全文获取类型
收费全文 | 662458篇 |
免费 | 115539篇 |
国内免费 | 82660篇 |
专业分类
电工技术 | 69916篇 |
综合类 | 74874篇 |
化学工业 | 79591篇 |
金属工艺 | 58152篇 |
机械仪表 | 41533篇 |
建筑科学 | 48370篇 |
矿业工程 | 33531篇 |
能源动力 | 19494篇 |
轻工业 | 73819篇 |
水利工程 | 24419篇 |
石油天然气 | 29322篇 |
武器工业 | 10403篇 |
无线电 | 76979篇 |
一般工业技术 | 65286篇 |
冶金工业 | 28110篇 |
原子能技术 | 9532篇 |
自动化技术 | 117326篇 |
出版年
2024年 | 5556篇 |
2023年 | 12020篇 |
2022年 | 24216篇 |
2021年 | 30181篇 |
2020年 | 25465篇 |
2019年 | 26410篇 |
2018年 | 28233篇 |
2017年 | 32285篇 |
2016年 | 30333篇 |
2015年 | 38250篇 |
2014年 | 43342篇 |
2013年 | 47750篇 |
2012年 | 56341篇 |
2011年 | 55612篇 |
2010年 | 52817篇 |
2009年 | 48524篇 |
2008年 | 48153篇 |
2007年 | 46622篇 |
2006年 | 39530篇 |
2005年 | 32408篇 |
2004年 | 27014篇 |
2003年 | 18727篇 |
2002年 | 17671篇 |
2001年 | 15857篇 |
2000年 | 13335篇 |
1999年 | 7378篇 |
1998年 | 4865篇 |
1997年 | 4180篇 |
1996年 | 3854篇 |
1995年 | 3832篇 |
1994年 | 3127篇 |
1993年 | 2930篇 |
1992年 | 2750篇 |
1991年 | 2048篇 |
1990年 | 1637篇 |
1989年 | 1564篇 |
1988年 | 1148篇 |
1987年 | 407篇 |
1986年 | 375篇 |
1985年 | 262篇 |
1984年 | 180篇 |
1983年 | 157篇 |
1982年 | 187篇 |
1981年 | 253篇 |
1980年 | 243篇 |
1979年 | 143篇 |
1976年 | 381篇 |
1975年 | 206篇 |
1972年 | 236篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
11.
12.
Tatsuya Hanaoka Hisashi Ishitani Ryuji Matsuhashi Yoshikuni Yoshida 《Applied Energy》2002,72(3-4):705-721
The objective of this study is to evaluate the potential for recovering fluorocarbons as measures for the abatement of global warming. In this study, we focused on the three different kinds of fluorocarbons: CFCs, HCFCs and HFCs, and targeted refrigerant use because of the availability of relevant data. We first estimated future fluorocarbon emissions from the targeted appliances; we next compared those emissions in the units of CO2 equivalent to the level of CO2 emissions in 1990 from a quantitative point of view. As the result of this study, it was found that fluorocarbon emissions in 1999 and 2010 would be equal to approximately 7 and 3% of the level of CO2 emissions in 1990 respectively. Moreover, if we implement a 100% recovery rate in every recovery route, we can reduce a large amount of emissions which correspond to approximately 2–5% of the level of CO2 emissions in 1990, even if we take into account the energy-related CO2 emissions by the transportation and decomposition of fluorocarbons. 相似文献
13.
本文研究了HPMBP与伯胺N_(1923)的二甲苯溶液,从盐酸介质中协同萃取希土(Ⅲ)的机理。用斜率法、恒摩尔法确定了协萃配合物的组成为:RNH_3Ln(PMBP)_4。求得关于Pr(Ⅲ)协萃反应的平衡常数及协萃配合物的生成常数分别为:logK_(12)=-1.95;logβ_(12)=3.94。实验发现,协萃系数(R)随希土元素的原子序数(Z)递变而呈现“双峰效应”。还研究了协萃配合物的IR,NMR谱。 相似文献
14.
15.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at 相似文献
16.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
17.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples. 相似文献
18.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献
19.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
20.
Timothy Thomasma Kurt Hilbrecht 《International Journal of Flexible Manufacturing Systems》1991,3(3-4):231-250
Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models. 相似文献