全文获取类型
收费全文 | 7143篇 |
免费 | 643篇 |
国内免费 | 354篇 |
专业分类
电工技术 | 503篇 |
综合类 | 435篇 |
化学工业 | 951篇 |
金属工艺 | 417篇 |
机械仪表 | 465篇 |
建筑科学 | 492篇 |
矿业工程 | 194篇 |
能源动力 | 204篇 |
轻工业 | 503篇 |
水利工程 | 144篇 |
石油天然气 | 482篇 |
武器工业 | 71篇 |
无线电 | 856篇 |
一般工业技术 | 835篇 |
冶金工业 | 366篇 |
原子能技术 | 55篇 |
自动化技术 | 1167篇 |
出版年
2024年 | 29篇 |
2023年 | 152篇 |
2022年 | 218篇 |
2021年 | 296篇 |
2020年 | 242篇 |
2019年 | 203篇 |
2018年 | 228篇 |
2017年 | 253篇 |
2016年 | 204篇 |
2015年 | 305篇 |
2014年 | 378篇 |
2013年 | 448篇 |
2012年 | 500篇 |
2011年 | 537篇 |
2010年 | 423篇 |
2009年 | 442篇 |
2008年 | 397篇 |
2007年 | 381篇 |
2006年 | 390篇 |
2005年 | 359篇 |
2004年 | 239篇 |
2003年 | 205篇 |
2002年 | 200篇 |
2001年 | 162篇 |
2000年 | 144篇 |
1999年 | 139篇 |
1998年 | 114篇 |
1997年 | 114篇 |
1996年 | 106篇 |
1995年 | 78篇 |
1994年 | 59篇 |
1993年 | 38篇 |
1992年 | 39篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有8140条查询结果,搜索用时 15 毫秒
91.
92.
Xuan Peng Linxiu Cheng Xiaoyang Zhu Yanfang Geng Fengying Zhao Kandong Hu Xuan Guo Ke Deng Qingdao Zeng 《Nano Research》2018,11(11):5823-5834
The two-dimensional self-assembly behaviors of tetraphenylethylene (TPE) molecules are significant for further applications, but reports are rare. The self-assembled structures of two C2-symmetry TPE derivatives (H4TCPE and H4ETTC) possessing propeller structures and their stimulus responses to the addition of vinylpyridine derivatives were thoroughly studied with the assistance of scanning tunneling microscopy (STM) technique in combination with density functional theory (DFT) calculations. Although their chemical structures were similar, the H4TCPE and H4ETTC molecules self-assembled into closely packed lamellar and quadrilateral structures, respectively, at the 1-heptanoic acid/HOPG interface. After the addition of pyridine derivatives (DPE, PEBP-C4, and PEBP-C8), H4TCPE and H4ETTC showed different responsiveness resulting in different co-assembly structures. The results indicated that the structures of pyridine derivatives—including backbones and substituents—affected the intermolecular interactions of both H4TCPE/pyridine and H4ETTC/pyridine systems. The modification of the self-assembly behaviors of propeller-shaped H4TCPE and H4ETTC would contribute to the construction of more complex multilevel nanostructures. 相似文献
93.
Jiabin Liu Jiawei Deng Yangyang Zhu Xiaokang Geng Lifu Zhang Sang Young Jeong Dan Zhou Han Young Woo Dong Chen Feiyan Wu Lie Chen 《Advanced materials (Deerfield Beach, Fla.)》2023,35(1):2208008
With the great potential of the all-polymer solar cells for large-area wearable devices, both large-area device efficiency and mechanical flexibility are very critical but attract limited attention. In this work, from the perspective of the polymer configurations, two types of terpolymer acceptors PYTX-A and PYTX-B (X = Cl or H) are developed. The configuration difference caused by the replacement of non-conjugated units results in distinct photovoltaic performance and mechanical flexibility. Benefiting from a good match between the intrinsically slow film-forming of the active materials and the technically slow film-forming of the blade-coating process, the toluene-processed large-area (1.21 cm2) binary device achieves a record efficiency of 14.70%. More importantly, a new parameter of efficiency stretchability factor (ESF) is proposed for the first time to comprehensively evaluate the overall device performance. PM6:PYTCl-A and PM6:PYTCl-B yield significantly higher ESF than PM6:PY-IT. Further blending with non-conjugated polymer donor PM6-A, the best ESF of 3.12% is achieved for PM6-A:PYTCl-A, which is among the highest comprehensive performances. 相似文献
94.
研究了以三氯氧磷为交联剂制备非糊化的高交联玉米淀汾的方法,测定了反应的取代度和布拉班德粘度曲线,研究了在沸水中受热后非糊化淀粉的颗粒形貌及粒度分布等特性。提出高交联玉米淀粉与原淀粉颗粒不同,在沸水中只发生轻度有限溶胀,呈非糊化颗粒态 相似文献
95.
96.
针对目前计算机审计课程教学过程中存在课堂教学与计算机审计实践脱节问题,笔者根据自身教学经验,并结合参与国家审计署项目审计的经历,提出以项目为导向、整体模块化、模块多样化的计算机审计教学方法,实现教学理论与审计实践的较好结合,充分调动教学中两个主体的主观能动性,提高了教学质量。 相似文献
97.
98.
Product-service system (PSS) approach has emerged as a competitive strategy to impel manufacturers to offer a set of product and services as a whole. A three-domain PSS conceptual design framework based on quality function deployment (QFD) is proposed in this research. QFD is a widely used design tool considering customer requirements (CRs). Since both product and services influence satisfaction of customer, they should be designed simultaneously. Identification of the critical parameters in these domains plays an important role. Engineering characteristics (ECs) in the functional domain include product-related ECs (P-ECs) and service-related ECs (S-ECs). ECs are identified by translating customer requirements (CRs) in the customer domain. Rating ECs’ importance has a great impact on achieving an optimal PSS planning. The rating problem should consider not only the requirements of customer, but also the requirements of manufacturer. From the requirements of customer, the analytic network process (ANP) approach is integrated in QFD to determine the initial importance weights of ECs considering the complex dependency relationships between and within CRs, P-ECs and S-ECs. In order to deal with the vagueness, uncertainty and diversity in decision-making, the fuzzy set theory and group decision-making technique are used in the super-matrix approach of ANP. From the requirements of manufacturer, the data envelopment analysis (DEA) approach is applied to adjust the initial weights of ECs taking into account business competition and implementation difficulty. A case study is carried out to demonstrate the effectiveness of the developed integrated approach for prioritizing ECs in PSS conceptual design. 相似文献
99.
Fazhan Geng 《Computers & Mathematics with Applications》2011,61(8):1935-1938
In this paper, an improved variational iteration method is presented for solving Duffing equations involving both integral and non-integral forcing terms. The main advantage of this modification over the standard variational iteration method (VIM) is that it can avoid unnecessary repeated computation in determining the unknown parameters in the initial solution. Numerical results reveal that the improved method is simple and efficient. 相似文献
100.
Fazhan Geng 《Computers & Mathematics with Applications》2011,62(4):1641-1644
In this paper, we introduce a piecewise variational iteration method for treating a nonlinear oscillator of a mass attached to a stretched elastic wire. For the nonlinear oscillator, the present method can produce a good approximation to the exact solution in a very large region, while the standard variational iteration method (VIM) gives a good approximation only in a small region. The numerical results obtained show that the present method does not share the drawback of the standard VIM and can provide very accurate analytical approximate solutions for both small and large values of the oscillation amplitude and parameter. 相似文献