全文获取类型
收费全文 | 188607篇 |
免费 | 15900篇 |
国内免费 | 8773篇 |
专业分类
电工技术 | 11400篇 |
技术理论 | 19篇 |
综合类 | 14293篇 |
化学工业 | 30670篇 |
金属工艺 | 10620篇 |
机械仪表 | 11202篇 |
建筑科学 | 13796篇 |
矿业工程 | 4842篇 |
能源动力 | 4888篇 |
轻工业 | 16164篇 |
水利工程 | 3782篇 |
石油天然气 | 10086篇 |
武器工业 | 1621篇 |
无线电 | 19948篇 |
一般工业技术 | 23457篇 |
冶金工业 | 9108篇 |
原子能技术 | 2708篇 |
自动化技术 | 24676篇 |
出版年
2024年 | 641篇 |
2023年 | 2731篇 |
2022年 | 5365篇 |
2021年 | 7462篇 |
2020年 | 5683篇 |
2019年 | 4577篇 |
2018年 | 5156篇 |
2017年 | 5729篇 |
2016年 | 5284篇 |
2015年 | 7323篇 |
2014年 | 9334篇 |
2013年 | 10937篇 |
2012年 | 12457篇 |
2011年 | 13583篇 |
2010年 | 11858篇 |
2009年 | 11250篇 |
2008年 | 11177篇 |
2007年 | 10475篇 |
2006年 | 9945篇 |
2005年 | 8167篇 |
2004年 | 6037篇 |
2003年 | 5315篇 |
2002年 | 5340篇 |
2001年 | 4642篇 |
2000年 | 4105篇 |
1999年 | 3976篇 |
1998年 | 3131篇 |
1997年 | 2520篇 |
1996年 | 2401篇 |
1995年 | 1930篇 |
1994年 | 1656篇 |
1993年 | 1204篇 |
1992年 | 1011篇 |
1991年 | 802篇 |
1990年 | 701篇 |
1989年 | 675篇 |
1988年 | 525篇 |
1987年 | 434篇 |
1986年 | 404篇 |
1985年 | 356篇 |
1984年 | 348篇 |
1983年 | 327篇 |
1978年 | 364篇 |
1977年 | 343篇 |
1976年 | 362篇 |
1975年 | 331篇 |
1974年 | 405篇 |
1973年 | 382篇 |
1972年 | 363篇 |
1971年 | 336篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献
32.
大型综合室内亲子乐园属于高大空间,设有游乐设施和游戏的特殊性使得对空间的舒适性要求一致,但是送风气流遇阻严重,室内存在较多气流死角,影响室内空气质量和儿童健康。因此其空调设计不仅需要考虑温度、风速的空间均匀度,还要考虑各点的空气龄和PMV-PPD指标。以天津某亲子乐园为研究对象,利用scSTREAM软件对适用于该房间的辐射供冷加新风、置换通风、混合通风三种空调方式的送风效果进行数值模拟分析,从流场的均匀性、人员的热舒适性等方面对模拟结果进行探讨,研究结果表明辐射供冷加新风方式的空间均匀性和PMV指标最佳,混合通风方式的空气龄最小。 相似文献
33.
34.
35.
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process.... 相似文献
36.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献
37.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
38.
39.
Yuanyuan Zhang Haiyan Lu Bing Wang Zhuo Zhang Xiaorong Lin Zhongzheng Chen Bin Li 《International Journal of Food Science & Technology》2015,50(6):1397-1404
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions. 相似文献
40.
Dy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm-white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance. 相似文献