全文获取类型
收费全文 | 21499篇 |
免费 | 1580篇 |
国内免费 | 701篇 |
专业分类
电工技术 | 1037篇 |
技术理论 | 3篇 |
综合类 | 1305篇 |
化学工业 | 3791篇 |
金属工艺 | 1013篇 |
机械仪表 | 1279篇 |
建筑科学 | 1852篇 |
矿业工程 | 458篇 |
能源动力 | 562篇 |
轻工业 | 1474篇 |
水利工程 | 340篇 |
石油天然气 | 1093篇 |
武器工业 | 157篇 |
无线电 | 2250篇 |
一般工业技术 | 3089篇 |
冶金工业 | 1183篇 |
原子能技术 | 265篇 |
自动化技术 | 2629篇 |
出版年
2024年 | 78篇 |
2023年 | 297篇 |
2022年 | 469篇 |
2021年 | 624篇 |
2020年 | 521篇 |
2019年 | 462篇 |
2018年 | 482篇 |
2017年 | 617篇 |
2016年 | 560篇 |
2015年 | 737篇 |
2014年 | 877篇 |
2013年 | 1156篇 |
2012年 | 1229篇 |
2011年 | 1301篇 |
2010年 | 1092篇 |
2009年 | 1072篇 |
2008年 | 1141篇 |
2007年 | 1076篇 |
2006年 | 1177篇 |
2005年 | 1139篇 |
2004年 | 716篇 |
2003年 | 668篇 |
2002年 | 636篇 |
2001年 | 545篇 |
2000年 | 692篇 |
1999年 | 737篇 |
1998年 | 631篇 |
1997年 | 561篇 |
1996年 | 494篇 |
1995年 | 460篇 |
1994年 | 335篇 |
1993年 | 250篇 |
1992年 | 210篇 |
1991年 | 171篇 |
1990年 | 137篇 |
1989年 | 117篇 |
1988年 | 90篇 |
1987年 | 45篇 |
1986年 | 48篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
41.
Ma Chao Wan Minjie Xu Yunkai Ren Kan Qian Weixian Chen Qian Gu Guohua 《Applied Intelligence》2022,52(3):2785-2800
Applied Intelligence - Infrared target tracking plays an important role in both civil and military fields. The main challenges in designing a robust and high-precision tracker for infrared... 相似文献
42.
Xiaoshuai Li Zhengwei Yuan Xiaowei Wei Hui Li Guifeng Zhao Jiaoning Miao Di Wu Bo Liu Songying Cao Dong An Wei Ma Henan Zhang Weilin Wang Qiushi Wang Hui Gu 《Journal of materials science. Materials in medicine》2016,27(4):77
Spina bifida aperta are complex congenital malformations resulting from failure of fusion in the spinal neural tube during embryogenesis. Despite surgical repair of the defect, most patients who survive with spina bifida aperta have a multiple system handicap due to neuron deficiency of the defective spinal cord. Tissue engineering has emerged as a novel treatment for replacement of lost tissue. This study evaluated the prenatal surgical approach of transplanting a chitosan–gelatin scaffold seeded with bone marrow mesenchymal stem cells (BMSCs) in the healing the defective spinal cord of rat fetuses with retinoic acid induced spina bifida aperta. Scaffold characterisation revealed the porous structure, organic and amorphous content. This biomaterial promoted the adhesion, spreading and in vitro viability of the BMSCs. After transplantation of the scaffold combined with BMSCs, the defective region of spinal cord in rat fetuses with spina bifida aperta at E20 decreased obviously under stereomicroscopy, and the skin defect almost closed in many fetuses. The transplanted BMSCs in chitosan–gelatin scaffold survived, grew and expressed markers of neural stem cells and neurons in the defective spinal cord. In addition, the biomaterial presented high biocompatibility and slow biodegradation in vivo. In conclusion, prenatal transplantation of the scaffold combined with BMSCs could treat spinal cord defect in fetuses with spina bifida aperta by the regeneration of neurons and repairmen of defective region. 相似文献
43.
We report the experimental implementation of pseudo-nondiffracting beams by use of diffractive phase elements (DPE's). Based on the conjugate-gradient method presented in J. Opt. Soc. Am. A 15, 144-151 (1998), these DPE's are designed and fabricated on a flat quartz substrate. The experimental results show that the performance of the fabricated DPE's is in good agreement with the theoretical prediction. 相似文献
44.
We propose a method for designing a correlator for achieving rotation-invariant and controllable space-variant optical correlation. The design concept is based on a combination of fractional correlation and circular-harmonic decomposition of the reference object. The suggested method is described and analyzed in detail. Numerical simulations show that this new correlator might provide potential applications in practice. 相似文献
45.
46.
顾宪锋 《计算机与数字工程》2011,39(2):198-202
组播因其在点对多点传输方面拥有的优势,常被用于多媒体会议等应用。但是由于使用组播路由规模的限制,阻碍了在因特网推广组播技术的应用。首先对组播的原理作了分析,提出了具有组播特性的包含多个目的IP地址的IP传输设计,然后描述了一些关键问题,并讲解了具体设计和实现方法。 相似文献
47.
48.
Sang Min LeeAuthor VitaeJae Hwa SongAuthor Vitae Phill Gu JungAuthor VitaeDong Hyo JangAuthor Vitae Min Seong KimAuthor VitaeWeui Bong JeongAuthor Vitae Byung Min KimAuthor VitaeJong Soo KoAuthor Vitae 《Sensors and actuators. A, Physical》2011,171(2):233-240
A superhydrophobic micromesh covered with nanoprotrusions has been introduced and its applicability to a waterproof mobile phone speaker has been evaluated. The nanotextured superhydrophobic micromesh showed excellent water repellency, self-cleaning and waterproofing performances. In a waterproof speaker test using the fabricated nanotextured micromesh, the micromesh did not lose its waterproof function at 2 m water depth and did not form a remnant water film after being removed from the water. The packaged speaker showed almost the same sound quality before and after dipping at a 2 m water depth. These results demonstrate that the superhydrophobic nanotextured micromesh could be directly applicable for various products that need to resist water penetration, yet allow the transmission of gases and sound/light waves. 相似文献
49.
50.
Duan Li Xiaoling Sun Jianjun Gao Shenshen Gu Xiaojin ZhengAuthor vitae 《Automatica》2011,47(9):2094-2098
Reachability is one of the most important behavioral properties of Petri nets. We propose in this paper a novel approach for solving the fundamental equation in the reachability analysis of acyclic Petri nets, which has been known to be NP-complete. More specifically, by adopting a revised version of the cell enumeration method for an arrangement of hyperplanes in discrete geometry, we develop an efficient solution scheme to identify firing count vector solution(s) to the fundamental equation on a bounded integer set, with a complexity bound of O((nu)n−m), where n is the number of transitions, m is the number of places and u is the upper bound of the number of firings for all individual transitions. 相似文献