全文获取类型
收费全文 | 861篇 |
免费 | 16篇 |
国内免费 | 4篇 |
专业分类
化学 | 483篇 |
晶体学 | 9篇 |
力学 | 26篇 |
数学 | 88篇 |
物理学 | 275篇 |
出版年
2022年 | 6篇 |
2021年 | 20篇 |
2020年 | 16篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 33篇 |
2015年 | 7篇 |
2014年 | 25篇 |
2013年 | 60篇 |
2012年 | 40篇 |
2011年 | 40篇 |
2010年 | 32篇 |
2009年 | 26篇 |
2008年 | 43篇 |
2007年 | 33篇 |
2006年 | 38篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 28篇 |
2002年 | 14篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1993年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1987年 | 7篇 |
1985年 | 9篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 15篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1970年 | 7篇 |
1969年 | 10篇 |
1968年 | 14篇 |
1967年 | 8篇 |
1966年 | 6篇 |
1964年 | 7篇 |
1962年 | 5篇 |
排序方式: 共有881条查询结果,搜索用时 0 毫秒
861.
V. K. Afonichkin L. G. Khrustova V. E. Komarov 《Russian Journal of Inorganic Chemistry》2013,58(4):456-462
The oxygen coefficient (atomic ratio O/U) of a cathode product and the cathode current yield in consecutive recovery of uranium oxides from molten salt mixtures (nLi2SO4 + (1 ? n)Cs2SO4) + UO2SO4 and (Li,Na,K)2SO4 + UO2SO4 in air were analyzed as dependent on the electrolyte and the mean solvent-salt cation radius. The increasing mean solvent-salt cation radius and decreasing UO2SO4 concentration in the electrolyte during long-term electrolysis suppress the solvolysis of uranyl ions and decrease the oxygen coefficient in the cathode product. The cathode current yield decreases systematically during electrolysis and drops to zero long before the uranium is completely recovered from the melt. The ultimate uranium recovery increases as the mean solvent-salt cation radius increases. 相似文献
862.
Igor V. Komarov Aleksandr V. Strizhak Mikhail Yu.Kornilov Aleksandr N. Kostyuk Andrey A. Tolmachev 《合成通讯》2013,43(13):2355-2370
Synthetic approaches to 1H-imidazol-2-yl and 1H-benzoimidazol-2-yl phosphinic and phosphonic acids and their derivatives are reported, based on phosphorylation of N-protected heterocylcles by PhPOCl2 or MePOCl2. Reaction of N-alkylbenzoimidazoles with POCl3 did not lead to C-phosphorylated products in a reasonable yield, [2,2′]-bis-benzoimidazolyles being formed instead. 相似文献
863.
Natasha Irrera Alessandra Bitto Emanuela SantAntonio Rita Lauro Caterina Musolino Alessandro Allegra 《Molecules (Basel, Switzerland)》2021,26(13)
The endocannabinoid system (ECS) is a composite cell-signaling system that allows endogenous cannabinoid ligands to control cell functions through the interaction with cannabinoid receptors. Modifications of the ECS might contribute to the pathogenesis of different diseases, including cancers. However, the use of these compounds as antitumor agents remains debatable. Pre-clinical experimental studies have shown that cannabinoids (CBs) might be effective for the treatment of hematological malignancies, such as leukemia and lymphoma. Specifically, CBs may activate programmed cell death mechanisms, thus blocking cancer cell growth, and may modulate both autophagy and angiogenesis. Therefore, CBs may have significant anti-tumor effects in hematologic diseases and may synergistically act with chemotherapeutic agents, possibly also reducing chemoresistance. Moreover, targeting ECS might be considered as a novel approach for the management of graft versus host disease, thus reducing some symptoms such as anorexia, cachexia, fatigue, anxiety, depression, and neuropathic pain. The aim of the present review is to collect the state of the art of CBs effects on hematological tumors, thus focusing on the essential topics that might be useful before moving into the clinical practice. 相似文献
864.
B. A. Komarov E. A. Dzhavadyan V. I. Irzhak A. G. Ryabenko V. A. Lesnichaya G. I. Zvereva A. V. Krestinin 《Polymer Science Series A》2011,53(6):502-509
The physical and mechanical properties of composite materials based on epoxy-amine systems—diglycidyl ether of diphenylolpropane-eutectic
mixture of aromatic amines (40 wt % m-phenylenediamine-60 wt % 4,4′-diaminodiphenylmethane) and epoxy-diane resin ED-20-eutectic mixture of aromatic diamines with
ultralow contents (≤0.1 wt %) of single-layer carbon nanotubes—are studied. It is shown that, for the concentration dependence
of the modulus of elasticity during tension, the additivity rule is obeyed only at the lowest concentrations of carbon nanotubes.
In this case, the presence of near-surface layers of a matrix with an increased elastic modulus should be considered. 相似文献
865.
Wang F Robert R Chernova NA Pereira N Omenya F Badway F Hua X Ruotolo M Zhang R Wu L Volkov V Su D Key B Whittingham MS Grey CP Amatucci GG Zhu Y Graetz J 《Journal of the American Chemical Society》2011,133(46):18828-18836
Materials that undergo a conversion reaction with lithium (e.g., metal fluorides MF(2): M = Fe, Cu, ...) often accommodate more than one Li atom per transition-metal cation, and are promising candidates for high-capacity cathodes for lithium ion batteries. However, little is known about the mechanisms involved in the conversion process, the origins of the large polarization during electrochemical cycling, and why some materials are reversible (e.g., FeF(2)) while others are not (e.g., CuF(2)). In this study, we investigated the conversion reaction of binary metal fluorides, FeF(2) and CuF(2), using a series of local and bulk probes to better understand the mechanisms underlying their contrasting electrochemical behavior. X-ray pair-distribution-function and magnetization measurements were used to determine changes in short-range ordering, particle size and microstructure, while high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) were used to measure the atomic-level structure of individual particles and map the phase distribution in the initial and fully lithiated electrodes. Both FeF(2) and CuF(2) react with lithium via a direct conversion process with no intercalation step, but there are differences in the conversion process and final phase distribution. During the reaction of Li(+) with FeF(2), small metallic iron nanoparticles (<5 nm in diameter) nucleate in close proximity to the converted LiF phase, as a result of the low diffusivity of iron. The iron nanoparticles are interconnected and form a bicontinuous network, which provides a pathway for local electron transport through the insulating LiF phase. In addition, the massive interface formed between nanoscale solid phases provides a pathway for ionic transport during the conversion process. These results offer the first experimental evidence explaining the origins of the high lithium reversibility in FeF(2). In contrast to FeF(2), no continuous Cu network was observed in the lithiated CuF(2); rather, the converted Cu segregates to large particles (5-12 nm in diameter) during the first discharge, which may be partially responsible for the lack of reversibility in the CuF(2) electrode. 相似文献
866.
Michael I. Bruce Martyn Jevric Wyona Patalinghug Brian W. Skelton Natasha N. Zaitseva 《Journal of organometallic chemistry》2008,693(17):2915-2920
Addition of [I(py)2]BF4 to Ru(CCH)(dppe)Cp∗ gave the iodovinylidene [Ru(CCHI)(dppe)Cp∗]BF41, which could be deprotonated to Ru(CCI)(dppe)Cp∗ 2. The attempted preparation of Ru(CCCCI)(dppe)Cp∗, followed by derivatisation with tcne, gave the dienynyl Ru{CCC[C(CN)2]CIC(CN)2}(dppe)Cp∗ 3. The Pd(0)/Cu(I)-catalysed reaction of 3 with Ru{CCCCAu(PPh3)}(dppe)Cp∗ afforded Ru{CCCC(CN)2CC(CN)2Au(PPh3)}(dppe)Cp∗ 4 by formal replacement of I+ by [Au(PPh3)]+. XRD structures of 1-4 are reported. 相似文献
867.
Dr. Natasha Eccles Dr. Flavio della Sala Dr. Bryden A. F. Le Bailly Dr. George F. S. Whitehead Prof. Jonathan Clayden Dr. Simon J. Webb 《ChemistryOpen》2020,9(3):338-345
Two α-aminoisobutyric acid (Aib) foldamers bearing Zn(II)-chelating N-termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group). Replacement of the quinolinyl arms of the BQPA-capped foldamer with pyridyl gave a BPPA-capped foldamer, then further replacement of the linking pyridyl with a 1,2,3-triazole gave a BPTA-capped foldamer. Their ability to relay chiral information from carboxylate bound to Zn(II) at the N-terminus to a glycinamide-based NMR reporter of conformational preference at the C-terminus was measured. The importance of the quinolinyl arms became readily apparent, as the foldamers with pyridyl arms were unable to report on the presence of chiral carboxylate in acetonitrile. Low solubility, X-ray crystallography and 1H NMR spectroscopy suggested that interfoldamer interactions inhibited carboxylate binding. However changing solvent to methanol revealed that the end-to-end relay of chiral information could be observed for the Zn(II) complex of the BPTA-capped foldamer at low temperature. 相似文献
868.
869.
Mesoscopic simulation of an ionomeric membrane based on sulfonated aromatic poly(ether ether ketone)
Mesoscopic simulation in the framework of the mesoscopic dynamics method (a version of the dynamic density functional method)
was performed for a proton conducting membrane based on sulfonated aromatic poly(ether ether ketone) in a wide range of water
content in the system. For the selected parametric field, the model demonstrates microphase separation of hydrophilic and
hydrophobic segments of the polymer. In the bulk of the membrane, a spatial network of water channels forms, whose walls consist
of polar (sulfonated) units of the macromolecule. Independent molecular dynamics simulation for one set of parameters gives
close values of the structural characteristics of the membrane, which confirms the correctness of the mesoscopic model. 相似文献
870.
-Trialkylstannylacetylenes react under mild conditions with metallic sodium at the Sn-C(sp) bond to give hexaalkyldistannanes and sodium acetylalkynides inca. 65–85 % yields.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1109–1110, June, 1994. 相似文献