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111.
We examine a single machine scheduling problem with random processing times and deadline. Given a set of independent jobs having specified initiation costs and terminal revenues, the objective is to select a subset of the jobs and sequence the selected jobs such that the expected profit is maximized. The job selection aspect considered by us marks a clear departure from the pure sequencing focus found in the traditional scheduling literature. In this paper, we assume an exponentially distributed deadline and do not allow preemption. Even under these conditions, the selection and sequencing problem remains quite difficult (unlike its pure sequencing counterpart); we in fact conjecture that the problem is NP-hard. However, we show that the problem can be efficiently solved as long as the cost parameter is agreeable or an approximate solution is acceptable. To this end, we describe several solution properties, present dynamic programming algorithms (one of which exhibits a pseudo-polynomial time worst-case complexity), and propose a fully-polynomial time approximation scheme. In addition, we study a number of special cases which can be solved in polynomial time. Finally, we summarize our work and discuss an extension where the jobs are precedence related. 相似文献
112.
以1.06μm激光为基频光,测量了金、铜、铂、银膜的反射二次谐波随基频光偏振角的变化,在b=-1的条件下拟合求得了这几种样品面谐波电流的唯象参数“a”值。 相似文献
113.
114.
本文用“稳健设计”的观点,分别对OTL电路中点电压稳定性“系统择优”,“参数择优”及“容差择优”作出较为系统的介绍 相似文献
115.
It is shown that the parameters in a two-dimensional (depth-averaged) numerical tidal model can be estimated accurately by assimilation of data from tide gauges. The tidal model considered is a semi-linearized one in which kinematical non-linearities are neglected but non-linear bottom friction is included. The parameters to be estimated (bottom friction coefficient and water depth) are assumed to be position-dependent and are approximated by piecewise linear interpolations between certain nodal values. The numerical scheme consists of a two-level leapfrog method. The adjoint scheme is constructed on the assumption that a certain norm of the difference between computed and observed elevations at the tide gauges should be minimized. It is shown that a satisfactory numerical minimization can be completed using either the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton algorithm or Nash's truncated Newton algorithm. On the basis of a number of test problems, it is shown that very effective estimation of the nodal values of the parameters can be achieved provided the number of data stations is sufficiently large in relation to the number of nodes. 相似文献
116.
R. N. Bergman R. E. Kalaba K. Spingarn 《Journal of Optimization Theory and Applications》1976,20(1):47-63
A glucose tolerance test was performed on dogs by injecting glucose intravenously and measuring the plasma glucose and insulin concentrations versus time. Various analytical and computational techniques were utilized to fit the data to a minimal model and to estimate the parameters of the blood glucose regulation process. A relatively good fit was obtained in spite of the rather simple model.Animal experiments were funded by the National Institute of Health Grant No. AM-17236 awarded to Dr. R. N. Bergman at U.S.C. 相似文献
117.
It is shown that the eddy viscosity profile in a quasi-three-dimensional numerical tidal and storm surge model can be estimated by assimilation of velocity data from one or more current meters located on the same vertical line. The computational model used is a simplified version of the so-called vertical/horizontal splitting algorithm proposed by Lardner and Cekirge. We have estimated eddy viscosity both as a constant and as a variable parameter. The numerical scheme consists of a two-level leapfrog method to solve the depth-averaged equations and a generalized Crank-Nicolson scheme to compute the vertical profile of the velocity field. The cost functional in the adjoint scheme consists of two terms. The first term is a certain norm of the difference between computed and observed velocity data and the second term measures the total variation in the eddy viscosity function. The latter term is not needed when the data are exact for the model but is necessary to smooth out the instabilities associated with ‘noisy’ data. It is shown that a satisfactory minimization can be accomplished using either the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton algorithm or Nash's truncated Newton algorithm. Very effective estimation of eddy viscosity profiles is shown to be achieved even when the amount of data is quite small. 相似文献
118.
Solid state nuclear magnetic resonance imaging (NMRI) techniques have been steadily improving over the years. Today high-resolution images of rigid solids are now accomplished by many different means. For abundant nuclei, the combination of multiple-pulse line narrowing and pulsed field gradients have greatly improved both the resolution and sensitivity of the imaging experiment, but often at the expense of the chemical information in the material. In this paper we discuss means of incorporating NMR parameters in the imaging experiment to generate image contrast which provides information about local variations in the chemistry of the material. 相似文献
119.
本文对微波场效应管Ⅰ—Ⅴ特性模型进行了研究,分析比较了八种常用模型的优缺点,它可为微波电路的设计提供一个实用的参考依据.在模型参数提取中,我们采用了一种新算法,先应用一个基于主成份灵敏度分析的空间坐标变换,然后采用Levenberg-Marquardt算法进行优化拟合.实际计算表明,此法能够快速、精确地提取模型参数. 相似文献
120.
本文叙述了VLSI CAD中版图参数提取并行算法在Transputer并行加速器上的实现。参数提取的并行算法是利用图形运算的区域并行性将版图划分为与处理器数目相等的若干区域,然后并行地在各处理器中完成对应区域的版图参数提取。用保持划分区域内图形向量数相等的方法,使各处理器负载均衡,经计算证实,各处理器负载均衡性较好,大大提高了运行速度。Transputer并行加速器具有优良的性能价格比,在其上实现 相似文献