全文获取类型
收费全文 | 2644篇 |
免费 | 70篇 |
国内免费 | 2篇 |
专业分类
化学 | 1325篇 |
晶体学 | 18篇 |
力学 | 79篇 |
综合类 | 3篇 |
数学 | 527篇 |
物理学 | 764篇 |
出版年
2022年 | 18篇 |
2021年 | 33篇 |
2020年 | 51篇 |
2019年 | 39篇 |
2018年 | 85篇 |
2017年 | 75篇 |
2016年 | 110篇 |
2015年 | 60篇 |
2014年 | 106篇 |
2013年 | 207篇 |
2012年 | 126篇 |
2011年 | 148篇 |
2010年 | 98篇 |
2009年 | 102篇 |
2008年 | 94篇 |
2007年 | 91篇 |
2006年 | 69篇 |
2005年 | 49篇 |
2004年 | 38篇 |
2003年 | 36篇 |
2002年 | 60篇 |
2001年 | 43篇 |
2000年 | 43篇 |
1999年 | 31篇 |
1998年 | 45篇 |
1997年 | 34篇 |
1996年 | 29篇 |
1994年 | 25篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1983年 | 24篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 30篇 |
1979年 | 20篇 |
1978年 | 34篇 |
1977年 | 35篇 |
1976年 | 40篇 |
1975年 | 31篇 |
1974年 | 29篇 |
1971年 | 19篇 |
1969年 | 19篇 |
1968年 | 24篇 |
1966年 | 21篇 |
排序方式: 共有2716条查询结果,搜索用时 15 毫秒
121.
The influence of the flashlamp pump current pulse shape on Er:YAG laser efficiency and laser rod thermal focusing was studied theoretically and experimentally. Two pulse shapes, PFN (Pulse Forming Network) and VSP (Variable Square Pulse), were considered. Theoretical modeling and experimental measurements show that the pump pulse shape itself does not have a significant influence on the Er:YAG laser efficiency or thermal focusing. Instead, the major parameter influencing Er:YAG laser efficiency and thermal focusing was found to be the overall pulse duration. For PFN pulses, rise and fall times directly define the overall pulse duration, and therefore do have influence on thermal focusing. By contrast, VSP pulse duration is defined by the externally controlled on-time of the switching transistor. For square shaped pulses, short rise and fall times do not have a direct beneficial influence on thermal lensing. 相似文献
122.
M. Hannoun N. Blažević D. Kolbah F. Kajfež 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):125-126
Abstract Bis(trimethylsilyl)peroxide (BSPO) can be used for chemo- and stereoselective generation of P=O group by oxygenation of P(III) centre and transformation of P=S and P=Se groups. 相似文献
123.
Active-to-absorbing phase transition subjected to the velocity fluctuations in the frozen limit case
N. V. Antonov M. Hnatich A. S. Kapustin T. Lučivjanský L. Mižišin 《Physics of Particles and Nuclei Letters》2017,14(6):944-952
The directed bond percolation process is studied in the presence of compressible velocity fluctuations with long-range correlations. We discuss a construction of a field theoretic action and a way of obtaining its large scale properties using the perturbative renormalization group. The most interesting results for the frozen velocity limit are given. 相似文献
124.
In the present paper, a new approach was developed for solving the problem of time synchronization of a set of signals obtained by different measurement techniques without a common trigger. The recorded signals were the result of sparks and bursts generated by a repetitive Marx generator. A thermal imaging camera, a high speed camera and an audio recorder were used to obtain the necessary data for synchronization and characterization. Moreover, a piezoelectric sensor was applied for shock waves characterization during the early stages of bursts. In the first place, different data with evident time shifts were acquired. Then, A set of simple operations such as maximum selection and localization, threshold comparison, Euclidean distance calculation and minimization were employed for signal analysis and pattern matching to ensure a good data synchronization, which allowed a detailed analysis of the phenomenon in the end. 相似文献
125.
A. A. Naberezhnov P. Yu. Vanina A. A. Sysoeva A. Ciźman E. Rysiakiewicz-Pasek A. Hoser 《Physics of the Solid State》2018,60(3):442-446
The effect of restricted geometry and thermal prehistory of sample preparation on phase transitions in nanocomposites on base of porous glasses with average pore diameters 7 and 46 nm filled by potassium nitrate have been studied by X-rays and neutron diffraction. The nanoparticle sizes have been determined and phase diagrams (on cooling) for these nanoparticles have been described. It is shown that there is a critical nanoparticle size in the interval from 30 till 20 nm, at which in nanocomposite the ferroelectric phase is realized only regardless of preparation method. 相似文献
126.
V. I. Petrenko M. V. Avdeev V. M. Garamus M. Kubovcikova Z. Gažová K. Šipošová L. A. Bulavin L. Almásy V. L. Aksenov P. Kopcansky 《Physics of the Solid State》2014,56(1):129-133
The structure of filament amyloid aggregates of hen egg white lysozyme in water has been investigated by the small-angle X-ray scattering method. The experimental data are described by different cylindrical models, among which the best agreement is reached with the long helix model. A comparison of the results with the small-angle neutron scattering data reveals the influence of the heavy component of the solvent (a H2O/D2O mixture) on the structure of the filaments. 相似文献
127.
Barbora Benešová Martin Kružík Gabriel Pathó 《Continuum Mechanics and Thermodynamics》2014,26(5):683-713
We design a new mesoscopic thin-film model for shape-memory materials which takes into account thermomechanical effects. Starting from a microscopic thermodynamical bulk model, we guide the reader through a suitable dimension reduction procedure followed by a scale transition valid for specimen large in area up to a limiting model which describes microstructure by means of parametrized measures. All our models obey the second law of thermodynamics and possess suitable weak solutions. This is shown for the resulting thin-film models by making the procedure described above mathematically rigorous. The main emphasis is, thus, put on modeling and mathematical treatment of joint interactions of mechanical and thermal effects accompanying phase transitions and on reduction in specimen dimensions and transition of material scales. 相似文献
128.
129.
Vladislava Mičková Silvia Ružičková Dagmar Remeteiová Martina Laubertová Marianna Dorková 《Chemical Papers》2018,72(5):1231-1238
Sampling is the most important procedure in arriving at the value of an electronic scrap. Inappropriate sampling makes other procedures, including assaying, valueless, as the sample must really represent the electronic scrap from which it was taken. The aim of this study was to develop the procedure to investigate the composition of heterogeneous printed circuit boards (PCBs) material and to show its applicability as well as its related limitations. The contents of Cu, Pb, Ni, and Zn in PCBs from wasted mobile phones were determined. Mixtures of aqua regia, hydrogen peroxide and hydrofluoric acid were applied to sample digestion. Open and closed vessel wet digestion with or without heating and microwave-assisted one was realized. For these purposes different sample amounts (0.2, 0.4, and 0.5 g) were applied and on the basis of calculated relative standard deviation values (RSD), the precision of repeated the most effective digestion was evaluated. The microwave-assisted wet digestion and mixture of aqua regia and hydrogen peroxide was found as the most effective one of the compared mixtures and applied conditions. A sample amount of 0.5 g was found as the most suitable. RSD values confirm the importance of electronic waste material sample preparation. 相似文献
130.