全文获取类型
收费全文 | 14350篇 |
免费 | 1359篇 |
国内免费 | 737篇 |
专业分类
电工技术 | 508篇 |
综合类 | 1989篇 |
化学工业 | 601篇 |
金属工艺 | 629篇 |
机械仪表 | 857篇 |
建筑科学 | 5199篇 |
矿业工程 | 332篇 |
能源动力 | 169篇 |
轻工业 | 431篇 |
水利工程 | 201篇 |
石油天然气 | 154篇 |
武器工业 | 108篇 |
无线电 | 1340篇 |
一般工业技术 | 1219篇 |
冶金工业 | 300篇 |
原子能技术 | 139篇 |
自动化技术 | 2270篇 |
出版年
2024年 | 40篇 |
2023年 | 151篇 |
2022年 | 266篇 |
2021年 | 329篇 |
2020年 | 382篇 |
2019年 | 277篇 |
2018年 | 262篇 |
2017年 | 360篇 |
2016年 | 424篇 |
2015年 | 458篇 |
2014年 | 957篇 |
2013年 | 839篇 |
2012年 | 1121篇 |
2011年 | 1279篇 |
2010年 | 949篇 |
2009年 | 1008篇 |
2008年 | 898篇 |
2007年 | 1039篇 |
2006年 | 875篇 |
2005年 | 771篇 |
2004年 | 615篇 |
2003年 | 536篇 |
2002年 | 471篇 |
2001年 | 404篇 |
2000年 | 344篇 |
1999年 | 267篇 |
1998年 | 211篇 |
1997年 | 159篇 |
1996年 | 135篇 |
1995年 | 104篇 |
1994年 | 107篇 |
1993年 | 71篇 |
1992年 | 55篇 |
1991年 | 54篇 |
1990年 | 51篇 |
1989年 | 35篇 |
1988年 | 38篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 14篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
盘扣式支撑架具有承载力强、方便安全、结实耐用等优点,被广泛应用于地铁施工。本文以广州市轨道交通十八号线万顷沙车辆段为例,对承插型盘扣式支撑架在地铁车辆段工程中的具体应用进行了详细说明,以期为同类工程提供参考。 相似文献
2.
Mehdi Hosseini Abadshapoori 《亚洲传热研究》2021,50(2):1056-1072
Increasing the heat capacity of heat exchangers is a crucial need for modern devices. The thermal conductivity of the usual fluids and the Nusselt (Nu) number of flows containing such fluids are two bottlenecks in the way of increasing heat delivery in the heat exchangers. For this reason, nanofluids have been introduced. The effect of utilizing a Cu-water nanofluid as a coolant of two hot pipes in a square cavity is investigated numerically with a two-component lattice Boltzmann method. The volume fraction of nanoparticles is assumed to be constant (0.03) while the Richardson (Ri) number varies from 0.02 to 20. Results show that the effectiveness of nanoparticles is better observed in the natural convection mode. However, sedimentation is also very probable at high Ri numbers, which significantly reduces the effectiveness of the nanoparticles. Configurations which produce a natural convection stream similar to the forced convection one as well as the configurations with high spacing and hence, low heat stream interactions, are the best choices for a uniform heat rate from the pipes. 相似文献
3.
4.
5.
As the development of cloud computing and the convenience of wireless sensor netowrks, smart devices are widely used in daily life, but the security issues of the smart devices have not been well resolved. In this paper, we present a new NTRU-type public-key cryptosystem over the binary field. Specifically, the security of our scheme relies on the computational intractability of an unbalanced sparse polynomial ratio problem (DUSPR). Through theoretical analysis, we prove the correctness of our proposed cryptosystem. Furthermore, we implement our scheme using the NTL library, and conduct a group of experiments to evaluate the capabilities and consuming time of encryption and decryption. Our experiments result demonstrates that the NTRU-type public-key cryptosystem over the binary field is relatively practical and effective. 相似文献
6.
7.
无源光网络(Passive Optical Network,PON)作为当今接入网的主要技术解决方案,具有带宽使用效率高、传输距离远、抗干扰能力强等特点.通过研究PON技术的发展动态,本文首先归纳了各种PON技术的产生背景和应用特点,整理出各技术间的连接关系及主要标准;其次介绍了PON技术的帧结构,并对带宽、波长、传输模式等PON技术的主要参数进行了汇总;然后将国内外研究热点进行划分,围绕媒体访问控制协议、帧结构、动态带宽分配算法、节能机制等关键技术,阐述了其研究现状及在PON中的重要作用;最后对PON技术的发展趋势进行了展望. 相似文献
8.
Avtar Singh Soottawat Benjakul Nurul Huda 《International Journal of Food Science & Technology》2020,55(12):3553-3562
Effect of debittered salmon frame hydrolysate (DSFH) at various levels (0, 5, 10, 15, 20 and 25 g/100 g) on physicochemical, textural, sensory and nutritional properties of biscuits was investigated. The highest thickness was obtained for the sample with 25 g/100 g DSFH (P < 0.05). There was no difference in diameter among all the biscuit samples (P > 0.05). The samples added with DSFH had lower weight, water activity and moisture content than the control (CONT, without DSFH) (P < 0.05). DSFH at 15 g/100 g showed no detrimental effect on sensory properties of resulting biscuits (DSFH-15). The DSFH-15 biscuit showed reduction in cutting force and fracturability. Scanning electron microscopic and cross-sectional images showed that DSFH-15 biscuit had more porous structure, compared to the CONT. The biscuits fortified with 15 g/100 g DSFH had higher protein but had lower energy value, fat and carbohydrate content than the CONT. 相似文献
9.
Kruk Menno R.; Halász József; Meelis Wout; Haller József 《Canadian Metallurgical Quarterly》2004,118(5):1062
Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.