全文获取类型
收费全文 | 36534篇 |
免费 | 3502篇 |
国内免费 | 1784篇 |
专业分类
电工技术 | 2703篇 |
综合类 | 2476篇 |
化学工业 | 8782篇 |
金属工艺 | 6607篇 |
机械仪表 | 1495篇 |
建筑科学 | 3714篇 |
矿业工程 | 1075篇 |
能源动力 | 1230篇 |
轻工业 | 2430篇 |
水利工程 | 801篇 |
石油天然气 | 1204篇 |
武器工业 | 266篇 |
无线电 | 2054篇 |
一般工业技术 | 4251篇 |
冶金工业 | 1767篇 |
原子能技术 | 245篇 |
自动化技术 | 720篇 |
出版年
2024年 | 208篇 |
2023年 | 754篇 |
2022年 | 1490篇 |
2021年 | 1644篇 |
2020年 | 1438篇 |
2019年 | 1124篇 |
2018年 | 1068篇 |
2017年 | 1480篇 |
2016年 | 1381篇 |
2015年 | 1396篇 |
2014年 | 1944篇 |
2013年 | 2013篇 |
2012年 | 2444篇 |
2011年 | 2731篇 |
2010年 | 1884篇 |
2009年 | 2179篇 |
2008年 | 1759篇 |
2007年 | 2100篇 |
2006年 | 2093篇 |
2005年 | 1732篇 |
2004年 | 1440篇 |
2003年 | 1245篇 |
2002年 | 1032篇 |
2001年 | 900篇 |
2000年 | 748篇 |
1999年 | 688篇 |
1998年 | 547篇 |
1997年 | 467篇 |
1996年 | 349篇 |
1995年 | 354篇 |
1994年 | 293篇 |
1993年 | 197篇 |
1992年 | 161篇 |
1991年 | 135篇 |
1990年 | 92篇 |
1989年 | 80篇 |
1988年 | 54篇 |
1987年 | 42篇 |
1986年 | 24篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1961年 | 2篇 |
1960年 | 3篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
本文研究了一种Zn-Ti合金新镀层,经盐水浸泡、中性盐雾和大气暴露试验结果试验,其耐蚀明显超过镀Zn层,并与镀Cd层相近,用缺口持久拉伸试验检验氢脆性,拉伸持续时间超过200h,达到原航空部部颁标准(HB5067-85),该镀层适用于高强度钢防护。 相似文献
143.
Electrochemical impedance measurements have been used to characterize zinc selenide films prepared by electrochemical co-deposition at a platinum rotating disk electrode. Estimations of capacitance and polarization resistance of variously prepared electrodeposits have been carried out to determine charge carrier density and corrosion rates. 相似文献
144.
145.
由于十三陵蓄能电站上水库地处蟒山之巅,所在山体地质条件复杂。施工期埋设了大量的监测仪器,原有人工监测系统效率低、资料分析的同步性差。2002年5月,对其进行了自动化改造,现已有一套符合其特点的自动化监测系统。十三陵上水库水工建筑自动监测系统已正常运行了三年,同时也存在着问题,有待于进一步的探讨和改进。 相似文献
146.
The failure of acetabular cups via loosening, migration or fracture is partially related to the stress distribution existing in the acetabular region. The complexity of the investigation of these stresses demands the application of a variety of model testing techniques involving combined embedded strain gauging, finite element analysis, transmission and reflective photoelasticity and crack propagation studies. The application of these procedures are described and the difficulties of obtaining representative loadings and restraints are commented upon. 相似文献
147.
Scott C. Thompson Anjali Pandit Nitin P. Padture Subra Suresh 《Journal of the American Ceramic Society》2002,85(8):2059-2064
The processing of stepwise graded Si3 N4 /SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si3 N4 (low elastic modulus, low thermal expansion coefficient) forms the top contact surface, with a stepwise gradient in composition existing between the two over a depth of ∼1.7 mm. The resulting Si3 N4 contact surface is fine-grained and dense, and it contains only 2 vol% yttrium aluminum garnet (YAG) additive. This graded ceramic shows resistance to cone-crack formation under Hertzian indentation, which is attributed to a combined effect of the elastic-modulus gradient and the compressive thermal-expansion-mismatch residual stress present at the contact surface. The presence of the residual stress is corroborated and quantified using Vickers indentation tests. The graded ceramic also possesses wear properties that are significantly improved compared with dense, monolithic Si3 N4 containing 2 vol% YAG additive. The improved wear resistance is attributed solely to the large compressive stress present at the contact surface. A modification of the simple wear model by Lawn and co-workers is used to rationalize the wear results. Results from this work clearly show that the introduction of surface compressive residual stresses can significantly improve the wear resistance of polycrystalline ceramics, which may have important implications for the design of contact-damage-resistant ceramics. 相似文献
148.
高密度聚乙烯6300M和2480的耐环境应力开裂性能研究 总被引:1,自引:0,他引:1
研究了成型塑料管材的两种牌号的高密度聚乙烯(HDPE)6300M和2480的耐环境应力开裂(ESCR)性能。研究中采用的测试方法为一般弯曲试片法、在管上取样的弯曲试片法和恒定压应变法-压缩环法。根据两种材料测试结果及与其他牌号HDPE测试数据比较,对他们的ESCR进行评价,并讨论和解释了HDPE结构参数,ESCR与韧性形变和脆性断裂之间的联系。 相似文献
149.
150.
Thermal Shock Behavior of Porous Silicon Carbide Ceramics 总被引:1,自引:0,他引:1
Using the water-quenching technique, the thermal shock behavior of porous silicon carbide (SiC) ceramics was evaluated as a function of quenching temperature, quenching cycles, and specimen thickness. It is shown that the residual strength of the quenched specimens decreases gradually with increases in the quenching temperature and specimen thickness. Moreover, it was found that the fracture strength of the quenched specimens was not affected by the increase of quenching cycles. This suggests a potential advantage of porous SiC ceramics for cyclic thermal-shock applications. 相似文献