全文获取类型
收费全文 | 40381篇 |
免费 | 4534篇 |
国内免费 | 1889篇 |
专业分类
电工技术 | 1557篇 |
技术理论 | 4篇 |
综合类 | 2845篇 |
化学工业 | 8201篇 |
金属工艺 | 5258篇 |
机械仪表 | 2171篇 |
建筑科学 | 2652篇 |
矿业工程 | 1778篇 |
能源动力 | 1533篇 |
轻工业 | 1967篇 |
水利工程 | 1824篇 |
石油天然气 | 3477篇 |
武器工业 | 241篇 |
无线电 | 2482篇 |
一般工业技术 | 5332篇 |
冶金工业 | 4007篇 |
原子能技术 | 565篇 |
自动化技术 | 910篇 |
出版年
2024年 | 81篇 |
2023年 | 945篇 |
2022年 | 1082篇 |
2021年 | 1520篇 |
2020年 | 1596篇 |
2019年 | 1503篇 |
2018年 | 1193篇 |
2017年 | 1381篇 |
2016年 | 1393篇 |
2015年 | 1390篇 |
2014年 | 2223篇 |
2013年 | 2459篇 |
2012年 | 2703篇 |
2011年 | 2764篇 |
2010年 | 2055篇 |
2009年 | 2155篇 |
2008年 | 1856篇 |
2007年 | 2485篇 |
2006年 | 2397篇 |
2005年 | 2168篇 |
2004年 | 1764篇 |
2003年 | 1771篇 |
2002年 | 1462篇 |
2001年 | 1195篇 |
2000年 | 1101篇 |
1999年 | 857篇 |
1998年 | 642篇 |
1997年 | 475篇 |
1996年 | 471篇 |
1995年 | 354篇 |
1994年 | 301篇 |
1993年 | 204篇 |
1992年 | 179篇 |
1991年 | 133篇 |
1990年 | 108篇 |
1989年 | 102篇 |
1988年 | 57篇 |
1987年 | 48篇 |
1986年 | 35篇 |
1985年 | 47篇 |
1984年 | 44篇 |
1983年 | 35篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
41.
The polymer electrolyte based solid-state lithium metal batteries are the promising candidate for the high-energy electrochemical energy storage with high safety and stability. Moreover, the intrinsic properties of polymer electrolytes and interface contact between electrolyte and electrodes have played critical roles for determining the comprehensive performances of solid-state lithium metal batteries. In this review, the development of polymer electrolytes with the design strategies by functional units adjustments are firstly discussed. Then the interfaces between polymer electrolyte and cathode/anode, including the interface issues, remedy strategies for stabilizing the interface contact and reducing resistances, and the in-situ polymerization method for enhancing the compatibilities and assembling the batteries with favorable performances, have been introduced. Lastly, the perspectives on developing polymer electrolytes by functional units adjustment, and improving interface contact and stability by effective strategies for solid-state lithium metal batteries have been provided. 相似文献
42.
套管屈服强度直接影响套管抗挤压性能,套管在加工孔过程中可能诱发孔眼附近材料发生金属相变,导致套管屈服强度不再均匀分布,进而影响套管抗挤压强度。在相同工况下,对比了P110完整套管和机加工孔套管的抗挤压强度,以此为参照组分析了相变区域面积和相变区域屈服强度对机加工孔套管抗挤压强度的影响。结果表明,机加工孔会改变材料屈服强度,进而影响套管抗挤压性能。随金属相变区域屈服强度减小,机加工孔套管抗挤压强度减弱;当金属相变区域屈服强度增大时,机加工孔套管抗挤压强度增强。且机加工孔套管相变区域面积对机加工孔套管抗挤压强度的影响随相变区域屈服强度增加而逐渐削弱。 相似文献
43.
44.
Xueliang Wang Huiqin Yin Wenguan Liu Guojun Yu Jian He Zhongfeng Tang Long Yan 《工业材料与腐蚀》2020,71(6):931-937
Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn5(OH)8Cl2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively. 相似文献
45.
Hydrogels for absorbing metal ions in wastewater have attracted more attentions in the environmental field especially for recent years. The removal efficiency of hydrogel adsorbents for eliminating metal ions is highly related with the effective contact between adsorbents and adsorbates. However, poor water absorption capacity of the hydrogel adsorbents would restrict on the expose of adsorption sites to the targeted subjects, causing undesirable removal ratio (RR) especially for metal ions at trace level. Thereby, the reported hydrogel adsorbents mainly focus on the removal of high content but not the trace level of metal ions so far. In this work, poly(acrylamide) (PAM)/poly(acrylic acid) (PAA)/Ca(OH)2 composite hydrogel is applied to adsorb trace metal ions. Swelling ratio of such PAM/PAA/Ca(OH)2 gel reaches 2,530 g/g, resulting in effective exposure of active sites and further expected RR for trace metal ions. The RRs of such adsorbent for Cu2+ (initial concentration C0 = 0.064 mg/L), Al3+ (C0 = 0.27 mg/L), Co2+ (C0 = 0.59 mg/L), Cr6+ (C0 = 0.52 mg/L), Mn2+ (C0 = 0.55 mg/L), Ni2+ (C0 = 0.59 mg/L), Zn2+ (C0 = 0.65 mg/L), Ag+ (C0 = 1.08 mg/L), and La3+ (C0 = 1.39 mg/L) are 56.6, 80.8, 41.3, 29.3, 34.6, 44.6, 55.9, 45.8, and 35.5%, respectively. This work broadens the application of hydrogel adsorbent for eliminating trace metal ions from polluted water. 相似文献
46.
47.
48.
针对目前蒸汽吞吐产量预测模型假设条件简单、普适性差等问题,一般采用测试法和类比法综合确定海上稠油油田蒸汽吞吐初期产量。由于目前海上油田通常只开展常规测试,无法直接获得热采开发初期产量。笔者提出海上稠油油田蒸汽吞吐初期产量确定新方法,建立蒸汽吞吐相对于常规开发的初期产量倍数预测模型,通过蒸汽吞吐产量倍数,将常规测试确定的产量转化为蒸汽吞吐产量。研究表明,蒸汽吞吐初期产量倍数主要受储集层渗透率、原油黏度、注入强度、蒸汽干度等因素影响,利用正交试验设计和多元回归等方法,建立海上稠油油田蒸汽吞吐初期产量倍数与油藏地质参数及注入参数之间的非线性预测模型,该模型经实际生产数据验证,预测误差小于5%,可靠性高,能够为海上稠油油田蒸汽吞吐初期产量的确定提供依据。 相似文献
49.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system. 相似文献
50.
稠油油藏出砂冷采技术实践 总被引:9,自引:5,他引:4
套保油田为普通稠油油藏,其开发的难点是常规冷采产能低、递减快,蒸汽吞吐开采注入压力过高破坏隔层导致底水上窜、注入压力过低不能保证注入蒸汽质量导致开采效果差。因此开展出砂冷采试验,经研究及现场试验形成了较完善的配套工艺技术,出砂冷采在套保油田白92块工业化应用,单井日产油达到10~30m^3/d,为常规冷采产量的10~20倍。 相似文献