全文获取类型
收费全文 | 14505篇 |
免费 | 1094篇 |
国内免费 | 841篇 |
专业分类
电工技术 | 321篇 |
技术理论 | 5篇 |
综合类 | 2577篇 |
化学工业 | 965篇 |
金属工艺 | 281篇 |
机械仪表 | 454篇 |
建筑科学 | 1993篇 |
矿业工程 | 235篇 |
能源动力 | 140篇 |
轻工业 | 2413篇 |
水利工程 | 170篇 |
石油天然气 | 280篇 |
武器工业 | 47篇 |
无线电 | 867篇 |
一般工业技术 | 745篇 |
冶金工业 | 401篇 |
原子能技术 | 89篇 |
自动化技术 | 4457篇 |
出版年
2024年 | 14篇 |
2023年 | 125篇 |
2022年 | 246篇 |
2021年 | 320篇 |
2020年 | 305篇 |
2019年 | 283篇 |
2018年 | 250篇 |
2017年 | 314篇 |
2016年 | 317篇 |
2015年 | 384篇 |
2014年 | 778篇 |
2013年 | 662篇 |
2012年 | 964篇 |
2011年 | 1045篇 |
2010年 | 973篇 |
2009年 | 1001篇 |
2008年 | 1106篇 |
2007年 | 1309篇 |
2006年 | 1158篇 |
2005年 | 882篇 |
2004年 | 849篇 |
2003年 | 648篇 |
2002年 | 514篇 |
2001年 | 405篇 |
2000年 | 333篇 |
1999年 | 251篇 |
1998年 | 202篇 |
1997年 | 150篇 |
1996年 | 127篇 |
1995年 | 100篇 |
1994年 | 100篇 |
1993年 | 71篇 |
1992年 | 53篇 |
1991年 | 41篇 |
1990年 | 47篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 5篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1965年 | 2篇 |
1963年 | 2篇 |
1961年 | 1篇 |
1955年 | 5篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Jianrong Xia Hanyu Xue Renjin Gao Yuchi Zhang Qi Lin 《Polymer Engineering and Science》2021,61(2):489-496
The over-exploitation of finite fossil resources and/or the increased environmental and sustainable awareness inspire scientists and technologists to search for inexpensive alternatives from renewable chemicals. Phenol formaldehyde (PF) resins, the oldest type of synthetic polymers with good mechanical properties and heat resistance, are widely used in the production of coatings, laminates, molding compositions, and glues. Here, biobased urushiol-derived PF resins were synthesized from the alkali-catalyzed reaction between urushiol and formaldehyde. The chemical compositions and molecular structures of resole resins were characterized by carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy, and their curing behaviors were studied by differential scanning calorimetry. The as-prepared urushiol-derived resole resins had methylol (Ph−CH2OH), ortho- and para-hemiformal groups (Ph−CH2OCH2OH), and the para−para/ortho−para/ortho−ortho links of methylene groups (Ph−CH2−Ph), whereas the resole resins had low curing temperatures at about 100–113°C. Additionally, given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol-derived resole resins had low glass transition temperatures of 132 ± 2°C. Furthermore, the as-prepared urushiol-derived coatings exhibited excellent physical and mechanical properties. 相似文献
2.
为国民身体素质、探索具有中国特色的现代食育之路,必须深入分析与探索中国饮食文化中的食育理念。文章以传统饮食文化为出发点和落脚点,概括出医食同源、饮食有节、饮食有礼等先进的食育观点。分析传统饮食与现代食育的关系,认为食育是弘扬传统饮食文化的重要途径,传统饮食文化是发展现代食育的基础。但探索现代食育仍面临着西方快餐文化冲击和国民食育进程缓慢等困境,必须采取强化国民食育意识、加强食育法制建设、健全食育教育体系、推进食育试点工作等措施促进中国传统饮食文化融入食育体系建设,真正探索具有中国特色的食育之路。 相似文献
3.
Stegobium paniceum (L.) (Coleoptera: Anobiidae) is among the major pests of stored products, causing great damage to stored Chinese medicinal plant materials (CMPMs) in China. Effective control strategies are urgently needed. The aim of this study was to explore the role of volatile organic compounds in the host preference of S. paniceum. First, the olfactory behavioral responses of S. paniceum adults to volatiles from four CMPMs (Panax notoginseng, Angelica sinensis, Gastrodia elata, and Peucedanum praeruptorum) were tested in Y-tube olfactometer experiments. Then, the volatile composition of these plant materials were analyzed by gas chromatography-mass spectrometry (GC-MS). S. paniceum showed significant preferences for volatiles from the four CMPMs, compared with clean air (CA). When S. paniceum was presented with choices among different CMPMs, it showed the strongest preference for P. notoginseng, followed by A. sinensis, then G. elata, and P. praeruptorum. GC-MS analysis identified 43, 34, 28 and 60 components in the volatile profiles of P. notoginseng, A. sinensis, G. elata, and P. praeruptorum, respectively. Falcarinol (14.4%), 3-n-butyl phthalide (78.7%), p-cresol (40.1%), and β-pinene (29.1%) were the most abundant components of the volatiles of P. notoginseng, A. sinensis, G. elata, and P. praeruptorum, respectively. The olfactory responses of S. paniceum to the four CMPMs demonstrated that host-related volatiles play an important role in the host-searching process by adult beetles. This information will be useful for the development of safe and effective trapping strategies for this pest. 相似文献
4.
The aims of this study were to assess the psocids that potentially carry Rickettsia and to characterize Rickettsia species. We collected booklice from dried fragments of Chinese medicinal herbs for retail. Species identification and Rickettsia detection were performed by using nondestructive DNA extraction method and PCR. Of the 224 booklice samples collected, the following species were identified: Liposcelis pearmani (50.89%), L. bostrychophila (25.89%) and L. entomophila (23.21%). Twenty-four samples were found to be positive for Rickettsia (10.71%, 24/224), and the number of Rickettsia-positive samples per species was as follows: L. pearmani (n = 10), L. bostrychophila (n = 8) and L. entomophila (n = 6). The phylogenetic tree revealed that the rickettsial agents found in booklice cluster along with Rickettsia felis belong to the spotted fever group (SFG). Mixed booklice contamination occurs in herbal fragments. The presence of Rickettsia-infected booklice suggests that there is a risk of louse-borne rickettsioses to humans in contact with herbs. These findings can contribute to the development of a disease control program that assists relevant practitioners and promotes public health. 相似文献
5.
在铁路运煤装车过程中为了快速、准确地识别车号,提出一种基于机器视觉的运煤车车号识别技术。将连通区域提取与投影分割法结合,实现车号的粗定位、细分割,并对图像中的断裂字符进行二次分割,构建了基于BP神经网络的分类模型进行车号识别,提升了煤炭装车的效率和精度。 相似文献
6.
7.
安维华 《计算机工程与应用》2019,55(23):1-6
传统的汉字书写教学方法具有一定的局限性,为此人们开始关注计算机辅助的汉字书写教学技术。它主要研究汉字书写规范的智能化、自动化评判方法以及可视化的反馈形式。对近20年来计算机辅助汉字书写教学技术的发展情况进行了综述;详细介绍了数字化展示、书写评判、水平评测等几个研究分支的特点、关键问题以及主要成果;结合相关技术的发展和需求的变化,提出了汉字书写数字化教学技术在未来的发展方向。 相似文献
8.
9.
经过几千年的发展和接受,儒家逐步确立了在中国主流意识形态中的“正典”地位。但应该承认,我们对于儒家的接受并不是不加批判全盘照搬的。在这两千多年的时间里,社会生活和意识形态领域所发生的重大变化我们不可能视而不见,而儒家思想恰恰有很大一部分是属于社会学科范畴之内的,在今天明显已经失去积极的意义(比如一些封建宗法),对此当然不能过分坚持,否定发展。因此,对于当今海外的“新儒家”的一些做法,可以欣赏他们对于中国传统文化的热忱,但必须承认那只是一部分知识分子的精英心态,从社会学的眼光看,的确过于保守,不利于文化的创造,特别是不能适应于现代艺术和设计的发展。本文希望区分出儒家思想中具有时代性和永恒性两个方面的内容,在对其已没有价值的社会伦理思想自觉进行发展的同时,对其永恒的东西进行一种当代的阐释。 相似文献
10.
《International Journal of Hydrogen Energy》2021,46(74):36801-36810
Sodium 9,10-anthraquinone-2,6-disulfonate (Na2AQ26DS, 130 mAh g−1) with polyanionic character and two O–Na ionic bonds is used as an organic cathode for Li-ion batteries. Na2AQ26DS exhibits highly impressive cycle stability in ether electrolytes due to its polyanionic character and the effective suppression of solvent-molecule co-intercalation. In half cells (1–3.9 V vs. Li+/Li) using 1 M bis(trifluoromethanesulphonyl)imide lithium salt (LiTFSI) in 1,3-dioxolane/dimethoxyethane (DOL/DME), Na2AQ26DS delivers a highly stable specific capacity of 123 mAh g−1 at 50 mA g−1 for 900 cycles (6-month test) and realizes ∼69 mAh g−1 for 2800 cycles at 500 mA g−1. In the full cells with the reduced state (Li4TP) of lithium terephthalate (Li2TP) as the organic anode, the resulting Li4TP II Na2AQ26DS organic lithium-ion batteries (OLIBs) can display a highly stable average discharge capacity of 120 mAh g−1cathode for 100 cycles at 50 mA g−1 and ∼63 mAh g−1cathode for 1200 cycles at 500 mA g−1 in 0.2–3.3 V. 相似文献