全文获取类型
收费全文 | 1801篇 |
免费 | 48篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 116篇 |
综合类 | 3篇 |
化学工业 | 460篇 |
金属工艺 | 44篇 |
机械仪表 | 37篇 |
建筑科学 | 33篇 |
矿业工程 | 1篇 |
能源动力 | 136篇 |
轻工业 | 123篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 139篇 |
一般工业技术 | 302篇 |
冶金工业 | 268篇 |
原子能技术 | 71篇 |
自动化技术 | 117篇 |
出版年
2023年 | 11篇 |
2022年 | 22篇 |
2021年 | 38篇 |
2020年 | 23篇 |
2019年 | 21篇 |
2018年 | 29篇 |
2017年 | 22篇 |
2016年 | 44篇 |
2015年 | 25篇 |
2014年 | 56篇 |
2013年 | 98篇 |
2012年 | 75篇 |
2011年 | 97篇 |
2010年 | 70篇 |
2009年 | 69篇 |
2008年 | 83篇 |
2007年 | 76篇 |
2006年 | 77篇 |
2005年 | 53篇 |
2004年 | 54篇 |
2003年 | 55篇 |
2002年 | 38篇 |
2001年 | 40篇 |
2000年 | 33篇 |
1999年 | 44篇 |
1998年 | 100篇 |
1997年 | 83篇 |
1996年 | 47篇 |
1995年 | 35篇 |
1994年 | 41篇 |
1993年 | 35篇 |
1992年 | 14篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1973年 | 6篇 |
1970年 | 7篇 |
排序方式: 共有1853条查询结果,搜索用时 393 毫秒
1.
Hiromi Eba Yuki Masuzoe Toru Sugihara Hayao Yagi Tian Liu 《International Journal of Hydrogen Energy》2021,46(18):10642-10652
Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide. 相似文献
2.
Tatsuro Tanaka Yoshifumi Maeda Shinji Yamamoto Toru Iwao 《Electrical Engineering in Japan》2019,207(1):15-23
The arc welding has been used in various welding methods because it is inexpensive and high in strength after welding. However, it is a problem that accidents such as collapse of the bridge occur because of the welding defects. The welding of low cost and high productivity is required without the welding defects. The pulsed TIG welding is inexpensive and capable of high‐quality welding. The electromagnetic force contributing to penetration changes because the transient response of arc temperature and iron vapor generated from anode occurs. However, the analysis of pulsed TIG welding with metal vapor has been elucidated only metal vapor concentration near anode with transient phenomenon and heat flux. Thus, the theoretical elucidation of penetration depth with control factor has not been researched. In this paper, the contribution of metal vapor mass at the periphery part of pulsed arc to the electromagnetic force in the weld pool is elucidated. As a result, the iron vapor mass at periphery part decreased with increasing the frequency. The iron vapor was stagnated at axial center within one cycle. The electromagnetic force to the penetration depth direction in weld pool increased at axial center. Therefore, the metal vapor mass at periphery part plays an important role for the electromagnetic force increment at axial center. 相似文献
3.
4.
In a bending load test for brittle materials, such as ceramics for spacecraft and aircraft, decreasing the number of test specimens required is a crucial problem. This paper discusses the effectiveness of using the information of both fracture stress and fracture location to decrease the number of specimens required to obtain the same precision as the Weibull estimator. The following results were obtained: It was found that by adding the fracture location information, the precision of the Weibull parameter estimation under the optimal design became 1.5–1.9 times better compared with the case of using only the fracture stresses. This means the number of samples necessary to attain the same precision becomes 1/1.5–1/1.9. Tables and figures which give information on the number of samples necessary to attain the required precision are given. 相似文献
5.
6.
Theoretical analysis based on the calculation of phase diagrams was employed for Fe-Si-Co and Fe-Si-Al ordering systems to
clarify the necessity for the occurrence of phase separation in Fe-base ternary ordering systems. The free energy of Fe-base
ternary ordering alloys where B2 and D03 ordered structures are formed is evaluated statistically using a pairwise interaction approximation up to second nearest
neighbours, taking into account not only the atomic interaction but also the magnetic interaction, based on the Bragg-Williams-Gorsky
model. The calculated phase diagrams are consistent with the experimentally obtained ones. The phase diagram calculation in
this work is useful to predict the equilibrium states of the ternary ordering systems. The phase separation in ordering alloys
is caused by the contribution of excess free energies due to ordering. The influences of ferromagnetism on the two-phase regions
are also demonstrated. 相似文献
7.
8.
S. Matsuo Y. Mizuguchi Y. Tanaka H. Kubota R. Yamamoto 《International Journal of Thermophysics》1996,17(2):441-454
Densities of aqueous of 1,4-dioxane have been measured at temperatures from 298 to 348 K and at pressures up to 40 MPa by a vibrating-tube method. Molar volumes obtained with an estimated uncertainty of ±0.2°,% are correlated with pressure by the Tait equation within the experimental uncertainty. Pressure and composition dependences of the excess molar volume, partial molar volume, and isothermal compressibility are determined and they are compared with those of other aqueous solutions. 相似文献
9.
10.
Ganglioside GT1b and, to a lesser extent, GD3, enhanced phosphorylation of a 36 kDa protein (the substrate of protein kinase
C) in the particulate fraction from bovine mammary gland. Sialic acids, asialogangliosides, and GM3 were without effect, and
GD1a conversely inhibited phosphorylation of the 36 kDa protein. The enhanced phosphorylation by GT1b required the simultaneous
presence of phosphatidylserine (PS) and Ca2+. The 36 kDa protein reacted with anti-annexin I in Western blot analysis. Addition of purified annexin I to the reaction
mixture containing the particulate fraction increased the extent of phosphorylated 36 kDa protein, and the phosphorylation
was further enhanced by GT1b. The enhanced phosphorylation of annexin I by GT1b was also dependent on PS and Ca2+. When annexin I was phosphorylated by purified protein kinase C, GT1b inhibited the annexin I phosphorylation. Addition of
epidermal growth factor or insulin to the particulate fraction had little effect on the enhancement. These results suggest
that an enzyme or enzymes other than protein kinase C, epidermal growth factor receptor kinase, or insulin receptor kinase
is responsible for the GT1b- and GD3-enhanced phosphorylation of annexin I in the presence of PS and Ca2+. 相似文献