全文获取类型
收费全文 | 6539篇 |
免费 | 729篇 |
国内免费 | 534篇 |
专业分类
电工技术 | 471篇 |
综合类 | 610篇 |
化学工业 | 482篇 |
金属工艺 | 372篇 |
机械仪表 | 510篇 |
建筑科学 | 309篇 |
矿业工程 | 541篇 |
能源动力 | 93篇 |
轻工业 | 177篇 |
水利工程 | 82篇 |
石油天然气 | 112篇 |
武器工业 | 49篇 |
无线电 | 477篇 |
一般工业技术 | 716篇 |
冶金工业 | 297篇 |
原子能技术 | 31篇 |
自动化技术 | 2473篇 |
出版年
2024年 | 61篇 |
2023年 | 142篇 |
2022年 | 174篇 |
2021年 | 223篇 |
2020年 | 237篇 |
2019年 | 213篇 |
2018年 | 167篇 |
2017年 | 236篇 |
2016年 | 260篇 |
2015年 | 241篇 |
2014年 | 378篇 |
2013年 | 448篇 |
2012年 | 447篇 |
2011年 | 428篇 |
2010年 | 344篇 |
2009年 | 392篇 |
2008年 | 354篇 |
2007年 | 393篇 |
2006年 | 407篇 |
2005年 | 353篇 |
2004年 | 301篇 |
2003年 | 284篇 |
2002年 | 240篇 |
2001年 | 196篇 |
2000年 | 174篇 |
1999年 | 119篇 |
1998年 | 122篇 |
1997年 | 96篇 |
1996年 | 56篇 |
1995年 | 78篇 |
1994年 | 41篇 |
1993年 | 40篇 |
1992年 | 30篇 |
1991年 | 28篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1966年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7802条查询结果,搜索用时 0 毫秒
1.
2.
3.
Barbara M. Johnston Peter R. Johnston 《International journal for numerical methods in engineering》2003,56(4):589-607
Accurate numerical evaluation of integrals arising in the boundary element method is fundamental to achieving useful results via this solution technique. In this paper, a number of techniques are considered to evaluate the weakly singular integrals which arise in the solution of Laplace's equation in three dimensions and Poisson's equation in two dimensions. Both are two‐dimensional weakly singular integrals and are evaluated using (in a product fashion) methods which have recently been used for evaluating one‐dimensional weakly singular integrals arising in the boundary element method. The methods used are based on various polynomial transformations of conventional Gaussian quadrature points where the transformation polynomial has zero Jacobian at the singular point. Methods which split the region of integration into sub‐regions are considered as well as non‐splitting methods. In particular, the newly introduced and highly accurate generalized composite subtraction of singularity and non‐linear transformation approach (GSSNT) is applied to various two‐dimensional weakly singular integrals. A study of the different methods reveals complex relationships between transformation orders, position of the singular point, integration kernel and basis function. It is concluded that the GSSNT method gives the best overall results for the two‐dimensional weakly singular integrals studied. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
讨论了输出终端带不等式约束情形的多输入多输出系统,说明了这些约束可以通过修改输入柔化系数而使其得以满足,在柔化系数的选择范围确定过程中,为了避免矩阵求逆,采用利用已知数据辨识参数的方法来确定柔化系数,从而使得问题简化。降低了计算量且加快了收敛速度。 相似文献
5.
Non-pinched, minimum energy solutions are important class of distillation designs that offer the potential advantage of a better trade-off between capital investment and operating costs. In this paper, two important tasks associated with non-pinched distillation designs are studied. Thus the novel contributions of this work to the literature are
- (1) A comprehensive methodology for finding non-pinched minimum energy designs.
- (2) Understanding of the reasons for the existence of non-pinched distillation designs.
6.
Sucrose crystallization in thin films (50–55 μm) was studied, using a videomicroscopy technique, at conditions encountered during hard panning processes. No nucleation occurred in unseeded films, while a linear increase in seeded crystals occurred during drying. Crystal growth rate increased with temperature (25–30°C) and with air velocity (2.4–12.5 m/sec), but did not change with varying sucrose concentrations (70–76% w/w) and relative humidities (0–66% at 30°C). FD & C Yellow No. 5 food coloring in the dye form (0.05–0.5 g/100 mL) showed no effects while similar concentrations in the lake form inhibited crystal growth rate. 相似文献
7.
Investigations have been carried out on an erosion-corrosion apparatus to investigate the behaviour of corrosion-resistant highalloy iron-base materials containing hard phases. These materials had been optimized for increased wear resistance under complex stress conditions. As expected, in dry erosion tests, very low mass losses were established; there was little difference between the materials. Also, in corrosive environments (NaCl, H2SO4), the materials showed good stability; however, the duplex structures were superior to the martensitic ones. The combination of erosion and corrosion produced large differences and, in some cases, markedly reduced resistance to damage. These results confirmed observations that it is impossible to deduce the environmentally influenced mechanical behaviour of an alloy from its behaviour in separate corrosion and erosion experiments. The basic mechanisms underlying these processes have been investigated only tentatively. 相似文献
8.
9.
国内外钻探用金刚石复合片性能的研究 总被引:1,自引:0,他引:1
主要介绍国内外金刚石复合片性能及采用四高复合片钻探硬岩的初试,为快速钻探提供一个新的途径. 相似文献
10.
形状记忆聚氨酯的结构与性能研究 总被引:1,自引:0,他引:1
以 2 ,4 -甲苯二异氰酸酯 (2 ,4 -TDI)、不同分子量的聚己二酸丁二醇酯 (PBAG)和 1,4-丁二醇 (BDO)为原料合成了具有形状记忆功能的聚氨酯材料。通过DSC、弯曲实验和力学实验 ,研究了形状记忆聚氨酯的性能 ,发现软段高度结晶和硬段聚集形成硬段微区是其具有较好形状记忆性能的必要条件。 相似文献