全文获取类型
收费全文 | 2075篇 |
免费 | 11篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 12篇 |
综合类 | 50篇 |
化学工业 | 396篇 |
金属工艺 | 307篇 |
机械仪表 | 473篇 |
建筑科学 | 161篇 |
矿业工程 | 23篇 |
能源动力 | 154篇 |
轻工业 | 61篇 |
水利工程 | 10篇 |
石油天然气 | 14篇 |
武器工业 | 7篇 |
无线电 | 58篇 |
一般工业技术 | 289篇 |
冶金工业 | 29篇 |
原子能技术 | 9篇 |
自动化技术 | 50篇 |
出版年
2023年 | 37篇 |
2022年 | 58篇 |
2021年 | 48篇 |
2020年 | 47篇 |
2019年 | 47篇 |
2018年 | 40篇 |
2017年 | 32篇 |
2016年 | 48篇 |
2015年 | 49篇 |
2014年 | 79篇 |
2013年 | 118篇 |
2012年 | 121篇 |
2011年 | 179篇 |
2010年 | 126篇 |
2009年 | 127篇 |
2008年 | 93篇 |
2007年 | 159篇 |
2006年 | 102篇 |
2005年 | 94篇 |
2004年 | 79篇 |
2003年 | 76篇 |
2002年 | 56篇 |
2001年 | 47篇 |
2000年 | 45篇 |
1999年 | 42篇 |
1998年 | 30篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有2103条查询结果,搜索用时 0 毫秒
1.
Y. Yin C.K. Erdonmez A. Cabot S. Hughes A.P. Alivisatos 《Advanced functional materials》2006,16(11):1389-1399
Formation of cobalt sulfide hollow nanocrystals through a mechanism similar to the Kirkendall Effect has been investigated in detail. It is found that performing the reaction at > 120 °C leads to fast formation of a single void inside each shell, whereas at room temperature multiple voids are formed within each shell, which can be attributed to strongly temperature‐dependent diffusivities for vacancies. The void formation process is dominated by outward diffusion of cobalt cations; still, the occurrence of significant inward transport of sulfur anions can be inferred as the final voids are smaller in diameter than the original cobalt nanocrystals. Comparison of volume distributions for initial and final nanostructures indicates excess apparent volume in shells, implying significant porosity and/or a defective structure. Indirect evidence for fracture of shells during growth at lower temperatures was observed in shell‐size statistics and transmission electron microscopy images of as‐grown shells. An idealized model of the diffusional process imposes two minimal requirements on material parameters for shell growth to be obtainable within a specific synthetic system. 相似文献
2.
Fabrication of multi-walled carbon nanotube reinforced polyelectrolyte hollow nanofibers by electrospinning 总被引:1,自引:0,他引:1
Hybrid hollow multi-walled carbon nanotubes (MWCNTs)/polyelectrolytes (PE) nanofibers were prepared by a combination of the electrospinning method and layer-by-layer (LbL) technique. The mixed polystyrene (PS)/MWCNTs nanofibers were obtained by electrospinning method, which were employed as templates to self-assembly multilayered polyelectrolytes by LbL technique. Hollow MWCNTs/PE nanofibers were obtained by selectively removed part of the template: PS, which is confirmed by Raman spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). 相似文献
3.
Preparation of submicrometer-sized titania hollow spheres by templating sulfonated polystyrene latex particles 总被引:1,自引:0,他引:1
Akhmad Syoufian 《Materials Letters》2007,61(7):1572-1575
Submicrometer-sized titania hollow spheres with tunable shell thickness and smooth surfaces have been successfully synthesized by employing sulfonated polystyrene (PS) latex particles as a template in sol-gel method. The structure of the particles was characterized by scanning electron microscopy and transmission electron microscopy. The shell thickness was readily tuned by altering the concentration of titanium tetrabutoxide (TBOT) in ethanol solutions. The surface roughness as well as the shell thickness has the tendency to increase with the increase in the concentration of TBOT. The diameter of the hollow spheres was on the average of 20-26% smaller than the diameter of template PS latex particles. Some titania fragments were also observed for the sample with the highest TBOT concentration. 相似文献
4.
Wei-Jun Liu Wei-Dong He Xue-Wu Ge Hua-Rong Liu Mo-Zheng Wang Zheng-Qi Chang 《Materials Letters》2007,61(13):2818-2821
Interfacial-initiated polymerization of styrene (St) was carried out in inversed emulsion with cumene hydroperoxide (CHPO) and ferrous sulfate (FeSO4)/disodium ethylenediaminetetraacetate (NaEDTA)/sodium formaldehyde sulfoxylate (SFS) as the redox initiation system. The water-soluble Fe2+-NaEDTA-SFS acted as the reducing component and the oil-soluble CHPO as the oxidant component of the redox initiation system. Therefore, the primary radicals were produced mainly at the oil/water interface to initiate the polymerization of St. Thus, sub-micrometer hollow polystyrene (PSt) spheres were obtained by one-stage polymerization, which was supported by the techniques of transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). 相似文献
5.
We have studied the CO2/CH4 mixed gas permeation through hollow fiber membranes in a permeator. An approach to characterize the true separation performance of hollow fiber membranes for binary gas mixtures was provided based on experiments and simulations. Experiments were carried out to measure the retentate and permeate flow rates and compositions at each outlet. The influences of pressure drop within the hollow fibers, non-ideal gas behavior in the mixture and concentration polarization were taken into consideration in the mathematics model. The calculation results indicate that the net influence of the non-ideal gas behavior, competitive sorption and plasticization yields the calculated CO2 permeance in a mixed gas permeator close to that obtained in pure gas tests. Whereas the CH4 permeance is higher in the mixed gas tests than that in the pure gas tests, as the plasticization caused by CO2 dominates the permeation process. As a result, the CO2/CH4 mixed gas selectivity is smaller than those obtained in pure gas tests at equivalent pressures.The calculated membrane performance shows little changes with stage cut if the effect of concentration polarization is accounted for in the calculation. The integration method developed in this study could provide more accurate characterizations of mixed gas permeance of hollow membranes than other estimation methods, as our model considers the roles of non-ideal gas behavior and concentration polarization properly. 相似文献
6.
Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder 总被引:1,自引:0,他引:1
By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented. 相似文献
7.
通过改变高速车削淬火钢(Cr12)的切削用量,对切削力、切削温度、加工表面质量等进行了研究,结果表明合理选择切削用量,高速硬车削淬火钢可显著提高生产率及加工表面质量,并在一定程度上可取代磨削加工。 相似文献
8.
“Lightweight” is a major trend in machine tool design to ensure higher speed and higher acceleration of elements, which results from state‐of‐the‐art technology, such as the new linear drive and the control system.[1] Research is being carried out in institutes worldwide into lightweight construction by either design and/or choice of material. One type of advanced lightweight engineering material to reduce the mass of the moving parts of machine tools is hollow‐sphere composites. Investigations of their thermal and mechanical properties show the superior quality of HSCs compared with alternative materials. Example applications of hollow‐sphere composites include the table of a milling machine and robot arms. 相似文献
9.
主轴回转误差对加工影响的数学描述 总被引:2,自引:0,他引:2
就车床、镗床类机床主轴纯径向跳动和终了角度摆动所产生的加工误差进行了单因素分析,并给出了较为精确的数学表达。 相似文献
10.
The development of a high-speed spindle measurement system using a laser diode and a quadrants sensor 总被引:2,自引:2,他引:2
Wen-Yuh Jywe Chun-Jen Chen 《International Journal of Machine Tools and Manufacture》2005,45(10):1162-1170
Reducing the manufacturing time is the trend of precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. High-speed cutting is becoming more widely used and the high-speed spindle is a very important element, whose precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and the effects of the spindle's thermal expansion; however, the measurement of the high-speed spindle continues to use the conventional spindle measurement method.As with the measurement of the high-speed spindle, more strict demands are set on the dynamic balance of cutting tools and the bandwidth of the measurement systems when compared with common spindles. The capacitance displacement sensor has been employed for the spindle error test. The precision of the measurement system is limited by the reference (such as a master ball or a master cylinder). Also the capacitance sensor and the reference must be grounded together. This paper presents a simple spindle measurement system using a laser diode and a quadrants sensor, with accuracy up to 1 μm, within 300,000 rpm for various spindles. The system does not need any reference and it is easy to set up. This system can be applied to measure the spindle errors, the spindle speed and the spindle indexing. 相似文献