全文获取类型
收费全文 | 56322篇 |
免费 | 6988篇 |
国内免费 | 3578篇 |
专业分类
电工技术 | 5142篇 |
综合类 | 4115篇 |
化学工业 | 14955篇 |
金属工艺 | 4186篇 |
机械仪表 | 2920篇 |
建筑科学 | 4151篇 |
矿业工程 | 781篇 |
能源动力 | 4739篇 |
轻工业 | 2505篇 |
水利工程 | 692篇 |
石油天然气 | 2158篇 |
武器工业 | 859篇 |
无线电 | 4813篇 |
一般工业技术 | 7928篇 |
冶金工业 | 1765篇 |
原子能技术 | 809篇 |
自动化技术 | 4370篇 |
出版年
2024年 | 303篇 |
2023年 | 1141篇 |
2022年 | 1719篇 |
2021年 | 2134篇 |
2020年 | 2374篇 |
2019年 | 2062篇 |
2018年 | 1895篇 |
2017年 | 2327篇 |
2016年 | 2351篇 |
2015年 | 2403篇 |
2014年 | 3346篇 |
2013年 | 3838篇 |
2012年 | 3961篇 |
2011年 | 4110篇 |
2010年 | 3046篇 |
2009年 | 3220篇 |
2008年 | 2750篇 |
2007年 | 3483篇 |
2006年 | 3287篇 |
2005年 | 2535篇 |
2004年 | 2188篇 |
2003年 | 1854篇 |
2002年 | 1672篇 |
2001年 | 1414篇 |
2000年 | 1260篇 |
1999年 | 982篇 |
1998年 | 859篇 |
1997年 | 771篇 |
1996年 | 628篇 |
1995年 | 507篇 |
1994年 | 413篇 |
1993年 | 311篇 |
1992年 | 327篇 |
1991年 | 270篇 |
1990年 | 237篇 |
1989年 | 191篇 |
1988年 | 147篇 |
1987年 | 112篇 |
1986年 | 84篇 |
1985年 | 84篇 |
1984年 | 79篇 |
1983年 | 52篇 |
1982年 | 62篇 |
1981年 | 34篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1959年 | 7篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
12.
Aniruddha Nag Mohammed Asif Ali Jiabei Zhou Makoto Ogawa Tatsuo Kaneko 《大分子材料与工程》2021,306(11):2100459
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5-benzimidazole)s are rigid-rod polymers to show ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole-co-amide)s are synthesized from two biobased monomers, 3,4-diaminobenzoic acid and a semirigid comonomer, 4-aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high-performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc. 相似文献
13.
Hydrogen production via ammonia decomposition catalyzed by Ni/M–Mo–N (M = Ni,Co) bimetallic nitrides
《International Journal of Hydrogen Energy》2022,47(77):32893-32902
This study demonstrates the significant improvement in NH3 decomposition using Ni-decorated M–Mo–N-based catalysts (M = Co and Ni) compared with conventional catalysts. Catalysts are prepared using a mixture of the corresponding metal salts and hexamethylenetetramine, and the impregnation method is used to decorate the Ni-particles on the catalysts. Among all the samples, 10 wt% Ni-decorated Co3Mo3N exhibits the highest NH3 conversion rate (71%) at 500 °C, and the performance remains stable for 30 h of long-term testing. According to the gas chromatography measurements, the H2/N2 ratio is approximately 3 in all cases, which is consistent with the theoretical value. X-ray photoelectron spectroscopy results show that Co3Mo3N possesses the highest NH3 conversion efficiency because of the weaker binding energy of Mo–N. Furthermore, Co3Mo3N exhibits a stronger Lewis acidity and higher NH3 decomposition, which is attributed to the easy breaking of the N–H bond on the Co3Mo3N surface. 相似文献
14.
Lindsey Yue Alicia Bayon Wojciech Lipiński 《American Institute of Chemical Engineers》2021,67(8):e17267
The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size. 相似文献
15.
华治国 《混凝土与水泥制品》2020,(6):70-72
选择了几份典型的外墙外保温系统标准,通过对这几份标准中胶粘剂和抹面胶浆的成型和检测方法的比较,分析了现有检测技术的优劣,并结合工作实践提出了建议。 相似文献
16.
乳腺疾病已严重危害女性身心健康,其中乳腺癌更位居全球范围内女性癌症发病率和死亡率首位,因此乳腺癌的早期发现意义重大。传统结构影像学早期检测疾病具有一定局限性,而红外热成像作为功能成像技术可为乳腺癌的早期筛查提供有效线索。因此本文主要就红外热成像在乳腺疾病的早期检测及预后评估的应用价值进行综述。 相似文献
17.
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
18.
In this research, we propose a novel framework referred to as collective game behavior decomposition where complex collective behavior is assumed to be generated by aggregation of several groups of agents following different strategies and complexity emerges from collaboration and competition of individuals. The strategy of an agent is modeled by certain simple game theory models with limited information. Genetic algorithms are used to obtain the optimal collective behavior decomposition based on history data. The trained model can be used for collective behavior prediction. For modeling individual behavior, two simple games, the minority game and mixed game are investigated in experiments on the real-world stock prices and foreign-exchange rate. Experimental results are presented to show the effectiveness of the new proposed model. 相似文献
19.
活塞环在内燃机中有着支撑、密闭、储油、导热的作用,内燃机活塞环制备材料应该具备优良的加工性能、耐高温、耐腐蚀、导热性好且具有良好的强韧性,较好的与气缸材料表面的磨合性能。球墨铸铁和专用钢材已经成为制备内燃机活塞环的基础材料,目前国内外采用多种表面处理技术比如:镀铬、氮化、PVD与CVD镀膜、喷钼、喷涂陶瓷层等表面处理工艺进行表面改性,提高内燃机活塞环的使用寿命和使用性能。需要不断研究和开发新的内燃机活塞环的表面处理技术来满足实际生产和应用中内燃机越来越高的要求。 相似文献
20.