全文获取类型
收费全文 | 234802篇 |
免费 | 2198篇 |
国内免费 | 677篇 |
专业分类
化学 | 126453篇 |
晶体学 | 3602篇 |
力学 | 11037篇 |
综合类 | 10篇 |
数学 | 27242篇 |
物理学 | 69333篇 |
出版年
2021年 | 2379篇 |
2020年 | 2506篇 |
2019年 | 3041篇 |
2018年 | 4023篇 |
2017年 | 4038篇 |
2016年 | 5630篇 |
2015年 | 3051篇 |
2014年 | 5095篇 |
2013年 | 10281篇 |
2012年 | 8642篇 |
2011年 | 10310篇 |
2010年 | 7568篇 |
2009年 | 7607篇 |
2008年 | 9561篇 |
2007年 | 9549篇 |
2006年 | 8615篇 |
2005年 | 7702篇 |
2004年 | 7158篇 |
2003年 | 6478篇 |
2002年 | 6380篇 |
2001年 | 5987篇 |
2000年 | 4517篇 |
1999年 | 3475篇 |
1998年 | 3020篇 |
1997年 | 3097篇 |
1996年 | 3001篇 |
1995年 | 2546篇 |
1994年 | 2613篇 |
1993年 | 2485篇 |
1992年 | 2789篇 |
1991年 | 2872篇 |
1990年 | 2756篇 |
1989年 | 2830篇 |
1988年 | 2759篇 |
1987年 | 2751篇 |
1986年 | 2591篇 |
1985年 | 3375篇 |
1984年 | 3438篇 |
1983年 | 2831篇 |
1982年 | 2871篇 |
1981年 | 2839篇 |
1980年 | 2628篇 |
1979年 | 2984篇 |
1978年 | 2913篇 |
1977年 | 3095篇 |
1976年 | 3074篇 |
1975年 | 2872篇 |
1974年 | 2806篇 |
1973年 | 2916篇 |
1972年 | 2173篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
This is a review paper of basic knowledge and recent advances in the area of spatial solitons in Kerr and Kerr-like media. We consider spatial bright and dark solitons, solitons in waveguide geometries, optical bullets, vortex solitons and, briefly, dissipative cases. In our treatment, we use a Hamiltonian approach when considering stability issues. 相似文献
42.
Flowing and static gas-phase samples of HNO3 in O2 and N2 were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO2 and NO3, the concentrations of which were calculated using differential absorption cross sections. NO2 is produced predominantly by the heterogeneous decomposition of HNO3, whereas NO3 is generated in the gas phase by the thermal decomposition of N2O5, a product of the self-disproportionation of liquid HNO3. © 1993 John Wiley & Sons, Inc. 相似文献
43.
N. V. Pratsevityi 《Ukrainian Mathematical Journal》1998,50(8):1233-1241
We study the fractal properties of a convolution of two Cantor distributions. By using the method of characteristic functions,
we establish sufficient conditions for the singularity of the convolution of an arbitrary finite number of distributions of
random variables with independent s-adic digits. We disprove the hypothesis on the validity of a “singular analog” of the Jessen-Wintner theorem for anomalously
fractal distributions.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 8, pp. 1082–1088, August, 1998.
The present work was partially supported by the International Soros Program of Educational Support in Exact Sciences (grant
No. APU 061086). 相似文献
44.
The gauge compensation fields induced by the differential operators of the Stueckelberg-Schrödinger equation are discussed, as well as the relation between these fields and the standard Maxwell fields; An action is constructed and the second quantization of the fields carried out using a constraint procedure. The properties of the second quantized matter fields are discussed. 相似文献
45.
46.
A. N. Urumbaev 《Ukrainian Mathematical Journal》1997,49(2):320-326
We show that the modified method for finite-dimensional approximation of solutions of Fredholm integral equations of the first
kind presented in this paper is more economical than traditional methods for finite-dimensional approximation.
Institute of Mathematies, Ukrainian Academy of Science, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49,
No. 2, pp. 289–295, February, 1997. 相似文献
47.
H.-J. Sue E. I. Garcia-Meitin N. A. Orchard 《Journal of Polymer Science.Polymer Physics》1993,31(5):595-608
The fracture behavior of a core-shell rubber (CSR) modified epoxy is investigated using both fracture mechanics and microscopy tools. The CSR-modified epoxy is found to be toughened via numerous line-array cavitations of the CSR particles, followed by plastic flow of the epoxy matrix. The toughening effect via the above craze-like damage process is found to be as effective as that of the well-known widespread rubber cavitation/matrix shear yielding mechanisms. The conditions for triggering the craze-like damage appear to be both stress state and rubber concentration dependent. The type of rubber tougheners utilized also plays a critical role in triggering this rather unusual craze-like damage in epoxy systems. © 1993 John Wiley & Sons, Inc. 相似文献
48.
M. N. Davies 《The Journal of the Operational Research Society》1994,45(12):1363-1373
For the last ten years or so, developments in simulation software and methodology have been focused in two areas: (1) automating the model-building process; and (2) interfacing with other techniques and systems. That both academic and commercial research continues to be carried out in these areas is evidence of the continued popularity of the simulation technique. The most popular application areas where simulation modelling is used include manufacturing (engineering and process), warehousing and communications; not surprisingly, research and developments have therefore been concentrated in these areas. This paper describes the development of a simulation model generator for a different application area, that of clerical office processing of paper and documents for financial service companies. It outlines the reasons why there is a need for such a model generator and discusses the initial design requirements. The paper goes on to detail the developments and re-defined criteria required as the model generator brief changes as a result of practical applications. 相似文献
49.
50.
Khaled A. Aamer Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1109-1121
Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007 相似文献