全文获取类型
收费全文 | 158篇 |
免费 | 22篇 |
国内免费 | 30篇 |
专业分类
化学 | 113篇 |
力学 | 10篇 |
综合类 | 7篇 |
数学 | 34篇 |
物理学 | 46篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 22篇 |
2011年 | 17篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
排序方式: 共有210条查询结果,搜索用时 343 毫秒
31.
(Ca,Mg)—Sialon陶瓷在空气及水润滑条件下的磨损机理研究 总被引:7,自引:7,他引:7
利用SRV球-盘磨损试验机考察了一种(Ca,Mg)-Sialon陶瓷在空气及水中的摩擦学性能,并采用EPMA,SEM,EDAX以及XPS等分析手段对其磨损机理做了进一步研究。结果表明:(Ca,Mg)-Sialon陶瓷在水中比在空气中具有更低的摩擦因数,但具有较高的磨损体积损失。 相似文献
32.
自下而上法制备金-介孔二氧化硅复合纳米管用作还原4-硝基苯酚的催化剂 总被引:1,自引:0,他引:1
采用自下而上方法制备了金-介孔二氧化硅复合纳米管,其中金纳米粒子作为催化剂嵌在介孔二氧化硅纳米管管壁内侧。金纳米颗粒的团聚、脱落和晶粒尺寸生长都可以被有效限制,而且催化剂负载量和尺寸大小均可实现简单控制。管壁中的介孔孔道、纳米管末端开口以及一维中空管道可以协同促进反应物扩散,从而提高4-硝基苯酚还原反应活性。循环实验证明这种复合纳米管催化剂具有良好的可重复使用性,而且在反应过程中未出现金纳米粒子脱落或团聚现象。 相似文献
33.
本文研究了和素数有关的方程组和不等式组,通过更细致的指数和估计,我们改进了以前的结果。 相似文献
34.
电场驱动的高分子凝胶 总被引:1,自引:0,他引:1
本文较系统地阐述了电场驱动的高分子水凝胶、有机凝胶的响应机理,并扼要介绍了此类凝胶应用的最新进展。 相似文献
35.
Suppose a and b are two fixed positive integers such that (a, b) = 1. In this paper we shall establish an asymptotic formula for the mean square of the error term Δ a,b (x) of the general two-dimensional divisor problem. 相似文献
36.
Suppose a and b are two fixed positive integers such that (a, b) = 1. In this paper we shall establish an asymptotic formula for the mean square of the error term Δ
a,b
(x) of the general two-dimensional divisor problem. 相似文献
37.
We study the mean square of the error term of the mean value for binary Egyptian fractions.We get an asymptotic formula under the Riemann Hypothesis. 相似文献
38.
钢渣和污泥作为传统大宗固体废弃物,始终面临处理成本高、回收利用率低等问题,但其内部含有大量可利用物质,具有较高的资源化利用价值,现已成为国内外的研究热点。为了提高钢渣与污泥绿色、高效、协同资源化利用,综述了近年来国内外钢渣在建筑、道路、水处理、农业等领域资源化利用的研究进展,立足固废无害化、减量化,从钢渣和污泥的资源化进行分析与总结,指出不同研究方法的特点和优劣,为固废资源化利用提供参考。并基于我国发展现状对钢渣与污泥资源化利用的未来发展方向进行了展望,以期为固废处理行业的良性发展提供一定的理论支撑。 相似文献
39.
Superior Electrical Conductivity in Hydrogenated Layered Ternary Chalcogenide Nanosheets for Flexible All‐Solid‐State Supercapacitors
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Xin Hu Wei Shao Xudong Hang Dr. Xiaodong Zhang Prof. Wenguang Zhu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(19):5733-5738
As the properties of ultrathin two‐dimensional (2D) crystals are strongly related to their electronic structures, more and more attempts were carried out to tune their electronic structures to meet the high standards for the construction of next‐generation smart electronics. Herein, for the first time, we show that the conductive nature of layered ternary chalcogenide with formula of Cu2WS4 can be switched from semiconducting to metallic by hydrogen incorporation, accompanied by a high increase in electrical conductivity. In detail, the room‐temperature electrical conductivity of hydrogenated‐Cu2WS4 nanosheet film was almost 1010 times higher than that of pristine bulk sample with a value of about 2.9×104 S m?1, which is among the best values for conductive 2D nanosheets. In addition, the metallicity in the hydrogenated‐Cu2WS4 is robust and can be retained under high‐temperature treatment. The fabricated all‐solid‐state flexible supercapacitor based on the hydrogenated‐Cu2WS4 nanosheet film shows promising electrochemical performances with capacitance of 583.3 F cm?3 at a current density of 0.31 A cm?3. This work not only offers a prototype material for the study of electronic structure regulation in 2D crystals, but also paves the way in searching for highly conductive electrodes. 相似文献
40.
Bing Xu Tao Bai Andrew Sinclair Wei Wang Qian Wu Fei Gao Huizhen Jia Shaoyi Jiang Wenguang Liu 《Materials Today Chemistry》2016
Stem-cell-based neural regeneration has received significant attention, as it has potential to restore functionality to diseased or damaged neural tissues that have a limited ability to self-repair or regenerate. Culturing neural stem cells (NSCs) on hydrogel substrates has been shown to facilitate differentiation to neural progenitors, but this has only been achieved on very soft hydrogels, greatly increasing the difficulty of manufacture and limiting their wide applications. Here, we realized the differentiation of NSCs to neural and glial progenitors on high-strength hydrogels. Hydrogen-bonding-strengthened conductive hydrogels (PVV-PANI) were synthesized through one-pot copolymerization of 2-vinyl-4,6-diamino-1,3,5-triazine, 1-vinylimidazole and polyethylene glycol diacrylate, followed by post-coating with polyaniline (PANI). Diaminotriazine-diaminotriazine hydrogen bonding dramatically increases their mechanical strength, while copolymerization with VI pronouncedly promotes the adsorption of PANI particles, endowing the hydrogels with electrical conductivity. These hydrogels exhibit tensile strengths up to 1.16 MPa, a 559% breaking strain, a 9.9 MPa compressive strength and up to 16.7 mS/cm conductivity. Importantly, PVV-PANI hydrogels support the attachment, proliferation, and differentiation of NSCs, and allow the efficient induction of neural and glial differentiation via electrical stimulation. This work demonstrates high-strength conductive hydrogels can serve as an electroactive soft-wet platform for modulating the specific differentiation of NSCs, a significant step towards cell-based therapies for neurological diseases. 相似文献