全文获取类型
收费全文 | 785篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 364篇 |
晶体学 | 4篇 |
力学 | 25篇 |
数学 | 39篇 |
物理学 | 363篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 7篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 42篇 |
2012年 | 22篇 |
2011年 | 40篇 |
2010年 | 19篇 |
2009年 | 24篇 |
2008年 | 47篇 |
2007年 | 43篇 |
2006年 | 36篇 |
2005年 | 26篇 |
2004年 | 12篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 5篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 14篇 |
1972年 | 5篇 |
排序方式: 共有795条查询结果,搜索用时 15 毫秒
141.
Bidyut B. Sarma Jonglack Kim Jonas Amsler Giovanni Agostini Claudia Weidenthaler Norbert Pfnder Raul Arenal Patricia Concepcin Philipp Plessow Felix Studt Gonzalo Prieto 《Angewandte Chemie (International ed. in English)》2020,59(14):5806-5815
Realizing the full potential of oxide‐supported single‐atom metal catalysts (SACs) is key to successfully bridge the gap between the fields of homogeneous and heterogeneous catalysis. Here we show that the one‐pot combination of Ru1/CeO2 and Rh1/CeO2 SACs enables a highly selective olefin isomerization‐hydrosilylation tandem process, hitherto restricted to molecular catalysts in solution. Individually, monoatomic Ru and Rh sites show a remarkable reaction specificity for olefin double‐bond migration and anti‐Markovnikov α‐olefin hydrosilylation, respectively. First‐principles DFT calculations ascribe such selectivity to differences in the binding strength of the olefin substrate to the monoatomic metal centers. The single‐pot cooperation of the two SACs allows the production of terminal organosilane compounds with high regio‐selectivity (>95 %) even from industrially‐relevant complex mixtures of terminal and internal olefins, alongside a straightforward catalyst recycling and reuse. These results demonstrate the significance of oxide‐supported single‐atom metal catalysts in tandem catalytic reactions, which are central for the intensification of chemical processes. 相似文献
142.
U. Pandey S. Banerjee A. Mukherjee H. D. Sarma M. Venkatesh 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):719-723
Several human tumors such as neuroendocrine tumors, medullary thyroid carcinoma, etc., express somatostatin receptors which
specifically bind somatostatin and its analogues such as lanreotide, octreotide, etc. In order to prepare a therapeutic agent
for targeting such tumors, attempts were made to prepare 90Y-DOTA-Lanreotide. Lanreotide could be successfully conjugated with the macrocyclic chelating agent DOTA (1,4,7,10-tetraaza
cyclododecane tetracetic acid) which forms stable complexes with 90Y. 90Y-DOTA-Lanreotide could be prepared in >98% radiochemical purity and remained stable for 72 hours at room temperature. The
tracer showed specific binding to A431 cells. Biodistribution studies in C57BL6 mice bearing melanoma showed ∼1.3% uptake
pergram of tumor at 24-hour p.i. 相似文献
143.
Papu Kalita Biman Medhi Haobam Kisan Singh Himangshu Pratim Bhattacharyya Nikhil Gupt Dr. Manabendra Sarma 《Chemphyschem》2023,24(3):e202200727
The conical intersection (CI) governs the ultra-fast relaxation of excited states in a radiationless manner and are observed mainly in photochemical processes. In the current work, we investigated the effects of substituents on the reaction dynamics for the conversion of gauche-1,3-butadiene to bicyclobutane via photochemical electrocyclization. We incorporated both electron withdrawing (−F) and donating (−CH3) groups in the conjugated system. In our study, we optimized the minimum energy conical intersection (MECI) geometries using the multi-configurational state-averaged CASSCF approach, whereas, to study the ground state reaction pathways for the substituted derivatives, dispersion corrected, B3LYP-D3 functional was used. The non-adiabatic surface hopping molecular dynamics simulations were performed to observe the behaviour of electronic states involved throughout the photoconversion process. The results obtained from the multi-reference second-order perturbation correction of energy at the XMS-CASPT2 level of theory, topography analysis, and non-adiabatic dynamics suggest that the −CH3 substituted derivatives can undergo faster thermal conversion to the product in the ground state with a smaller activation energy barrier compared to −F substituted derivative. Our study also reveals that the GBUT to BIBUT conversion follows both conrotatory and disrotatory pathways, whereas, on substitution with −F or −CH3, the conversion proceeds via the conrotatory pathway. 相似文献
144.
The possibility of excited‐state protomeric shifts in the biologically important molecule, alloxan, is investigated. We have focused on the S1 and T1 excited states of alloxan and its hydroxy tautomers. Modifications brought in by excitation on the relative stabilities, activation barriers, and optimized geometries, computed at the MNDO, AM1, and PM3 levels of approximation, have been discussed for both excited electronic states. The absorption and fluorescence spectra for the three tautomers are also discussed. Results show significant changes in the geometries on excitation, although the changes are similar for the singlet and triplet excited states. Though the relative stability orders do not change, the 2‐hydroxy tautomer is stabilized, while the 4‐hydroxy tautomer gets destabilized on excitation. The excited states are (n,π*) states, involving the promotion of a nonbonding oxygen lone pair from the CO? CO? CO moiety, which explains why the oxygens of this group become less basic and the 4‐hydroxy tautomer gets destabilized on excitation. However, the activation barriers do not reduce significantly on excitation, and this precludes the possibility of ground‐ or excited‐state proton transfer in the gas phase. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 相似文献
145.
Das MR Sarma RK Saikia R Kale VS Shelke MV Sengupta P 《Colloids and surfaces. B, Biointerfaces》2011,83(1):16-22
A solution-based approach to the synthesis of silver (Ag) nanoparticles by chemical reduction of AgNO(3) in a graphene oxide (GrO) suspension is demonstrated. X-ray diffraction and transmission electron microscopy indicate that the Ag nanoparticles, of size range 5-25nm, were decorated on the GrO sheets. The size and shape of the Ag nanoparticles are dependent on the concentration of the AgNO(3) solution. Antimicrobial activity of such hybrids materials is investigated against the Gram negative bacteria Escherichia coli and Pseudomonous aeruginosa. The bacterial growth kinetics was monitored in nutrient broth supplemented with the Ag nanoparticle-GrO suspension at different conditions. It was observed that P. aeruginosa is comparatively more sensitive to the Ag nanoparticle-GrO suspension. 相似文献
146.
The success of organic light emitting diodes (OLED) has been witnessed by the commercialization of this technology for manufacturing the vivid and colorful displays used in our daily life now. The prospective growth of OLED technology on display industry will be optimistic. Over the last three decades, many different approaches on material and device designs have been implemented for improving the efficiency and stability of OLED devices. These efforts install main cornerstones to support the great achievement of OLED technology. However, until now, the performance and stability of blue OLEDs still have some concerns. This troublesome issue should be totally conquered before the large‐scale manufactures dominated over other display technologies, particularly liquid crystal‐based displays, takes place. Though significant progress has already been made to achieve high performance and long lifetime blue OLEDs, this topic still remains as one of the hot researches in OLEDs. We have been working on this area for about two decades and made some notable contributions. Consequently, in this personal account we have outlined our efforts to obtain better performing blue OLEDs by utilizing a range of emitters based on fluorescence, phosphorescence, delayed fluorescence and exciplex systems. We have also developed some novel host materials for blue OLEDs, which are worth mentioning in this account. 相似文献
147.
Chen CH Hwang BJ Wang GR Sarma LS Tang MT Liu DG Lee JF 《The journal of physical chemistry. B》2005,109(46):21566-21575
We report in situ X-ray absorption spectroscopy (XAS) investigations on the formation of palladium-platinum (Pd/Pt) bimetallic clusters at the early stage within the water-in-oil microemulsion system of water/AOT/n-heptane. The reduction of palladium and platinum ions and the formation of corresponding clusters are monitored as a function of dosage of reducing agent, hydrazine (N(2)H(5)OH). Upon successive addition of the reducing agent, hydrazine (N(2)H(5)OH), five distinguishable steps are observed in the formation process of Pd/Pt clusters at the early stage. Both in situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis for both the Pd K-edge and Pt L(III)-edge revealed the formation of Pd/Pt bimetallic clusters. A corresponding structural model is proposed for each step to provide a detailed insight into the nucleation and growth mechanism of Pd/Pt bimetallic clusters. We also discussed the atomic distribution of Pd and Pt atoms in Pd/Pt bimetallic clusters based on the calculated XAS structural parameters. 相似文献
148.
149.
150.