全文获取类型
收费全文 | 5941篇 |
免费 | 528篇 |
国内免费 | 238篇 |
学科分类
工业技术 | 6707篇 |
出版年
2024年 | 13篇 |
2023年 | 98篇 |
2022年 | 156篇 |
2021年 | 252篇 |
2020年 | 210篇 |
2019年 | 157篇 |
2018年 | 202篇 |
2017年 | 171篇 |
2016年 | 182篇 |
2015年 | 262篇 |
2014年 | 307篇 |
2013年 | 385篇 |
2012年 | 426篇 |
2011年 | 411篇 |
2010年 | 373篇 |
2009年 | 352篇 |
2008年 | 337篇 |
2007年 | 315篇 |
2006年 | 291篇 |
2005年 | 225篇 |
2004年 | 171篇 |
2003年 | 140篇 |
2002年 | 108篇 |
2001年 | 107篇 |
2000年 | 148篇 |
1999年 | 174篇 |
1998年 | 157篇 |
1997年 | 129篇 |
1996年 | 114篇 |
1995年 | 83篇 |
1994年 | 73篇 |
1993年 | 41篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有6707条查询结果,搜索用时 15 毫秒
31.
煤储层物性及特征是煤层气地质理论的重要内容,加强其研究对提高煤层气勘探开发成效至关重要。基于天荣矿地质、煤层气勘探及相关测试等资料,采用地质与煤层气地质理论对该矿二2煤储层物性及特征进行了研究。结果表明:天荣矿二2煤层物理性质良好,生烃物质丰富;煤层含煤性、稳定性、可采性好,煤层气含量和纯度高,可为煤层气开发提供良好对象和气源条件;煤变质程度高,煤中裂隙相对发育,但其渗透性整体较差,渗透率分异显著且普遍低下;煤储层能量较强且分异显著,煤储层压力状态为欠压—超压型,并以正常—超压煤储层压力状态为主,有利于煤层气高产富集。 相似文献
32.
33.
Jin Zou Qi-Jie Zhai Fang-Yu Liu Ke-Ming Liu De-Ping Lu 《Metals and Materials International》2018,24(6):1275-1284
A rotating magnetic field (RMF) was applied in the solidification process of Cu-8Fe alloy. Focus on the mechanism of RMF on the solid solution Fe(Cu) atoms in Cu-8Fe alloy, the influences of RMF on solidification structure, solute distribution, and material properties were discussed. Results show that the solidification behavior of Cu–Fe alloy have influenced through the change of temperature and solute fields in the presence of an applied RMF. The Fe dendrites were refined and transformed to rosettes or spherical grains under forced convection. The solute distribution in Cu-rich phase and Fe-rich phase were changed because of the variation of the supercooling degree and the solidification rate. Further, the variation in solute distribution was impacted the strengthening mechanism and conductive mechanism of the material. 相似文献
34.
Lingyan Yang Yuanxin Zhai Ying Hao Zhanchi Zhu Guosheng Cheng 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(3)
Reducing amyloid‐β (Aβ) accumulation could be a potential therapeutic approach for Alzheimer's disease (AD). Particular functional biomolecules in exosomes vested by the microenvironment in which the original cells resided can be transferred to recipient cells to improve pathological conditions. However, there are few reports addressing whether exosomes derived from cells cultured on scaffolds with varying dimension can reduce Aβ deposition or ameliorate cognitive decline for AD therapy. Herein, both 3D graphene scaffold and 2D graphene film are used as the matrix for human umbilical cord mesenchymal stem cell culture, from which the supernatants are obtained to isolate exosomes. The levels of 195 kinds of miRNAs and proteins, including neprilysin, insulin‐degrading enzyme and heat shock protein 70, in 3D‐cultured exosomes (3D‐Exo) are dramatically different from those obtained from 2D culture. Hence, 3D‐Exo could up‐regulate the expression of α‐secretase and down‐regulate the β‐secretase to reduce Aβ production in both AD pathology cells and transgenic mice, through their special cargo. With rescuing Aβ pathology, 3D‐Exo exerts enhanced therapeutic effects on ameliorating the memory and cognitive deficits in AD mice. These findings provide a novel clinical application for scaffold materials and functional exosomes derived from stem cells. 相似文献
35.
36.
37.
Zhai Wangyi Cao Yuanming Li Yifei Zheng Min Wang Zuoshan 《Journal of Materials Science》2022,57(4):2597-2609
Journal of Materials Science - The exploration of novel and multifunctional coatings through composite nanomaterials design is crucial for developing next-generation polyester fabrics. Herein, we... 相似文献
38.
深部开采煤柱载荷在底板岩层传递影响角的探讨 总被引:3,自引:0,他引:3
在阐明深部巷道围岩变形机理的基础上,对煤柱支承压力在底板传播规律和煤柱载荷在底板岩层传递影响角进行了分析,并结合实测资料,提出了测定煤柱影响的方法,为深部开采底板巷道合理位置选择提供了依据。 相似文献
39.
40.