全文获取类型
收费全文 | 118869篇 |
免费 | 13202篇 |
国内免费 | 8277篇 |
专业分类
电工技术 | 9611篇 |
技术理论 | 1篇 |
综合类 | 11468篇 |
化学工业 | 14750篇 |
金属工艺 | 7376篇 |
机械仪表 | 7344篇 |
建筑科学 | 8107篇 |
矿业工程 | 4538篇 |
能源动力 | 3264篇 |
轻工业 | 13198篇 |
水利工程 | 3690篇 |
石油天然气 | 4148篇 |
武器工业 | 1820篇 |
无线电 | 11385篇 |
一般工业技术 | 9948篇 |
冶金工业 | 12022篇 |
原子能技术 | 1789篇 |
自动化技术 | 15889篇 |
出版年
2024年 | 761篇 |
2023年 | 1964篇 |
2022年 | 4424篇 |
2021年 | 5673篇 |
2020年 | 4172篇 |
2019年 | 2954篇 |
2018年 | 3258篇 |
2017年 | 3654篇 |
2016年 | 3388篇 |
2015年 | 5112篇 |
2014年 | 6249篇 |
2013年 | 7556篇 |
2012年 | 9204篇 |
2011年 | 9438篇 |
2010年 | 9070篇 |
2009年 | 8393篇 |
2008年 | 8423篇 |
2007年 | 8241篇 |
2006年 | 7096篇 |
2005年 | 5530篇 |
2004年 | 4169篇 |
2003年 | 3129篇 |
2002年 | 2964篇 |
2001年 | 2718篇 |
2000年 | 1993篇 |
1999年 | 1126篇 |
1998年 | 2973篇 |
1997年 | 1778篇 |
1996年 | 1186篇 |
1995年 | 732篇 |
1994年 | 595篇 |
1993年 | 615篇 |
1992年 | 190篇 |
1991年 | 167篇 |
1990年 | 153篇 |
1989年 | 158篇 |
1988年 | 107篇 |
1987年 | 101篇 |
1986年 | 86篇 |
1985年 | 63篇 |
1984年 | 17篇 |
1983年 | 27篇 |
1982年 | 44篇 |
1981年 | 45篇 |
1980年 | 77篇 |
1979年 | 22篇 |
1977年 | 161篇 |
1976年 | 284篇 |
1959年 | 43篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
32.
The rate of filtration and the water content of cake are influenced by the existence of a dense skin in a highly compressible
cake. The phenomenon of the dense skin has been rarely studied, and its existence has not been verified experimentally. In
this study, the porosity variation in a very compressible cake is measured by using a new experimental apparatus, and with
this the existence of dense skin has been established experimentally. ‘Unified theory on solid-liquid separation’, a recently
developed theory, is utilized for calculating the porosity variation in a very compressible cake. 相似文献
33.
34.
35.
36.
37.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
38.
This study employs a relational dialectics approach to gain insights into the nature of relational communication via Cyworld , a Korean social network site. Qualitative analysis of in-depth interview data from 49 users suggests that Cyworld users routinely negotiate multiple dialectical tensions that are created within the online world, transferred from face-to-face contexts, or imposed by interpersonal principles that relate to Korea's collectivistic culture. The interviewees experienced a new relational dialectic of interpersonal relations versus self-relation, analogous to Baxter and Montgomery's (1996) connection-autonomy contradiction. Their responses suggest that Cyworld's design features and functions encourage users to transcend the high-context communication of Korean culture by offering an alternative channel for elaborate and emotional communication, which fosters the reframing of relational issues offline. Cy-Ilchons (online buddies) virtually extend the Korean cultural concept of blood ties, called yons, in ways that intensify the openness-closedness contradiction at early stages of relationship formation. 相似文献
39.
40.
Spontaneous mutation for a quantitative trait in Drosophila melanogaster. II. Distribution of mutant effects on the trait and fitness 总被引:7,自引:0,他引:7
Exposure of the Chinese hamster ovarian AuxB1 cell line in vitro to fractionated X-irradiation generated sublines designated DXR-10, which proved resistant to multiple drugs and overexpressed P-glycoprotein (Pgp), as judged by Western blotting using the C219 monoclonal antibody. Further characterization of these irradiated DXR-10 sublines has provided evidence for: (i) the expression of cross-resistance to gramacidin D, taxol, puromycin and Navelbine, but not to daunomycin or mitoxantrone; (ii) overexpression of the class I Pgp, as judged by Western blotting using the C494 monoclonal antibody; (iii) decreased accumulation of 3H-vincristine, which could be enhanced by verapamil addition; (iv) unaltered accumulation and subcellular distribution of adriamycin; (v) significantly increased rhodamine 123 accumulation in the presence of verapamil; (vi) plasma-membrane ultrastructural modifications resulting in a significantly increased surface area; (vii) numerous clonal karyotypic alterations, with abnormalities involving the long arm of chromosome 1 being consistently identified; (viii) a lack of overexpression of sorcin; (ix) increased total glutathione levels and overexpression of glutathione S-transferase pi. The fact that only certain of these features are considered characteristic of the 'classic' multidrug-resistant CHRC5 cell line supports our earlier proposal that exposure to fractionated X-irradiation results in the expression of a unique drug-resistance phenotype. 相似文献