全文获取类型
收费全文 | 36078篇 |
免费 | 5072篇 |
国内免费 | 2006篇 |
专业分类
电工技术 | 3142篇 |
技术理论 | 2篇 |
综合类 | 3233篇 |
化学工业 | 3779篇 |
金属工艺 | 1835篇 |
机械仪表 | 3263篇 |
建筑科学 | 3874篇 |
矿业工程 | 2231篇 |
能源动力 | 2565篇 |
轻工业 | 3834篇 |
水利工程 | 1973篇 |
石油天然气 | 2822篇 |
武器工业 | 450篇 |
无线电 | 2269篇 |
一般工业技术 | 2807篇 |
冶金工业 | 2131篇 |
原子能技术 | 503篇 |
自动化技术 | 2443篇 |
出版年
2024年 | 314篇 |
2023年 | 852篇 |
2022年 | 1557篇 |
2021年 | 1790篇 |
2020年 | 1906篇 |
2019年 | 1476篇 |
2018年 | 1247篇 |
2017年 | 1479篇 |
2016年 | 1564篇 |
2015年 | 1601篇 |
2014年 | 2337篇 |
2013年 | 2218篇 |
2012年 | 2556篇 |
2011年 | 2807篇 |
2010年 | 2078篇 |
2009年 | 2061篇 |
2008年 | 1700篇 |
2007年 | 2008篇 |
2006年 | 1780篇 |
2005年 | 1612篇 |
2004年 | 1290篇 |
2003年 | 1149篇 |
2002年 | 953篇 |
2001年 | 769篇 |
2000年 | 706篇 |
1999年 | 618篇 |
1998年 | 484篇 |
1997年 | 372篇 |
1996年 | 335篇 |
1995年 | 307篇 |
1994年 | 236篇 |
1993年 | 198篇 |
1992年 | 141篇 |
1991年 | 127篇 |
1990年 | 104篇 |
1989年 | 92篇 |
1988年 | 69篇 |
1987年 | 40篇 |
1986年 | 27篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1966年 | 7篇 |
1964年 | 14篇 |
1962年 | 6篇 |
1959年 | 10篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
41.
N.M. ShaalanAuthor Vitae T. YamazakiAuthor Vitae T. KikutaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):784-790
Electrodes with micro-gaps are fabricated by using dc-sputtering and FIB techniques. SnO2 nanowires are deposited on the micro-gap (1-30 μm) by suspension dropping method to fabricate a micro-gas sensor. The sensing ability of various SnO2 micro-gap sensors is measured. A comparison between sensors reveals that the short-gap electrode has numerous advantages in terms of reliability, high sensitivity and detection of low concentrations of NO2, while the large-gap electrode is relatively sensitive for high concentrations. Conductance measurements are carried out at different surface temperatures and NO2 concentrations in order to investigate the effects that the gap size has on the overall sensor conductance. The results suggest that the interface between the electrode and sensitive layer has a very important role for the sensing mechanism of tin dioxide gas sensors. 相似文献
42.
Dong-Seok Lee 《Applied ergonomics》2009,40(3):440-447
This study introduces a user interface, referred to as the flow interface, which provides a graphical representation of the movement of content among and inside audio/video devices. The proposed interface provides a different frame of reference with content-oriented visualization of the generation, manipulation, storage, and display of content as well as input and output. The flow interface was applied to a VCR/DVD recorder combo, one of the most complicated consumer products. A between-group experiment was performed to determine whether the flow interface helps users to perform various tasks and to examine the learning effect of the flow interface, particularly in regard to hooking up and recording tasks. The results showed that participants with access to the flow interface performed better in terms of success rate and elapsed time. In addition, the participants indicated that they could easily understand the flow interface. The potential of the flow interface for application to other audio video devices, and design issues requiring further consideration, are discussed. 相似文献
43.
Acceptance, utility, and usability of system designs have become a focal interest in human–computer interaction (HCI) research, yet at present there is a lack detailed understandings of which system design features influence them. The purpose of the study is to examine the effects of five product design features; customization, adaptive behavior, memory load, content density, and speed on user preference through an experimental study by using conjoint analysis. In experimental study, instead of classical conjoint cards, prototypes were generated for products. Besides, desirability and market segments of product prototypes were identified. In line with the results, among the five product design features, speed is the most and customization is the least important features that affect user preference. Contrary to the expectations, customization has a relatively small importance value in this research. Subsequent design features that influence user preference after speed are minimal memory load, adaptive behavior, and content density, respectively. According to findings, interfaces that have high-speed, minimal memory load, adaptive behavior, low content density, and customization features are more preferable than those that do not. 相似文献
44.
A new approach is introduced for turbidite modeling, leveraging the potential of computational fluid dynamics methods to simulate the flow processes that led to turbidite formation. The practical use of numerical flow simulation for the purpose of turbidite modeling so far is hindered by the need to specify parameters and initial flow conditions that are a priori unknown. The present study proposes a method to determine optimal simulation parameters via an automated optimization process. An iterative procedure matches deposit predictions from successive flow simulations against available localized reference data, as in practice may be obtained from well logs, and aims at convergence towards the best-fit scenario. The final result is a prediction of the entire deposit thickness and local grain size distribution. The optimization strategy is based on a derivative-free, surrogate-based technique. Direct numerical simulations are performed to compute the flow dynamics. A proof of concept is successfully conducted for the simple test case of a two-dimensional lock-exchange turbidity current. The optimization approach is demonstrated to accurately retrieve the initial conditions used in a reference calculation. 相似文献
45.
The model-based human body motion analysis system 总被引:3,自引:0,他引:3
In this paper, we propose a model-based method to analyze the human walking motion. This system consists of three phases: the preprocessing phase, the model construction phase, and the motion analysis phase. In the experimental results, we show that our system not only analyzes the motion characteristics of the human body, but also recognizes the motion type of the input image sequences. Finally, the synthesized motion sequences are illustrated for verification. The major contributions of this research are: (1) developing a skeleton-based method to analyze the human motion; (2) using Hidden Markov Model (HMM) and posture patterns to describe the motion type. 相似文献
46.
周利群 《数码设计:surface》2008,(7):109-111
由于受到"艺术至上论"和"技术至上论"两种不良教学思想的影响,使得我国高校服装设计教育出现毕业学生综合素质较差,学生知识结构单一,设计思路狭窄,与社会实际需求脱节现象严重等等弊端,我们要不断深刻反思,加以改进。 相似文献
47.
刘超英 《数码设计:surface》2008,(3):100-102
浙江石窗是第二批浙江省非物质文化遗产名录中的一项民间美术,它是盛开在浙江大地上的一朵建筑民俗之花,它的审美趣味与当地的民风民俗和建筑风格完全融合,它的表现手法与中国的吉祥图案一脉相连。 相似文献
48.
由于产品的注塑成型过程非常复杂,而注塑的计算机模拟能比较准确的预测产品的质量和存在的问题。本文介绍了Moldflow软件MPI/Stress中的MPI/Cool、MPI/Flow、MPI/Warpage模块的作用,并以标准齿轮为例进行了冷却、模流和翘曲分析,分析和讨论了影响产品质量的主要原因和问题。 相似文献
49.
50.
Energy flux characteristics of seismic waves at the interface between soil layers with different saturations 总被引:1,自引:0,他引:1
Based on the multiphase poroelasticity theory describing the propagation of waves in the unsaturated fluid-saturated porous medium, the reflection and transmission coefficients of the seismic waves at the interface between soil layers with different saturations are obtained. Our unsaturated model consists of a deformable skeleton in which two compressible and viscous fluids (i.e., water and gas) flow in the interstices. Three compressional waves (i.e., P1, P2, and P3 waves) and one shear (i.e., S wave) wave exist in the unsaturated soils. The expressions for the energy ratios of the various reflected and transmitted waves at the interface during the transmission and reflection processes are presented in explicit forms accordingly. At last, numerical computations are performed and the results obtained are respectively depicted graphically. The variation of the energy ratios with the incident angle, wave frequency and saturation degrees of the upper and lower soil layers is illustrated in detail. The calculation results show that the allocation of incident seismic waves at the interface is influenced not only by the angle and frequency of the incident seismic waves, but also by the saturations of the upper and lower soil layers. It is also verified that, at the interface, the sum of energy ratios of the reflected and transmitted waves is approximately equal to unity as was expected. This study is of importance to several fields such as geotechnical engineering, seismology, and geophysics. 相似文献