全文获取类型
收费全文 | 366799篇 |
免费 | 30434篇 |
国内免费 | 22174篇 |
学科分类
工业技术 | 419407篇 |
出版年
2024年 | 1376篇 |
2023年 | 3678篇 |
2022年 | 6782篇 |
2021年 | 8436篇 |
2020年 | 9516篇 |
2019年 | 7139篇 |
2018年 | 6460篇 |
2017年 | 9291篇 |
2016年 | 10712篇 |
2015年 | 12333篇 |
2014年 | 23774篇 |
2013年 | 20317篇 |
2012年 | 26848篇 |
2011年 | 28757篇 |
2010年 | 21822篇 |
2009年 | 22002篇 |
2008年 | 22214篇 |
2007年 | 27834篇 |
2006年 | 24986篇 |
2005年 | 22077篇 |
2004年 | 18202篇 |
2003年 | 16344篇 |
2002年 | 12781篇 |
2001年 | 10637篇 |
2000年 | 8915篇 |
1999年 | 7193篇 |
1998年 | 5453篇 |
1997年 | 4652篇 |
1996年 | 3907篇 |
1995年 | 3240篇 |
1994年 | 2715篇 |
1993年 | 1880篇 |
1992年 | 1564篇 |
1991年 | 1159篇 |
1990年 | 908篇 |
1989年 | 773篇 |
1988年 | 561篇 |
1987年 | 333篇 |
1986年 | 221篇 |
1985年 | 231篇 |
1984年 | 242篇 |
1983年 | 207篇 |
1982年 | 171篇 |
1981年 | 125篇 |
1980年 | 100篇 |
1979年 | 94篇 |
1978年 | 70篇 |
1977年 | 66篇 |
1976年 | 28篇 |
1959年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
软件构件技术在管理信息系统中的应用 总被引:2,自引:1,他引:1
翟广宇 《兰州工业高等专科学校学报》2004,11(3):35-38
软件构件技术是一种前沿的软件设计思想,其方法与传统的软件制作方法有很大区别.通过介绍软件构件技术在开发管理信息系统的应用,与其它软件制作方法进行比较,得出这样的结论:在软件编制中应用这种思想,不仅能大幅度地加快软件的开发速度,而且对整个软件行业的发展有着至关重要的推动作用。 相似文献
132.
Technology can take many forms from the development of sophisticated electronics to the application of basic procedural principles. Technology transfer can also take several forms, however, in this case, it is the transfer of technological principles between application domains that is of primary interest. This paper presents a framework (the Five ‘M’s framework) that can be used to consider the likely success of technology transfer. The framework is based upon a sociotechnical system approach. The framework is illustrated with an evaluation of the introduction of intelligent cruise control into motor vehicles. It is argued that this is a technological concept first developed as an aerospace application in the form of the autopilot. In this case, it is argued that the transfer of this technology in its current form may potentially compromise safety. 相似文献
133.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
134.
介绍了钻孔灌注桩成孔质量的影响因素 ,详细叙述了钢筋笼的制作和吊放处理步骤 ,阐述了断桩发生的原因 ,提出了具体的防治措施 ,经实践效果良好 相似文献
135.
Fluctuations and waves in fluidized bed systems: The influence of the air-supply system 总被引:1,自引:0,他引:1
Srdjan Sasic 《Powder Technology》2005,153(3):176-195
A general model of the response of a fluidized bed to disturbances is formulated, and the information provided by the model with respect to the dynamics of the bed, the bed plus the air-plenum and the bed plus the entire air-supply system, is investigated. Expressions given in literature on the fundamental frequency of the bed-plenum system are analyzed, and it is shown that they are a special case of the general model. In order to simulate various types of interaction between the bed and the rest of the system, experiments were performed in a cold fluidized bed unit operated under both non-circulating and circulating conditions. At low velocity, three regimes were identified: the multiple bubble regime with almost no interaction between bed and air-plenum, the single bubble regime with the interaction between bed and air-plenum only, and a regime with numerous irregular bubbles, where the bed interacted with the entire air-supply system. At high fluidization velocity, the exploding bubble regime was identified, with the same dominant frequency as that of the single bubble regime (the interaction with the air-supply system remains at that frequency). The models investigated correctly reproduce the dynamics when the bed is independent of the other parts of the system, or when the bed interacts only with the air-plenum. However, the models are only partially applicable when the bed interacts with the entire air-supply system. The reasons for this are investigated. In the case of system interaction, pressure waves, generated in the bed, interact with pressure pulsations from the air-supply system. This results in a coupled system, which is not covered by the models. Pressure waves resulting from events in the bed, are recognized as the coherent part of the cross power spectra of pressure fluctuations measured in the bed and the air-plenum. 相似文献
136.
Generalized difference control of parallel streams temperatures 总被引:1,自引:0,他引:1
A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes. 相似文献
137.
The objective of this note is to propose a method for stabilization of structurally fixed modes in expansions of LTI dynamic systems in the scope of overlapping decentralized control design based on the expansion/contraction framework, enabling successful design for a broader class of problems than considered so far. The method is based on a judicious choice of complementary matrices in the expanded space. Numerical examples are provided to illustrate simplicity and efficiency of the proposed approach. 相似文献
138.
基于MAPINFO和VB的自来水管网信息系统的建立 总被引:2,自引:0,他引:2
介绍基于MapInfo平台,利用VB语言进行二次开发,建立自来水管网地理信息系统的关键技术及其注意的问题。 相似文献
139.
140.
介绍了房地产企业项目进度控制的重要性,从事前、事中、事后三个阶段探讨了工程进度的控制,以保证房地产企业的项目顺利完工,从而保证建筑物的施工质量,提高房地产企业的竞争力。 相似文献