全文获取类型
收费全文 | 324024篇 |
免费 | 17631篇 |
国内免费 | 5763篇 |
专业分类
电工技术 | 14031篇 |
技术理论 | 35篇 |
综合类 | 16206篇 |
化学工业 | 50761篇 |
金属工艺 | 18536篇 |
机械仪表 | 18189篇 |
建筑科学 | 19782篇 |
矿业工程 | 8139篇 |
能源动力 | 8043篇 |
轻工业 | 17599篇 |
水利工程 | 4872篇 |
石油天然气 | 17168篇 |
武器工业 | 1642篇 |
无线电 | 35859篇 |
一般工业技术 | 44899篇 |
冶金工业 | 15453篇 |
原子能技术 | 2941篇 |
自动化技术 | 53263篇 |
出版年
2025年 | 493篇 |
2024年 | 5463篇 |
2023年 | 4959篇 |
2022年 | 6854篇 |
2021年 | 9659篇 |
2020年 | 8412篇 |
2019年 | 7300篇 |
2018年 | 20501篇 |
2017年 | 20260篇 |
2016年 | 16585篇 |
2015年 | 9772篇 |
2014年 | 11747篇 |
2013年 | 13576篇 |
2012年 | 17169篇 |
2011年 | 24338篇 |
2010年 | 21269篇 |
2009年 | 17899篇 |
2008年 | 18784篇 |
2007年 | 19342篇 |
2006年 | 12455篇 |
2005年 | 11913篇 |
2004年 | 8309篇 |
2003年 | 7349篇 |
2002年 | 5984篇 |
2001年 | 4954篇 |
2000年 | 5602篇 |
1999年 | 6509篇 |
1998年 | 5516篇 |
1997年 | 4492篇 |
1996年 | 4238篇 |
1995年 | 3511篇 |
1994年 | 2832篇 |
1993年 | 1984篇 |
1992年 | 1572篇 |
1991年 | 1265篇 |
1990年 | 948篇 |
1989年 | 756篇 |
1988年 | 548篇 |
1987年 | 346篇 |
1986年 | 288篇 |
1985年 | 205篇 |
1984年 | 155篇 |
1983年 | 119篇 |
1982年 | 136篇 |
1981年 | 104篇 |
1980年 | 77篇 |
1968年 | 47篇 |
1965年 | 48篇 |
1955年 | 64篇 |
1954年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A simple, inexpensive and one-step synthesis method of metal-containing carbon nanocapsules using an arc discharge in aqueous solution is reported. It was found that Ni, Co and Fe nanoparticles could be in situ encapsulated in carbon shells when the arc was performed respectively in aqueous solutions of NiSO4, CoSO4 and FeSO4. Transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction patterns of selected areas were used to determine the crystalline phase of the metal cores. To explain the formation mechanism of metal-containing carbon nanocapsules, a model of discharge in solution is proposed. This result presents a simply controllable way to synthesize metal-containing carbon nanocapsules. 相似文献
93.
94.
为了在新形势下的教育体制改革中有所发展和进步,幼儿园管理面临着巨大的挑战.作为一名优秀的管理者,应总结当前管理工作的不足之处,结合幼儿园自身的特点,响应政府的改革计划,制订符合本园发展的特色制度,以人为本、科学管理,以实现儿童的全面发展. 相似文献
95.
96.
Multilayered protein films which contained ordered layers of photosynthetic reaction center (RC) from Rhodobacter Sphaeroides (RS601) were assembled by means of alternate electrostatic adsorption with positively charged poly(diallyldimethylammonium chloride) (PDDA). The assembly of RC was monitored by spectrometry and photocurrent measurement. Linear film growth was observed up to about 20 cycles of adsorption. For the monolayer film, the photocurrent was about 8.5 nA cm−2. For the multilayered film, the total photocurrent was about 77 nA cm−2 for the 24-layer RC film, while the average photocurrent increment per adsorption cycle was about 3.2 nA cm−2. The overall light-to-electricity conversion efficiency for a 24-layer film was about eight times higher than that for the monolayer one. The effects of electrode potential and pH on the photocurrent were also measured to illustrate the light-to-electric converting mechanism. 相似文献
97.
This paper presents a mathematical model based on the reaction rate expressions to describe the displacement of methane conversion in the steam reforming. The effect of several parameters including weight hourly space velocity (WHSV), load-to-surface ratio, reaction pressure, hydrogen partial pressure in permeate side and reaction temperature were investigated. Simulation and experimental results showed that a conversion higher than 80% could be achieved in a palladium membrane reactor at reaction temperature of 500 °C relative to 850 °C in a conventional fixed bed reactor (FBR). Besides, the yield of CO (<2%) in membrane reactor was much lower than that (>50%) in the FBR, which indicated the significant depression of CO production in use of membrane reactor. 相似文献
98.
本文在概述软件教学体系及其理论的基础上,结合软件教学的特点,阐述了软件教学体系的结构、应用环境以及在教学中将遇到的问题和解决对策,并描述了"软件教学资源网系统"建立的目的、设计方案、功能及开发环境。 相似文献
99.
A novel and simple growth mark method was developed to make marks during the growth process of carbon nanotube arrays. These marks can be read out under scanning electron microscope or optical microscope. Based on this method, the growth rates at different temperatures and under different acetylene partial pressures were measured, from which the activation energy and the order of reaction were determined. Based on our experimental results, the growth of carbon nanotube arrays in our experimental condition could not be diffusion-limited. The measured activation energy could possibly be attributed to the heterogeneous decomposition of acetylene over the catalyst particle. Furthermore the marked array with special segmental structure may be found some applications in the future. 相似文献
100.
女性馆员是高校图书馆事业发展的重要生力军,而女性馆员在进行职业岗位的择选、调整、变化,实现自我价值增值等方面面临多种冲突与困惑。如何保护女性馆员的权益,保障她们拥有与男性平等的发展权、建立社会支持系统和法律制度的保障,是全体高校女性馆员的呼声。 相似文献