全文获取类型
收费全文 | 342588篇 |
免费 | 2031篇 |
国内免费 | 717篇 |
专业分类
化学 | 169506篇 |
晶体学 | 5259篇 |
力学 | 18358篇 |
综合类 | 27篇 |
数学 | 42718篇 |
物理学 | 109468篇 |
出版年
2020年 | 3429篇 |
2019年 | 4284篇 |
2018年 | 6290篇 |
2017年 | 6369篇 |
2016年 | 8178篇 |
2015年 | 3941篇 |
2014年 | 7198篇 |
2013年 | 14467篇 |
2012年 | 11432篇 |
2011年 | 13418篇 |
2010年 | 11117篇 |
2009年 | 11355篇 |
2008年 | 12882篇 |
2007年 | 12713篇 |
2006年 | 11279篇 |
2005年 | 9893篇 |
2004年 | 9370篇 |
2003年 | 8430篇 |
2002年 | 8562篇 |
2001年 | 9508篇 |
2000年 | 7180篇 |
1999年 | 5462篇 |
1998年 | 4879篇 |
1997年 | 4818篇 |
1996年 | 4307篇 |
1995年 | 3794篇 |
1994年 | 3850篇 |
1993年 | 3800篇 |
1992年 | 4068篇 |
1991年 | 4412篇 |
1990年 | 4296篇 |
1989年 | 4355篇 |
1988年 | 4158篇 |
1987年 | 4167篇 |
1986年 | 3906篇 |
1985年 | 4989篇 |
1984年 | 5041篇 |
1983年 | 4285篇 |
1982年 | 4354篇 |
1981年 | 4208篇 |
1980年 | 3888篇 |
1979年 | 4456篇 |
1978年 | 4576篇 |
1977年 | 4762篇 |
1976年 | 4833篇 |
1975年 | 4511篇 |
1974年 | 4385篇 |
1973年 | 4629篇 |
1972年 | 3642篇 |
1971年 | 3384篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Gabriel N. Gatica Ernst P. Stephan 《Numerical Methods for Partial Differential Equations》2002,18(1):105-128
This article deals with an expanded mixed finite element formulation, based on the Hu‐Washizu principle, for a nonlinear incompressible material in the plane. We follow our related previous works and introduce both the stress and the strain tensors as further unknowns, which yields a two‐fold saddle point operator equation as the corresponding variational formulation. A slight generalization of the classical Babu?ka‐Brezzi's theory is applied to prove unique solvability of the continuous and discrete formulations, and to derive the corresponding a priori error analysis. An extension of the well‐known PEERS space is used to define an stable associated Galerkin scheme. Finally, we provide an a posteriori error analysis based on the classical Bank‐Weiser approach. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 105–128, 2002 相似文献
92.
93.
V. A. Zayats A. N. Nikolaevskii T. A. Filippenko O. P. Kniga G. A. Tikhonova 《Russian Journal of Applied Chemistry》2006,79(10):1651-1654
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied. 相似文献
94.
95.
A theory that predicts the effect of the counterion size on the swelling and collapse of a weakly charged polyelectrolyte gel was developed. In addition to excluded-volume interactions between monomer units of the gel, the theory involves the counterion-monomer unit and counterion-counterion interactions in terms of the virial approximation. The character of interactions between different units in the system varies from repulsion to attraction depending on the type of solvent, counterion, and dielectric permittivity of the solvent. For solvents with a low permittivity, the effect of condensation of counterions resulting in the formation of ion pairs is taken into account. 相似文献
96.
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
97.
The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes. 相似文献
98.
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
99.
100.