全文获取类型
收费全文 | 26034篇 |
免费 | 2161篇 |
国内免费 | 1324篇 |
专业分类
电工技术 | 819篇 |
综合类 | 2847篇 |
化学工业 | 3207篇 |
金属工艺 | 4359篇 |
机械仪表 | 2541篇 |
建筑科学 | 2368篇 |
矿业工程 | 927篇 |
能源动力 | 661篇 |
轻工业 | 1268篇 |
水利工程 | 876篇 |
石油天然气 | 2084篇 |
武器工业 | 411篇 |
无线电 | 1443篇 |
一般工业技术 | 2567篇 |
冶金工业 | 1172篇 |
原子能技术 | 385篇 |
自动化技术 | 1584篇 |
出版年
2024年 | 86篇 |
2023年 | 279篇 |
2022年 | 488篇 |
2021年 | 593篇 |
2020年 | 646篇 |
2019年 | 526篇 |
2018年 | 525篇 |
2017年 | 811篇 |
2016年 | 888篇 |
2015年 | 1016篇 |
2014年 | 1565篇 |
2013年 | 1331篇 |
2012年 | 1891篇 |
2011年 | 2103篇 |
2010年 | 1651篇 |
2009年 | 1735篇 |
2008年 | 1452篇 |
2007年 | 1862篇 |
2006年 | 1798篇 |
2005年 | 1416篇 |
2004年 | 1278篇 |
2003年 | 1143篇 |
2002年 | 901篇 |
2001年 | 817篇 |
2000年 | 664篇 |
1999年 | 440篇 |
1998年 | 337篇 |
1997年 | 279篇 |
1996年 | 266篇 |
1995年 | 171篇 |
1994年 | 156篇 |
1993年 | 84篇 |
1992年 | 93篇 |
1991年 | 49篇 |
1990年 | 41篇 |
1989年 | 30篇 |
1988年 | 24篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1964年 | 4篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
This paper presents seasonal‐energy storage of solar energy for the heating of buildings. We distinguish several types of seasonal storage, such as latent, sensible, and chemical storage, among which the thermochemical storage is used and analysed in this research. In the first part, a laboratory heat‐storage tank, which was made in the laboratory for heating, sanitary, and solar technology and air conditioning from the Faculty of Mechanical Engineering, University of Ljubljana, Slovenia, was presented. The experimental model was tested for charging and discharging mode. Two types of numerical models for sorption thermal‐energy storage exist, which are microscale and macroscale (integral). For microscale analysis, the analysis system (ANSYS) model can be used to simulate the behaviour in the adsorption reactor. On macroscale or integral scale, TRaNsient SYStem (TRNSYS) model was used to perform the operation of the storages on the yearly basis. In the second part the simulation of the underfloor heating system operation with a built‐in storage tank was carried out for two locations, Ljubljana and Portoro?. Furthermore, the comparison between a thermochemical and sensible‐heat storage was performed with TRNSYS and Excel software. In this comparison, the focus was on the surface parameters of the SCs and volume of the thermal‐storage tank for the coverage of the energy demand for selected building. With this analysis, we would like to show the advantage of the thermochemical storage system, to provide greater coverage of the energy demand for the operation of the building, compared with the seasonal sensible‐heat storage (SSHS). Such a heat‐storage technology could, in the future, be a key contributor to the more environmentally friendly and more sustainable way of delivering energy needs for buildings. 相似文献
993.
José M. León Blanco Pedro L. González-R Carmen Martina Arroyo García María José Cózar-Bernal Marcos Calle Suárez David Canca Ortiz 《Drug development and industrial pharmacy》2018,44(1):135-143
This work was aimed at determining the feasibility of artificial neural networks (ANN) by implementing backpropagation algorithms with default settings to generate better predictive models than multiple linear regression (MLR) analysis. The study was hypothesized on timolol-loaded liposomes. As tutorial data for ANN, causal factors were used, which were fed into the computer program. The number of training cycles has been identified in order to optimize the performance of the ANN. The optimization was performed by minimizing the error between the predicted and real response values in the training step. The results showed that training was stopped at 10?000 training cycles with 80% of the pattern values, because at this point the ANN generalizes better. Minimum validation error was achieved at 12 hidden neurons in a single layer. MLR has great prediction ability, with errors between predicted and real values lower than 1% in some of the parameters evaluated. Thus, the performance of this model was compared to that of the MLR using a factorial design. Optimal formulations were identified by minimizing the distance among measured and theoretical parameters, by estimating the prediction errors. Results indicate that the ANN shows much better predictive ability than the MLR model. These findings demonstrate the increased efficiency of the combination of ANN and design of experiments, compared to the conventional MLR modeling techniques. 相似文献
994.
《中国有色金属学会会刊》2020,30(12):3195-3209
Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7xxx alloys. The 7050 alloy machining chips were spray formed, hot extruded, rotary swaged and heat-treated in order to improve mechanical properties. Microstructures, tensile properties and fatigue strength results for a 2.7 mm-diameter recycled wire are presented. Secondary phases and precipitates were investigated by XRD, SEM, EBSD, TEM and DSC. As-swaged and heat-treated (solution and aging) conditions were evaluated. Mechanical properties of both conditions outperformed AA7050 aerospace specification. Substantial grain refinement resulted from the extensive plastic deformation imposed by rotary swaging. Refined micrometric and sub-micrometric Al grains, as well as coarse and fine intermetallic precipitates were observed. Subsequent solution treatment resulted in a homogeneous, recrystallized and equiaxed microstructure with grain size of 9 μm. Nanoscale GP(I) zones and η′ phase precipitates formed after aging at 120 °C, imparting higher tensile (586 MPa) and fatigue (198 MPa) strengths. 相似文献
995.
Raja Aqib Sarang Kiani Shaher Bano Abdul Wadood Muhammad Atiq Ur Rehman 《International Journal of Applied Ceramic Technology》2021,18(3):544-562
In this study, we investigated surface and biological properties of Ag–Sr-doped mesoporous bioactive glass nanoparticle (Ag–Sr MBGN) loaded chitosan/gelatin coatings deposited by electrophoretic deposition (EPD) on 316L stainless steel. The EPD parameters, that is, deposition time, applied voltage, and distance between the electrodes was optimized by the Taguchi design of experiment (DoE) approach. Scanning electron microscopy (SEM) images illustrated the spherical morphology of the synthesized Ag–Sr MBGNs with the mean particle size of 160 ± 20 nm. Energy-dispersive X-ray (EDX) spectroscopy results confirmed the presence of Ag and Sr in the synthesized MBGNs. Optimum EPD parameters determined by DoE approach were 5 g/L of Ag–Sr MBGNs, deposition time of 5 min, and applied voltage of 30 V. SEM images confirmed that the coatings were fairly homogenous. Fourier-transform infrared spectroscopy and EDX results confirmed the presence of chitosan, gelatin, and Ag–Sr MBGNs in the coatings. Chitosan/gelatin/Ag–Sr MBGN composite coatings exhibited suitable wettability for the protein attachment and proliferation of osteoblast cells. The composite coatings exhibited suitable adhesion strength with the substrate. The coatings developed HA crystals upon immersion in simulated body fluid. The results of the turbidity test confirmed that the coatings are antibacterial to the Escherichia coli cells. 相似文献
996.
为提高冷弯机组的控制精度,设计了冷弯成型机组控制系统的多通道信号采集与分析系统。利用高精度传感器测量机组的运动参数,~LLabVIEw为软件平台、PXI为硬件平台构建信号采集与分析系统,对各通道的信号进行实时采集、处理与显示,并将所需数据反馈控制系统。实验结果表明:该系统运行稳定,信号采集精度高,并具有易扩展、易维护等牦最,适合广泛应用在测控领域中。 相似文献
997.
998.
999.
Among tunnel fire safety strategies, evacuation speed in smoke, which is the basic evacuation performance characteristic, is one of the most important factors when assessing safety. An evacuation experiment in a full-scale tunnel filled with smoke has been done in order to clarify the relation between extinction coefficient up to Cs = 1.0 m−1, which includes Cs = 0.4 m−1 as a Japanese road tunnel fire prevention standard, and evacuation speed. The maximum, minimum and mean values of normal walking speeds are almost constant regardless of the extinction coefficient. As for the emergency evacuation speeds, the maximum speed is largely influenced by extinction coefficient, decreasing rapidly from 3.55 m/s at Cs = 0.30 m−1 to 2.53 m/s at Cs = 0.75 m−1 while the minimum and mean speeds are almost constant with a slight decrease as Cs increases. The maximum evacuation speed trends in the present experiments and those in Frantzich and Nillson (2003, 2004) and Fridolf et al. (2013), lie on the same decreasing logarithmic curve as a function of extinction coefficient. 相似文献
1000.
介绍了几种钢铁中磷含量的测定方法,着重对铋磷钼蓝分光光度法进行了研究,阐述了实验所需仪器、试剂以及实验试剂制备流程,通过探讨实验的准确度与精密度,得出了一些有意义的结论。 相似文献