全文获取类型
收费全文 | 158278篇 |
免费 | 1447篇 |
国内免费 | 429篇 |
专业分类
化学 | 85526篇 |
晶体学 | 2079篇 |
力学 | 6811篇 |
综合类 | 7篇 |
数学 | 16071篇 |
物理学 | 49660篇 |
出版年
2020年 | 1165篇 |
2019年 | 1231篇 |
2018年 | 1514篇 |
2017年 | 1501篇 |
2016年 | 2550篇 |
2015年 | 1629篇 |
2014年 | 2505篇 |
2013年 | 6565篇 |
2012年 | 5164篇 |
2011年 | 6536篇 |
2010年 | 4421篇 |
2009年 | 4448篇 |
2008年 | 5963篇 |
2007年 | 6035篇 |
2006年 | 5702篇 |
2005年 | 5245篇 |
2004年 | 4666篇 |
2003年 | 4065篇 |
2002年 | 4072篇 |
2001年 | 4456篇 |
2000年 | 3423篇 |
1999年 | 2647篇 |
1998年 | 2308篇 |
1997年 | 2248篇 |
1996年 | 2073篇 |
1995年 | 1989篇 |
1994年 | 1968篇 |
1993年 | 1807篇 |
1992年 | 2078篇 |
1991年 | 2195篇 |
1990年 | 1977篇 |
1989年 | 1974篇 |
1988年 | 1924篇 |
1987年 | 1813篇 |
1986年 | 1739篇 |
1985年 | 2269篇 |
1984年 | 2400篇 |
1983年 | 1970篇 |
1982年 | 2174篇 |
1981年 | 2031篇 |
1980年 | 1956篇 |
1979年 | 2092篇 |
1978年 | 2272篇 |
1977年 | 2118篇 |
1976年 | 2175篇 |
1975年 | 2096篇 |
1974年 | 2121篇 |
1973年 | 2108篇 |
1972年 | 1396篇 |
1971年 | 1244篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
V. Edon M.C. Hugon B. Agius L. Miotti C. Radtke F. Tatsch J.J. Ganem I. Trimaille I.J.R. Baumvol 《Applied Physics A: Materials Science & Processing》2006,83(2):289-293
The influence of processing parameters on the electrical characteristics of RuO2/LaAlO3/Si metal-oxide-semiconductor structures was investigated. In particular, the sputtering regime during deposition of LaAlO3 on Si and the atmosphere used in the post-deposition annealing step were addressed by determining capacitance-voltage and
gate current-voltage characteristics. These results were correlated with compositional information obtained by Rutherford
backscattering spectrometry and nuclear reaction analysis. A post-deposition annealing step in oxygen at 600 °C resulted in
better electrical characteristics of the final structure as compared to the same treatment performed in nitrogen. This result
is explained by oxygen ability to heal oxygen vacancies in the LaAlO3 film, especially at the dielectric/semiconductor interface region. A thermalized sputtering regime during deposition of LaAlO3 on Si leads to capacitors with electrical characteristics superior to those deposited in ballistic regime.
PACS 77.84.Dy; 81.15.Cd; 81.40.Gh; 73.40.Qv; 82.80.Yc 相似文献
32.
F. Iachello S. Oss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):307-314
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years.
We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century.
Received 21 November 2001 相似文献
33.
R. F. Bikbaev 《Journal of Mathematical Sciences》1991,57(3):3078-3083
Diffraction by a semitransparent screen is considered in the framework of the nonlinear Schrödinger equation. The case of a defocusing medium is investigated. The method used represents a synthesis of the method of Riemann's matrix problem and the technique of Whitham's deformations of spectral curves.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 179, pp. 23–31, 1989. 相似文献
34.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
35.
36.
37.
William F. Bowlin 《The Journal of the Operational Research Society》1987,38(2):127-135
The objective of this research is to evaluate a new methodology, data envelopment analysis (DEA), as a tool for measuring and evaluating the operational efficiency of US Air Force organizations. This study involves the application of DEA to locate possible inefficiencies in the performance of US Air Force real-property maintenance activities. Dynamic behaviour, as exhibited via window analyses, is reviewed along with static counterparts. The testing was done in close coordination with Air Force officials, who reviewed the results for accuracy, validity and relevance. We conclude that this type of efficiency analysis does have value for the Air Force, where it can serve as a guide to auditors, budget programmers, managers and others in measuring, evaluating and enhancing operational efficiency. 相似文献
38.
F. G. Gerasimato 《Journal of Mathematical Sciences》1991,57(5):3381-3383
We propose a simplified method of determining the integral characteristics of the opening of a parachute which makes it possible to compute the maximal stress on a parachute and the trajectory parameters of the motion of the load in the region of the opening of the parachute, and to determine the size of the portion of the canopy at the time of maximal stress.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 38–41. 相似文献
39.
Vijaya Gracias Alan F. Gasiecki Joel D. Moore Irini Akritopoulou-Zanze Stevan W. Djuric 《Tetrahedron letters》2006,47(50):8977-8980
A general method for the preparation of diaza-spirocycles is reported. This method used an olefin metathesis in order to construct the desired spirocyclic framework. Beginning with commercially available protected amino ketones, this strategy ultimately produced pharmacologically relevant diaza-scaffolds in an efficient and high-yielding process. 相似文献
40.
Kurenkov V. F. Zaitseva O. A. Kirdyashova G. N. 《Russian Journal of Applied Chemistry》2002,75(4):641-644
The kinetics of radical copolymerization of acrylamide with lithium, sodium, and potassium 2-acrylamido-2-methylpropanesulfonates in concentrated aqueous solutions in the presence of potassium persulfate as initiating agent at pH 9 and 50°C was studied by dilatometry. 相似文献