全文获取类型
收费全文 | 302篇 |
免费 | 18篇 |
专业分类
化学 | 183篇 |
数学 | 27篇 |
物理学 | 110篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 11篇 |
2013年 | 29篇 |
2012年 | 32篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 11篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有320条查询结果,搜索用时 15 毫秒
251.
Samim Sultana Shreemoyee Bordoloi Surajit Konwer Geetika Borah Pradip K. Gogoi 《应用有机金属化学》2020,34(5):e5582
Reduced graphene oxide was synthesized and functionalized with FeSO4⋅7H2O to form a reduced graphene oxide/iron oxide hybrid composite. The hybrid composite was extensively characterized using various techniques. Its application for transfer hydrogenation of various ketones was studied. The investigation showed that it serves as a good catalyst for transfer hydrogenation of aromatic and some aliphatic ketones resulting in excellent isolated yields (97–99%) of products. It is magnetically separable showing good reusability. The products were characterized and compared with authentic ones. 相似文献
252.
Shakya Anshul Chaudhary Sushil Kumar Bhat Hans Raj Gogoi Neelutpal Ghosh Surajit Kumar 《平面色谱法杂志一现代薄层色谱法》2019,32(6):467-474
JPC – Journal of Planar Chromatography – Modern TLC - Ayurvedic medicines show great promise due to their holistic approach in the treatment of diseases. However, proper standardization... 相似文献
253.
Nayana Adhikari Ankita Kashyap Anshul Shakya Surajit Kumar Ghosh Dibya Ranjan Bhattacharyya Hans Raj Bhat Udaya Pratap Singh 《Journal of heterocyclic chemistry》2020,57(6):2389-2399
A series of novel PABA-substituted 1,3,5-triazine derivatives were developed via microwave assisted synthesis and subsequently tested for antimalarial activity against chloroquine sensitive 3D7 strain of Plasmodium falciparum using chloroquine as standard. Antimalarial screening result showed that synthesized compounds exhibited IC50 in the range of 4.46 to 79.72 μg mL−1. Among the tested compounds, 4c and 4f showed significant antimalarial activity with low binding energies (BE) -172.32 and 160.41 kcal mol−1 via interacting with Arg122 through the involvement of COOH of the phenyl linked to 1,3,5-triazine. In conclusion, these core scaffolds can be used for future antimalarial drug development. 相似文献
254.
255.
D.K. Rai Debjit Datta Sanjay K. Ram Surajit Sarkar Rajeev Gupta Satyendra Kumar 《Solid State Sciences》2010,12(8):1449-1454
Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp3 content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H2 content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient (γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications. 相似文献
256.
257.
Vidhika Punjani Dr. Golam Mohiuddin Supreet Kaur Dr. Angshuman Roy Choudhury Dr. Sathyanarayana Paladugu Dr. Surajit Dhara Dr. Sharmistha Ghosh Dr. Santanu Kumar Pal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5859-5871
Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent-shaped systems with a −CH3 moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even-numbered carbon chains from n=4 to 18 were synthesized, in which −Cl was substituted for −CH3 at the kink position and a drastic modification in the phase structure of the bent-shaped molecule was observed. An unusual stabilization of the cubic blue phase (BP) over a wide range of 16.4 °C has been witnessed. Two homologues in this series ( 1 -12 and 1 -14) exhibit an interesting phase sequence consisting of BPI/II, chiral nematic, twist grain boundary, smectic A, and smectic X (SmX) phases. The higher homologues ( 1 -16 and 1 -18) stabilize the SmX phase enantiotropically over the entire temperature range. Crystal structure analysis confirmed the bent molecular architecture, with a bent angle of 148°, and revealed the presence of two different molecular conformations in an asymmetric unit of compound 1 -4. A DFT study corroborated that the −Cl moiety at the central core of the molecule led to an increase in the dipole moment along the transverse direction, which, in turn, facilitated the unusual stabilization of frustrated structures. Crystal polymorphism has been evidenced in three homologues ( 1 -10, 1 -12, and 1 -14) of the series. On the application of mechanical pressure through grinding, compound 1 -10 transformed from a bright yellow crystalline solid to a dark orange–green amorphous solid, which reversed upon dropwise addition of dichloromethane, indicating reversible mechanochromism in this class of compounds. In addition, excellent thermochromic behavior has been observed for compound 1 -10 with a controlled temperature–color combination. 相似文献
258.
259.
Radhakrishnan Mahesh Arghya Kusum Dhar Tara Sasank T.V.N.V. Sappanimuthu Thirunavukkarasu Thangaraj Devadoss 《中国化学快报》2011,22(4):389-392
The condensation of o-phenylenediamines with 1,2-dicarbonyl compounds in the presence of citric acid afforded the corresponding quinoxaline derivatives in higher yields at room temperature in ethanol,and most of the reactions were completed in less than 1 min. 相似文献
260.
Sandip Dhara Chuan‐Pu Liu Shu‐Fang Chen Andrei A. Eliseev Dmitry I. Petukhov 《Journal of Raman spectroscopy : JRS》2015,46(1):1-3
We report an observation of shape‐induced phase transition from wurtzite to zinc blende phase of encapsulated CdSe nanoclusters in mesoporous silica. Presence of both the phases is also observed in the as‐grown sample before encapsulation. Role of interfacial energy in the energetic mesopores, as the possible origin of phase transition, is thus ruled out, as the samples are encapsulated subsequent to their synthesis in the soft chemistry route. Electron–phonon coupling in the resonant Raman spectroscopic studies, using different energies for clusters of different phase and shape, thereby confirms the presence of both the wurtzite and the zinc blende phases. Transmission electron microscopic studies are used for the direct evidence of the shape‐induced solid–solid phase transition between two crystalline phases, for the first time. Small fluctuation of energies, in the form of shape, during its growth may be the driving force for the observed phenomenon, as the surface energy of both the phases stabilizes to the same value. Thus, finally, specific shapes can be used as one of the ways to differentiate the resulting phases. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献