全文获取类型
收费全文 | 1193篇 |
免费 | 29篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 111篇 |
化学工业 | 356篇 |
金属工艺 | 51篇 |
机械仪表 | 42篇 |
建筑科学 | 37篇 |
能源动力 | 59篇 |
轻工业 | 117篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 71篇 |
一般工业技术 | 207篇 |
冶金工业 | 27篇 |
原子能技术 | 39篇 |
自动化技术 | 110篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 18篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 31篇 |
2013年 | 78篇 |
2012年 | 56篇 |
2011年 | 84篇 |
2010年 | 47篇 |
2009年 | 80篇 |
2008年 | 80篇 |
2007年 | 47篇 |
2006年 | 50篇 |
2005年 | 39篇 |
2004年 | 45篇 |
2003年 | 52篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 25篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1980年 | 4篇 |
1979年 | 18篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有1231条查询结果,搜索用时 15 毫秒
181.
Hitoshi Matsuoka Boping Liu Hisayuki Nakatani Isa Nishiyama Minoru Terano 《Polymer International》2002,51(9):781-784
To investigate the role of the internal donor in a Ziegler–Natta catalyst, the nature and existing states of the internal donor were intentionally varied by alkylaluminium treatment before polymerization, and the catalytic properties during propene polymerization were accurately evaluated using the stopped‐flow method. A significant decrease in the amount of the remaining internal donor was observed during the initial stage of the extraction. The polymerization results show a gradual decrease in the polymer isotacticity with an increase in the extraction time. These different patterns, as a function of the extraction time, indicate that the amount of the remaining internal donor is not directly related to the isotacticity of the produced polymer. © 2002 Society of Chemical Industry 相似文献
182.
Fukuyama Y Yasuda N Kim J Murayama H Ohshima T Tanaka Y Kimura S Kamioka H Moritomo Y Toriumi K Tanaka H Kato K Ishikawa T Takata M 《The Review of scientific instruments》2008,79(4):045107
An ultra-high-precision clock system for long time delay has been developed for picosecond time-resolved x-ray diffraction measurements using synchrotron radiation (SR) pulses and synchronized femtosecond laser pulses. The time delay control between pump laser pulse and the probe SR pulse was achieved by combining an in-phase quadrature modulator and a synchronous counter. This method allowed us to change the delay time by a nearly infinite amount while maintaining the precision of +/-8.40 ps. Time-resolved diffraction measurements using the delay control system were demonstrated for precise measurement of an acoustic velocity in a single crystal of gallium arsenide. 相似文献
183.
Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a corrosion product diffuses to the environment including the salt was suggested in Bi0.5Sb1.5Te3. However, the amount of dissolved corrosion product was very low, and the chemical stability of the corrosion product was not changed or improved by element substitution. 相似文献
184.
Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jae Hyeon Jo Ji Ung Choi Aishuak Konarov Hitoshi Yashiro Shuai Yuan Liyi Shi Yang‐Kook Sun Seung‐Taek Myung 《Advanced functional materials》2018,28(14)
Surface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na2/3[Ni1/3Mn2/3]O2 is modified with ionic, conducting sodium phosphate (NaPO3) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH4H2PO4 with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na+/Na, the NaPO3‐coated Na2/3[Ni1/3Mn2/3]O2/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO3 nanolayers positively impact the cell performance by scavenging HF and H2O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO3 coating layer is delayed for decomposition to Mn3O4, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries. 相似文献
185.
Predicting Solid–Liquid Equilibrium of Fatty Acid Methyl Ester and Monoglyceride Mixtures as Biodiesel Model Fuels
下载免费PDF全文
![点击此处可从《Journal of the American Oil Chemists](/ch/ext_images/free.gif)
Shinichiro Yoshidomi Yuitsu Sugami Eiji Minami Noriko Shisa Hitoshi Hayashi Shiro Saka 《Journal of the American Oil Chemists' Society》2017,94(8):1087-1094
Fatty acid methyl esters from plant oils are the main component of biodiesel and used as a substitute for petroleum diesel. Biodiesel generally contains a small amount of monoglycerides as intermediate compounds, which have high melting points and often solidify and clog fuel filters. The prediction of the cold-flow property of biodiesel is of great importance for practical application. In this study, a thermodynamic study was conducted for mixtures of monoglycerides and fatty acid methyl esters. Temperatures of the solid–liquid equilibrium for the mixtures were measured by differential scanning calorimetry and visual observation, while the theoretical values were calculated using the modified Universal Quasi-chemical Functional-group Activity Coefficients (UNIFAC) model (Dortmund). The theoretical and experimental results were in good agreement, especially for binary mixtures of monoglycerides and methyl esters. The importance of monoglycerides on the cold-flow properties of biodiesel was determined, and the effects could be well described by the modified UNIFAC model (Dortmund). 相似文献
186.
应用柔性拉索的非线性振动响应计算理论,提出考虑横向脉动风荷载作用及支点激励的拉索非线性振动计算方法。以力学特性不同的两种斜拉索为对象,通过数值方法分析横风作用和支点激励下的钢索、CFRP拉索非线性振动响应,比较支点激励频率、风速、阻尼器对参数振动响应的影响。结果表明,在拉索基频f1以及两倍基频2f1的支点位移激励下,脉动风虽然导致拉索出现不规则的竖向和横向水平振动轨迹,但不会改变拉索的参数振动特性;横向风荷载对参数振动具有空气阻尼力的效应;总体上CFRP拉索的参数振动振幅小于钢索,特别当拉索跨度比较大时,CFRP拉索的振幅将明显低于同跨度的钢索;黏性阻尼装置的减振效果与拉索的结构条件有关,当拉索的无量纲参数λ(Irvine参数)较大时,阻尼器的减振效果不明显,反之当λ较小时阻尼器有一定的减振效果。 相似文献
187.
188.
Yasuyuki Okimura Hitoshi Yokoi Kazushige Ohbayashi Ken-ichi Shimizu Atsushi Satsuma Tadashi Hattori 《Catalysis Letters》1998,52(3-4):157-161
Selective reduction of NO with hydrocarbons was studied using metal oxide catalysts having a spinel structure. A Zn–Al–Ga
complex oxide was found to be very active and selective for the catalytic reduction of NO with both C3H6 and CH4. It was revealed that the role of oxygen at the initial stage of the reaction strongly depends on the reductants; oxygen
is mainly used for NO oxidation to NO2 in the reduction with CH4, whereas it is used both for NO oxidation to NO2 and oxidation of C3H6 to an active intermediate in the reduction with C3H6.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
189.
190.
Nobuhide Itoh Hitoshi Ohmori Sei Moriyasu Toshio Kasai Toshiro Karaki-Doy B.P. Bandyopadhyay 《International Journal of Machine Tools and Manufacture》1998,38(7):747-762
ELID-lap grinding is a method of constant pressure grinding which utilizes an electrically conductive wheel and the electrolytic in-process dressing (ELID) method. This method has the advantage of using micro grain-wheels above #10 000 and also, through simple modification, can be used on existing lap machines. To find the characteristics of metal-resin bonded wheels developed for ELID-lap grinding, experiments on the grinding of brittle materials were performed using wheels with a variety of grain diameters. The wheels used in the experiments were #8000, #120 000 and #3 000 000 metal-resin bonded diamond wheels (#8000 MRB-D, #120 000 MRB-D and #3 000 000 MRB-D wheels). The workpieces were silicon and glass. The results of the experiments showed that stable grinding can be achieved with the #8000 to #3 000 000 MRB-D wheels. With the #3 000 000 MRB-D wheel, very smooth surface finishes were obtained for both silicon (PV 2.8 nm) and glass (PV 2.5 nm). Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) observations indicated these surfaces to be very smooth in the order of several nanometers, obtained by mechanical removal using an ultrafine wheel. 相似文献