全文获取类型
收费全文 | 76000篇 |
免费 | 4594篇 |
国内免费 | 2226篇 |
专业分类
电工技术 | 3210篇 |
技术理论 | 2篇 |
综合类 | 3225篇 |
化学工业 | 9890篇 |
金属工艺 | 2162篇 |
机械仪表 | 2654篇 |
建筑科学 | 3862篇 |
矿业工程 | 1426篇 |
能源动力 | 1259篇 |
轻工业 | 5552篇 |
水利工程 | 1304篇 |
石油天然气 | 1641篇 |
武器工业 | 352篇 |
无线电 | 5798篇 |
一般工业技术 | 7091篇 |
冶金工业 | 22647篇 |
原子能技术 | 627篇 |
自动化技术 | 10118篇 |
出版年
2024年 | 285篇 |
2023年 | 934篇 |
2022年 | 1496篇 |
2021年 | 1838篇 |
2020年 | 1421篇 |
2019年 | 1113篇 |
2018年 | 1649篇 |
2017年 | 1947篇 |
2016年 | 2183篇 |
2015年 | 2326篇 |
2014年 | 2345篇 |
2013年 | 2665篇 |
2012年 | 4712篇 |
2011年 | 5063篇 |
2010年 | 2823篇 |
2009年 | 2715篇 |
2008年 | 2512篇 |
2007年 | 2374篇 |
2006年 | 2224篇 |
2005年 | 4682篇 |
2004年 | 3434篇 |
2003年 | 2789篇 |
2002年 | 1514篇 |
2001年 | 1356篇 |
2000年 | 954篇 |
1999年 | 1235篇 |
1998年 | 6636篇 |
1997年 | 4226篇 |
1996年 | 2905篇 |
1995年 | 1756篇 |
1994年 | 1353篇 |
1993年 | 1299篇 |
1992年 | 422篇 |
1991年 | 437篇 |
1990年 | 406篇 |
1989年 | 373篇 |
1988年 | 349篇 |
1987年 | 260篇 |
1986年 | 236篇 |
1985年 | 191篇 |
1984年 | 85篇 |
1983年 | 93篇 |
1982年 | 147篇 |
1981年 | 184篇 |
1980年 | 205篇 |
1979年 | 62篇 |
1978年 | 97篇 |
1977年 | 608篇 |
1976年 | 1319篇 |
1975年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
41.
Presents an obituary and information about the life and accomplishments of Josef Maria Bro?ek. Born August 14, 1913, in the ancient town of Melnik, in central Bohemia, today the Czech Republic, Josef spent his childhood in Poland (Warsaw, 1913- 1915) and in Siberia (1915-1920). His education in Czechoslovakia culminated with a thesis on "Memory, Its Measurement and Structure" and a PhD awarded in June 1937. In the history of psychology, his lifetime project bore the title "Historiography of Psychology Around the World," and it covered about 20 geographical areas. Extensive attention was devoted to institutional and organizational developments as journals, academic settings, archives, museums, research groups, conferences, and institutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
43.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
44.
光通信技术发展的新亮点 总被引:1,自引:0,他引:1
自光通信问世以来,经历了研究探索、实用化、推广应用、快速发展等时期,直至2001年,达到急剧发展的高潮。随着世界经济的滑坡,通信行业的不景气,使光通信也进入了寒冷的冬天。实际上,即使在经济低速的时期,光通信的技术依然没有停止发展,而且出现了不少继续将光通信推向前进的新亮点。从技术和应用的角度,简要介绍一些光通信的新技术。 相似文献
45.
46.
47.
三江盆地西部藻类地层学特征 总被引:3,自引:1,他引:2
本文依据三江盆地西部4口井的藻类分布特征,自下而上划分9个组合,并对各组合的时代及沉积环境进行了探讨。 相似文献
48.
The expression of cytokeratins (CK), involucrin, vimentin, CD34, and alpha-smooth-muscle actin was studied in fetal and adult hair follicles. The first stage of the developing hair follicle is characterized by palisaded, elongated epithelial cells budding from the epidermal basal layer. These cells express CK5/6, CK14, CK17, CK19, and vimentin. During the following weeks of gestation, different structures in the developing hair follicle can be identified and characterized. The matrical cells display only CK19. The keratinocytes of the outer root sheath express CK5/6, CK14, CK17, CK19, and involucrin; those of the inner root sheath, CK4, CK18, and involucrin; those of the isthmus, the same profile as the ORS. In the infundibulum, the basal-layer keratinocytes express CK5/6, CK14, CK17, and CK19, whereas in the suprabasal layers CK1, CK4, CK10, CK14, and CK17 are seen. The adult hair follicle in anagen fails to express CK19 in the matrical cells and isthmus and both CK17 and CK19 in the infundibulum. These profiles of intermediate filaments and other markers appear to be potentially useful in categorizing neoplasms with apparent follicular differentiation. 相似文献
49.
50.
Phospholamban (PLN) was expressed in Escherichia coli as a protein fusion with glutathione S-transferase (GST). GST-PLN was mostly present in the insoluble protein fraction and accounted for approximately 50% of total insoluble protein. Attempts to suppress inclusion body formation or to use GST as an affinity-purification tag failed. A successful purification method is based on preparative SDS/PAGE and electrodialysis. From 1 g cells we typically purified 13.5 mg fusion protein with a PLN content of 2.8 mg. We genetically inserted an enterokinase (EK) protease site just in front of the PLN sequence and demonstrated the proteolytical liberation of PLN from the carrier protein. The approach described represents a substantial advancement in PLN expression and purification. 相似文献