved by considering two- and three-dimensional effects of gas mixing by overlap of rotating nozzles and expansion tubes.
Received
Received 14 February 1996 / Accepted 1 June 1996 相似文献
953.
Rate processes including change of phase are modelled analytically for a half-space porous substance exposed to a jump in external temperature. The model predicts, in a closed form, the pressure build-up and the rate of evaporation of volatiles from a porous matrix. It assumes two distinct regions separated by a moving interface where the change of phase takes place. One region maintains its initial concentration of volatiles while the second is devoid of volatiles. Different thermophysical properties are considered for the two regions. The model was applied for the evaporation of moisture from oil-shale. Results are given in a parametric form 相似文献
954.
提出了用以解释若干重大地质灾害的成因的地球内外动力耦合作用理论。在以往的自然灾害分类及研究中 ,常将内动力地质灾害和外动力地质灾害区分为两种类型 ,而注意两者的联系显然不够。本文则论证了在我国大部分地壳运动活跃地区内外动力耦合作用常是重大地质灾害的总体成因。 相似文献
955.
The purpose of this work is to examine the stationary motion and stability properties of stationary motion of two degree-of-freedom
noisy auto-parametric systems We shall use analytical techniques to extend the existing results to examine such multi-dimensional
nonlinear systems with noise, and in particular additive white noise. We obtain an approximation for the top Lyapunov exponent,
the exponential growth rate, of the response of the so-called single-mode stationary motion. We show analytically that the top Lyapunov exponent is positive, and for small values of noise intensity
ɛ and dissipation ɛ2 the exponent grows in proportion with ɛ2/3. 相似文献
956.
A numerical method to estimate spectral properties of nonlinear oscillators with random input is presented. The stationary system response is expanded into a trigonometric Fourier series. A set of nonlinear algebraic equations, solved by Newtons method, leads to the determination of the unknown Fourier series coefficients of single samples of the response process. For cubic polynomial nonlinearities, closed-form expressions are used to find the nonlinear terms at each step of the solution scheme. Further, a simple procedure yields an approximation of an arbitrary nonlinearity by a cubic polynomial. Power spectral density estimates for the response process are constructed by averaging the square modulus of the computed Fourier coefficients over various samples or by means of well-established smoothing techniques of spectral analysis. Two applications are presented illustrating the effectiveness of the method as compared to statistical linearization and digital Monte-Carlo simulation. 相似文献
957.
958.
Cover Picture: Robust Chemical Preservation of Digital Information on DNA in Silica with Error‐Correcting Codes (Angew. Chem. Int. Ed. 8/2015)
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
959.
Prof. Dr. Helmut Schwarz 《Angewandte Chemie (International ed. in English)》2015,54(35):10090-10100
Gas‐phase investigations of judiciously doped oxide clusters permit to address fundamental challenges related to, for example, the low‐temperature oxidation of CO or the selective conversion of hydrocarbons. Modifying the size and composition of a free cluster in a controlled way enables the modification of local charge effects and of spin states, and spectroscopic studies in combination with computational work help to identify the active site of a catalyst and to unravel mechanistic details. Also, the interplay of the support material with the reactive part of a composite catalyst cluster can be addressed. Examples will be presented demonstrating how and why the gas‐phase reactivities of heteronuclear clusters, in comparison with their homonuclear counterparts, toward small, generally rather inert molecules can be increased, decreased, or not significantly affected. 相似文献
960.
Dr. Jinshui Zhang Mingwen Zhang Lihua Lin Prof. Xinchen Wang 《Angewandte Chemie (International ed. in English)》2015,54(21):6297-6301
The chemical protonation of graphitic carbon nitride (CN) solids with strong oxidizing acids, for example HNO3, is demonstrated as an efficient pathway for the sol processing of a stable CN colloidal suspension, which can be translated into thin films by dip/disperse‐coating techniques. The unique features of CN colloids, such as the polymeric matrix and the reversible hydrogen bonding, result in the thin‐film electrodes derived from the sol solution exhibiting a high mechanical stability with improved conductivity for charge transport, and thus show a remarkably enhanced photo‐electrochemical performance. The polymer system can in principle be broadly tuned by hybridization with desired functionalities, thus paving the way for the application of CN for specific tasks, as exemplified here by coupling with carbon nanotubes. 相似文献