全文获取类型
收费全文 | 84824篇 |
免费 | 8161篇 |
国内免费 | 5193篇 |
专业分类
电工技术 | 7224篇 |
技术理论 | 4篇 |
综合类 | 9331篇 |
化学工业 | 8693篇 |
金属工艺 | 4772篇 |
机械仪表 | 4500篇 |
建筑科学 | 9200篇 |
矿业工程 | 4073篇 |
能源动力 | 3032篇 |
轻工业 | 4415篇 |
水利工程 | 3394篇 |
石油天然气 | 10974篇 |
武器工业 | 794篇 |
无线电 | 7416篇 |
一般工业技术 | 7855篇 |
冶金工业 | 4096篇 |
原子能技术 | 1090篇 |
自动化技术 | 7315篇 |
出版年
2024年 | 302篇 |
2023年 | 1142篇 |
2022年 | 2027篇 |
2021年 | 2519篇 |
2020年 | 2408篇 |
2019年 | 2167篇 |
2018年 | 1861篇 |
2017年 | 2470篇 |
2016年 | 2729篇 |
2015年 | 2947篇 |
2014年 | 4684篇 |
2013年 | 4516篇 |
2012年 | 5861篇 |
2011年 | 6314篇 |
2010年 | 4777篇 |
2009年 | 4898篇 |
2008年 | 4471篇 |
2007年 | 5704篇 |
2006年 | 5400篇 |
2005年 | 4786篇 |
2004年 | 4093篇 |
2003年 | 3772篇 |
2002年 | 3087篇 |
2001年 | 2573篇 |
2000年 | 2283篇 |
1999年 | 1897篇 |
1998年 | 1452篇 |
1997年 | 1234篇 |
1996年 | 1087篇 |
1995年 | 958篇 |
1994年 | 790篇 |
1993年 | 558篇 |
1992年 | 443篇 |
1991年 | 323篇 |
1990年 | 331篇 |
1989年 | 306篇 |
1988年 | 206篇 |
1987年 | 138篇 |
1986年 | 90篇 |
1985年 | 84篇 |
1984年 | 80篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 44篇 |
1980年 | 40篇 |
1979年 | 40篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1975年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
931.
针对实时控制系统接入各种现场设备并与之通讯的问题,提出并设计了一种跨平台实时控制系统的现场设备驱动。首先概述了设计的基本原理,然后详细阐述了驱动函数,驱动模块,驱动引擎等各模块的设计及在多操作系统平台的实现。最后以实际的使用示例说明设备驱动的使用方法。 相似文献
932.
The process of grinding soybeans to a fine flour and extracting the flour with hexane was studied on a pilot plant scale.
The crude oil from the pilot plant study had 15 ppm phosphorus and was suitable for physical refining after a light acid pretreatment
and bleaching. The refined oil showed a Lovibond color of 1.4 yellow and 0.3 red. The pilot plant study also showed that grinding
of the soybeans and the separation of solid from miscella were the most difficult steps in solvent extraction with fine flour.
A laboratory study on separation of miscella from meal by aqueous ethanol reduced the hold-up volume, but it did not remove
all the miscella. A test with betacarotene showed that only the miscella outside the flour particles was displaced.
Aqueous ethanol solutions used as a second solvent extracted additional nontriglyceride materials (primarily phospholipids)
from the meal. Also, the free fatty acid content of the oil was increased with aqueous ethanol solution wash. The quality
of the extracted crude oil was lowered by using a second solvent, but it had the advantage of needing only one centrifugation
to separate miscella from meal. 相似文献
933.
一种新颖的汉字字形相似度计算方法 总被引:1,自引:0,他引:1
为了利用字形描述技术识别相似汉字, 提出了三元组递归表示的汉字字形相似度计算方法。该算法把汉字表示为汉字结构、字首部件和字尾部件三元组, 以部件为运算对象, 字型结构为运算符, 将汉字描述为前缀表达式。通过建立汉字字形相似度计算递归模型, 使计算过程被逐层分解为原子部件间的相似性比较, 从而更好地降低了计算的复杂性。然后将其用于计算汉字的最佳相似字。实验结果表明, 该方法与人的认知结果吻合度很好, 算法是有效可行的。 相似文献
934.
935.
936.
TESTS FOR FRACTIONAL INTEGRATION:A MONTE CARLO INVESTIGATION 总被引:1,自引:0,他引:1
Abstract. The performance of the Geweke-Porter-Hudak (GPH) test, the modified rescaled range (MRR) test and two Lagrange multiplier (LM) type tests for fractional integration in small samples is examined using Monte Carlo methods. Both the GPH and MRR tests are found to be robust to moderate autoregressive moving-average components, autoregressive conditional heteroskedasticity effects and shifts in the variance. However, these two tests are sensitive to large autoregressive moving-average components and shifts in the mean. It is also found that the LM tests are sensitive to deviations from the null hypothesis. As an illustration, the GPH test is applied to two economic data series. 相似文献
937.
廖剑平 《网络安全技术与应用》2014,(6):189-190
本文围绕软件专业建设重点难点开展理论教学与实践教学研究,构建软件专业高职实训教学框架体系,通过实训内容项目化。强化实训环境建设,以力求实训效果职业化,从而使教学工作真正步入高等职业教育轨道,提高学生就业机会,实现人才培养目标。 相似文献
938.
939.
Yury V. Kissin 《Catalysis Letters》1993,19(2-3):181-187
An experimental technique is discussed for measuring relative reactivities of alkanes in the catalytic cracking of multi-component hydrocarbon mixtures over a heterogeneous, Y-zeolitebased catalyst at 250–350 °C. With the technique, ca. 0.1 l of an alkane mixture is evaporated and contacted with a catalyst, after which the mixture of reaction products and the unreacted feed enters the chromatographic column and is immediately analyzed. The technique is used to measure relative reactivities of 21 alkanes in a single experiment. The principal results of these experiments are similar to the results of single-component cracking: alkane reactivity rapidly increases with the increase of the carbon number, and methyl-branched alkanes are more reactive than linear alkanes. However, the variations in alkane reactivities as a function of their molecular weight and skeleton structure differ very significantly between single- and multicomponent experiments. 相似文献
940.
The reduction of NO
x
with propene or propane in the presence of 1 or 4% O2 was studied at low conversions over a 7.4 wt% Cu-ZrO2 and a 3.2 wt% Cu-ZSM-5 catalyst. The rates of N2 production were compared in experiments using only NO or a mixture of NO and NO2 in the feed. They were also compared with the rates of NO2 reduction to NO under the same conditions, and of NO oxidation to NO2 in the absence of hydrocarbon. It was found that the reduction of NO2 to NO was very fast, consistent with literature data. The data were best explained by a reaction scheme in which the hydrocarbon was activated primarily by reaction with adsorbed NO2 to form an adsorbed oxidized N-containing hydrocarbon intermediate, the reaction of which with NO was the principal route to produce N2 under lean NO
x
conditions.On leave from State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China. 相似文献