全文获取类型
收费全文 | 588篇 |
免费 | 57篇 |
国内免费 | 54篇 |
专业分类
化学 | 446篇 |
晶体学 | 11篇 |
力学 | 52篇 |
综合类 | 3篇 |
数学 | 36篇 |
物理学 | 151篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 22篇 |
2021年 | 22篇 |
2020年 | 27篇 |
2019年 | 20篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 40篇 |
2015年 | 32篇 |
2014年 | 28篇 |
2013年 | 29篇 |
2012年 | 60篇 |
2011年 | 55篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 39篇 |
2007年 | 49篇 |
2006年 | 33篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有699条查询结果,搜索用时 265 毫秒
81.
82.
Bingbing Shi Zhengtao Li Yuezhou Liu Liqing Shangguan Huangtianzhi Zhu Huaqiang Ju Feihe Huang 《Tetrahedron letters》2018,59(38):3477-3480
Here we report the design and syntheses of two new triptycene-based rigid acyclic C-shaped hosts, clip[5]arenes C[5]OH and C[5]ME, and the strong host–guest complexation between C[5]OH and an electron-poor bipyridinium salt, paraquat G. The Ka value for the host–guest complex C[5]OH???G was calculated to be (1.09?±?0.36)??×??105?M?1 in acetone by using a non-linear curve-fitting method based on the UV–vis absorption titration experiments. Furthermore, based on this new host–guest recognition motif, a novel pseudopolyrotaxane-like supramolecular structure was constructed with C[5]OH threaded on polyviologen polymer VP-10. 相似文献
83.
Jian-Jun Zhong Ningbo Liao Yunfeng Pu Tian Ding Xingqian Ye Donghong Liu 《Chromatographia》2018,81(7):1097-1102
Nowadays, there is a demand for fast liquid chromatography (LC) of biogenic amines in food with the equipment available in the average laboratory. To this end, high-temperature liquid chromatography (HTLC) is presented in this study as a viable option, working on a conventional LC platform at moderately high temperatures up to 80 °C. The LC platform was adapted by including an appropriate length of stainless-steel microbore tubing as a preheater. Biogenic amines as benzoyl derivatives showed good thermostability on a thermally rugged column (150?×?4.6 mm, 5 µm). As a model application the HTLC conditions were developed for wine separation. The separation selectivity changed considerably with temperature in the range 36–84 °C, and baseline resolution was obtained only at temperatures well above ambient. At 73 °C oven temperature, the system allowed a flow rate as high as 3 mL min?1 with the backpressure not exceeding 195 bar (2800 psi). The separation took less than 5 min, comparably fast to documented fast LC separations, and typically at least three to five times faster than a conventional separation. 相似文献
84.
The aggregation and assembly of crescent oligoamides with two to six benzene residues are investigated. In chloroform, the pentamer and hexamer are found to associate into large aggregates. In the solid state, all oligomers examined associate into columnar assemblies via stacking interactions, as shown by X-ray diffraction data from single crystals and powder samples. The columnar assemblies of the pentamer and hexamer should contain hydrophilic channels defined by the constituent oligomers. 相似文献
85.
An effective strategy for the synthesis of N-2-substituted-1,2,3-triazoles with excellent yields and regioselectivity has been developed. 相似文献
86.
A biocomposite material of hyaluronic acid (HA) and room temperature ionic liquid, 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate (BMIMBF4) was fabricated and characterized by voltammetry and electrochemical impedance spectroscopy. Hemoglobin (Hb), as a model protein, was immobilized in this biocomposite on glassy carbon electrode to investigate its direct electrochemistry. A pair of well‐defined, quasireversible cyclic voltammetric peaks appeared with the formal potentials (E°′) at ?0.360 V (vs. SCE). The Hb modified electrode exhibited an excellent electrocatalytic activity to the reduction of H2O2 with a wide linear range, good selectivity, sensitivity and reproducibility, which had potential application to fabrication the third‐generation biosensor. 相似文献
87.
Hai Hu Wenjun Xiao Jian Yuan Jianwei Shi Dannong He Wenfeng Shangguan 《Journal of Sol-Gel Science and Technology》2008,45(1):1-8
A set of anatase titanium dioxide (TiO2) films coated on foam nickel that modified by Al2O3 films as transition layer (indicated as TiO2/Al2O3 films) were synthesized via sol-gel route. The bulk and surface properties of the TiO2/Al2O3 films were characterized by thermal gravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD),
field-emission scanning electron microscope (FE-SEM), and BET. The photocatalytic activities of TiO2/Al2O3 films were investigated based on the degradation of gaseous acetaldehyde under ultraviolet (UV) irradiation. The foam nickel
is a promising substrate material in practical applications because of its excellent hydrodynamic properties for gas passing.
The TiO2/Al2O3 composite films showed much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than the
onefold TiO2 films. The significant enhancement in photocatalytic activity and stability can be ascribed to the coating of Al2O3 transition layer, which concentrates the target substances around TiO2 particles and increases the specific surface area (SSA) of the substrate (the SSAs of bare foam nickel and Al2O3 modified foam nickel are 0.12 and 113.7 m2/g, respectively) to provide more sites for TiO2 loading. 相似文献
88.
Qidi Ren Lu Wang Wenfei Qian Baiqiu Chen Qi Shuai Yunfeng Yan 《Macromolecular bioscience》2023,23(7):2300085
RNA interference (RNAi) is a promising approach for disease treatments. But the development of safe and effective delivery carriers remains a major challenge. Organic–inorganic hybrid nanoparticles (NPs), with the integration of functions from distinct materials, show great potential in small interfering RNA (siRNA) delivery. Herein, pH responsive amorphous calcium carbonate NPs (ACC NPs) are prepared using flash nanoprecipitation and hybrid NPs are constructed by coating ACC NPs with polyethyleneimine (PEI) for efficient siRNA delivery. PEI/ACC NPs show robust pH responsiveness and stability as well as effective siRNA loading and protection. Furthermore, siRNA-loaded PEI/ACC NPs demonstrate enhanced cellular uptake and efficient endosomal escape, mediating improved siRNA delivery compared to pure PEI. These findings suggest that PEI/ACC NPs may have great potential in siRNA delivery for RNAi-based therapy. 相似文献
89.
Chiral lactic acid and its ester derivatives are crucial building blocks and platforms in the generation of high value-added drugs, fine chemicals and functional materials. Optically pure D-lactic acid and its ester derivatives cannot be directly generated from fermentation and are quite expensive. Herein, we identified, heterologously expressed and functionally characterized one Bacillus esterase BSE01701 from the deep sea of the Indian Ocean. Esterase BSE01701 could enzymatically resolve inexpensive racemic methyl lactate and generate chiral D-methyl lactate. The enantiomeric excess of desired chiral D-methyl lactate and the substrate conversion could reach over 99 % and 60 %, respectively, after process optimization. Notably, the addition of 60 % (v/v) organic co-solvent heptane could greatly improve both the enantiomeric excess of D-methyl lactate and the conversion. BSE01701 was a very promising marine microbial esterase in the generation of chiral chemicals in industry. 相似文献
90.