全文获取类型
收费全文 | 13719篇 |
免费 | 1436篇 |
国内免费 | 635篇 |
专业分类
电工技术 | 318篇 |
技术理论 | 3篇 |
综合类 | 1096篇 |
化学工业 | 3003篇 |
金属工艺 | 327篇 |
机械仪表 | 377篇 |
建筑科学 | 658篇 |
矿业工程 | 189篇 |
能源动力 | 563篇 |
轻工业 | 3530篇 |
水利工程 | 131篇 |
石油天然气 | 226篇 |
武器工业 | 93篇 |
无线电 | 848篇 |
一般工业技术 | 1702篇 |
冶金工业 | 673篇 |
原子能技术 | 74篇 |
自动化技术 | 1979篇 |
出版年
2024年 | 128篇 |
2023年 | 473篇 |
2022年 | 590篇 |
2021年 | 735篇 |
2020年 | 637篇 |
2019年 | 597篇 |
2018年 | 521篇 |
2017年 | 553篇 |
2016年 | 535篇 |
2015年 | 564篇 |
2014年 | 804篇 |
2013年 | 828篇 |
2012年 | 835篇 |
2011年 | 988篇 |
2010年 | 643篇 |
2009年 | 680篇 |
2008年 | 634篇 |
2007年 | 782篇 |
2006年 | 677篇 |
2005年 | 579篇 |
2004年 | 504篇 |
2003年 | 425篇 |
2002年 | 337篇 |
2001年 | 264篇 |
2000年 | 224篇 |
1999年 | 222篇 |
1998年 | 153篇 |
1997年 | 107篇 |
1996年 | 124篇 |
1995年 | 108篇 |
1994年 | 91篇 |
1993年 | 60篇 |
1992年 | 51篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 17篇 |
1988年 | 26篇 |
1987年 | 9篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1979年 | 9篇 |
1965年 | 10篇 |
1964年 | 13篇 |
1961年 | 12篇 |
1959年 | 9篇 |
1957年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
41.
César I. Beristain Ebner Azuara Hugo S. Garcia & Eduardo J. Vernon-Carter 《International Journal of Food Science & Technology》1996,31(5):379-386
The water and oil uptake of mesquite and arabic gums in powdered form was studied at temperatures of 23, 35 and 45°C. A previously proposed equation to predict osmotic equilibrium was tested using the experimental data with both gums and a good statistical fit was obtained. Mesquite gum showed the highest water and oil absorption at all temperatures studied. Temperature dependence of the reciprocal of the S1 and WL∞ were determined using an Arrhenius equation. The activation energy for water and oil absorption for gum arabic was 21.98 and 39.57 kJ mol−1 , compared to that of mesquite gum having values of 15.79 and 46.16 kJ mol−1 , respectively. A second order kinetic model was obtained for water and oil absorption for both gums. 相似文献
42.
Preacher Kristopher J.; Rucker Derek D.; MacCallum Robert C.; Nicewander W. Alan 《Canadian Metallurgical Quarterly》2005,10(2):178
Analysis of continuous variables sometimes proceeds by selecting individuals on the basis of extreme scores of a sample distribution and submitting only those extreme scores to further analysis. This sampling method is known as the extreme groups approach (EGA). EGA is often used to achieve greater statistical power in subsequent hypothesis tests. However, there are several largely unrecognized costs associated with EGA that must be considered. The authors illustrate the effects EGA can have on power, standardized effect size, reliability, model specification, and the interpretability of results. Finally, the authors discuss alternative procedures, as well as possible legitimate uses of EGA. The authors urge researchers, editors, reviewers, and consumers to carefully assess the extent to which EGA is an appropriate tool in their own research and in that of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Gregory S. Ho Chen Huang Emily A. Carter 《Current Opinion in Solid State & Materials Science》2007,11(5-6):57-61
Orbital-free density functional theory (OF-DFT) can be made to scale linearly with sample size, allowing thousands of atoms to be treated explicitly with quantum mechanics. State-of-the-art kinetic energy density functionals and ion–electron pseudopotentials are used to obtain accurate structural property predictions for nanoparticles, nanowires, extended surfaces, and nanoindentation of simple metals. 相似文献
44.
Hua-Chieh Li 《Applicable Algebra in Engineering, Communication and Computing》2007,18(4):313-348
In this paper, we give a general criterion to determine when a complex space-time block code has a ring structure and then
we provide a complete list of complex space-time block codes which have ring structures up to size 4. 相似文献
45.
Much research has examined gender and age effects on compensation, concluding that a wage gap exists favoring men and negative stereotypes against older workers persist. Although the effect of an employee's gender or age has been widely studied, little work has examined the impact of the demographic characteristics of a focal employee's immediate referent groups (e.g., subordinates, peers, or supervisors) on pay. The effect of the gender and age composition of a focal manager's subordinates, peers, and supervisor on the manager's compensation levels was investigated in a sample of 2,178 managers across a wide range of organizations and functional areas. After controlling for a number of human capital variables, results indicated that not only does a wage gap favoring men exist, but also managerial pay is lower when managers' referent groups are largely female, when subordinates are outside the prime age group, and when peers and supervisors are younger. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Employing the density functional theory, we investigate the tensile and fracture processes of the Al/TiN(0 0 1) interface. The simulation presents directly the strain–stress relationship, the ideal tensile strength and the process of bond breaking of the system. Through the analysis of deformation, we find that the softer Al layers deform larger than the harder TiN layers during the tensile process. And fracture occurs between the interface and the sub-interface Al layers. In addition, the results show that during the tensile process, the ripple of the interfacial TiN layer decreases gradually with the increment of the strain. Charge transfer was detected from the Al to TiN layers near the interface area during the tensile process by means of charge density and density of states analyses. The charge transfer affects the fracture process. Compared to our previous study of the Al/TiN(1 1 1) interface, the Al/TiN(0 0 1) interface has smaller work of adhesion and larger tensile strength than the Al/TiN(1 1 1) interface. Our investigation shows that the fractures of the Al/TiN(0 0 1) and (1 1 1) interface systems both happen in the Al layers near the interface. 相似文献
48.
The fractions obtained from bagasse after activation with 17.5% NaOH, alternative alkylation with quarternary ammonium groups and extraction with 80% ethanol, water and 5% NaOH, were analyzed using pyrolysis-field ionization mass spectrometry (Py-FIMS). The proposed degradation products from lignin were mostly symmetric fragments containing two aromatic rings while the compounds formed from polysaccharides were the result of dehydration reactions. From the temperature-resolved Py-FIMS it could be seen that ethanol-lignin starts to degrade at temperatures lower than 180°C before the degradation of the hemicellulose fraction. The lignin markers are eliminated from hemicellulose fractions before the polysaccharide gasification starts. The quarternary ammonium groups are cleaved from the fractions at temperatures lower than 200°C. 相似文献
49.
本文提出了激光功能微调技术在高精度混合集成电路上的应用,讨论了关键技术问题,并以实例具体说明。该技术的应用为研制高精度混合集成电路开辟了新途径。 相似文献
50.