全文获取类型
收费全文 | 2359篇 |
免费 | 90篇 |
国内免费 | 72篇 |
专业分类
化学 | 957篇 |
晶体学 | 17篇 |
力学 | 121篇 |
综合类 | 16篇 |
数学 | 439篇 |
物理学 | 971篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 48篇 |
2021年 | 39篇 |
2020年 | 43篇 |
2019年 | 47篇 |
2018年 | 45篇 |
2017年 | 49篇 |
2016年 | 50篇 |
2015年 | 39篇 |
2014年 | 76篇 |
2013年 | 396篇 |
2012年 | 82篇 |
2011年 | 86篇 |
2010年 | 83篇 |
2009年 | 105篇 |
2008年 | 111篇 |
2007年 | 144篇 |
2006年 | 112篇 |
2005年 | 93篇 |
2004年 | 84篇 |
2003年 | 84篇 |
2002年 | 76篇 |
2001年 | 63篇 |
2000年 | 50篇 |
1999年 | 61篇 |
1998年 | 52篇 |
1997年 | 29篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有2521条查询结果,搜索用时 15 毫秒
11.
An energy-dependent partitioning scheme is explored for extracting a small number of eigenvalues of a real symmetric matrix with the help of genetic algorithm. The proposed method is tested with matrices of different sizes (30 × 30 to 1000 × 1000). Comparison is made with Löwdin’s strategy for solving the problem. The relative advantages and disadvantages of the GA-based method are analyzed 相似文献
12.
In single-objective optimization it is possible to find a global optimum, while in the multi-objective case no optimal solution is clearly defined, but several that simultaneously optimize all the objectives. However, the majority of this kind of problems cannot be solved exactly as they have very large and highly complex search spaces. Recently, meta-heuristic approaches have become important tools for solving multi-objective problems encountered in industry as well as in the theoretical field. Most of these meta-heuristics use a population of solutions, and hence the runtime increases when the population size grows. An interesting way to overcome this problem is to apply parallel processing. This paper analyzes the performance of several parallel paradigms in the context of population-based multi-objective meta-heuristics. In particular, we evaluate four alternative parallelizations of the Pareto simulated annealing algorithm, in terms of quality of the solutions, and speedup. 相似文献
13.
设(X,Y),(X1,Y1),…,(XnYn)为取值于 Rd× R的 i.i.d.随机变量,E(|Y|) <∞.设mn(x)为回归函数m(x)=E(|Y|X=x)基于分割的估计,本文在对mn(x)进行改良的条件下得到改良的基于分割的强相合估计. 相似文献
14.
We present a model arising from the thermal modelling of two metal casting processes. We consider an enthalpy formulation for this two‐phase Stefan problem in a time varying three‐dimensional domain and consider convective heat transfer in the liquid phase. Then, we introduce a weak formulation in a fixed domain, by means of a suitable transformation. Existence of solution is obtained by applying an abstract theorem. The proof of this theorem is done by taking an implicit discretization in time together with a regularization. By passing to the limit in the regularization parameter and in the time step, we obtain the existence of solution of the continuous problem. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates. 相似文献
16.
提出用发展中的硅微机械加工技术设计制作硅一体化薄膜微电极器件.这类微电化学器件具有微电极所特有的全部优点,而且由于结构上的一体化,便于器件整体的微型化和集成化.试用薄膜微电极器件电流法常温直接检测CO2气体,取得了满意的结果。设想通过器件三维构型设计的改进和完善,器件工作的长期稳定性可望进一步提高. 相似文献
17.
Fabio Schoen 《Journal of Global Optimization》1994,4(1):17-35
In this paper a new algorithm is proposed for global optimization problems. The main idea is that of modifying a standard clustering approach by sequentially sampling the objective function while adaptively deciding an appropriate sample size. Theoretical as well as computational results are presented. 相似文献
18.
19.
We develop two implementable algorithms, the first for the solution of finite and the second for the solution of semi-infinite min-max-min problems. A smoothing technique (together with discretization for the semi-infinite case) is used to construct a sequence of approximating finite min-max problems, which are solved with increasing precision. The smoothing and discretization approximations are initially coarse, but are made progressively finer as the number of iterations is increased. This reduces the potential ill-conditioning due to high smoothing precision parameter values and computational cost due to high levels of discretization. The behavior of the algorithms is illustrated with three semi-infinite numerical examples. 相似文献
20.
Microemulsions are becoming increasingly complex systems by containing more sophisticated surfactants, polymers, biomolecules, inorganic nanoparticles, etc. The detailed understanding of such more complex systems requires increasingly more refined and comprehensive characterisation. This is typically done by the combination of complementary techniques and is aided by the fact that several experimental methods have been improved (such as electron microscopy) in recent times, new ones have become available (such as fluorescence correlation spectroscopy), and the theoretical understanding of structural data is advancing. 相似文献