全文获取类型
收费全文 | 111097篇 |
免费 | 4631篇 |
国内免费 | 2160篇 |
专业分类
电工技术 | 3725篇 |
技术理论 | 1篇 |
综合类 | 4531篇 |
化学工业 | 15231篇 |
金属工艺 | 6371篇 |
机械仪表 | 5049篇 |
建筑科学 | 4493篇 |
矿业工程 | 1622篇 |
能源动力 | 1935篇 |
轻工业 | 5397篇 |
水利工程 | 1967篇 |
石油天然气 | 1397篇 |
武器工业 | 404篇 |
无线电 | 12707篇 |
一般工业技术 | 19182篇 |
冶金工业 | 3604篇 |
原子能技术 | 625篇 |
自动化技术 | 29647篇 |
出版年
2024年 | 173篇 |
2023年 | 583篇 |
2022年 | 1280篇 |
2021年 | 1891篇 |
2020年 | 1291篇 |
2019年 | 948篇 |
2018年 | 15443篇 |
2017年 | 14397篇 |
2016年 | 10972篇 |
2015年 | 2217篇 |
2014年 | 2015篇 |
2013年 | 2339篇 |
2012年 | 5454篇 |
2011年 | 11704篇 |
2010年 | 10271篇 |
2009年 | 7409篇 |
2008年 | 8463篇 |
2007年 | 9361篇 |
2006年 | 1491篇 |
2005年 | 2276篇 |
2004年 | 1872篇 |
2003年 | 1765篇 |
2002年 | 1113篇 |
2001年 | 553篇 |
2000年 | 546篇 |
1999年 | 317篇 |
1998年 | 239篇 |
1997年 | 177篇 |
1996年 | 165篇 |
1995年 | 120篇 |
1994年 | 70篇 |
1993年 | 59篇 |
1992年 | 61篇 |
1991年 | 43篇 |
1989年 | 39篇 |
1988年 | 25篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 35篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1960年 | 31篇 |
1959年 | 43篇 |
1958年 | 37篇 |
1957年 | 37篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
Atsushi Narumi Kosei Kawasaki Harumi Kaga Toshifumi Satoh Naoya Sugimoto Toyoji Kakuchi 《Polymer Bulletin》2003,49(6):405-410
Summary
The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1-P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-l-P]0 and [maltohexaose]0 of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and
showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amylose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization o f the glucose unit
(n) as 27, 5 1, and 180 for 2-I, 2-II, and 2-III, respectively.
Received: 29 November 2002/Accepted: 22 December 2002
Correspondence to Toyoji Kakuchi 相似文献
52.
ZhaoYahong ZhangZhongpei WuWeiling 《电子科学学刊(英文版)》2003,20(3):177-182
Adaptive modulation and power allocation is introduced into the multicarrier DSCDMA system to improve the system performance and bandwidth efficiency.First,the system design appropriate for adaptive modulation and power allocation is given,then the algorithm of adaptive modulation and power allocation is applied.Simulation results demonstrate great performance improvement compared with the fixed modulated one. 相似文献
53.
As an aid towards improving the treatment of exchange and correlation effects in electronic structure calculations, it is
desirable to have a clear picture of the errors introduced by currently popular approximate exchange-correlation functionals.
We have performed ab initio density functional theory and density functional perturbation theory calculations to investigate
the thermal properties of bulk Cu, using both the local density approximation (LDA) and the generalized gradient approximation
(GGA). Thermal effects are treated within the quasiharmonic approximation. We find that the LDA and GGA errors for anharmonic
quantities are an order of magnitude smaller than for harmonic quantities; we argue that this might be a general feature.
We also obtain much closer agreement with experiment than earlier, more approximate calculations. 相似文献
54.
Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of
semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons
of the tube screen the magnetization of the dopants: the coupling to the tube is usually antiferromagnetic (except for Cr). 相似文献
55.
随着集成电路规模的不断增大,电源网络的重要性日趋显著,电源网络的分布直接影响芯片的电压降(IR-drop)。一种布线后通过在空闲处插入电源桥和地桥的方法,可以在不增加芯片面积的情况下,改善IR-drop效应。实验结果表明在芯片布局利用率不高的情况下(70~75%),该方法可以使IR-drop得到明显的优化。 相似文献
56.
58.
59.
60.
This article proposes a model of the ways in which dyadic interactions between employees who occupy 1 of 4 archetypal social roles in organizations can lead to either episodic or institutionalized patterns of victimization. The model shows how the occurrence of victimization involving these 4 role types is influenced by organizational variables such as power differences, culture, and access to social capital. The model integrates behavioral and social structural antecedents of victimization to develop a relational perspective on the dynamics of harmful behavior in the workplace. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献