全文获取类型
收费全文 | 3347篇 |
免费 | 261篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 21篇 |
综合类 | 4篇 |
化学工业 | 823篇 |
金属工艺 | 135篇 |
机械仪表 | 229篇 |
建筑科学 | 53篇 |
能源动力 | 124篇 |
轻工业 | 377篇 |
水利工程 | 27篇 |
石油天然气 | 2篇 |
无线电 | 566篇 |
一般工业技术 | 677篇 |
冶金工业 | 178篇 |
原子能技术 | 38篇 |
自动化技术 | 367篇 |
出版年
2024年 | 3篇 |
2023年 | 58篇 |
2022年 | 73篇 |
2021年 | 119篇 |
2020年 | 95篇 |
2019年 | 107篇 |
2018年 | 112篇 |
2017年 | 133篇 |
2016年 | 177篇 |
2015年 | 116篇 |
2014年 | 193篇 |
2013年 | 245篇 |
2012年 | 251篇 |
2011年 | 301篇 |
2010年 | 223篇 |
2009年 | 180篇 |
2008年 | 193篇 |
2007年 | 154篇 |
2006年 | 126篇 |
2005年 | 106篇 |
2004年 | 74篇 |
2003年 | 74篇 |
2002年 | 79篇 |
2001年 | 76篇 |
2000年 | 48篇 |
1999年 | 50篇 |
1998年 | 83篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有3621条查询结果,搜索用时 0 毫秒
91.
92.
Hyeondeuk Yong Kiyeol Kim Wooseok Choi Joonkyu Park Muneer Ahmad Yongho Seo 《Carbon》2012,50(12):4640-4647
A graphene cellular array on an insulating SiO2 layer was fabricated by scanning probe lithography. The graphene layer was oxidized by an electric field which was applied between the cantilever tip and Si substrate without any electrode directly connected to the graphene layer. When the bias voltage was applied on a cell of patterned graphene through the cantilever tip, charge was accumulated on the cell and preserved for a long time without decay. The accumulated charge and the surface potential were measured by an electrostatic force microscope. The charge retention was measured as a function of time, and the decay time constant was estimated to be ~70 min. 相似文献
93.
94.
Jung-hyun Seo 《The Journal of supercomputing》2013,64(3):987-1007
A two-dimensional (2D) Petersen-torus network is a mesh-class fixed-degree network designed using a Petersen graph, which has a maximum of 10 nodes when the degree is 3 and the diameter is 2 in a (d,k)-graph problem. Here, I propose a new three-dimensional (3D) Petersen-torus network that extends the 2D Petersen-torus network without increasing the degree. The 3D Petersen-torus has the same number of nodes (N). The 3D Petersen-torus is better than the well-known 3D torus and 3D honeycomb mesh in terms of diameter and network cost. The 3D Petersen-torus network is better than the hypercube-like and star graph-like networks in terms of extendibility. Hence, the proposed network may serve as the foundation for realizing a high-performance multicomputer. In this paper, the optimal routing algorithm, Hamilton cycle, and several basic attributes are discussed. Furthermore, a comparison with a mesh-class fixed-degree 3D network is made for degree, diameter, and network cost. 相似文献
95.
The gelling temperature of Poloxamer 407/Poloxamer 188 (16%/10%) mixture solution increased with increasing amount of surfactants. Among surfactants tested, the order of effectiveness in increasing the gelling temperature was sodium dodecyl sulfate (SDS) > tween 20 > cetyltrimethylammonium chloride (CTAC). The gelling temperature increased with the increasing concentration of cyclodextrin (CD). The order of effectiveness in increasing the gelling temperature was gamma CD > beta CD > alpha CD. The gelling temperature increased with increasing concentration of alcohols (ethanol and propylene glycol (PG)). On the contrary, dimethyl sulfoxide (DMSO) decreased the gelling temperature of P407/P188 (16%/10%) mixture solution. On the other hand, the gelling temperature decreased upon addition of NaCl but it increased by addition of MgCl2. With P407/P188-loaded monoolein cubic phase, the degrees of release in 40 hr were about 52% at 25 °C and 37.5% at 47 °C. The suppressed release at 47 °C is possibly because P407/P188 in the water channel of cubic phase is in gel state at the temperature. 相似文献
96.
Byung Hoon Jo Jaoon Y.H. Kim Jeong Hyun Seo Hyung Joon Cha 《International Journal of Hydrogen Energy》2014
H2 production under aerobic conditions has been proposed as an alternative method to overcome the fundamentally low yield of H2 production by fermentative bacteria by maximizing the number of electrons that are available for H2. Here, we engineered Vitreoscilla hemoglobin (VHb) in Escherichia coli to study the effects of this versatile oxygen (O2)-binding protein on oxic H2 production in a closed batch system that was supplemented with glucose. The H2 yields that were obtained with the VHb-expressing E. coli were greatly enhanced in comparison to the negative control cells in culture that started with high O2 tensions. The formate hydrogen lyase (FHL) activity of oxically cultured, VHb-expressing cells was also much higher than that of the negative control cells. Through inhibitor studies and time-course experiments, VHb was shown to contribute to the improved H2 yield primarily by increasing the efficiency of cellular metabolism during the aerobic phase before the onset of H2 production and not by working as an O2-scavenger during H2 production. This new approach allowed more substrate to remain to be further utilized for the production of more H2 from limited resources. We expect that VHb can be successfully engineered in potential aerobic H2-producing microbial systems to enhance the overall H2 production yield. In addition, the remarkably high FHL activity of oxically grown, VHb-expressing cells may make this engineered strain an attractive whole-cell biocatalyst for converting formate to H2. 相似文献
97.
When the number of users is finite, the performance improvement of the orthogonal random beamforming (ORBF) scheme is limited in high signal‐to‐noise ratio regions. In this paper, to improve the performance of the ORBF scheme, the user set and transmit power allocation are jointly determined to maximize sum rate under the total transmit power constraint. First, the transmit power allocation problem is expressed as a function of a given user set. Based on this expression, the optimal user set with the maximum sum rate is determined. The suboptimal procedure is also presented to reduce the computational complexity, which separates the user set selection procedure and transmit power allocation procedure. 相似文献
98.
Kwan-Ho Park Sin-Wook You Soon-Chul Ur Il-Ho Kim Soon-Mok Choi Won-Seon Seo 《Journal of Electronic Materials》2012,41(6):1051-1056
The thermal stability of skutterudite-based thermoelectric modules is of great importance since they are used at elevated temperatures. This study examined the high-temperature stability of In-filled and Fe-doped skutterudites (In0.25Co3FeSb12) as a function of the following aging variables: atmosphere (vacuum and air), temperature, and time. Sb-based oxides are produced preferentially on exposure to high temperatures in air. The oxide layer produced during aging at 823?K in air was much thinner than that produced during aging at 723?K in air. The formation of InSb is believed to retard the oxidation of Sb and act as an obstacle to the growth of the oxide layer. The CoSb3-based skutterudites were stable at 823?K if they were not exposed to air, and InSb phases were not produced in the In0.25Co3FeSb12 skutterudites. 相似文献
99.
Myoung Do Seo Young Jo Kim Jong Sung Lim Jeong Won Kang 《Korean Journal of Chemical Engineering》2012,29(1):103-110
Vapor-liquid equilibrium (VLE) for binary mixtures composed of ethanol+methyl isobutyl ketone, 1-butanol+ methyl ethyl ketone,
and 1-butanol+methyl propyl ketone systems was measured using a circulation type equilibrium apparatus at atmospheric pressure.
The measured data and literature data for alcohol and ketone systems have been correlated by the UNIversal Quasi-Chemical
(UNIQUAC) model with two binary interaction parameters and the non-random lattice fluid equation of state with hydrogen bonding
equation of state (NLF-HB EoS) using a single binary interaction parameter. For the NLF-HB EoS calculations, the numbers of
proton acceptor for ketones were adjusted between 0 and 1. The calculation results with the NLF-HB EoS are better than those
with the UNIQUAC model. 相似文献
100.
The antioxidant activities and nutritional properties of Jeonyak made with beef bone stock and gelatin were investigated. Traditional Jeonyak (J1) was prepared with beef bone stock, whereas modified Jeonyak was made with gelatin and honey (J2) or with gelatin and oligosaccharides (J3). All 3 kinds of Jeonyak had antioxidant activities and J1 had the highest activity. The α-glucosidase inhibitory activity was measured to investigate the antidiabetic effect and J3 had the highest inhibitory activity of 80.47%. Glycine was the most abundant amino acid in all 3 kinds of Jeonyak. Both traditional and modified Jeonyaks have antioxidative and antidiabetic effects, suggesting that Jeonyak can be used as an effective traditional functional food. 相似文献