全文获取类型
收费全文 | 111145篇 |
免费 | 19036篇 |
国内免费 | 11430篇 |
专业分类
化学 | 75740篇 |
晶体学 | 1343篇 |
力学 | 7354篇 |
综合类 | 679篇 |
数学 | 13245篇 |
物理学 | 43250篇 |
出版年
2024年 | 237篇 |
2023年 | 2203篇 |
2022年 | 2409篇 |
2021年 | 3735篇 |
2020年 | 4524篇 |
2019年 | 4360篇 |
2018年 | 3734篇 |
2017年 | 3464篇 |
2016年 | 5400篇 |
2015年 | 5188篇 |
2014年 | 6285篇 |
2013年 | 8264篇 |
2012年 | 10060篇 |
2011年 | 10626篇 |
2010年 | 7153篇 |
2009年 | 6825篇 |
2008年 | 7288篇 |
2007年 | 6649篇 |
2006年 | 6040篇 |
2005年 | 5102篇 |
2004年 | 3742篇 |
2003年 | 2949篇 |
2002年 | 2697篇 |
2001年 | 2177篇 |
2000年 | 1965篇 |
1999年 | 2215篇 |
1998年 | 1925篇 |
1997年 | 1798篇 |
1996年 | 1868篇 |
1995年 | 1557篇 |
1994年 | 1490篇 |
1993年 | 1208篇 |
1992年 | 1090篇 |
1991年 | 1013篇 |
1990年 | 816篇 |
1989年 | 587篇 |
1988年 | 499篇 |
1987年 | 389篇 |
1986年 | 391篇 |
1985年 | 331篇 |
1984年 | 251篇 |
1983年 | 167篇 |
1982年 | 153篇 |
1981年 | 114篇 |
1980年 | 91篇 |
1979年 | 59篇 |
1978年 | 54篇 |
1976年 | 43篇 |
1974年 | 52篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of... 相似文献
52.
53.
通常采用以氢氧化物作为造孔剂,过渡金属硝酸盐或氯化物作为石墨化催化剂的传统两步法策略制备多孔石墨化碳材料。然而制备过程中多涉及有毒和腐蚀性试剂,且多步骤的过程耗时较长。本文以双氰胺为原料通过热缩聚反应得到g-C3N4,采用高铁酸钾为催化剂一步法实现g-C3N4的同步碳化-石墨化,并研究其光催化性能。与传统的两步法相比,该方法耗时少、效率高、无污染。与初始的g-C3N4材料相比,石墨化g-C3N4衍生碳质材料不仅显著改善了可见光的吸收,而且大大增强了光催化活性。研究了不同石墨化温度对g-C3N4衍生碳质材料在可见光下降解甲基橙溶液的影响。700 ℃下制备的衍生碳质材料的降解率为12.4 mg/g。光电化学测试结果表明,多孔g-C3N4衍生碳质材料的光生载流子密度、电荷分离和光电流(提高了5.4倍)均得到显著提高。因此,该简便、灵活方法为提高g-C3N4衍生碳质材料的吸附和光催化性能提供了一种有前景的、高效的途径。 相似文献
54.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research. 相似文献
55.
Natural products with a variety of pharmacological effects are important sources for commercial drugs, and it is very crucial to develop effective techniques to selectively extract and isolate bioactive natural components from the plants against the background of sustainable development. Ionic liquids (ILs) are a kind of designable material with unique physicochemical properties, including good thermal stability, negligible vapor pressure, good solvation ability, etc. ILs have already been used in pharmaceuticals for extraction, purification, drug delivery, etc. It has been reported that multi-interactions, like hydrogen bonding, hydrophobic interactions, play important roles in the extraction of bioactive components from the plants. In this review, recent progress in the understanding of scientific essence of hydrogen bonding, the special interaction, in ILs was summarized. The extraction of various natural products, one important area in pharmaceutical, by conventional and functional ILs as well as the specific roles of multi-interactions in this process were also reviewed. Moreover, problems existing in bioactive compound extraction by ILs and the future developing trends of this area are given, which might be helpful for scientists, especially beginners, in this field. 相似文献
56.
Yuwei Wang Jia-Jun Yan Shengnan Hu Prof. David James Young Prof. Hong-Xi Li Prof. Zhi-Gang Ren 《化学:亚洲杂志》2021,16(18):2681-2686
A photoluminescent bimetallic cluster [Ag10Cu6(bdppthi)2(C≡CPh)12(MeOH)2(H2O)](ClO4)4 ( 1 , bdppthi=N,N’-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH3 in air or water. The sensing of NH3 was rapid and recoverable, with detection limits of 53 ppm (v/v) in N2 and 21 μmol/L (0.36 ppm, w/w) for NH3 ⋅ H2O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water. 相似文献
57.
Du Yongbo Yu Pengfei Wang Junxiong Zhang Jinping Wang Chang’an Che Defu 《Journal of Thermal Analysis and Calorimetry》2021,143(1):327-334
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential... 相似文献
58.
Wang Dong Ming Fei Song Xue-Ke Ye Liu Chen Jing-Ling 《The European Physical Journal C - Particles and Fields》2020,80(8):1-16
The European Physical Journal C - We study the isentropic evolution of the matter produced in relativistic heavy-ion collisions for various values of the entropy-per-baryon ratio of interest for... 相似文献
59.
60.
Rajkumar P. Diwakar K. Subadevi R. Gnanamuthu R. M. Wang Fu-Ming Liu Wei-Ren Sivakumar M. 《Journal of Solid State Electrochemistry》2021,25(3):939-948
Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To... 相似文献