全文获取类型
收费全文 | 346篇 |
免费 | 9篇 |
国内免费 | 9篇 |
专业分类
化学 | 157篇 |
晶体学 | 2篇 |
力学 | 14篇 |
数学 | 136篇 |
物理学 | 55篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 29篇 |
2011年 | 23篇 |
2010年 | 27篇 |
2009年 | 15篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 4篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1908年 | 2篇 |
1906年 | 1篇 |
排序方式: 共有364条查询结果,搜索用时 156 毫秒
91.
Emre Alkan Florin Stan Alexandru Zaharescu 《Proceedings of the American Mathematical Society》2006,134(10):2807-2815
Generalizing a classical problem of Lehmer, in this paper we provide an asymptotic result for the number of Lehmer -tuples.
92.
A CE protocol was developed for the identification and separation of inorganic polysulfides simultaneously with other inorganic sulfur-bearing species coexisting in aqueous hydrosulfide/sulfur solutions. The electrophoretic separation of thiosulfate, sulfate, hydrosulfide, sulfite, tetrathionate, and polysulfides was achieved at pH values between 8.2 and 12.2. The peaks attributed to the polysulfide species were strongly sensitive to pH. CE analysis of hydrosulfide/sulfur solutions at different pH values permitted possible identification of two forms of polysulfides: S4(2-) and S3(2-). Upon exposure to air at ambient temperature, thiosulfate was the main oxidation product of hydrosulfide/sulfur solutions mainly in the first 60 min, when hydrosulfide was rapidly consumed. Analysis of the oxidation reaction products provided retrospectively tentative evidence that the peaks separated and identified as tri- and tetrasulfide may be ascribed to polysulfides. 相似文献
93.
The connection between geodesics on the modular surface and regular continued fractions, established by Series, is extended to a connection between geodesics on
and odd and grotesque continued fractions, where is the index two subgroup of generated by the order three elements and , and having an ideal quadrilateral as fundamental domain.A similar connection between geodesics on
and even continued fractions is discussed in our framework, where denotes the Theta subgroup of generated by and . 相似文献
94.
A fluid-structure mathematical model usually includes parameters whose actual values are known only approximately or can vary around some reference values. The objective of the sensitivity analysis is to determine quantitatively the behavior of the responses of a fluid-structure system locally around a chosen point of the trajectory in the phase-space of parameters and dependent variables. In this work, the response considered is the total mechanical energy of the structure. The sensitivities with respect to all the parameters the fluid-structure system depends on are useful in many situations as well as for optimization purposes. We present the theoretical developments necessary for the application of the adjoint sensitivity analysis methods (ASAM) for the fully coupled governing equations of an aeroelastic system. The algorithm is general and can be applied for any kind of fluid-structure interaction problems. Illustrative numerical examples are presented for the case of typical section with two degrees of freedom. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
95.
Florin A. Radu Iuliu Sorin Pop Sabine Attinger 《Numerical Methods for Partial Differential Equations》2010,26(2):320-344
In this article, we analyze an Euler implicit‐mixed finite element scheme for a porous media solute transport model. The transporting flux is not assumed given, but obtained by solving numerically the Richards equation, a model for subsurface fluid flow. We prove the convergence of the scheme by estimating the error in terms of the discretization parameters. In doing so we take into account the numerical error occurring in the approximation of the fluid flow. The article, is concluded by numerical experiments, which are in good agreement with the theoretical estimates. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010 相似文献
96.
For a vector \(\mathbf a = (a_1,\ldots ,a_r)\) of positive integers, we prove formulas for the restricted partition function \(p_{\mathbf a}(n): = \) the number of integer solutions \((x_1,\dots ,x_r)\) to \(\sum _{j=1}^r a_jx_j=n\) with \(x_1\ge 0, \ldots , x_r\ge 0\) and its polynomial part. 相似文献
97.
Jürgen Brem Csaba Paizs Monica Ioana Toşa Elemér Vass Florin Dan Irimie 《Tetrahedron: Asymmetry》2009,20(4):489-496
Starting from the racemic 3-benzofuranyl- and 3-benzo[b]thiophenyl-3-hydroxypropanoic acid ethyl esters as substrates, various multistep enzymatic procedures were developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids. 相似文献
98.
99.
A molecule undergoing reaction may form a short-lived intermediate. Under certain conditions, the rate at which the reaction proceeds toward the product state via the intermediate may exceed that of a simple, direct path. The competition of two alternative reactive pathways is analyzed here in terms of a stochastic model. The approach allows one to diagnose this competition as a function of the energy of the intermediate relative to the barrier heights of the potential surface and values of the reactive vibrational modes. The result has applications to a variety of problems in chemical physics, ranging from the "lock-and-key" mechanism for the enzymatic activity to control of temporal evolution of complex systems by optimal laser fields. 相似文献
100.
Trimetazidine and internal standard [1-(2,4,5-trimethoxybenzyl)piperazine] were isolated from plasma by protein precipitation with trifluoroacetic acid. The neutralized supernatant was separated on a C(8) column with methanol-aqueous 0.11% triethylamine adjusted to pH 3.3 with formic acid (1:4, v/v) at a flow rate of 0.85 mL/min. The separation was achieved within 8 min and the column ef fluent was transferred into an ion trap analyzer via an atmospheric pressure chemical ionization interface. The mass analyzer was used in the selected reaction monitoring mode, to enhance detection selectivity. The method was fully validated with a quantitation limit for trimetazidine of 1.5 ng/mL. The method was successfully applied to assess bioequivalence of two immediate and two modified commercially available pharmaceutical formulations containing 20 and 35 mg of trimetazidine, respectively. 相似文献