全文获取类型
收费全文 | 48576篇 |
免费 | 7017篇 |
国内免费 | 3739篇 |
专业分类
电工技术 | 3451篇 |
技术理论 | 2篇 |
综合类 | 5094篇 |
化学工业 | 3536篇 |
金属工艺 | 5205篇 |
机械仪表 | 4067篇 |
建筑科学 | 8060篇 |
矿业工程 | 3739篇 |
能源动力 | 2343篇 |
轻工业 | 3624篇 |
水利工程 | 3518篇 |
石油天然气 | 2996篇 |
武器工业 | 608篇 |
无线电 | 2428篇 |
一般工业技术 | 4981篇 |
冶金工业 | 2995篇 |
原子能技术 | 399篇 |
自动化技术 | 2286篇 |
出版年
2024年 | 347篇 |
2023年 | 1004篇 |
2022年 | 1932篇 |
2021年 | 2295篇 |
2020年 | 2372篇 |
2019年 | 1832篇 |
2018年 | 1637篇 |
2017年 | 1991篇 |
2016年 | 2158篇 |
2015年 | 2228篇 |
2014年 | 3205篇 |
2013年 | 2985篇 |
2012年 | 3741篇 |
2011年 | 3972篇 |
2010年 | 2914篇 |
2009年 | 2883篇 |
2008年 | 2413篇 |
2007年 | 2943篇 |
2006年 | 2646篇 |
2005年 | 2193篇 |
2004年 | 1821篇 |
2003年 | 1634篇 |
2002年 | 1342篇 |
2001年 | 1125篇 |
2000年 | 1082篇 |
1999年 | 908篇 |
1998年 | 659篇 |
1997年 | 539篇 |
1996年 | 436篇 |
1995年 | 411篇 |
1994年 | 349篇 |
1993年 | 252篇 |
1992年 | 205篇 |
1991年 | 163篇 |
1990年 | 168篇 |
1989年 | 129篇 |
1988年 | 87篇 |
1987年 | 55篇 |
1986年 | 38篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 8篇 |
1980年 | 20篇 |
1979年 | 12篇 |
1966年 | 7篇 |
1964年 | 14篇 |
1959年 | 15篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The objective of the current research is to model trends in video game playing, overall computer use, and communication technology use in a longitudinal sample of youths, aged 11-16 over a 3-year interval. In addition, individual difference characteristics that may be predictive of these trends were included, namely, socio-demographic characteristics (gender, ethnicity, and parental income) and personality characteristics (self-esteem, the Big Five personality factors). Findings suggested that youth increased their overall computer and communication technology use but decreased their videogame playing over time. Many individual differences predicted mean levels of these technologies with fewer predicting slopes. Conclusions, implications, and limitations are discussed. 相似文献
993.
994.
Yu-Jin ChenAuthor Vitae Gang XiaoAuthor VitaeTie-Shi WangAuthor Vitae Fan ZhangAuthor VitaeYang MaAuthor Vitae Peng GaoAuthor Vitae Chun-Ling ZhuAuthor VitaeEndi ZhangAuthor Vitae Zhi XuAuthor VitaeQiu-hong LiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):270-277
Crystalline α-MoO3/TiO2 core/shell nanorods are fabricated by a hydrothermal method and subsequent annealing processes under H2/Ar flow and in the ambient atmosphere. The shell layer is composed of crystalline TiO2 particles with a diameter of 2-6 nm, and its thickness can be easily controlled in the range of 15-45 nm. The core/shell nanorods show enhanced sensing properties to ethanol vapor compared to bare α-MoO3 nanorods. The sensing mechanism is different from that of other one-dimensional metal oxide core/shell nanostructures due to very weak response of TiO2 nanoparticles to ethanol. The enhanced sensing properties can be explained by the change of type II heterojunction barrier formed at the interface between α-MoO3 and TiO2 in the different gas atmosphere. The present results demonstrate a novel sensing mechanism available for gas sensors with high performance. 相似文献
995.
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
996.
Xavier Maurice Anders Sandholm Nicolas Pronost Ronan Boulic Daniel Thalmann 《The Visual computer》2009,25(9):835-842
Today, to create and to simulate a virtual anatomical version of a subject is useful in the decision process of surgical treatments.
The muscular activity is one of the factors which can contribute to abnormal movements such as in spasticity or static contracture.
In this paper, we propose a numerical solution, based on the Finite Element (FE) method, able to estimate muscles deformations
during contraction. Organized around a finite element solver and a volumetric environment, this solution is made of all the
modeling and simulation processes from the discretization of the studied domain to the visualization of the results. The choices
of materials and properties of the FE model are also presented such as the hyperelasticity, the contention model based on
inter-meshes neighboring nodes pairing, and the estimation of nodal forces based on the subject-specific muscular forces and
action lines.
相似文献
Nicolas PronostEmail: |
997.
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
998.
The purposes of this study are to: (1) obtain measures of actual decision support system (DSS) use that include the three elements of DSS use proposed by Burton-Jones and Straub (Burton-Jones, A., & Straub, D.W., Jr., (2006). Reconceptualizing system usage: An approach and empirical test. Information Systems Research, 17(3), 228–246), and (2) identify an important psychological construct – a user’s motivation to perform a task – and examine how it interacts with two DSS characteristics – effectiveness and efficiency – to affect actual DSS use. As predicted, the findings indicated that individuals who used a more effective DSS to work on a task that they were motivated in increased usage of the DSS, while DSS use did not differ between individuals who used either a more or less effective DSS to complete a task that they were less motivated in. The results also showed significant difference for two measures of DSS use (i.e., STEP and TIME) and no significant difference for one measure of DSS use (i.e., USE) between individuals who used either a more or less efficient DSS to perform a task that they were more motivated in. As expected, significant differences were found for individuals who used either a more or less efficient DSS to complete a task that they were less motivated in. Finally, the results showed that DSS use increased when perceived ease of use and perceived usefulness of the DSS were high; therefore, these results corroborate the findings of prior research in the context of actual DSS use. 相似文献
999.
基于氧传感膜荧光特性研制了一种低成本、小型化的溶解氧传感器.对传统氧传感膜的制备方案进行了优化,结合其透光特性对所制备的传感膜优劣进行甄别和选优.在此基础上,重点研究了水温、浸泡时间等因素对传感膜荧光发射强度的影响.为提高溶解氧的测量精度,设计了一种45°角斜面传感器探头结构,有效降低了水中气泡对溶解氧的测量干扰.实验结果表明:该溶解氧传感器能够准确测量0 ~20 mg/L范围内的待测液体的含氧量,检测误差为±2%,检测精度达±0.1 mg/L,在工农业生产、水质监测及水产养殖等方面具有较好的应用前景. 相似文献
1000.