全文获取类型
收费全文 | 18438篇 |
免费 | 1594篇 |
国内免费 | 1207篇 |
专业分类
电工技术 | 821篇 |
技术理论 | 1篇 |
综合类 | 3786篇 |
化学工业 | 1692篇 |
金属工艺 | 625篇 |
机械仪表 | 1018篇 |
建筑科学 | 903篇 |
矿业工程 | 334篇 |
能源动力 | 493篇 |
轻工业 | 608篇 |
水利工程 | 580篇 |
石油天然气 | 1299篇 |
武器工业 | 248篇 |
无线电 | 1427篇 |
一般工业技术 | 2891篇 |
冶金工业 | 489篇 |
原子能技术 | 371篇 |
自动化技术 | 3653篇 |
出版年
2024年 | 56篇 |
2023年 | 164篇 |
2022年 | 280篇 |
2021年 | 298篇 |
2020年 | 390篇 |
2019年 | 436篇 |
2018年 | 458篇 |
2017年 | 493篇 |
2016年 | 536篇 |
2015年 | 504篇 |
2014年 | 805篇 |
2013年 | 1180篇 |
2012年 | 1235篇 |
2011年 | 1222篇 |
2010年 | 990篇 |
2009年 | 978篇 |
2008年 | 1019篇 |
2007年 | 1121篇 |
2006年 | 1080篇 |
2005年 | 913篇 |
2004年 | 826篇 |
2003年 | 754篇 |
2002年 | 651篇 |
2001年 | 530篇 |
2000年 | 529篇 |
1999年 | 534篇 |
1998年 | 462篇 |
1997年 | 417篇 |
1996年 | 387篇 |
1995年 | 385篇 |
1994年 | 303篇 |
1993年 | 257篇 |
1992年 | 224篇 |
1991年 | 199篇 |
1990年 | 160篇 |
1989年 | 134篇 |
1988年 | 100篇 |
1987年 | 57篇 |
1986年 | 43篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Sheng Tian 《哈尔滨工业大学学报(英文版)》2015,22(3):101-106
Full frontal impact theory needs researching and exploring to satisfy the primary safety design of occupant restraint system,avoiding the increasingly "engineering"trend in order to develop and design safety vehicle. After occupant restraint system is simulated by using linear elastic stiffness k,the occupant-vehicle frontal rigid barrier impact model is established. Dynamic equation of dummy chest coupling vehicle is built for full frontal impact based on ordinary vehicle deceleration by Hooke law,and the equation is solved by comparing coefficient and satisfying boundary qualifications. While relative vehicle characteristic parameters are kept unchanging,the actual vehicle deceleration is fitted to the simplified equivalent square wave( ESW),tipped equivalent square wave( TESW) and equivalent dual trapezoids wave( EDTW). Phase angle and amplitude A of dynamic equations based on ESW,TESW and EDTW are calculated and deduced. The results show that: the dynamic equation of dummy chest coupling vehicle can be well utilized to instruct the primary safety design of full frontal impact for objective vehicle to satisfy chest deceleration demands and the equation based on TESW is best for this design. 相似文献
62.
该文提出了一种可以广泛应用于四阶PDE曲面的裁剪方法。利用PDE的参数域内的曲线在曲面上投影,得到所求裁剪曲面的边界曲线,然后通过边界曲线的导矢与曲面在边界曲线处的法向量得到边界曲线处的跨界导矢,最后以求得的裁剪曲面的边界曲线以及裁剪曲面在边界曲线处的跨界导矢为PDE曲面的边界条件,用四阶的PDE曲面方程求得PDE裁剪曲面。 相似文献
63.
The conservative method of calculating the Boltzmann collision integral for simple gases, gas mixtures and gases with rotational degrees of freedom of molecules is presented. In all cases the common approach based on the projection technique of summing up the contributions in the collision integral is used. The method is applied for solving the Boltzmann kinetic equation for two fundamental rarefied gas flow problems: the heat transfer problem and the problem of shock wave structure. A comparison with experimental and numerical data of other authors is reported. It is shown that the considered numerical method allows one to solve the Boltzmann equation for real gases with high accuracy. 相似文献
64.
In this paper, we propose a new compact fourth-order accurate method for solving the two-dimensional fourth-order elliptic boundary value problem with third-order nonlinear derivative terms. We use only 9-point single computational cell in the scheme. The proposed method is then employed to solve Navier–Stokes equations of motion in terms of streamfunction–velocity formulation, and the lid-driven square cavity problem. We describe the derivation of the method in details and also discuss how our streamfunction–velocity formulation is able to handle boundary conditions in terms of normal derivatives. Numerical results show that the proposed method enables us to obtain oscillation-free high accuracy solution. 相似文献
65.
In this paper, we derive a high-order compact finite difference scheme for solving the reaction–subdiffusion equation with Neumann boundary value condition. The L1 method is used to approximate the temporal Caputo derivative, and the compact difference operator is applied for spatial discretization. We prove that the compact finite difference method is unconditionally stable and convergent with order O(τ2?α+h4) in L2 norm, where τ, α, and h are the temporal step size, the order of time fractional derivative and the spatial step size, respectively. Finally, some numerical experiments are carried out to show the effectiveness of the proposed difference scheme. 相似文献
66.
R.C. Mittal 《国际计算机数学杂志》2015,92(10):2139-2159
A technique to approximate the solutions of nonlinear Klein–Gordon equation and Klein–Gordon-Schrödinger equations is presented separately. The approach is based on collocation of cubic B-spline functions. The above-mentioned equations are decomposed into a system of partial differential equations, which are further converted to an amenable system of ODEs. The obtained system has been solved by SSP-RK54 scheme. Numerical solutions are presented for five examples, to show the accuracy and usefulness of proposed approach. The approximate solutions of both the equations are computed without using any transformation and linearization. The technique can be applied with ease to solve linear and nonlinear PDEs and also reduces the computational work. 相似文献
67.
68.
We place the continuous-time orbit problem in P, sharpening the decidability result shown by Hainry [7]. 相似文献
69.
许多实际系统可用n 维超球坐标系来描述, 并且系统有球对称的性质, 因而可通过研究半径方向的状态变化, 得到系统的全局动态过程. 通过将高维的对称系统转化为等价的径向一维方程, 本文采用边界Backstepping 方法设计了球对称反应扩散方程的输出反馈控制器. 使用容易测量的边界状态值, 设计了状态观测器来估计系统在空间域的所有状态, 从而实现输出反馈控制. 本文扩展了连续Backstepping 方法,提出了n维球坐标的Volterra 积分映射, 从而求出了显式表达的控制器和状态观测器. 论文用Lyapunov 函数法证明了输出反馈系统在H1范数下指数稳定, 表明状态对初值的连续依赖, 确保控制系统具有较好的性质, 不会在空间某点发散. 最后进行了数值仿真, 仿真结果表明系统在输出反馈控制律的作用下收敛到稳态值. 相似文献
70.