全文获取类型
收费全文 | 4049篇 |
免费 | 262篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 43篇 |
综合类 | 2篇 |
化学工业 | 1096篇 |
金属工艺 | 69篇 |
机械仪表 | 114篇 |
建筑科学 | 106篇 |
矿业工程 | 6篇 |
能源动力 | 192篇 |
轻工业 | 571篇 |
水利工程 | 34篇 |
石油天然气 | 14篇 |
无线电 | 273篇 |
一般工业技术 | 707篇 |
冶金工业 | 140篇 |
原子能技术 | 33篇 |
自动化技术 | 921篇 |
出版年
2024年 | 8篇 |
2023年 | 67篇 |
2022年 | 172篇 |
2021年 | 203篇 |
2020年 | 142篇 |
2019年 | 139篇 |
2018年 | 161篇 |
2017年 | 157篇 |
2016年 | 187篇 |
2015年 | 129篇 |
2014年 | 204篇 |
2013年 | 313篇 |
2012年 | 258篇 |
2011年 | 343篇 |
2010年 | 228篇 |
2009年 | 234篇 |
2008年 | 192篇 |
2007年 | 182篇 |
2006年 | 131篇 |
2005年 | 132篇 |
2004年 | 84篇 |
2003年 | 67篇 |
2002年 | 70篇 |
2001年 | 53篇 |
2000年 | 43篇 |
1999年 | 33篇 |
1998年 | 49篇 |
1997年 | 34篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有4321条查询结果,搜索用时 0 毫秒
11.
Federico Ferreres Alberto Ortiz Carmen Silva Christina Garcia-Viguera Francisco A. Tomás-Barberán Francisco Tomás-Lorente 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,194(2):139-143
Summary The flavonoids present in ten selected samples of La Alcarria honey with different pollen compositions have been HPLC analysed in order to establish if correlations between botanical origin and flavonoid profiles are possible. A common flavonoid pattern is observed in the different samples showing that pollen is not the main source of honey flavonoids. A close correlation between the flavonoid patterns of honey flavonoids and propolis flavonoids has been found suggesting that flavonoid analysis could be more useful in geographical origin determinations than in botanical origin studies.
Flavonoide des La-Alcarria-Honigs Eine Studie ihres botanischen Ursprungs
Zusammenfassung Die Flavonoide in Proben in Alcarria-Honig mit unterschiedlicher Pollenzusammensetzung wurden untersucht, um Kortrelationen zwischen dem botanischen Ursprung und den möglichen Flavonoiden zu finden. In den verschiedenen Proben wurde ein Flavonoid-Muster gefunden, wobei der Pollen nicht die Hauptquelle der Honigflavonoide ist. Es wurde jedoch eine enge Korrelation zwischen den Flavonoid-Mustern des Honigs und des Bienenkittharzes gefunden, was für die geographische Herkunft wichtiger ist als die botanische.相似文献
12.
María del Mar Noblejas-Lpez Mariona Baliu-Piqu Cristina Nieto-Jimnez Francisco J. Cimas Esther C. Morafraile Atanasio Pandiella ngel L. Corbi Balzs Gyrffy Alberto Ocaa 《International journal of molecular sciences》2021,22(8)
Targeting the innate immune system has attracted attention with the development of anti- CD47 antibodies. Anti-CD47 antibodies block the inhibition of the phagocytic activity of macrophages caused by the up-regulation of CD47 on tumor cells. In this study, public genomic data was used to identify genes highly expressed in breast tumors with elevated CD47 expression and analyzed the association between the presence of tumor immune infiltrates and the expression of the selected genes. We found that 142 genes positively correlated with CD47, of which 83 predicted favorable and 32 detrimental relapse-free survival (RFS). From those associated with favorable RFS, we selected the genes with immunologic biological functions and defined a CD47-immune signature composed of PTPRC, HLA-E, TGFBR2, PTGER4, ETS1, and OPTN. In the basal-like and HER2+ breast cancer subtypes, the expression of the CD47-immune signature predicted favorable outcome, correlated with the presence of tumor immune infiltrates, and with gene expression signatures of T cell activation. Moreover, CD47 up-regulated genes associated with favorable survival correlated with pro-tumoral macrophages. In summary, we described a CD47-immune gene signature composed of 6 genes associated with favorable prognosis, T cell activation, and pro-tumoral macrophages in breast cancer tumors expressing high levels of CD47. 相似文献
13.
Fernando Corvillo Laura Gonzlez-Snchez Alberto Lpez-Lera Emilia Arjona Giovanni Ceccarini Ferruccio Santini David Araújo-Vilar Rebecca J Brown Joan Villarroya Francesc Villarroya Santiago Rodríguez de Crdoba Teresa Caballero Pilar Nozal Margarita Lpez-Trascasa 《International journal of molecular sciences》2021,22(12)
14.
Canan Akay Neslihan Turan Duygu Karakış Luis Alberto Angurel 《International Journal of Applied Ceramic Technology》2021,18(1):51-59
Zirconia is a dental material that shows excellent biocompatibility and high strength in clinical applications. This study aims to evaluate the effects of ultrafast laser applications. The surface nanostructures were classified into three groups. Group 1 was generated using the burst mode, with three different distances between dots: 52 µm (Group 1a), 104 µm (Group 1b), and 156 µm (Group 1c). Group 2 was processed using the scanning mode configuration, with a set of parallel lines. Group 3 was also processed using this scanning configuration creating a set of square-shaped patterning. Group 4 was the control group. After the surface treatments, a pair of zirconia specimens was bonded end to end with resin cement. Flexural bond strength (FBS) test was applied in a universal test machine. Multiple comparisons were performed using a one-way analysis of variance and the Tukey's HSD test. All the samples that were treated with the laser showed higher FBS values than the untreated surface. Using the burst mode, preformed circular-shaped surface on an angle of 900 at 52 µm distance (Group 1a) showed the highest FBS values among all groups (p < .05). Groups 2 and 3 had significantly higher values than 1b and 1c. 相似文献
15.
Laura Prati Alberto Villa Francesca Porta Di Wang Dangsheng Su 《Catalysis Today》2007,122(3-4):386-390
The liquid phase oxidation of glycerol with oxygen has been studied using mono and bimetallic catalysts based on Au and Pd metals supported on activated carbon, in order to study the effect of the metal on the distribution of the products and on activity of catalysts. It was found that by using bimetallic catalysts (Au–Pd) a strong synergistic effect was shown. By using a preformed nucleating centre we were able to obtain a single alloyed phase, which allowed us to address the synergistic effect to the presence of alloyed Au/Pd. The advantage of using this latter catalyst lies not only in the high activity but also in a prolonged catalyst life. Although a partial leaching of palladium and assembling of the particles have been revealed by ICP and HRTEM respectively, activity after 10 re-cycles decreased less than expected (about 10%). 相似文献
16.
Alberto Ortiz Francisco Bonnin-Pascual Emilio Garcia-Fidalgo 《Journal of Intelligent and Robotic Systems》2014,76(1):151-167
Vessel maintenance entails periodic visual inspections of the internal and external parts of the hull in order to detect the typical defective situations affecting metallic structures, such as coating breakdown, corrosion, cracks, etc. The main goal of project MINOAS is the automation of the inspection process, currently undertaken by human surveyors, by means of a fleet of robotic agents. This paper overviews an approach to the inspection problem based on an autonomous Micro Aerial Vehicle (MAV) which, as part of this fleet, is in charge of regularly supplying images that can teleport the surveyor from a base station to the areas of the hull to be inspected. The control software approach adopted for the MAV is fully described, with a special emphasis on the self-localization capabilities of the vehicle. Experimental results showing the suitability of the platform to the application are as well reported and discussed. 相似文献
17.
Silphinene Sesquiterpenes as Model Insect Antifeedants 总被引:3,自引:0,他引:3
González-Coloma A Valencia F Martín N Hoffmann JJ Hutter L Marco JA Reina M 《Journal of chemical ecology》2002,28(1):117-129
Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11-acetoxy-5-angeloyloxysilphinen-3-one (1), 11-acetoxy-5-tigloyloxysilphinen-3-one (2), 11-acetoxy-5-iso- butyryloxysilphinen-3-one (3), 11-hydroxy-5-angeloyloxysilphinen-3-one (4), 11,5-dihydroxysilphinen-3-one (5), 11,5-diacetoxysilphinen-3-one (6), 5,11-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect. 相似文献
18.
Jeung Hee Lee Kerby C. Jones Thomas A. Foglia Alberto Nuñez Jong Ho Lee Yu Mi Kim Phuong-Lan Vu Ki-Teak Lee 《Journal of the American Oil Chemists' Society》2007,84(3):211-217
Using a 1,3-regioselective lipase as a catalyst, soybean oil and olive oil were interesterified with the short-chain triacylglycerol
tributyrin (1,2,3-tributyrylglycerol) to produce mixtures of structured triacylglycerols (SL-TAG). The SL-TAG were purified
by column chromatography and analyzed by both normal-phase (silica column; NPSIL) and reversed-phase [octadecyl silane (ODS) column] high-performance liquid chromatography (HPLC). Individual SL-TAG molecular
species were detected by evaporative light-scattering detection, and characterized by mass spectrometry. NPSIL HPLC successfully separated the newly synthesized SL-TAG into two groups of TAG: one composed of one butyryl group and two
long-chain fatty acyl groups (from soybean or olive oil); the second was composed of two butyryl groups and one long-chain
fatty acyl group. The SL-TAG species were further analyzed by reversed-phase HPLC which gave a more detailed separation of
the TAG species present in the two SL-TAG. 相似文献
19.
Helen L. Ngo Alberto Nuñez Wenbin Lin Thomas A. Foglia 《European Journal of Lipid Science and Technology》2007,109(3):214-224
Branched‐chain (bc) saturated fatty acids (SFA) have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids (UFA) and have better low‐temperature properties than linear SFA. Previous studies in converting UFA to bc‐FA using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting UFA to bc‐FA in higher yields and conversions. In this work, we examined the scope and potential of the zeolite‐catalyzed synthesis of bc‐FA starting from readily available monounsaturated linear FA. Our results show that common UFA such as oleic acid can be converted to bc‐isomers using modified Ferrierite zeolite catalysts with high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the FA chain were determined from the GC‐MS spectra of the picolinyl esters of the bc‐FA. 相似文献
20.
Victor T. Wyatt Alberto Nuñez Thomas A. Foglia William N. Marmer 《Journal of the American Oil Chemists' Society》2006,83(12):1033-1039
Novel oligomeric prepolymers were synthesized by acid-catalyzed condensation of glycerol with iminodiacetic, azelaic, or succinic
acid. The prepolymers were obtained, on average, in 62% yield and were characterized by 13C NMR, 1H NMR, matrix-assisted laser desorption ionization-time of flight-mass spectrometry, and gel permeation chromatography. The
synthesized oligomers had an average M.W. of 1543 Daltons (average polydispersity (PD)=1.34, average degree of polymerization
(DOP)=5.5). Hyperbranching was evident in the oligomers produced when using azelaic acid and succinic acid as co-monomers
with glycerol, whereas the reaction between iminodiacetic acid and glycerol resulted in linear products bearing cyclic urethane
structures. 相似文献