全文获取类型
收费全文 | 17983篇 |
免费 | 1571篇 |
国内免费 | 661篇 |
专业分类
电工技术 | 475篇 |
综合类 | 1409篇 |
化学工业 | 7964篇 |
金属工艺 | 760篇 |
机械仪表 | 544篇 |
建筑科学 | 1538篇 |
矿业工程 | 811篇 |
能源动力 | 546篇 |
轻工业 | 1246篇 |
水利工程 | 418篇 |
石油天然气 | 903篇 |
武器工业 | 31篇 |
无线电 | 441篇 |
一般工业技术 | 1248篇 |
冶金工业 | 1082篇 |
原子能技术 | 289篇 |
自动化技术 | 510篇 |
出版年
2024年 | 80篇 |
2023年 | 259篇 |
2022年 | 496篇 |
2021年 | 606篇 |
2020年 | 629篇 |
2019年 | 527篇 |
2018年 | 486篇 |
2017年 | 672篇 |
2016年 | 675篇 |
2015年 | 684篇 |
2014年 | 948篇 |
2013年 | 1090篇 |
2012年 | 1405篇 |
2011年 | 1365篇 |
2010年 | 1058篇 |
2009年 | 1040篇 |
2008年 | 841篇 |
2007年 | 1144篇 |
2006年 | 972篇 |
2005年 | 830篇 |
2004年 | 715篇 |
2003年 | 614篇 |
2002年 | 526篇 |
2001年 | 432篇 |
2000年 | 399篇 |
1999年 | 340篇 |
1998年 | 234篇 |
1997年 | 208篇 |
1996年 | 156篇 |
1995年 | 151篇 |
1994年 | 110篇 |
1993年 | 81篇 |
1992年 | 88篇 |
1991年 | 69篇 |
1990年 | 56篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 43篇 |
1986年 | 31篇 |
1985年 | 28篇 |
1984年 | 26篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
飞秒激光烧蚀研究进展 总被引:7,自引:3,他引:7
介绍飞秒激光烧蚀材料的机理论模型,阐述飞秒激光烧蚀的特性,揭示飞秒激光烧蚀的广泛应用前景。 相似文献
172.
173.
174.
Xiang-meng Jing Dong-ming Fang Chuang Huang Jing-quan Liu Xiang Chen 《Microelectronics Journal》2007,38(1):120-124
A novel method for fabrication of multi-layer microstructures of microelectro-mechanical system (MEMS) devices is described. This technique, which combines bulk silicon micromachining technique and UV-LIGA technique can overcome some shape limitations of single technique on complex microstructures. To demonstrate this combination, the SU-8 microstructure fabricated in the etched silicon grooves is presented. In this fabrication process, a SU-8 removal method by fuming sulfuric acid was introduced and a novel type of plastics PETG was tried in microhot embossing process. The proposed fabrication process can be applied to fabricating a high-aspect-ratio microstructure for a large displacement actuator and precision sensors. Moreover, this combined process enables the fabrication of more complex structures, which cannot be fabricated by bulk micromachining or UV-LIGA alone. 相似文献
175.
David C. Bassett Benedetto Marelli Showan N. Nazhat Jake E. Barralet 《Advanced functional materials》2012,22(16):3460-3469
Calcium carbonate is the most abundant biomineral that is biogenically formed with a vast array of nano and microscale features. Among the less stable polymorphs present in mineralized organisms, the most soluble, amorphous calcium carbonate (ACC), formed in chitin exoskeletons of some crustacea, is of particular interest since aqueous stability of isolated ACC is limited to a few hours in the absence of polyanions or magnesium. Here the influence of a selection of biopolymer gels on the mineralization of calcium carbonate is investigated. Mineralization is achieved in all biopolymers tested, but is particularly abundant in collagen hydrogels, in which a significant proportion of the calcium carbonate (≈18%) is found to be amorphous. In dense collagen gels, this amorphous fraction does not crystallize for up to six weeks in deionized water at room temperature. The reason why collagen in particular should stabilize this phase remains obscure, although the results suggest that the fiber diameter, fiber spacing, and the amphoteric nature of collagen fibers are important. Upon immersion in phosphate containing solutions, the calcium carbonate present within the collagen hydrogels is readily converted to carbonated hydroxyapatite, enabling the formation of a stiff bone‐like composite containing 78 wt% mineral, essentially equivalent to cortical bone. 相似文献
176.
由于PBGA组件点位于四件与PCB之间,焊点的检查和检修成本很高,控制PCB组件焊接失效显得尤为重要。文章通过对焊接失效的焊盘镍层、金层结构进行了SEM、X-RAY分析导致焊接失效产生的主要原因,并针对此现象进行控制与改善。 相似文献
177.
Noise detection and its removal is very important in the image processing. Detection of noise is very crucial and significant in random valued impulse noise because it does not hamper the image pixels uniformly. This paper presents a novel and unique concept of adaptive dual threshold for the detection of random valued impulse noise along with simple median filter at noise removal stage. Simulation results shows that an efficient noise detection leads to a superior quality of de-noised image as compared to existing adaptive threshold based image de-noising techniques. Proposed threshold computation is based on averaging of pixel values of window which enhances the PSNR of our system as compared to existing median filter based image de-noising methods. 相似文献
178.
The periodic structure of the underlying support of paintings on canvas can become quite prominent and disturbing in high resolution digital recordings. In this paper, we construct a new model and method for the digital removal of canvas which is considered as a noise component superimposed on the painting artwork. The high resolution of the images prohibits the efficient application of existing adaptive denoising filters. Hence, a two-step approach is proposed. First a (smoothing) Wiener filter is applied to the complete image. The second step consists of a spatially adaptive extension with low-complexity to obtain a generic digital canvas removal filter. 相似文献
179.
180.
Nanoporous thin films of Cd1−xCuxS (0≤x≤0.06) were grown on a heated glass substrate employing a home-made spray pyrolysis technique. The influences of [Cu]/[Cd] and the annealing in the range 300–500 °C on the structural and morphological properties of the films were investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM). The influences of Cu doping ratio, solution flow rate, and the deposition time on the optical properties and photocatalytic activity of these films are also reported. The films are of polycrystalline nature and hexagonal structure. Increasing the Cu doping ratio and annealing temperature improve the (1 0 1) preferential orientation. The crystallite size is ranged from 23.82 to 32.11 nm. XRD and FTIR reveal the formation of CdO in the 6% Cu-doped CdS film annealed at 400 °C and in all films annealed at 500 °C. The pure CdS film is of a porous structure and the close-packing and porosity of the films increase with increasing Cu%. Also, the pore diameter can be controlled from 50 to 15 nm with the increase of Cu content. The films showed transmittance below 70%. The optical band gap of the films is decreased from 2.43 to 1.82 eV with increasing Cu% and flow rate/deposition time. Additionally, the refractive indices and dispersion parameters of the films are also affected by the deposition conditions. Cu doping enhanced the films' photostability as well as the photocatalytic removal of methylene blue (MB). 相似文献