全文获取类型
收费全文 | 24480篇 |
免费 | 2198篇 |
国内免费 | 902篇 |
专业分类
电工技术 | 1377篇 |
技术理论 | 3篇 |
综合类 | 1474篇 |
化学工业 | 4364篇 |
金属工艺 | 1224篇 |
机械仪表 | 1527篇 |
建筑科学 | 1993篇 |
矿业工程 | 569篇 |
能源动力 | 722篇 |
轻工业 | 1707篇 |
水利工程 | 434篇 |
石油天然气 | 1272篇 |
武器工业 | 196篇 |
无线电 | 2587篇 |
一般工业技术 | 3488篇 |
冶金工业 | 1330篇 |
原子能技术 | 323篇 |
自动化技术 | 2990篇 |
出版年
2024年 | 137篇 |
2023年 | 444篇 |
2022年 | 761篇 |
2021年 | 1000篇 |
2020年 | 725篇 |
2019年 | 631篇 |
2018年 | 657篇 |
2017年 | 803篇 |
2016年 | 684篇 |
2015年 | 890篇 |
2014年 | 1066篇 |
2013年 | 1347篇 |
2012年 | 1421篇 |
2011年 | 1493篇 |
2010年 | 1272篇 |
2009年 | 1225篇 |
2008年 | 1274篇 |
2007年 | 1205篇 |
2006年 | 1282篇 |
2005年 | 1221篇 |
2004年 | 779篇 |
2003年 | 703篇 |
2002年 | 671篇 |
2001年 | 576篇 |
2000年 | 728篇 |
1999年 | 775篇 |
1998年 | 650篇 |
1997年 | 577篇 |
1996年 | 512篇 |
1995年 | 478篇 |
1994年 | 349篇 |
1993年 | 261篇 |
1992年 | 218篇 |
1991年 | 181篇 |
1990年 | 138篇 |
1989年 | 121篇 |
1988年 | 92篇 |
1987年 | 48篇 |
1986年 | 50篇 |
1985年 | 44篇 |
1984年 | 19篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Fabrication of multi-walled carbon nanotube reinforced polyelectrolyte hollow nanofibers by electrospinning 总被引:1,自引:0,他引:1
Hybrid hollow multi-walled carbon nanotubes (MWCNTs)/polyelectrolytes (PE) nanofibers were prepared by a combination of the electrospinning method and layer-by-layer (LbL) technique. The mixed polystyrene (PS)/MWCNTs nanofibers were obtained by electrospinning method, which were employed as templates to self-assembly multilayered polyelectrolytes by LbL technique. Hollow MWCNTs/PE nanofibers were obtained by selectively removed part of the template: PS, which is confirmed by Raman spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). 相似文献
62.
63.
Jiang Minhong Gu Zhengfei Cheng Gang 《中国稀土学报(英文版)》2005,23(6):723-723
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC. 相似文献
64.
65.
66.
A new technique for the preparation of CuI nanoparticles from CuSO4 and KI ethanol solutions has been developed. Preparation conditions were optimized through a series of experiments. Under
these conditions, the yield of CuI reached 95.39%. The product was characterized and the reaction kinetics was studied. The
results show that the product takes a roughly spherical shape with an average particle size of less then 50 nm. The activation
energy of the formation of CuI is found to be E
a = 0.58 × 102 kJ/mol, and the preexponential factor in the Arrhenius equation is k
0 = 7.43 × 1016 mol/(l s).
The text was submitted by the authors in English. 相似文献
67.
68.
The combination of the chemical aggressivity of water and lead piping, as is well known, can cause severe cases of lead poisoning in those who consume such water. After a great number of observations and epidemiological studies which have strongly incriminated this metal in a wide range of pathologic conditions, other materials have been gradually substituted for lead; however, the problem remains.In compliance with a European Directive to survey the risk of lead poisoning (Council Directive, 1977), a random sample of 321 residents was selected from the Vosgian Mountains of France. This region is noted for its high incidence of cases of lead poisoning: 150 reported during 8 months in 1983 (Barbier et al., 1983).During the course of a health evaluation, a blood sample was taken from each subject for lead analysis. At the same time, a sample of tap-water (after running for 5 s) was taken from each subject home. Both lead analyses (blood and water) were performed by electrothermal atomization-atomic absorption spectrophotometry. Because of the log-normality of the distributions of the blood lead levels and the concentrations of lead in the drinking water, a logarithmic transformation was performed so that the results are expressed as the geometric mean, which for the amount of lead in the drinking water of our sample was found to be 0.16 mg l?1.Among the subjects of this study, 28% are served by water containing more than 0.10 mg l?1 of lead (the standard for France) and 48% by water containing more than 0.05 mg l?1 (the European and WHO standard). In concurrence with numerous authors, our study indicates that, among our subjects, the blood lead level is much higher in men than in women (geometric means 22.9 and 15.0 μg dl?1 respectively); this difference is highly significant (t-test:P < 0.001). Table 1 summarizes the results, by sex, obtained in this region compared with those from a study (Huel, 1982) concerning an urban French population whose geometric mean blood lead levels were 15.9 μg dl?1 for men and 11.4 μg dl?1 for women. The irrespective of sex, is highly significant (P < 0.001). Table 2 shows the significance of the relation between these subjects, high blood lead levels and the concentration of lead in their drinking water, while Fig. 1 shows that for contamination levels up to 0.02 mg l?1 of lead in water, the blood lead level remains relatively stable, while above this apparent “threshold” value, the blood lead level begins to increase finally reaching quite high values in response to high contamination levels, suggesting a direct translation of increases in the water above the 0.02 mg l?1 level to increases in the blood. 相似文献
69.
Xinying. Lu Kaiming. Liang Shouren. Gu Yankang. Zheng Hongsheng. Fang 《Journal of Materials Science》1997,32(24):6653-6656
The effect of oxygen vacancy on the stability of phase structures and phase transformation of zirconia at low temperatures
was studied using an electrochemical technique. It is suggested that the decrease of oxygen vacancies decreases the stability
of metastable tetragonal zirconia and promotes its transformation to the monoclinic phase.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
70.