全文获取类型
收费全文 | 312篇 |
免费 | 27篇 |
国内免费 | 52篇 |
专业分类
化学 | 260篇 |
晶体学 | 2篇 |
力学 | 28篇 |
综合类 | 5篇 |
数学 | 46篇 |
物理学 | 50篇 |
出版年
2024年 | 3篇 |
2023年 | 23篇 |
2022年 | 31篇 |
2021年 | 22篇 |
2020年 | 36篇 |
2019年 | 25篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 24篇 |
2013年 | 19篇 |
2012年 | 19篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 13篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有391条查询结果,搜索用时 31 毫秒
81.
将典型的光热等离激元石墨烯和纳米金简便地负载在钛酸钠(Na2Ti3O7)载体上, 构建出具有较窄禁带宽度和较高光催化活性的Au/RGO/Na2Ti3O7光热辅助光催化体系. 研究发现, 石墨烯片层与金纳米颗粒在光照下, 通过局域表面等离激元共振效应诱导产生大量的热电子, 以活化反应物并降低反应活化能, 其引发的光热效应还可精准提升光催化体系中反应位点附近的温度, 从而大幅提升光催化反应速率. 通过构建特殊微支结构, 进一步增强了Au/RGO/Na2Ti3O7催化剂对光的捕获, 并限域锚定高表面能催化剂以增强体系的稳定性. 在光热、 光催化的高效协同增强下, Au/RGO/Na2Ti3O7催化剂体系对对硝基苯酚和肉桂醛的加氢反应均表现出增强的光催化活性. 光热辅助下的Au/RGO/Na2Ti3O7光催化剂在对硝基苯酚反应中的转换频率(TOF)值高达54.4 min-1, 反应活化能显著降低至15.78 kJ/mol, 且其在长效测试中表现出良好的稳定性(4次循环催化后, 转化率的保持率近90%). 相似文献
82.
CO2驱是一种具有广阔前景的提高油藏采收率的方法。其中,降低CO2与原油的最低混相压力以实现混相驱是增强CO2驱效果的重要手段。由此我们设计了由亲油基团十六烷基和亲CO2基团全乙酰蔗糖酯基结合的新型“亲油-亲CO2助混分子”十六酸全乙酰基蔗糖酯CAA8-X,研究发现,CAA8-X对超临界CO2流体和不同油相的煤油、白油以及长庆原油有优异的助混效果,界面张力消失法和细管实验法测定结果表明,CAA8-X可以将超临界CO2/长庆原油的最低混相压力降低20.5%。用分子动力学模拟计算了CO2分子与全乙酰蔗糖酯基的亲和能力,研究了这类新型“亲油-亲CO2助混分子”通过多酯头基降低与CO2亲和势能而降低油/CO2界面能的助混机理。 相似文献
83.
84.
Thermo‐Driven Controllable Emulsion Separation by a Polymer‐Decorated Membrane with Switchable Wettability 下载免费PDF全文
Dr. Weifeng Zhang Dr. Na Liu Dr. Qingdong Zhang Dr. Ruixiang Qu Dr. Yanan Liu Dr. Xiangyu Li Prof. Yen Wei Prof. Lin Feng Prof. Lei Jiang 《Angewandte Chemie (International ed. in English)》2018,57(20):5740-5745
A thermoresponsive Poly(N‐isopropylacrylamide) (PNIPAAm)‐modified nylon membrane was fabricated via hydrothermal route. Combining rough structure, proper pore size, and thermoresponsive wettability, the membrane can separate at least 16 types of stabilized oil‐in‐water and water‐in‐oil emulsions at different temperatures. Below the LCST (ca. 25 °C), the material exhibits hydrophilicity and underwater superoleophobicity, which can be used for the separation of various kinds of oil‐in‐water emulsions. Above the LCST (ca. 45 °C), the membrane shows the opposite property with high hydrophobicity and superoleophilicity, and it can then separate stabilized water‐in‐oil emulsions. The material exhibits excellent recyclability and high separation efficiency for various kinds of emulsions and the hydrothermal method is facile and low‐cost. The membrane shows good potential in real situations such as on‐demand oil‐spill cleanup, industrial wastewater treatment, remote operation of oil/water emulsion separation units, and fuel purification. 相似文献
85.
建立了一种基于离子液体分散液液微萃取前处理技术的食品接触材料中全氟辛酸和全氟辛烷磺酸迁移量的超高效液相色谱-串联质谱测定方法。水、10%(体积分数)乙醇溶液和4%(体积分数)乙酸溶液作为3种水性食品模拟物与食品接触材料充分接触,进行迁移试验,对迁移液采用离子液体分散液液微萃取技术进行目标物的萃取富集,考察了萃取剂种类和用量、涡旋时间、盐浓度、离心速率及时间等关键因素对食品模拟物中全氟辛酸和全氟辛烷磺酸萃取效率的影响。使用Waters ACQUITY UPLC BEH Shield RP18色谱柱(50 mm×2.1 mm,1.7 μm),以乙腈和水为流动相,梯度洗脱分离,在电喷雾负离子模式下,采用多反应监测模式进行定性及定量分析。结果表明,全氟辛酸和全氟辛烷磺酸在各自范围内线性关系良好(r2>0.99),检出限分别为0.5和1 μg/L,定量限分别为2和5 μg/L;在低、中、高3个添加水平下全氟辛酸和全氟辛烷磺酸的平均回收率为86.4%~116.9%,相对标准偏差为4.3%~14.4%(n=6)。该方法准确高效、环境友好,适用于食品接触材料中全氟辛酸和全氟辛烷磺酸迁移量的检测。 相似文献
86.
Ying Lv Xiangyu Ma Jinsong Chai Dr. Haizhu Yu Prof. Dr. Manzhou Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(61):13977-13986
Face-centered-cubic (FCC) silver nanoclusters (NCs) adopting either cubic or half-cubic growth modes have been recently reported, but the origin of these atomic assembly patterns and how they are achieved, which would inform our understanding of larger FCC silver nanomaterials, are both unknown. In this study, the cubic and half-cubic growth modes have been unified based on common structural characteristics, and differentiated depending on the starting blocks (cubic vs. half cubic). In both categories, the silver atoms adopt octahedral Ag6, linear AgS2 (in projection drawing), or tetrahedral AgS3P binding modes, and the sulfur atoms adopt T-shaped SAg3 and orthogonal SAg4 modes. An additional T-shaped AgS3 mode is oriented on the surface edge in cubic NCs to complete the cubic framework. Density functional theory calculations indicated that the high structural regularity originates from the strong diffusing capacity of the Ag(5d) and S(3p) orbitals, and the angular momentum distribution of the formed superatomic orbitals. The equatorial orientation of μ4-S or μ4-Ag determines whether growth stops or continues. In particular, a density-of-states analysis indicated that the octahedral silver atoms are chemically more reactive than the silver atoms in the AgS3P motif, regardless of whether the parent NC functions as an electron donor or acceptor. 相似文献
87.
Zeolite imidazolate frameworks (ZIFs) have recently emerged as an ideal type of carbon precursors with abundant tailorability. In this work, a series of ZIF‐derived porous carbon catalysts have been prepared with encapsulation of bimetallic oxide nanoparticles via simple thermal treatment. The composition and structure of these catalysts were confirmed in detail by different characterization methods. The bimetallic oxide (Mn/Co, Fe/Co, and Cu/Co) nanoparticles were encapsulated in the nitrogen‐doped graphitized carbon matrix. Moreover, the hierarchically porous structure and carbon defects were successfully constructed in the carbon catalysts. Additionally, in the selective oxidation of saturated C–H bonds in alkyl arenes, the carbon catalysts demonstrate outstanding performance for the oxidation of C–H bonds to corresponding carboxyl groups. This was due to their unique structure can greatly promote mass transfer and molecular oxygen activation, resulting in high conversion and high selectivity. Remarkably, this work here could also provide a novel strategy to the controllable synthesis of metal–organic frameworks (MOFs)‐derived carbon catalysts for enhanced performance in heterogeneous catalysis. 相似文献
88.
89.
Alenka Vesel Rok Zaplotnik Gregor Primc Xiangyu Liu Kaitian Xu Kevin C. Chen Chiju Wei Miran Mozetic 《Plasma Chemistry and Plasma Processing》2016,36(3):835-848
Samples of porous foam from polyurethane/urea copolymers based on polyethylene glycol (PURPEG) were prepared in the form of 1-mm-thick discs of diameter 10 cm and exposed to ammonia plasma created by inductively coupled radiofrequency discharge in either low density (E mode) or high density (H mode). The evolution of surface composition and structure upon plasma treatment was characterized by X-ray photoelectron spectroscopy. Treatment in the H mode caused depletion of oxygen even after 2 s of treatment, whereas treatment in the E mode caused gentle functionalization with amide groups. The concentration of functional groups depended on the discharge power, and the best results were obtained at moderately high power just before the transition from E to H modes. 相似文献
90.
电子雷管的技术潜力目前仍未在隧道工程中得以充分发挥,一个重要原因是没有严密理论支撑的爆破参数计算方法,药量、孔间延时等核心参数多沿用普通矿山法设计;其次是不能解决第二自由面形成后爆破参数计算准确性问题。以重庆观音桥隧道为研究背景,基于Anderson理论和电子雷管延时特性,提出隧道爆破在单自由面形成双自由面过程中,不同自由面条件下电子雷管爆破参数设计的新方法。现场获取不同药量单自由面单孔爆破振动曲线,逐一计算各孔间延时下的多孔合成振动,对比不同药量、不同延时合成振动曲线后确定单自由面爆破参数;根据电子雷管特点设计短延时掏槽爆破现场试验,获得起爆48 ms后已形成第二自由面;据此设计第二自由面形成后单孔爆破试验并计算双自由面下的合成振速、爆破参数,最终形成爆破全过程爆破参数计算方法。对计算结果进行综合分析后,现场设计主掏槽单孔药量1.2 kg,辅助掏槽单孔药量1.4 kg,孔间延时为5 ms;主掏槽与辅助掏槽间最小时差为35 ms;采用上述优化参数进行现场试验,在低振速控制的同时实现高效进尺。 相似文献