全文获取类型
收费全文 | 1975篇 |
免费 | 641篇 |
国内免费 | 135篇 |
专业分类
电工技术 | 40篇 |
综合类 | 94篇 |
化学工业 | 741篇 |
金属工艺 | 229篇 |
机械仪表 | 108篇 |
建筑科学 | 25篇 |
矿业工程 | 25篇 |
能源动力 | 156篇 |
轻工业 | 133篇 |
水利工程 | 17篇 |
石油天然气 | 58篇 |
武器工业 | 23篇 |
无线电 | 232篇 |
一般工业技术 | 701篇 |
冶金工业 | 31篇 |
原子能技术 | 67篇 |
自动化技术 | 71篇 |
出版年
2024年 | 19篇 |
2023年 | 101篇 |
2022年 | 108篇 |
2021年 | 126篇 |
2020年 | 191篇 |
2019年 | 174篇 |
2018年 | 177篇 |
2017年 | 142篇 |
2016年 | 144篇 |
2015年 | 163篇 |
2014年 | 159篇 |
2013年 | 213篇 |
2012年 | 138篇 |
2011年 | 158篇 |
2010年 | 79篇 |
2009年 | 90篇 |
2008年 | 85篇 |
2007年 | 78篇 |
2006年 | 67篇 |
2005年 | 64篇 |
2004年 | 56篇 |
2003年 | 37篇 |
2002年 | 19篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1985年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有2751条查询结果,搜索用时 15 毫秒
51.
52.
Recapillarity: Electrochemically Controlled Capillary Withdrawal of a Liquid Metal Alloy from Microchannels 下载免费PDF全文
This paper describes the mechanistic details of an electrochemical method to control the withdrawal of a liquid metal alloy, eutectic gallium indium (EGaIn), from microfluidic channels. EGaIn is one of several alloys of gallium that are liquid at room temperature and form a thin (nm scale) surface oxide that stabilizes the shape of the metal in microchannels. Applying a reductive potential to the metal removes the oxide in the presence of electrolyte and induces capillary behavior; we call this behavior “recapillarity” because of the importance of electrochemical reduction to the process. Recapillarity can repeatably toggle on and off capillary behavior by applying voltage, which is useful for controlling the withdrawal of metal from microchannels. This paper explores the mechanism of withdrawal and identifies the applied current as the key factor dictating the withdrawal velocity. Experimental observations suggest that this current may be necessary to reduce the oxide on the leading interface of the metal as well as the oxide sandwiched between the wall of the microchannel and the bulk liquid metal. The ability to control the shape and position of a metal using an applied voltage may prove useful for shape reconfigurable electronics, optics, transient circuits, and microfluidic components. 相似文献
53.
I. C. Kemp T. Hartwig R. Herdman P. Hamilton A. Bisten S. Bermingham 《Drying Technology》2016,34(10):1243-1252
This article presents experimental and modeling work to complete previously reported work on spray drying. Back-calculated droplet sizes have been verified by measurements with a laser imaging rig. Flow patterns in a cylindrical spray chamber have been simulated by computational fluid dynamics and demonstrated that droplet residence times are much shorter than expected. A droplet tracking population balance model has been implemented in gSOLIDS and shows how drying times vary with droplet diameter. Particle collection by cyclone and bag filter have also been compared experimentally. 相似文献
54.
55.
感应式水雾荷电及其捕尘效应的研究 总被引:3,自引:0,他引:3
本文阐述感应式水雾荷电的原理及结构要素,分析了荷电雾粒的捕尘机制,并指明感应式水雾荷电除尘器提高除尘效率的技术途径。 相似文献
56.
Fuquan LI Chunqing WANG Yanhong TIAN 《材料科学技术学报》2006,22(3):392-396
The interracial phenomena of the Sn-Pb solder droplet on and needle-like AuSn4 are formed at the interface after Au/Ni/Cu pad are investigated. A continuous AuSn2 the liquid state reaction (soldering). The interracial reaction between the solder and Au layer continues during solid state aging with AuSn4 breaking off from the interface and felling into the solder. The kinetics of Au layer dissolution and diffusion into the solder during soldering and aging is analyzed to elucidate intermetallic formation mechanism at the solder/Au pad interface. The concentration of Au near the solder/pad interface is identified to increase and reach the solubility limit during the period of liquid state reaction. During solid state reaction, the thickening of Au-Sn compound is mainly controlled by element diffusion. 相似文献
57.
Emine Kaplanoglu Igor Kolotilin Rima Menassa Cam Donly 《International journal of molecular sciences》2022,23(7)
Plant-mediated RNA interference (RNAi) holds great promise for insect pest control, as plants can be transformed to produce double-stranded RNA (dsRNA) to selectively down-regulate insect genes essential for survival. For optimum potency, dsRNA can be produced in plant plastids, enabling the accumulation of unprocessed dsRNAs. However, the relative effectiveness of this strategy in inducing an RNAi response in insects using different feeding mechanisms is understudied. To investigate this, we first tested an in vitro-synthesized 189 bp dsRNA matching a highly conserved region of the v-ATPaseA gene from cotton mealybug (Phenacoccus solenopsis) on three insect species from two different orders that use leaf-chewing, lacerate-and-flush, or sap-sucking mechanisms to feed, and showed that the dsRNA significantly down-regulated the target gene. We then developed transplastomic Micro-tom tomato plants to produce the dsRNA in plant plastids and showed that the dsRNA is produced in leaf, flower, green fruit, red fruit, and roots, with the highest dsRNA levels found in the leaf. The plastid-produced dsRNA induced a significant gene down-regulation in insects using leaf-chewing and lacerate-and-flush feeding mechanisms, while sap-sucking insects were unaffected. Our results suggest that plastid-produced dsRNA can be used to control leaf-chewing and lacerate-and-flush feeding insects, but may not be useful for sap-sucking insects. 相似文献
58.
Zhaoyuan Zhu Li Zhang Ruilong Sheng Jian Chen 《International journal of molecular sciences》2022,23(7)
Safe and efficient delivery of small interfering RNA (siRNA) is essential to gene therapy towards intervention of genetic diseases. Herein, we developed a novel cationic cholesterol lipid derivative (CEL) in which cholesterol hydrophobic skeleton was connected to L-lysine cationic headgroup via a hexanediol linker as the non-viral siRNA delivery carrier. Well-organized CEL/siRNA nanocomplexes (100–200 nm) were prepared by microfluidic-assisted assembly of CEL and siRNA at various N/P ratios. The CEL and CEL/siRNA nanocomplexes have lower cytotoxicity compared with bPEI25k. Delightfully, we disclosed that, in Hela–Luc and H1299–Luc cell lines, the micro-fluidic-based CEL/siRNA nanocomplexes exhibited high siRNA transfection efficiency under both serum-free condition (74–98%) and low-serum circumstances (80–87%), higher than that of lipofectamine 2000. These nanocomplexes also showed high cellular uptake through the caveolae/lipid-raft mediated endocytosis pathway, which may greatly contribute to transfection efficiency. Moreover, the time-dependent (0–12 h) dynamic intracellular imaging demonstrated the efficient delivery to cytoplasm after lysosomal co-localization. The results indicated that the microfluidic-based CEL/siRNA nanosystems possessed good stability, low cytotoxicity, high siRNA delivery efficiency, rapid cellular uptake and caveolae/lipid raft-dependent internalization. Additionally, this study provides a simple approach for preparing and applying a “helper lipid-free” cationic lipid siRNA delivery system as potential nanotherapeutics towards gene silencing treatment of (tumor) diseases. 相似文献
60.
Effect of Ultra-high-pressure Homogenization on Structure and on Rheological Properties of Soy Protein-stabilized Emulsions 总被引:2,自引:0,他引:2
ABSTRACT: An ultra high-pressure homogenizer (20 to 350 MPa) was used to realize fine food emulsions stabilized by soy proteins. The first aim of the work was to understand how dynamic high-pressure processing affects soybean globulin conformation. Then, the effect of homogenizing pressure on the emulsions structure and rheology was investigated. High-pressure homogenization caused denaturation of proteins due to strong mechanical forces and high temperatures encountered in the valve. Droplet sizes of emulsions were greatly reduced with high-pressure homogenization and Newtonian liquid emulsions were converted into shear-thinning emulsion gels by homogenization at pressures above 250 MPa. Hydrophobic interactions between proteins were supposed to cause the gel-like network structure of emulsions. 相似文献