全文获取类型
收费全文 | 40173篇 |
免费 | 4523篇 |
国内免费 | 3580篇 |
专业分类
电工技术 | 2137篇 |
技术理论 | 2篇 |
综合类 | 3252篇 |
化学工业 | 1895篇 |
金属工艺 | 1203篇 |
机械仪表 | 2595篇 |
建筑科学 | 2272篇 |
矿业工程 | 1687篇 |
能源动力 | 1100篇 |
轻工业 | 883篇 |
水利工程 | 1519篇 |
石油天然气 | 3019篇 |
武器工业 | 488篇 |
无线电 | 3993篇 |
一般工业技术 | 2464篇 |
冶金工业 | 1450篇 |
原子能技术 | 338篇 |
自动化技术 | 17979篇 |
出版年
2024年 | 286篇 |
2023年 | 857篇 |
2022年 | 1485篇 |
2021年 | 1570篇 |
2020年 | 1528篇 |
2019年 | 1203篇 |
2018年 | 1116篇 |
2017年 | 1322篇 |
2016年 | 1558篇 |
2015年 | 1510篇 |
2014年 | 2440篇 |
2013年 | 2157篇 |
2012年 | 2559篇 |
2011年 | 2974篇 |
2010年 | 2122篇 |
2009年 | 2189篇 |
2008年 | 2328篇 |
2007年 | 2739篇 |
2006年 | 2524篇 |
2005年 | 2331篇 |
2004年 | 2031篇 |
2003年 | 1859篇 |
2002年 | 1412篇 |
2001年 | 1133篇 |
2000年 | 865篇 |
1999年 | 759篇 |
1998年 | 586篇 |
1997年 | 497篇 |
1996年 | 425篇 |
1995年 | 381篇 |
1994年 | 278篇 |
1993年 | 197篇 |
1992年 | 145篇 |
1991年 | 132篇 |
1990年 | 104篇 |
1989年 | 99篇 |
1988年 | 76篇 |
1987年 | 54篇 |
1986年 | 47篇 |
1985年 | 46篇 |
1984年 | 42篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 40篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 32篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Ye. L. Stolov 《Journal of Electronic Testing》1993,4(3):283-283
Let a circuit havem outputs,m>1. There are two ways to test this circuit by means of a signature analyzer: use a single input analyzer for each output or use anm-input analyzer to test all outputs simultaneously. The main goal of this letter is to demonstrate that for fault output sequences with small multiplicity of errors and long length the second approach is more effective. 相似文献
32.
以地震资料精细处理和解释在大庆长垣外围徐家围子油田开发中的成功应用为例,论述了地震地质综合描述技术在地质情况复杂的低、特低渗透油田开发中的应用效果。 相似文献
33.
Michael E. G. Ferguson Peter L. Spedding 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):262-278
Experimental data for air–water two-phase co-current flow in two different pipe diameters were used to test the prediction of pressure drop by a number of existing theories and correlations. Several models are shown to be useful for prediction, particularly with the stratified regimes which have proved difficult to handle in the past. The model suggested by Olujic proved to be of particular value. 相似文献
34.
杜社教 《小型微型计算机系统》1994,15(12):34-40
本文分析讨论了在MS-Windows操作系统下的应用程序间的数据交换的概念及方法,并给出了这些方法的选用策略。这些方法包括裁剪板,动态数据交换(DDE),对象的连接及嵌入(OLE),动态连接库(DLL)。 相似文献
35.
Computational complexity of queries based on itemsets 总被引:1,自引:0,他引:1
Nikolaj Tatti 《Information Processing Letters》2006,98(5):183-187
We investigate determining the exact bounds of the frequencies of conjunctions based on frequent sets. Our scenario is an important special case of some general probabilistic logic problems that are known to be intractable. We show that despite the limitations our problems are also intractable, namely, we show that checking whether the maximal consistent frequency of a query is larger than a given threshold is NP-complete and that evaluating the Maximum Entropy estimate of a query is PP-hard. We also prove that checking consistency is NP-complete. 相似文献
36.
37.
U. Reimer
H. -J. Schek
《Data & Knowledge Engineering》1989,4(4):321-352The first part of this paper introduces the basic constructs of a frame representation model and gives a formal definition for them. Subsequently the nested relational model (NF2) is described as an extension of the classical relational model to support relation-valued attributes. In the second part of this paper both models are compared with each other and a mapping of frame representation structures to NF2 structures is specified. The structural similarities between frames and NF2 relations are made clear and it is shown that their main difference is due to the type polymorphism introduced by the concept hierarchy of the frame model. This causes type collisions to occur in the strictly typed NF2 model when frames are directly mapped to NF2 structures. Two solutions to this problem are suggested and compared. The paper concludes with a reformulation of query operations of the frame model in terms of NF2 algebra operations. 相似文献
38.
Koenen Karestan C.; Stellman Jeanne Mager; Stellman Steven D.; Sommer John F. Jr. 《Canadian Metallurgical Quarterly》2003,71(6):980
Risk factors affecting the course of posttraumatic stress disorder (PTSD) are poorly understood. As part of a larger study on characterizing exposure to herbicides in Vietnam, the authors investigated this issue in a random sample of 1,377 American Legionnaires who had served in Southeast Asia during the Vietnam War and were followed over a 14-year period. High combat exposure, perceived negative community attitudes at homecoming, minority race, depression symptoms at Time 1, and more anger at Time 1 predicted a more chronic course. Community involvement at Time 1 was protective and associated with decreased risk at Time 2. Discomfort in disclosing Vietnam experiences was associated with an increased risk for developing PTSD but did not predict its course. Combat exposure predicted PTSD course more strongly than any other risk factor. Findings suggest recovery from PTSD is significantly influenced by perceived social support. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.