全文获取类型
收费全文 | 5029篇 |
免费 | 156篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 82篇 |
综合类 | 15篇 |
化学工业 | 1213篇 |
金属工艺 | 104篇 |
机械仪表 | 107篇 |
建筑科学 | 299篇 |
矿业工程 | 23篇 |
能源动力 | 100篇 |
轻工业 | 757篇 |
水利工程 | 21篇 |
石油天然气 | 4篇 |
无线电 | 439篇 |
一般工业技术 | 892篇 |
冶金工业 | 647篇 |
原子能技术 | 57篇 |
自动化技术 | 431篇 |
出版年
2021年 | 58篇 |
2020年 | 44篇 |
2019年 | 55篇 |
2018年 | 63篇 |
2017年 | 65篇 |
2016年 | 97篇 |
2015年 | 105篇 |
2014年 | 119篇 |
2013年 | 200篇 |
2012年 | 209篇 |
2011年 | 207篇 |
2010年 | 141篇 |
2009年 | 177篇 |
2008年 | 166篇 |
2007年 | 188篇 |
2006年 | 198篇 |
2005年 | 142篇 |
2004年 | 126篇 |
2003年 | 109篇 |
2002年 | 123篇 |
2001年 | 92篇 |
2000年 | 72篇 |
1999年 | 89篇 |
1998年 | 179篇 |
1997年 | 129篇 |
1996年 | 90篇 |
1995年 | 94篇 |
1994年 | 81篇 |
1993年 | 71篇 |
1992年 | 80篇 |
1991年 | 62篇 |
1990年 | 54篇 |
1989年 | 62篇 |
1988年 | 69篇 |
1987年 | 76篇 |
1986年 | 67篇 |
1985年 | 59篇 |
1984年 | 69篇 |
1983年 | 63篇 |
1982年 | 51篇 |
1981年 | 61篇 |
1980年 | 64篇 |
1979年 | 54篇 |
1978年 | 52篇 |
1977年 | 54篇 |
1976年 | 77篇 |
1975年 | 44篇 |
1974年 | 40篇 |
1973年 | 39篇 |
1971年 | 36篇 |
排序方式: 共有5191条查询结果,搜索用时 31 毫秒
81.
Multi‐dimensional data originate from many different sources and are relevant for many applications. One specific sub‐type of such data is continuous trajectory data in multi‐dimensional state spaces of complex systems. We adapt the concept of spatially continuous scatterplots and spatially continuous parallel coordinate plots to such trajectory data, leading to continuous‐time scatterplots and continuous‐time parallel coordinates. Together with a temporal heat map representation, we design coordinated views for visual analysis and interactive exploration. We demonstrate the usefulness of our visualization approach for three case studies that cover examples of complex dynamic systems: cyber‐physical systems consisting of heterogeneous sensors and actuators networks (the collection of time‐dependent sensor network data of an exemplary smart home environment), the dynamics of robot arm movement and motion characteristics of humanoids. 相似文献
82.
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.
83.
The presented study describes the processes and mechanisms of batch fluidized bed drying. The influencing factors of hot air drying are theoretically and experimentally examined, in order to present the relations between temperature and humidity profiles and all other drying parameters. A physical model is presented to facilitate the calculation of the drying processes under defined conditions. Three succeeding drying stages are therefore modeled. Mass and energy balances including all components taking part in the process are formulated. The model clarities the drying process under the assumption of pure heat transfer mechanisms. It does not contain adaptive parameters and takes into account an inactive bypass fraction of the fluidization and drying medium. The evaluation of the model was successful for two fluidized bed plants with nominal widths of 100 mm and 400 mm. The experiments showed sufficient accuracy and transferability of the model to equipment of application‐oriented dimensions. 相似文献
84.
Werner Interthal 《大分子材料与工程》1984,123(1):387-417
Soluble high polymers drastically reduce the friction or drag of turbulent wall flows; this effect is widely known as drag reduction. In practical applications drag reducing polymers also bring about an increase in flow rate. That is why we have introduced the term flow enhancer for this type of polymer. Drag reduction by polymers was discovered in 1948. The addition of very small amounts (ppm) of a high polymer reduces the pressure drop in turbulent pipe flow by up to 80 % or increases the flow rate by up to 100 %. These rheological effects are demonstrated with the aid of laboratory experiments. A physical model is presented which describes the interference of the coiled macromolecule in turbulent boundary layers with elongational velocity gradients. From this theory are derived a number of requirements for particularly effective macromolecules, such as molar mass, conformation, linearity and electrical charges in the molecule. The well-known water soluble drag reducing polymers are presented and the influence of pH, electrolytes and temperature described. Finally a survey of practical applications with experiments describing the operation of a specially designed flow enhancer for hydrotransport of sand slurries is given. 相似文献
85.
Ashraf El-Sayed Josef Gödde Peter Witzgall Heinrich Arn 《Journal of chemical ecology》1999,25(2):389-400
The behavioral responses of Lobesia botrana males to calling females, pheromone gland extracts, and synthetic sex pheromones were recorded in a wind tunnel. Gland extracts and synthetic pheromones were released from a pheromone evaporator. The numbers of males reaching the source and their flight tracks in response to calling females and pheromone gland extracts were compared to those of synthetic blends. Upwind flights to natural sex pheromone were straighter and faster than to a three-component blend of (E)-7,(Z)-9-dodecadienyl acetate (E7,Z9–12:Ac), (E)-7,(Z)-9-dodecadien-1-ol (E7,Z9–12:OH), and (Z)-9-docecenyl acetate (Z9–12:Ac) (100:20:5). The optimum ratio of E7,Z9–12:OH and Z9–12:Ac to E7,Z9–12:Ac was found to be 5% and 1%, respectively. An additional seven compounds identified in the sex pheromone gland were investigated for their biological activity. Two unsaturated acetates, i.e., (E)-9-dodecenyl acetate (E9–12:Ac) and 11-dodecenyl acetate (11–12:Ac), increased the number of males reaching the source as well as straightness, linear velocity, and decreased the track angle of upwind flight. Optimum response was obtained by releasing 10 pg/min E7,Z9–12:Ac in a mixture with 0.5 pg/min E7,Z9–12:OH, 0.1 pg/min Z9–12:Ac, 0.1 pg/min E9– 12:Ac and 1 pg/min 11-12–Ac. The saturated acetates previously identified in the female glands were biologically inactive. 相似文献
86.
Werner Lohwasser Maximilian Fleischer Josef Gerblinger Hans Meixner 《Journal of the American Ceramic Society》1994,77(7):1969-1972
Simultaneous Hall and conductivity measurements have been performed on sputtered polycrystalline thin films and on bulk ceramic specimens of nearly stoichiometric CeO2 in the temperature range between 900° and 1040°C. The measurements have been performed in air using low-frequency alternating current. In the case of the bulk ceramic specimens, an upper limit for the carrier mobility of ≤0.2 cm2 /(V·s) has been obtained, which is in accordance with data from the literature for bulk samples. The conductivity of the thin films (l/1Ω·m) at 1000°C) is in accordance with data from the literature for bulk ceramics. The carrier density derived from the Hall measurements (3 × 1016 /cm3 at 1000°C) increases with increasing temperature, whereas the Hall mobility (4 cm2 (V·s) at 1000°C) decreases with increasing temperature. These values differ from literature data for bulk ceramic specimens. The difference may be duelo the small grain diameters (∼200 nm) in the 1-μm-thick thin films. 相似文献
87.
Chinmoy Saha Siva Ponnupandian Francis R. Costa Gert Heinrich Nikhil K. Singha 《Polymer Engineering and Science》2021,61(12):3163-3169
This investigation reports the synthesis of a new class of polyurethane (PU) based on bis(hydroxyalkyl) polydimethylsiloxane (PDMS) as diol and isophorone diisocyanate as diisocyanate followed by the preparation of PU/layered double hydroxide (PU/LDH) nanocomposite via ex-situ technique. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy studies confirm the formation of PU and incorporation of PDMS into the PU backbone. Thermogravimetry analysis revealed that thermal stability of the composite improves significantly with incorporation of LDH into the PU matrix. This may be accredited to the barrier effect rendered by the LDH layers. Differential scanning calorimetry study reveals that with the incorporation of LDH, glass transition temperature (Tg) of the composite increases for an optimum level of loading beyond which it remains constant. 相似文献
88.
Surface reconstruction for incremental forming 总被引:1,自引:0,他引:1
A. Erman Tekkaya Ravi Shankar Gerd Sebastiani Werner Homberg Matthias Kleiner 《Production Engineering》2007,1(1):71-78
In spite of extensive efforts being made with regard to virtual process optimization technology, the production of prototype
parts is still a necessity. With respect to the production of sheet metal parts in low quantities, incremental sheet metal
forming (ISMF) is a highly interesting process. ISMF allows the production of complex parts with drastically reduced costs
in tooling and machinery compared to conventional processes like deep drawing. However, ISMF, with it’s incremental nature,
introduces the need for generating a tool path considering both final geometry and process-induced deviations or constraints.
Consequently, for the generation of the tool path a (tool path) surface, with an adequate offset, is necessary. That is why,
within the scope of extensive research work at the Institute of Forming Technology and Lightweight Construction (IUL), a special
correction module has been developed, determining this offset e.g. depending on the workpiece geometry. This paper presents
the algorithm, the application, and the effect on the produced parts. Furthermore, a concept for an extension regarding further
constraints like elastic workpiece behavior is presented. 相似文献
89.
90.