全文获取类型
收费全文 | 34626篇 |
免费 | 2934篇 |
国内免费 | 1442篇 |
专业分类
电工技术 | 1219篇 |
技术理论 | 4篇 |
综合类 | 3820篇 |
化学工业 | 3284篇 |
金属工艺 | 730篇 |
机械仪表 | 1170篇 |
建筑科学 | 11872篇 |
矿业工程 | 1664篇 |
能源动力 | 885篇 |
轻工业 | 2375篇 |
水利工程 | 1793篇 |
石油天然气 | 921篇 |
武器工业 | 259篇 |
无线电 | 1655篇 |
一般工业技术 | 2026篇 |
冶金工业 | 1300篇 |
原子能技术 | 171篇 |
自动化技术 | 3854篇 |
出版年
2024年 | 169篇 |
2023年 | 536篇 |
2022年 | 930篇 |
2021年 | 1095篇 |
2020年 | 1111篇 |
2019年 | 848篇 |
2018年 | 717篇 |
2017年 | 931篇 |
2016年 | 1042篇 |
2015年 | 1170篇 |
2014年 | 2476篇 |
2013年 | 1981篇 |
2012年 | 2369篇 |
2011年 | 2600篇 |
2010年 | 2245篇 |
2009年 | 2274篇 |
2008年 | 2069篇 |
2007年 | 2552篇 |
2006年 | 2202篇 |
2005年 | 1853篇 |
2004年 | 1539篇 |
2003年 | 1357篇 |
2002年 | 1201篇 |
2001年 | 885篇 |
2000年 | 719篇 |
1999年 | 521篇 |
1998年 | 353篇 |
1997年 | 263篇 |
1996年 | 216篇 |
1995年 | 150篇 |
1994年 | 126篇 |
1993年 | 108篇 |
1992年 | 86篇 |
1991年 | 57篇 |
1990年 | 60篇 |
1989年 | 36篇 |
1988年 | 31篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1971年 | 3篇 |
1966年 | 3篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
通过对铸造湿型小件产品缺陷典型实例的原因分析,从型砂的选择及配制、造型工艺、浇注工艺等方面提出控制缺陷产生的工艺方法。 相似文献
42.
Environment as a first class abstraction in multiagent systems 总被引:2,自引:1,他引:1
The current practice in multiagent systems typically associates the environment with resources that are external to agents and their communication infrastructure. Advanced uses of the environment include infrastructures for indirect coordination, such as digital pheromones, or support for governed interaction in electronic institutions. Yet, in general, the notion of environment is not well defined. Functionalities of the environment are often dealt with implicitly or in an ad hoc manner. This is not only poor engineering practice, it also hinders engineers to exploit the full potential of the environment in multiagent systems. In this paper, we put forward the environment as an explicit part of multiagent systems.We give a definition stating that the environment in a multiagent system is a first-class abstraction with dual roles: (1) the environment provides the surrounding conditions for agents to exist, which implies that the environment is an essential part of every multiagent system, and (2) the environment provides an exploitable design abstraction for building multiagent system applications. We discuss the responsibilities of such an environment in multiagent systems and we present a reference model for the environment that can serve as a basis for environment engineering. To illustrate the power of the environment as a design abstraction, we show how the environment is successfully exploited in a real world application. Considering the environment as a first-class abstraction in multiagent systems opens up new horizons for research and development in multiagent systems. 相似文献
43.
海洋钻井液有机物添加剂生物降解性评价 总被引:1,自引:0,他引:1
随着海洋石油的勘探开发,钻井液有机添加剂不可避免地进入海洋.因此在海洋勘探开发过程中应选择环保性能好,即生物降解性能好的有机物添加剂。用累计耗氧量法测定了海洋钻井液有机添加剂的生物降解性,研究评价了有机添加剂的生物降解规律和机理,探讨了有机物生物降解性同其化学结构的内在联系,为海洋勘探开发过程中选择环保性能好的有机物添加剂提供理论依据。总结实验结果发现:淀粉类(如DFD-140和FI-E1等)最容易生物降解;其次是纤维素类(如MV-CMC等)和烯类单体聚合物(如PAM和PHP);而沥青类、两性离子类则难以生物降解,有的甚至对生物降解起抑制作用。 相似文献
44.
航空放射性遥感系统采用航空γ能谱仪,在空中飞行探测地表放射性,能够快速进行大面积环境放射性调查。结合已经开始进行的首次大面积航空放射性遥感调查工作,简要介绍了航空放射性遥感系统构成、核探测γ能谱测量和数据处理技术。对系统转换因子刻度和剥离系数刻度方法进行了讨论,并对初步应用情况进行了总结。 相似文献
45.
Color‐vision deficiency is a relatively common genetic condition, which often leads to the obstruction of necessary information in colored images. It is important to minimize such inconvenient effects in communication using colored images from a universal design perspective. The universal design principle stipulates that all environments and products should be usable by all people, regardless of age, physical attributes, and ability. This article proposes a method to detect color combinations in a given image that would confuse color dichromats, and suggests a way in which to modify them to make the image easily distinguishable for both normal and dichromatic observers. Confusing color combinations were detected based on a color‐difference calculation using simulations of how the color would appear to dichromats. The confusing colors were then modified based on the minimization of an evaluation function, which was defined as the sum of the degree of confusion and the degree of color change from the original image. Several colored images obtained by the proposed method were compared with the originals by red–green dichromatic observers who judged them to be clearer, thereby confirming that the proposed method was effective for color rendering for universal design. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 203–211, 2008 相似文献
46.
In this work the synergistic effects of microwave (MW) irradiation induced oxidation processes and CoFe2O4 were studied for the degradation of brilliant green (BG) from aqueous solutions. Under the optimum condition, the ratio of solid to liquid was 1:167 (0.3 g CoFe2O4 mixed with 50 mL of 20 mg L−1 BG solution), MW power 600 W, and the time of the irradiation 2 min. And the decolorization rate could reach up to 100%. Further investigation showed that BG was degraded by MW-induced oxidation combined with CoFe2O4 surface adsorption. The CoFe2O4 could increase the efficiencies of MW degradation and be used repeatedly. The experimental results indicated that the method of MW degradation BG in the presence of CoFe2O4 could reduce reaction time and increase product yield. 相似文献
47.
Christoph Böhringer Wolfgang Wiegard Collin Starkweather Anna Ruocco 《Computational Economics》2003,22(1):75-109
The double or even triple dividend hypothesis of green tax reforms has beena major issue of dispute in both the scientific community and the politicalarena during the last decade. Theoretical analysis has provided a number ofimportant qualitative insights to the debate but lacks of actual policyrelevance due to very restrictive assumptions. Applied research that takes thestep from stylized analytical to complex numerical models usually comes as ablackbox to non-expert modelers. This paper aims at bridging the gap betweenstylized theoretical work and numerical analysis. We develop a flexible,interactive simulation model which is accessible underhttp://brw.zew.de. Users can specify their own green tax reforms andevaluate the induced economic and environmental effects. Based on illustrativesimulations, we demonstrate the usefulness of our do-it-yourself approach fora better understanding of the double (triple) dividend hypothesis. 相似文献
48.
49.
从对区域地质调查的任务出发,总结了过去区域地质调查工作的特点,即基本上是沿用传统方式进行的。提出和论述了21世纪中国区域地质调查应有新发展,以适应战略转变的要求,即除去运输、通讯、记录及数字化成图等之外,更应当面向土地资源、矿产资源、地质灾害以及提高环境质量的需要, 用现代地学理论指导进行多学科的调查和采集、整理资料,实现3维多参数填图和理论概括,是关系现代地质科学发展的、具有深远战略意义的事。几十年的调查工作已证明深部的地质构造情况与地表层的观察结果是不一样的,与依据地表地质构造情况推测的深层情况也很不同。今后应加强深部探测,发展深部探测技术,取得不同深度层次的高分辨率成像图案,使人们对地球的认识提高到一个新的高度,形成新的空间—时间观念,以更有效地解决我国及地球的资源环境问题。 相似文献
50.
On the basis of the idea that situational norms are mentally represented as associations between environments and normative behavior, it was proposed that an environment can automatically direct normative behavior. More specifically, when situational norms are well-established (e.g., when entering the library, one should be silent), an environment is capable of automatically activating mental representations of normative behavior and the behavior itself. In these experiments, participants were exposed to pictures of environments, and effects on accessibility of representations of normative behavior and on actual behavior were assessed. Results indicated that representations of behavior and actual behavior itself are activated automatically when (a) goals to visit the environment are active and (b) strong associations between environment and normative behavior are established. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献