全文获取类型
收费全文 | 68411篇 |
免费 | 5224篇 |
国内免费 | 2682篇 |
学科分类
工业技术 | 76317篇 |
出版年
2024年 | 116篇 |
2023年 | 989篇 |
2022年 | 1425篇 |
2021年 | 2420篇 |
2020年 | 1891篇 |
2019年 | 1720篇 |
2018年 | 1960篇 |
2017年 | 2143篇 |
2016年 | 2000篇 |
2015年 | 2510篇 |
2014年 | 3283篇 |
2013年 | 3978篇 |
2012年 | 4086篇 |
2011年 | 4475篇 |
2010年 | 4017篇 |
2009年 | 3706篇 |
2008年 | 3616篇 |
2007年 | 3533篇 |
2006年 | 3522篇 |
2005年 | 3052篇 |
2004年 | 2310篇 |
2003年 | 2394篇 |
2002年 | 2756篇 |
2001年 | 2284篇 |
2000年 | 1797篇 |
1999年 | 1872篇 |
1998年 | 1618篇 |
1997年 | 1279篇 |
1996年 | 1246篇 |
1995年 | 965篇 |
1994年 | 738篇 |
1993年 | 575篇 |
1992年 | 417篇 |
1991年 | 340篇 |
1990年 | 258篇 |
1989年 | 220篇 |
1988年 | 191篇 |
1987年 | 128篇 |
1986年 | 107篇 |
1985年 | 67篇 |
1984年 | 59篇 |
1983年 | 43篇 |
1982年 | 37篇 |
1981年 | 36篇 |
1980年 | 35篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 16篇 |
1976年 | 21篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Microstructure and Phase Stability of Yttria-Doped Tetragonal Zirconia Polycrystals Heat Treated in Nitrogen Atmosphere 总被引:2,自引:0,他引:2
Tai-Joo Chung Huesup Song Gyeung-Ho Kim Doh-Yeon Kim 《Journal of the American Ceramic Society》1997,80(10):2607-2612
The low-temperature degradation of zirconia (ZrO2 ) that was doped with 3 mol% yttria (Y2 O3 ) (3Y-TZP) was prevented by the heat treatment of sintered specimens in nitrogen. The heat treatment of sintered specimens resulted in a surface layer that was stabilized by nitrogen ions, whereas the interior was only slightly affected by the heat treatment. X-ray diffractometry and transmission electron microscopy analyses revealed that the stabilized surface layer consisted of cubic grains with tetragonal precipitates. Although the presence of the surface layer decreased the strength of the sintered 3Y-TZP, the strength of nitrified specimens was maintained when low-temperature annealing was applied. 相似文献
992.
高硅铸铝合金镀前浸锌液 总被引:3,自引:1,他引:3
针对高硅铸铝件在组成,组织与性能上的特点,研究了8种高硅铝合金镀前浸锌液。用扫描电镜(SEM)观察了8种不同的浸锌液配方浸锌的试片的表面浸锌膜的微观形貌,测定了浸锌后镀镍层与试片的结合力,优选了能获得良好结合力的最佳浸锌液配方。并研究了随浸锌时间的增加,锌晶核的析出与成长的过程,结果表明,当氢氧化钠140g/L,氧化锌14~20g/L、氯化镍1.5g/L时,试片镀镍后结合力良好。发现浸锌液能够溶解铝合金部分组织,并在铝表面造成孔洞,这种孔洞对镀层起着锚链作用,铝合金表面孔洞的均匀分散以及细小锌晶粒的高度弥散是得到良好结合力的前提。 相似文献
993.
994.
995.
Hyun Jin Chung Suk Jin Chung Min Ku Jeon Seong Ihl Woo 《Korean Journal of Chemical Engineering》2006,23(2):329-332
The ((Bi3.5La0.5)Ti3O12(BLT) thin-films used in this study were fabricated on a Pt(111)/SiO2/Si(100) substrate by a Liquid Source Misted Chemical Deposition (LSMCD) technique. X-ray diffraction patterns showed that
the BLT films were crystallized and no other phases were observed when annealed above 650 ‡C. Grain size and remnant polarizations
increased with increase in the annealing temperature, while leakage current densities decreased. The remnant polarizations
(Pr) increased from 2.0 to 4.8 and 19.0 μC/cm2 with increase in the annealing temperature from 650 to 700 and 750 ‡C, respectively.
The BLT films annealed at 700 ‡C in O2 showed a good fatigue resistance of reduced polarization by 10% after 109 switching cycles when 9 V of bipolar voltage was applied at a frequency of 40 kHz. 相似文献
996.
单丝牌号5000S是大庆HDPE装置的主要产品,适用于加工渔网丝、编织袋等产品。作者们讨论了产品的物性参数特点,分析了以往产品质量存在的主要问题。从工艺技术方面对于如何提高5000S产品的优级品率,提高产品的加工性能和使用性能进行了讨论。 相似文献
997.
The methanation of CO2 has been investigated over a special Ru/TiO2 catalyst suggested by Thampi, Kiwi and Graetzel [4]. This paper deals with the analysis of the material and the investigation of the reported photoenhancement of the activity. The catalyst is characterised by in situ UV-VIS spectroscopy and by XPS. Conversion experiments at atmospheric pressure were carried out with and without UV light irradiation. The irradiation increases the conversion significantly. From various experiments it can be shown, however, that this effect is due to a thermal effect and does not involve an intrinsic photochemical step. Localised Ti3+ states sensitise the support to convert visible light into heat resulting in the observed increase in conversion. 相似文献
998.
999.
A simple, inexpensive and one-step synthesis method of metal-containing carbon nanocapsules using an arc discharge in aqueous solution is reported. It was found that Ni, Co and Fe nanoparticles could be in situ encapsulated in carbon shells when the arc was performed respectively in aqueous solutions of NiSO4, CoSO4 and FeSO4. Transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction patterns of selected areas were used to determine the crystalline phase of the metal cores. To explain the formation mechanism of metal-containing carbon nanocapsules, a model of discharge in solution is proposed. This result presents a simply controllable way to synthesize metal-containing carbon nanocapsules. 相似文献
1000.
Jun Yang Jianbao Li Hong Lin Xiaozhan Yang Xuguang Tong Gangfeng Guo 《Journal of Applied Electrochemistry》2006,36(8):945-950
In this paper, we describe the preparation of a porous nanosheet-stacked NiCo2O4 composite electrode using a novel electrophoretic deposition (EPD) calcination method. The effects of the deposition time and voltage, and of the calcination temperature have been investigated. The microstructure of the deposited films in the electrodes before and after calcination has also been investigated. The electrocatalytic properties of the electrodes have been investigated using cyclic voltammetry and polarization curves. The electrode films produced using this new technique have a porous structure composed of stacked hexagonal NiCo2O4 nanosheets. The resulting electrodes exhibit good electrocatalytic properties for water electrolysis. 相似文献