全文获取类型
收费全文 | 8347篇 |
免费 | 845篇 |
国内免费 | 522篇 |
专业分类
电工技术 | 227篇 |
综合类 | 663篇 |
化学工业 | 899篇 |
金属工艺 | 1698篇 |
机械仪表 | 885篇 |
建筑科学 | 747篇 |
矿业工程 | 417篇 |
能源动力 | 309篇 |
轻工业 | 270篇 |
水利工程 | 147篇 |
石油天然气 | 544篇 |
武器工业 | 75篇 |
无线电 | 813篇 |
一般工业技术 | 1075篇 |
冶金工业 | 545篇 |
原子能技术 | 160篇 |
自动化技术 | 240篇 |
出版年
2024年 | 14篇 |
2023年 | 103篇 |
2022年 | 177篇 |
2021年 | 245篇 |
2020年 | 257篇 |
2019年 | 227篇 |
2018年 | 237篇 |
2017年 | 296篇 |
2016年 | 344篇 |
2015年 | 337篇 |
2014年 | 515篇 |
2013年 | 551篇 |
2012年 | 562篇 |
2011年 | 614篇 |
2010年 | 524篇 |
2009年 | 518篇 |
2008年 | 395篇 |
2007年 | 481篇 |
2006年 | 586篇 |
2005年 | 383篇 |
2004年 | 375篇 |
2003年 | 338篇 |
2002年 | 243篇 |
2001年 | 210篇 |
2000年 | 187篇 |
1999年 | 165篇 |
1998年 | 140篇 |
1997年 | 99篇 |
1996年 | 105篇 |
1995年 | 103篇 |
1994年 | 78篇 |
1993年 | 73篇 |
1992年 | 59篇 |
1991年 | 36篇 |
1990年 | 42篇 |
1989年 | 26篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有9714条查询结果,搜索用时 156 毫秒
991.
黏土心墙堆石坝是一种常用的坝型,黏土的碾压质量决定大坝运行中防渗效果的好坏.以骆察尼大坝为例,通过黏土的现场碾压试验,分析其压实特性,并探讨粘性土料最优含水率、最佳铺料厚度和碾压遍数等施工参数的取舍,从而为同类型条件下的施工提供参考. 相似文献
992.
以恒压模式在Na2CO3-Na2SiO3的电解液中对TC4钛合金进行微弧氧化,研究微弧氧化电参数:正向电压、脉宽、脉间对陶瓷膜表面形貌、厚度、粗糙度的影响。结果表明:电压恒定时增加脉宽和脉间有利于提高陶瓷膜的致密性;降低正向电压,降低脉宽,增加脉间有利于得到较薄的钛合金微弧氧化陶瓷膜;降低正向电压,降低脉宽,增加脉间有利于钛合金微弧氧化陶瓷膜的粗糙度减小. 相似文献
993.
The use of design method considering a coil temperature to maximize the thrust density of a double side coreless permanent
magnet linear synchronous motor (PMLSM) was presented. The optimal current density where the coil temperature reaches an allowable
temperature with heat analysis was applied to a magnetic circuit design. Changing optimal current density is verified whenever
the design parameters of the motor are altered. The design parameters of the motor were applied to thrust calculation. In
this way, the optimal model, which is a reversal of the existing design method, is deduced. The results were compared with
the experimental data to verify their validity. When the convection heat transfer coefficient is applied to other models,
the results of the analysis and test values show good concordance. The method proposed has some limitations. 相似文献
994.
Both experimental and mechanical analyses were carried out to investigate the characteristics of thickness distribution for
tailor-welded tube (TWT) hydroforming with dissimilar thickness. Then, the effects of weld-seam position and thickness difference
were also revealed. A multiple-diameter tube was formed to reveal the characteristics and the regularity of thickness distribution
during TWT hydroforming. It is indicated that there are obvious fluctuations in thickness distribution though the TWTs have
the same expansion ratio. The thinning ratio of thinner tube is bigger than that of thicker tube especially in the zone closed
to the weld-seam. The difference in thinning ratio between two tube segments can reach 9%. Consequently, sudden and large
fluctuation of thickness appears in the zone nearby the weld-seam. The difference in thinning ratio between thinner and thicker
tubes enlarges as the thickness difference increases, but improves as length ratio increases. Different strain states are
the main reason to induce nonuniform thickness distribution. The difference in thickness is the main reason to induce different
strain states on thinner and thicker tubes. 相似文献
995.
应用压电本构方程,通过分析圆环径向小体元的振动,将其等效为长度伸缩振动模态,以简化圆环的运动方程,推导其径向厚度振动的谐振频率。采用有限元分析法对圆环进行建模仿真,计算出圆环谐振频率,并用阻抗测量法实测圆环实体振动进行比较,结果表明圆环厚度为4~9 mm时吻合较好。 相似文献
996.
以服用为目的的合成革,其厚度变异性、强力及透湿性决定了其服用的基本性能,而革基布是构成合成革最基本的元素.选取工艺一致但涤粘原料配比不一样的3种水刺无纺布,对比水刺无纺革基布的3种基本的性能指标,得出对水刺无纺革基布性能最佳的涤粘原料配比是55/45. 相似文献
997.
王虎妹 《武汉大学学报(工学版)》2011,(6):752-756
对三个不同地点的带帽刚性桩复合地基工程进行试验监测,根据试验监测数据结果进行分析,可见褥垫层不同厚度对带帽刚性桩承载力和沉降变形的影响:设计褥垫层在某一合适的厚度,能有效降低桩身承载力,提高桩间土的承载力,使桩和桩间土合理共同承担荷载,降低复合地基沉降变形,减少地基对基础的应力集中,对工程实际有一定的指导意义.在试验分... 相似文献
998.
计算了不同管径和保温厚度下蒸汽管道输送高压蒸汽的热损失和温度降。结果表明:保温厚度越大,蒸汽的热损失越小、温度降越小;保温材料导热系数与蒸汽的热损失呈正比;环境温度越高,蒸汽的热损失越小;环境风速对热损失的影响不大。同时研究了保温材料选择和保温结构对节能的影响。 相似文献
999.
Mode I fatigue crack growth tests were conducted on joints bonded with a filled adhesive (A) at 20 Hz and 2 Hz and on joints bonded with a filled and toughened adhesive (B) at 20 Hz, 2 Hz, 0.2 Hz and 0.02 Hz. Strain energy release rate, G, and J-integral were evaluated based on elastic and elastoplastic finite element analyses (FEA) of the joints bonded with adhesive A and B, respectively. For the configurations considered, J was found to be path-independent and did not differ much from G. The fatigue crack growth rate (FCGR), da/dN, in the joints bonded with adhesive A was relatively independent of frequency while it increased with decreasing frequency at given δ for the joints bonded with adhesive B. The fatigue processes in both adhesives involved the cracking of the filler particles and subsequent linkage of the resultant microcracks. The process zone in adhesive B is larger than that in adhesive A and it increases with decreasing frequency. It is suggested that this variation in process zone size can account for the observed fatigue behaviour. The fatigue crack growth velocity, da/dt, was also calculated for the joints bonded with adhesive B and the variation of da/dt with test frequency at given δG is much smaller than the variation in da/dN, suggesting a creep effect in the fatigue crack growth. 相似文献
1000.