全文获取类型
收费全文 | 91518篇 |
免费 | 8122篇 |
国内免费 | 3997篇 |
专业分类
电工技术 | 5199篇 |
技术理论 | 9篇 |
综合类 | 5633篇 |
化学工业 | 15412篇 |
金属工艺 | 5403篇 |
机械仪表 | 6055篇 |
建筑科学 | 6430篇 |
矿业工程 | 2807篇 |
能源动力 | 2737篇 |
轻工业 | 5833篇 |
水利工程 | 1400篇 |
石油天然气 | 5477篇 |
武器工业 | 793篇 |
无线电 | 10905篇 |
一般工业技术 | 11945篇 |
冶金工业 | 4722篇 |
原子能技术 | 1153篇 |
自动化技术 | 11724篇 |
出版年
2024年 | 337篇 |
2023年 | 1656篇 |
2022年 | 2479篇 |
2021年 | 4119篇 |
2020年 | 3063篇 |
2019年 | 2663篇 |
2018年 | 2914篇 |
2017年 | 3201篇 |
2016年 | 2938篇 |
2015年 | 3850篇 |
2014年 | 4800篇 |
2013年 | 5772篇 |
2012年 | 6001篇 |
2011年 | 6614篇 |
2010年 | 5389篇 |
2009年 | 5225篇 |
2008年 | 5214篇 |
2007年 | 4817篇 |
2006年 | 4837篇 |
2005年 | 4006篇 |
2004年 | 2856篇 |
2003年 | 2510篇 |
2002年 | 2434篇 |
2001年 | 2112篇 |
2000年 | 2087篇 |
1999年 | 2124篇 |
1998年 | 1764篇 |
1997年 | 1503篇 |
1996年 | 1373篇 |
1995年 | 1090篇 |
1994年 | 887篇 |
1993年 | 596篇 |
1992年 | 488篇 |
1991年 | 389篇 |
1990年 | 332篇 |
1989年 | 282篇 |
1988年 | 209篇 |
1987年 | 141篇 |
1986年 | 107篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 60篇 |
1982年 | 53篇 |
1981年 | 37篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1976年 | 24篇 |
1975年 | 10篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 775 毫秒
101.
Mohammad Reza Gaeeni Morteza Sasani Ghamsari Abbas Majd Abadi Mohammad Hossein Majles Ara Wooje Han Hyung‐Ho Park 《Journal of the American Ceramic Society》2015,98(6):1818-1822
A facile sol–gel procedure has been developed for the synthesis of colloidal alumina nanocrystals. For the first time, optical characterization procedures were employed to study the quantum confinement effects in optical properties of the prepared Al2O3 sol. Accordingly, the hyperbolic band model was used to determine the optical band gap of colloidal alumina nanocrystals. X‐Ray diffraction pattern was used to study the crystallographic phase of the dried gel. Morphological characterization was performed using scanning electron microscopy (SEM). Inductively Coupled Plasma (ICP) emission spectroscopy was used to determination purity of the Al2O3 powder. High‐resolution TEM showed that the diameter of colloidal nanocrystals is about 10 nm. Photoluminescence spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 68% with 300 nm excitation wavelength. The experimental observations confirm that highly stable alumina sol with strong UV emission was synthesized. The mentioned optical properties have not been reported before. 相似文献
102.
AbstractThe reabsorption characteristics of the lignite treated by low and high temperature drying process were addressed in the paper. The information about the moisture form, functional groups, effective water-filled porosities and equilibrium moisture content of the lignite before and after the drying process was investigated using Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and a self-made reabsorption device, respectively. The results show that the low drying temperature (140, 190, 230?°C, 10?min, N2) has little impact on the effective water-filled porosities of the resulted samples, whereas it has a great influence on the main oxygen-containing functional groups, which amount firstly decreases and then increases with the drying temperature increasing. In the case of the lignite samples dried under high-temperature (600, 700, 800?°C, 30?s, N2), the amount of the effective water-filled porosity of the sample decreases and the amount of oxygen-containing functional groups increases as the temperature increasing. The reabsorption capability of the high temperature dried sample is much lower than that of the sample treated under low drying temperature. The reabsorption characteristics of the low-temperature dried samples are affected by the amount of the oxygen-containing functional groups, while the effective water-filled porosity is main factor for the lignite samples derived from high temperature drying process. Moreover, the work gives a good evidence that the high-temperature drying process is an effective choose for lignite upgrading. 相似文献
103.
1,5-己二烯交联烯烃聚合物的合成及其抗剪切稳定性 总被引:1,自引:0,他引:1
以金属配合物为催化剂、1,5-己二烯为交联剂,采用本体聚合法合成了交联超高相对分子质量烯烃类聚合物(简称交联聚合物)。用傅里叶变换红外光谱、核磁共振、凝胶渗透色潜表征交联聚合物的结构和相对分子质量。用旋转黏度计和超声波仪研究了1,5-己二烯用量对交联聚合物溶液表观黏度的影响及交联聚合物的相对分子质量对交联聚合物溶液抗剪切稳定性的影响。实验结果表明,在最佳聚合条件(单体80mL、助催化剂0.4mL、CS-1催化剂0.090g、1,5-己二烯0.40mL、0℃、24 b)下所合成的交联聚合物的重均相对分子质量为7.7×106,数均相对分子质量3.6×106。加入少量1,5-己二烯能提高交联聚合物的抗剪切能力,同时也能提高交联聚合物的相对分子质量。交联聚合物的相对分子质量越大,抗剪切稳定性越好。1,5-己二烯用量约为0.1 mL时(单体40 mL),交联聚合物溶液的表观黏度达到最大值(16.8 mPa·s)。 相似文献
104.
105.
106.
107.
108.
109.
Ye Wan Jun Tan Guangling Song Chuanwei Yan 《Metallurgical and Materials Transactions A》2006,37(7):2313-2316
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that
the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting
finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before. 相似文献
110.
介绍了如何配置与优化水电厂的自动化元件,其配置选型应以可靠实用、结构简单、便于维护为原则,同时还应结合电厂的各种介质特点、设备运行方式、控制方式等因素综合考虑. 相似文献