全文获取类型
收费全文 | 237983篇 |
免费 | 15835篇 |
国内免费 | 8517篇 |
专业分类
电工技术 | 11555篇 |
技术理论 | 9篇 |
综合类 | 13473篇 |
化学工业 | 35850篇 |
金属工艺 | 14022篇 |
机械仪表 | 13259篇 |
建筑科学 | 15835篇 |
矿业工程 | 5515篇 |
能源动力 | 5526篇 |
轻工业 | 13879篇 |
水利工程 | 4537篇 |
石油天然气 | 8718篇 |
武器工业 | 1582篇 |
无线电 | 27061篇 |
一般工业技术 | 32977篇 |
冶金工业 | 9414篇 |
原子能技术 | 2282篇 |
自动化技术 | 46841篇 |
出版年
2024年 | 531篇 |
2023年 | 2627篇 |
2022年 | 4698篇 |
2021年 | 6997篇 |
2020年 | 5410篇 |
2019年 | 4218篇 |
2018年 | 18634篇 |
2017年 | 18257篇 |
2016年 | 14273篇 |
2015年 | 7383篇 |
2014年 | 8790篇 |
2013年 | 10353篇 |
2012年 | 14788篇 |
2011年 | 21436篇 |
2010年 | 18781篇 |
2009年 | 15582篇 |
2008年 | 16329篇 |
2007年 | 16638篇 |
2006年 | 8744篇 |
2005年 | 8526篇 |
2004年 | 5946篇 |
2003年 | 4918篇 |
2002年 | 3981篇 |
2001年 | 2979篇 |
2000年 | 3218篇 |
1999年 | 3378篇 |
1998年 | 2621篇 |
1997年 | 2131篇 |
1996年 | 2158篇 |
1995年 | 1739篇 |
1994年 | 1418篇 |
1993年 | 993篇 |
1992年 | 802篇 |
1991年 | 655篇 |
1990年 | 450篇 |
1989年 | 371篇 |
1988年 | 317篇 |
1987年 | 203篇 |
1986年 | 128篇 |
1985年 | 88篇 |
1984年 | 58篇 |
1982年 | 50篇 |
1981年 | 39篇 |
1980年 | 42篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 46篇 |
1959年 | 49篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
本文分析了乌兰矿投产前期采矿现状及存在的主要问题,针对该矿所处蒙古国经济落后、投资风险大的现实状况,为避免生产中断、规避投资风险,早日回收前期投资考虑,采取了双斜坡道开拓、全尾胶结充填、高端壁空场嗣后充填采矿、多中段组合式连续开采等系列技术应对方案。大大降低了一次性投资规模及投资风险,前期投资得以快速回笼的同时,矿山产能也充分释放,确保了矿山的持续稳定,取得了较好的经济和社会效益。为海外地下近地表矿体开采矿山规避投资风险提供了很好的技术方案借鉴。 相似文献
32.
Sijia Huo Yujin Wang Mianyi Yao Zhikun Zhang Lei Chen Hui Gu Jiahu Ouyang Yu Zhou 《Journal of the European Ceramic Society》2021,41(11):5466-5473
Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB2 addition as a sintering aid for the first time. The effects of ZrB2 contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB2 and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB2 (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports. 相似文献
33.
One-Dimensional Deep Convolutional Neural Network for Mineral Classification from Raman Spectroscopy
Neural Processing Letters - Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials.... 相似文献
34.
Wenjie Liu Jianmin Liu Shu Xing Xiaobin Li Liwen Han Kechun Liu Tao Wei Mingyang Zhou 《European Journal of Lipid Science and Technology》2021,123(6):2000276
In this study, the anti-atherosclerotic properties of three marine phospholipids (MPLs) extracts from fishery by-products including codfish roe, squid gonad, and shrimp head are verified. Their effects on key factors involved in atherosclerosis are examined and compared to explore whether the differences in their constitutions lead to the differences in the function. All three MPLs dampen oxidation of low- density lipoproteins (LDL) in vitro. Treating RAW264.7 macrophages and HUVECs endothelial cells with each MPLs ranging 10–100 µg mL−1 does not decrease cell viability, yet ox-LDL caused cytotoxicity of both cells are alleviated by 50 or 100 µg mL−1 MPLs treatment. In addition, the three MPLs reduce ox-LDL induced macrophage foam-like transition, mainly through inhibition of lipid uptake. Of the three MPLs, the one from squid gonad exhibits the best effect. On the other hand, all three MPLs modulate inflammatory responses, equally, by inhibiting the adhesion of monocytes to endothelial cells, and decreasing secretion of pro-inflammatory cytokines IL-6 and MCP-1. Using a high-cholesterol diet induced zebrafish model, it is found that all three MPLs, especially the one from squid gonad, alleviates cholesterol accumulation in early plaques, and decreases total cholesterol as well as lipid peroxide in vivo. Practical Applications: As a way of making the best of the increasingly scarce marine resources, valuable lipid components can be recovered from by-products and wastes from the fishery industry. Here, we tested the anti-atherosclerotic effects and the mechanisms of three MPLs extracted from codfish roe, squid gonad, and shrimp head. Our study provides further evidence that marine phospholipids extracted from fishery by-products could protect against atherosclerosis, and helps to elucidate the structure-function relationship of MPLs. 相似文献
35.
为了解破碎围岩分别采用锚杆支护、锚喷支护以及锚喷+锚索耦合三种支护方式下的支护效果,进而为破碎围岩巷道选择合理的支护方式提供参考。通过借助FLAC3D软件建立数值模型,分析不同支护条件下的破碎围岩巷道位移量、应力分布以及塑性区的时空演化特征。结果表明,采用锚喷+锚索耦合支护时,可以较好的控制巷道围岩的位移量、减小应力集中效应、缩小塑性区的影响范围。 相似文献
36.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
37.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
38.
Mitigating gibbsite particle cracking and breakage during industrial alumina production can increase the quality of smelter grade alumina product by reducing the ultrafine particle content. Therefore, it is essential to investigate the particle cracking during static calcination and the breakage of calcined gibbsite particles under external force. In this work, we investigated the impact of the calcination ramping rate and the crystallite size on gibbsite particle cracking during static calcination. A slow ramping rate and a large pristine crystallite size tend to increase particle cracking. Apart from the study of particle cracking behaviour, we also investigated the breakage of calcined gibbsite particle under external force. Cracks on the particle surface can initiate breakage within the crystallite and along the grain boundary under external force. The breakage within crystallite occurs as the cleavage of the crystallite, while the breakage along the grain boundary leads to the shedding of a whole crystallite. We further explored the factors influencing the strength of calcined gibbsite particles. With increasing calcination temperature, the strength of particle increases when gibbsite converts to boehmite, and then decreases when boehmite converts into amorphous alumina. Particles containing smaller crystallites and calcined with fast ramping rates exhibit higher resistance to breakage. 相似文献
39.
Wireless Networks - TCP latency is critical to the performance of Web services. However, packet loss greatly impairs the TCP performance due to its poor loss recovery mechanisms. Recent work FUSO... 相似文献
40.