全文获取类型
收费全文 | 3055篇 |
免费 | 245篇 |
国内免费 | 112篇 |
专业分类
电工技术 | 167篇 |
综合类 | 159篇 |
化学工业 | 523篇 |
金属工艺 | 168篇 |
机械仪表 | 155篇 |
建筑科学 | 222篇 |
矿业工程 | 66篇 |
能源动力 | 95篇 |
轻工业 | 166篇 |
水利工程 | 69篇 |
石油天然气 | 215篇 |
武器工业 | 38篇 |
无线电 | 349篇 |
一般工业技术 | 406篇 |
冶金工业 | 176篇 |
原子能技术 | 66篇 |
自动化技术 | 372篇 |
出版年
2024年 | 15篇 |
2023年 | 46篇 |
2022年 | 86篇 |
2021年 | 162篇 |
2020年 | 117篇 |
2019年 | 93篇 |
2018年 | 111篇 |
2017年 | 100篇 |
2016年 | 119篇 |
2015年 | 148篇 |
2014年 | 141篇 |
2013年 | 187篇 |
2012年 | 204篇 |
2011年 | 192篇 |
2010年 | 181篇 |
2009年 | 164篇 |
2008年 | 138篇 |
2007年 | 126篇 |
2006年 | 117篇 |
2005年 | 108篇 |
2004年 | 83篇 |
2003年 | 72篇 |
2002年 | 56篇 |
2001年 | 58篇 |
2000年 | 53篇 |
1999年 | 68篇 |
1998年 | 61篇 |
1997年 | 61篇 |
1996年 | 59篇 |
1995年 | 54篇 |
1994年 | 46篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3412条查询结果,搜索用时 0 毫秒
51.
Yi Wei Wei Wang Zhennan Wang Hang Yang Xinyu You Yunna Zhao Peipei Dang Hongzhou Lian Jianhua Hao Guogang Li Jun Lin 《Advanced functional materials》2023,33(2):2205829
Bismuth (Bi3+)-included lead-free metal halide (LFMH) materials attract much attention in lighting, display, photodetectors, X-ray detectors, and photovoltaic fields, due to the tunable luminescence and optoelectronic performance in response to crystal and electronic structure, morphology, and particle sizes. This review summarizes Bi3+-included LFMH materials about their preparation approach, crystal and electronic structure properties, luminescence performance, and emerging applications. Notably, Bi3+ ions not only can act as framework cation to construct stable LFMH structure, but can also incorporate into LFMH materials as activators or sensitizers to generate remarkable luminescence tuning and band engineering. The Bi3+ effect on the luminescence and optoelectronic properties of LFMH materials, including, promotion of exciton localization, enhancement of light absorption in near-ultraviolet region, action as sensitizer ions to transfer energy to rare earth or transition metal ions and emission of highly-efficient light is systematically summarized. The proposed structure-luminescence relationship offers guidance for the optimization of current Bi3+-included LFMH materials and the exploitation of new LFMH derivatives. 相似文献
52.
Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultrahigh carrier mo-bility and thermal conductivity,low thermal expansion coefficient,and ultra-high breakdown voltage,etc.Despite these ex-traordinary properties,diamond also faces various challenges before being practically used in the semiconductor industry.This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes,high-power/high-frequency field-effect transistors,MEMS/NEMS,and devices operating at high temperatures.Following that,we will discuss recent developments to address scalable diamond device applications,emphasizing the synthesis of large-area,high-quality CVD diamond films and difficulties in diamond doping.Lastly,we show potential solutions to modulate diamond’s electronic properties by the“elastic strain engineering”strategy,which sheds light on the future development of diamond-based electronics,photonics and quantum systems. 相似文献
53.
Synthesis of Highly Active Sub‐Nanometer Pt@Rh Core–Shell Nanocatalyst via a Photochemical Route: Porous Titania Nanoplates as a Superior Photoactive Support
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
54.
55.
通过分析.net中的CallBack回调技术和已有的基于ArcGIS Server构建的WebGIS系统的三层体系结构,结合数字化城管部件在线更新的系统的开发实例,搭建了一套多层体系结构和.net的CallBack回调技术相结合的体系框架,事实证明此框架有效的降低了服务器的负载,实现了页面异步调用和无刷新的局部显示,提升了用户体验。 相似文献
56.
针对现有分布式地理信息系统数据处理的瓶颈问题,利用Web服务和移动Agent技术解决GIS领域的动态服务问题,详细阐述GIS软件的系统结构和动态服务模型,介绍移动Agent和构件服务等相关实现技术,给出基于智能决策的Agent迁移策略及其算法描述.最后通过模拟仿真实验,验证了该迁移策略和算法的有效性. 相似文献
57.
The conventional precision-based decision analysis methodology is invalid for business decision analysis when precise assessment data seldom exist. This paper considers the Cournot game with fuzzy demand and fuzzy costs that are assumed to be triangular fuzzy numbers. Our model utilizes the weighted center of gravity (WCoG) method to defuzzify the fuzzy profit function into a crisp value. We derive the equilibrium Cournot quantity of each firm by simultaneously solving the first-order condition of each firm. Our model explicitly derives the necessary condition to avoid an unreasonable outcome of negative equilibrium quantities and lack of flexibility for modification of the ranking method. In addition, we examine the standard deviation of the fuzzy profit resulting from the fuzziness of each firm’s cost and market demand functions. We conduct sensitivity analysis to investigate the effect of parameter perturbations on firms’ outcomes. The results indicate that the center of parameter plays an important role in sensitivity analysis and dominates over variations in equilibrium quantity due to a perturbation of fuzzy parameters. 相似文献
58.
Dang TN Wilkinson L Anand A 《IEEE transactions on visualization and computer graphics》2010,16(6):1044-1052
An ongoing challenge for information visualization is how to deal with over-plotting forced by ties or the relatively limited visual field of display devices. A popular solution is to represent local data density with area (bubble plots, treemaps), color (heatmaps), or aggregation (histograms, kernel densities, pixel displays). All of these methods have at least one of three deficiencies:1) magnitude judgments are biased because area and color have convex downward perceptual functions, 2) area, hue, and brightness have relatively restricted ranges of perceptual intensity compared to length representations, and/or 3) it is difficult to brush or link to individual cases when viewing aggregations. In this paper, we introduce a new technique for visualizing and interacting with datasets that preserves density information by stacking overlapping cases. The overlapping data can be points or lines or other geometric elements, depending on the type of plot. We show real-dataset applications of this stacking paradigm and compare them to other techniques that deal with over-plotting in high-dimensional displays. 相似文献
59.
为解决不规则形状物体面积的快速测量问题,设计实现了一套基于数字图像处理技术的面积测量系统;利用常用硬件构建了合理的系统硬件结构,并开发了适合非计算机专业人士操作的视窗工作软件,将硬件采集到的待测物某表面图像数据经过软件处理之后就可以得到并显示出待测物该表面的面积;实验证明,该系统测量物体面积的精度为士1.5%以内,可以实现对不规则形体面积的有效测量,操作简单、数据可视性好且测量稳定可靠. 相似文献
60.
In this paper, we describe a formal framework for conformance testing of continuous and hybrid systems, using the international
standard ‘Formal Methods in Conformance Testing’ FMCT. We propose a novel test coverage measure for these systems, which is
defined using the star discrepancy notion. This coverage measure is used to quantify the validation ‘completeness’. It is
also used to guide input stimulus generation by identifying the portions of the system behaviors that are not adequately examined.
We then propose a test generation method, which is based on a robotic motion planning algorithm and is guided by the coverage
measure. This method was implemented in a prototype tool that can handle high dimensional systems (up to 100 dimensions). 相似文献