全文获取类型
收费全文 | 2406篇 |
免费 | 142篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 1061篇 |
金属工艺 | 21篇 |
机械仪表 | 41篇 |
建筑科学 | 79篇 |
矿业工程 | 5篇 |
能源动力 | 47篇 |
轻工业 | 569篇 |
水利工程 | 17篇 |
石油天然气 | 7篇 |
无线电 | 86篇 |
一般工业技术 | 297篇 |
冶金工业 | 69篇 |
原子能技术 | 6篇 |
自动化技术 | 237篇 |
出版年
2024年 | 13篇 |
2023年 | 53篇 |
2022年 | 277篇 |
2021年 | 313篇 |
2020年 | 93篇 |
2019年 | 70篇 |
2018年 | 88篇 |
2017年 | 84篇 |
2016年 | 98篇 |
2015年 | 75篇 |
2014年 | 95篇 |
2013年 | 158篇 |
2012年 | 137篇 |
2011年 | 163篇 |
2010年 | 109篇 |
2009年 | 117篇 |
2008年 | 92篇 |
2007年 | 92篇 |
2006年 | 76篇 |
2005年 | 62篇 |
2004年 | 54篇 |
2003年 | 42篇 |
2002年 | 29篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1932年 | 2篇 |
排序方式: 共有2549条查询结果,搜索用时 46 毫秒
101.
Marta Bobiano Nuno Rodrigues Marta Madureira Luís G. Dias Ana C. A. Veloso José A. Pereira António M. Peres 《Journal of the American Oil Chemists' Society》2019,96(7):751-760
Olive oil price and consumers’ preference depend on the commercial grade classification that can decrease if any sensory defect is perceived leading to an economic loss. Enriched oils, obtained by incorporating dried aromatic herbs, spices, or essential oils, which is a common practice in the Mediterranean region, are commercially available. This practice may conceal the fraudulent purpose of masking the perception of sensory defects. The detection of this type of fraud is a difficult task, requiring sensory analysis. Thus, in this study, extra-virgin and lampante olive oils, the latter classification being due to the perception of an intense winey-vinegary defect, were deliberately enriched with different amounts of basil-dried herbs and oregano-dried herbs. Sensory analysis showed that, depending on the aromatic herb and on the added amount (0.011–0.110 g herb per kg oil), the defect intensity could be masked leading to an erroneous classification of flavored lampante oils as flavored virgin oils. In contrast, the electronic tongue-chemometric approach could unmask the defect in flavored oils (predictive sensitivities: 70–78%) and semiquantitatively discriminate flavored oils according to the added levels of basil or oregano (predictive sensitivities: 93–100%). The electronic tongue approach showed satisfactory unmasking performance when compared with the sensory panel, and so, its future application as a quality control taste-sensor device for disclosing olive oil sensory defects masked by the incorporation of flavoring agents may be forseen. 相似文献
102.
Dr. Eduarda Mendes Enrico Cadoni Filipa Carneiro Dr. Marta B. Afonso Hugo Brito Dr. João Lavrado Dr. Daniel J. V. A. dos Santos Dr. Jorge B. Vítor Prof. Stephen Neidle Prof. Cecília M. P. Rodrigues Prof. Alexandra Paulo 《ChemMedChem》2019,14(14):1325-1328
Quadruplex nucleic acids are promising targets for cancer therapy. In this study we used a fragment-based approach to create new flexible G-quadruplex (G4) DNA-interactive small molecules with good calculated oral drug-like properties, based on quinoline and triazole heterocycles. G4 melting temperature and polymerase chain reaction (PCR)-stop assays showed that two of these compounds are selective G4 ligands, as they were able to induce and stabilize G4s in a dose- and DNA sequence-dependent manner. Molecular docking studies have suggested plausible quadruplex binding to both the G-quartet and groove, with the quinoline module playing the major role. Compounds were screened for cytotoxicity against four cancer cell lines, where 4,4′-(4,4′-(1,3-phenylene)bis(1H-1,2,3-triazole-4,1-diyl))bis(1-methylquinolin-1-ium) ( 1 d ) showed the greater activity. Importantly, dose–response curves show that 1 d is cytotoxic in the human colon cancer HT-29 cell line enriched in cancer stem-like cells, a subpopulation of cells implicated in chemoresistance. Overall, this study identified a new small molecule as a promising lead for the development of drugs targeting G4 in cancer stem cells. 相似文献
103.
André Campaniço Dr. Marta P. Carrasco Dr. Mathew Njoroge Ronnett Seldon Prof. Kelly Chibale Dr. João Perdigão Prof. Isabel Portugal Prof. Digby F. Warner Prof. Rui Moreira Prof. Francisca Lopes 《ChemMedChem》2019,14(16):1537-1546
Herein we report the screening of a small library of aurones and their isosteric counterparts, azaaurones and N-acetylazaaurones, against Mycobacterium tuberculosis. Aurones were found to be inactive at 20 μm , whereas azaaurones and N-acetylazaaurones emerged as the most potent compounds, with nine derivatives displaying MIC99 values ranging from 0.4 to 2.0 μm . In addition, several N-acetylazaaurones were found to be active against multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical M. tuberculosis isolates. The antimycobacterial mechanism of action of these compounds remains to be determined; however, a preliminary mechanistic study confirmed that they do not inhibit the mycobacterial cytochrome bc1 complex. Additionally, microsomal metabolic stability and metabolite identification studies revealed that N-acetylazaaurones are deacetylated to their azaaurone counterparts. Overall, these results demonstrate that azaaurones and their N-acetyl counterparts represent a new entry in the toolbox of chemotypes capable of inhibiting M. tuberculosis growth. 相似文献
104.
Marta Lubary Theo W. de LoosJoop H. ter Horst Gerard W. Hofland 《The Journal of Supercritical Fluids》2011,55(3):1079-1088
The ScMM (Supercritical Melt Micronization) process was applied for the production of microparticles from anhydrous milk fat (AMF) and a diacylglycerol-based modified milk fat (D-AMF). Both fats were able to dissolve ca. 30 wt% CO2 in the studied pressure and temperature ranges, being the CO2 amount slightly higher for AMF. A melting point depression was observed in both systems in the presence of CO2. Two powder morphologies were obtained (spherical hollow particles and a mass sponge-like broken particles) depending on the ScMM process conditions. The concentration of CO2 in the fat melt was the main process variable affecting the particle morphology, followed by the temperature of the melt. The small broken particles originated from the breakage of spherical fat particles that solidified before all CO2 could escape from the atomized droplets. While the hollow spheres had a tendency to agglomerate, the broken microparticles constituted a free-flowing powder as long as they were stored at low temperatures (up to −18 °C). Both types of particles have a potential for being incorporated in refrigerated or frozen food products as a structuring agent. 相似文献
105.
106.
Chi P. Huynh Stephen C. Hawkins Marta Redrado Scott Barnes Deborah Lau William Humphries George P. Simon 《Carbon》2011,(6):1989-1997
Carbon nanotubes (CNTs) grown on substrate-bound catalysts by CVD are influenced by the catalyst, which changes over the course of the process. The evolution of the CNT growth is revealed by breaking the process into recycling increments and using the phenomenon of ‘direct spinnability’ as a target characteristic.Using acetylene alone, it was found that the first four cycles gave 100% regrowth in height and mass yield of CNTs, with both properties falling to around 20% on the 5th cycle. A decrease in nanotube diameter was observed whilst the areal density increased. With the addition of hydrogen a 100% regrowth for the second cycle was observed, followed by a decrease to around 55%, 18% and 11% in both height and yield for subsequent cycles. The diameter increased, whilst the areal density decreased in subsequent cycles.In the absence of hydrogen the CNTs have around seven walls, decreasing to about three by the seventh cycle. With hydrogen, CNTs have five or six walls for all cycles. Raman spectroscopy indicates an increase in disorder in later cycles. Spinnability is high for initial cycles but drops sharply on the fourth cycle, or third cycle with hydrogen, as the nanotube forest tortuosity markedly increases. 相似文献
107.
Carlos Moreno-Castilla Marta B. Dawidziuk Francisco Carrasco-Marín Zulamita Zapata-Benabithe 《Carbon》2011,49(12):3808-3819
Carbon aerogels were prepared by carbonizing (at 500–1500 °C) organic aerogels obtained from the polymerization reaction of resorcinol and/or pyrocatechol with formaldehyde using boric and oxalic acids as polymerization catalysts. Prepared samples were characterized by different techniques to ascertain their composition, surface chemistry, morphology, and surface physics, determining their electrochemical capacitances in acidic medium. The use of pyrocatechol yielded carbon aerogels that were micro–mesoporous, showing Type IV N2 adsorption isotherms with Type H2 hysteresis cycles. The volume and size of mesopores depended on the acid catalyst used and the temperature at which the carbon aerogel was obtained. Conversely, the sample prepared with resorcinol and boric acid as catalyst was micro–macroporous and that obtained with a resorcinol–pyrocatechol mixture was micro–mesoporous but with large mesopores. Most of the boric acid used was lost during the exchange of water with acetone in the organic hydrogels before their supercritical CO2 drying. Carbon aerogels obtained at 900 °C and using boric acid as polymerization catalyst showed a capacitance between 17 and 24 μF/cm2. Boron influenced the capacitance because it increased the oxygen content. Sample synthesized using pyrocatechol, formaldehyde, and oxalic acid and heat-treated at 900 °C had the highest capacitance, 34 μF/cm2. 相似文献
108.
Two different approaches to the creation of phosphorus‐containing soybean‐oil copolymers were investigated. First, two phosphorus‐containing styrene (ST) derivatives, diphenyl styryl phosphine oxide and dimethyl‐p‐vinylbenzylphosphonate (STP2), where tested as comonomers in the cationic copolymerization of soybean oil (SOY), ST, and divinylbenzene (DVB), to obtain heterogeneous systems in all cases. To overcome this drawback, the cross‐metathesis reaction of methyl 10‐undecenoate and STP2 was carried out to link the phosphorus moiety to the vegetable‐oil derivative. This second approach permitted the synthesis of a new reactive phosphorus‐containing plant‐oil derivative, which was incorporated into the soybean oil, ST, and DVB system. The cationic copolymerization was investigated, and the structure, thermal stability, and mechanical and flame‐retardant properties of the resulting copolymers were studied. Thermosets with moderate glass‐transition temperatures were obtained; this showed that the cross‐metathesis reaction is a convenient way to produce oil‐compatible monomers able to undergo homogeneous polymerization reactions. The resulting thermosets with 1% phosphorus had limiting oxygen index values about 24.0; this indicated an improvement in the fire‐retardant properties of the soybean‐oil‐based copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
109.
Marta Lubary Gerard W. Hofland Joop H. ter Horst 《European Journal of Lipid Science and Technology》2011,113(4):459-468
We propose a novel process for the production of a DAG‐rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties, derived from both its high content of DAG and of short‐chain fatty acids (FAs). The proposed process consists of three steps: lipase‐catalysed partial ethanolysis of milk fat, extraction of the by‐product fatty acid ethyl esters (FAEEs) using supercritical carbon dioxide (SC‐CO2) and isomerization of DAG to increase the proportion of 1,3‐DAG. The experimental investigation of the process steps was done using milk fat and trilaurin. Several lipases were tested for maximizing the percentage of DAG in the acylglycerol mixture produced by ethanolysis. The selectivity of the chosen lipase was such that the produced AG mixture was enriched in short‐chain FAs in relation to the original milk fat. FAEEs were completely extracted from the ethanolysis mixture by SC‐CO2. In the final process step, we explored the reaction conditions for facilitating acyl migration in the DAG mixture, so that the equilibrium proportion of 1,3‐DAG (~64%) was attained. Our results set the basis for the development of a simple process for the production of a DAG‐rich milk fat analogue. 相似文献
110.
Rahela Kulčar Mojca Friškovec Marta Klanjšek Gunde Nina Knešaurek 《Coloration Technology》2011,127(6):411-417
Leuco dye‐based thermochromic inks reversibly change from the coloured to the discoloured state in a defined, comparatively wide temperature region. Inside this region, the colour of a sample depends on the temperature and thermal history, which is known as the hysteresis effect. The colour of such a sample as a function of temperature has the shape of a hysteresis loop. Commercially available thermochromic inks have different loops, narrow or broad, and their shapes range from approximately symmetric to highly asymmetric. These properties are also important in mixtures of inks. The hysteresis loop of a mixture reveals its binary nature if the individual pure inks have well‐separated hysteresis. When inks with close‐separated loops, i.e. with similar activation temperatures, are mixed together, the loop of the mixture fuses together into an apparently single loop. Our research shows that some of their dynamic colour properties could be predicted in advance. However, optic and colorimetric properties of mixtures are not additive. 相似文献