全文获取类型
收费全文 | 15923篇 |
免费 | 1482篇 |
国内免费 | 799篇 |
专业分类
电工技术 | 1102篇 |
综合类 | 1373篇 |
化学工业 | 2583篇 |
金属工艺 | 865篇 |
机械仪表 | 862篇 |
建筑科学 | 1298篇 |
矿业工程 | 433篇 |
能源动力 | 448篇 |
轻工业 | 1200篇 |
水利工程 | 413篇 |
石油天然气 | 780篇 |
武器工业 | 131篇 |
无线电 | 1703篇 |
一般工业技术 | 1832篇 |
冶金工业 | 623篇 |
原子能技术 | 137篇 |
自动化技术 | 2421篇 |
出版年
2024年 | 67篇 |
2023年 | 230篇 |
2022年 | 431篇 |
2021年 | 609篇 |
2020年 | 441篇 |
2019年 | 406篇 |
2018年 | 410篇 |
2017年 | 447篇 |
2016年 | 405篇 |
2015年 | 600篇 |
2014年 | 757篇 |
2013年 | 809篇 |
2012年 | 951篇 |
2011年 | 967篇 |
2010年 | 935篇 |
2009年 | 876篇 |
2008年 | 913篇 |
2007年 | 864篇 |
2006年 | 790篇 |
2005年 | 644篇 |
2004年 | 572篇 |
2003年 | 802篇 |
2002年 | 1110篇 |
2001年 | 970篇 |
2000年 | 540篇 |
1999年 | 378篇 |
1998年 | 225篇 |
1997年 | 199篇 |
1996年 | 149篇 |
1995年 | 154篇 |
1994年 | 143篇 |
1993年 | 86篇 |
1992年 | 77篇 |
1991年 | 60篇 |
1990年 | 36篇 |
1989年 | 23篇 |
1988年 | 37篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
82.
Flammability ranking of foliage species by factor analysis of physical and chemical pyric properties
In this paper, factor analysis is introduced to evaluate the flammability of 55 foliage species that may be used in China for construction of the fuel break network of forest strips with lower flammability. Six pyric parameters, i.e. air dry moisture content, absolute dry moisture content, ignition point, ash content, caloric value and extractive content, are measured and used as variables for factor analysis. The covariance analysis shows that four principal factors can be extracted to reflect the flammability in different physical and chemical senses. In terms of the contributions of the four factors to the variances and the physical significance of the relevant parameters, the four factors are, respectively, termed as ‘flaming factor,’ ‘air dry factor,’ ‘ash factor’ and ‘absolute dry factor.’ The stability of the factor analysis method is examined by a different number of samples considered, and the variation degrees of the orderings indicate that the method has high reliability to measure the total flammability of foliage species. The results of the flammability evaluation are verified by comparison with the recommended tree species in the Chinese technology standard. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
83.
84.
85.
Closed-form solutions of pressure-impulse (P–I) diagrams for simply supported and fully clamped rigid-plastic beams subjected to impact load are developed. Two failure categories, i.e., bending failure and shear failure, are considered and the responses of the beams are analyzed based on five transverse velocity profiles. With proper failure criteria, the critical P–I equations for bending and shear failure are derived. After the simplification of the critical P–I equations, the influences of the shear-to-bending strength ratio and the boundary conditions on the P–I diagrams are discussed. The results are compared with those based on a single-degree-of-freedom (SDOF) model. It is shown that the proposed P–I diagram method can be conveniently applied to assess beam damage extents and damage patterns. Especially, the P–I diagrams have good agreement with those based on an elastic, perfectly plastic model when severe damage occurs. 相似文献
86.
87.
88.
89.
90.