全文获取类型
收费全文 | 536773篇 |
免费 | 4044篇 |
国内免费 | 1195篇 |
专业分类
化学 | 256480篇 |
晶体学 | 8263篇 |
力学 | 28886篇 |
综合类 | 10篇 |
数学 | 73666篇 |
物理学 | 174707篇 |
出版年
2021年 | 5080篇 |
2020年 | 5402篇 |
2019年 | 6314篇 |
2018年 | 9008篇 |
2017年 | 9292篇 |
2016年 | 12322篇 |
2015年 | 6446篇 |
2014年 | 11446篇 |
2013年 | 24046篇 |
2012年 | 19109篇 |
2011年 | 22613篇 |
2010年 | 17578篇 |
2009年 | 17858篇 |
2008年 | 21014篇 |
2007年 | 20766篇 |
2006年 | 18949篇 |
2005年 | 16486篇 |
2004年 | 15608篇 |
2003年 | 14082篇 |
2002年 | 14204篇 |
2001年 | 15636篇 |
2000年 | 11926篇 |
1999年 | 9145篇 |
1998年 | 8039篇 |
1997年 | 7723篇 |
1996年 | 7160篇 |
1995年 | 6322篇 |
1994年 | 6295篇 |
1993年 | 6178篇 |
1992年 | 6518篇 |
1991年 | 7049篇 |
1990年 | 6761篇 |
1989年 | 6696篇 |
1988年 | 6321篇 |
1987年 | 6501篇 |
1986年 | 6073篇 |
1985年 | 7391篇 |
1984年 | 7671篇 |
1983年 | 6468篇 |
1982年 | 6637篇 |
1981年 | 6212篇 |
1980年 | 6001篇 |
1979年 | 6624篇 |
1978年 | 6661篇 |
1977年 | 6806篇 |
1976年 | 6818篇 |
1975年 | 6383篇 |
1974年 | 6199篇 |
1973年 | 6383篇 |
1972年 | 4988篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
T. Yu. Gumerov A. F. Dobrynina R. A. Yusupov V. P. Barabanov 《Russian Journal of Applied Chemistry》2006,79(12):1935-1939
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants. 相似文献
152.
P. V. Dvornikov 《Russian Physics Journal》2006,49(4):392-401
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by
the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous
symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in
many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006. 相似文献
153.
154.
R. Jayakumar Y.‐S. Lee S. Nanjundan 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2865-2878
The calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)2] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Calcium‐containing poly(urethane ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI) with a mixture of Ca(HEEP)2 and poly(ethylene glycol) (PEG300 or PEG400) with di‐n‐butyltin dilaurate as a catalyst. A series of calcium‐containing PUEs of different compositions were synthesized with Ca(HEEP)2/PEG300 (or PEG400)/diisocyanate (HMDI or TDI) molar ratios of 2:2:4, 3:1:4, and 1:3:4 so that the coating properties of the PUEs could be studied. Blank PUEs without calcium‐containing ionic diols were also prepared by the reaction of PEG300 or PEG400 with HMDI or TDI. The PUEs were well characterized by Fourier transform infrared, 1H and 13C NMR, solid‐state cross‐polarity/magic‐angle‐spinning 13C NMR, viscosity, solubility, and X‐ray diffraction studies. The thermal properties of the polymers were also studied with thermogravimetric analysis and differential scanning calorimetry. The PUEs were applied as top coats on acrylic‐coated leather, and their physicomechanical properties were also studied. The coating properties of PUEs, such as the tensile strength, elongation at break, tear strength, water vapor permeability, flexing endurance, cold crack resistance, abrasion resistance, color fastness, and adhesive strength, were better than the standard values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2865–2878, 2003 相似文献
155.
A method for suppressing self-modulation in backward-wave tubes is proposed. Additional delay is introduced into the feedback
circuit, owing to which the output signal amplitude affects the electron beam current that enters into the interaction space.
Numerical simulations demonstrate that the operating current in the single-frequency oscillation mode may be increased roughly
twofold. 相似文献
156.
Salimgareeva V. N. Polevoi R. M. Kolesov S. V. Ostakhov S. S. Ponomareva V. A. Leplyanin G. V. 《Russian Journal of Applied Chemistry》2003,76(5):804-808
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied. 相似文献
157.
H. Okumura T. Takahagi N. Nagai S. Shingubara 《Journal of Polymer Science.Polymer Physics》2003,41(17):2071-2078
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003 相似文献
158.
In this paper, we find the approximate solution of a second order nonlinear partial differential equation on a simple connected region inR 2. We transfer this problem to a new problem of second order nonlinear partial differential equation on a rectangle. Then, we transformed the later one to an equivalent optimization problem. Then we consider the optimization problem as a distributed parameter system with artificial controls. Finally, by using the theory of measure, we obtain the approximate solution of the original problem. In this paper also the global error inL 1 is controlled. 相似文献
159.
A. V. Yakovlev 《Journal of Mathematical Sciences》2004,120(4):1642-1644
It is proved that a Galois extension of a field of characteristic p is completely determined by its Galois group and the endomorphism of the additive group of the group algebra that corresponds to the raising to the power p. 相似文献
160.
S. M. Saprikin 《Journal of Mathematical Sciences》2004,120(5):1752-1765
An arbitrary operator-valued function from the generalized Shur class is realized as the transfer function of a minimal optimal and minimal *-optimal dissipative scattering system with the Pontryagin state space. These results generalize Arov's results for the case of the Hilbert state space. Bibliography: 11 titles. 相似文献