全文获取类型
收费全文 | 1578篇 |
免费 | 47篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 17篇 |
综合类 | 3篇 |
化学工业 | 401篇 |
金属工艺 | 24篇 |
机械仪表 | 40篇 |
建筑科学 | 69篇 |
矿业工程 | 7篇 |
能源动力 | 42篇 |
轻工业 | 175篇 |
水利工程 | 11篇 |
石油天然气 | 1篇 |
无线电 | 127篇 |
一般工业技术 | 222篇 |
冶金工业 | 152篇 |
原子能技术 | 18篇 |
自动化技术 | 322篇 |
出版年
2023年 | 17篇 |
2022年 | 49篇 |
2021年 | 63篇 |
2020年 | 25篇 |
2019年 | 27篇 |
2018年 | 35篇 |
2017年 | 33篇 |
2016年 | 58篇 |
2015年 | 31篇 |
2014年 | 41篇 |
2013年 | 106篇 |
2012年 | 84篇 |
2011年 | 98篇 |
2010年 | 76篇 |
2009年 | 80篇 |
2008年 | 78篇 |
2007年 | 77篇 |
2006年 | 67篇 |
2005年 | 56篇 |
2004年 | 54篇 |
2003年 | 43篇 |
2002年 | 41篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 53篇 |
1997年 | 45篇 |
1996年 | 20篇 |
1995年 | 28篇 |
1994年 | 30篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1939年 | 7篇 |
1938年 | 6篇 |
1937年 | 7篇 |
排序方式: 共有1631条查询结果,搜索用时 12 毫秒
61.
Enhancing the temporal resolution of satellite-based flood extent generation using crowdsourced data for disaster monitoring 总被引:1,自引:0,他引:1
Remote-sensing satellite data are routinely used during disasters for damage assessment and to coordinate relief operations. Although there is a plethora of satellite sensors able to provide actionable data about an event, their temporal resolution is limited by their revisit time, presence of clouds, and errors in the reception of data. These limitations do not allow for an uninterrupted monitoring, which is crucial during disasters and emergencies. This research presents an approach that leverages the increased temporal resolution of crowdsourced data to partially overcome the limitations of satellite data. The proposed approach focuses on the geostatistical analysis of a combined satellite and Twitter data to help delineate the flood extent on a daily basis. The crowdsourced data are used to augment satellite imagery from Advanced Land Imager instrument on Earth Observating One (EO-1) satellite, Landsat 8, WorldView-2, and WorldView-3. The proposed methodology was applied to estimate the daily flood extents in Charleston, South Carolina, caused by the October 2015 North American storm complex. The results of the proposed methodology indicate that the user-generated data can be utilized adequately to both bridge the temporal gaps in the satellite-based observations and also increase the spatial resolution of the flood extents. 相似文献
62.
The oxidative coupling of methane (OCM) was carried out in a polytropic fixed-bed reactor applying a Zr/La/Sr catalyst developed by the Neste company. Over this catalyst the OCM reaction follows a complex reaction scheme which includes primary parallel reaction steps to CO, CO2 and C2H6 and consecutive reactions of ethane to ethylene or COx. Yield of higher hydrocarbons C2+ obtained with this catalyst strongly depended on reaction conditions, i.e. low partial pressures of methane and oxygen obtained by diluting the feed gas with nitrogen and high reaction temperatures promoted C2+ selectivity and yield. The maximum yield amounted to 21.4% (20 Vol.-% CH4, 9 Vol.-% O2, 71 Vol.-% N2, T = 860°C; XCH4 = 41.8%, S = 52.5%). This result belongs to the highest yields reported in the open literature. 相似文献
63.
As an alternative to previously developed catalytic FeCrAlloy fibre mat burners based on perovskite catalysts, new catalytic burners have been developed based on Pd catalyst on lantana-stabilised Al2O3 and different fibre structures (NIT100A, NIT100S and NIT200S by ACOTECH NV). All development steps are considered, shifting from catalyst preparation (based on combustion synthesis of γ-Al2O3) to the optimisation of lantana and Pd loadings, from the definitions of the best catalyst-deposition conditions (washcoating) to the catalytic burners performances, determined in an ad hoc developed combustion chamber. The results show almost half pollutants emissions and better performance compared to various non-catalytic counterparts, especially as far as CO and NOx emissions are concerned. Some flame instability problems were though registered, especially for one of the catalytic burner mattresses employed, at low specific power inputs and excesses of air (<375 kW/m2 and <12%, respectively). Further, PdO/Pd transition is shown to influence the dynamic behaviour of the catalytic burners. 相似文献
64.
65.
Guido Walther Andreas Martin Angela Köckritz 《Journal of the American Oil Chemists' Society》2013,90(1):141-145
A selection of plant oils was catalytically transferred into 1,19-nonadecanedioate by a direct transesterification, isomerization and methoxycarbonylation under mild conditions using Pd/o-C6H4(CH2P t Bu2)2. Additionally, sulfuric acid was demonstrated as being able to substitute methane sulfonic acid as co-catalyst without any significant loss of activity and selectivity. 相似文献
66.
Genome-Wide Investigation of Multifocal and Unifocal Prostate Cancer—Are They Genetically Different?
Chinyere Ibeawuchi Hartmut Schmidt Reinhard Voss Ulf Titze Mahmoud Abbas Joerg Neumann Elke Eltze Agnes Marije Hoogland Guido Jenster Burkhard Brandt Axel Semjonow 《International journal of molecular sciences》2013,14(6):11816-11829
Prostate cancer is widely observed to be biologically heterogeneous. Its heterogeneity is manifested histologically as multifocal prostate cancer, which is observed more frequently than unifocal prostate cancer. The clinical and prognostic significance of either focal cancer type is not fully established. To investigate prostate cancer heterogeneity, the genetic profiles of multifocal and unifocal prostate cancers were compared. Here, we report observations deduced from tumor-tumor comparison of copy number alteration data of both focal categories. Forty-one fresh frozen prostate cancer foci from 14 multifocal prostate cancers and eight unifocal prostate cancers were subjected to copy number variation analysis with the Affymetrix SNP 6.0 microarray tool. With the investigated cases, tumors obtained from a single prostate exhibited different genetic profiles of variable degrees. Further comparison identified no distinct genetic pattern or signatures specific to multifocal or unifocal prostate cancer. Our findings suggest that samples obtained from multiple sites of a single unifocal prostate cancer show as much genetic heterogeneity and variability as separate tumors obtained from a single multifocal prostate cancer. 相似文献
67.
Garrett BC Dixon DA Camaioni DM Chipman DM Johnson MA Jonah CD Kimmel GA Miller JH Rescigno TN Rossky PJ Xantheas SS Colson SD Laufer AH Ray D Barbara PF Bartels DM Becker KH Bowen KH Bradforth SE Carmichael I Coe JV Corrales LR Cowin JP Dupuis M Eisenthal KB Franz JA Gutowski MS Jordan KD Kay BD Laverne JA Lymar SV Madey TE McCurdy CW Meisel D Mukamel S Nilsson AR Orlando TM Petrik NG Pimblott SM Rustad JR Schenter GK Singer SJ Tokmakoff A Wang LS Wettig C Zwier TS 《Chemical reviews》2005,105(1):355-390
68.
Francesca Guidi Giovanni Carta Gilberto Rossetto Guido Salmaso 《Electrochimica acta》2005,50(23):4609-4614
Alumina (Al2O3) coatings of different thickness were deposited on OT59 brass substrate (BS) using the metal organic chemical vapour deposition (MOCVD) technique to evaluate the corrosion performance by EIS measurements. The used precursor was dimethyl-aluminium-isopropoxide. Electrochemical characterizations of the deposited films were performed in a standard very aggressive acidic solution (aerated 1N H2SO4 at 25 °C up to 168 h of immersion time) by means of direct current method (Tafel curves) and electrochemical impedance spectroscopy (EIS). The Rutherford backscattering spectroscopy (RBS) indicated that the films are very pure with the correct Al2O3 stoichiometry, while the IR absorption spectra showed that the films did not contain any OH groups. The surface film morphology was investigated by atomic force microscopy (AFM) and displayed a globular texture. The films were very smooth, with a maximum root mean square roughness, for example, of 14 nm for a 0.96 μm thick coating. The EIS data confirmed, as expected, that a 2.40 μm Al2O3 layer ensures the best corrosion protection after 168 h of immersion in the very acidic environment used. 相似文献
69.
Tama Dinur Peter Bauer Christian Beetz Guido Kramp Claudia Cozma Marius-Ionu Iuracu Michal Becker-Cohen Majdolen Istaiti Arndt Rolfs Ari Zimran Shoshana Revel-Vilk 《International journal of molecular sciences》2022,23(3)
For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced β-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1–78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9–1340) ng/mL and 5.4 (1.5–16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9–1050), compared to GD1 and severe GBA1 variants, 447 (38–1340) ng/mL, and neuronopathic GD, 325 (116–1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5–15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5–16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7–10.7) in heterozygous GBA1 carriers with Parkinson’s disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type. 相似文献
70.