全文获取类型
收费全文 | 267961篇 |
免费 | 21705篇 |
国内免费 | 15234篇 |
专业分类
电工技术 | 35619篇 |
技术理论 | 22篇 |
综合类 | 30078篇 |
化学工业 | 23373篇 |
金属工艺 | 13277篇 |
机械仪表 | 20237篇 |
建筑科学 | 22619篇 |
矿业工程 | 10098篇 |
能源动力 | 8916篇 |
轻工业 | 10176篇 |
水利工程 | 7058篇 |
石油天然气 | 9230篇 |
武器工业 | 4339篇 |
无线电 | 24003篇 |
一般工业技术 | 17494篇 |
冶金工业 | 10111篇 |
原子能技术 | 2477篇 |
自动化技术 | 55773篇 |
出版年
2024年 | 933篇 |
2023年 | 2521篇 |
2022年 | 5160篇 |
2021年 | 6398篇 |
2020年 | 6803篇 |
2019年 | 5106篇 |
2018年 | 4823篇 |
2017年 | 6742篇 |
2016年 | 7798篇 |
2015年 | 9103篇 |
2014年 | 16539篇 |
2013年 | 14159篇 |
2012年 | 19625篇 |
2011年 | 20888篇 |
2010年 | 16031篇 |
2009年 | 16071篇 |
2008年 | 15685篇 |
2007年 | 20359篇 |
2006年 | 18319篇 |
2005年 | 16395篇 |
2004年 | 13469篇 |
2003年 | 12136篇 |
2002年 | 9420篇 |
2001年 | 7901篇 |
2000年 | 6558篇 |
1999年 | 5388篇 |
1998年 | 4066篇 |
1997年 | 3255篇 |
1996年 | 2897篇 |
1995年 | 2415篇 |
1994年 | 2016篇 |
1993年 | 1339篇 |
1992年 | 1156篇 |
1991年 | 811篇 |
1990年 | 617篇 |
1989年 | 502篇 |
1988年 | 363篇 |
1987年 | 209篇 |
1986年 | 123篇 |
1985年 | 128篇 |
1984年 | 109篇 |
1983年 | 95篇 |
1982年 | 75篇 |
1981年 | 72篇 |
1980年 | 58篇 |
1979年 | 49篇 |
1978年 | 34篇 |
1977年 | 29篇 |
1976年 | 24篇 |
1959年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
This paper presents a novel process for the fabrication of pultruded polyurethane (PU) composites. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) and thermal properties (HDT) of the fibre reinforced PU composites by pultrusion have been studied. The processing parameters investigated include pulling rate (in-line speed), die temperature, filler type and content, and post-cure time and temperature. Results show that the composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio, the mechanical properties and the thermal properties of composites, the optimum die temperature can be determined. It is found that the mechanical and thermal properties increase with filler content for various types of filler. The mechanical and thermal properties increase at a suitable post-cure temperature and time. Furthermore, the properties which decreased due to the degradation of composite materials for a long post-cure time will be discussed. 相似文献
52.
New small‐scale dispersed generation systems, such as fuel cells and micro gas turbines, have made remarkable advances lately and they will be applied practically in the near future. Although a large number of researches on the introduction of small‐scale dispersed generation systems have been carried out, only a small number of small‐scale dispersed generation systems are considered in these researches. Therefore, little is known about problems to be solved when a large number of small‐scale dispersed generation systems are introduced into electric power systems. This paper deals with a super‐distributed energy system that consists of a great number of dispersed generation systems such as fuel cells, micro gas turbines, and so on. The behavior of a customer with a dispersed generation system is simulated as the Ising model in statistical mechanics. The necessity of a distribution network in super‐distributed energy systems is discussed based on the Ising model. The feasibility of decentralized autonomous control using vicinity information is also investigated on the basis of stability analysis of the Hopfield neural network model. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(1): 43–55, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10368 相似文献
53.
SW233 PIN驱动器自动测试系统的研制 总被引:1,自引:0,他引:1
介绍了一种集成电路自动测试系统,该系统采用计算机并口作通信接口,用VB6编程,实现了对外围测试电路的控制,用IEEE-488接口卡控制测试仪器,可对SW233电路的36个参数进行自动测试,并将测试结果自动保存在数据库中。该测试系统具有自动化程度高、操作方便、测试结果精确等特点。 相似文献
54.
Motonobu Yoshikawa Hiroshi Nakajima Takeshi Inada Yasushi Harada Masahiko Amano Yuji Nakata 《Electrical Engineering in Japan》1995,115(7):29-39
A new practical method is proposed which gives a quasi-optimal solution of the dynamic load-dispatching problem formulated by a multiconstraint multiobjective optimization problem. Here, the multiple constraints are rate reserve constraints and power flow ones, and the multiple objectives are fuel cost and CO2 emission. The proposed method is an integration of the following three techniques: (1) “Group Dispatch Scheme,” which is developed by the authors, is used to satisfy a violated constraint easily. This scheme consists of three steps. The first step is to classify all generators into two groups. One is the group which should be more loaded to satisfy the violated constraint, and the other is the should-be less loaded group. The second step is to add some load to the former group, and to subtract the same load from the latter. The third step is to dispatch each group load to each groups generators, respectively; (2) the dynamic load-dispatching algorithm is used which provides, in practical time, quasi-optimal generation trajectories; (3) the conventional weighting parametric method is used to obtain a Pareto optimal solution of multiobjective problems. The effectiveness of the method is clarified by a computer simulation on the actual power system of Kansai Electric Power Company. 相似文献
55.
56.
小口径弹道炮在使用初期,弹道特性值偏高,影响产品的验收和标准弹的鉴选.该文用膛阻理论解释弹道炮使用的各个时期的弹道特性变化,并介绍了“光膛”射击后,在弹道曲线下降段进行产品验收以及标准弹鉴选中的实际应用. 相似文献
57.
Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern. 相似文献
58.
Hironori Oda 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):223-228
Fluorans are given considerable attention as functional dyes for heat-and/or pressure-sensitive recording media. Numerous potential metal complexes were synthesised to prolong the life of coloured species. The protecting effect of these compounds against the photofading was examined on cellulose. It was found that the zinc or nickel salts of 3,5-dihydroxy-2-naphthoic acid and its derivatives can be applied as effective stabilisers against the fading of fluoran dyes. 相似文献
59.
Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning. 相似文献
60.
本文介绍一种基于VME总线的高速A/D缓冲系统的原理和结构。着重阐述了高速数据采集技术,高速FIFO缓冲技术,存储器总线切换技术,VME及PC/ISA总线接口技术在本系统中的成功应用。 相似文献