全文获取类型
收费全文 | 2269篇 |
免费 | 102篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 28篇 |
综合类 | 5篇 |
化学工业 | 339篇 |
金属工艺 | 74篇 |
机械仪表 | 53篇 |
建筑科学 | 162篇 |
矿业工程 | 6篇 |
能源动力 | 76篇 |
轻工业 | 166篇 |
水利工程 | 25篇 |
石油天然气 | 6篇 |
无线电 | 275篇 |
一般工业技术 | 321篇 |
冶金工业 | 345篇 |
原子能技术 | 11篇 |
自动化技术 | 481篇 |
出版年
2023年 | 19篇 |
2022年 | 23篇 |
2021年 | 44篇 |
2020年 | 38篇 |
2019年 | 33篇 |
2018年 | 60篇 |
2017年 | 41篇 |
2016年 | 67篇 |
2015年 | 51篇 |
2014年 | 64篇 |
2013年 | 152篇 |
2012年 | 112篇 |
2011年 | 118篇 |
2010年 | 102篇 |
2009年 | 91篇 |
2008年 | 95篇 |
2007年 | 122篇 |
2006年 | 107篇 |
2005年 | 69篇 |
2004年 | 64篇 |
2003年 | 87篇 |
2002年 | 44篇 |
2001年 | 43篇 |
2000年 | 40篇 |
1999年 | 46篇 |
1998年 | 82篇 |
1997年 | 36篇 |
1996年 | 51篇 |
1995年 | 21篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 36篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 21篇 |
1975年 | 12篇 |
1966年 | 5篇 |
排序方式: 共有2373条查询结果,搜索用时 15 毫秒
51.
针对乳腺癌数据存在的不平衡性问题,对标准的Adaboost算法进行改进,即首先引入BP神经网络,然后融合模拟退火遗传算法(SA-GA)较强的全局寻优能力和较快的收敛速度,最后通过权重的合理分配,提出BP-GamysBoost算法。同时为验证所提出的新算法BP-GamysBoost的合理性,从UCI机器学习知识库中获取WBCD数据库,比较BP-GamysBoost算法模型与BP模型、BP-GA模型、BP-Adaboost模型的稳定性、准确率、漏诊率、灵敏度等性能指标。最终结果表明,BP-GamysBoost模型在乳腺癌数据库中运行良好,并优于其他3种算法模型。 相似文献
52.
Mario Bragaglia Tony McNally Francesca R. Lamastra Valeria Cherubini Francesca Nanni 《应用聚合物科学杂志》2021,138(20):50423
Immiscible blends of ethylene-propylene-diene-monomer (EPDM) and polyoxymethylene (POM), when EPDM is the major phase were compatibilized on the addition of an ionomer, poly(ethylene-co-methacrylic acid). The inclusion of the ionomer reduced the interfacial tension between the two phases, such that the diameter of the POM domains were significantly reduced to between 0.5 and 2 μm, typical of that required to toughen ductile polymers. The mechanical properties of the resultant compatibilized blends were significantly enhanced with increases in Young's modulus (↑54%), tensile strength (σ, ↑139%), elongation at break (ε, ↑97%), and tensile toughness (↑500%) with increasing ionomer content, relative to EPDM rubber alone. The ShoreA hardness of the compatibilized blend was 70.1 compared with 56.8 for the immiscible binary blend and, 50.2 for neat EPDM rubber. 相似文献
53.
54.
C. -X. Ji Peter F. Ladwig Ronald D. Ott Y. Yang Joshua J. Yang Y. Austin Chang Eric S. Linville Jenny Gao Bharat B. Pant 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(6):50-54
Sputter-deposited, equiatomic PtMn thin films have application in giant magnetoresistive spin valves, tunneling magnetoresistive
spin valves, and magnetic random access memory. However, the as-deposited films are found to be a disordered A1 phase in a
paramagnetic state rather than an antiferromagnetic phase with L10 structure, which is needed for device operation. Therefore, a postannealing step is required to induce the phase transformation
from the asdeposited A1 face-centered-cubic phase to the antiferromagnetic L10 phase. The A1 to L10 metastable transformation was studied by x-ray diffraction and differential-scanning calorimetry. An exothermic transformation
enthalpy of −12.1 kJ/mol of atoms was determined. The transformation kinetics were simulated using the Johnson-Mehl-Avrami
analysis. 相似文献
55.
Chloride rich reinforced concrete prisms were coupled to chloride-free prisms and exposed to diurnal and seasonal temperature cycles typical of those found in the UK. Acoustic emissions (AE) and galvanic currents were continuously monitored and correlated with ambient temperature. AE and galvanic currents were found to emulate the evolution of temperature in the diurnal cycles, although no specific relationship between AE and galvanic current could be obtained. The influence of seasonal variations in galvanic current had no obvious influence on AE Energy per second over the range of corrosion rates studied. The findings suggest that AE is more sensitive to short term (diurnal) changes in corrosion rates than the longer (seasonal) effects. It was hypothesised that this is due to transitory changes in the internal microclimate of the concrete. 相似文献
56.
Tony L. Schmitz Jeremiah Couey Eric Marsh Nathan Mauntler Duke Hughes 《International Journal of Machine Tools and Manufacture》2007,47(5):841-851
This paper investigates the effect of milling cutter teeth runout on surface topography, surface location error, and stability in end milling. Runout remains an important issue in machining because commercially-available cutter bodies often exhibit significant variation in the teeth/insert radial locations; therefore, the chip load on the individual cutting teeth varies periodically. This varying chip load influences the machining process and can lead to premature failure of the cutting edges. The effect of runout on cutting force and surface finish for proportional and non-proportional tooth spacing is isolated here by completing experiments on a precision milling machine with 0.1 μm positioning repeatability and 0.02 μm spindle error motion. Experimental tests are completed with different amounts of radial runout and the results are compared with a comprehensive time-domain simulation. After verification, the simulation is used to explore the relationships between runout, surface finish, stability, and surface location error. A new instability that occurs when harmonics of the runout frequency coincide with the dominant system natural frequency is identified. 相似文献
57.
Shuang-Lin Chen Jie-Yu Zhang Xiong-Gang Lu Kuo-Chih Chou Y. Austin Chang 《Journal of Phase Equilibria and Diffusion》2006,27(2):121-125
Graham scan, a computational geometric algorithm for finding a two-dimensional convex hull, is introduced to calculate binary
phase diagrams. This algorithm is modified and applied to find the convex hull of discrete points in the space of Gibbs energy
vs mol fraction. The modified Graham scan algorithm has a very low computational cost, which improves efficiency in binary
phase diagram calculation. 相似文献
58.
Thin‐film encapsulated white organic light top‐emitting diodes using a WO3/Ag/WO3 cathode to enhance light out‐coupling
下载免费PDF全文
![点击此处可从《Journal of the Society for Information Display》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Karim Bouzid Tony Maindron Hani Kanaan 《Journal of the Society for Information Display》2016,24(9):563-568
An alternative design of a semitransparent cathode for top‐emission white‐fluorescent organic light‐emitting diodes (OLEDs) has been investigated. The scope of this study was to improve the luminance of OLEDs used for displays while keeping the current density versus voltage characteristic unchanged for addressing purposes. The use of an optical simulation tool allowed the optimization of the tri‐layer cathode WO3/Ag/WO3 to increase the light out‐coupling coefficient of the device leading to an increased white emission compared with a reference device with a Ca/Ag cathode. An increase of ~40% in luminance has been calculated by simulation and experimentally confirmed. The p‐i‐n OLED structure underneath the tri‐layer cathode allowed an efficient injection of electrons independently from the work function of WO3. The WO3/Ag/WO3 cathode has been also confirmed to be compatible with the atomic layer deposition technique for thin film encapsulation. Finally, lifetime measurements up to 600 h have been carried out to quantify the enhancements induced by the new cathode compared with the control device. It has been found that lifetimes of both cathode architectures are similar on this time scale, while the WO3/Ag/WO3 cathode shows a lower voltage drift versus aging. 相似文献
59.
Michael Unterkalmsteiner Tony Gorschek Robert Feldt Niklas Lavesson 《Empirical Software Engineering》2016,21(6):2324-2365
Software Engineering activities are information intensive. Research proposes Information Retrieval (IR) techniques to support engineers in their daily tasks, such as establishing and maintaining traceability links, fault identification, and software maintenance. We describe an engineering task, test case selection, and illustrate our problem analysis and solution discovery process. The objective of the study is to gain an understanding of to what extent IR techniques (one potential solution) can be applied to test case selection and provide decision support in a large-scale, industrial setting. We analyze, in the context of the studied company, how test case selection is performed and design a series of experiments evaluating the performance of different IR techniques. Each experiment provides lessons learned from implementation, execution, and results, feeding to its successor. The three experiments led to the following observations: 1) there is a lack of research on scalable parameter optimization of IR techniques for software engineering problems; 2) scaling IR techniques to industry data is challenging, in particular for latent semantic analysis; 3) the IR context poses constraints on the empirical evaluation of IR techniques, requiring more research on developing valid statistical approaches. We believe that our experiences in conducting a series of IR experiments with industry grade data are valuable for peer researchers so that they can avoid the pitfalls that we have encountered. Furthermore, we identified challenges that need to be addressed in order to bridge the gap between laboratory IR experiments and real applications of IR in the industry. 相似文献
60.