全文获取类型
收费全文 | 1587篇 |
免费 | 48篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 98篇 |
综合类 | 2篇 |
化学工业 | 405篇 |
金属工艺 | 63篇 |
机械仪表 | 38篇 |
建筑科学 | 28篇 |
能源动力 | 79篇 |
轻工业 | 135篇 |
水利工程 | 4篇 |
无线电 | 114篇 |
一般工业技术 | 255篇 |
冶金工业 | 186篇 |
原子能技术 | 35篇 |
自动化技术 | 199篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 32篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 38篇 |
2017年 | 34篇 |
2016年 | 42篇 |
2015年 | 25篇 |
2014年 | 54篇 |
2013年 | 87篇 |
2012年 | 83篇 |
2011年 | 97篇 |
2010年 | 68篇 |
2009年 | 82篇 |
2008年 | 94篇 |
2007年 | 63篇 |
2006年 | 62篇 |
2005年 | 59篇 |
2004年 | 61篇 |
2003年 | 44篇 |
2002年 | 42篇 |
2001年 | 27篇 |
2000年 | 20篇 |
1999年 | 37篇 |
1998年 | 89篇 |
1997年 | 47篇 |
1996年 | 38篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 26篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1970年 | 3篇 |
排序方式: 共有1641条查询结果,搜索用时 31 毫秒
1.
Manjin Kim Qinfen Gu Tanveer Hussain Yahia Ali Trevor B. Abbott Kazuhiro Nogita 《International Journal of Hydrogen Energy》2021,46(53):27096-27106
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics. 相似文献
2.
Takeshi Kondo Hiroyuki Ito Kazuhide Kusakabe Kazuhiro Ohkawa Kensuke Honda Yasuaki Einaga Akira Fujishima Takeshi Kawai 《Diamond and Related Materials》2008,17(1):48-54
The effect of CF4 plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)63−/4− was also found to be significantly modified after 10 s of CF4 plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (Cdl) of the electrolyte/CF4 plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF4 plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage. 相似文献
3.
4.
Koji Kamei Kunihiko Fujita Eva Jettmar Sen Yoshida Kazuhiro Kuwabara 《Interacting with computers》2002,14(6):438-759
In this paper, we present and discuss Community Organizer, a system designed to support network communities. The main characteristic of Community Organizer is the use of spatial representations for the relationships among community members including the communications exchanged among these members. These spatial representations reflect the degree of closeness of interests and concerns among the members, and are intended to provide users with clues on how to form network communities. In order to investigate the effectiveness of the proposed spatial representations, we conducted experiments with two different versions of the software. One version offered meaningful spatial representations while the other version did not. The subjects who used the former software version felt a greater sense of ‘community’, enjoyed using the software more, and actively used it longer than the subjects using the latter software version (control condition). These results indicated that the proposed spatial representations are effective in supporting network community formation. 相似文献
5.
6.
7.
Lipid-Lowering Effect of Eriocitrin, the Main Flavonoid in Lemon Fruit, in Rats on a High-Fat and High-Cholesterol Diet 总被引:2,自引:0,他引:2
Yoshiaki Miyake Eriko Suzuki Satoko Ohya Syuichi Fukumoto Masanori Hiramitsu Kazuhiro Sakaida Toshihiko Osawa Yukio Furuichi 《Journal of food science》2006,71(9):S633-S637
ABSTRACT: Eriocitrin (eriodictyol 7- O -β-rutinoside) is the main flavonoid in lemon fruit. In this study, eriocitrin was investigated for its lowering effect on serum and hepatic lipids in high-fat and high-cholesterol fed rats. Rats in the control group ( N = 6) were fed a 20% lard and 1% cholesterol diet for 21 d, and rats in the 0.35% eriocitrin group ( N = 6) and 0.70% eriocitrin group ( N = 6) were fed a diet supplemented with eriocitrin 0.35% and 0.70%, respectively. The content of hepatic total cholesterol and triglyceride in the eriocitrin group was no different from that of the control group. The total cholesterol, VLDL+LDL, triglyceride, and phospholipid in the serum of the 0.35% eriocitrin group showed significantly lower concentrations than the control group ( P < 0.05), although there was no difference in the HDL concentrations among the groups. The lowering effect of eriocitrin for serum total cholesterol was thought to be caused by a decrease in VLDL+LDL. The 0.35% eriocitrin group was shown to have a significant increase in excretion of fecal bile acid ( P < 0.05) and a tendency for enhanced hepatic m-RNA levels of LDL receptor in comparison with the control group. 相似文献
8.
H Imano H Iso T Tanigawa T Sankai T Ohira M Kudo T Shimamoto S Sato T Okamura M Iida 《Canadian Metallurgical Quarterly》1998,45(6):536-551
To investigate the contribution of the platelet aggregation in the development of cardiovascular diseases, we examined the relation of constitutional and lifestyle variables with platelet aggregation for a total of 306 males aged 50 to 70 in Ikawa town, Akita prefecture (n = 163) and Noichi town, Kochi prefecture (n = 143). The examination of platelet aggregation was completed within 3 hours of obtaining blood samples. We used ADP (Adenosine 5'-diphosphate) as an agonist and obtained PATI (the platelet aggregatory threshold index) by nephelometry. Platelet count, mean platelet volume, white blood cell count, serum fatty acid compositions were also examined and dietary intake of fish, seafood and soy bean foods were inquired using one-week dietary records. PATI indicated a logarithmic normal distribution in both Ikawa and Noichi. The mean of logarithmic transformed PATI (log PATI) was higher in Ikawa than in Noichi. Thus platelet aggregation was lower in Ikawa than in Noichi. According to multiple regression analysis, age, platelet count in platelet rich plasma, mean platelet volume in platelet rich plasma, and white blood cell count were inversely associated with log PATI. Serum arachidonic acid composition tended to be inversely related with log PATI. Serum n3-polyunsaturated fatty acid composition was positively related with log PATI, and log gamma-GTP tended to be positively associated with log PATI. Soy protein intake and cigarette smoking showed no consistent associations with log PATI. This cross-sectional study suggests that serum n3-polyunsaturated fatty acid, and gamma-GTP, as an index of alcohol intake, reduce platelet aggregation while age, white blood cell count, platelet count, mean platelet volume, and serum arachidonic acid raise platelet aggregation. 相似文献
9.
H Kusaba J Kudo T Kuruma R Nagashima M Ra T Mori Y Kaji H Ishibashi Y Niho Y Baba 《Canadian Metallurgical Quarterly》1993,84(6):330-333
Cardiotoxicity of interferon-alpha or gamma, such as fatal arrhythmia and myocardial infarction, has been reported. Therefore cardiotoxicity of interferon should be seriously considered before administration for patients with a pre-existing heart disease. We treated a patient with chronic active hepatitis type B, coexisted with Wolff-Parkinson-White syndrome, who has had frequent attacks of paroxysmal atrial fibrillation. To prevent the occurrence of fatal arrhythmia with an interferon therapy in this patient, we performed radiofrequency catheter ablation of the Kent bundle. After the successful ablation, we could safely administered recombinant interferon alpha-2b for chronic hepatitis type B. 相似文献
10.
Kazuhiro Arai Yoichi Yamashita Riichiro Mizoguchi 《Expert systems with applications》1992,5(3-4):219-232
System monitoring and diagnosis through signal interpretation are important tasks in many engineering fields. Although monitoring or diagnosis expert systems help human experts a lot, it is not so easy to build a signal interpretation expert system. We have developed two expert systems for speech signal processing. The close analysis of the two systems revealed common functions and modules applicable to wide range of signal interpretation problems. On the basis of the experience, we have developed a shell for signal interpretation expert systems named SSI. In order to evaluate SSI, we also developed two expert systems by using it and obtained satisfactory results. This paper describes the design philosophy and architecture of SSI together with some examples. 相似文献