全文获取类型
收费全文 | 322540篇 |
免费 | 27385篇 |
国内免费 | 18186篇 |
专业分类
电工技术 | 23079篇 |
技术理论 | 51篇 |
综合类 | 42875篇 |
化学工业 | 35073篇 |
金属工艺 | 11149篇 |
机械仪表 | 15666篇 |
建筑科学 | 49135篇 |
矿业工程 | 18021篇 |
能源动力 | 10053篇 |
轻工业 | 19599篇 |
水利工程 | 22160篇 |
石油天然气 | 16712篇 |
武器工业 | 2866篇 |
无线电 | 18930篇 |
一般工业技术 | 23031篇 |
冶金工业 | 16696篇 |
原子能技术 | 2966篇 |
自动化技术 | 40049篇 |
出版年
2024年 | 1152篇 |
2023年 | 3536篇 |
2022年 | 6440篇 |
2021年 | 7782篇 |
2020年 | 8404篇 |
2019年 | 7249篇 |
2018年 | 6855篇 |
2017年 | 8001篇 |
2016年 | 9396篇 |
2015年 | 10356篇 |
2014年 | 18227篇 |
2013年 | 16919篇 |
2012年 | 21655篇 |
2011年 | 23130篇 |
2010年 | 18085篇 |
2009年 | 19111篇 |
2008年 | 17776篇 |
2007年 | 22728篇 |
2006年 | 21316篇 |
2005年 | 18720篇 |
2004年 | 15914篇 |
2003年 | 14244篇 |
2002年 | 11699篇 |
2001年 | 9885篇 |
2000年 | 8433篇 |
1999年 | 7026篇 |
1998年 | 5318篇 |
1997年 | 4623篇 |
1996年 | 4233篇 |
1995年 | 3563篇 |
1994年 | 3210篇 |
1993年 | 2382篇 |
1992年 | 2141篇 |
1991年 | 1573篇 |
1990年 | 1320篇 |
1989年 | 1147篇 |
1988年 | 906篇 |
1987年 | 628篇 |
1986年 | 468篇 |
1985年 | 379篇 |
1984年 | 375篇 |
1983年 | 277篇 |
1982年 | 247篇 |
1981年 | 179篇 |
1980年 | 174篇 |
1979年 | 141篇 |
1978年 | 70篇 |
1977年 | 78篇 |
1976年 | 57篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
992.
993.
开放的ladder型无反转激光系统的稳定性分析 总被引:1,自引:0,他引:1
利用开放的ladder型无反转激光系统的密度矩阵运动方程组的定态解和激光场运动方程分析了系统的稳定性。结果表明:如果增益大于激光腔损耗,则零解是不稳定的;如果增益小于激光腔损耗,则零解是稳定的;如果增益大于激光腔损耗,则非零解是稳定的。 相似文献
994.
995.
简要分析了升船机上闸首基础岩体的特点,在施工期随上部建筑物形成的过程中沉降与水平形变随荷载变化的特征。分析认为:基础岩体形变与其受荷特点相吻合,目前建筑物总体安全状态正常,但部分坝段需引起注意,同时为验证设计、指导施工提供了依据。 相似文献
996.
997.
998.
999.
The boundary knot method (BKM) of very recent origin is an inherently meshless, integration‐free, boundary‐type, radial basis function collocation technique for the numerical discretization of general partial differential equation systems. Unlike the method of fundamental solutions, the use of non‐singular general solution in the BKM avoids the unnecessary requirement of constructing a controversial artificial boundary outside the physical domain. The purpose of this paper is to extend the BKM to solve 2D Helmholtz and convection–diffusion problems under rather complicated irregular geometry. The method is also first applied to 3D problems. Numerical experiments validate that the BKM can produce highly accurate solutions using a relatively small number of knots. For inhomogeneous cases, some inner knots are found necessary to guarantee accuracy and stability. The stability and convergence of the BKM are numerically illustrated and the completeness issue is also discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
1000.
A. Moropoulou N. Kouloumbi G. Haralampopoulos A. Konstanti P. Michailidis 《Progress in Organic Coatings》2003,48(2-4):259-270
Susceptibility of stone to salt decay is directly related to its microstructural and mechanical characteristics. In the present work, a porous stone from a quarry in Cyprus was examined. Samples of this stone were consolidated and protected with certain conservation materials. The modification of microstructural characteristics of the stone was evaluated by mercury intrusion porosimetry, while its mechanical characteristics were measured by compressive and bending strength tests. From these data, the susceptibility of Cyprus stone to salt (NaCl) decay was estimated. The values of crystallization pressure of NaCl were calculated and compared to the experimentally measured compressive and tensile strength of the stone, in order to examine the probability of stone disruption due to salt crystallization. The development of the phenomenon after coarse pores’ filling with crystals, i.e. crystallization of salts in capillaries or mechanical failure of the stone, was determined by thermodynamic analysis. Additionally, artificial weathering tests of marine salt spray were performed for the evaluation of stone’s durability after the conservation. The treated stone proved to be resistant to salt decay, as it presented ameliorated microstructural and mechanical characteristics, concerning decay due to soluble salt crystallization. The most possible thermodynamic scenario was small pores repletion with crystals, avoiding mechanical failure of the stone. 相似文献