全文获取类型
收费全文 | 40463篇 |
免费 | 3377篇 |
国内免费 | 1829篇 |
专业分类
电工技术 | 3245篇 |
技术理论 | 6篇 |
综合类 | 2870篇 |
化学工业 | 3764篇 |
金属工艺 | 1017篇 |
机械仪表 | 2127篇 |
建筑科学 | 10265篇 |
矿业工程 | 1861篇 |
能源动力 | 1491篇 |
轻工业 | 887篇 |
水利工程 | 944篇 |
石油天然气 | 3751篇 |
武器工业 | 291篇 |
无线电 | 2045篇 |
一般工业技术 | 2031篇 |
冶金工业 | 2413篇 |
原子能技术 | 175篇 |
自动化技术 | 6486篇 |
出版年
2024年 | 190篇 |
2023年 | 553篇 |
2022年 | 975篇 |
2021年 | 1182篇 |
2020年 | 1292篇 |
2019年 | 1035篇 |
2018年 | 925篇 |
2017年 | 1230篇 |
2016年 | 1384篇 |
2015年 | 1469篇 |
2014年 | 2899篇 |
2013年 | 3234篇 |
2012年 | 2798篇 |
2011年 | 3039篇 |
2010年 | 2286篇 |
2009年 | 2385篇 |
2008年 | 2129篇 |
2007年 | 2522篇 |
2006年 | 2314篇 |
2005年 | 1954篇 |
2004年 | 1603篇 |
2003年 | 1395篇 |
2002年 | 1267篇 |
2001年 | 1079篇 |
2000年 | 859篇 |
1999年 | 708篇 |
1998年 | 525篇 |
1997年 | 448篇 |
1996年 | 368篇 |
1995年 | 363篇 |
1994年 | 273篇 |
1993年 | 204篇 |
1992年 | 153篇 |
1991年 | 128篇 |
1990年 | 106篇 |
1989年 | 73篇 |
1988年 | 48篇 |
1987年 | 50篇 |
1986年 | 26篇 |
1985年 | 49篇 |
1984年 | 36篇 |
1983年 | 34篇 |
1982年 | 22篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Andrea Engl Benno Kunz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):257-261
Studies took place to investigate the effects of different nutrient conditions on the biosorption ability and selectivity of heavy metals by Saccharomyces cerevisiae. After having grown in media supplemented with additional glucose, ammonium, phosphate or cysteine, the yeast was exposed to an equimolar solution of lead, cadmium, zinc and copper. Lead removal from a mixed solution was significantly higher than that of copper, followed by zinc and cadmium. Generally, yeasts from cysteine-rich media showed greatest sorption capacity whereas phosphate addition influenced zinc selectivity. In addition, glucose, fructose and sucrose as carbon sources were examined. Cultures grown in glucose had a better uptake than those cultivated with fructose at an incubation time of 30 min. 相似文献
52.
In the history of operations research in industry there has been an abundance of analyses and recommendations produced in millions of man hours by dedicated OR specialists. And yet the net improvement is significantly lower than expected. There are numerous reasons for this shortfall: incomplete analysis, too much theory, incomplete implementation, unreliable recommendations, or a combination of some of these reasons.
By describing several examples, the major reasons for the fragility of the link between recommendation and implementation will be reviewed. What has to be done today to increase the likelihood of implementing an OR recommendation and thus improve the performance of an industrial entity by using the power of OR tools will then be described. 相似文献
By describing several examples, the major reasons for the fragility of the link between recommendation and implementation will be reviewed. What has to be done today to increase the likelihood of implementing an OR recommendation and thus improve the performance of an industrial entity by using the power of OR tools will then be described. 相似文献
53.
从烧结矿冷却并回收其余热的角度出发,介绍了利用烧结机尾落矿空间,采用喷吹空气装置对烧结矿进行冷却的小型模拟试验,从测出的结果来看,有可能成为一种新的烧结矿冷却方式。 相似文献
54.
55.
“To understand and protect our home planet, to explore the universe and search for life, and to inspire the next generation of explorers” is NASA's mission. The Systems Management Office at Johnson Space Center (JSC) is searching for methods to effectively manage the Center's resources to meet NASA's mission. D-Side is a group multi-criteria decision support system (GMDSS) developed to support facility decisions at JSC. D-Side uses a series of sequential and structured processes to plot facilities in a three-dimensional (3-D) graph on the basis of each facility's alignment with NASA's mission and goals, the extent to which other facilities are dependent on the facility, and the dollar value of capital investments that have been postponed at the facility relative to the facility's replacement value. A similarity factor rank orders facilities based on their Euclidean distance from Ideal and Nadir points. These similarity factors are then used to allocate capital improvement resources across facilities. We also present a parallel model that can be used to support decisions concerning allocation of human resources investments across workforce units. Finally, we present results from a pilot study where 12 experienced facility managers from NASA used D-Side and the organization's current approach to rank order and allocate funds for capital improvement across 20 facilities. Users evaluated D-Side favorably in terms of ease of use, the quality of the decision-making process, decision quality, and overall value-added. Their evaluations of D-Side were significantly more favorable than their evaluations of the current approach. 相似文献
56.
A genetic algorithm for the optimisation of assembly sequences 总被引:6,自引:0,他引:6
This paper describes a Genetic Algorithm (GA) designed to optimise the Assembly Sequence Planning Problem (ASPP), an extremely diverse, large scale and highly constrained combinatorial problem. The modelling of the ASPP problem, which has to be able to encode any industrial-size product with realistic constraints, and the GA have been designed to accommodate any type of assembly plan and component. A number of specific modelling issues necessary for understanding the manner in which the algorithm works and how it relates to real-life problems, are succinctly presented, as they have to be taken into account/adapted/solved prior to Solving and Optimising (S/O) the problem. The GA has a classical structure but modified genetic operators, to avoid the combinatorial explosion. It works only with feasible assembly sequences and has the ability to search the entire solution space of full-scale, unabridged problems of industrial size. A case study illustrates the application of the proposed GA for a 25-components product. 相似文献
57.
时效处理对 TiNi 合金相变与性能的影响 总被引:2,自引:0,他引:2
通过用TEM等方法研究热处理制度(固溶处理、时效处理)对TiNi合金相变组织和性能的影响,找出了最佳热处理制度。结果表明,在450~500℃进行时效处理,Ti-50.8at%Ni的合金出现了大量的Ti3Ni4相,且恢复率最高。 相似文献
58.
用于疏通油水井的脉冲放电技术 总被引:1,自引:0,他引:1
评价了各种不同的解堵技术,指出冲击波解堵是一种很有发展前途的技术。介绍了液中脉冲放电产生冲击波的基本原理,并由此研制出了一套井下脉冲放电油水井处理设备样机。通过现场试验,表明用冲击波疏通油井能较好地解除油井污染,提高采收率。 相似文献
59.
电子商务环境下企业资源计划(ERP)的新进展 总被引:8,自引:0,他引:8
分析了在电子商务环境下企业资源计划 (ERP)需求的新特点 ,并结合ERP发展和实际应用中存在的问题 ,论述了ERP与电子商务集成化的发展方向 ,提出了企业关系管理 (ERM )的基本框架和建立商业网络 (BN)的必要性。同时 ,还论述了ERP系统在网络化、模块化和智能化的发展方向和最新进展。 相似文献
60.
Reinhard Effenberger 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,58(2):129-133
The preparation of 2,6-dibromophenol is described. This compound, useful as raw material for brominated poly(phenyleneoxide) and pyrogallol or derived pharmaceuticals/pesticides, was prepared in 80% (isolated) yield by a transalkylation reaction between tetrabromobisphenol-A and toluene. The catalyst, trifluoromethanesulphonic acid, can be simply recovered and recycled. Perfluorinated resin sulphonic acid (NAFION-H®, DuPont) did not effectively catalyse this transalkylation. 相似文献