全文获取类型
收费全文 | 38741篇 |
免费 | 2222篇 |
国内免费 | 123篇 |
专业分类
电工技术 | 457篇 |
综合类 | 234篇 |
化学工业 | 7513篇 |
金属工艺 | 758篇 |
机械仪表 | 902篇 |
建筑科学 | 1459篇 |
矿业工程 | 113篇 |
能源动力 | 1161篇 |
轻工业 | 5928篇 |
水利工程 | 323篇 |
石油天然气 | 172篇 |
武器工业 | 6篇 |
无线电 | 3077篇 |
一般工业技术 | 6176篇 |
冶金工业 | 6971篇 |
原子能技术 | 265篇 |
自动化技术 | 5571篇 |
出版年
2024年 | 71篇 |
2023年 | 278篇 |
2022年 | 522篇 |
2021年 | 1095篇 |
2020年 | 800篇 |
2019年 | 885篇 |
2018年 | 1094篇 |
2017年 | 1181篇 |
2016年 | 1238篇 |
2015年 | 984篇 |
2014年 | 1416篇 |
2013年 | 2482篇 |
2012年 | 2210篇 |
2011年 | 2344篇 |
2010年 | 1702篇 |
2009年 | 1727篇 |
2008年 | 1657篇 |
2007年 | 1474篇 |
2006年 | 1235篇 |
2005年 | 1140篇 |
2004年 | 1173篇 |
2003年 | 1051篇 |
2002年 | 1029篇 |
2001年 | 840篇 |
2000年 | 671篇 |
1999年 | 649篇 |
1998年 | 2197篇 |
1997年 | 1459篇 |
1996年 | 1021篇 |
1995年 | 700篇 |
1994年 | 553篇 |
1993年 | 603篇 |
1992年 | 260篇 |
1991年 | 315篇 |
1990年 | 248篇 |
1989年 | 215篇 |
1988年 | 237篇 |
1987年 | 177篇 |
1986年 | 189篇 |
1985年 | 208篇 |
1984年 | 153篇 |
1983年 | 109篇 |
1982年 | 140篇 |
1981年 | 137篇 |
1980年 | 133篇 |
1979年 | 114篇 |
1978年 | 87篇 |
1977年 | 151篇 |
1976年 | 244篇 |
1975年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Andrés Mario Zervigón 《History of Photography》2019,43(2):130-143
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could. 相似文献
32.
Gabriel Rodrigues de Almeida Neto Cesar Augusto Gonçalves Beatrice Daniel Rodrigo Leiva Luiz Antonio Pessan 《International Journal of Hydrogen Energy》2021,46(46):23767-23778
This study investigates the preparation of polyetherimide (PEI) – LaNi5 composites films for hydrogen storage. Prior to the polymer addition, LaNi5 was ball-milled at different conditions (250, 350, and 450 RPM) and annealed at 500 °C for 1 h under vacuum. The composites were produced with BM-LaNi5-350 (PEI/LaNi5-350) and annealed BM-LaNi5-350 (PEI/LaNi5-350-TT). Membranes were successfully produced through solvent casting assisted by an ultrasonic bath. The particles dispersion and the film morphology did not change after hydrogenation cycles. In the H2 sorption experiments at 43 °C and 20 bar, the films stored H2 without incubation time; both samples reached a capacity of ~0.6 wt%. The H2 sorption kinetics of PEI/LaNi5-350 was comparable to that of BM-LaNi5-350, whereas PEI/LaNi5-350-TT presented significantly slower kinetics. LaNi5 oxidation was hindered by PEI, showing that it can be explored to improve metal hydrides air resistance. The results demonstrated that PEI films filled with LaNi5 are promising materials for hydrogen storage. 相似文献
33.
Dr. Alejandra A. Carriles Alberto Mills Dr. María-José Muñoz-Alonso Dr. Dolores Gutiérrez Dr. Juan M. Domínguez Prof. Dr. Juan A. Hermoso Prof. Dr. Federico Gago 《Chembiochem : a European journal of chemical biology》2021,22(2):374-391
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades. 相似文献
34.
Lydia Saidi Dr. Djenisa H. A. Rocha Dr. Oualid Talhi Dr. Yamina Bentarzi Prof. Dr. Bellara Nedjar-Kolli Dr. Khaldoun Bachari Dr. Filipe A. Almeida Paz Dr. Luisa A. Helguero Prof. Dr. Artur M. S. Silva 《ChemMedChem》2019,14(10):1041-1048
Breast and prostate cancers are frequently treated with chemotherapy. Several novel chemicals are being reported for this purpose, particularly synthetic and natural benzophenones. This work reports the synthesis of substituted 2-hydroxybenzophenones through 1,4-conjugate addition/intramolecular cycloaddition/dehydration of nitromethane on key intermediate chromones. Structures were extensively studied by means of 2D NMR spectroscopy and single-crystal XRD. Their cytotoxicity was evaluated in vitro in two breast cancer cell lines (MDA-MB-231 and T47-D) and one prostate cancer cell line (PC3). The most potent compound exhibited good cytotoxic effects against the three cancer cell lines (IC50 values ranging from 12.09 to 26.49 μm ) and induced cell-cycle retardation only on prostate cancer cells, which suggested that it might exert cell-type-specific effects. 相似文献
35.
36.
Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution
下载免费PDF全文
![点击此处可从《Polymer International》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Elton Jorge da Rocha Rodrigues Roberto Pinto Cucinelli Neto Pedro José Oliveira Sebastião Maria Inês Bruno Tavares 《Polymer International》2018,67(6):675-683
The potential of time‐domain nuclear magnetic resonance (TD‐NMR) for the real‐time monitoring of solution radical polymerizations is demonstrated. A model system composed of a redox‐pair initiator system, acrylamide as monomer and water as solvent was investigated. A second‐generation continuous wave free precession technique was employed to measure the longitudinal relaxation time constant (T1) of the samples throughout the polymerization reactions. This parameter was shown to be sensitive to the reactant feed free‐radical enhancement of the water molecule relaxation time, making it a good probe to monitor monomer conversion in real time in an automated, non‐destructive fashion. It was found that the T1 value was better than the transverse relaxation time constant (T2) for describing the evolution of the polymerization reactions, due to its greater sensitivity to paramagnetic effects. The TD‐NMR signal variation observed was linked to the formation, propagation and termination steps of the radical polymerization kinetics scheme. These first results may contribute to the application of real‐time monitoring of radical polymerization reactions employing low‐cost and robust TD‐NMR spectrometers. © 2018 Society of Chemical Industry 相似文献
37.
László Lőrincz Máté Zsemberi György Bánsághi Tamás Sohajda Edit Székely 《化学工程与技术》2018,41(7):1466-1472
Chiral molecules, especially enantiomers and diastereomers of purity > 99 %, present a significant market share within the chemical, pharmaceutical, and flavor industries. Antisolvent precipitations, both batch and semicontinuous operations to serve the current trends in flow chemistry were demonstrated to be environmentally benign and efficient tools in achieving high optical purities. Although salts are known to be insoluble in supercritical CO2, instabilities of the nascent salts were detected and applied for increasing efficiency. Diastereomeric excess values of the crystalline products exceeded 99 % in maximum of three consecutive steps both by repeated resolution with half molar equivalent of the amine to the acid and by direct recrystallization of the salts. 相似文献
38.
39.
40.