全文获取类型
收费全文 | 1123篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 58篇 |
综合类 | 3篇 |
化学工业 | 302篇 |
金属工艺 | 29篇 |
机械仪表 | 27篇 |
建筑科学 | 24篇 |
能源动力 | 43篇 |
轻工业 | 66篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 56篇 |
一般工业技术 | 227篇 |
冶金工业 | 189篇 |
原子能技术 | 50篇 |
自动化技术 | 74篇 |
出版年
2022年 | 6篇 |
2021年 | 21篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 49篇 |
2012年 | 31篇 |
2011年 | 41篇 |
2010年 | 24篇 |
2009年 | 37篇 |
2008年 | 47篇 |
2007年 | 39篇 |
2006年 | 31篇 |
2005年 | 40篇 |
2004年 | 32篇 |
2003年 | 48篇 |
2002年 | 36篇 |
2001年 | 38篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 90篇 |
1997年 | 51篇 |
1996年 | 31篇 |
1995年 | 39篇 |
1994年 | 37篇 |
1993年 | 37篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有1151条查询结果,搜索用时 15 毫秒
1.
2.
JIAHong-bo CHENBao-xue ZHOUJian-zhong ZHAODe-xir LUHong-liang YUANYi-fang ISOMamoru 《半导体光子学与技术》2004,10(1):21-27
Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32-and 36-wavelengths optical waveguide wavelength-interleave coupler (i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8nm at 1550nm. The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%, while the least through coupling ratios are respectively greater than 98. 2% and 96. 5%. The output differences due to polarization fluctuation are less than 1.7% and 3.2% 相似文献
3.
4.
Nobuhiro Kumada Nobuo Ozawa Nobukazu Kinomura Fumio Muto 《Materials Research Bulletin》1985,20(5):583-589
Pyrochlores of A1?xHxTaO3·nH2O (A=Na,K) were prepared under the hydrothermal conditions. The values of x for these compounds were increased from 0.3 to 0.5 for A=Na and from 0.2 to 0.5 for A=K by treatment with the distilled water. The compounds with x<0.5 were decomposed to a mixture of NaTaO3 and Na2Ta4O11 for A=Na, or to a mixture of KTaO3 and a tetragonal tungsten bronze phase, and those with x=0.5 to a single phase of A2Ta4O11 at elevated temperatures. Below the decomposition temperatures, defect pyrochlores with oxygen vacancies, , were produced. They were hygroscopic, and in the case of A=K and x=0.5 the original phase was recovered by leaving in air for several hours. 相似文献
5.
CD80(B7-1) and CD86(B7-2) co-stimulatory molecules have been reported to activate Th1/Th2 development pathways differentially. It is well known that Langerhans cells (LC), potent antigen-presenting dendritic cells in the epidermis, express several co-stimulatory molecules and that this expression is modulated by several cytokines. Based on the recently reported effect of interferon (IFN)-gamma and interleukin (IL-)-10 on the expression of CD80 and CD86 by LC, we examined the effects of these cytokines on the expression of CD54 (intercellular adhesion molecule-1) and CD40 in addition to CD80 and CD86 on LC, and correlated the expression of each co-stimulatory molecule with antigen presentation for a Th1 clone by cultured LC (cLC) treated with these cytokines. LC cultured for 72 h significantly up-regulated MHC class II antigen expression and all the co-stimulatory molecules were examined. As previously reported, IL-10 or IFN-gamma inhibited the up-regulation of CD80 expression. Granulocyte/macrophage-colony-stimulating factor (GM-CSF) partially restored the suppression of CD80 expression induced by IFN-gamma on cultured LC, while it had virtually no effect on the inhibition induced by IL-10. Antigen presentation for the myoglobin-specific syngeneic Th1 clone by cLC, which were pre-incubated with these cytokines, correlated well with their CD80 expression. In addition, among the antibodies for CD80, CD86, CD28 or CD40, the suppression of the Th1 clone stimulation by LC was found to occur only with anti-CD80 and anti-CD28 antibodies. Finally, we studied the effects of IFN-gamma and IL-10 on GM-CSF production by epidermal keratinocytes (KC). We could show that only IFN-gamma, but not IL-10, suppressed GM-CSF production by KC. These findings suggest that both IFN-gamma and IL-10 suppress antigen presentation by LC for Th1 cells by suppressing their CD80 expression. The inhibitory effect of IFN-gamma on CD80 expression on LC appears to be partially mediated through the suppression of GM-CSF production by KC. 相似文献
6.
7.
Rong-Jun Xie Mamoru Mitomo Kyota Uheda Fang-Fang Xu Yoshio Akimune 《Journal of the American Ceramic Society》2002,85(5):1229-1234
Rare-earth-doped oxynitride or nitride compounds have been reported to be luminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, we report the photoluminescence (PL) spectra of europium-, terbium-, and praseodymium-doped Ca-α-SiAlON ceramics. The highly dense ceramics were prepared by hot pressing at 1750°C for 1 h under 20 MPa in a nitrogen atmosphere. Europium-doped Ca-α-SiAlON displayed a single broad emission band peaking at λ= 550–590 nm depending on the europium concentration. The emission bands in the spectra of europium-doped Ca-α-SiAlONs were assigned to the allowed transition of Eu2+ from the lowest crystal field component of 4 f 6 5 d to 8 S7/2 (4 f 7 ) ground-state level. The emission spectra of terbium- and praseodymium-doped Ca-α-SiAlON ceramics both consisted of several sharp lines, which were attributed to the 5 D4 →7 F j ( j = 3, 4, 5, 6) transitions of Tb3+ and 3 P0 →3 H j ( j = 3, 4, 5) transitions of Pr3+ , respectively. In particular, the terbium-doped α-SiAlON ceramics showed a strong green emission among these phosphors. 相似文献
8.
Phase-separated domains prepared in the two-phase region were dissolved at a temperature in the single-phase region, and their dissolution dynamics was studied by using the time-resolved light scattering (TRLS) technique and a scanning electron microscope (SEM). The time tps of preparation of domains was chosen to be long enough for phase separation to proceed into the late stage. The scattered light intensity at small wavenumbers increased before it attenuated. As tps increased, the increase at smaller wavenumbers became more significant and the peak intensity decreased only slightly with dissolution time. The characteristic wavenumber qm evaluated from TRLS and SEM followed the power-law relation qmt−0.3. 相似文献
9.
A case is presented of a 29-year-old woman with neurofibromatosis, who had a 100 degrees dystrophic kyphosis of the cervical spine and was successfully treated by a one-stage anterior and posterior correction. Anterior distractive and posterior compressive corrections were simultaneously applied keeping the posterior longitudinal ligament intact. The kyphosis was corrected to 42 degrees. Safety and better results of the one-stage correction of kyphosis is based on a concept of shortening the spinal canal. 相似文献
10.
Relatively uniform polymeric microspheres, the coefficients of variation being close to 10%, were obtained by the BPO-initiated suspension polymerization of styrenic monomers. Unlike the conventional stirred-tank system, a particular microporous glass membrane (SPG) provided uniform monomer droplets continuously when monomer was allowed to permeate through the micropores. The monomer droplets were suspended in an aqueous solution containing the stabilizing agents, transferred to a stirred vessel, and polymerized. Up to 10μm spheres, of a far narrower size distribution than those obtained by conventional microsuspension polymerization spheres, were obtained. The initial droplet size and distribution were retained with the successful suppression of secondary particle nucleation by the addition of hydroquinone in the aueous phase. Crosslinked polystyrene spheres were also synthesized in the presence of various low-molecular-weight diluents. While a good solvent, toluene, was not so effective; poor solvents, n-heptane and n-heptane, easily yielded the microporous structure, the specific surface area being as high as 160 m2/g. © 1994 John Wiley & Sons, Inc. 相似文献