全文获取类型
收费全文 | 121905篇 |
免费 | 14436篇 |
国内免费 | 6040篇 |
专业分类
电工技术 | 9430篇 |
技术理论 | 15篇 |
综合类 | 8783篇 |
化学工业 | 18519篇 |
金属工艺 | 7447篇 |
机械仪表 | 8274篇 |
建筑科学 | 9732篇 |
矿业工程 | 4187篇 |
能源动力 | 3935篇 |
轻工业 | 8251篇 |
水利工程 | 2787篇 |
石油天然气 | 6207篇 |
武器工业 | 1341篇 |
无线电 | 14503篇 |
一般工业技术 | 14127篇 |
冶金工业 | 5469篇 |
原子能技术 | 1844篇 |
自动化技术 | 17530篇 |
出版年
2025年 | 23篇 |
2024年 | 1877篇 |
2023年 | 2763篇 |
2022年 | 4643篇 |
2021年 | 6179篇 |
2020年 | 4768篇 |
2019年 | 3672篇 |
2018年 | 4172篇 |
2017年 | 4509篇 |
2016年 | 4232篇 |
2015年 | 5658篇 |
2014年 | 6863篇 |
2013年 | 8029篇 |
2012年 | 9022篇 |
2011年 | 9516篇 |
2010年 | 8205篇 |
2009年 | 7762篇 |
2008年 | 7438篇 |
2007年 | 6841篇 |
2006年 | 6436篇 |
2005年 | 5345篇 |
2004年 | 3777篇 |
2003年 | 3071篇 |
2002年 | 3011篇 |
2001年 | 2537篇 |
2000年 | 2192篇 |
1999年 | 2064篇 |
1998年 | 1477篇 |
1997年 | 1174篇 |
1996年 | 1168篇 |
1995年 | 919篇 |
1994年 | 702篇 |
1993年 | 554篇 |
1992年 | 450篇 |
1991年 | 293篇 |
1990年 | 239篇 |
1989年 | 168篇 |
1988年 | 177篇 |
1987年 | 91篇 |
1986年 | 91篇 |
1985年 | 56篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The iron rhenate was compounded by chemical method, which may be generated during wear process of Fe-Re alloys at elevated
temperature. The friction coefficient of iron rhenate has been determined by a pin-on-disc device. The results show that iron
rhenate plays role of lubricating at RT-600 °C. The lubricating behavior is related to the matching pairs. The hardness of
the materials of matching pairs, compatibility of iron rhenate with materials of matching pairs and surface roughness of disc
affect the lubricating behavior of iron rhenate mostly. The principle of matching pairs is proposed.
Project supported by the National Natural Science Foundation of China
Synopsis of the first author Xiong Dangsheng. associated professor, born in 1960. Current research fields include high-temperature self-lubricating alloys
and tribological properties of material. 相似文献
32.
33.
ChenJianrong PengJianqin 《中国油气》2002,9(1):34-36
China has formulated a series of preferential taxation policies for the country 's petroleum enterprises. Those state policies are the important factors influencing reform and development of petroleum enterprises. The taxes turned over to the State by CNPC in 1998, 1999 and 2000 are 31.4 billion yuan, 31.7 billion yuan and 41 billion yuan respectively, accounting for 11.64 percent, 9.06 percent and 10.15 percent of the annual sales income.With China 's entry into WTO, it is necessary for t… 相似文献
34.
35.
Peng Dangcong Jin Qiting 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,58(1):89-93
The anaerobic digestion of alkaline black liquor from a cereal straw pulping mill was studied in batch (serum bottles) and continuous systems (up-flow anaerobic sludge blanket reactor—UASB). The batch digestion studies confirmed that lignin and related compounds (LRC) in the alkaline black liquor were the main inhibitory substances and could not be decomposed by anaerobic bacteria. At organic loading rates of 5–10 kg COD m?3 day?1, the UASB reactor achieved 50–60% COD removal efficiencies. Gas production was 2–3 dm3 per dm3 of alkaline black liquor. Two different sludge types were examined in the reactor: granular and cluster-like sludges. Sludge in a cluster, which involved many small granules and flocs, tended to form larger aggregates and possessed good settling ability. 相似文献
36.
37.
Qiyong Han Xiaodong Zhang Dong Chen Pengfei Wang 《Metallurgical and Materials Transactions B》1988,19(4):617-622
The equilibrium Ca3P2(s) = 3[Ca] + 2[P] was studied at 1600 ° by equilibrating liquid iron, saturated with Ca3P2, and contained in a TiN crucible, with Ca vapor. The source of Ca was liquid Ca contained in an Mo crucible, and the vapor
pressure of Ca was varied by varying the position of the Mo crucible in the temperature gradient of a vertical tube furnace.
A least-squares analysis of the data gave and. The simultaneous equilibria CaO(s) = [Ca] + [O] and CaS(s) = [Ca] + [S] were studied at 1600 ° by equilibrating liquid iron, contained in a pressed and sintered CaO-CaS crucible with
Ca vapor. The advantage of this technique is that two equilibrium constants,K
cas andK
cao, and two interaction coefficients, and can be determined from one set of experiments. It was determined that, at 1600 °,K
cas = 5.9 × 10−8
K
cao = 5.5 × 10−9,, and.
Formerly Graduate Students 相似文献
38.
39.
Qiu Jun Wang Yueting Wu Peng Jiang Shan Cui Kaibo Chen Guowei Liu Dongliang Cui Guangwen 《Journal of Porous Materials》2021,28(6):1675-1687
Journal of Porous Materials - The dynamics and thermodynamics of adsorption of hexadecyl ammonium with different numbers of carbon chains in montmorillonite (Mt) with different layer charge density... 相似文献
40.