全文获取类型
收费全文 | 2736篇 |
免费 | 40篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 28篇 |
综合类 | 2篇 |
化学工业 | 279篇 |
金属工艺 | 30篇 |
机械仪表 | 42篇 |
建筑科学 | 68篇 |
矿业工程 | 7篇 |
能源动力 | 29篇 |
轻工业 | 153篇 |
水利工程 | 9篇 |
无线电 | 258篇 |
一般工业技术 | 285篇 |
冶金工业 | 1403篇 |
原子能技术 | 20篇 |
自动化技术 | 164篇 |
出版年
2023年 | 16篇 |
2022年 | 18篇 |
2021年 | 31篇 |
2020年 | 17篇 |
2019年 | 20篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 33篇 |
2015年 | 36篇 |
2014年 | 32篇 |
2013年 | 69篇 |
2012年 | 58篇 |
2011年 | 71篇 |
2010年 | 64篇 |
2009年 | 58篇 |
2008年 | 65篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 57篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 40篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 68篇 |
1998年 | 391篇 |
1997年 | 225篇 |
1996年 | 170篇 |
1995年 | 96篇 |
1994年 | 85篇 |
1993年 | 93篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 41篇 |
1989年 | 49篇 |
1988年 | 36篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 22篇 |
1977年 | 42篇 |
1976年 | 98篇 |
1971年 | 19篇 |
1970年 | 14篇 |
排序方式: 共有2777条查询结果,搜索用时 15 毫秒
91.
M. R. Mohd Asyraf M. Masud Rana Harrison D. E. Fan Andrew T. Koch Alireza Nojeh 《Fullerenes, Nanotubes and Carbon Nanostructures》2016,24(2):88-99
Vertically aligned carbon nanotubes (VACNTs) have drawn significant attention by the researchers because of their nanometric size and favorable material properties. Patterning of CNT forests in the micrometric domain is very important for their application in the area of microelectromechanical system (MEMS). For the first time this paper reports, detailed experimental investigation on a post growth μ-patterning process of VACNT forests. The micromechanical bending (M2B) process was locally applied at the targeted area in order to change the alignment of VACNT forests. Interestingly, the VACNT forest was transformed from typical black body absorber to reflective mirror as the M2B process was applied. Several parameters were identified that govern the resultant patterns such as rotational spindle speed, lateral bending speed, step size, tool morphology, and total depth of bend. Optimization of the parameters was carried out experimentally to obtain the best surface roughness and integrity of the microstructure. A minimum average surface roughness of Ra = 15 nm was achieved with 2000 rpm spindle speed, 1 mm/min bending speed and 1 µm step size. 相似文献
92.
Gary G. Koch 《技术计量学》2013,55(4):577-585
A general procedure for estimating the population mean in random effects models of the nested and/of classification type is considered. The suggested estimator is unbiased and consistent (with respect to the structure of the experimental design). It is also optimal with respect to a particular quadratic, location-sensitive criterion. Finally, for experimental designs which contain a certain degree of structural balance, the suggested estimator coincides with the sample mean. 相似文献
93.
94.
95.
Kerim Isik Gregory Gerstein Thomas Schneider Robert Schulte Daniel Rosenbusch Till Clausmeyer Florian Nürnberger Milan Vucetic Sergej Koch Sven Hübner Bernd-Arno Behrens A. Erman Tekkaya Marion Merklein 《Production Engineering》2016,10(1):5-15
Sheet-bulk metal forming processes combine conventional sheet forming processes with bulk forming of sheet semi-finished parts. In these processes the sheets undergo complex forming histories. Due to in- and out-of-plane material flow and large accumulated plastic strains, the conventional failure prediction methods for sheet metal forming such as forming limit curve fall short. As a remedy, damage models can be applied to model damage evolution during those processes. In this study, damage evolution during the production of two different toothed components from DC04 steel is investigated. In both setups, a deep drawn cup is upset to form a circumferential gearing. However, the two final products have different dimensions and forming histories. Due to combined deep drawing and upsetting processes, the material flow on the cup walls is three-dimensional and non-proportional. In this study, the numerical and experimental investigations for those parts are presented and compared. Damage evolution in the process chains is simulated with a Lemaitre damage criterion. Microstructural analysis by scanning electron microscopy is performed in the regions with high mechanical loading. It is observed that the evolution of voids in terms of void volume fraction is strongly dependent on the deformation path. The comparison of simulation results with microstructural data shows that the void volume fraction decreases in the upsetting stage after an initial increase in the drawing stage. Moreover, the concurrent numerical and microstructural analysis provides evidence that the void volume fraction decreases during compression in sheet-bulk metal forming. 相似文献
96.
Hongqi Li Amit Misra Yuntian Zhu Zenji Horita Carl C. Koch Terry G. Holesinger 《Materials Science and Engineering: A》2009,523(1-2):60-64
Carbon nanotube (CNT) reinforced nanostructured Cu matrix composite with a grain size less than 25 nm has been successfully fabricated via a combination of ball milling and high-pressure torsion. CNTs were found to be homogeneously dispersed into the metal matrix, leading to grain refinement with a narrow grain size distribution and significant increase in hardness. 相似文献
97.
98.
The Effect of Gradual Fluorination on the Properties of FnZnPc Thin Films and FnZnPc/C60 Bilayer Photovoltaic Cells
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)
Michael Brendel Stefan Krause Andreas Steindamm Anna Katharina Topczak Sudhakar Sundarraj Peter Erk Steffen Höhla Norbert Fruehauf Norbert Koch Jens Pflaum 《Advanced functional materials》2015,25(10):1565-1573
Motivated by the possibility of modifying energy levels of a molecule without substantially changing its band gap, the impact of gradual fluorination on the optical and structural properties of zinc phthalocyanine (FnZnPc) thin films and the electronic characteristics of FnZnPc/C60 (n = 0, 4, 8, 16) bilayer cells is investigated. UV–vis measurements reveal similar Q‐ and B‐band absorption of FnZnPc thin films with n = 0, 4, 8, whereas for F16ZnPc a different absorption pattern is detected. A correlation between structure and electronic transport is deduced. For F4ZnPc/C60 cells, the enhanced long range order supports fill factors of 55% and an increase of the short circuit current density by 18%, compared to ZnPc/C60. As a parameter being sensitive to the organic/organic interface energetics, the open circuit voltage is analyzed. An enhancement of this quantity by 27% and 50% is detected for F4ZnPc‐ and F8ZnPc‐based devices, respectively, and is attributed to an increase of the quasi‐Fermi level splitting at the donor/acceptor interface. In contrast, for F16ZnPc/C60 a decrease of the open circuit voltage is observed. Complementary photoelectron spectroscopy, external quantum efficiency, and photoluminescence measurements reveal a different working principle, which is ascribed to the particular energy level alignment at the interface of the photoactive materials. 相似文献
99.
100.
Tobias Schneider Lars Wietschel Denny Schüppel Jonas Riesner Kevin Konrad Andrea Thorenz Axel Tuma Dietmar Koch 《International Journal of Applied Ceramic Technology》2022,19(6):3247-3254
Over the past 40 years, development of Ceramic Matrix Composites (CMCs) has focused mainly on the improvement of material performance and optimization of cost-efficient production routes. Recently, more fields of application have opened up for CMCs, in which environmental impacts are relevant. These impacts have barely been investigated so far but receive growing interest due to increasing awareness of the environmental consequences. Our innovative approach frames material properties in relation to environmental impacts (e.g., global warming potential in CO2 emission) by varying process parameters to balance optimum performance against environmental considerations. First, the process of wet filament winding has been investigated up to the Carbon Fiber Reinforced Plastic (CFRP) state by changing both the curing and tempering temperatures. During the production of CFRP plates, mass and energy flows were tracked in each step. Three point-bending and interlaminar shear tests have been performed on the resulting samples to identify basic mechanical properties. The environmental impacts are determined by a cradle-to-gate Life Cycle Assessment (LCA), using the software SimaPro. The resulting tradeoffs between mechanical properties and environmental impacts show nonlinear behavior, thus revealing optimum points above which improved mechanical properties are associated with significantly higher CO2 emissions. 相似文献