全文获取类型
收费全文 | 2632篇 |
免费 | 113篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 27篇 |
化学工业 | 424篇 |
金属工艺 | 38篇 |
机械仪表 | 26篇 |
建筑科学 | 74篇 |
矿业工程 | 12篇 |
能源动力 | 33篇 |
轻工业 | 753篇 |
水利工程 | 18篇 |
石油天然气 | 2篇 |
无线电 | 183篇 |
一般工业技术 | 470篇 |
冶金工业 | 294篇 |
原子能技术 | 6篇 |
自动化技术 | 392篇 |
出版年
2023年 | 21篇 |
2022年 | 16篇 |
2021年 | 47篇 |
2020年 | 32篇 |
2019年 | 31篇 |
2018年 | 56篇 |
2017年 | 61篇 |
2016年 | 101篇 |
2015年 | 71篇 |
2014年 | 90篇 |
2013年 | 155篇 |
2012年 | 138篇 |
2011年 | 122篇 |
2010年 | 120篇 |
2009年 | 110篇 |
2008年 | 136篇 |
2007年 | 107篇 |
2006年 | 91篇 |
2005年 | 64篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 60篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 96篇 |
1997年 | 54篇 |
1996年 | 54篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1976年 | 19篇 |
1937年 | 11篇 |
1936年 | 29篇 |
1935年 | 32篇 |
1934年 | 21篇 |
1933年 | 21篇 |
1932年 | 16篇 |
1931年 | 25篇 |
1930年 | 24篇 |
1929年 | 20篇 |
1928年 | 46篇 |
1927年 | 36篇 |
1926年 | 14篇 |
1925年 | 23篇 |
1915年 | 16篇 |
1913年 | 49篇 |
1912年 | 28篇 |
1907年 | 13篇 |
排序方式: 共有2752条查询结果,搜索用时 9 毫秒
81.
Synergistic effect of organoclay fillers based on fluorinated surfmers for preparation of polystyrene nanocomposites 下载免费PDF全文
Chahinez Benbayer Salima Saidi‐Besbes Elisabeth Taffin de Givenchy Sonia Amigoni Frédéric Guittard Aicha Derdour 《应用聚合物科学杂志》2015,132(33)
Novel fluorinated reactive surfactants were used for the organic modification of monmorillonite clays. These organoclays were used for the preparation of polystyrene?clay nanocomposites by in‐situ free radical polymerization. Reference systems based on hydrocarbon homologous surfmer and nonpolymerizable surfactants were also used to deduce the effect of the fluorine moiety and the polymerizable function on the morphology and thermal stability of the prepared nanocomposites. Different structural parameters of the surfactants were investigated and modulated for the clay modification including: the nature of surfactant (surfmer/classical surfactant, fluorinated, or hydrocarbonated), the length of the fluorinated chain as well as the length of the hydrocarbon spacers linking the ammonium head to the fluorine chain or the polymerizable acrylic function. Wide angle‐X‐ray scattering (WAXD), thermogravimetric analysis (TGA), and electronic microcopies (TEM and SEM) were used to establish a structure‐morphology, thermal properties relationships, and to highlight the key parameters governing the exfoliation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42347. 相似文献
82.
83.
Effects of antimicrobial agents on the thermal and mechanical properties of acrylate hydrogel matrices 下载免费PDF全文
Polymer materials with antimicrobial activity are prepared by UV polymerization of acrylate and methacrylate mixture at room temperature. The antimicrobials are silver acetate and copper (II) acetate, used without pretreatment. Their chemical stability in the acrylate matrix and their effect on the thermal and mechanical properties of the polymer matrix are investigated as a function of their concentration up to 15 wt %. Physico‐chemical, thermal, rheological, and morphological analyses as well as the surveillance of metal salts release in aqueous medium are conducted. A significant decrease in the thermal stability of the salts introduced into the acrylate matrix is observed after UV treatment. The metal salts also have significant effects on the properties of the matrix. A plasticization and densification of the material associated with an aggregation of salts up to the percolation at the highest concentration are highlighted. At equal concentrations, the effects are more pronounced in the presence of copper salts. The latter was released more slowly than silver salts from acrylate material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43501. 相似文献
84.
Efficient Engineering and Production Concepts for Products in Regulated Environments – Dream or Nightmare? 下载免费PDF全文
Prof. Jochen Strube Dr. Reinhard Ditz Holger Fröhlich Dr. Dirk Köster Dr. Thomas Grützner Dr. Jörg Koch Dr. Rüdiger Schütte 《化学,工程师,技术》2014,86(5):687-694
Manufacturing of chemical‐pharmaceutical products is moving increasingly fast on a global scale. Therefore, developing and starting up production facilities fast, with high quality, and at reasonable costs has become extremely challenging. Engineering concepts like modularization, standardization and simultaneous/parallel engineering are discussed as methods for speeding up process design and filing for regulatory approval. Transfer from batch to continuous operation mode of production is pointed out as the key‐issue in such strategies. 相似文献
85.
AbstractThe objective of this study was to compare spray-dried and freeze-dried extracts of Sennae fructus regarding the stability of the sennosides. Therefore, the influence of the addition of maltodextrin (MD) not only before the drying processes but also during fluidized bed granulation was investigated. Analysis of the hygroscopicities, the simultaneous TGA-DSC-MS data, and the influence of storage revealed that spray-dried extracts are more stable than freeze-dried extracts. The addition of MD led to an even better stability of the extracts. Lower amounts of MD are sufficient if applied onto the surface of the native extract during fluidized bed granulation. 相似文献
86.
Thomsen C Knutsen HK Liane VH Frøshaug M Kvalem HE Haugen M Meltzer HM Alexander J Becher G 《Molecular nutrition & food research》2008,52(2):228-237
Very high concentrations of polybrominated diphenyl ethers (PBDE) have been reported in fish from Lake Mj?sa in Norway. This study was performed to examine the serum concentrations of PBDE and hexabromocyclododecane (HBCD) in consumers of fish from this lake and to investigate possible relationships between serum concentrations, self-reported fish intake and calculated total dietary PBDE exposure. Serum concentrations of the sum of the seven PBDE (BDE-28, 47, 99, 100, 153, 154 and 183) were significantly higher than those of a reference group of Norwegians eating only food with background levels of contamination (medians: 18 ng/g lipids men, 8.4 ng/g lipids women). The median dietary intake of Sum 7 PBDE was 2549 ng/day (30 ng/kg body weight/day), the highest dietary intake of PBDE reported. The contribution from fish caught from the contaminated lake comprised 98.7% of the total dietary exposure. For men, serum levels of PBDE were strongly correlated with the calculated dietary exposure, except for BDE-209. This suggests that sources other than the diet are important for human BDE-209 exposure. The median serum HBCD concentration was 4.1 and 2.6 ng/g lipids for men and women, respectively, and was also found to be associated with consumption of fish from Lake Mj?sa. 相似文献
87.
88.
This contribution is concerned with the business value of Radio Frequency Identification (RFID) technology in retail. We present a case study of an RFID project at Galeria Kaufhof, a subsidiary of Metro Group and one of the largest department store chains in Europe. The project encompasses a variety of RFID applications at the intersection of store logistics and customer service. The contribution that our study makes to the literature is threefold. First, we describe an innovative large-scale trial that goes beyond what was done in earlier projects in several respects. The most fundamental difference from previous trials is the full integration of RFID event data with point-of-sale (POS) and master data, which for the first time offers the retailer the opportunity to directly observe and analyse physical in-store processes. Second, the heterogeneity of RFID applications implemented by Kaufhof allows us to theorise about the effects that RFID may have on business processes from an IT value perspective. We develop a conceptual model to explain the different cause-and-effect chains between RFID investments and their impact on firm performance, the role of complementary and contextual factors, and the difficulty of assessing these impacts using objective performance measures. Third, we compare the case to a prior trial conducted by Kaufhof about 5 years earlier. The differences between the lessons that the company learned in the two projects illustrate the impact of technological advances and standardisation efforts in recent years on managerial perceptions of RFID business value, which allows for the derivation of a number of useful implications for practice. 相似文献
89.
N. Grittner H. von Senden gen. Haverkamp Dipl.‐Ing. O. Stelling D. Bormann K. Schimanski M. Nikolaus A. von Hehl Fr.‐W. Bach H.‐W. Zoch 《Materialwissenschaft und Werkstofftechnik》2009,40(12):901-906
Rod Extrusion of Titanium‐Aluminum Composites The combination of different metals enables the processing of materials with local optimized properties. Thus, the production of metallic composites is associated with high standards in manufacturing technologie. Focus of the following investigations is the rod extrusion process of titanium‐aluminum‐composites. Besides the mechanical properties, the formation of the bonding zone and the mechanisms of adhesion in the bonding zone were investigated. The influence of specimens’ preparation and of different coatings used improve bonding were a matter of particular interest. Whereas coatings of copper or nickel inhibit the formation of a strong bonding due to the formation of oxide layers, sealed titanium cores can reach a mechanical strength of up to 100 MPa after rod extrusion. Compared to other joining technologies, an impairment of the base metal via formation of heat affected zones, pores or grain coarsening does not occur. 相似文献
90.
Joecila Santos da Silva Stéphane Calmant Frédérique Seyler Daniel Medeiros Moreira Daniel Oliveira Achiles Monteiro 《Water Resources Management》2014,28(3):587-603
The hydrological observation network in the Amazon basin is made of conventional rainfall and water level stations presently maintained by the Agência Nacional de Águas (ANA), the National Agency for Waters. The water level network has long been plagued by difficulties associated with spatial coverage, timely delivery and data errors. Satellite observations are important means for providing hydrologic data with acceptable spatial and temporal resolution, and radar altimeters embarked onboard successive satellites since the early 1970s collect measurements of water level over rivers in a well-defined geodetic reference frame and can be used to address some of these problems. Nowadays, satellite altimetry can be used to collect the time variations of the water levels over many rivers throughout the word, as long as the reach are several hundred meters wide. This ability is particularly interesting in ungauge basins but it can also be used as an independent source of information to cross-check existing gauge series. In the present study, we focus on examples from the Amazon basin where radar altimetry has been used to provide an independent dataset that can be used to support the management of hydrological observation networks by including new data together with conventional field data, 相似文献