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91.
Dispersed fluorescence spectra of jet-cooled hydrogen-bonded phenols have been observed by excitation of intra- and inter-molecular vibrational levels. The spectra show that vibrational energy redistribution occurs from the excited vibronic level into intermolecular vibrational modes. Energy redistribution within the intermolecular vibrational modes was also found. 相似文献
92.
Jinkui Chai Wei Ding Chen Wang Shingo Ito Junliang Wu Naohiko Yoshikai 《Chemical science》2021,12(45):15128
The Ritter reaction, Brønsted- or Lewis acid-mediated amidation of alkene or alcohol with nitrile via a carbocation, represents a classical method for the synthesis of tertiary amides. Although analogous reactions through a vinyl cation or a species alike may offer a route to enamide, an important synthetic building block as well as a common functionality in bioactive compounds, such transformations remain largely elusive. Herein, we report a Ritter-type trans-difunctionalization of alkynes with a trivalent iodine electrophile and nitrile, which affords β-iodanyl enamides in moderate to good yields. Mediated by benziodoxole triflate (BXT), the reaction proves applicable to a variety of internal alkynes as well as to various alkyl- and arylnitriles. The benziodoxole group in the product serves as a versatile handle for further transformations, thus allowing for the preparation of various tri- and tetrasubstituted enamides that are not readily accessible by other means.Ritter-type trans-selective iodo(iii)amidation of internal alkynes with benziodoxole triflate and various nitriles has been achieved for the stereocontrolled synthesis of multisubstituted enamides. 相似文献
93.
Recent advances in the research field of supramolecularly engineered dye aggregates have enabled the design of simple one-dimensional stacks such as fibers and of closed structures such as nanotoroids (nanorings). More complex and advanced supramolecular systems could potentially be designed using a molecule that is able to provide either of these distinct nanostructures under different conditions. In this study, we introduced bulky but strongly aggregating cholesterol units to a scissor-shaped azobenzene dyad framework, which affords either nanotoroids, nanotubes, or 1D fibers, depending on the substituents. This new dyad with two trans-azobenzene arms shows supramolecular polymorphism in its temperature-controlled self-assembly, leading to not only oligomeric nanotoroids as kinetic products, but also to one-dimensional fibers as thermodynamic products. This supramolecular polymorphism can also be achieved via photo-triggered self-assembly, i.e., irradiation of a monomeric solution of the dyad with two cis-azobenzene arms using strong visible light leads to the preferential formation of nanotoroids, whereas irradiation with weak visible light leads to the predominant formation of 1D fibers. This is the first example of a successful light-induced modulation of supramolecular polymorphism to produce distinctly nanostructured aggregates under isothermal conditions.Introduction of the bulky yet strongly aggregating cholesterol units to an azobenzene dyad lead to a supramolecular polymorphism not only in its temperature-controlled but also in photo-triggered self-assembly, leading to toroids and helical fibers. 相似文献
94.
95.
The magnetic hyperfine structure of atoms is studied. A new compact expression is introduced for the magnetic hyperfine anomaly. A theoretical foundation is given for an empirical formula discovered by Moskowitz and Lombardi. The effects of core polarization and mesonic exchange currents are discussed. There are two kinds of core polarization, Δl = 0 and Δl = 2. The latter is shown to be important to explain certain isotope shifts, though it is smaller than the former Δl = 0 effect. 相似文献
96.
Kinoshita N Marx KH Tanaka K Tsubaki K Kawabata T Yoshikai N Nakamura E Fuji K 《The Journal of organic chemistry》2004,69(23):7960-7964
Iridium-catalyzed asymmetric allylic alkylation of monoaryl substrates 4-6 with chiral phosphites 1-3 has been investigated. Although branched isomers were formed with high regioselectivities, the enantioselectivities of these products were remarkably influenced by solvents, countercations, and additives (ZnCl(2) and LiCl). 相似文献
97.
Local structures around germanium in liquid germanate have been investigated by means of in situ x-ray absorption measurements up to 9 GPa at 1273 K. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated germanium becomes stable. The GeO6 octahedron in the high-density liquid is more compressible than that in solids. 相似文献
98.
Fumitoshi Hirayama Makoto Kamada Hideki Yano Koichi Udo Hidetoshi Arima Kaneto Uekama 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):159-161
6A-O-[2-(3-benzoylphenyl)propinoyl]--cyclodextrin (KP/-CyD conjugate), in which an anti-inflammatory drug, ketoprofen (KP), is covalently bound to one of the primary hydroxyl groups of -cyclodextrin, was prepared, and the CyD conjugate-based prolonged-release system was designed by combining the KP/-CyD conjugate (used as a delayed-release fraction) with the KP/ethylcellulose (EC) solid dispersion (used as a slow-release fraction). The conjugate showed a typical delayed-release pattern after oral administration to rats, i.e., plasma levels of KP increased after a lag time of about 3 h and reached a maximum concentration at about 9 h. The co-administration of the conjugate and the EC solid dispersion gave a sustained-release pattern of KP, i.e., a constant plasma KP level was maintained for at least 24 h. The long circulating release patterns in plasma KP levels after oral administration were reflected in the anti-inflammatory effect using with carrageenan-induced acute edema in rat paw. 相似文献
99.
Dramatic Mechanistic Change in Acid‐Catalyzed Arylation of Azafulleroids Depending on their Ambident N/C Basicity: Formation of Cyclopentene Centered Pentakisadduct 下载免费PDF全文
Dr. Naohiko Ikuma Yuta Doi Koichi Fujioka Tsubasa Mikie Dr. Ken Kokubo Prof. Dr. Takumi Oshima 《化学:亚洲杂志》2014,9(11):3084-3088
Azafulleroid, amino‐bridged [5,6]‐open fullerene, has the ambident N/C basicity of the incorporated enamine moiety. Acid‐catalyzed arylation of N‐substituted azafulleroids proceeded via two types of initial N/C protonation to perform monoarylation or 1,4‐bisarylation for the N‐alkyl substituents and shuttlecock‐type pentakisarylation for the N‐phenyl substituent. The dramatic product change was explained by considering the possible mechanism as well as the DFT computational results. 相似文献
100.
Kaho Tanaka Naohiko Akasaka Tomoyuki Kosai Shunya Honda Yuya Ushijima Shintaro Ishida Takeaki Iwamoto 《Molecules (Basel, Switzerland)》2021,26(6)
π-Electron systems of silicon have attracted attention because of their narrow HOMO-LUMO gap and high reactivity, but the structural diversity remains limited. Herein, new dialkylboryl-substituted disilenes were synthesized by the selective desilylation-borylation of the corresponding trimethylsilyl-substituted disilenes. The dialkylboryl-substituted disilenes were fully characterized by a combination of NMR spectroscopy, MS spectrometry, single-crystal X-ray diffraction analysis, and theoretical calculations. The longest-wavelength absorption bands of boryldisilenes were bathochromically shifted compared to the corresponding silyl-substituted disilenes, indicating a substantial conjugation between π(Si=Si) and vacant 2p(B) orbitals. In the presence of 4-(dimethylamino)pyridine (DMAP), the dialkylboryl groups in the boryl-substituted disilenes were easily converted to trimethylsilyl groups, suggesting the dialkylboryl-substituted disilenes in the presence of a base serve as the surrogates of disilenyl anions (disilenides). 相似文献