全文获取类型
收费全文 | 2942篇 |
免费 | 189篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 56篇 |
综合类 | 32篇 |
化学工业 | 742篇 |
金属工艺 | 82篇 |
机械仪表 | 179篇 |
建筑科学 | 93篇 |
矿业工程 | 5篇 |
能源动力 | 111篇 |
轻工业 | 291篇 |
水利工程 | 15篇 |
石油天然气 | 14篇 |
无线电 | 415篇 |
一般工业技术 | 553篇 |
冶金工业 | 222篇 |
原子能技术 | 52篇 |
自动化技术 | 296篇 |
出版年
2024年 | 5篇 |
2023年 | 40篇 |
2022年 | 91篇 |
2021年 | 117篇 |
2020年 | 75篇 |
2019年 | 79篇 |
2018年 | 96篇 |
2017年 | 110篇 |
2016年 | 102篇 |
2015年 | 99篇 |
2014年 | 126篇 |
2013年 | 168篇 |
2012年 | 180篇 |
2011年 | 223篇 |
2010年 | 180篇 |
2009年 | 163篇 |
2008年 | 163篇 |
2007年 | 102篇 |
2006年 | 102篇 |
2005年 | 80篇 |
2004年 | 81篇 |
2003年 | 73篇 |
2002年 | 76篇 |
2001年 | 71篇 |
2000年 | 51篇 |
1999年 | 57篇 |
1998年 | 100篇 |
1997年 | 69篇 |
1996年 | 52篇 |
1995年 | 38篇 |
1994年 | 36篇 |
1993年 | 17篇 |
1992年 | 31篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1914年 | 2篇 |
排序方式: 共有3158条查询结果,搜索用时 0 毫秒
61.
Template‐Directed Directionally Solidified 3D Mesostructured AgCl–KCl Eutectic Photonic Crystals 下载免费PDF全文
62.
Photonic Crystals: Template‐Directed Directionally Solidified 3D Mesostructured AgCl–KCl Eutectic Photonic Crystals (Adv. Mater. 31/2015) 下载免费PDF全文
63.
Yu Ra Jeong Heun Park Sang Woo Jin Soo Yeong Hong Sang‐Soo Lee Jeong Sook Ha 《Advanced functional materials》2015,25(27):4228-4236
Stretchable electronics have recently been extensively investigated for the development of highly advanced human‐interactive devices. Here, a highly stretchable and sensitive strain sensor is fabricated based on the composite of fragmentized graphene foam (FGF) and polydimethylsiloxane (PDMS). A graphene foam (GF) is disintegrated into 200–300 μm sized fragments while maintaining its 3D structure by using a vortex mixer, forming a percolation network of the FGFs. The strain sensor shows high sensitivity with a gauge factor of 15 to 29, which is much higher compared to the GF/PDMS strain sensor with a gauge factor of 2.2. It is attributed to the great change in the contact resistance between FGFs over the large contact area, when stretched. In addition to the high sensitivity, the FGF/PDMS strain sensor exhibits high stretchability over 70% and high durability over 10 000 stretching‐releasing cycles. When the sensor is attached to the human body, it functions as a health‐monitoring device by detecting various human motions such as the bending of elbows and fingers in addition to the pulse of radial artery. Finally, by using the FGF, PDMS, and μ‐LEDs, a stretchable touch sensor array is fabricated, thus demonstrating its potential application as an artificial skin. 相似文献
64.
Pradeep Bhartiya Neha Kaushik Linh N. Nguyen Sander Bekeschus Kai Masur Klaus-Dieter Weltmann Nagendra Kumar Kaushik Eun Ha Choi 《International journal of molecular sciences》2022,23(6)
Excess amounts of redox stress and failure to regulate homeostatic levels of reactive species are associated with several skin pathophysiologic conditions. Nonmalignant cells are assumed to cope better with higher reactive oxygen and nitrogen species (RONS) levels. However, the effect of periodic stress on this balance has not been investigated in fibroblasts in the field of plasma medicine. In this study, we aimed to investigate intrinsic changes with respect to cellular proliferation, cell cycle, and ability to neutralize the redox stress inside fibroblast cells following periodic redox stress in vitro. Soft jet plasma with air as feeding gas was used to generate plasma-activated medium (PAM) for inducing redox stress conditions. We assessed cellular viability, energetics, and cell cycle machinery under oxidative stress conditions at weeks 3, 6, 9, and 12. Fibroblasts retained their usual physiological properties until 6 weeks. Fibroblasts failed to overcome the redox stress induced by periodic PAM exposure after 6 weeks, indicating its threshold potential. Periodic stress above the threshold level led to alterations in fibroblast cellular processes. These include consistent increases in apoptosis, while RONS accumulation and cell cycle arrest were observed at the final stages. Currently, the use of NTP in clinical settings is limited due to a lack of knowledge about fibroblasts’ behavior in wound healing, scar formation, and other fibrotic disorders. Understanding fibroblasts’ physiology could help to utilize nonthermal plasma in redox-related skin diseases. Furthermore, these results provide new information about the threshold capacity of fibroblasts and an insight into the adaptation mechanism against periodic oxidative stress conditions in fibroblasts. 相似文献
65.
Rupak K. Banerjee Madhura Karve Jong Ho Ha Dong Hwan lee Young I. Cho 《Numerical Heat Transfer, Part A: Applications》2013,63(10):735-753
Air cooled steam condensers (ACSC) consist of finned-tube arrays bundled in an A-frame structure. Inefficient performance under extreme temperature operating conditions is a common problem in ACSCs. The purpose of this study was to improve the heat transfer characteristics of an annular finned-tube system for better performance in extreme climatic conditions. Perforations were created on the surface of the annular fins to increase heat transfer coefficient (h). Mesh generation and finite volume analyses were performed using Gambit 2.4.6 and Fluent 6.3 with an RNG k–? turbulent model to calculate pressure drop (ΔP), heat flux (q), and heat transfer coefficient (h). Solid (no perforations) finned-tubes were simulated with free stream velocity ranging between 1 m/s–5 m/s and validated with the published data. Computations were performed for perforations at 30° interval starting at ±60°, ±90°, ±120°, ±150°, and ±180° from the stagnation point. Five cases with single perforation and three cases with multiple perforations were evaluated for determining the maximum q and h, as well as minimum ΔP. For the perforated case (perforations starting from 60° at interval of 30°), the fin q and h performance ratios increased by 5.96% and 7.07%, respectively. Consequently, the fin ΔP performance ratio increased by 11.87%. Thus, increased q and h is accompanied with a penalty of higher ΔP. In contrast, a single perforation location at 120° provided favorable results with a 1.70% and 2.23% increase in q and h performance ratios, respectively, while there was a relatively smaller increase (only 1.39%) of ΔP performance ratio. Perforations in the downstream region at ±120°, ±150°, and ±180° also resulted in a similar favorable outcome. Furthermore, the spacing of the fins along the arms of an A-frame ACSC was altered to decrease ΔP across the finned-tube array. Fin spacing in the A-frame structure with sparsely spaced fins in the center resulted in a 1.80% reduction in ΔP. Thus, penalty in ΔP for a perforated fin can possibly be offset by changing the fin spacing along the arms of an A-frame structure. 相似文献
66.
The electrical resistance of bipolar plates for polymer–electrolyte membrane fuel cells (PEMFCs) should be very low to conduct the electricity generated with minimum electrical loss. The resistance of a bipolar plate consists of the bulk material resistance and the interfacial contact resistance when two such plates are contacted to provide channels for fuel and air (oxygen) supplies. 相似文献
67.
An Impulse-time Perturbation Approach for a Symmetric Extra-insensitive Input Shaper 总被引:1,自引:0,他引:1
Ha Chang-Wan Lee Dongwook Rew Keun-Ho Kim Kyung-Soo 《International Journal of Control, Automation and Systems》2018,16(3):1239-1246
International Journal of Control, Automation and Systems - In this study, symmetric perturbation extra-insensitive input shapers (SPEI-ISs) are proposed to enhance the robustness of the... 相似文献
68.
The structural shape of the interface between a metal and dielectric material in a triboelectric nanogenerator (TENG) is an important factor that can improve the device performance. Many interfacial structures have been developed to improve the TENG performance. However, there have been very few studies on the numerical interpretation of various types of contact interfaces. For various interfacial structures on which uniform triboelectric charge density is distributed, the surface charge density (in-plane, out-of-plane, and total) is systematically analyzed to predict the quantity of the transferred charges on the bottom metal under a short-circuit condition. In this work, a numerical study is conducted using a finite element method. The numerical results confirm that the increase in the quantity of the transferred charges collected on the bottom metal via electrostatic induction is related to the increase in the area of the surface structures (i.e., surface enlargement effect due to the formation of complex interfacial morphology). The estimated magnitude of the transferred charges shows the following decreasing trend for the various structural shapes: rectangle > cylinder > pyramid > cone > flat. 相似文献
69.
70.
This paper proposes the Internet connectivity of RF-powered devices in the backscatter system. The RF-powered devices do not use a battery and charge energy by harvesting from ambient RF signals of TV, a cellular phone and Wi-Fi devices. The Internet connectivity of the RF-powered devices in the backscatter system is very useful in Internet of things technology because the RF-powered devices which are called to a tag have a small size by the harvesting from ambient RF signals without a battery. This paper proposes a method improving the communication performance of the Wi-Fi backscatter system by applying the cooperative communication scheme.
相似文献