全文获取类型
收费全文 | 127258篇 |
免费 | 7084篇 |
国内免费 | 3545篇 |
专业分类
电工技术 | 6213篇 |
技术理论 | 7篇 |
综合类 | 10995篇 |
化学工业 | 9249篇 |
金属工艺 | 6005篇 |
机械仪表 | 14311篇 |
建筑科学 | 28590篇 |
矿业工程 | 3909篇 |
能源动力 | 2992篇 |
轻工业 | 5097篇 |
水利工程 | 3624篇 |
石油天然气 | 4079篇 |
武器工业 | 1440篇 |
无线电 | 7737篇 |
一般工业技术 | 13334篇 |
冶金工业 | 3070篇 |
原子能技术 | 663篇 |
自动化技术 | 16572篇 |
出版年
2024年 | 454篇 |
2023年 | 1238篇 |
2022年 | 2070篇 |
2021年 | 2641篇 |
2020年 | 2917篇 |
2019年 | 2219篇 |
2018年 | 2181篇 |
2017年 | 2784篇 |
2016年 | 3191篇 |
2015年 | 3462篇 |
2014年 | 9054篇 |
2013年 | 7127篇 |
2012年 | 8927篇 |
2011年 | 9591篇 |
2010年 | 8116篇 |
2009年 | 8411篇 |
2008年 | 7527篇 |
2007年 | 9097篇 |
2006年 | 7640篇 |
2005年 | 6731篇 |
2004年 | 5443篇 |
2003年 | 5133篇 |
2002年 | 4135篇 |
2001年 | 3443篇 |
2000年 | 2836篇 |
1999年 | 2200篇 |
1998年 | 1823篇 |
1997年 | 1536篇 |
1996年 | 1289篇 |
1995年 | 1003篇 |
1994年 | 815篇 |
1993年 | 565篇 |
1992年 | 451篇 |
1991年 | 375篇 |
1990年 | 238篇 |
1989年 | 242篇 |
1988年 | 186篇 |
1987年 | 139篇 |
1986年 | 82篇 |
1985年 | 93篇 |
1984年 | 122篇 |
1983年 | 81篇 |
1982年 | 92篇 |
1981年 | 31篇 |
1980年 | 35篇 |
1979年 | 27篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1959年 | 11篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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
122.
In this study, a single unit of planar micro-solid-oxide fuel cell (μSOFC) is investigated numerically to evaluate the influences of flow channel design, oxygen composition, and thermal operating conditions on cell performance. Four flow channel designs are examined under the co-flow configuration: serpentine, double serpentine, rod bundle, and oblique rib. For all designs, the contacts areas of interconnect to electrodes are kept consistent to maintain the ohmic losses at the same level. To characterize the mass transport effects, there are three different compositions, 100% O2, 50% O2/50% N2 and air, fed to the cathode inlet. Different thermal conditions, adiabatic and isothermal, are applied to the outer boundary of the μSOFC and the results are compared. The outcomes suggest that both thermal conditions and oxidant composition show remarkable influences on μSOFC performance. Under adiabatic conditions, the rise of cell temperature causes a decrease in reversible voltage, deteriorating the overall cell competence. When oxygen is diluted with nitrogen, local gas diffusion becomes dominant to the cathode reaction. Bulk flow, on the other hand, plays a minor role in cell performance since there is little deviation in the polarization curves for all flow channel designs, even at high current densities. For comparison, the flow visualization technique is employed to observe the transport phenomena in various flow channel designs. The flow patterns are found to resemble the concentration distribution, providing a useful tool to design μSOFCs. 相似文献
123.
介绍了设计模式在解决特定问题过程中的基本功能作用,分析了设计模式与程序结构之间的关系,并在此基础上讨论了如何使用设计模式来改善程序结构的问题。 相似文献
124.
游强盛 《有色冶金设计与研究》2004,25(4):40-44
通过南昌市某快速路的设计实例,认识到搞好快速路沿线各交叉口的方案设计是快速路规划设计的关键内容。道路交叉口设计应注重交通功能分析,满足路口交通需求,同时也不能忽视立交的景观要求。 相似文献
125.
以某公司焦化厂焦化DCS控制系统为例,从DCS系统的选型、设计、实施等几方面。阐述焦化DCS控制系统的设计与实现。 相似文献
126.
中国传统的思维方式深深地影响了中国传统陶瓷艺术设计,中国传统陶瓷艺术设计的历史脉络清晰,深入到设计思维系统的深层,才有助于我们对当前的陶瓷设计作出有效的转化。现代陶瓷设计的观念是对传统陶瓷文化的延续和发展,深入挖掘传统思维方式的源头活水,才是发展中国现代陶瓷设计的关键。 相似文献
127.
Being perceptive is a trait highly valued in scientific and engineering professions. What a scientist or engineer notices while considering a problem, evaluating alternatives, or interpreting data has a profound impact on how a problem is viewed and solved. This paper focuses on processes we believe underlie being perceptive: firstly, preparation—becoming attuned to salient or important features; secondly, assimilation-detection and exploration of patterns (invariants) as well as anomalies; and thirdly, strategic control-heuristic strategies for exploring the implications of what has been observed. These processes play an integral role in characteristic activities within creative design, including problem reformulation, the emergence of properties and constraints on the solution, and the ability to incorporate into the design experimental feedback from the environment and from experiences with prototypes and previous designs. The paper presents a computational model incorporating these ideas, implemented in a system called IMPROVISER. 相似文献
128.
本文通过建立几何模型 ,讨论了高速转镜相机光束倾斜入口的成象原理。证实了倾斜光束入口在转镜旋转时成象点的扫描轨迹是在以入射点为顶点 ,以成象点和入射点的连线为母线扫出的正圆锥底面的平面内 ,从而把空间光学的复杂设计问题简化成平面上的设计。此原理已用于 PDF- 2 0 0型平面转镜等待式分幅相机的设计 相似文献
129.
本研究在简介国际上先进的变参设计几种方法及优点后,叙述了一个国家863/CIMS项目:CAD/CAPP/NCP集成系统中二维尺寸驱动的变参设计子系统的构成与功能;然后着重阐述了本系统采用的尺寸驱动的变参设计思想和几何约束建立的原则,并提供了系统数据结构,最后以几个实例证明了此方法的正确性与工程实用性。 相似文献
130.
The focus of this paper is database design using automated database design tools or more general CASE tools. We present a genetic algorithm for the optimization of (internal) database structures, using a multi-criterion objective function. This function expresses conflicting objectives, reflecting the well-known time/space trade-off. This paper shows how the solution space of the algorithm can be set up in the form of tree structures (forests), and how these are encoded by a simple integer assignation. Genetic operators (database transformations) defined in terms of this encoding behave as if they manipulate tree structures. Some basic experimental results produced by a research prototype are presented. 相似文献