全文获取类型
收费全文 | 64987篇 |
免费 | 10511篇 |
国内免费 | 5637篇 |
专业分类
电工技术 | 11258篇 |
技术理论 | 4篇 |
综合类 | 7219篇 |
化学工业 | 3596篇 |
金属工艺 | 2028篇 |
机械仪表 | 4741篇 |
建筑科学 | 9801篇 |
矿业工程 | 3138篇 |
能源动力 | 3469篇 |
轻工业 | 3845篇 |
水利工程 | 3092篇 |
石油天然气 | 3114篇 |
武器工业 | 733篇 |
无线电 | 4628篇 |
一般工业技术 | 4582篇 |
冶金工业 | 2482篇 |
原子能技术 | 470篇 |
自动化技术 | 12935篇 |
出版年
2024年 | 422篇 |
2023年 | 1331篇 |
2022年 | 2566篇 |
2021年 | 2902篇 |
2020年 | 3125篇 |
2019年 | 2493篇 |
2018年 | 2309篇 |
2017年 | 2760篇 |
2016年 | 2896篇 |
2015年 | 3156篇 |
2014年 | 4623篇 |
2013年 | 4001篇 |
2012年 | 5294篇 |
2011年 | 5608篇 |
2010年 | 4299篇 |
2009年 | 4253篇 |
2008年 | 3872篇 |
2007年 | 4432篇 |
2006年 | 3741篇 |
2005年 | 3118篇 |
2004年 | 2507篇 |
2003年 | 2115篇 |
2002年 | 1695篇 |
2001年 | 1403篇 |
2000年 | 1204篇 |
1999年 | 1026篇 |
1998年 | 671篇 |
1997年 | 580篇 |
1996年 | 536篇 |
1995年 | 440篇 |
1994年 | 372篇 |
1993年 | 259篇 |
1992年 | 180篇 |
1991年 | 152篇 |
1990年 | 157篇 |
1989年 | 132篇 |
1988年 | 105篇 |
1987年 | 67篇 |
1986年 | 38篇 |
1985年 | 38篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 9篇 |
1966年 | 8篇 |
1964年 | 14篇 |
1959年 | 11篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
本文从盘锦地区1987-1993年电力负荷的原始资料入手,运用移动平均并加以改良的方法,从具有季节性变化的电力负荷系列中,分离出季节性分量,提示了电力负荷发展变化的规律。文中分析了盘锦地区七年间电力负荷发展的自身特点,指出其循环变化的转折点,给出了未来近期负荷变化的趋势,为电力行业制定规划和组织生产提供了依据,对供电企业合理安排生产计划、适应市场经济带来启示。 相似文献
102.
爆破条件对爆破震动信号分析中小波包时频特征的影响 总被引:10,自引:2,他引:8
非平稳信号的小波包分析是在小波变换基础上发展起来的 ,它对小波分析中没有细分的高频部分进一步分解 ,从而能够对信号局部信息进行更为精细的掌握。爆破条件是影响爆破震动时频特征分布的主要因素之一。本研究中 ,针对在不同段药量、不同微差间隔时间及近似相同的其它条件下产生的爆破震动信号 ,运用小波包分析方法对其进行了时频分析 ,主要探讨了段药量、段微差间隔时间对爆破震动时频分布的影响规律。段药量对爆破震动波形时频特征的影响主要体现在各层小波包主振频带内的细节信号峰值质点振速方面 ,各细节信号的峰值质点振速随段药量增加而增大 ,但主振频带分布保持基本的一致性 ,同一主振频带下小波包细节信号的阻尼比也趋于一致 ;段微差时间间隔对爆破震动时频特征的影响主要表现在 :延长各主振频带小波包细节信号的振动持时 ,不同微差单段波形的叠加增加了主振频带个数 (优势频率个数 )并使各频带内的优势频率值有微弱增大的趋势 相似文献
103.
104.
文章论述了井塔拆除爆破中,把框架承重立柱的裸露钢筋骨架失稳看作为压杆失稳以及井塔在倾斜撞地时下部不解体破坏的估算。 相似文献
105.
106.
The conventional way of solving the group technology (GT) problem is to start from an assignment of parts to machines and try to find a partitioning of machine cells and part families. The similarity between parts is measured based on commonality of the machines assigned to them. However, parts are assigned to machines based on their operation requirements and the operation capabilities of machines. Similarity between parts should be based on their required operations. In this paper, the authors attempt to solve or facilitate solving the GT problem at the assignment level. An algorithm for assigning parts to machines is provided which utilizes the types of operations required by parts and applies GT principles in producing the assignment. This leads to better partitioning of machine cells and part-families. Furthermore, operation sequences required by parts in determining the similarity between parts have been considered. An algorithm to form part-families based on the operation sequence similarity coefficient has been developed. The resulting families are then used by the assignment algorithm to produce machine assignments to part-families. The use of the algorithm is demonstrated by examples. 相似文献
107.
Thomas L. Landers Melinda K. Beavers Malik Sadiq Don E. Stuart 《Computers & Industrial Engineering》1994,27(1-4):245-248
This paper describes an approach, conceptual framework, and software architecture for dynamic reconfiguration of the order picking system. The research and development project was sponsored by the Material Handling Research Center (MHRC), a National Science Foundation sponsored Cooperative Industry/University Research Center. The storage configuration is assumed to be an in-the-aisle order picking system in which stockkeeping units (SKUs) can occupy variable capacity storage locations and stock-splitting is allowed among zones (clusters). The product mix may include multiple product families with different life cycles, correlated demand within families and commonality of demand across families. 相似文献
108.
Li Yonghua Wang Chunbo Chen Hongwei 《Frontiers of Energy and Power Engineering in China》2007,1(1):96-100
Power plants in China have to burn blended coal instead of one specific coal for a variety of reasons. So it is of great necessity
to investigate the combustion of blended coals. Using a test rig with a capacity of 640 MJ/h with an absolute milling system
and flue gas online analysis system, characteristics such as burnout, slag, and pollution of some blended coals were investigated.
The ratio of coke and slag as a method of distinguishing coal slagging characteristic was introduced. The results show that
the blending of coal has some effect on NO
x
but there is no obvious rule. SO
x
emission can be reduced by blending low sulfur coal.
Translated from Proceedings of the CSEE, 2005, 25(18): 97–103 [译自: 中国电机工程学报] 相似文献
109.
Marsch Lisa A.; Stephens Mary Ann Chutuape; Mudric Timothy; Strain Eric C.; Bigelow George E.; Johnson Rolley E. 《Canadian Metallurgical Quarterly》2005,13(4):293
This study examined (1) predictors of treatment outcome for opioid-dependent participants in a single-site controlled trial comparing methadone, buprenorphine, and LAAM treatments and (2) the extent to which various subpopulations of patients may have more successful outcomes with each medication. The relationships between patient demographics, drug use history, and psychological status and outcome measures of treatment retention, opiate use, and cocaine use were assessed. We believe this study to be the first to demonstrate that predictors of treatment success appear to be largely similar in LAAM, buprenorphine, and methadone treatment for opioid dependence. We did not find any factors that would strongly guide selection of one medication over others. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.
连续蒸煮器内洗涤结合器外扩散洗涤,具有洗涤时间长、洗涤效率高、提取黑液浓度高、浆层厚度均匀、浆层结构组织和浓度一致等特点,运行可靠,易于自动化控制,实现了洗涤用水的封闭循环。 相似文献