全文获取类型
收费全文 | 4457篇 |
免费 | 225篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 54篇 |
综合类 | 3篇 |
化学工业 | 950篇 |
金属工艺 | 86篇 |
机械仪表 | 67篇 |
建筑科学 | 268篇 |
矿业工程 | 4篇 |
能源动力 | 198篇 |
轻工业 | 471篇 |
水利工程 | 30篇 |
石油天然气 | 9篇 |
无线电 | 384篇 |
一般工业技术 | 822篇 |
冶金工业 | 416篇 |
原子能技术 | 32篇 |
自动化技术 | 898篇 |
出版年
2023年 | 44篇 |
2022年 | 66篇 |
2021年 | 124篇 |
2020年 | 83篇 |
2019年 | 99篇 |
2018年 | 109篇 |
2017年 | 102篇 |
2016年 | 139篇 |
2015年 | 125篇 |
2014年 | 159篇 |
2013年 | 284篇 |
2012年 | 287篇 |
2011年 | 342篇 |
2010年 | 296篇 |
2009年 | 265篇 |
2008年 | 276篇 |
2007年 | 240篇 |
2006年 | 206篇 |
2005年 | 177篇 |
2004年 | 155篇 |
2003年 | 135篇 |
2002年 | 120篇 |
2001年 | 59篇 |
2000年 | 74篇 |
1999年 | 53篇 |
1998年 | 64篇 |
1997年 | 53篇 |
1996年 | 55篇 |
1995年 | 43篇 |
1994年 | 51篇 |
1993年 | 34篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 29篇 |
1988年 | 17篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有4692条查询结果,搜索用时 15 毫秒
11.
This study examines the links between antecedents and consequences of Gabonese teachers' (N= 152) work motivation. The theoretical underpinnings are based on the Motivational Model of Job Burnout (MMJB) which is grounded in Self-Determination Theory (SDT) and states that the more supervisors satisfy an employee's need for self-determination, competence, and relatedness, the more self-determined is the latter's work motivation. The level of self-determined motivation has an impact on job satisfaction, which in turn determines life satisfaction. Higher levels of self-determined motivation also buffer emotional exhaustion and psychological distress. The model was confirmed via structural equation modeling and provides support for the validity and generalizability of the MMJB and SDT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Huseyin Selcuk Jeosadaque J Sene Marc A Anderson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(9):979-984
This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10?1 min?1, 8.3 × 10?2 min?1 and 2.49 × 10?2 min?1 (R2 > 0.97) for UV254 degradation and 1.7 × 10?1 min?1, 6.5 × 10?2 min?1 and 2.0 × 10?2 min?1 for color removal from 5 mg dm?3, 10 mg dm?3 and 25 mg dm?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry 相似文献
13.
Marc Dubreuil Christian Gagné Marc Parizeau 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(1):229-235
This paper introduces a new mathematical model of the master-slave architecture for distributed evolutionary computations (EC). This model is validated using a concrete implementation based on the Distributed BEAGLE C++ framework. Results show that contrary to (current) popular belief, master-slave architectures are able to scale well over local area networks of workstations using off-the-shelf networking equipment. The main properties of the master-slave are also compared with those of the more mainstream island-model. 相似文献
14.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined. 相似文献
15.
Thermodynamic analysis of solar photovoltaic cell systems 总被引:1,自引:0,他引:1
Ahmet Duran Sahin Ibrahim Dincer Marc A. Rosen 《Solar Energy Materials & Solar Cells》2007,91(2-3):153-159
The thermodynamic characteristics of solar photovoltaic (PV) cells are investigated from a perspective based on exergy. A new efficiency is developed that is useful in studying PV performance and possible improvements. Exergy analysis is applied to a PV system and its components, and exergy flows, losses and efficiencies are evaluated. Energy efficiency is seen to vary between 7% and 12% during the day. In contrast, exergy efficiencies, which incorporate the second law of thermodynamics and account for solar irradiation exergy values, are lower for electricity generation using the considered PV system, ranging from 2% to 8%. Values of “fill factors” are determined for the system and observed to be similar to values of exergy efficiency. 相似文献
16.
这个综合学校包括一个主建筑,一个体育馆和各种户外设施,朝向一片处在前军事基地上的住宅开发区。整个主建筑沿纵向被一个由顶部采光的回廊从中间分开,由此可以进入两侧的教室,回廊局部变宽的部分构成一个公共空间。这个构想与将城市设计理论运用于建筑内部设计的概念相符合:街道、广场和建筑被看成了建筑内部空间部分。虽然这个建筑从外部看来是个大体块,但内部空间却设计流畅,通道有的通向楼层的各个角落,也有的依着倾斜的地势因势而建。由墙面反射的散射光线加强了内部空间的肃穆和厚重感。在具有宗教感的整体风格下,整个学校的设计和装饰也显得古香古色,如一部宽阔的观光楼梯、两个塔形和壁炉形的建筑构成元素等。不同历史风格建筑的叠加给这个校区带来一种复杂的味道,堪比阿尔多·罗西(Aldo Rossi)的设计或泰辛(Tessin)新理性主义的代表作。 相似文献
17.
Abstract. A sufficient condition for the invertibility of univariate periodic moving-average models has been given by Cipra and Ghysels and Hall. We show that this condition is not a necessary one, and provide a necessary and sufficient condition for the general m -variate, d -periodical moving-average MA( q ) case. 相似文献
18.
Marc D. Hein 《乙烯基与添加剂工艺杂志》1994,16(4):208-212
The performance standards for flexible PVC compounds continue to become more demanding as manufacturers pursue more value-added applications traditionally dominated by rubbers and thermoplastic elastomers. Blending of PVC with other polymers has proven to be a viable approach in developing higher performance flexible PVC-based materials. This paper will review some of the typical approaches to producing PVC-based elastomers, and show how these standard flexible PVC blends compare to a newly developed family of PVC alloys. The advantages of these materials will be discussed, and some examples of commercial materials and their application will also be reviewed. 相似文献
19.
20.