全文获取类型
收费全文 | 10728篇 |
免费 | 1764篇 |
国内免费 | 706篇 |
专业分类
电工技术 | 999篇 |
技术理论 | 1篇 |
综合类 | 686篇 |
化学工业 | 1600篇 |
金属工艺 | 1035篇 |
机械仪表 | 682篇 |
建筑科学 | 517篇 |
矿业工程 | 156篇 |
能源动力 | 348篇 |
轻工业 | 257篇 |
水利工程 | 83篇 |
石油天然气 | 247篇 |
武器工业 | 95篇 |
无线电 | 1242篇 |
一般工业技术 | 1342篇 |
冶金工业 | 433篇 |
原子能技术 | 36篇 |
自动化技术 | 3439篇 |
出版年
2024年 | 33篇 |
2023年 | 120篇 |
2022年 | 179篇 |
2021年 | 242篇 |
2020年 | 341篇 |
2019年 | 477篇 |
2018年 | 423篇 |
2017年 | 524篇 |
2016年 | 585篇 |
2015年 | 614篇 |
2014年 | 704篇 |
2013年 | 676篇 |
2012年 | 668篇 |
2011年 | 671篇 |
2010年 | 541篇 |
2009年 | 535篇 |
2008年 | 545篇 |
2007年 | 692篇 |
2006年 | 623篇 |
2005年 | 594篇 |
2004年 | 478篇 |
2003年 | 498篇 |
2002年 | 538篇 |
2001年 | 552篇 |
2000年 | 384篇 |
1999年 | 289篇 |
1998年 | 198篇 |
1997年 | 139篇 |
1996年 | 99篇 |
1995年 | 64篇 |
1994年 | 44篇 |
1993年 | 33篇 |
1992年 | 29篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1958年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The iterative method labelled correlation-based tuning (CbT) is considered in this paper for tuning linear time-invariant multivariable controllers. The approach allows one to tune some elements of the controller transfer function matrix to satisfy the desired closed-loop performance, while the other elements are tuned to mutually decouple the closed-loop outputs. Decoupling is achieved by decorrelating a given reference with the non-corresponding outputs. The controller parameters are calculated either by solving a correlation equation (decorrelation procedure) or by minimizing a cross-correlation function (correlation reduction). In addition, the preferred way of exciting a 2×2 system for CbT is investigated via the accuracy of the estimated controller parameters. It is shown that simultaneous excitation of both reference signals does not improve the accuracy of the estimated controller parameters compared to the case of sequential excitation. In fact, one must choose between low experimental cost (simultaneous excitation) and better accuracy of the estimated parameters (sequential excitation). The theoretical results are illustrated via three simulation studies. 相似文献
993.
通过器件模拟并结合实验结果,在已有PIN(Positive intrinsic negative)和DPD(Double photo-diodes)探测器电路模型基础之上,对带浅沟槽隔离(STI)准PIN结构的DPD探测器电路模型进行了探讨。模拟了由深N阱和浅沟槽给DPD带来的性能上的改变,同时结合实验结果,从响应电流和探测器的等效串联电阻两方面对电路模型进行了修正,得到了符合该器件的较准确电路模型。 相似文献
994.
Ming ZHU Meishuan LI Shuwang DUO Yanchun ZHOU 《材料科学技术学报》2007,23(3):373-378
Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3+Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales. 相似文献
995.
996.
997.
Eakin Elizabeth G.; Bull Sheana S.; Riley Kimberley M.; Reeves Marina M.; McLaughlin Patty; Gutierrez Silvia 《Canadian Metallurgical Quarterly》2007,26(4):392
Objective: The Resources for Health trial evaluates a social-ecologically based lifestyle (physical activity and diet) intervention targeting low-income, largely Spanish-speaking patients with multiple chronic conditions. Design: A randomized controlled trial was conducted with 200 patients recruited from an urban community health center and assigned to intervention and usual care conditions. Intervention involved 2 face-to-face, self-management support and community linkage sessions with a health educator, 3 follow-up phone calls, and 3 tailored newsletters. Main Outcome Measures: Primary outcomes measured at 6-months were changes in dietary behavior and physical activity. Changes in multilevel support for healthy living were evaluated as a secondary outcome. Results: After adjustment for age, sex, language, and number of chronic conditions, significant intervention effects were observed for dietary behavior and multilevel support for healthy lifestyles but not for physical activity. Conclusion: The Resources for Health intervention provides an effective and practical model for improving health behavior among low-income, Spanish-speaking patients with multiple chronic conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
该文介绍了MapViewer的基本构成和技术特点,研究和分析了以MapViewer与Oracle空间数据库相结合开发基于位置的服务系统的总体体系结构和实现原理,构建并实现了一种的基于Mapviewer平台的基于位置服务的应用,即在地图上的范围查询服务.最后总结了基于位置服务的技术具有广阔的应用前景和巨大的商业发展潜力. 相似文献
999.
Huang Shifeng 《Materials Letters》2007,61(30):5217-5219
Composites with 2-2 connectivity were fabricated from plates of “PMN” ceramic embedded in a sulphoaluminate cement matrix by a cut-filling process. The influences of the water-cement ratio in the matrix on the properties of the composite were analyzed. The results show that when the water-cement ratio is less than 0.4, the piezoelectric stain factor d33 and piezoelectric voltage factor g33 increase smoothly. When the water-cement ratio is larger than 0.4, d33 and g33 increase obviously with increasing the water-cement ratio. This is attributed to a more effective contact between the active and matrix phases. d33 = 322 pc N− 1 and g33 = 20.9 mV mN− 1 at a water-cement ratio of 0.45. The planar electromechanical coupling coefficient Kp of the composite is nearly independent of the water-cement ratio. With increasing the water-cement ratio, the thickness electromechanical coupling coefficient Kt of the composite increases, while the mechanical quality factor Qm exhibits the trend of decrease. 相似文献
1000.
Aditya M. Vora 《Journal of Superconductivity and Novel Magnetism》2007,20(5):387-392
The theoretical study of the superconducting state parameters (SSP) viz. electron–phonon coupling strength λ, Coulomb pseudopotential μ
*, transition temperature T
C
, isotope effect exponent α and effective interaction strength N
O
V of 5d-transition metals based binary alloys have been made extensively in the present work using a model potential for the
first time. A considerable influence of various exchange and correlation functions on λ and μ
* is found from the present study. The present results of the SSP are found in qualitative agreement with the available experimental
data wherever it exists. 相似文献