全文获取类型
收费全文 | 2187篇 |
免费 | 92篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 120篇 |
综合类 | 10篇 |
化学工业 | 653篇 |
金属工艺 | 50篇 |
机械仪表 | 66篇 |
建筑科学 | 93篇 |
矿业工程 | 9篇 |
能源动力 | 85篇 |
轻工业 | 236篇 |
水利工程 | 9篇 |
石油天然气 | 18篇 |
无线电 | 122篇 |
一般工业技术 | 421篇 |
冶金工业 | 172篇 |
原子能技术 | 82篇 |
自动化技术 | 151篇 |
出版年
2024年 | 9篇 |
2023年 | 32篇 |
2022年 | 61篇 |
2021年 | 80篇 |
2020年 | 41篇 |
2019年 | 34篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 57篇 |
2015年 | 39篇 |
2014年 | 49篇 |
2013年 | 140篇 |
2012年 | 108篇 |
2011年 | 134篇 |
2010年 | 95篇 |
2009年 | 94篇 |
2008年 | 101篇 |
2007年 | 97篇 |
2006年 | 80篇 |
2005年 | 79篇 |
2004年 | 60篇 |
2003年 | 72篇 |
2002年 | 70篇 |
2001年 | 46篇 |
2000年 | 44篇 |
1999年 | 45篇 |
1998年 | 82篇 |
1997年 | 61篇 |
1996年 | 50篇 |
1995年 | 39篇 |
1994年 | 37篇 |
1993年 | 40篇 |
1992年 | 22篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 5篇 |
排序方式: 共有2297条查询结果,搜索用时 15 毫秒
21.
Yuji Watanabe 《Artificial Life and Robotics》2011,16(3):422-425
Statistical en-route filtering (SEF) schemes can detect and eliminate false data injection attacks in wireless sensor networks.
However, SEF does not address the identification of the compromised nodes which are injecting false reports. Therefore, we
have proposed an immunity-based SEF to identify compromised nodes and achieve earlier detection of false reports. In the proposed
scheme, each node has a list of neighborhood nodes and assigns credibility to each neighboring node. Each node can update
the credibility of a neighboring node based on the success or failure of filtering and communication, and can then use the
updated credibility as the probability of the next communication. In this article, some simulation results show that the immunity-based
SEF outperforms the original SEF. 相似文献
22.
In recently developed intelligent vehicles, warning alarms are often used to prompt avoidance behaviours from drivers facing imminent hazardous situations. However, when critical reaction delays to auditory stimulation are anticipated, the alarm should be activated earlier to compensate for such delays. It was found that reaction times to an auditory stimulus significantly increased in the presence of slow eye movement (SEM), which is known to occur frequently during the wake-sleep transition. The reaction delay could not be attributed to temporal effects such as fatigue and was invariant regardless of response effectors (finger or foot). Moreover, it was found that applied pedal force decreased immediately after an auditory stimulus interrupted SEM. Consequently, it was concluded that SEM can be a good predictor of reaction delays to auditory warning alarms when drivers are in a drowsy state. STATEMENT OF RELEVANCE: The present study demonstrated that simple auditory reaction time significantly increased when SEM emerged. In the design of vehicle safety systems using warning alarms to prompt avoidance behaviours from drivers, such reaction delays during SEM must be taken into account. 相似文献
23.
Urban growth modeling of Kathmandu metropolitan region, Nepal 总被引:6,自引:0,他引:6
The complexity of urban system requires integrated tools and techniques to understand the spatial process of urban development and project the future scenarios. This research aims to simulate urban growth patterns in Kathmandu metropolitan region in Nepal. The region, surrounded by complex mountainous terrain, has very limited land resources for new developments. As similar to many cities of the developing world, it has been facing rapid population growth and daunting environmental problems. Three time series land use maps in a fine-scale (30 m resolution), derived from satellite remote sensing, for the last three decades of the 20th century were used to clarify the spatial process of urbanization. Based on the historical experiences of the land use transitions, we adopted weight of evidence method integrated in cellular automata framework for predicting the future spatial patterns of urban growth. We extrapolated urban development patterns to 2010 and 2020 under the current scenario across the metropolitan region. Depending on local characteristics and land cover transition rates, this model produced noticeable spatial pattern of changes in the region. Based on the extrapolated spatial patterns, the urban development in the Kathmandu valley will continue through both in-filling in existing urban areas and outward rapid expansion toward the east and south directions. Overall development will be greatly affected by the existing urban space, transportation network, and topographic complexity. 相似文献
24.
Kazuko Yamasaki Kenneth J. Mackin Masanori Ohshiro Kotaro Matsushita Eiji Nunohiro 《Artificial Life and Robotics》2008,12(1-2):122-124
We studied the networks of the temperature record in the atmosphere. They are made by the strength of the synchronization,
including the delay between temperatures at locations on Earth. We consider these locations as nodes, and we consider a pair
of locations as a link if the synchronization between them is stronger than a threshold. The network is scale-free, which
is thought to contribute to the stability of the climate.
This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January
25–27, 2007 相似文献
25.
26.
H. Takahashi L. H. Liu Y. Yashiro K. Ioku G. Bignall N. Yamasaki T. Kori 《Journal of Materials Science》2006,41(5):1585-1589
The reduction of CO2 under hydrothermal conditions has been investigated. In typical experiment, Fe-powder, Ni-powder, solvent, and CO2 have been reacted in a batch-type micro autoclave under hydrothermal conditions for several hours. Methane, formic acid,
and hydrogen were generated after treatment in water. With the rise of Ni amount, the methane yield increased while hydrogen
and formic acid decreased. It is supposed that Ni has acted as a hydrogenation catalyst. In basic solution, CO2 was converted to formic acid selectively at 300°C involved with trace of methane. Considering the reduction characteristics
of formic acid, the reaction pathway has been discussed. In experiments with the mixture of Fe and Fe3O4, trace of methanol was detected at the experiments with less amount of metallic Fe. It is inferred that the control on the
effect of reductant is indispensable for oxygenated organic compound formation. Experiment on the effect of water has been
conducted using hydrogen. Ethane yield increased with the amount of water, while there was no drastic change in the yield
of methane. From these results, it is supposed that the steam reforming reaction of methane was involved in the reduction
of CO2, and effected on the C–C bond formation. 相似文献
27.
Agglomeration control of hydroxyapatite nano-crystals grown in phase-separated microenvironments 总被引:1,自引:0,他引:1
Kimiyasu Sato Yuji Hotta Takaaki Nagaoka Masaki Yasuoka Koji Watari 《Journal of Materials Science》2006,41(17):5424-5428
Materials synthesis processes that require high temperatures consume large quantities of energy that generate an environmental burden. We attempted to synthesize hydroxyapatite (HAp) nano-crystals without firing or melting. “Water in oil” (W/O) emulsions were employed as microreactors for HAp formation. The surfactant-bounded water mediated HAp crystal nucleation, and HAp nano-crystallites were obtained. The obtained particles were aggregates composed of plate-like nano-crystals and monodisperse tiny crystals. Utilization of the W/O emulsions resulted in tunable nucleation frequency and the reactant provision, and yielded HAp nano-crystals with characteristic agglomeration properties. 相似文献
28.
Z. Jing N. Matsuoka F. Jin N. Yamasaki K. Suzuki T. Hashida 《Journal of Materials Science》2006,41(5):1579-1584
Solidification of Coal Fly-ash (CFA) has been carried out using a hydrothermal processing method. In the hydrothermal processing,
the CFA was first compacted in a mold at 20 - 50 MPa, and then hydrothermally cured in an autoclave. The hydrothermal curing
was performed at 150 – 250°C for 15 – 60 h. The experimental results showed that NaOH solution, Ca(OH)2 content, compaction pressure, autoclave curing temperature and time significantly affected the strength of solidified bodies.
The most important strength-producing constituent in the solidified bodies produced with CFA was tobermorite, or tobermorite-like
calcium silicate hydrate. When the CaO/SiO2 ratio of the starting material was close to 0.83, tobermorite readily formed and the formed tobermorite enhanced the strength
of solidified bodies. The tensile strength determined by the Brazilian test reached more than 10 MPa under the hydrothermal
processing. As such, the hydrothermal processing method may provide a high potential for recycling CFA on a large scale. 相似文献
29.
Ichiro Takano Yoshiharu Arai Michiko Sasaki Yoshio Sawada Kaori Yamada Takayoshi Yagasaki Yuji Kimura 《Vacuum》2006,80(7):788-792
Biodegradable plastics can be used as conventional plastics, while on disposal they decompose to water and carbon dioxide by microorganisms existing in natural environment. Products using biodegradable plastics have recently been developed in many companies pursuing ecology. In this study, surface modification of biodegradable plastics was carried out by inert ion beams for improvement of photo deterioration under an ultraviolet ray. The hardness of biodegradable plastics tended generally to decrease with irradiation of an ultraviolet ray. In this method, the hardness of ion-bombarded biodegradable plastics was kept at an initial value under an ultraviolet ray, because the modified layer by ion bombardment intercepted an ultraviolet ray. The hardness of He+ ion-bombarded biodegradable plastics showed larger value than that of Ar+ ion bombardment. He+ ion bombardment at ion energy of 10 keV produced the suitable property with both of high transmittance of a visible ray and high interception of an ultraviolet ray in a surface layer of biodegradable plastics. 相似文献
30.
Makoto Kobayashi Masashi Shimada Yuji Hatano Takuji Oda Brad Merrill Yasuhisa Oya Kenji Okuno 《Fusion Engineering and Design》2013,88(9-10):1749-1752
The deuterium trapping behaviors in tungsten damaged by light ions with lower energy (10 keV C+ and 3 keV He+) or a heavy ion with higher energy (2.8 MeV Fe2+) were compared by means of TDS to understand the effects of cascade collisions on deuterium retention in tungsten. By light ion irradiation, most of deuterium was trapped by vacancies, whose retention was almost saturated at the damage level of 0.2 dpa. For the heavy ion irradiation, the deuterium trapping by voids was found, indicating that cascade collisions by the heavy ion irradiation would create the voids in tungsten. Most of deuterium trapped by the voids was desorbed in higher temperature region compared to that trapped by vacancies. It was also found that deuterium could accumulate in the voids, resulting in the formation of blisters in tungsten. 相似文献