全文获取类型
收费全文 | 7364篇 |
免费 | 861篇 |
国内免费 | 726篇 |
专业分类
电工技术 | 1426篇 |
综合类 | 1164篇 |
化学工业 | 345篇 |
金属工艺 | 263篇 |
机械仪表 | 362篇 |
建筑科学 | 326篇 |
矿业工程 | 138篇 |
能源动力 | 167篇 |
轻工业 | 146篇 |
水利工程 | 71篇 |
石油天然气 | 136篇 |
武器工业 | 71篇 |
无线电 | 886篇 |
一般工业技术 | 628篇 |
冶金工业 | 294篇 |
原子能技术 | 110篇 |
自动化技术 | 2418篇 |
出版年
2024年 | 35篇 |
2023年 | 105篇 |
2022年 | 160篇 |
2021年 | 188篇 |
2020年 | 262篇 |
2019年 | 216篇 |
2018年 | 198篇 |
2017年 | 251篇 |
2016年 | 274篇 |
2015年 | 310篇 |
2014年 | 439篇 |
2013年 | 476篇 |
2012年 | 650篇 |
2011年 | 574篇 |
2010年 | 498篇 |
2009年 | 432篇 |
2008年 | 419篇 |
2007年 | 485篇 |
2006年 | 477篇 |
2005年 | 410篇 |
2004年 | 304篇 |
2003年 | 264篇 |
2002年 | 249篇 |
2001年 | 214篇 |
2000年 | 212篇 |
1999年 | 153篇 |
1998年 | 120篇 |
1997年 | 99篇 |
1996年 | 85篇 |
1995年 | 84篇 |
1994年 | 50篇 |
1993年 | 53篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有8951条查询结果,搜索用时 31 毫秒
1.
Guoxiang
Zhang Junyu Xiang 《International journal for numerical methods in engineering》2020,121(15):3339-3361
A new eight-node conforming quadrilateral element with high-order completeness, denoted as QH8-C1, is proposed in this article. First, expressions for the interpolation displacement function satisfying the requirements for high-order completeness in the global coordinate system are constructed. Second, the displacement function expression in global coordinates is transformed into isoparametric coordinates, and the relationships between the two series of coefficients for the two kinds of displacement function expressions are found. Third, the displacement function expression is modified to satisfy the requirements of nodal freedom and interelement boundary continuity. The key to the new element construction is the derivation of the linear relationship expressions among 12 coefficients of element displacement interpolation polynomials in the global and isoparametric coordinate systems. As a result, the relationship between quadratic completeness and interelement continuity is explicitly given, and a proof of the completeness and the continuity was conducted to theoretically guarantee the validity of the derivation results. Furthermore, in order to verify the correctness of the theoretical work, nine numerical examples were performed. The computation results from these examples demonstrate that QH8-C1 exhibited excellent performance, including high simulation accuracy, fast convergence, insensitivity to mesh distortion, and monotonic convergence. 相似文献
2.
3.
Anis Zeglaoui Anouar Houmia Maher Mejai Radhouane Aloui 《International Journal of Adaptive Control and Signal Processing》2021,35(9):1842-1859
In compressive sampling theory, the least absolute shrinkage and selection operator (LASSO) is a representative problem. Nevertheless, the non-differentiable constraint impedes the use of Lagrange programming neural networks (LPNNs). We present in this article the -LPNN model, a novel algorithm that tackles the LASSO minimization together with the underlying theory support. First, we design a sequence of smooth constrained optimization problems, by introducing a convenient differentiable approximation to the non-differentiable -norm constraint. Next, we prove that the optimal solutions of the regularized intermediate problems converge to the optimal sparse signal for the LASSO. Then, for every regularized problem from the sequence, the -LPNN dynamic model is derived, and the asymptotic stability of its equilibrium state is established as well. Finally, numerical simulations are carried out to compare the performance of the proposed -LPNN algorithm with both the LASSO-LPNN model and a standard digital method. 相似文献
4.
《Measurement》2015
In the harmonic active power measurement, the highest uncertainties are generally introduced by the current and voltage transducers. In a previous paper, the authors showed that the current transformer (CT) can introduce significant errors in such measurement, especially if the phase shift between voltage and current is close to ±90°. In such condition the errors on harmonic power measurement are mainly due to the CT phase displacement. This paper shows that better results can be achieved with more linear transducers, such as the Rogowski coil current transducers (RCCTs), whose metrological performance in distorted condition can be improved, by means of a proper compensation method. The proposed method for RCCTs compensation is based on the frequency response and it allows to reduce the errors on harmonic power measurement, also for phase shift close to ±90°. The study is supported by several experimental tests. 相似文献
5.
6.
国产风机盘管空调系统常见问题分析 总被引:2,自引:1,他引:1
分析了国产风机盘管使用中常见的问题,指出机组因风量不足、冷量风量匹配不合理以及风机盘管某些设备故障,导致了风机盘管精度低、舒适性差、能耗高等一系列问题。指出应引起空调设计和运行维护人员的注意。 相似文献
7.
A. Yu. Luchka 《Cybernetics and Systems Analysis》2003,39(6):880-888
A modified variational-gradient method is proposed and substantiated for quasilinear operator equations in a Hilbert space. 相似文献
8.
本文运用多输入多输出系统参数的集员辨识的结果讨论了Hammerstein系统参数的集员辨识.在系统动态噪声有界的假定下导出了Hammerstein系统参数的成员集是个椭球,并证明了在一定条件下椭球趋向于一点,文中还给出了仿真例子. 相似文献
9.
10.
研究H90-钢-H90反向凝固复合过程中复合层厚度的变化规律以及复合带的组织和性能,探讨界面结合机理。结果表明:随着浸渍时间的增加,复合层的厚度变化经历了凝固生长、平衡相持和回熔3个阶段,钢带的预热温度越低,获得的最大复合层厚度越厚;H90复合层的组织为等轴晶粒,复合界面处Cu和Fe发生了扩散,而Zn未发生明显扩散,扩散层较薄,约为4μm;复合带的界面结合牢固;不同复合层厚度的复合带,其力学性能略有差异,但均达到GB5213——85所规定的F级深冲钢板的力学性能要求。 相似文献