全文获取类型
收费全文 | 38222篇 |
免费 | 3901篇 |
国内免费 | 2192篇 |
专业分类
电工技术 | 812篇 |
综合类 | 3980篇 |
化学工业 | 7118篇 |
金属工艺 | 4401篇 |
机械仪表 | 1825篇 |
建筑科学 | 9133篇 |
矿业工程 | 1868篇 |
能源动力 | 545篇 |
轻工业 | 2073篇 |
水利工程 | 1442篇 |
石油天然气 | 1248篇 |
武器工业 | 290篇 |
无线电 | 863篇 |
一般工业技术 | 5029篇 |
冶金工业 | 2756篇 |
原子能技术 | 145篇 |
自动化技术 | 787篇 |
出版年
2024年 | 165篇 |
2023年 | 534篇 |
2022年 | 1017篇 |
2021年 | 1308篇 |
2020年 | 1242篇 |
2019年 | 1088篇 |
2018年 | 1142篇 |
2017年 | 1514篇 |
2016年 | 1531篇 |
2015年 | 1556篇 |
2014年 | 2282篇 |
2013年 | 2572篇 |
2012年 | 2743篇 |
2011年 | 2802篇 |
2010年 | 2089篇 |
2009年 | 2137篇 |
2008年 | 1989篇 |
2007年 | 2395篇 |
2006年 | 2191篇 |
2005年 | 1905篇 |
2004年 | 1633篇 |
2003年 | 1371篇 |
2002年 | 1205篇 |
2001年 | 1037篇 |
2000年 | 884篇 |
1999年 | 776篇 |
1998年 | 617篇 |
1997年 | 494篇 |
1996年 | 419篇 |
1995年 | 356篇 |
1994年 | 294篇 |
1993年 | 249篇 |
1992年 | 187篇 |
1991年 | 123篇 |
1990年 | 122篇 |
1989年 | 108篇 |
1988年 | 53篇 |
1987年 | 51篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 6篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1964年 | 4篇 |
1963年 | 2篇 |
1961年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The bond strength and slip of epoxy-coated reinforcing bars in concrete have been evaluated by carrying out single pullout and double pullout tests. In extended single pullout tests, slip measurements were made while tensile force was applied to reinforcing bars embedded in concrete. In double pullout tests, 20 cycles of load were applied at levels of steel stress between zero and 0·5 times characteristic steel strength. Strains were measured by electrical resistance strain gauges glued inside the bars. Both epoxy-coated and uncoated bars were used in the investigation, to obtain comparative results. The strain gradient along the bar was found to be less for the coated reinforcement. In general, the epoxy coating was found to increase slip in bond and thereby reduce the bond performance of coated bars. 相似文献
22.
23.
Shou-ren Wang Hao-ran Geng Lin-hai Hui Ying-zi Wang 《Journal of Materials Engineering and Performance》2007,16(1):113-118
A multiphase reticulated porous ceramic (RPC) as Si3N4–Al2O3–SiO2 was fabricated by replication techniques. Proper volumes of additives and twice sinter- twice immerse process endow the RPC
an excellent crack healing and submerging property. The compressive strength and fracture toughness improved owing to the
crack bridging behavior. The existence of pores in struts in RPC blunt the crack tip and increased the external force needed
to propagate the crack. The mechanisms play a beneficial role in enhancing the compressive strength and fracture strength.
Si3N4 RPC with additives of 5%Al and 5% Al2O3 yielded the compressive strength of 9.8 MPa and fracture toughness of 0.3 MPa m1/2. 相似文献
24.
Results of metal testing in impact tension–compression and indentation are analyzed. As the analysis of these data demonstrates, the strength of metals increases greatly with strain rates and at moderate indentation rates. At high indentation rates, a decrease in the specific energy (per unit volume of a displaced material) necessary for the formation of a conical cavity was observed. The account of the effects of viscosity, temperature increase upon plastic deformation and its localization can be used to explain the above phenomena. 相似文献
25.
26.
K.W. Allen S.M. Smith W.C. Wake A.O. van Raalte 《International Journal of Adhesion and Adhesives》1985,5(1):23-32
The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints. 相似文献
27.
28.
29.
The concept that plasticity index of soils can be defined as a range of water contents producing a 100-fold variation in undrained shear strength has been experimentally verified with the help of a large number of tests on soils of diverse nature. This has led to the redefinition of the plastic limit as the water content at which undrained shear strength is around 170 kN/m2. Undrained shear strength of a soil at the liquid limit can be considered to be around 1.7 kN/m2. Accordingly, both the liquid limit and the plastic limit have been determined in the present work by a single consistent method, i.e., the Swedish fall cone method. The undrained shear strength-water content relationship has been found to be log-linear for a wide range of water contents beginning from lower than the plastic limit to higher than the liquid limit. This resulted in the formulation of an expression for predicting undrained shear strength of a remolded soil at any water content based solely on its liquid limit and plastic limit. 相似文献
30.