全文获取类型
收费全文 | 2087篇 |
免费 | 67篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 51篇 |
综合类 | 2篇 |
化学工业 | 792篇 |
金属工艺 | 38篇 |
机械仪表 | 37篇 |
建筑科学 | 161篇 |
矿业工程 | 4篇 |
能源动力 | 70篇 |
轻工业 | 151篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 107篇 |
一般工业技术 | 235篇 |
冶金工业 | 189篇 |
原子能技术 | 11篇 |
自动化技术 | 304篇 |
出版年
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 25篇 |
2017年 | 17篇 |
2016年 | 49篇 |
2015年 | 53篇 |
2014年 | 73篇 |
2013年 | 76篇 |
2012年 | 93篇 |
2011年 | 106篇 |
2010年 | 70篇 |
2009年 | 88篇 |
2008年 | 93篇 |
2007年 | 81篇 |
2006年 | 92篇 |
2005年 | 79篇 |
2004年 | 82篇 |
2003年 | 57篇 |
2002年 | 54篇 |
2001年 | 41篇 |
2000年 | 49篇 |
1999年 | 48篇 |
1998年 | 48篇 |
1997年 | 47篇 |
1996年 | 39篇 |
1995年 | 28篇 |
1994年 | 44篇 |
1993年 | 39篇 |
1992年 | 37篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 30篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1983年 | 23篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 21篇 |
1973年 | 15篇 |
1972年 | 15篇 |
排序方式: 共有2157条查询结果,搜索用时 15 毫秒
71.
Frits van der Klis Jérôme Le Nôtre Rolf Blaauw Jacco van Haveren Daan S. van Es 《European Journal of Lipid Science and Technology》2012,114(8):911-918
A two‐step concept for the production of linear alpha olefins from biomass is reported. As a starting material an internally unsaturated C17 alkene was used, which was obtained by the decarboxylation of oleic acid. Here, we report on the ethenolysis of this bio‐based product, using commercially available metathesis catalysts. The desired alpha olefin products, 1‐nonene and 1‐decene, were obtained in excellent yield (96%) and selectivity (96%). Practical applications: The two‐step conversion described in this contribution, starting from unsaturated fatty acids, provides a method for the production of industrially important linear alpha olefins. These valuable products are widely used as starting materials for the production of surfactants and polymers such as linear low density polyethylene (LLDPE). 相似文献
72.
Rolf G. Kuehni 《Color research and application》2012,37(6):424-428
Unlike in the case of sound where there is a compressed but straightforward relationship between frequency of sound waves and the perceived pitch, in the case of color the relationship is highly nonlinear, as first pointed out by Ostwald in 1916. In this article, the relationship between the perceptual Munsell hue scale and the related dominant wavelengths of the color chips involved is investigated. A hypothesis is proposed according to which the immediate cause of the nonlinearity can be found in the relative activation of the kinds of chromatically opponent functions shown to exist in neurons of the lateral geniculate nuclei. However, at this time, the relationship is only correlational, given the lack of deeper understanding of the relationship between the physiological operation of the color vision system and conscious experiences of color. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011; 相似文献
73.
The scratch behavior of butyl-acrylate rubber-modified styrene-acrylonitrile (ASA) upon high temperature annealing is investigated following the ASTM D7027/ISO 19252 linearly increasing normal load test methodology. The critical normal loads at the onset of the major deformation transitions along the scratch path, such as groove formation, scratch visibility, microcrack formation, and plowing, are reported and quantitatively analyzed. It is found that the scratch resistance improves with high temperature annealing, i.e., 30 °C above Tg, as compared to annealing below or around Tg. Microscopic investigation suggests that the increase in scratch resistance is related to the changes in surface morphology of the polymer. It is concluded that performing high temperature annealing enhances the scratch performance without compromising ASA bulk properties. Implication of the present study for improving scratch resistance of polymers is discussed. 相似文献
74.
Graphenated Ceramic Particles as Functional Fillers for Nonisocyanate Polyhydroxyurethane Composites
Graphenation of corundum and silicon carbide filler particles simultaneously improves mechanical properties and electrical conductivity of nonisocyanate polyhydroxyurethanes (NIPU) composites prepared by amine cure of polyfunctional cyclic carbonates. Typically, the ceramic fillers coated with either glucose, polydopamine, or graphite oxide (GO) are thermolyzed to produce an ultrathin graphene shell around the ceramic core, as verified by transmission electron microscopy. As compared to a blend of corundum particles with the thermally reduced graphite oxide (TRGO) nanofiller, graphenation of corundum with GO at a similar total carbon content significantly improves the Young’s modulus (7000 MPa, +184%) of trimethylolpropane glycidylether carbonate (TMPGC) cured with diethylenetriamine (DETA). Moreover, up to 30 wt% of the graphenated corundum filler is uniformly dispersed, whereas a few percent of neat TRGO account for intolerable high viscosity. Furthermore, NIPU composites containing graphenated ceramic fillers exhibit electrical conductivities of up 2.58 × 10?5 S m?1 well below the percolation threshold of neat TRGO in the same NIPU matrix. Hence, the graphenation of inorganic particles represents a facile and universal synthetic route toward tailoring functional fillers and combines the two worlds of functionalized graphene and inorganic fillers in an economic way by eliminating the tedious syntheses and handling typical for graphene nanofillers. 相似文献
75.
X Bian F Huang FA Stewart L Xia Y Zhang R Müller 《Chembiochem : a European journal of chemical biology》2012,13(13):1946-1952
The reconstruction of a natural product biosynthetic pathway from bacteria in a vector and subsequent heterologous expression in a technically amenable microbial system represents an efficient alternative to empirical traditional methods for functional discovery, yield improvement, and genetic engineering to produce "unnatural" derivatives. However, the traditional cloning procedure based on genomic library construction and screening are complicated due to the large size (>10 kb) of most biosynthetic pathways. Here, we describe the direct cloning of a partial syringolin biosynthetic gene cluster (sylCDE, 19 kb) from a digested genomic DNA mixture of Pseudomonas syringae into a plasmid in which sylCDE is under the control of an inducible promoter by one step linear-plus-linear homologous recombination (LLHR) in Escherichia coli. After expression in E. coli GB05-MtaA, two new syringolin derivatives were discovered. The complete syringolin gene cluster was assembled by addition of sylAB and exchange of a synthetic bidirectional promoter against the native promoter to drive sylB and sylC expression by using Red/ET recombineering. The varying production distribution of syringolin derivatives showed the different efficiencies of native and synthetic promoters in E. coli. The successful reconstitution and expression of the syringolin biosynthetic pathway shows that Red/ET recombineering is an efficient tool to clone and engineer secondary metabolite biosynthetic pathways. 相似文献
76.
77.
Ressler Thorsten Wienold Julia Jentoft Rolf E. Neisius Thomas Günter Marco M. 《Topics in Catalysis》2002,18(1-2):45-52
The potentials of X-ray absorption spectroscopy (XAS) (quantitative phase composition and average valence together with a short-range order structure analysis) combined with a time-resolution in the second range make time-resolved (TR-) XAS a powerful tool for investigating the reactivity of solids in catalysis and solid-state chemistry. General aspects of TR-XAS investigations are discussed (i.e., instrumentation, data analysis). In addition, some experiments illustrate how the kinetics of solid-state reactions in heterogeneous catalysis can be elucidated from TR-XAS studies. 相似文献
78.
79.
80.
RolfW.Hertling 《光盘技术》2003,(4):42-46
1引言:高级的可录DVD格式需要高级的测试设备 放眼当今市场,终端消费者已逐步接受可录DVD格式;展望不久的将来,可录DVD必将取代CD-R成为数据备份的标准存储媒体。因而盘片复制商、生产线制造商、测试设备提供商都越来越关注DVD-R。 相似文献