全文获取类型
收费全文 | 2013篇 |
免费 | 99篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 21篇 |
综合类 | 5篇 |
化学工业 | 563篇 |
金属工艺 | 77篇 |
机械仪表 | 59篇 |
建筑科学 | 38篇 |
矿业工程 | 3篇 |
能源动力 | 122篇 |
轻工业 | 126篇 |
水利工程 | 15篇 |
石油天然气 | 6篇 |
无线电 | 211篇 |
一般工业技术 | 450篇 |
冶金工业 | 195篇 |
原子能技术 | 15篇 |
自动化技术 | 224篇 |
出版年
2024年 | 11篇 |
2023年 | 49篇 |
2022年 | 73篇 |
2021年 | 102篇 |
2020年 | 88篇 |
2019年 | 75篇 |
2018年 | 110篇 |
2017年 | 98篇 |
2016年 | 108篇 |
2015年 | 56篇 |
2014年 | 94篇 |
2013年 | 165篇 |
2012年 | 90篇 |
2011年 | 142篇 |
2010年 | 94篇 |
2009年 | 81篇 |
2008年 | 82篇 |
2007年 | 61篇 |
2006年 | 49篇 |
2005年 | 40篇 |
2004年 | 25篇 |
2003年 | 27篇 |
2002年 | 19篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 29篇 |
1997年 | 31篇 |
1996年 | 29篇 |
1995年 | 25篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1970年 | 2篇 |
排序方式: 共有2130条查询结果,搜索用时 15 毫秒
111.
Multi-objective differential evolution (MODE) is used to optimize an industrial styrene reactor considering productivity, selectivity and yield as the main objectives. Two reactor configurations (single bed adiabatic operation and steam injected pseudo-isothermal operation) and four combinations of objectives consisting of 5 and 7 variables respectively are considered. Pareto optimal solutions are obtained for all combinations of objective functions for both the configurations. The results are compared with those reported in the literature and an industrial operating point. For all the cases considered, MODE is able to give a Pareto front better (in terms of wider range and a better spread) than that obtained using NSGA for both the configurations. Steam injected reactor configuration is better than the adiabatic reactor configuration in terms of performance. The Pareto optimal solutions obtained from such studies provide a wide range of optimal operating conditions from which an appropriate operating point can be selected based on the requirements of the decision maker. 相似文献
112.
Jayakrishna Khatei Naresh Babu PendyalaK.S.R.K. Rao 《Journal of Alloys and Compounds》2011,509(13):4632-4635
This article describes a facile, low-cost, solution-phase approach to the large-scale preparation of Hg1−xCdxTe nanostructures of different shapes such as nanorods, quantum dots, hexagonal cubes of different sizes and different compositions at a growth temperature of 180 °C using an air stable Te source by solvothermal technique. The XRD spectrum shows that the crystals are cubic in their basic structure and reveals the variation in lattice constant as a function of composition. The size and morphology of the products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of irregular shaped particles and few nano-rods in the present synthesis is attributed to the cetyl trimethylammonium bromide (CTAB). The room temperature FTIR absorption and PL studies for a compositon of x = 0.8 gives a band gap of 1.1 eV and a broad emission in NIR region (0.5-0.9 eV) with all bands attributed to surface defects. 相似文献
113.
Jeremy M. Rathfon Zoha M. AL‐Badri Raja Shunmugam Scott M. Berry Santosh Pabba Robert S. Keynton Robert W. Cohn Gregory N. Tew 《Advanced functional materials》2009,19(5):689-695
The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro‐Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub‐micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices. 相似文献
114.
S. Tzamtzis N.S. Barekar N. Hari Babu J. Patel B.K. Dhindaw Z. Fan 《Composites Part A》2009,40(2):144-151
Particulate metal matrix composites (PMMCs) have attracted interest for application in numerous fields. The current processing methods often produce agglomerated particles in the ductile matrix and as a result these composites exhibit extremely low ductility. The key idea to solve the current problem is to adopt a novel Rheo-process allowing the application of sufficient shear stress (τ) on particulate clusters embedded in liquid metal to overcome the average cohesive force or the tensile strength of the cluster. In this study, cast A356/SiCp composites were produced using a conventional stir casting technique and a novel Rheo-process. The microstructure and properties were evaluated. The adopted Rheo-process significantly improved the distribution of the reinforcement in the matrix. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (ε) is obtained. 相似文献
115.
In this letter, the authors present the process, growth kinetics, and electrical characteristics of tunnel oxides grown by furnace oxidation of silicon at 800 degC in an ambient of nitrous oxide (N2O) and water vapor. Tunnel oxides of thickness 82-92 Aring are grown by this "wet N2O oxidation" process, and the electrical characteristics such as the capacitance-voltage, current-voltage, voltage ramp, time-dependent dielectric breakdown, and charge to breakdown are evaluated using MOS capacitor as the diagnostic device. The results obtained clearly demonstrate superior performance characteristics of this oxide for Flash memory applications, with excellent charge to breakdown and minimum change in the gate voltage during constant current stressing 相似文献
116.
K Sangthongpitag KR Moore NM Lapsys F Bao SR Babu PR Fain CF Verge 《Canadian Metallurgical Quarterly》1998,48(6):343-345
Abstract DNA typing of four tetrameric repeat loci (HUMVWA, HUMTH0I, D21SII and HPRT) was carried out in a Chinese Han population from Shanghai (East China) and one from Guangzhou (South-East China) using a quadruplex PCR amplification and detection of the fluorescent-labeled alleles on the ALF DNA sequencer. All loci were in accordance with Hardy-Weinberg equilibrium except for D21S11 in the Guangzhou population. A test for population differentiation showed no statistical difference in the allele frequency distribution between the two populations. Comparison of the allele frequency data with other Chinese Han populations from North and South-West China for the STR loci HUMVWA and HUMTH01 revealed heterogeneity between Northern Chinese Han and Southern Chinese Han, which is in accordance with previous studies on the basis of protein markers. 相似文献
117.
BR Babu SJ Zhu AV Ramayya JH Hamilton LK Peker MG Wang TN Ginter J Kormicki WC Ma JD Cole R Aryaeinejad K Butler-Moore YX Dardenne MW Drigert GM Ter-Akopian YT Oganessian JO Rasmussen S Asztalos IY Lee AO Macchiavelli SY Chu KE Gregorich MF Mohar S Prussin MA Stoyer RW Lougheed KJ Moody JF Wild 《Canadian Metallurgical Quarterly》1996,54(2):568-571
118.
119.
In this study, a simultaneous chemical kinetics and heat transfer model is used to predict the effects of the most important physical and thermal properties (thermal conductivity, heat transfer coefficient, emissivity, reactor temperature and heat of reaction number) of the feedstock on the convective-radiant pyrolysis of biomass fuels for different geometries such as slab, cylinder and sphere. The pyrolysis rate is simulated by a kinetic scheme involving two parallel primary reactions and a third secondary reaction between volatile and gaseous products and the char. Finite difference pure implicit scheme utilizing the Tri-Diagonal Matrix Algorithm (TDMA) is employed for solving heat transfer model equation. Runge-Kutta fourth order method is used for solving the chemical kinetics model equations. Simulations are carried out for different geometries considering the equivalent radius ranging from to , and the temperature ranging from to .For conversion in the thermally thick regime (intra-particle heat transfer control), it is found that variations in the properties mainly affect the activity of primary reactions. The highest sensitivity is associated with reactor temperature and emissivity. Applications of these findings in reactor design and operation are discussed. The results obtained using the model used in the present study are in excellent agreement with many reported experimental studies, much better than the agreement with earlier models reported in the literature. 相似文献
120.
P. Mohan Babu G. Venkata Rao P. Sreedhara Reddy S. Uthanna 《Journal of Materials Science: Materials in Electronics》2004,15(6):389-394
Cadmium oxide films were grown on glass substrates using d.c. reactive magnetron sputtering technique by sputtering from a metallic cadmium target in an oxygen partial pressure of 1×10–3 mbar under various substrate bias voltages. The substrate bias voltage significantly influences the crystallographic structure of the deposited films. The influence of substrate bias voltage on the electrical and optical properties of the films was systematically studied. The films formed at a substrate temperature of 473 K and bias voltage of –80 V showed an electrical resistivity of 1×10–3 cm, optical transmittance of 86%, optical band gap of 2.47 eV and a figure of merit of 7×10–3 –1. 相似文献