全文获取类型
收费全文 | 27027篇 |
免费 | 976篇 |
国内免费 | 337篇 |
专业分类
电工技术 | 208篇 |
综合类 | 7725篇 |
化学工业 | 3846篇 |
金属工艺 | 319篇 |
机械仪表 | 1090篇 |
建筑科学 | 3328篇 |
矿业工程 | 276篇 |
能源动力 | 428篇 |
轻工业 | 390篇 |
水利工程 | 173篇 |
石油天然气 | 137篇 |
武器工业 | 33篇 |
无线电 | 2860篇 |
一般工业技术 | 898篇 |
冶金工业 | 409篇 |
原子能技术 | 39篇 |
自动化技术 | 6181篇 |
出版年
2024年 | 123篇 |
2023年 | 252篇 |
2022年 | 452篇 |
2021年 | 597篇 |
2020年 | 584篇 |
2019年 | 345篇 |
2018年 | 260篇 |
2017年 | 351篇 |
2016年 | 607篇 |
2015年 | 968篇 |
2014年 | 2395篇 |
2013年 | 1535篇 |
2012年 | 2370篇 |
2011年 | 2906篇 |
2010年 | 2611篇 |
2009年 | 2265篇 |
2008年 | 1632篇 |
2007年 | 1724篇 |
2006年 | 1351篇 |
2005年 | 1002篇 |
2004年 | 805篇 |
2003年 | 764篇 |
2002年 | 607篇 |
2001年 | 495篇 |
2000年 | 413篇 |
1999年 | 240篇 |
1998年 | 128篇 |
1997年 | 106篇 |
1996年 | 98篇 |
1995年 | 73篇 |
1994年 | 46篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1984年 | 8篇 |
1982年 | 4篇 |
1977年 | 4篇 |
1966年 | 5篇 |
1963年 | 3篇 |
1962年 | 5篇 |
1961年 | 3篇 |
1959年 | 4篇 |
1957年 | 4篇 |
1956年 | 3篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
11.
土木工程施工课程作为土木工程及工程管理专业的学科基础课和核心专业课程,在疫情防控期间"停课不停教""停课不停学"的要求下,通过线上平台进行授课。由于土木工程施工课程内容庞杂、综合性强、实践性强,且章节之间关联性较弱,探究既能使学生快速适应,又能保证教学质量的在线教学方法至关重要。以华南某高校土木工程施工课程为例,基于中国大学MOOC、建筑云课、腾讯课堂、QQ群等线上平台讲授教学内容,并运用问卷调查对课程线上教学效果进行评价。结果表明,线上教学为学生提供了丰富灵活的学习方式,显著提高了学生的自主学习能力,扩大了学生的知识面,达到了较好的学习效果。 相似文献
12.
《Journal of the European Ceramic Society》2019,39(16):5292-5297
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), which exhibits a high mixed oxide ionic-electronic conduction, was used for the fabrication of an oxygen separation membrane. An asymmetric structure, which was a thin and dense BSCF membrane layer supported on a porous BSCF substrate, was fabricated by the electrophoretic deposition method (EPD). Porous BSCF supports were prepared by the uniaxial pressing method using a powder mixture with BSCF and starch as the pore-forming agent (0–50 wt.%). The sintering behaviors of the porous support and the thin layer were separately characterized by dilatometry to determine the co-fired temperature at which cracking did not occur. A crack-free and thin dense membrane layer, which had about a 15 μm thickness and >95% relative density, was obtained after optimizing the processes of EPD and sintering. The dense/porous interface was well-bonded and the oxygen permeation flux was 2.5 ml (STP) min−1 cm-2 at 850 °C. 相似文献
13.
物理化学课程创新教学模式是以学生学习为中心,吐故纳新,优化精选,以新颖或变化的教学方式进行教学。调查表明创新教学模式受到绝大多数学生的肯定和认可,有效地调动学生的积极性,提高了学生对物理化学的学习和探究兴趣,学生提问问题的广度和难度发生显著变化。该教学模式能够逐步提升学生的创新意识和创新能力。 相似文献
14.
15.
Flotation has been used in industry for more than a half century as the primary technique for upgrading phosphate. While the flotation of phosphate was inefficient when oleic acid was used alone as a collector, therefore a mixed collector of oleic acid (HOl), linoleic acid (LA) and linolenic acid (LNA) was employed to improve the recovery of phosphate flotation. The batch flotation results showed that the optimal composition of the mixed collector was 54 wt.% HOl, 36 wt.% LA and 10 wt.% LNA. Additionally, the effect of pH on the mixed collector application was studied while considering the surface tension, contact angle and micro-flotation. The results showed that the mixed collector should be used at a pH of 9.5. Above a pH of 9.5, the adsorption of fatty acids dimers on the apatite surface hindered phosphate flotation. The influence of the mixed collector assembly on apatite flotation was also investigated. It was demonstrated that due to its low critical micelle concentration, a sufficiently hydrophobic apatite surface could be generated at a collector concentration of 60 mg/L. In addition, zeta potential experiments suggested that collector adsorption was governed by chemisorption. FTIR and XPS spectra studies further indicated that the chemical reaction involved the carboxyl groups of fatty acids and Ca species at the apatite surface for each fatty acid in the mixed collector. 相似文献
16.
The conversion of lignocellulosic biomass (LCB) to microbial oils is attracting a growing amount of attention. However, the growth of the oleaginous yeast Rhodotorula glutinis on LCB hydrolysate (mainly rice straw) only will lead to a low lipid mass fraction, in the range of 10–20%. This study shows that the addition of crude glycerol to the LCB hydrolysate medium can efficiently raise the lipid mass fraction to the range of 30–40%. Crude glycerol is a by-product in the biodiesel production process. The use of renewable LCB hydrolysate and crude glycerol would greatly reduce the substrate cost for microbial oil production using R. glutinis. In addition, the results of experiments show that a low-cost airlift bioreactor is a more suitable fermentation process for the growth of R. glutinis than the use of a conventional agitation tank. When using mixed carbon sources of LCB hydrolysate with 30 kg m−3 of reducing sugars and 30 kg m−3 of crude glycerol, a maximal cell mass of 21.4 kg m−3 and lipid mass fraction of 58.5 ± 6.2 were achieved in an internal loop airlift bioreactor, and this process may have the potential to be applied in scale-up production. 相似文献
17.
要培养学生的创造力,教师主要起引导作用。应提倡感性的观察方法与理性的表现相结合。从构图阶段开始就应该贯穿创新意念,鼓励学生采用大胆新奇的构图,以独特的视觉去观察对象、设计函面,充分发挥学生的主观能动性。 相似文献
18.
G. Murali Dhar B. N. Srinivas M. S. Rana Manoj Kumar S. K. Maity 《Catalysis Today》2003,86(1-4):45-60
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication. 相似文献
19.
混合Hermite-Lagrange插值之同时逼近 总被引:1,自引:1,他引:0
谢庭藩 《中国计量学院学报》1993,(2)
对于(-1,1)中的结点组{X_k}_(k=1)~n,记l_k(x)为相应的Lagrange插值基本多项式,又记A_n=‖∑(2-x~2-x_k~2)(1-x_k~2)~-1丨l_k(x)‖。对于f∈C_([-1,1)~q与r=[q+2/2],本文证明满足条件H_n(f,x_k)=f(x_k)(k=1,2,…,n),H_n~(s)(f,±1)=f~(s)(±1)(s=0,1,…,n-1)的n+2r-1次代数多项式H_n(f,x)有逼近性质H_n~(s)(f,x)-f~(s)(x)=(?)其中δ_n(x)=n~(-1)(1-x~2)~(1/2),△_n(x)=δ_n(x)+n~(-2).作为证明的重要工具,本文还对n次代数多项式P_n(x),建立了另一形式的Bernstein不等武:若 P_n(x)=O(1)δ_n~q(x)ω(δ_n(x)),则p_n~(S)(X)=O(1)δ_n~(q-2S)(X)ω(δ_n(X))△_n~s(X)。 相似文献
20.
林苗 《电气电子教学学报》2002,24(1):43-45
阐述了我校使用“面向21世纪”电工学课程系列教材的实践与探索过程,以及对我校电工学教学所产生的转折性影响和积极的导向作用,最后对教材提出了几点建议。 相似文献