全文获取类型
收费全文 | 63428篇 |
免费 | 6991篇 |
国内免费 | 3532篇 |
专业分类
电工技术 | 4556篇 |
技术理论 | 1篇 |
综合类 | 6741篇 |
化学工业 | 7760篇 |
金属工艺 | 4844篇 |
机械仪表 | 3919篇 |
建筑科学 | 9601篇 |
矿业工程 | 2445篇 |
能源动力 | 855篇 |
轻工业 | 2540篇 |
水利工程 | 1676篇 |
石油天然气 | 1941篇 |
武器工业 | 899篇 |
无线电 | 9563篇 |
一般工业技术 | 6654篇 |
冶金工业 | 3158篇 |
原子能技术 | 342篇 |
自动化技术 | 6456篇 |
出版年
2024年 | 294篇 |
2023年 | 888篇 |
2022年 | 1620篇 |
2021年 | 1975篇 |
2020年 | 1988篇 |
2019年 | 1660篇 |
2018年 | 1699篇 |
2017年 | 2354篇 |
2016年 | 2486篇 |
2015年 | 2723篇 |
2014年 | 3968篇 |
2013年 | 4104篇 |
2012年 | 4824篇 |
2011年 | 4920篇 |
2010年 | 3705篇 |
2009年 | 3600篇 |
2008年 | 3574篇 |
2007年 | 4391篇 |
2006年 | 3856篇 |
2005年 | 3327篇 |
2004年 | 2747篇 |
2003年 | 2263篇 |
2002年 | 1903篇 |
2001年 | 1669篇 |
2000年 | 1372篇 |
1999年 | 1193篇 |
1998年 | 910篇 |
1997年 | 768篇 |
1996年 | 620篇 |
1995年 | 524篇 |
1994年 | 441篇 |
1993年 | 382篇 |
1992年 | 264篇 |
1991年 | 192篇 |
1990年 | 178篇 |
1989年 | 154篇 |
1988年 | 89篇 |
1987年 | 79篇 |
1986年 | 26篇 |
1985年 | 39篇 |
1984年 | 25篇 |
1983年 | 30篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1964年 | 6篇 |
1963年 | 6篇 |
1959年 | 5篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
N. F. Kuschevskaya A. E. Kushchevskii A. I. Oleshko 《Powder Metallurgy and Metal Ceramics》2006,45(3-4):202-206
The possibility of utilizing nanopowders of iron and Fe-Co-Ni produced bu a thermochemical method in the fabrication of sealing
composition materials is investigated. It is established that such hermetic sealing composition materials function reliably
under extremal conditions and guarantee elevated strength of adhesion to the surface of the metal and high corrosion and temperature
stability.
__________
Translated from Poroshkaya Metallurgiya, Nos. 3–4(448), pp. 112–117, March–April, 2006. 相似文献
13.
Sei-Ichi Aiba Masato Izume Norihiko Minoura Yukihiko Fujiwara 《Polymer International》1985,17(1):38-40
Chitin membrane was prepared by casting a N,N-dimethyl acetamide, N-methyl 2-pyrrolidone and lithium chloride (DMA-NMP-LiCl)solution of chitin and coagulating with several media. The effect of the coagulants on membrane formation was studied. 2-Propanol was found to be more favourable than methanol, ethanol, acetone and mixtures of 2-propanol and water. The membrane obtained in 2-propanol was subjected to annealing. Annealing made the membrane dense and strong. The tensile strength of the membrane annealed at 145°C for 2hr was about twice that of an unannealed membrane. The solute permeability of the annealed membranes was lower than that of the original one. These phenomena could be clearly interpreted in terms of crystallinity. 相似文献
14.
二次型时频分析技术的开发与应用 总被引:1,自引:1,他引:0
基于二次型的时频分析是高分辨率时频分析技术的有效方法之一,该项技术能够有效反映时变信号的频谱特性,具有分辨率高、能量集中和跟踪瞬时频率的特点。从时变信号的特点出发,阐述了二次型时频分析技术的基本方法原理,采用正演模型分析验证了该方法的有效性,并在实际地震资料中应用于识别物源方向、划分沉积相带、预测储层结构以及相对厚度等诸多方面,均取得了较好的效果。 相似文献
15.
T. MATTILA-SANDHOLM T. ALI-VEHMAS G. WIRTANEN U. RÖNNER M. SANDHOLM 《International Journal of Food Science & Technology》1991,26(3):325-336
Automated monitoring of the microbiological quality of heat-processed foods by the resazurin reduction test was applied to microtitration plate incubator-fluorimeter technology. The appearance and disappearance of the fluorescing peak of resorufin was monitored on microtitration trays. Pasteurized or ultra-high temperature-treated starch-based soup was used as the model food system. Bacillus subtilis spores (ultra-high temperature treatment) and vegetative cells of Enterococcus faecalis (pasteurization) were inoculated into the soup before the heat treatment at levels which resulted in some survival. The timing of appearance of maximum fluorescence correlated with the number of bacteria in pre-incubated samples. Automated resazurin-reduction fluorimetry was compared with conventional plating, turbidometry and microcolony count by the direct epifluorescent filter technique. The results of the resazurin test correlated well with those of all the other methods tested. Fluorimetry had the advantage that the results could be read within 1–5h and the reproducibility was superior to the other methods. 相似文献
16.
Jorge Soriano-Santos† Setsuko Iwabuchi Kenshiro Fujimoto 《International Journal of Food Science & Technology》1992,27(3):337-346
Nitrogen was extracted more efficiently from amaranth seed with 0.04 M Na2 SO4 (5% w/v) than with either 0.09 M or 0.17 M NaCl (5% or 10% w/v), despite both solutions having the same ionic strength (μ= 1). Solubility of saline soluble proteins (albumin ± globulin) was very poor in either water or 1M NaCl, but increased in 0.4M NaCl at alkaline pH between 7 and 10. Globulins were very soluble in 0.4M NaCl at a pH 9. Albumin was the main storage protein. Saline soluble proteins formed very weak gels. 相似文献
17.
18.
19.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献
20.
卸荷裂隙在水利水电工程建设中的危害 总被引:3,自引:0,他引:3
卸荷裂隙是对水工建筑物稳定最不利的软弱结构面之一。文中较系统地介绍了这种结构面的特点、分布规律、形成的力学机理、对工程的危害、勘查方法及处理措施。 相似文献