全文获取类型
收费全文 | 21837篇 |
免费 | 2036篇 |
国内免费 | 911篇 |
专业分类
电工技术 | 1183篇 |
综合类 | 1021篇 |
化学工业 | 3569篇 |
金属工艺 | 1453篇 |
机械仪表 | 1641篇 |
建筑科学 | 1257篇 |
矿业工程 | 596篇 |
能源动力 | 813篇 |
轻工业 | 1496篇 |
水利工程 | 309篇 |
石油天然气 | 952篇 |
武器工业 | 115篇 |
无线电 | 2940篇 |
一般工业技术 | 3557篇 |
冶金工业 | 1216篇 |
原子能技术 | 184篇 |
自动化技术 | 2482篇 |
出版年
2024年 | 66篇 |
2023年 | 422篇 |
2022年 | 613篇 |
2021年 | 1065篇 |
2020年 | 810篇 |
2019年 | 659篇 |
2018年 | 809篇 |
2017年 | 766篇 |
2016年 | 792篇 |
2015年 | 905篇 |
2014年 | 1101篇 |
2013年 | 1340篇 |
2012年 | 1447篇 |
2011年 | 1607篇 |
2010年 | 1378篇 |
2009年 | 1353篇 |
2008年 | 1224篇 |
2007年 | 1015篇 |
2006年 | 974篇 |
2005年 | 850篇 |
2004年 | 651篇 |
2003年 | 635篇 |
2002年 | 590篇 |
2001年 | 498篇 |
2000年 | 465篇 |
1999年 | 471篇 |
1998年 | 455篇 |
1997年 | 353篇 |
1996年 | 326篇 |
1995年 | 258篇 |
1994年 | 208篇 |
1993年 | 136篇 |
1992年 | 109篇 |
1991年 | 75篇 |
1990年 | 74篇 |
1989年 | 62篇 |
1988年 | 41篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 22篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1973年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Jinsun Yoon Hong-kyu Song Sungjin Park Jongok Won Yong Soo Kang 《Polymer Bulletin》2014,71(8):2053-2065
We have investigated the effects of localized surface plasmons (LSPs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs). Ag and Au nanoparticles (NPs) were prepared by photoreduction in the presence of generation 5 polyester hydroxyl acetylene bis(hydroxymethyl)propanoic acid dendrons (Dendron) as a stabilizer. The plasmon-enhanced DSSCs were achieved by incorporating metal@Dendron NPs into TiO2 photoanodes. The presence of dendrons prevents the photoelectrons from recombining on the surface of TiO2 semiconductor and improves the stability of metal NPs. With the addition of Ag@Dendron NPs, the photocurrent and the power conversion efficiency of quasi-solid-state DSSCs increased due to the LSP effect of metal NPs and the barrier effect of dendron, which were confirmed by the increased incident photon-to-photocurrent efficiency and by electrochemical impedance spectroscopy analysis. 相似文献
992.
Park Ji-Woo Ku Tae-Wan Kim Jeong Kim Kwang-Ho Kang Beom-Soo 《Journal of Mechanical Science and Technology》2016,30(5):2203-2210
Journal of Mechanical Science and Technology - Flexible forming technology such as Multi-point dieless forming (MDF) has benefits for the sheet metal field because it can implement a variety of... 相似文献
993.
随着我国交通事业的发展,其对桥梁的结构和性能也提出了更高的要求。本文主要分析了大跨高墩连续刚构桥不对称悬臂段施工现状和主要施工技术要点,并成功将其应用于实际,以期为同类桥型的施工提供借鉴。 相似文献
994.
995.
Roll-to-roll (R2R) slot-die coating systems are mostly devoted to the mass manufacture of printed electronics. This study examined the correlation among the operating conditions, thickness, and width of the patterned strip fabricated by the R2R slot-die system. A full factorial experiment was conducted to screen for effective parameters. The velocity of a moving substrate was found to be the most dominant parameter affecting the thickness and width of the patterned strips. The flow ratio of the supply to the slot-die, and gap between substrate and slot-die did not affect the width of the strip, but affected the thickness; therefore, the flow ratio and gap can be employed for the independent patterning of thickness against width. In addition, it was proposed to determine the R2R process conditions, such as gap, velocity, and flow ratio for the desired thickness and width of the patterned strips. 相似文献
996.
Dimensional variation in assembly processes is one of the most important issues that affect quality. Although robust design and statistical process quality control help to reduce this problem, they cannot be used for instant variation reduction during assembly operations, especially during process ramp-up. This paper introduces a complete methodology for dimensional-related error compensation in compliant sheet metal assembly processes. The proposed methodology is divided into two steps: (1) an off-line error control-learning module using virtual assembly models to determine necessary adjustments; and (2) an in-line control implementation using a feed-forward control strategy based on the learned adjustments. The off-line learning step focuses on determining control actions or corrections to compensate for the negative effects incoming part errors have on Key Product Characteristics. Specifically, it utilizes a newly developed iterative sampling method based on Kriging fitting to efficiently determine optimal control actions. The in-line feed-forward control identifies appropriate part-by-part adjustments using these learned control actions and incoming assembly component measurements. In this paper, two case studies are presented. First, a mathematical case study presents an empirical proof for the feasibility of the Iterative Sampling and Fitting Algorithm. Second, a simulation-based case study illustrates the effectiveness of the proposed methodology to improve dimensional quality in assembly operations for compliant sheet metal parts. 相似文献
997.
Malrey Lee Eun-Kwan Kang 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(3):419-425
Path design uses information about termite reproduction and the termite environment necessary for tunneling. Features are
extracted by analyzing relevance of this information, and the fitness and relevance of these features are evaluated. The proposed
method is demonstrated and is capable of finding various optimal termite tunneling paths. 相似文献
998.
J. Wang C. Hong A. H. Kang C. H. Geng 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(2):214-226
Drilling and dewaxing are used to manufacture the quantitative model and stochastic model of fracture-vuggy media, respectively, which are used for the investigation on the oil displacement of full diameter cores. The formation and distribution of remaining oil and sensitivity analysis in fracture-vuggy media are studied. The research results show that the density difference between the displacing phase and the displaced phase and the connection position between fractures and vugs determine the fluid distribution law in the vugs. After water flooding, the remaining oil is composed of “attic oil,” “occlusion oil,” “corner oil,” “blind-vug oil,” “oil film,” and “dead oil region.” Then, the influences of oil viscosity, injection rate, density, and viscosity of driving fluid on oil recovery and remaining oil are studied. 相似文献
999.
Molecular Ordering: Selectivity of Threefold Symmetry in Epitaxial Alignment of Liquid Crystal Molecules on Macroscale Single‐Crystal Graphene (Adv. Mater. 40/2018) 下载免费PDF全文
1000.
Wenjun Hou Chuanhui Liu Faping Lu Jiafang Kang Zhongyang Mao Bifeng Li 《Photonic Network Communications》2018,35(2):251-257
A novel non-line-of-sight ultraviolet single-scatter path loss model for coplanar geometries is proposed on the basis of spherical coordinate system. In comparison with the classical single-scatter analytical model based on the prolate-spheroidal coordinate system, it is of a simple integral form which only depends on the variables of the zenith and receiver elevation angles. Additionally, analytical approximation for the proposed single-scatter path loss model is presented. Numerical examples on path loss are presented for various system geometries. Correspondingly, the results are verified with the classical single-scatter analytical model, which demonstrates the validity of our path loss model and the reasonability of the analytical approximation. 相似文献