全文获取类型
收费全文 | 2289篇 |
免费 | 167篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 967篇 |
金属工艺 | 20篇 |
机械仪表 | 42篇 |
建筑科学 | 64篇 |
矿业工程 | 6篇 |
能源动力 | 65篇 |
轻工业 | 472篇 |
水利工程 | 21篇 |
石油天然气 | 5篇 |
无线电 | 113篇 |
一般工业技术 | 311篇 |
冶金工业 | 89篇 |
原子能技术 | 5篇 |
自动化技术 | 263篇 |
出版年
2024年 | 4篇 |
2023年 | 47篇 |
2022年 | 187篇 |
2021年 | 225篇 |
2020年 | 75篇 |
2019年 | 97篇 |
2018年 | 81篇 |
2017年 | 81篇 |
2016年 | 102篇 |
2015年 | 89篇 |
2014年 | 95篇 |
2013年 | 168篇 |
2012年 | 143篇 |
2011年 | 181篇 |
2010年 | 158篇 |
2009年 | 118篇 |
2008年 | 102篇 |
2007年 | 85篇 |
2006年 | 76篇 |
2005年 | 54篇 |
2004年 | 36篇 |
2003年 | 39篇 |
2002年 | 41篇 |
2001年 | 20篇 |
2000年 | 8篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2457条查询结果,搜索用时 11 毫秒
51.
Chiara Paolini Silvia Agarbati Devis Benfaremo Matteo Mozzicafreddo Silvia Svegliati Gianluca Moroncini 《International journal of molecular sciences》2022,23(7)
Systemic sclerosis (SSc) is a clinically heterogeneous disorder of the connective tissue characterized by vascular alterations, immune/inflammatory manifestations, and organ fibrosis. SSc pathogenesis is complex and still poorly understood. Therefore, effective therapies are lacking and remain nonspecific and limited to disease symptoms. In the last few years, many molecular and cellular mediators of SSc fibrosis have been described, providing new potential options for targeted therapies. In this review: (i) we focused on the PDGF/PDGFR pathway as key signaling molecules in the development of tissue fibrosis; (ii) we highlighted the possible role of stimulatory anti-PDGFRα autoantibodies in the pathogenesis of SSc; (iii) we reported the most promising PDGF/PDGFR targeting therapies. 相似文献
52.
Polysaccharides,oligosaccharides and nitrogenous compounds change during the ageing of Tempranillo and Verdejo sparkling wines 下载免费PDF全文
53.
Manuel Porcar Silvia Ramos Amparo Latorre 《Journal of the science of food and agriculture》2007,87(14):2728-2731
BACKGROUND: The polymerase chain reaction (PCR) is a powerful tool that is being increasingly used for detection of transgenic DNA. PCR requires only a minute quantity of template, but sensitive and accurate testing requires DNA of sufficient purity and free from inhibitors such as plant polysaccharides. Several standard protocols are available for this purpose, but they usually involve several steps, imply destruction of the maize kernel, or are time‐consuming. Our aim was to develop a fast and simple extraction method to isolate a raw DNA‐containing solution from maize tissues suitable for use as a template in a PCR‐based detection assay with specific oligonucleotides directed to the identification of event MON810. RESULTS: The NaOH‐based DNA extraction method we report here is time‐saving (5 min) and can be used to isolate DNA‐containing solutions from a small maize leaf portion (down to 1 mg) or from a single overnight‐germinated kernel. PCR performed with selected primers yielded reproducible detection of transgenic DNA. CONCLUSION: The main advantages of the procedure are the quick extraction step, the possibility of non‐destructive testing of maize kernels, and the robustness of the PCR‐based detection, a consequence of the selection of MON810‐matching oligonucleotides yielding intense and highly specific amplicons. Copyright © 2007 Society of Chemical Industry 相似文献
54.
DNA barcoding as a new tool for food traceability 总被引:1,自引:0,他引:1
Andrea Galimberti Fabrizio De Mattia Alessia Losa Ilaria Bruni Silvia Federici Maurizio Casiraghi Stefano Martellos Massimo Labra 《Food research international (Ottawa, Ont.)》2013,50(1):55-63
Food safety and quality are nowadays a major concern. Any case of food alteration, especially when reported by the media, has a great impact on public opinion. There is an increasing demand for the improvement of quality controls, hence addressing scientific research towards the development of reliable molecular tools for food analysis. DNA barcoding is a widely used molecular-based system, which can identify biological specimens, and is used for the identification of both raw materials and processed food. In this review the results of several researches are critically analyzed, in order to exploit the effectiveness of DNA barcoding in food traceability, and to delineate some best practices in the application of DNA barcoding throughout the industrial pipeline. The use of DNA barcoding for food safety and in the identification of commercial fraud is also discussed. 相似文献
55.
Mercedes Álvarez Isabel M. Moreno Silvia Pichardo Ana M. Cameán A. Gustavo González 《Food chemistry》2012
Fifty wines from the Denomination of origin (DO) of Condado de Huelva were analysed for mineral content by measuring 12 elements (Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Samples were previously digested by heating with H2O2/HNO3 mixture. The results obtained showed that metal data set were non-normally distributed and accordingly, non-parametric statistics were applied. The average levels (medians) of these elements found in the samples are as follows, in mg/L: 2.54 (Al); 0.06 (Ba); 82.58 (Ca); 0.21 (Cu); 3.53 (Fe); 865.34 (K); 68.87 (Mg); 0.71 (Mn); 32.77 (Na); 71.61 (P); 0.48 (Sr); 0.56 (Zn). The interrelation of metal couples was studied through the Spearman non-parametric sample correlation, being Fe/Al, P/Mg, and Zn/Ba the most important correlations established. As a result of this study, we can suggest that the contribution to the safety intake limits (per week) of the studied elements through the wine consumption is not significant. Actually, they range between 0.1% in Fe and 11.9% in Mg, for normal drinkers. 相似文献
56.
Synthesis of Novel Niobium Aluminide-Based Composites 总被引:5,自引:0,他引:5
Daniel E. Garcia Silvia Schicker Jorn Bruhn Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1997,80(9):2248-2252
A reactive sintering process has been used to produce almost fully dense composites with interpenetrating networks of NbAl3 and Al2 O3 . The process involves the reaction synthesis of niobium aluminides and Al2 O3 from compacts of intensively milled aluminum and Nb2 O5 powder mixtures. During carefully controlled heating under an inert atmosphere, the oxide reduction by aluminum to form niobium aluminides and Al2 O3 proceeds at temperatures below the melting point of aluminum. At temperatures of >1000°C, the reaction-formed niobium aluminides and Al2 O3 sinter. The present paper discusses processing parameters, such as attrition milling, the heating cycle, and the metal:ceramic ratio in the starting mixture, that control microstructure development and mechanical properties. 相似文献
57.
Silvia Gomez Joop A. Peters Jan C. van der Waal Wuzong Zhou Thomas Maschmeyer 《Catalysis Letters》2002,82(1-2):1-5
Platinum particles (<1.5 nm) have been shown to behave as bases in their interaction with -alumina. FTIR spectra of adsorbed pyridine probe molecules showed that the acid strength of the -alumina was decreased by the presence of (<1.5 nm) Pt particles. Ammonium chloride treatment converts the primary Pt clusters to H
x
Pt
y
Cl
z
intermediates that de-anchor from the support. Consequently, agglomeration to 8 nm Pt particles was observed following treatment in hydrogen at a relatively mild temperature. For the treated catalyst the IR data of absorbed pyridine show a 3 cm-1 increase relative to the original Pt/-Al2O3 catalyst, indicating a strengthening of the acidity. Changes in the Pt particle size were confirmed by FTIR spectroscopy of CO absorbed onto the Pt particles before and after treatment. Consecutive CO and pyridine probe adsorption demonstrated the electronic interplay between the Pt particles and the support. Pyridine adsorption onto the -alumina support of a Pt/Al2O3 catalyst pre-dosed with CO produces a nearly 40 cm-1 lowering of the CO peak position, indicative of CO bond weakening. In the case of CO adsorbed onto a catalyst pre-dosed with pyridine, a shift in the pyridine IR spectrum was only observed from the original highly dispersed catalyst. 相似文献
58.
Potent,Metabolically Stable 2‐Alkyl‐8‐(2H‐1,2,3‐triazol‐2‐yl)‐9H‐adenines as Adenosine A2A Receptor Ligands 下载免费PDF全文
Dr. Silvia Pace Dr. Giandomenico Brogin Dr. Maria Antonietta Stasi Dr. Teresa Riccioni Franco Borsini Dr. Francesca Capocasa Dr. Francesco Manera Carlo Tallarico Dr. Pietro Grossi Dr. Federica Vacondio Dr. Michele Bassi Dr. Francesca Bartoccini Dr. Simone Lucarini Dr. Giovanni Piersanti Prof. Giorgio Tarzia Walter Cabri Dr. Patrizia Minetti 《ChemMedChem》2015,10(7):1149-1152
Inhibition of adenosine A2A receptors has been shown to elicit a therapeutic response in preclinical animal models of Parkinson’s disease (PD). We previously identified the triazolo‐9H‐purine, ST1535, as a potent A2AR antagonist. Studies revealed that ST1535 is extensively hydroxylated at the ω‐1 position of the butyl side chain. Here, we describe the synthesis and evaluation of derivatives in which the ω‐1 position has been substituted (F, Me, OH) in order to block metabolism. The stability of the compounds was evaluated in human liver microsomes (HLM), and the affinity for A2AR was determined. Two compounds, (2‐(3,3‐dimethylbutyl)‐9‐methyl‐8‐(2H‐1,2,3‐triazol‐2‐yl)‐9H‐purin‐6‐amine ( 3 b ) and 4‐(6‐amino‐9‐methyl‐8‐(2H‐1,2,3‐triazol‐2‐yl)‐9H‐purin‐2‐yl)‐2‐methylbutan‐2‐ol ( 3 c ), exhibited good affinity against A2AR (Ki=0.4 nM and 2 nM , respectively) and high in vitro metabolic stability (89.5 % and 95.3 % recovery, respectively, after incubation with HLM for two hours). 相似文献
59.
Cristhiane Caroline Ferrari Silvia Pimentel Marconi Germer José Maurício de Aguirre 《Drying Technology》2013,31(2):154-163
The purpose of this work was to study the effects of spray-drying conditions on the physicochemical characteristics of blackberry powder using a central composite rotatable design. Inlet air temperature (140–180°C) and maltodextrin concentration (5–25%) were employed as independent variables. Moisture content, hygroscopicity, anthocyanin retention, color, powder morphology, and particle size were analyzed. A higher inlet air temperature significantly increased the hygroscopicity of the powder, decreased its moisture content, and led to the formation of larger particles with smooth surfaces. Powders produced with higher maltodextrin concentrations were less hygroscopic, slightly lighter and less red, and had a lower moisture content. Anthocyanin retention was mainly affected by drying temperature due to the heat sensitivity of the pigment. The optimal processing conditions were an inlet air temperature of 140–150°C and maltodextrin concentration of 5–7%. Overall, these results indicate that good quality powders can be obtained by spray drying, with potential applications for the food industry. 相似文献
60.
Giuseppe Spoto Silvia Bordiga Domenica Scarano Adriano Zecchina 《Catalysis Letters》1992,13(1-2):39-44
In this note an exchange procedure of the acidic protons of H-ZSM5 by CuI ions through reaction with CuCl in the gas phase is described. In the so obtained CuI-ZSM5 exchanged zeolite the CuI ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The CuI(NO)2 species are transformed at RT into CuII(NO)X (X=O– and/or NO
2
–
) species which could represent an intermediate in NO decomposition. 相似文献