全文获取类型
收费全文 | 41809篇 |
免费 | 5378篇 |
国内免费 | 4445篇 |
专业分类
化学 | 12759篇 |
晶体学 | 964篇 |
力学 | 9625篇 |
综合类 | 573篇 |
数学 | 14707篇 |
物理学 | 13004篇 |
出版年
2024年 | 74篇 |
2023年 | 435篇 |
2022年 | 685篇 |
2021年 | 943篇 |
2020年 | 1207篇 |
2019年 | 1037篇 |
2018年 | 1070篇 |
2017年 | 1478篇 |
2016年 | 1710篇 |
2015年 | 1305篇 |
2014年 | 2130篇 |
2013年 | 3070篇 |
2012年 | 2564篇 |
2011年 | 2927篇 |
2010年 | 2476篇 |
2009年 | 2755篇 |
2008年 | 2680篇 |
2007年 | 2681篇 |
2006年 | 2449篇 |
2005年 | 2281篇 |
2004年 | 1963篇 |
2003年 | 1773篇 |
2002年 | 1582篇 |
2001年 | 1327篇 |
2000年 | 1233篇 |
1999年 | 1120篇 |
1998年 | 1031篇 |
1997年 | 892篇 |
1996年 | 746篇 |
1995年 | 634篇 |
1994年 | 586篇 |
1993年 | 463篇 |
1992年 | 476篇 |
1991年 | 361篇 |
1990年 | 278篇 |
1989年 | 213篇 |
1988年 | 186篇 |
1987年 | 131篇 |
1986年 | 88篇 |
1985年 | 115篇 |
1984年 | 108篇 |
1983年 | 53篇 |
1982年 | 71篇 |
1981年 | 50篇 |
1980年 | 26篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 37篇 |
1976年 | 13篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Svitlana P. Rogovchenko 《Journal of Mathematical Analysis and Applications》2003,279(1):121-134
In this paper, we are concerned with a class of nonlinear second-order differential equations with a nonlinear damping term. Passage to more general class of equations allows us to remove a restrictive condition usually imposed on the nonlinearity, and, as a consequence, our results apply to wider classes of nonlinear differential equations. Two illustrative examples are considered. 相似文献
102.
103.
Monika Goikoetxea María J. Barandiaran José M. Asua 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5838-5846
The mechanisms involved in the formation of n‐butanol during the synthesis of butyl acrylate containing latices were investigated. The experimental results showed that neither the hydrolysis of butyl acrylate nor of the ester bond in the butyl acrylate segments of the polymer played a major role in the formation of n‐butanol, which was mainly generated from the polymer backbone, by transfer reactions to polymer chain followed by cyclization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5838–5846, 2007 相似文献
104.
Hana Macková Daniela Králová Daniel Horák 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5884-5898
The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe2O3 nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe2O3, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe2O3 nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007 相似文献
105.
106.
线性规划联合算法的理论与应用 总被引:6,自引:4,他引:2
本在[1]的基础上.较系统的叙述了线性规划联合算法的步骤、相关理论及其应用,指出该算法具有避免人工变量、减少迭代次数、使用灵活、应用方便等特点。 相似文献
107.
108.
109.
The numerical prediction of the fields of inelastic strains (the linear invariant of the tensor of inelastic strains) in thermoset polyester/marble filler composite plates is discussed. A uniformly distributed load is applied to the plates, which lie on a steel base. The strain fields are predicted by means of the boundary element method by using creep test data for the composites and the polyester matrix itself. Identical creep tests were performed for two ages of the materials (1 month and 13 years), which allowed evaluating the aging effect. The study is carried out in two stages. At the first stage, the application of the generalized Maxwell-Gurevich equation to the thermoset matrix/mineral filler composite is demonstrated. The model parameters determined from the experimental creep data is used for the second stage, where the state of inelastic strains in the plates is predicted by applying the boundary element method. The influence of composite formulation (filler content) and physical aging of the polyester matrix on the state of inelastic strains in the plates is shown.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 145–156, March–April, 2005. 相似文献
110.
本文提出的MMD算法用于提高模型区别错误信息和正确信息的能力.利用该算法在对模型的参数进行重估计时.涉及到复杂的目标函数的梯度运算.击运用矩阵运算使得梯度运算变得简单明了,因此本文给出了MMD算法下的HMM参数重估计的矩阵表示形式并给出了证明. 相似文献