全文获取类型
收费全文 | 18302篇 |
免费 | 1960篇 |
国内免费 | 1200篇 |
专业分类
电工技术 | 1553篇 |
综合类 | 1869篇 |
化学工业 | 1918篇 |
金属工艺 | 1833篇 |
机械仪表 | 1823篇 |
建筑科学 | 1260篇 |
矿业工程 | 1369篇 |
能源动力 | 716篇 |
轻工业 | 1199篇 |
水利工程 | 640篇 |
石油天然气 | 761篇 |
武器工业 | 223篇 |
无线电 | 1350篇 |
一般工业技术 | 2075篇 |
冶金工业 | 606篇 |
原子能技术 | 211篇 |
自动化技术 | 2056篇 |
出版年
2024年 | 59篇 |
2023年 | 257篇 |
2022年 | 502篇 |
2021年 | 556篇 |
2020年 | 624篇 |
2019年 | 524篇 |
2018年 | 533篇 |
2017年 | 671篇 |
2016年 | 771篇 |
2015年 | 792篇 |
2014年 | 1199篇 |
2013年 | 1264篇 |
2012年 | 1392篇 |
2011年 | 1484篇 |
2010年 | 1164篇 |
2009年 | 1129篇 |
2008年 | 932篇 |
2007年 | 1247篇 |
2006年 | 1076篇 |
2005年 | 887篇 |
2004年 | 722篇 |
2003年 | 601篇 |
2002年 | 522篇 |
2001年 | 434篇 |
2000年 | 391篇 |
1999年 | 331篇 |
1998年 | 218篇 |
1997年 | 226篇 |
1996年 | 194篇 |
1995年 | 141篇 |
1994年 | 132篇 |
1993年 | 84篇 |
1992年 | 83篇 |
1991年 | 58篇 |
1990年 | 57篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文利用最优回归设计“310”方案,研究了黑土地甜菜 Zn、K_2O、B的效果及合理施用问题。得出甜菜块根产量、含糖、产糖量、灰分 K 和有害 N 与 ZnK_2O、B 肥回归关系显著的回归模型,分析了 Zn、K_2O、B 对上述五个指标的效应,明确了 Zn 是影响各项指标的主要因子,并采用频率筛选法,提出了兼顾上述五项指标的优质高产施肥措施。 相似文献
82.
Color characteristics of Cu-Zn-Al alloys 总被引:4,自引:0,他引:4
COLORCHARACTERISTICSOFCu-Zn-AlALLOYS ̄①Li,Baomian;Zhang,Xiuhua(ShenyangInstituteofGoldTechnology,Shenyang110015)COLORCHARACTER... 相似文献
83.
84.
Structural and electrical properties of brush plated ZnTe films 总被引:1,自引:0,他引:1
Zinc telluride thin films were deposited by the brush plating technique at a potential of −0.90 V (SCE) on conducting glass and titanium substrates at different temperatures in the range 30–90 °C. The films were polycrystalline in nature with peaks corresponding to the cubic phase. Direct band gap of 2.30 eV was observed. XPS studiers indicated the formation of ZnTe. Depth profiling studies indicated a uniform distribution of Zn and Te throughout the entire thickness. EDAX measurements were made on the films and it was found that there was a slight excess of Te. The carrier concentration was found to vary from 1014–1015 cm−3 with increase of substrate temperature. The mobility was found to vary from 5 to 60 cm2 V−1 s−1. 相似文献
85.
随着时间的推移,混凝土的导温系数将发生变化,为了了解参数随时间的变化规律,利用原型观测资料对导温系数进行分段反演,从而拟合出大坝混凝土导温系数随时间的变化规律. 相似文献
86.
87.
组织光学中的Monte Carlo方法 总被引:12,自引:5,他引:7
介绍了Monte Carlo方法产生的背景、基本思想及其在组织光学应用中的重要意义,评述了其在组织光学应用中的研究进展,对其发展趋势作了展望。 相似文献
88.
“Symmetric materials” devices, where both electrodes are made of the same electrochromic materials, allow the in situ study of side reactions. Each transferred charge that is not used for the expected electrochromic reaction will cause a colour change in the whole symmetric device. Two electrochromic materials, WO3 and IrO2, are successively used to show how to obtain information about side reactions such as faradaic efficiency, reversibility and potential limits from the symmetric experiment. This in situ approach with a polymer electrolyte shows significant differences compared to results obtained with studies in aqueous electrolytes. 相似文献
89.
T. Jeevananda Siddaramaiah Taek Su Lee Joong Hee Lee O. M. Samir R. Somashekar 《应用聚合物科学杂志》2008,109(1):200-210
Polyaniline/carboxylated multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c-MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (〈N〉), lattice strain (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and volume of the ordered regions were calculated from the X-ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c-MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c-MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two-probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c-MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
90.
The swelling kinetics curves of structurally defined poly(acrylic acid) hydrogel in bidistilled water at temperatures: 25, 30, 35, 40, and 45°C were determined. The possibility of kinetically explaining the isothermal swelling process by applying the following models: reaction controlled by diffusion, first order chemical reaction kinetics, and second order chemical reaction kinetics, was investigated. It was found that kinetically explaining the swelling process using these methods was limited to only certain parts of the process. The swelling process in bidistilled water was described in full range assuming that the hydrogel's swelling rate was a kinetically controlled reaction by the rate of the movement of reactive interface of hydrogel. Based on that model, the kinetic parameters, activation energy (Ea) and preexponential factor (A), of the swelling process were determined to be Ea = 35 kJ/mol and lnA = 8.6. A possible mechanism of the investigated swelling process was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献