全文获取类型
收费全文 | 1576篇 |
免费 | 46篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 112篇 |
综合类 | 2篇 |
化学工业 | 534篇 |
金属工艺 | 59篇 |
机械仪表 | 56篇 |
建筑科学 | 41篇 |
矿业工程 | 1篇 |
能源动力 | 109篇 |
轻工业 | 118篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 53篇 |
一般工业技术 | 302篇 |
冶金工业 | 29篇 |
原子能技术 | 37篇 |
自动化技术 | 174篇 |
出版年
2023年 | 7篇 |
2022年 | 33篇 |
2021年 | 44篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 16篇 |
2014年 | 31篇 |
2013年 | 81篇 |
2012年 | 61篇 |
2011年 | 119篇 |
2010年 | 69篇 |
2009年 | 75篇 |
2008年 | 85篇 |
2007年 | 61篇 |
2006年 | 55篇 |
2005年 | 62篇 |
2004年 | 48篇 |
2003年 | 52篇 |
2002年 | 42篇 |
2001年 | 34篇 |
2000年 | 25篇 |
1999年 | 32篇 |
1998年 | 41篇 |
1997年 | 39篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1994年 | 38篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有1635条查询结果,搜索用时 15 毫秒
41.
Taizo Miyachi Susumu Kunifuji Hajime Kitakami Koichi Furukawa Akikazu Takeuchi Haruo Yokota 《New Generation Computing》1984,2(4):385-404
In this paper we consider a deductive question-answering system for relational databases as a logic database system, and propose a knowledge assimilation method suitable for such a system. The concept of knowledge assimilation for deductive logic is constructed in an implementable form based on the notion of amalgamating object language and metalanguage. This concept calls for checks to be conducted on four subconcepts, provability, contradiction, redundancy, independency, and their corresponding internal database updates. We have implemented this logic database knowledge assimilation program in PROLOG, a logic programming language, and have found PROLOG suitable for knowledge assimilation implementation. 相似文献
42.
LIU JiangHao FU ZhengYi WANG WeiMin ZHANG JinYong WANG Hao WANG YuCheng LEE SooWohn NIIHARA Koichi 《中国科学:技术科学(英文版)》2014,57(6):1085-1092
The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline ceramics.The densification process of magnesia compact with a particle size of 100 nm was investigated,under the applied pressure of up to 170 MPa,and the temperature range of 1740–2080 K with ultra-high heating rate(above 1700 K/min).High-purity magnesia ceramics with a relative density of 98.8%and an average grain size of 120 nm was obtained at 1740 K,and the grain growth during the densification process was effectively restrained.The characteristic morphology of evaporation-condensation was observed in the compact prepared at 2080 K,which revealed the actual process of mass transfer by gas diffusion.Moreover,the investigation on the microstructure evolution and mechanism of grain growth was carried out,on the basis of as-preserved nanocrystalline ceramics.The result indicated that the grain growth of the nanocrystalline MgO was controlled by the mechanism of evaporation-condensation rather than surface diffusion.Furthermore,the pressure had an influence of restraining the grain growth based on solid diffusion and strengthening the effect of gas diffusion with the increasing temperature.Under the particular conditions,there existed an appropriate temperature for the densification of nanocrystalline magnesia,while the excessive temperature would exaggerate grain growth and impede densification. 相似文献
43.
Shunjiro Ogawa Hideyo Suzuki Masatake Toyoda Yoshio Ito Masahiro Iwaida Hiroko Nonogi Tazu Fuke Kazuo Obara Tadao Adachi Koichi Fujita Makiko Ikuzawa Tetsuo Izumi Takashi Hamano Yukimasa Mitsuhashi Yukio Matsuki 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1979,168(4):293-298
Summary Detection and determination of traces of sulphites in foods was attempted by use of the modified Rankine apparatus and pararosaniline colorimetry. Replacement of alkaline titration reported previously by pararosaniline colorimetry lowered the absolute detection limit from 30 g (titration method) to 2 g. In view of clean analysis, in the color developing system, 0.1 N-sodium hydroxide was used in place of mercuric chloride solution commonly used as an absorbant of sulphites. In order to prevent oxidative decomposition of sulphites during operation, nitrogen gas was used as carrier instead of air. Dimedone and sodium azide were used for the elimination of aldehydes and nitrites, respecitvely, in the sample, which will disturb the color development of sulphites with pararosaniline-formaldehyde reagents. With this improved method, it was possible to determine the residual sulphites in frozen peeled shrimps, sugared beans and other foods with low sulphite contents accurately.
Studies on the Analyses of Sulphites in Foods (IV) 相似文献
Colorimetrische Mikrobestimmung von Sulfiten in Lebensmitteln bei Anwendung der modifizierten IV. Rankine Apparatur
Zusammenfassung Geringe Sulfitmengen in Lebensmitteln (geschälte Garnelen, gezuckerte Bohnen) können colorimetrisch bestimmt werden. Die neuentwickelte Methode beruht auf einer Kombination von colorimetrischer Bestimmung mittels p-Rosanilin und der Bestimmungsmethode nach Rankine. Auf diese Weise lassen sich Gehalte von 2 g noch genau bestimmen. Bei der Farbentwicklung wurde das giftige Quecksilbertetrachlorid durch 0.1 n-NaOH ersetzt, anstelle von Luft Stickstoff als Trägergas verwendet und somit eine Oxydation des Sulfits während der Bestimmung vermieden. Da Nitrit und Aldehyde die Farbentwicklung stören, wurde ihr Einfluß durch Dimedon und Natriumazid ausgeschaltet.
Studies on the Analyses of Sulphites in Foods (IV) 相似文献
44.
Experimental study of perforation and cracking of water-filled aluminum tubes impacted by steel spheres 总被引:4,自引:0,他引:4
Water-filled aluminum tubes were subjected to impact by six steel spherical projectiles of different diameters at impact velocities of 40–200 m/s. The effects of the diameter of the steel projectiles and of the material properties of the tubes on cracking and perforation were discussed. Water decreased the wall strength of the aluminum alloy tubes, and the impact velocity at which a steel projectile first passes through the tube wall decreased with increasing diameter of the steel projectile. Using the velocity at which the steel projectile perforates the tube wall, empirical equations of the energies required to perforate the tube wall were derived. Also, the energy balance in the steel projectile during a collision is discussed referring to the pressure history in the filled water and the velocities of the steel projectile before and after collision. 相似文献
45.
Crystal orientation changes of Ag thin films due to the tribo-assisted recrystallization have been studied using grazing incidence X-ray diffraction with synchrotron radiation. After preparation of an Si(111) √3 × √3-Ag surface, a 5-nm-thick Ag film was deposited on the surface at the substrate temperature of 303 K in an ultra-high vacuum chamber. The friction experiments were carried out using a diamond pin-on-plate type tribometer just after the Ag deposition in the same UHV chamber. We found that the coefficient of friction of the Ag films on the Si(111) √3 × √3-Ag surface decreases from 0.07 to 0.03, with increasing reciprocal sliding cycles. In synchronization with the coefficient change, Ag{100} grains are gradually disappearing. As a result, the Ag{111} grains cover the entire surface after 50 sliding cycles. Moreover, we found that the domain size of the Ag{111} grains increases with increasing reciprocal sliding cycles by measuring the rocking curve width. These results directly show that the Ag(111) plane is the sliding plane of friction and the coefficient of friction of Ag films is determined by the fraction of the Ag(111) grains in the Ag films. Moreover, to clarify the reaction between the Ag film and the Si substrate due to the tribo-assisted recrystallization, the substrate strain has been studied by an extremely asymmetric X-ray diffraction technique using synchrotron radiation. 相似文献
46.
Nariaki Sakaba Kazuhiko Iigaki Masaaki Kondo Koichi Emori 《Nuclear Engineering and Design》2004,233(1-3):135
The containment structures of the HTTR consist of the reactor containment vessel, the service area, and the emergency air purification system, which minimise the release of fission products in postulated accidents, which lead to fission product release from the reactor facilities. The reactor containment vessel is designed to withstand the temperature and pressure transients and to be leak-tight in the case of a rupture of the primary concentric hot-gas duct, etc. The pressure inside the service area is maintained at a negative pressure by the emergency air purification system. The emergency air purification system will also remove airborne radioactivity and will maintain a correct pressure in the service area.The leak-tightness characteristics of the containment structures are described in this paper. The measured leakage rates of the reactor containment vessel were enough less than the specified leakage limit of 0.1%/d confirmed during the commissioning tests and annual inspections. The service area was kept in a way that the design pressure becomes well below its allowable limitation by the emergency air purification system, which filters efficiency of particle removal and iodine removal well over the limited values.The obtained data demonstrate that the reactor containment structures were fabricated to minimise the release of fission products in the postulated accidents with fission product release from the reactor facilities. 相似文献
47.
Koichi Uozumi Masatoshi Iizuka Tadashi Inoue Takashi Iwai 《Journal of Nuclear Materials》2004,325(1):34-43
Experiments were conducted on simultaneous recovery of uranium and plutonium electrochemically into laboratory scale liquid cadmium cathodes (LCCs) at different U/Pu ratios in the salt phase, and the influence of the salt composition on the recovered amounts of uranium and plutonium, the morphologies of uranium and plutonium in the LCC, and the behavior of americium, which is present as a decay product of plutonium-241, were examined. As a result, it was shown that there is a threshold in the U/Pu ratio in the salt phase between 1/4.3 and 1/1.73 for the successful simultaneous recovery of uranium and plutonium up to 10 wt% in the LCC at high current efficiencies. In the LCC, uranium and plutonium existed in the forms of intermetallic compounds, (U, Pu)Cd6 and (U, Pu)Cd11, and also pure uranium metal. It was also revealed that americium associates with plutonium according to the separation factor during the LCC operation. 相似文献
48.
The radical polymerization of N‐isopropylacrylamide was carried out in toluene at low temperatures in the presence of silyl alcohols, such as triethylsilanol. Poly(N‐isopropylacrylamide) with a racemo dyad content of 75% was obtained at ? 80 °C with a 4:1 triethylsilanol to monomer ratio loading. NMR analysis suggests that the mechanism for syndiotactic induction, in the presence of silyl alcohols, may be similar to that observed with alkyl alcohols. In this case, a 1:2 complex formation, via hydrogen bonding interactions, leads to the induction of syndiotactic specificity. Copyright © 2012 Society of Chemical Industry 相似文献
49.
Visual management (VM) has become an important management tool for the smooth management of global supply chains. The target of VM systems is to harmonise communication. For example, in the production sector, VM provides solutions for various issues such as the quick detection of an abnormal situation, continuous maintenance of a safe environment, prevention of an operation miss and knowledge sharing. However, the development of VM cases has been uncontrolled, which is considered problematic. A system for the strategic enhancement of VM is necessary. Recognising this need, this study presents a model for the performance evaluation of relevant cases and validates the utility of the model, which is the initial step in developing a strategic enhancement system for VM. 相似文献
50.
Katsunori Yamaura Makiko Ishiwatari Masao Yamamoto Maki Shimada Yuanyuan Bi Koichi Ueno 《Journal of food science》2012,77(12):H262-H267
Abstract: We have previously reported that bilberry anthocyanins exhibit an anti‐pruritic effect in a mouse model of allergic contact dermatitis. It has been reported that anthocyanins are particularly sensitive to thermal treatment and are easily hydrolyzed to anthocyanidins when exposed to high temperatures. The objective of this study was to compare the anti‐pruritic effect of anthocyanin‐rich quality‐controlled bilberry extract and anthocyanidin‐rich degraded extract using a mouse model of allergic contact dermatitis. BALB/c mice with allergic contact dermatitis induced by 4 weeks of repeated application of 2,4,6‐trinitro‐1‐chlorobenzene (TNCB) were administered Bilberon‐25 orally for 4 weeks after sensitization with TNCB. The effect of Bilberon‐25 on pruritus was evaluated by measurement of scratching behavior. RBL‐2H3 mast cells were used to investigate the effect of Bilberon‐25 on degranulation in 48/80‐stimulated mast cells. Compared with nonheated Bilberon‐25, the proportion of anthocyanins in heated Bilberon‐25 decreased, and the proportion of anthocyanidins was increased in heated‐time dependent manner. Treatment with non‐heated Bilberon‐25 significantly attenuated the TNCB‐induced increase in scratching behavior, whereas treatment with 2 h‐heated Bilberon‐25 did not. Moreover, 300 μg/mL nonheated Bilberon‐25 showed significant inhibition of degranulation in RBL‐2H3 mast cells, whereas 2 h‐heated Bilberon‐25 had no effect at any concentration studied. It is assumed that the inhibitory effect of bilberry anthocyanins on pruritus might be mediated, at least in part, by its inhibitory effect on mast cell degranulation. In conclusion, the anthocyanin‐rich but not anthocyanidin‐rich bilberry extract may be a useful dietary supplement for skin diseases involving pruritic symptoms, such as chronic allergic contact dermatitis, atopic dermatitis, and rhinitis. 相似文献