全文获取类型
收费全文 | 12674篇 |
免费 | 1171篇 |
国内免费 | 323篇 |
专业分类
电工技术 | 144篇 |
综合类 | 1351篇 |
化学工业 | 2578篇 |
金属工艺 | 222篇 |
机械仪表 | 353篇 |
建筑科学 | 4914篇 |
矿业工程 | 1032篇 |
能源动力 | 160篇 |
轻工业 | 658篇 |
水利工程 | 315篇 |
石油天然气 | 582篇 |
武器工业 | 14篇 |
无线电 | 193篇 |
一般工业技术 | 742篇 |
冶金工业 | 411篇 |
原子能技术 | 143篇 |
自动化技术 | 356篇 |
出版年
2024年 | 29篇 |
2023年 | 148篇 |
2022年 | 254篇 |
2021年 | 334篇 |
2020年 | 327篇 |
2019年 | 281篇 |
2018年 | 270篇 |
2017年 | 356篇 |
2016年 | 419篇 |
2015年 | 405篇 |
2014年 | 733篇 |
2013年 | 799篇 |
2012年 | 970篇 |
2011年 | 995篇 |
2010年 | 723篇 |
2009年 | 779篇 |
2008年 | 676篇 |
2007年 | 818篇 |
2006年 | 737篇 |
2005年 | 630篇 |
2004年 | 513篇 |
2003年 | 447篇 |
2002年 | 387篇 |
2001年 | 352篇 |
2000年 | 289篇 |
1999年 | 259篇 |
1998年 | 187篇 |
1997年 | 282篇 |
1996年 | 135篇 |
1995年 | 128篇 |
1994年 | 80篇 |
1993年 | 71篇 |
1992年 | 81篇 |
1991年 | 56篇 |
1990年 | 47篇 |
1989年 | 47篇 |
1988年 | 43篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Reliable prediction of flooding conditions is needed for sizing and operating packed extraction columns. Due to the complex interplay of physicochemical properties, operational parameters and the packing-specific properties, it is challenging to develop accurate semi-empirical or rigorous models with a high validity range. State of the art models may therefore fail to predict flooding accurately. To overcome this problem, a data-driven model based on Gaussian processes is developed to predict flooding for packed liquid-liquid and high-pressure extraction columns. The optimized Gaussian process for the liquid-liquid extraction column results in an average absolute relative error (AARE) of 15.23 %, whereas the algorithm for the high-pressure extraction column results in an AARE of 13.68 %. Both algorithms can predict flooding curves for different packing geometries and chemical systems precisely. 相似文献
2.
《Geotextiles and Geomembranes》2020,48(6):897-911
Dynamic responses of the geosynthetic-encased stone column (GESC) supported embankment under traffic loads have become a hot topic. This study investigates the responses of GESC improved ground under vertical cyclic loading. A series of laboratory tests in a designed model test tank have been carried out with different loading parameters (varied loading amplitudes and frequencies), different column dimensions (varied encasement lengths and column diameters). In the tests, the soil-column stress distribution, accumulated settlement of loading plate, excess pore water pressure in the surrounding soil and lateral bulging of the stone column are monitored. Experimental results indicate that the vertical stress on the stone column increases with the increment of encasement length, and decreases with the increment of column diameter, loading amplitude and loading frequency. The increasing stress on the surrounding soil leads to a greater accumulated settlement of the loading plate and excess pore water pressure, while the increasing stress on the column leads to larger lateral bulging of the column. Excess pore water pressure dissipates effectively through vertical and horizontal drainage channels provided by the stone column and the sand bed. The geosynthetic encasement prevents the clay from obstructing the drainage channel by filtration and guarantees the drainage effect. 相似文献
3.
In this paper, the dynamic behaviors on the basis of simulation for high-purity heat integrated air separation column (HIASC) are studied. A nonlinear generic model control (GMC) scheme is proposed based on the nonlinear behavior analyses of a HIASC process, and an adaptive generic model control (AGMC) scheme is further presented to correct the model parameters online. Related internal model control (IMC) scheme and multi-loop PID (M-PID) scheme are also developed as the comparative base. The comparative researches are carried out among these linear and nonlinear control schemes in detail. The simulation research results show that the proposed AGMC schemes present advantages in both servo control and regulatory control for the high-purity HIASC. 相似文献
4.
5.
根据延迟焦化装置露天栈桥的工程设计实践,围绕一炉两塔(一个加热炉两个焦炭塔)的焦化装置,分析了露天栈桥设计中的要点及难点,对其在平面布置、基础安排和吊车梁选型等设计方面做一些介绍和论述。 相似文献
6.
7.
本文以NH3-H2O系统Gibbs自由能、熵、焓和汽液相平衡的热力学模型为基础,用松弛法进行了无水氨精馏塔的模拟计算。改变无水氨采出比、回流比(直汽量)和进料板位置均影响蒸馏效果。 相似文献
8.
9.
10.