全文获取类型
收费全文 | 1837篇 |
免费 | 90篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 24篇 |
综合类 | 16篇 |
化学工业 | 564篇 |
金属工艺 | 30篇 |
机械仪表 | 31篇 |
建筑科学 | 138篇 |
矿业工程 | 3篇 |
能源动力 | 27篇 |
轻工业 | 169篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 116篇 |
一般工业技术 | 373篇 |
冶金工业 | 65篇 |
原子能技术 | 16篇 |
自动化技术 | 346篇 |
出版年
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 65篇 |
2020年 | 36篇 |
2019年 | 46篇 |
2018年 | 43篇 |
2017年 | 41篇 |
2016年 | 51篇 |
2015年 | 47篇 |
2014年 | 73篇 |
2013年 | 97篇 |
2012年 | 89篇 |
2011年 | 157篇 |
2010年 | 99篇 |
2009年 | 111篇 |
2008年 | 102篇 |
2007年 | 84篇 |
2006年 | 85篇 |
2005年 | 73篇 |
2004年 | 68篇 |
2003年 | 53篇 |
2002年 | 51篇 |
2001年 | 44篇 |
2000年 | 42篇 |
1999年 | 41篇 |
1998年 | 27篇 |
1997年 | 27篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1967年 | 2篇 |
1939年 | 1篇 |
1931年 | 3篇 |
排序方式: 共有1932条查询结果,搜索用时 15 毫秒
71.
Markus Feulner Gunter Hagen Andreas Piontkowski Andreas Müller Gerhard Fischerauer Dieter Brüggemann Ralf Moos 《Topics in Catalysis》2013,56(1-8):483-488
Diesel particulate filters (DPF) are indispensable parts of modern automotive exhaust gas aftertreatment systems due to the stringent emissions legislation. For a fuel-efficient control strategy, it would be beneficial to determine directly and in-operation their actual trapped soot mass. Two novel approaches—based on the electrical conductivity of trapped soot particles—emerged recently. By measuring the electrical resistance between different single walls inside the filter, the soot load is determined with local resolution. The microwave-based technique is a contactless approach that gives an integral value depending on the soot mass in the DPF. We present investigations on loading and regeneration of DPFs in a dynamometer test bench applying both methods. The results are compared with each other and correlated with the differential pressure and the soot mass. Especially the microwave-based technique has a potential for serial application. 相似文献
72.
Elastomer materials are used in a wide application range and subjected to different loading from which failure of the material results. Because this failure is caused by initiation and propagation of cracks, the application of fracture mechanics methods for the assessment of the material is obvious. A short summary of the methods of technical fracture mechanics including possibilities of determination of crack resistance curves is given. Vulcanizates on the basis of SBR 1500 with various sulfur and carbon black contents were investigated. For describing the crack initiation and crack propagation behavior, several fracture mechanics examination methods were applied. Tear‐analyzer results were used to assess the crack propagation behavior under fatigue‐like loading conditions. Furthermore, for the characterization of the crack resistance of the materials under impact‐like loading conditions, instrumented tensile‐impact tests were performed. To obtain information about the initiation and propagation of a stable crack, quasi‐static fracture mechanics tests were applied. The results of the several tests are discussed in dependence on sulfur and carbon black contents. We found a non‐monotonous behavior of the toughness as a function of carbon black loading. An explanation is given in connection with a percolation‐like transition in filler morphology on larger length scales.
73.
Andrea Zocca Cynthia M. Gomes Enrico Bernardo Ralf Müller Jens Günster Paolo Colombo 《Journal of the European Ceramic Society》2013,33(9):1525-1533
Highly porous (>60% open porosity) glass–ceramic scaffolds with remarkable mechanical properties (compression strength of ~15 MPa) were produced by indirect 3D printing. Precursor glass powders were printed into 3D ordered structures and then heat treated to sinter and develop crystalline phases. The final glass–ceramic contained a β-spodumene solid solution together with a secondary phase of lithium disilicate.The precision of the printed geometry and the density of the struts in the scaffold depended on several processing parameters (e.g. powder size and flowability, layer thickness) and were improved by increasing the binder saturation and drying time. Two types of powders with different particle size distribution (PSD) and flowability were used. Powders with a larger PSD, could be processed within a wider range of printing parameters due to their good flowability; however, the printing precision and the struts density were lower compared to the scaffolds printed using the powder in a smaller average PSD. 相似文献
74.
Identification and Structure–Activity Relationship Studies of Small‐Molecule Inhibitors of the Methyllysine Reader Protein Spindlin1 下载免费PDF全文
Dr. Dina Robaa Dr. Tobias Wagner Chiara Luise Dr. Luca Carlino Joel McMillan Dr. Ralf Flaig Prof. Dr. Roland Schüle Prof. Dr. Manfred Jung Prof. Dr. Wolfgang Sippl 《ChemMedChem》2016,11(20):2327-2338
The methyllysine reader protein Spindlin1 has been implicated in the tumorigenesis of several types of cancer and may be an attractive novel therapeutic target. Small‐molecule inhibitors of Spindlin1 should be valuable as chemical probes as well as potential new therapeutics. We applied an iterative virtual screening campaign, encompassing structure‐ and ligand‐based approaches, to identify potential Spindlin1 inhibitors from databases of commercially available compounds. Our in silico studies coupled with in vitro testing were successful in identifying novel Spindlin1 inhibitors. Several 4‐aminoquinazoline and quinazolinethione derivatives were among the active hit compounds, which indicated that these scaffolds represent promising lead structures for the development of Spindlin1 inhibitors. Subsequent lead optimization studies were hence carried out, and numerous derivatives of both lead scaffolds were synthesized. This resulted in the discovery of novel inhibitors of Spindlin1 and helped explore the structure–activity relationships of these inhibitor series. 相似文献
75.
Hamza Messaoudi Fabian Thiemicke Claas Falldorf Ralf B. Bergmann Frank Vollertsen 《Production Engineering》2017,11(3):365-371
Digital micromirror devices (DMD) are increasingly used in laser-based manufacturing for a maskless beam shaping in order to realize simultaneous 2D/3D material processing. Thereby, the DMD has to be irradiated under a sharp angle to achieve acceptable projection quality with negligible distortion phenomena. In this article, we present a novel setup for DMD-based laser material processing. It enables the irradiation under large angles (up to 60\(^{\circ }\)), the reduction of optical elements as well as machine size. Occurring optical distortions during the amplitude-based laser beam shaping are characterized. To eliminate these phenomena, we implement an optical modelling of the DMD patterns, taking into account the propagation through the tilted interfaces. The resulting imaging of different desired shapes is verified experimentally for its geometrical properties such as length, radius and aspect ratio. Thereby, an angle-dependent correction and high shape accuracy of the image projection is shown. This novel arrangement may have applications in direct laser writing and photochemical machining. 相似文献
76.
Diana Linke Manfred Nimtz Ralf G. Berger Holger Zorn 《Journal of the American Oil Chemists' Society》2009,86(5):437-444
Two extracellular esterases were produced in submerged cultures of the basidiomycete Pleurotus sapidus. A foam fractionation device was designed and employed for the isolation of the esterolytic enzymes. The recovery of enzyme
activity in the liquefied foam strongly depended on the superficial gas velocity. High purification and enrichment factors
(E
a = 62.0, P = 15.5) were achieved using nitrogen at 1.87 cm min−1 within 100 min. Increasing the superficial gas velocity to 2.49 cm min−1 improved the recovery of total esterase activity in the foam to >95% at the expense of reduced enrichment and purification
factors. Differences in their physicochemical characteristics resulted in differing foaming properties of the two esterases
secreted by P. sapidus. By variation of the pH value of the culture medium and addition of Triton X-100, both esterases were successively and quantitatively
transferred into the foam in a two-step fractionation process. 相似文献
77.
Yong Men Hubert Gnaser Christiane Ziegler Ralf Zapf Volker Hessel Gunther Kolb 《Catalysis Letters》2005,105(1-2):35-40
Thermal desorption spectroscopy (TDS) under ultra high vacuum (UHV) condition has been used to investigate the desorption
characteristics of Cu/CeO2/γ-Al2O3 thin film catalysts coated onto the microchannel of a microreactor. TDS results demonstrate that surface desorption profiles
and chemical properties (acid–base and redox properties) are remarkably influenced by the catalyst composition, i.e. the loading
of copper and ceria. The enhanced basicity with the increase of ceria loading and the decrease of copper loading is evident
from the shifted desorption maximum of CO2 in TDS spectra. Three oxygen species, ranging from weakly bound oxygen desorbed at low temperature to the strongly held lattice
oxygen desorbed at high temperature, are easily discernible and clearly identified by O2 TDS spectra, depending on the catalyst compositions. The concomitant thermal desorption of O2, CO2, and H2O at low temperature indicates the unique chemical properties of copper/ceria catalyst with appropriate copper and ceria contents.
The observed low-temperature feature is ascribed to the role of porthole of copper/ceria interfacial area for several desorbed
species. The weakly bound oxygen species is attributed to the enhanced abundance of copper/ceria interfacial anionic vacancies
created by the intimate contact between copper and ceria entities and its impact on steam reforming of methanol (SRM) reaction
is tentatively discussed in terms of reverse oxygen spillover. 相似文献
78.
Claus RA Wüstholz A Müller S Bockmeyer CL Riedel NH Kinscherf R Deigner HP 《Chembiochem : a European journal of chemical biology》2005,6(4):726-737
The enantioselective synthesis of an analogue of scyphostatin, a potent inhibitor of the neutral sphingomyelinase, is described. The synthesis starts with cyclohexanone and a protected D-serine derivative. The key step is an asymmetric hydroxylation to access a hydroxycyclohexanone, which is transformed into a substituted hydroxycyclohexenone. This is converted into the scyphostatin analogue 14, a chemically and metabolically stabilised compound lacking the epoxy function of the natural congener and carrying a palmitic acid group instead of the native trienoyl residue. An evaluation of the biological activity of 14 revealed neutral sphingomyelinase inhibition in several in vivo test systems (monocytes, macrophages, hepatocytes) monitoring antiapoptotic effects and the inversion of phorbolester-induced translocation of green fluorescent protein labelled kinase (protein kinase C-alpha). 相似文献
79.
Alessandro Zampieri Andreas Dubbe Wilhelm Schwieger Abhijeet Avhale Ralf Moos 《Microporous and mesoporous materials》2008,111(1-3):530-535
ZSM-5 zeolite films were grown on Si substrates by a two-step hydrothermal synthesis consisting of in situ seeding and secondary crystal growth. The films were 8–13 μm thick and partly oriented with the c-axis perpendicular to the substrate surface. After ion exchange with sodium ions, one film was applied as solid electrolyte in a potentiometric hydrocarbon gas sensor. A fast and reversible voltage response of the sensor to varying propane concentrations (100 ppm – 10%) was observed in O2/CO2/N2 gas mixtures at 723 K. 相似文献
80.
Jan Rybnicek Ralf Lach Monika Lapcikova Josef Steidl Zdenek Krulis Wolfgang Grellmann Miroslav Slouf 《应用聚合物科学杂志》2008,109(5):3210-3223
Binary and ternary blends of PC, ABS, and PMMA were studied. The blends were produced from original and recycled materials by melt mixing in a wide range of compositions. Instrumented Charpy impact testing, tensile testing, rheology investigations, and electron microscopy were carried out to determine the relationship between the deformation and fracture behavior, blend composition, morphology, and processing parameters. Resistance against unstable crack propagation was evaluated using the concepts of J‐integral and crack‐tip‐opening displacement (CTOD). The transition from ductile elastic‐plastic to brittle‐linear elastic fracture behavior was observed in the case of PC/ABS/PMMA blend at 10% of PMMA. Reprocessing had only a slight influence on the deformation and fracture behavior of the recycled blends. The blends produced from recycled materials proved to be competitive with the original pure materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献