全文获取类型
收费全文 | 55802篇 |
免费 | 5100篇 |
国内免费 | 3477篇 |
专业分类
电工技术 | 3045篇 |
综合类 | 4781篇 |
化学工业 | 7861篇 |
金属工艺 | 3157篇 |
机械仪表 | 2175篇 |
建筑科学 | 7435篇 |
矿业工程 | 2094篇 |
能源动力 | 3670篇 |
轻工业 | 4128篇 |
水利工程 | 1447篇 |
石油天然气 | 2646篇 |
武器工业 | 516篇 |
无线电 | 5994篇 |
一般工业技术 | 7547篇 |
冶金工业 | 3907篇 |
原子能技术 | 1322篇 |
自动化技术 | 2654篇 |
出版年
2024年 | 243篇 |
2023年 | 884篇 |
2022年 | 1531篇 |
2021年 | 1808篇 |
2020年 | 1914篇 |
2019年 | 1696篇 |
2018年 | 1490篇 |
2017年 | 1923篇 |
2016年 | 1939篇 |
2015年 | 2032篇 |
2014年 | 3169篇 |
2013年 | 3351篇 |
2012年 | 3656篇 |
2011年 | 4066篇 |
2010年 | 3203篇 |
2009年 | 3194篇 |
2008年 | 2905篇 |
2007年 | 3562篇 |
2006年 | 3274篇 |
2005年 | 2816篇 |
2004年 | 2390篇 |
2003年 | 2136篇 |
2002年 | 1965篇 |
2001年 | 1569篇 |
2000年 | 1358篇 |
1999年 | 1075篇 |
1998年 | 865篇 |
1997年 | 786篇 |
1996年 | 628篇 |
1995年 | 560篇 |
1994年 | 435篇 |
1993年 | 393篇 |
1992年 | 307篇 |
1991年 | 255篇 |
1990年 | 232篇 |
1989年 | 162篇 |
1988年 | 118篇 |
1987年 | 88篇 |
1986年 | 55篇 |
1985年 | 49篇 |
1984年 | 51篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 26篇 |
1978年 | 7篇 |
1966年 | 8篇 |
1964年 | 7篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Cognitive Operations in the Generation Effect on a Recall Test: Role of Aging and Divided Attention.
Generation effect (generated words are better memorized than read words) of anagrams, rhymes, and associates of target words was examined in young, elderly, and very old subjects. Experiments 1 and 2 showed that only young subjects benefit from the generation effect in a free-recall test when the rule is of a phonological nature. Experiments 3, 4, and 5 showed that the generation effect of rhymes was due to a resources-dependent self-initiated process. Experiments 4 and 5 showed that in a divided-attention situation, generation effect of rhymes is not significant in young subjects, but that the generation effect of semantic associates remains significant for both groups (Experiment 5). The results are discussed within the environmental support framework and the transfer-appropriate processing framework. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
62.
To find the exact probability distribution of the global maximum or minimum of a random field within a bounded domain is a pending problem even for Gaussian fields. Except for very special examples of fields, recourse must be taken to approximate reasoning or asymptotic considerations to be judged with respect to accuracy by simulations. In this paper, the problem is addressed through a functional equation that leads to the definition of a class of distribution functions that depend solely on process or field characteristics and domain quantities that can be calculated explicitly. This distribution function class is studied for Gaussian processes in earlier works by the author and it has been obtained explicitly for Gaussian fields on rectangular domains in the plane. Simulation studies show that rather good predictions are obtained for sufficiently smooth wide band Gaussian processes and fields. In this paper, the distribution function is obtained in general for Gaussian fields over arbitrary bounded domains with piecewise continuous and differentiable boundaries, and as in earlier works the distribution function is tested against empirical distribution functions obtained by simulation of sample functions of a smooth approximately Gaussian field, herein called a broken line Hino field. For completeness this particular field type is defined in appendix a and appendix b. The paper concludes with a statistical application on data for plain concrete tensile strength. 相似文献
63.
Kenji Nomura Hiromichi OhtaKazushige Ueda Toshio Kamiya Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):322-326
We have investigated the characteristics of transparent metal-insulator-semiconductor field-effect transistors (MISFETs) fabricated using InGaO3(ZnO)m (m=integer) single-crystalline thin films as n-channel layers and amorphous alumina as gate insulator films. The MISFETs exhibit good characteristics such as insensitivity to visible light illumination, off-current as low as ∼1 nA with a positive threshold voltage of ∼3 V and on/off current ratio of 105. The field-effect mobility increased from ∼1 to ∼10 cm2 (V s)−1 as the m-value increased. Room temperature Hall mobility also increased. However, unexpectedly these values were lower than the field-effect mobility. It is explained by existence of shallow localized state in the homologous compounds. 相似文献
64.
多模干涉型集成光学器件研究进展 总被引:4,自引:1,他引:3
基于自镜像效应(SIE)的多模干涉(MMI)型集成光学器件是集成光学中具有广泛用途的重要器件。本文详细而系统地综述了近几年来MMI器在国内外的研究进展,特别是其在集成光学中的应用。 相似文献
65.
66.
Alleviation Effect of Lanthanum on Cadmium Stress in Seedling Hydroponic Culture of Kidney Bean and Corn 总被引:4,自引:0,他引:4
Since1970s,rare earths(RE)have been exten-sively used as micro-fertilizers for crops in China.Ithas already been proved that REcani mprove the pro-duction and quality of crops.However,there havebeen a fewinvestigations about using RE as regulatorin pollution ecology.For example,An et al[1]studiedthe effects of O3on wheat growth and the protectiveeffect of RE.Yan and Zhou et al[2,3]discussed theprotective effect of RE on plants under acid rainstress.Jia et al[4]and Hu et al[5]reported th… 相似文献
67.
The physical preconditions are considered for the temperature of a body to influence the force of gravity experienced by it. The results are given of experiments on weighing metal rods heated by ultrasound which confirm a dependence of the weight of the rods on their temperature. 相似文献
68.
利用Excel表格进行供暖系统计算 总被引:2,自引:0,他引:2
利用Excel表格进行供暖工程设计计算,可以减少工作量,提高工作效率。介绍了房间热负荷和供暖管道水力计算方法。 相似文献
69.
G. Lange 《Materialwissenschaft und Werkstofftechnik》2003,34(1):80-85
Failures by notch induced fatigue fractures Notches produce local stress concentrations and promote the formation of fatigue cracks. Characteristic types of notches as a result of design, manufacturing and operation are presented and remedial measures are discussed. Examples demonstrate the effect of different kinds of notches on various components. 相似文献
70.
本文探讨了装药结构中空气间隙作用的机理,提出了气体分子的迁移效应与碰撞效应,比较完满地解释了不同空气间隙对爆破效果的影响. 相似文献