全文获取类型
收费全文 | 26536篇 |
免费 | 3119篇 |
国内免费 | 1490篇 |
专业分类
电工技术 | 2250篇 |
综合类 | 2452篇 |
化学工业 | 2388篇 |
金属工艺 | 535篇 |
机械仪表 | 1541篇 |
建筑科学 | 3145篇 |
矿业工程 | 403篇 |
能源动力 | 1040篇 |
轻工业 | 5885篇 |
水利工程 | 1633篇 |
石油天然气 | 873篇 |
武器工业 | 296篇 |
无线电 | 1613篇 |
一般工业技术 | 3238篇 |
冶金工业 | 1229篇 |
原子能技术 | 469篇 |
自动化技术 | 2155篇 |
出版年
2024年 | 194篇 |
2023年 | 605篇 |
2022年 | 1301篇 |
2021年 | 1326篇 |
2020年 | 1352篇 |
2019年 | 1183篇 |
2018年 | 1118篇 |
2017年 | 1286篇 |
2016年 | 1363篇 |
2015年 | 1356篇 |
2014年 | 1654篇 |
2013年 | 1764篇 |
2012年 | 2173篇 |
2011年 | 2172篇 |
2010年 | 1370篇 |
2009年 | 1350篇 |
2008年 | 1189篇 |
2007年 | 1332篇 |
2006年 | 1184篇 |
2005年 | 981篇 |
2004年 | 771篇 |
2003年 | 651篇 |
2002年 | 494篇 |
2001年 | 430篇 |
2000年 | 345篇 |
1999年 | 320篇 |
1998年 | 279篇 |
1997年 | 208篇 |
1996年 | 176篇 |
1995年 | 182篇 |
1994年 | 138篇 |
1993年 | 131篇 |
1992年 | 112篇 |
1991年 | 76篇 |
1990年 | 76篇 |
1989年 | 61篇 |
1988年 | 49篇 |
1987年 | 39篇 |
1986年 | 27篇 |
1985年 | 30篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1980年 | 24篇 |
1979年 | 23篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1961年 | 13篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The current study replicated, in a sample of 2,300 outpatients seeking psychiatric treatment, a previous study (R. F. Krueger & M. S. Finger, 2001) that implemented an item response theory approach for modeling the comorbidity of common mood and anxiety disorders as indicators along the continuum of a shared latent factor (internalizing). The 5 disorders examined were major depressive disorder, social phobia, panic disorder/agoraphobia, specific phobia, and generalized anxiety disorder. The findings were consistent with the prior research. First, a confirmatory factor analysis yielded sufficient evidence for a nonspecific factor underlying the 5 diagnostic indicators. Second, a 2-parameter logistic item response model showed that the diagnoses were represented in the upper half of the internalizing continuum, and each was a strongly discriminating indicator of the factor. Third, the internalizing factor was significantly associated with 3 indexes of social burden: poorer social functioning, time missed from work, and lifetime hospitalizations. Rather than the categorical system of presumably discrete disorders presented in DSM-IV, these 5 mood and anxiety disorders may be alternatively viewed as higher end indicators of a common factor associated with social cost. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
The solutions of the spherically symmetric, linear, isothermal, and transient viscoelasticity problems via reciprocity theorem have been investigated for a specific material. The integral form of stress–strain relations has been used. The Laplace transform of a viscoelastic state, which is necessary for the integral equation arising as a result of reciprocity theorem, has been derived. This integral equation has been solved by Laplace transform. A sample problem has been solved to test the presented formulation. A numerical application of the analytic solution of this problem has been given. 相似文献
43.
Sinéad C. Mac Namara Maria M. Garlock David P. Billington 《Canadian Metallurgical Quarterly》2007,21(2):152-156
Steam generator replacement at nuclear power plants requires large construction openings in nuclear containment structures. This study examines the effects of such openings placed in a 61?cm (2?ft) thick dome of a shield building. The dome is cast in two layers, and the limiting cases of the two layers acting as one and the lower layer carrying the entire load are considered. Without openings, the stresses due to dead load in the structure are very low when compared to the material strength. With openings, the loads are easily redistributed around the opening, and the maximum stresses for the conservative case are between three and four and one-half times larger than in the original structure with no openings. The extent of the affected area around the holes is relatively small. Smooth corners in the openings are necessary to avoid high local stress concentrations. 相似文献
44.
利用随机振动复模态分析,提出了一种求解时变线性系统,在确定性激励与随机激励共同作用下非平稳随机响应的计算方法,并以舰载火箭武器系统为研究对象,用该法探讨了海浪对舰面火箭发射初始扰动和系统振动特性的影响。 相似文献
45.
单层球面网壳地震反应特征分析 总被引:29,自引:0,他引:29
考虑不同矢跨比、荷载、跨度和支座刚度等多种因素的影响,对单层球面网壳在地震作用下的反应进行了较全面的研究,给出了其随各参数变化的规律,得出了在单层球面网壳抗震设计中起控制作用的是水平地震作用而不是竖向地震作用等有益的结论.此外本文还给出了由于阻尼比不同而需对引用现行抗震规范反应谱分析的网壳地震作用进行修正的建议. 相似文献
46.
47.
48.
文克尔地基上中面x方向受力的矩形薄板的振动 总被引:1,自引:1,他引:0
建立文克尔地基上x=0与x=a两对边受面内均布拉(压)力作用的矩形薄板自由振动和强迫振动的微分方程并求得其通解。给出振型函数的表达式,用广义函数的富里叶展开,讨论板在不同形式载荷作用下的强迫振动响应。文中导出的各种情况下的影响函数,亦可用于求解相应情况下矩形薄板的静力弯曲与稳定性问题。 相似文献
49.
利用广义函数导出阶梯轴横向弯曲振动的微分方程。应用作者在文献[1]、[2]中引入的 W 运算符,给出了建立阶梯轴横向弯曲自由振动的特征方程的一般简易方法。文中还讨论了应用广义函数的 Fourier 展开来求解阶梯轴横向弯曲强迫振动响应的方法。 相似文献
50.
Energy Value of Resistant Starch 总被引:23,自引:0,他引:23
Resistant starch was evaluated for energy value using fine silica and normal starch as controls and young rats as a test model. The net increase in rats' carcass energy due to the test materials fed over a 3-wk period formed the basis for assessing energy value. Rats fed normal starch deposited about twice as much fat and significantly more protein in the carcass than those fed either resistant starch or silica. Rats fed resistant starch or silica showed similar growth responses and increases in components of body composition and carcass energy content. This suggested that resistant starch provided, like silica, no energy. 相似文献