全文获取类型
收费全文 | 5603篇 |
免费 | 156篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 61篇 |
综合类 | 9篇 |
化学工业 | 1024篇 |
金属工艺 | 122篇 |
机械仪表 | 101篇 |
建筑科学 | 247篇 |
矿业工程 | 38篇 |
能源动力 | 87篇 |
轻工业 | 601篇 |
水利工程 | 56篇 |
石油天然气 | 8篇 |
无线电 | 461篇 |
一般工业技术 | 904篇 |
冶金工业 | 1447篇 |
原子能技术 | 52篇 |
自动化技术 | 547篇 |
出版年
2023年 | 31篇 |
2022年 | 50篇 |
2021年 | 93篇 |
2020年 | 65篇 |
2019年 | 73篇 |
2018年 | 90篇 |
2017年 | 87篇 |
2016年 | 100篇 |
2015年 | 72篇 |
2014年 | 125篇 |
2013年 | 275篇 |
2012年 | 184篇 |
2011年 | 259篇 |
2010年 | 195篇 |
2009年 | 167篇 |
2008年 | 215篇 |
2007年 | 189篇 |
2006年 | 192篇 |
2005年 | 143篇 |
2004年 | 140篇 |
2003年 | 147篇 |
2002年 | 124篇 |
2001年 | 115篇 |
2000年 | 98篇 |
1999年 | 114篇 |
1998年 | 348篇 |
1997年 | 235篇 |
1996年 | 199篇 |
1995年 | 122篇 |
1994年 | 148篇 |
1993年 | 122篇 |
1992年 | 81篇 |
1991年 | 50篇 |
1990年 | 65篇 |
1989年 | 89篇 |
1988年 | 53篇 |
1987年 | 49篇 |
1986年 | 54篇 |
1985年 | 51篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 31篇 |
1981年 | 43篇 |
1980年 | 32篇 |
1979年 | 40篇 |
1978年 | 52篇 |
1977年 | 47篇 |
1976年 | 97篇 |
1975年 | 40篇 |
1974年 | 31篇 |
排序方式: 共有5765条查询结果,搜索用时 15 毫秒
1.
Fischer-Tropsch synthesis of the CO2 in biogas aims at producing light hydrocarbons and increasing its calorific value for feeding into the grid. Fe catalysts with Mn and K as promoters are supposed to yield high amounts of light hydrocarbons. Using a Fe-Mn-K/MgO catalyst, a parameter screening and long-term experiments were carried out. The catalyst shows, within the examined range, the highest selectivity to C2–C4 hydrocarbons at 450 °C, 8 bar(a), and a gas hourly space velocity of 350 h−1. Calcination of the catalyst resulted in a significant drop of activity and an almost complete loss of selectivity to hydrocarbons. Admixture of steam to the reactant gas lowers the tendency to carbon deposition but also promotes the water-gas shift reaction and results in lower yields of hydrocarbons. 相似文献
2.
3.
4.
Moritz Raab Simon Maier Ralph-Uwe Dietrich 《International Journal of Hydrogen Energy》2021,46(21):11956-11968
A large-scale point to point hydrogen transport is one strategy for a prospective energy import scenario for certain countries. The case for a hydrogen transport from Australia to Japan has been addressed in several studies. However, most studies lack transparency and detailed insights into the made assumptions thus a fair evaluation of different transport pathways is challenging. To address this issue, we developed a model where a large-scale point to point hydrogen transport of liquid hydrogen is compared with the transport via liquid organic hydrogen carrier (LOHC), namely via methyl cyclohexane and hydrogenated dibenzyl toluene. We analyzed, where energy is required along the different pathways, where hydrogen losses do occur and how the costs are put together. Furthermore, the influence of hydrogen feed costs is also considered. For hydrogen production costs of 5 €2018/kgH2 the total delivery costs are in the range of 6.40– 8.10 €2018/kgH2. 相似文献
5.
Jasmin Kuhn Philipp M. Klein Nader Al Danaf Joel Z. Nordin Sren Reinhard Dominik M. Loy Miriam Hhn Samir El Andaloussi Don C. Lamb Ernst Wagner Yoshitsugu Aoki Taavi Lehto Ulrich Lchelt 《Advanced functional materials》2019,29(48)
Phosphorodiamidate morpholino oligomers (PMOs) are oligonucleotide analogs that can be used for therapeutic modulation of pre‐mRNA splicing. Similar to other classes of nucleic acid‐based therapeutics, PMOs require delivery systems for efficient transport to the intracellular target sites. Here, artificial peptides based on the oligo(ethylenamino) acid succinyl‐tetraethylenpentamine (Stp), hydrophobic modifications, and an azide group are presented, which are used for strain‐promoted azide‐alkyne cycloaddition conjugation with splice‐switching PMOs. By systematically varying the lead structure and formulation, it is determined that the type of contained fatty acid and supramolecular assembly have a critical impact on the delivery efficacy. A compound containing linolenic acid with three cis double bonds exhibits the highest splice‐switching activity and significantly increases functional protein expression in pLuc/705 reporter cells in vitro and after local administration in vivo. Structural and mechanistic studies reveal that the lipopeptide PMO conjugates form nanoparticles, which accelerate cellular uptake and that the content of unsaturated fatty acids enhances endosomal escape. In an in vitro Duchenne muscular dystrophy exon skipping model using H2K‐mdx52 dystrophic skeletal myotubes, the highly potent PMO conjugates mediate significant splice‐switching at very low nanomolar concentrations. The presented aminoethylene‐lipopeptides are thus a promising platform for the generation of PMO‐therapeutics with a favorable activity/toxicity profile. 相似文献
6.
7.
Computer Supported Cooperative Work (CSCW) - 相似文献
8.
H Daims F Maixner S Lücker K Stoecker K Hace M Wagner 《Water science and technology》2006,54(1):21-27
Nitrite-oxidizing bacteria of the genus Nitrospira are key nitrifiers in wastewater treatment plants. Pure cultures of these organisms are unavailable, but cultivation-independent molecular methods make it possible to detect Nitrospira-like bacteria in environmental samples and to investigate their ecophysiology. Comprehensive screening of natural and engineered habitats and of public databases for 16S rRNA sequences of Nitrospira-like bacteria revealed a surprisingly high biodiversity in the genus Nitrospira, which comprises at least four phylogenetic sublineages. All Nitrospira-like bacteria detected in wastewater treatment plants belonged to the sublineages I and II. Subsequently, the population dynamics of different Nitrospira-like bacteria were monitored, by quantitative fluorescence in situ hybridization with rRNA-targeted probes, confocal laser scanning microscopy and digital image analysis, during incubation of nitrifying activated sludge in media containing different nitrite concentrations. These experiments showed that Nitrospira-like bacteria, which were affiliated with the phylogenetic sublineages I or II of the genus Nitrospira, responded differently to nitrite concentration shifts. Previously unknown properties of Nitrospira-like bacteria were discovered in the course of an environmental genomics project. Implications of the obtained results for fundamental understanding of the microbial ecology of nitrite oxidizers as well as for future improvement of nutrient removal in wastewater treatment plants are discussed. 相似文献
9.
We are standing at the beginning of the industrialization of flexible thin-film transistor (TFT) backplanes. The two important research directions for the TFTs are (i) processability on flexible substrates and (ii) sufficient field-effect mobilities of electrons and holes to support complementary metal insulator semiconductor operation. The most important group of TFT capable semiconductors are the several modifications of silicon films: amorphous, nanocrystalline and microcrystalline. We summarize their TFT properties and their compatibility with foil substrate materials. 相似文献
10.
van Dick Rolf; Wagner Ulrich; Pettigrew Thomas F.; Christ Oliver; Wolf Carina; Petzel Thomas; Castro Vanessa Smith; Jackson James S. 《Canadian Metallurgical Quarterly》2004,87(2):211
Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献