全文获取类型
收费全文 | 7054篇 |
免费 | 259篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 110篇 |
综合类 | 32篇 |
化学工业 | 1779篇 |
金属工艺 | 126篇 |
机械仪表 | 135篇 |
建筑科学 | 385篇 |
矿业工程 | 30篇 |
能源动力 | 126篇 |
轻工业 | 564篇 |
水利工程 | 43篇 |
石油天然气 | 2篇 |
无线电 | 569篇 |
一般工业技术 | 1370篇 |
冶金工业 | 1089篇 |
原子能技术 | 60篇 |
自动化技术 | 907篇 |
出版年
2023年 | 54篇 |
2022年 | 71篇 |
2021年 | 115篇 |
2020年 | 91篇 |
2019年 | 86篇 |
2018年 | 107篇 |
2017年 | 123篇 |
2016年 | 174篇 |
2015年 | 138篇 |
2014年 | 194篇 |
2013年 | 316篇 |
2012年 | 277篇 |
2011年 | 392篇 |
2010年 | 306篇 |
2009年 | 308篇 |
2008年 | 312篇 |
2007年 | 293篇 |
2006年 | 279篇 |
2005年 | 258篇 |
2004年 | 202篇 |
2003年 | 161篇 |
2002年 | 149篇 |
2001年 | 127篇 |
2000年 | 116篇 |
1999年 | 142篇 |
1998年 | 265篇 |
1997年 | 189篇 |
1996年 | 169篇 |
1995年 | 118篇 |
1994年 | 116篇 |
1993年 | 117篇 |
1992年 | 101篇 |
1991年 | 80篇 |
1990年 | 94篇 |
1989年 | 93篇 |
1988年 | 85篇 |
1987年 | 75篇 |
1986年 | 63篇 |
1985年 | 64篇 |
1984年 | 68篇 |
1983年 | 55篇 |
1982年 | 59篇 |
1981年 | 64篇 |
1980年 | 42篇 |
1979年 | 45篇 |
1978年 | 55篇 |
1977年 | 45篇 |
1976年 | 59篇 |
1975年 | 44篇 |
1973年 | 41篇 |
排序方式: 共有7327条查询结果,搜索用时 31 毫秒
101.
Sascha Stanic Thomas Koch Klaus Schmid Simone Knaus Vasiliki-Maria Archodoulaki 《应用聚合物科学杂志》2021,138(28):50659
The influence of two peroxides (peroxydicarbonate/dilauroyl peroxide) with various concentrations (10–200 mmol/kg PP) and their effective opportunity to introduce long chain branched (LCB) were investigated. The dependence of a single and double extrusion step and the changes of the properties were studied. Experiments were carried out in a single screw extruder at 180°C for the first extrusion step (modification) and at 240°C for the second extrusion step (processing simulation). Melt flow rate and dynamic rheological properties were studied at a measuring temperature of 230°C. For the definitive determination of long chain branched polypropylene (LCB-PP) served the extensional rheology measurements. The mechanical properties were examined via tensile test and impact tensile test. Summarized, LCB (melt strength) could be observed via extensional rheology for all modified specimens and the mechanical properties were maintained or even improved for the modified samples. Particularly, samples containing dilauroyl peroxide display excellent mechanical properties in this study. 相似文献
102.
Chaudry Oliver Friedberger Andreas Grimm Alexandra Uder Michael Nagel Armin Michael Kemmler Wolfgang Engelke Klaus 《Magma (New York, N.Y.)》2021,34(3):367-376
Magnetic Resonance Materials in Physics, Biology and Medicine - To develop a precise semi-automated segmentation of the fascia lata (FL) of the thigh to quantify IMAT volume in T1w MR images and... 相似文献
103.
Wolfgang Tillmann Matthias Manka Lukas Wojarski Michael Holewa 《Science & Technology of Welding & Joining》2020,25(4):290-296
ABSTRACTTools for machining are exposed to high loads, wear, and elevated temperatures. Commonly, such tools consist of cemented carbides and tool steel. To combine the advantages of both materials, high-quality-joints with high strengths are desired. When brazing these materials, the main challenge is the mismatch of the Coefficient of Thermal Expansion (CTE) and the poor wettability of cemented carbides by molten filler alloys. In this regard, the feasibility of two custom-made alloys (CuNi12Si5, CuNi12Si5B0.4) was analysed. Besides being a cost-efficient alternative, these alloys offer the possibility to modify their mechanical properties by precipitation hardening to reduce stresses within the final joints. Thus, this paper shows that a temperature of 1060°C is suitable for wetting and brazing tests on different substrates. 相似文献
104.
Erika Leitel Wolfgang Hübner Karsten P. Thiessen Ju. B. Makari
ev A. G. Akimov 《工业材料与腐蚀》1988,39(1):1-7
Investigation into the passivation mechanism of iron in phosphate electrolytes on surfaces exposed to erosive attack On iron electrodes in neutral phosphate electrolytes by continuous solid particle impingement a reaction layer is formed within the transition potential region under anodic polarization. XPS and AES investigations show that the reaction layer formed under impingement will be replaced by an oxide layer during the transition into the passive state under simultaneous decrease of the layer thickness. The active/passive transition in phosphate electrolytes may be attached to the equilibrium potential of the reaction . According to this thermodynamic interpretation of both the active/passive transition and the passive/active transition, respectively on iron in presence of phosphate ions may be described as the Fe(II)/Fe(III)-redox reaction with two solid phases, the iron(II)-phosphate phase and the iron(III)-oxide phase. The increase of the interfacial dynamic processes at the solid/liquid interface causes in consequence of the solid particle impingement that thermodynamic laws govern the course of reactions. 相似文献
105.
Jan Behmann Kathrin Hendriksen Ute Müller Wolfgang Büscher Lutz Plümer 《GeoInformatica》2016,20(4):693-714
Tracking the spatio-temporal activity is highly relevant for domains like security, health, and quality management. Since animal welfare became a topic in politics and legislation locomotion patterns of livestock have received increasing interest. In contrast to the monitoring of pedestrians cattle activity tracking poses special challenges to both sensors and data analysis. Interesting states are not directly observable by a single sensor. In addition, sensors must be accepted by cattle and need to be robust enough to cope with a rough environment. In this article, we introduce the novel combination of heart rate and positioning sensors. Attached to neck and chest they are less interfering than accelerometers at the ankles. Exploiting the potential of such combined sensor system that records locomotion and non-spatial information from the heart rate sensor however is challenging. We introduce a novel two level method for the activity tracking focused on the duration and sequence of activity states. We combine Support Vector Machine (SVM) with Conditional Random Field (CRF) and extend Conditional Random fields by an explicit representation of duration. The SVM characterizes local activity states, whereas the CRF addresses sequences of local states to sequences incorporating spatial and non-spatial contextual knowledge. This combination provides a reliable and comprehensive identification of defined activity patterns, as well as their chronology and durations, suitable for the integration in an activity data base. This data base is used to extract physiological parameters and promises insights into internal states such as fitness, well-being and stress. Interestingly we were able to demonstrate a significant correlation between resting pulse rate and the day of pregnancy. 相似文献
106.
L. Wieth K. Kelemen S. Braun R. Koch H.-J. Bauer H. P. Schuchmann 《Microfluidics and nanofluidics》2016,20(2):42
High-pressure homogenization is a widely used process in the food, pharmaceutical, and cosmetic industry for producing emulsions. Because of small dimensions and high velocities, the experimental and numerical investigation of such a process is challenging. Hence, the development of products is mostly based on trial and error. In this paper, simulations of a generic high-pressure homogenization process using the Lagrangian, mesh-free smoothed particle hydrodynamics (SPH) method are presented and compared to experimental findings using Micro-Particle Image Velocimetry (μ-PIV). The SPH code has been developed and validated with the scope of simulating technical relevant multi-phase problems (Höfler et al. 2012). The present simulations cover the investigation of two different dynamic viscosities of the dispersed phase as well as different droplet trajectories. The comparison between the simulations and the experiments focusses on the velocity distribution of the continuous phase and the droplet deformation and breakup. In both cases a qualitatively good agreement is observed, demonstrating the ability of our SPH implementation for simulating technical relevant two-phase flows. 相似文献
107.
108.
Sambasiva Rao Chinnamsetty Mike Espig Wolfgang Hackbusch 《Computing and Visualization in Science》2015,17(6):267-275
The computation of a six-dimensional density matrix is the crucial step for the evaluation of kinetic energy in electronic structure calculations. For molecules with heavy nuclei, one has to consider a very refined mesh in order to deal with the nuclear cusps. This leads to high computational time and needs huge memory for the computation of the density matrix. To reduce the computational complexity and avoid discretization errors in the approximation, we use mesh-free canonical tensor products in electronic structure calculations. In this paper, we approximate the six-dimensional density matrix in an efficient way and then compute the kinetic energy. Accuracy is examined by comparing our computed kinetic energy with the exact computation of the kinetic energy. 相似文献
109.
The goal of this research is to explore new interaction metaphors for augmented reality on mobile phones, i.e. applications where users look at the live image of the device’s video camera and 3D virtual objects enrich the scene that they see. Common interaction concepts for such applications are often limited to pure 2D pointing and clicking on the device’s touch screen. Such an interaction with virtual objects is not only restrictive but also difficult, for example, due to the small form factor. In this article, we investigate the potential of finger tracking for gesture-based interaction. We present two experiments evaluating canonical operations such as translation, rotation, and scaling of virtual objects with respect to performance (time and accuracy) and engagement (subjective user feedback). Our results indicate a high entertainment value, but low accuracy if objects are manipulated in midair, suggesting great possibilities for leisure applications but limited usage for serious tasks. 相似文献
110.