首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   199667篇
  免费   2307篇
  国内免费   613篇
电工技术   3468篇
综合类   149篇
化学工业   28960篇
金属工艺   8049篇
机械仪表   6068篇
建筑科学   4811篇
矿业工程   1303篇
能源动力   5127篇
轻工业   17115篇
水利工程   2297篇
石油天然气   4040篇
武器工业   8篇
无线电   23066篇
一般工业技术   40012篇
冶金工业   37227篇
原子能技术   5086篇
自动化技术   15801篇
  2021年   1605篇
  2019年   1568篇
  2018年   2573篇
  2017年   2645篇
  2016年   2775篇
  2015年   1794篇
  2014年   3074篇
  2013年   8939篇
  2012年   5050篇
  2011年   7021篇
  2010年   5589篇
  2009年   6350篇
  2008年   6443篇
  2007年   6511篇
  2006年   5579篇
  2005年   5228篇
  2004年   5005篇
  2003年   4887篇
  2002年   4525篇
  2001年   4656篇
  2000年   4578篇
  1999年   4726篇
  1998年   11373篇
  1997年   8120篇
  1996年   6408篇
  1995年   4673篇
  1994年   4271篇
  1993年   4073篇
  1992年   3223篇
  1991年   3076篇
  1990年   2870篇
  1989年   2951篇
  1988年   2826篇
  1987年   2398篇
  1986年   2308篇
  1985年   2715篇
  1984年   2505篇
  1983年   2345篇
  1982年   2090篇
  1981年   2203篇
  1980年   2029篇
  1979年   2124篇
  1978年   2120篇
  1977年   2366篇
  1976年   3188篇
  1975年   1833篇
  1974年   1761篇
  1973年   1772篇
  1972年   1443篇
  1971年   1339篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
71.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time.  相似文献   
72.
In the present work 316LN as well as 316 stainless steel (SS) coupons each of dimensions (0.025 × 0.018 × 0.006 m3) in well-polished condition were used as two nominal electrodes which were immersed in the aerated solution of 0.5 M NaCl. Correlated current and potential electrochemical noise (EN) signals were collected at 1 Hz sampling frequency for 1 h daily over a period of 30 days. The detrended EN data were used to calculate the noise resistance (R N) as well as the spectral noise resistance at zero frequency (R SNo) values and other statistical parameters. To study the nature of pits and distribution of their diameters as well as depths, extensive observations of the pitted and the blank specimens were carried out using Confocal Laser Scanning Microscopy (CLSM). The current and the potential records of the two alloys showed distinct differences in their corrosion behavior. It was observed that within less than 4 h of immersion, 316SS showed signals indicative of unstable pitting and onset of stable pitting was noticed after 48 h of exposure. However, until about 24 h, 316LN showed just the random signals and unstable pitting was observed after 28 h. The signals clearly indicated continuous growth of the stable pits in 316SS as against the repassivation of the unstable pits in 316LN after 7 days exposure. It was observed that R N values showed a continuous decrease in the case of 316SS, but were quite stable in the case of 316LN over the exposure period. Concurrent to these observations it was observed that 316SS specimen was extensively pitted. The frequency distributions of pit diameters as well pit depths were observed to be highest at 10-20 μm and 5-10 μm, respectively. However, pits with as large as 70-80 μm diameter and as deep as 20-25 μm too were observed. No pits were observed in case of 316LN even after 30 days of exposure, an observation that corroborates well with the stable R N values. Thus, in the present investigation, the long-term tests using EN technique coupled with CLSM studies conclusively prove that many unstable pits initiated in 316SS turn into stable ones resulting in insidious localized corrosion attack whereas the unstable pits initiated in 316LN get passivated in the simulated coastal environment.  相似文献   
73.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress.  相似文献   
74.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals.  相似文献   
75.
Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on. Translated from Novye Ogneupory, No. 4, pp. 64–67, April, 2008.  相似文献   
76.
Results are presented on the corrosion resistance of chromium-bearing refractories of granular structure acted on by corrosive molten slags, metals, and glasses. It is possible to recommend these refractories to customers for particular conditions of use. Chromium-bearing refractories increase the working lives of furnaces considerably. __________ Translated from Novye Ogneupory, No. 1, pp. 55–61, January, 2008.  相似文献   
77.
The processes of phase formation in the Na2CO3-TiO2 and Na2CO3-TiO2-Nd2O3 systems are investigated in the temperature range 600–900°C. The high-temperature solid-phase reactions underlying the process of formation of complex oxide NaNdTiO4 are studied. It is established that the synthesis of the NaNdTiO4 compound occurs through the reaction of the intermediate product Na8Ti5O14 with neodymium oxide in the temperature range 720–780°C. The optimum method is proposed for synthesizing NaNdTiO4, which makes it possible to reduce the temperature of the synthesis, to avoid the formation of impurities, and to obtain the product in a finely dispersed state.  相似文献   
78.
Phase transitions are considered for silicon oxycarbide material between joints in hearth blocks under aluminum electrolyzer operating conditions. It is established that in the electrolyzer there is formation of aluminum subcarbide, and also there is conversion of silicon carbide polytypes as a result of impurities of aluminum, sodium, magnesium, copper and iron. Due to phase transitions there is a reduction in joint strength, and therefore it is undesirable to use material based on corundum and black silicon carbide in hearth joints between blocks for aluminum electrolyzers. Use of pure α-SiO2 free from impurities is recommended for this purpose. Translated from Novye Ogneupory, No. 4, pp. 47–52, April 2008.  相似文献   
79.
Nanosized (2–8 nm) amorphous powders of the solid solution based on zirconia and hafnia are synthesized through back coprecipitation upon treatment of gels at temperatures from +20 to −77°C. Heat treatment of these powders at temperatures up to 1000 and above 1100°C leads to the formation of cubic (fluorite type, O h 5 = Fm3m) and tetragonal phases of the Zr82Hf10Y3Ce5O x composition, respectively. It is revealed that a decrease in the synthesis temperature (from +20°C to −6°C) results in a decrease in the size of gel agglomerates from 30 to 1 μm. Recrystallization processes in the gels prepared using cryochemical treatment are developed very slowly in the temperature range 500–1200°C (the crystallite size does not exceed 25 nm). Original Russian Text ? T.I. Panova, V.B. Glushkova, A.E. Lapshin, 2008, published in Fizika i Khimiya Stekla.  相似文献   
80.
Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N2-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.   相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号