全文获取类型
收费全文 | 2344篇 |
免费 | 92篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 39篇 |
综合类 | 1篇 |
化学工业 | 420篇 |
金属工艺 | 52篇 |
机械仪表 | 53篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 121篇 |
轻工业 | 83篇 |
水利工程 | 15篇 |
石油天然气 | 39篇 |
无线电 | 521篇 |
一般工业技术 | 411篇 |
冶金工业 | 176篇 |
原子能技术 | 14篇 |
自动化技术 | 459篇 |
出版年
2023年 | 35篇 |
2022年 | 91篇 |
2021年 | 80篇 |
2020年 | 59篇 |
2019年 | 60篇 |
2018年 | 92篇 |
2017年 | 75篇 |
2016年 | 66篇 |
2015年 | 68篇 |
2014年 | 79篇 |
2013年 | 177篇 |
2012年 | 106篇 |
2011年 | 98篇 |
2010年 | 108篇 |
2009年 | 78篇 |
2008年 | 80篇 |
2007年 | 77篇 |
2006年 | 72篇 |
2005年 | 67篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 55篇 |
2001年 | 31篇 |
2000年 | 45篇 |
1999年 | 39篇 |
1998年 | 70篇 |
1997年 | 50篇 |
1996年 | 36篇 |
1995年 | 41篇 |
1994年 | 42篇 |
1993年 | 38篇 |
1992年 | 23篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有2441条查询结果,搜索用时 31 毫秒
101.
102.
Mayank Agrawal 《分离科学与技术》2016,51(3):502-516
In contrast to the different approaches currently adopted for generating basic and side-split subcolumn distillation sequence for separating zeotropic multicomponent feed mixture, we present a unified graphical method applicable towards both basic and side-split subcolumn distillation sequence. For a given number of components in the feed mixture, we enforce constraints on a base graph to eliminate violations of conservation principles and to preclude distillation sequences that demand higher heat duty in all appraised practical scenarios. A compact set of algebraic constraints is transfixed using the graph counterpart for generating basic-only distillation configurations. These algebraic constraints utilize binary variables to quantify existence of submixture streams and this considerably reduces the number of variables in generating distillation sequences. We also suggest extension of the formulation to enable the exploration of thermally coupled configurations. 相似文献
103.
Ashish P. Unnarkat Tam Sridhar Huanting Wang Sanjay Mahajani Akkihebbal K. Suresh 《American Institute of Chemical Engineers》2016,62(12):4384-4402
Oxidation of cyclohexane has been carried out using molecular oxygen over cobalt molybdenum oxide (CoMoO4) catalysts in solvent free conditions. The catalysts were prepared using citrate method with three different molar ratios of Co:Mo, 1:1, 1:2, and 2:1 along with individual oxides for comparative studies. While all the catalysts showed significant activity and selectivity, CoMoO4 with 1:1 ratio showed the best performance compared to the others with a conversion of 7.38%, with selectivity to cyclohexanol and cyclohexanone (KA oil) of 94.3%, in 1 h. The performance of the catalyst, has been studied as a function of oxygen pressure, reaction temperature, and catalyst loading. It was observed that the catalyst deactivates during the course of the reaction. The reasons for deactivation and methods for restoring the activity have been studied. A kinetic model is presented that captures the complex kinetics and matches well with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4384–4402, 2016 相似文献
104.
105.
106.
Gustavo F. Brito Pankaj Agrawal Edcleide M. Araújo Tomás J.A. Mélo 《Polymer Engineering and Science》2014,54(8):1922-1930
Blends of poly(lactic acid) (PLA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (EMA‐GMA) with and without the addition of an organoclay were prepared by melt mixing in a twin screw extruder. Mechanical, morphological, structural, and rheological properties of the systems have been investigated as function of its compositions. The impact strength (IS) of PLA increased with the addition of EMA‐GMA. Furthermore, the addition of 2.5 wt% of organoclay to the PLA/EMA‐GMA blend promoted improvements in the mechanical properties, such as IS, tensile strength, and strain‐at‐break. Further addition of organoclay, 5 wt%, led to a formation of a double percolated network, where the clay particles form bridges across EMA‐GMA droplets and glue them together, however, without coalescence. In addition, morphological and wide‐angle X‐ray scattering analyses evidenced that the clay presents a partially exfoliated structure and that remains inside the EMA‐GMA droplets, probably as a consequence of the approach used to produce the systems. POLYM. ENG. SCI., 54:1922–1930, 2014. © 2013 Society of Plastics Engineers 相似文献
107.
Steven M. McLeod Charles J. Hages Nathaniel J. Carter Rakesh Agrawal 《Progress in Photovoltaics: Research and Applications》2015,23(11):1550-1556
We report a total‐area power conversion efficiency of 15% for a copper indium gallium disulfoselenide (CIGSSe) solar cell fabricated from a copper indium gallium disulfide (CIGS) nanoparticle ink based process. Careful optimization of the fabrication process has resulted in a significant improvement in efficiency compared to our previously reported efficiency of 12%. This efficiency ranks among the highest reported in the literature for solution processed CIGSSe. Despite having an absorber thickness of approximately 700–800 nm, which is less than half the thickness of high efficiency devices grown by both coevaporation and solution processes in the literature, our devices show good short‐circuit current (32.1 mA/cm2). Surprisingly, the sintered film shows lateral composition fluctuations, which have not been reported for other high efficiency devices and may be responsible for the lower open circuit voltage (636 mV) observed here. This suggests an avenue for further improvement through optimization of the nanoparticle selenization process to better control composition in the sintered film. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
108.
Resolving Deep Sub-Wavelength Scattering of Nanoscale Sidewalls Using Parametric Microscopy 下载免费PDF全文
Nagendra Parasad Yadav Ji-Chuan Xiong Wei-Ping Liu Wei-Ze Wang Yun Cao Ashish Kumar Xue-Feng Liu 《电子科技学刊:英文版》2021,19(3):233-242
The quantitative optical measurement of deep sub-wavelength features with sub-nanometer sensitivity addresses the measurement challenge in the semiconductor fabrication process. Optical scatterings from the sidewalls of patterned devices reveal abundant structural and material information. We demonstrated a parametric indirect microscopic imaging (PIMI) technique that enables recovery of the profile of wavelength-scale objects with deep sub-wavelength resolution, based on measuring and filtering the variations of far-field scattering intensities when the illumination was modulated. The finite-difference time-domain (FDTD) numerical simulation was performed, and the experimental results were compared with atomic force microscopic (AFM) images to verify the resolution improvement achieved with PIMI. This work may provide a new approach to exploring the detailed structure and material properties of sidewalls and edges in semiconductor-patterned devices with enhanced contrast and resolution, compared with using the conventional optical microscopy, while retaining its advantage of a wide field of view and relatively low cost. 相似文献
109.
Human development is inherently connected with availability of water and energy. Energy production requires water, whereas water treatment needs energy. On the other hand, microbial fuel cell has capability to produce energy and water simultaneously from waste water or organic matter. In this paper, first principle-based model of variable volume microbial fuel cell is simulated. Hydraulic retention time is selected as the manipulated variable using the study of steady state and dynamic responses. Classical PI and model predictive control strategies are developed for controlling the produced power from the cell, and its performance is tested for servo problem. Settling time for positive and negative set points is found to be 126 and 889 h in case of classical PI and 120 and 750 h in case of linear MPC, respectively along with large increase (three times order of magnitude) in working volume for negative set point. These control challenges are overcome by using split range controller with variable and constant volume microbial fuel cells. The settling time for negative set point is found to be 49 and 21 h for classical PI and linear MPC schemes, respectively, which is significantly lower than using only variable volume microbial fuel cell. Also, there is no increase in the working volume of the constant volume microbial fuel cell. Hence, operating range of the microbial fuel cell is enhanced using split range controller. 相似文献
110.
Rekha Agrawal Jyoti Shah Govind Gupta Ritu Srivastava Chhemendra Sharma Ravinder Kotnala 《应用聚合物科学杂志》2020,137(48):49566
A facile and eco-friendly synthesis of polypyrrole from monomer pyrrole using nominal amount of ferric chloride hexahydrate (FeCl3.6H2O) oxidant in aqueous solution by chemically oxidative polymerization method has been reported. The use of aqueous solvent and ferric chloride hexahydrate salt in polypyrrole synthesis have an eco-friendly route favorable for the production of polypyrrole in large quantities. The synthesized polypyrrole samples exhibit good electrical conductivity (2 S/cm) and yield of 80% for reaction time of 8 hr at 5°C. Quality and properties of polypyrrole samples have been thoroughly investigated with varying reaction time and temperature while other synthesis parameters like molar ratio of oxidant to monomer, oxidant concentration, and solvent were kept constant. X-ray diffraction analysis of polypyrrole with a shorter reaction time shows the presence of iron oxide (Fe2O3) peaks. The complete reaction may not occur at shorter reaction times due to which residual ferric ions converted into Fe2O3. X-ray photoelectron spectroscopy measurement of polypyrrole also confirms the formation of Fe2O3. Appropriate selection of reaction time and temperature produced pure phase polypyrrole with high yield and good conductivity. Synthesized polypyrrole by our eco-friendly and cost-effective technique exhibits prominent electromagnetic shielding effectiveness value of 30 dB in the X-band (8–12 GHz). 相似文献