全文获取类型
收费全文 | 13087篇 |
免费 | 805篇 |
国内免费 | 105篇 |
专业分类
电工技术 | 317篇 |
综合类 | 184篇 |
化学工业 | 2696篇 |
金属工艺 | 462篇 |
机械仪表 | 749篇 |
建筑科学 | 446篇 |
矿业工程 | 65篇 |
能源动力 | 535篇 |
轻工业 | 919篇 |
水利工程 | 68篇 |
石油天然气 | 244篇 |
武器工业 | 36篇 |
无线电 | 2233篇 |
一般工业技术 | 2555篇 |
冶金工业 | 953篇 |
原子能技术 | 204篇 |
自动化技术 | 1331篇 |
出版年
2024年 | 20篇 |
2023年 | 174篇 |
2022年 | 237篇 |
2021年 | 390篇 |
2020年 | 306篇 |
2019年 | 244篇 |
2018年 | 351篇 |
2017年 | 397篇 |
2016年 | 410篇 |
2015年 | 339篇 |
2014年 | 511篇 |
2013年 | 816篇 |
2012年 | 767篇 |
2011年 | 929篇 |
2010年 | 700篇 |
2009年 | 723篇 |
2008年 | 699篇 |
2007年 | 603篇 |
2006年 | 549篇 |
2005年 | 505篇 |
2004年 | 427篇 |
2003年 | 361篇 |
2002年 | 373篇 |
2001年 | 325篇 |
2000年 | 326篇 |
1999年 | 338篇 |
1998年 | 438篇 |
1997年 | 296篇 |
1996年 | 248篇 |
1995年 | 169篇 |
1994年 | 186篇 |
1993年 | 158篇 |
1992年 | 99篇 |
1991年 | 96篇 |
1990年 | 74篇 |
1989年 | 67篇 |
1988年 | 50篇 |
1987年 | 53篇 |
1986年 | 33篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1975年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors 下载免费PDF全文
Woo Seok Lee Seung‐Wook Lee Hyungmok Joh Mingi Seong Haneun Kim Min Su Kang Ki‐Hyun Cho Yun‐Mo Sung Soong Ju Oh 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(47)
All‐solution processed, high‐performance wearable strain sensors are demonstrated using heterostructure nanocrystal (NC) solids. By incorporating insulating artificial atoms of CdSe quantum dot NCs into metallic artificial atoms of Au NC thin film matrix, metal–insulator heterostructures are designed. This hybrid structure results in a shift close to the percolation threshold, modifying the charge transport mechanism and enhancing sensitivity in accordance with the site percolation theory. The number of electrical pathways is also manipulated by creating nanocracks to further increase its sensitivity, inspired from the bond percolation theory. The combination of the two strategies achieves gauge factor up to 5045, the highest sensitivity recorded among NC‐based strain gauges. These strain sensors show high reliability, durability, frequency stability, and negligible hysteresis. The fundamental charge transport behavior of these NC solids is investigated and the combined site and bond percolation theory is developed to illuminate the origin of their enhanced sensitivity. Finally, all NC‐based and solution‐processed strain gauge sensor arrays are fabricated, which effectively measure the motion of each finger joint, the pulse of heart rate, and the movement of vocal cords of human. This work provides a pathway for designing low‐cost and high‐performance electronic skin or wearable devices. 相似文献
33.
34.
35.
BK Park ES Cho JD Lee C Oh MS Lee SZ Kim SH Kim KW Cho 《Canadian Metallurgical Quarterly》1998,43(8):611-618
The effect of a naturally occurring plant phenolic constituent (the acylphloroglucinol derivative, jensenone, derived from Eucalyptus jensenii) on the food intake of two folivorous marsupials, the common ringtail (Pseudocheirus peregrinus) and the common brushtail possum (Trichosurus vulpecula) was studied. When fed diets containing varying concentrations of jensenone, both species regulated their intake of jensenone so as not to exceed a ceiling intake. This ceiling was about twice as high for common ringtails as for common brushtails from northern Australia. Southern populations of common ringtails showed greatly reduced capacities to tolerate jensenone. When common brushtails were injected (0.5 mg.kg-0.75 body mass) with ondansetron (a selective antagonist of serotonin 5HT3 receptors), they ate significantly more jensenone than animals injected with physiological saline. The same pattern was observed when common ringtails were fed diets containing both jensenone and ondansetron (0.0035 mg.g-1 wet mass of diet). Ondansetron injection had no effect on food intake when the food did not contain jensenone while the addition of higher doses of ondansetron to diets of common ringtails very slightly reduced food intakes of a non-jensenone diet. When common brushtails were given 50 mg of jensenone by gastric lavage, their average subsequent intake of dietary jensenone matched the difference between the daily threshold and the dose given, although the response of individuals was highly variable. Lavage with water alone had no effect on subsequent jensenone intake compared with the pre-dose period. We interpret these results as evidence that the antifeedant effects of jensenone and related compounds are partly mediated by serotonin action on 5HT3 receptors most likely via "nausea" to condition a food aversion. 相似文献
36.
The index inhomogeneity and the microstructure of ZrO(2) films prepared by Ar-ion-assisted deposition are investigated. The results show that as the Ar-ion momentum transferred to the growing film increases, the average refractive index increases, the vacuum-to-air spectral shift becomes almost zero, the sign of relative inhomogeneity transits from negative to positive, and the void fraction of the top layer next to air becomes smaller than that of the bottom one. These optical properties result from the improved packing density and denser outer region next to air. The Ar-ion bombardment also induces the changes in microstructure of ZrO(2) films, such as the preferential (111) orientation of cubic phase, increase in compressive stress, and reduction of surface roughness. 相似文献
37.
Kung Chen Shu-Chun Weng Jia-Yin Lin Meng Wang Siau-Cheng Khoo 《Higher-Order and Symbolic Computation》2011,24(1-2):151-189
Many side-effecting programming activities, such as profiling and tracing, can be formulated as crosscutting concerns and be framed as side-effecting aspects in the aspect-oriented programming paradigm. The benefit gained from this separation of concerns is particularly evident in purely functional programming, as adding such aspects using techniques such as monadification will generally lead to crosscutting changes. This paper presents an approach to provide side-effecting aspects for lazy purely functional languages in a user transparent fashion. We propose a simple yet direct state manipulation construct for developing side-effecting aspects and devise a systematic monadification scheme to translate the woven code to monadic style purely functional code. Furthermore, we present a static and dynamic semantics of the aspect programs and reason about the correctness of our monadification scheme with respect to them. 相似文献
38.
Road sign recognition system remains a challenging part of designing an Intelligent Driving Support System. While there exist
many approaches to classify road signs, none have adopted an unsupervised approach. This paper proposes a way of Self-Organizing
feature mapping for recognizing a road sign. The emergent self-organizing map (ESOM) is employed for the feature mapping in
this study. It has the capability of visualizing the distance structures as well as the density structure of high-dimensional
data sets, in which the ESOM is suitable to detect non-trivial cluster structures. This paper discusses the usage of ESOM
for road sign detection and classification. The benchmarking against some other commonly used classifiers was performed. The
results demonstrate that the ESOM approach outperforms the others in conducting the same simulations of the road sign recognition.
We further demonstrate that the result obtained with ESOM is significantly more superior than traditional SOM which does not
take into the boundary effect like ESOM did. 相似文献
39.
Sangmun Shin Nguyen Khoa Viet Truong Byung Rae Cho Sung Hoon Hong 《Computers & Industrial Engineering》2011
Robust design (RD) and tolerance design (TD) have received much attention from researchers and practitioners for more than two decades, and a number of methodologies for modeling and optimizing the RD and TD processes have been studied. However, there is ample room for improvement. Because most existing research considers RD and TD as separate research fields, the primary objective of this paper is to develop a sequential robust–tolerance design method to jointly determine the best factor settings and the closed-form solutions for the optimal specification limits. We then apply the proposed method to a destructive quality characteristic. Finally, a case study and sensitivity analyses are performed for verification purposes, and further studies are discussed. 相似文献
40.
Investigating factors that influence social presence and learning outcomes in distance higher education 总被引:1,自引:0,他引:1
There are many factors that influence distance learning especially in higher education where collaborative and communicative discourse is necessary for pursuing knowledge. Social presence, among other factors, is an important concept to be facilitated, developed and sustained in distance higher education as it promotes and supports discourse based learning. This study examines the relationship among demographic and other variables, social presence and learning satisfaction. Results showed demographic variables, such as gender, online learning experience and work status were not significant factors in terms of influencing on either social presence or learning satisfaction. While media integration and instructor’s quality teaching were significant predictors of both social presence and learning satisfaction, interactivity among participants was a predictor of social presence but not of learning satisfaction. Along with the study findings, some implications were discussed for online learning practitioners in higher education setting. 相似文献