全文获取类型
收费全文 | 10659篇 |
免费 | 1131篇 |
国内免费 | 1026篇 |
专业分类
电工技术 | 507篇 |
综合类 | 1558篇 |
化学工业 | 775篇 |
金属工艺 | 907篇 |
机械仪表 | 720篇 |
建筑科学 | 723篇 |
矿业工程 | 208篇 |
能源动力 | 699篇 |
轻工业 | 118篇 |
水利工程 | 564篇 |
石油天然气 | 490篇 |
武器工业 | 96篇 |
无线电 | 789篇 |
一般工业技术 | 2474篇 |
冶金工业 | 365篇 |
原子能技术 | 166篇 |
自动化技术 | 1657篇 |
出版年
2024年 | 47篇 |
2023年 | 192篇 |
2022年 | 218篇 |
2021年 | 326篇 |
2020年 | 373篇 |
2019年 | 354篇 |
2018年 | 299篇 |
2017年 | 345篇 |
2016年 | 355篇 |
2015年 | 338篇 |
2014年 | 471篇 |
2013年 | 675篇 |
2012年 | 680篇 |
2011年 | 702篇 |
2010年 | 508篇 |
2009年 | 569篇 |
2008年 | 566篇 |
2007年 | 601篇 |
2006年 | 626篇 |
2005年 | 534篇 |
2004年 | 460篇 |
2003年 | 441篇 |
2002年 | 341篇 |
2001年 | 323篇 |
2000年 | 342篇 |
1999年 | 303篇 |
1998年 | 260篇 |
1997年 | 257篇 |
1996年 | 240篇 |
1995年 | 192篇 |
1994年 | 156篇 |
1993年 | 131篇 |
1992年 | 133篇 |
1991年 | 111篇 |
1990年 | 97篇 |
1989年 | 89篇 |
1988年 | 60篇 |
1987年 | 27篇 |
1986年 | 16篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Relative grain boundary energies can be simply related to true dihedral angles, which are the angles between grain boundary planes meeting at triple edges in polycrystals. Some limited efforts in the measurement of true dihedral angles have used the technique of serial sectioning, which is usually cumbersome and time consuming. In this study the three‐dimensional probe called the ‘disector’ has been employed to evaluate true dihedral angles. This probe, combined with automated image processing, introduces precision as well as efficiency, overcomes the disadvantages of the two‐dimensional probe and is far less tedious and less complicated than serial sectioning. It is shown that the technique is relatively simple and therefore can be applied to obtain a significantly large and accurate statistical sample of true dihedral angles. The application of this method is demonstrated by evaluating the triple junction geometry and the associated relative grain boundary energies in polycrystalline 316L austenitic stainless steel. 相似文献
22.
Chongbin Zhao Tianyun Liu 《International journal for numerical methods in engineering》2003,58(10):1435-1456
This paper presents an exact non‐reflecting boundary condition for dealing with transient scalar wave propagation problems in a two‐dimensional infinite homogeneous layer. In order to model the complicated geometry and material properties in the near field, two vertical artificial boundaries are considered in the infinite layer so as to truncate the infinite domain into a finite domain. This treatment requires the appropriate boundary conditions, which are often referred to as the artificial boundary conditions, to be applied on the truncated boundaries. Since the infinite extension direction is different for these two truncated vertical boundaries, namely one extends toward x →∞ and another extends toward x→‐ ∞, the non‐reflecting boundary condition needs to be derived on these two boundaries. Applying the variable separation method to the wave equation results in a reduction in spatial variables by one. The reduced wave equation, which is a time‐dependent partial differential equation with only one spatial variable, can be further changed into a linear first‐order ordinary differential equation by using both the operator splitting method and the modal radiation function concept simultaneously. As a result, the non‐reflecting artificial boundary condition can be obtained by solving the ordinary differential equation whose stability is ensured. Some numerical examples have demonstrated that the non‐reflecting boundary condition is of high accuracy in dealing with scalar wave propagation problems in infinite and semi‐infinite media. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
23.
颜力 《太赫兹科学与电子信息学报》2003,1(1):31-36
在频域中推导了适用于差分类数值方法的吸收边界条件的构造方法,并通过选取不同参数导出了几种现有的吸收边界条件。在计算了一般形式的吸收边界条件的反射系数之后,提出了一种简单实用的自适应吸收边界条件。 相似文献
24.
25.
26.
This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated. 相似文献
27.
The macroscopic deformation behavior of a fiber-reinforced aluminum-boron composite is investigated. Different periodic and random arrangements of the microstructure are considered with macroscopic hardening behavior due to the evolution of plastic zones on the microscale being taken into account.
For the solution of the initial boundary value problem, a non-standard algorithm is applied. It consists of the direct solution of the whole set of equations, treating all variables as global quantities. Together with a higher order time integration method (BDF2), an automatic step size control is used in the FEM calculations. 相似文献
28.
陆相断陷湖盆中层序边界是由于沉积物表面高出沉积基准面或盆地基准面、沉积物发生剥蚀或无沉积作用所形成的,其产生机理主要有边界断层停止活动、断块翘倾活动、湖盆整体抬升和湖平面下降。层序边界在地震特征上、测井曲线上、钻井剖面中的岩性、岩相特征、古生物组合、微量元素的变化上均有明显的特征。利用这些特征,在济阳坳陷下第三系中识别出9个三级层序。 相似文献
29.
利用Love波特性计算地基动力响应 总被引:5,自引:2,他引:3
本文利用Love波弥散特性在频域上对地基出平面振动及扭振问题进行了研究。在计算区域内结构将采用有限单元划分,而在边界上则根据Love 面波特性使用传递边界有限单元。本文同时讨论了不同模态波对结构动力响应的贡献。本文方法也适合于静力分析。 相似文献
30.
波浪力计算中的一个新边界元方法 总被引:8,自引:4,他引:4
滕斌 《水动力学研究与进展(A辑)》1994,(2):215-223
本文就波浪与结构物作用问题,提出了一个新的高阶边界元方法。较之Eatock Toylor和Chau的方法,本文在体内附助积分方程中应用了满足刚性水面条件和弱刚性底面条件的简单格林函数。计算速度相应地有所提高;漂浮结构的积分方程更为简洁;计算结果与Eatock Taylor和Chau的方法具有几乎相同的精度和收敛速度。 相似文献