全文获取类型
收费全文 | 1411篇 |
免费 | 28篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 33篇 |
化学工业 | 236篇 |
金属工艺 | 33篇 |
机械仪表 | 38篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 32篇 |
轻工业 | 124篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 158篇 |
一般工业技术 | 213篇 |
冶金工业 | 419篇 |
原子能技术 | 29篇 |
自动化技术 | 102篇 |
出版年
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 46篇 |
2012年 | 33篇 |
2011年 | 52篇 |
2010年 | 37篇 |
2009年 | 39篇 |
2008年 | 44篇 |
2007年 | 41篇 |
2006年 | 37篇 |
2005年 | 38篇 |
2004年 | 43篇 |
2003年 | 53篇 |
2002年 | 39篇 |
2001年 | 30篇 |
2000年 | 33篇 |
1999年 | 44篇 |
1998年 | 171篇 |
1997年 | 89篇 |
1996年 | 84篇 |
1995年 | 51篇 |
1994年 | 31篇 |
1993年 | 45篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1970年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有1443条查询结果,搜索用时 15 毫秒
101.
Norimasa Nukaga Hirofumi Ono Takuya Shida Hideaki Machida Toshie Suzuki Hiroshi Funakubo 《Integrated ferroelectrics》2013,141(1):215-222
SrBi 2 Ta 2 O 9 thin films were prepared by ECR plasma enhanced metalorganic chemical vapor deposition (ECR-MOCVD) with a liquid-delivery system using one cocktail source without an additional solvent. The strontium-tantalum double alkoxide, Sr{Ta[OC 2 H 4 H(CH 3 ) 2 ](OC 2 H 5 ) 5 } 2 , was dissolved in stabilized trimethyl bismuth, Bi(CH 3 ) 3 / dioxane. This source system has been used in a conventional bubbling system. Deposition rate and the composition of the films were strictly controlled by the concentration and the composition of the cocktail source. Therefore, high reproducibility was realized by using this system. The constituent phase of the stoichiometric SBT film as-deposited at 500 C on a (111)Pt/TiO 2 /SiO 2 /Si substrate was a fluorite phase and transformed to the single phase of SBT by the post annealing at 800 C. It showed almost the same ferroelectricity as the stoichiometric composition film. 相似文献
102.
103.
Ultrafine powders of the ZrO2-SiO2 system prepared by spraying aqueous mixed solutions of ZrO(NO3)2·2H2O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO2 (t-ZrO2) and amorphous SiO2 (a-SiO2).a-SiO2 alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO2 converted to monoclinic ZrO2 (m-ZrO2) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO2 anda-SiO2 exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO2 converted tom-ZrO2, and its amount decreased with an increase in SiO2 content. At 1400° C particle growth occurred, and the round particles of ZrO2 were dispersed in ana-SiO2 glass medium. These results indicate that ZrO2 and SiO2 mutually block particle growth, and that SiO2 contributes to the quenching oft-ZrO2 by keeping the particles of ZrO2 within the critical particle size oft-ZrO2. 相似文献
104.
K Higo Y Kubo Y Iwatani T Ono M Maeda H Hiai T Masuda K Kuribayashi F Zhang TY Lamin A Adachi A Ishimoto 《Canadian Metallurgical Quarterly》1997,71(1):750-754
Fv-4 is a mouse gene that dominantly confers resistance to infection with Friend murine leukemia virus (F-MuLV) (S. Suzuki, Jpn. J. Exp. Med. 45:473-478, 1975). Despite complete resistance to ecotropic MuLV infection in mice carrying the Fv-4 gene, it is known that cells carrying the resistance gene in tissue culture do not always show resistance as extensive as that in vivo (H. Yoshikura and T. Odaka, JNCI 61:461-463, 1978). To investigate the immunological effect on resistance in vivo, we introduced the Fv-4 gene into BALB/c nude mice (Fv-4-/- nude[nu/nu]) by mating them with Fv-4 congenic BALB/c mice (Fv-4r/r nude+/+) and examined the susceptibility of the F2 progeny to F-MuLV. All BALB/c nude mice without the Fv-4 gene (Fv-4-/- nude[nu/nu]) were permissive to F-MuLV and developed erythroleukemia within 2 weeks after virus inoculation. The BALB/c nude mice with the Fv-4 gene (Fv-4r/r nude[nu/nu]) did not develop leukemia, and no or little virus was detected in the spleen 7 weeks after virus inoculation. The resistance to F-MuLV was dominant in (Fv-4 congenic BALB/c x BALB/c nude) F1 mice with the Fv-4r/- nude(nu/+) genotype as strictly as in (Fv-4 congenic BALB/c x BALB/c) F1 mice with the Fv-4r/- nude+/+ genotype. However, almost all BALB/c nude mice with the Fv-4r/- nude(nu/nu) genotype developed the disease within 7 weeks, and the virus was detected in all of their spleens even in the mice without leukemia. These results show that the resistance caused by the Fv-4 gene is recessive in nude mice and dominant in BALB/c mice. Some immunological effects, perhaps cell-mediated immunity, may play important roles in the resistance to F-MuLV infection in vivo in addition to the dosage effect of the Fv-4 product. 相似文献
105.
Yamazaki S. Ono T. Shimizu H. Kitamura M. Emura K. 《Photonics Technology Letters, IEEE》1990,2(12):914-916
A 2.5-Gb/s CPFSK four-channel FDM transmission experiment has been conducted with a 150-km-long nondispersion-shifted fiber. This system employed a wideband channel space controller, a common polarization control, and a channel identification function. These were indispensable for realizing a high-capacity, coherent FDM trunk line system. The results of the experiment confirm the feasibility of trunk line systems with over 160-Gb/s capacity 相似文献
106.
HY zeolite is a highly active catalyst for the vapor-phase N-alkylation of pyrazoles with alcohols. For example, the reactions
of pyrazole and 4-methylpyrazole with methanol over HY afford N-methylpyrazole and 1,4-dimethylpyrazole, respectively, in
a 100% yield at 573 K.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
107.
New Point Estimates for Probability Moments 总被引:2,自引:0,他引:2
There are many areas of structural safety and structural dynamics in which it is often desirable to compute the first few statistical moments of a function of random variables. The usual approximation is by the Taylor expansion method. This approach requires the computation of derivatives. In order to avoid the computation of derivatives, point estimates for probability moments have been proposed. However, the accuracy is quite low, and sometimes, the estimating points may be outside the region in which the random variable is defined. In the present paper, new point estimates for probability moments are proposed, in which increasing the number of estimating points is easier because the estimating points are independent of the random variable in its original space and the use of high-order moments of the random variables is not required. By using this approximation, the practicability and accuracy of point estimates can be much improved. 相似文献
108.
Yoshida Y. Sasaki M. Shibata K. Kawazu Z. Ono K.-I. Nishiguchi H. Yagi T. Nishimura T. 《Quantum Electronics, IEEE Journal of》2005,41(6):828-832
We analyze kink and power saturation phenomena of high power 660-nm laser diodes for DVD-R/RW experimentally. Power-current (P-I) and voltage-current (V-I) characteristics of laser diodes with different cavity lengths were measured. Using these results and thermal resistances, temperature rises caused by self-heating (/spl Delta/T) and the dependence of slope efficiencies on the temperature rise (Se-/spl Delta/T) were calculated. The slope efficiencies decreased linearly with /spl Delta/T and their gradients showed the same value regardless of the cavity length, while they had no systematic dependence on the current. The kinks occurred at the same /spl Delta/T of 30/spl deg/C regardless of the cavity length, while they occurred at different currents. These results indicate that the temperature rise caused by the self-heating is a key parameter for the kink and the saturation power. A method is proposed to calculate the kink and the saturation power using the gradient (Se-/spl Delta/T) and the kink temperature. 相似文献
109.
The superconducting compound Nb3Sn was produced by the reduction of the oxides or hydroxides of niobium and tin. The procedure consists of the following three steps; (i) preparation of the mixed oxides or hydroxides, (ii) direct alloy reduction, and (iii) homogenizing heat treatment of the reduced metal powders. For mixing the two oxides, two methods were tried: the simultaneous precipitation from the aqueous solution and the solidification of the molten oxides. These mixed oxides were reduced by ca!ciunn or magnesium vapour in the temperature range 973 to 1373 K. After calcium or magnesium oxide was removed by leaching the fine compound powder had an A-15 type crystal structure, but showed a relatively low superconducting critical temperature (T
c). The isothermal annealing improvedT
c to 18.0 K. 相似文献
110.