全文获取类型
收费全文 | 581019篇 |
免费 | 25576篇 |
国内免费 | 12811篇 |
专业分类
电工技术 | 21936篇 |
技术理论 | 56篇 |
综合类 | 19773篇 |
化学工业 | 96745篇 |
金属工艺 | 33651篇 |
机械仪表 | 31203篇 |
建筑科学 | 29879篇 |
矿业工程 | 14714篇 |
能源动力 | 13587篇 |
轻工业 | 28291篇 |
水利工程 | 9339篇 |
石油天然气 | 35976篇 |
武器工业 | 2627篇 |
无线电 | 56573篇 |
一般工业技术 | 102235篇 |
冶金工业 | 50422篇 |
原子能技术 | 14330篇 |
自动化技术 | 58069篇 |
出版年
2023年 | 5527篇 |
2022年 | 10804篇 |
2021年 | 15266篇 |
2020年 | 11964篇 |
2019年 | 10710篇 |
2018年 | 14598篇 |
2017年 | 16058篇 |
2016年 | 15296篇 |
2015年 | 15244篇 |
2014年 | 21158篇 |
2013年 | 29221篇 |
2012年 | 27417篇 |
2011年 | 31291篇 |
2010年 | 26443篇 |
2009年 | 26406篇 |
2008年 | 26089篇 |
2007年 | 25190篇 |
2006年 | 24586篇 |
2005年 | 21669篇 |
2004年 | 15795篇 |
2003年 | 14388篇 |
2002年 | 13234篇 |
2001年 | 12400篇 |
2000年 | 12920篇 |
1999年 | 13879篇 |
1998年 | 15283篇 |
1997年 | 12571篇 |
1996年 | 10759篇 |
1995年 | 8974篇 |
1994年 | 7785篇 |
1993年 | 6697篇 |
1992年 | 5697篇 |
1991年 | 5313篇 |
1990年 | 4975篇 |
1989年 | 4597篇 |
1988年 | 4282篇 |
1987年 | 3938篇 |
1986年 | 3689篇 |
1985年 | 3653篇 |
1984年 | 3494篇 |
1983年 | 3348篇 |
1982年 | 3184篇 |
1980年 | 3200篇 |
1979年 | 3322篇 |
1978年 | 3523篇 |
1977年 | 3498篇 |
1976年 | 3964篇 |
1975年 | 3229篇 |
1974年 | 3306篇 |
1973年 | 3352篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
为了分析多水库系统中两座水库之间灌溉用水的分配问题,建立了基到动态规划的神经网络模型。为了研究从一座上游水库取水在下游两座之库之间进行水量分配的问题,提出了3个状态变量和4个决策变量的改进的动态规划算法。采用神经网络模型,用3个状态变量动态规划算法得出调度原则,就所研究的多水库系统实例来说,新的动态规划神经网络模型的性能很好,将该模型的性能与临时凑合的标准调度原则和以前推荐使用的约束动态规划神经网络模型进行了比较。 相似文献
12.
13.
G. I. Glazov A. M. Garaiev R. V. Timerkhanov 《Chemistry and Technology of Fuels and Oils》2003,39(1-2):26-53
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants. 相似文献
14.
A. V. Butko A. A. Klimov S. A. Nikitov Yu. A. Filimonov 《Journal of Communications Technology and Electronics》2006,51(8):944-947
The magneto-optical Kerr effect for red (628 nm) and green (532 nm) light is used to study magnetization processes in 2D magnonic crystals obtained by etching pits with the diameter D ≈ 32 μm to a depth of t ≤ 2 μm in a 16.1-μm-thick film of yttrium iron garnet (YIG). Hysteresis loops obtained in the case of the inplane crystal magnetization at 628 nm are characterized by lower saturation fields H s and higher remanent magnetizations than those obtained at 532 nm, a result that is attributed to different absorption coefficients of the YIG film at these wavelengths. This difference between the magnetization curves reflects the fact that the magnonic-crystal surface probed with the green light makes a greater contribution to the magneto-optical Kerr effect. Therefore, the green light is more sensitive to the demagnetizing fields, which govern magnetization processes in the magnonic crystals. 相似文献
15.
S. V. Doronin 《Chemical and Petroleum Engineering》2006,42(7-8):461-464
Current features are considered in the calculation of carrying capacities for constructions in engineering plant (EP). Methods
and algorithms are described for EP calculations with comprehensive incorporation of the effects from technological and working
defects on the behavior of structures under standard and emergency conditions.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 8, pp. 38–40, August, 2006. 相似文献
16.
第三节 常见氧化物膜目前研究最多的氧化物膜可谓二氧化硅和二氧化钛膜 ,这两种薄膜也是接受呈色离子、制备彩色镀膜常用的基体膜 ,所以 ,有必要将它们单独列出 ,加以讨论。1 二氧化钛膜在所有高折射率材料中 ,由钛的化合物制备的氧化物膜具有特殊的实际意义。因此 ,对二氧化 相似文献
17.
V. N. Pavlechko 《Journal of Engineering Physics and Thermophysics》2004,77(1):115-120
Relations for determining a motive force in a complex model of mass transfer as applied to concurrent, countercurrent, and cross motion of the vapor and liquid phases have been introduced. These forces have been compared for different forms of organization of the flow, and their comparison with similar quantities from the known Murphree and Hausen models is presented. 相似文献
18.
对在实际组网中选择合理的ASON架构和保护方式作了相应分析,并为搭建可向ASON平滑演进的传统网络时需注意的问题提供了参考意见, 相似文献
19.
M A Fennir J A Landry H S Ramaswamy V G S Raghavan 《The Journal of microwave power and electromagnetic energy》2003,38(3):189-196
This study investigates the effect of extraction methods on the color of date syrup and the potential use of microwave power for syrup processing. Sugar solutions were extracted from dates by boiling, soaking and blending. Color and sugar content of the extracted solutions were measured, and the percentage of sugar extracted form the total fruit sugar determined. Boiling was found to be the most efficient method of extraction whereby 74% of total samples sugar was extracted. In contrast, only 54.2% of fruit sugar was extracted by blending and 42% by soaking. In addition, solutions extracted by soaking and blending had a foaming problem in the subsequent concentration process. The extraction method had no effect on the product final color. The extracted solution was concentrated using two heating methods: conventional and microwave heating at a 600 W capacity and a frequency of 2450 MHz applied at three power levels: 10, 7, and 6. In the heating process, 180 minutes were needed to achieve a 77% degrees Brix using convective heating, while it took 81, 138, and 166 minutes of microwave heating at power level 10, 7, and 6, respectively to achieve the same concentration. Water activity of the syrup was measured within a sugar content range of 50 to 80% degrees Brix and the sugar concentration at which the product is shelf stable was determined at 76%. 相似文献
20.