全文获取类型
收费全文 | 1113篇 |
免费 | 78篇 |
专业分类
电工技术 | 5篇 |
综合类 | 6篇 |
化学工业 | 483篇 |
金属工艺 | 10篇 |
机械仪表 | 10篇 |
建筑科学 | 59篇 |
矿业工程 | 5篇 |
能源动力 | 22篇 |
轻工业 | 190篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 59篇 |
一般工业技术 | 142篇 |
冶金工业 | 62篇 |
原子能技术 | 2篇 |
自动化技术 | 130篇 |
出版年
2024年 | 6篇 |
2023年 | 32篇 |
2022年 | 116篇 |
2021年 | 121篇 |
2020年 | 51篇 |
2019年 | 41篇 |
2018年 | 38篇 |
2017年 | 50篇 |
2016年 | 34篇 |
2015年 | 48篇 |
2014年 | 37篇 |
2013年 | 67篇 |
2012年 | 60篇 |
2011年 | 73篇 |
2010年 | 61篇 |
2009年 | 43篇 |
2008年 | 50篇 |
2007年 | 34篇 |
2006年 | 33篇 |
2005年 | 22篇 |
2004年 | 21篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有1191条查询结果,搜索用时 15 毫秒
91.
Díaz MD Palomino-Schätzlein M Corzana F Andreu C Carbajo RJ del Olmo M Canales-Mayordomo A Pineda-Lucena A Asensio G Jiménez-Barbero J 《Chembiochem : a European journal of chemical biology》2010,11(17):2424-2432
The conformations of two synthetic pentapeptides with antimicrobial activity and their 4-fluorophenylalanine (Pff)-containing analogues (ArXArXAr-NH(2); Ar=Phe, Pff; X=Lys, Arg) have been studied. NMR experiments carried out both in aqueous fluoroalcohol solutions and SDS micelles permitted their interactions with membrane-like environments to be explored. WaterLOGSY experiments and Mn(2+)-based paramagnetic probes were also applied to assess their orientations with respect to the SDS micelles. In addition, pulse-field gradient (PFG) diffusion NMR spectroscopy studies were conducted, under different experimental conditions (i.e., concentration, temperature) to characterize the possible changes in the peptides' aggregation states as a putative critical factor for their antimicrobial activity. Finally, molecular dynamics simulations on a variety of conformations showed the intrinsic flexibility of these peptides in both aqueous solutions and membrane-mimetic systems. 相似文献
92.
Martina Baeumler Frank Gütle Vladimir Polyakov Markus Cäsar Michael Dammann Helmer Konstanzer Wilfried Pletschen Wolfgang Bronner Rüdiger Quay Patrick Waltereit Michael Mikulla Oliver Ambacher Franck Bourgeois Reza Behtash Klaus J. Riepe Paul J. van der Wel Jos Klappe Thomas Rödle 《Journal of Electronic Materials》2010,39(6):756-760
93.
Martina Rejtharová Libor Rejthar Katarína Čačková 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(2):233-240
A sensitive and robust confirmatory method for determination of steroid esters in blood serum is essential for reliable monitoring of possible illegal use of steroid hormones as growth promoters in meat production. A previously used sample preparation methodology was improved. The procedure consists of protein precipitation and removal of phospholipids by dispersive SPE Supel? QuE Z-Sep (Sigma-Aldrich) followed by clean-up on alumina column and LC-MS/MS measurement. The modified method has been validated according to Commission Decision 2002/657/EC. Validation parameters for determination of six testosterone esters and five nortestosterone esters in bovine and porcine blood serum are presented in this article. Decision limits for all analytes were observed in the range 10–20 pg mL?1. The method described is considerably robust for bovine and porcine serum analyses and can be applied both for screening and confirmatory determination in routine residue monitoring. 相似文献
94.
95.
Atomic force microscopy (AFM) can image materials at the nanometer scale and obtain quantitative information
on their surface energy, roughness and hardness (Morris et al. 1999). AFM has also been used to quantify
changes in the surface properties of polymer films and coatings exposed to UV radiation or natural weathering,
but it has not been used to assess the photodegradation of wood (Biggs et al. 2001). The advantage of
using AFM to assess the photodegradation of polymers lies in its ability to reveal early changes in the
material on a nanometer scale and elucidate mechanisms responsible for such degradation. This study examined
if AFM could provide similar information and insights for wood exposed to solar radiation. 相似文献
96.
Ulrike Cress Katrin Wodzicki Martina Bientzle Andreas Lingnau 《International Journal of Computer-Supported Collaborative Learning》2011,6(2):307-321
Computer-supported collaborative learning has an unexploited potential of becoming an effective learning method for pupils
with intellectual disabilities. This paper aims at showing how some specific requirements of this target group may be met
by structuring a learning situation with the help of floor control, which restricts the opportunities of a learning dyad to act simultaneously within the learning environment. It was expected
that floor control could improve communication between pupils with intellectual disabilities by explicitly structuring and restricting activities
in the learning environment and making it necessary for the pupils to communicate. To examine if floor control really supports the collaboration process in the hypothesized way, two different versions of a CSCL environment were implemented
and compared. The results revealed improved task-related communication and a higher quality of interaction outcomes. 相似文献
97.
Building on recent research investigating the role of life-course factors (including childhood conditions) and societal context in older Europeans health status, this study investigates the determinants of changes in elders’ health across two waves of the Survey of Health Ageing and Retirement in Europe (SHARE). Controlling for individuals’ current living conditions at baseline, our analysis provides evidence for long-term associations between childhood conditions (SES, health, cognition) and health dynamics in older age. Moreover, our findings suggest that income inequality tends to increase elders’ risk of experiencing negative health changes (decreases their chance to recover from poor health, respectively). Our study underlines the importance of accounting for both life-course and societal determinants of later life health dynamics. 相似文献
98.
Martina Rudnicki Marcos Roberto de Oliveira Tiago da Veiga Pereira Flávio Henrique Reginatto Felipe Dal-Pizzol José Cláudio Fonseca Moreira 《Food chemistry》2007,100(2):719-724
The leaves of Passiflora alata Dryander and Passiflora edulis Sims, traditionally used in American countries to treat both anxiety and nervousness by folk medicine, are rich in polyphenols, which have been reported as natural antioxidants. In this study, the antioxidant activities of P. edulis and P. alata hydroalcoholic leaf extracts were verified in in vitro and ex vivo assays. P. alata showed a higher total reactive antioxidant potential than did P. edulis. The antioxidant activities of both extracts were significantly correlated with polyphenol contents. In addition, both extracts attenuated ex vivo iron-induced cell death, quantified by lactate dehydrogenase leakage, and effectively protected against protein damage induced by iron and glucose. These findings demonstrate that the P. alata and P. edulis leaf extracts have potent in vitro and ex vivo antioxidant properties and might be considered as possible new sources of natural antioxidants. 相似文献
99.
Which kind of instruction helps children aged 9–14 years interact efficiently with a mobile phone? Due to analogies between navigation in menu structures and the natural environment, three instructions providing different forms of spatial knowledge were under study: A step-by-step instruction featuring landmark knowledge of the menu functions to be selected, a diagram of the menu structure providing survey knowledge and a free exploration of the menu, also giving the children the opportunity to develop survey knowledge. Results show a superiority of the two instructions that provide survey knowledge, except for the youngest children aged 9–10 years. This group showed to have lower spatial abilities and is therefore presumably not able to understand and integrate this type of knowledge. For those very young children, the landmark information given in traditional step-by-step instructions is more helpful. It is concluded, that simple diagrams of the menu structure can help children from 11 years on to significantly ease their interaction with small menu driven devices. 相似文献
100.
Di Lieto A. Minguzzi P. Pirastu A. Magni V. 《Quantum Electronics, IEEE Journal of》2003,39(7):903-909
We describe the development of Nd:YVO/sub 4/ lasers with continuous-wave emission at 1.342 /spl mu/m; they contain either one or two crystals which are longitudinally pumped by fiber-coupled diode laser arrays. With a single crystal, the output power is 7.3 W, while with the twin crystal configuration the power reaches 12 W. The best slope efficiency is 40% and the output beam divergence is about two times the diffraction limit. The influence of the Nd concentration, of the pump spot-size, and of the resonator configuration have been experimentally studied. Data on the thermally induced lens are also reported and discussed. 相似文献