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151.
The structure of stable [C9H11]+ ions from different model compounds with the molecular formula C9H11Cl has been estimated by energy measurements. It has further been shown that acetylenic compounds cyclise to form aromatic ions in the range of the appearance potentials. 相似文献
152.
153.
Christof Schmitz Ahmed Mourran Helmut Keul Martin Möller Martina Keerl Walter Richtering 《Colloid and polymer science》2009,287(10):1183-1193
The effect of microstructure on the aggregation behaviour of symmetrical di- and triblock copolymers P(BMA)-b-P(MAA) and P(BMA)-b-P(BMA-co-MAA)-b-P(MAA) with a molecular weight of 40,000 g/mol was studied. The critical micelle concentration, hydrodynamic radius and morphology
of the micelles were determined by fluorescence spectroscopy, dynamic light scattering and scanning force microscopy (SFM).
Whereas no effect of the microstructure on the critical micelle concentration could be detected, the hydrodynamic radius decreased
from di- to triblock copolymer from 53 to 36 nm. The decrease of about 32% corresponds to the length of the random middle
block within the triblock copolymer so that the reduction in hydrodynamic radius was caused by a complete orientation of the
random middle block at the core corona interface. Finally, the SFM investigation showed that dehydration of micelles on a
substrate is accompanied by formation of a physisorbed monolayer with a thickness of 2 nm on which the micelles are deposited. 相似文献
154.
Functionalized 4-nitro- and 4-aminophenols were regioselectively prepared based on [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-ethoxy-2-nitro-2-en-1-ones. 相似文献
155.
Daniel Göbke Yuriy Romanyshyn Sébastien Guimond Jacobus Marinus Sturm Dr. Helmut Kuhlenbeck Dr. Jens Döbler Dr. Ulrike Reinhardt Maria Veronica Ganduglia‐Pirovano Dr. Joachim Sauer Prof. Dr. Hans‐Joachim Freund Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(20):3695-3698
Hydroxy‐mediated methoxy formation or stabilization is probably an important process in many methanol adsorption systems. Hydrogen atoms originating from the scission of the methanol O? H bond react with the substrate and form water. This process may result 1) in the production of additional surface defects as reactive centers for methoxy formation and 2) in the stabilization of methoxy groups by suppression of methanol formation.
156.
157.
Xiaoqing Zeng Helmut Beckers Helge Willner Raphael J. F. Berger Stuart A. Hayes Norbert W. Mitzel 《ChemInform》2011,42(19):no-no
The title compound is characterized by IR (gas phase, Ar matrix), Raman (liquid, amorphous, and crystalline solid), and 19F, 31P, 14N and 15N NMR spectroscopy, as well as by quantum chemical DFT calculations. 相似文献
158.
Andrushchenko V Tsankov D Krasteva M Wieser H Bour P 《Journal of the American Chemical Society》2011,133(38):15055-15064
The four-stranded G-quadruplex motif is a conformation frequently adopted by guanine-rich nucleic acids that plays an important role in biology, medicine, and nanotechnology. Although vibrational spectroscopy has been widely used to investigate nucleic acid structure, association of particular spectral features with the quadruplex structure has to date been ambiguous. In this work, experimental IR absorption and vibrational circular dichroism (VCD) spectra of the model quadruplex systems d(G)(8) and deoxyguanosine-5'-monophosphate (5'-dGMP) were analyzed using molecular dynamics (MD) and quantum-chemical modeling. The experimental spectra were unambiguously assigned to the quadruplex DNA arrangement, and several IR and VCD bands related to this structural motif were determined. Involvement of MD in the modeling was essential for realistic simulation of the spectra. The VCD signal was found to be more sensitive to dynamical structural variations than the IR signal. The combination of the spectroscopic techniques with multiscale simulations provides extended information about nucleic acid conformations and their dynamics. 相似文献
159.
Sulfuryl diazide, O(2)S(N(3))(2), previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 °C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C(2)) conformer to be 6.6 kJ mol(-1) lower in energy than the syn (C(s)) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO(2)N(3), has also been prepared and characterized by IR and Raman spectroscopy. 相似文献
160.
Paul Kosma Martina Strobl Andreas Hofinger Jens Ø. Duus Bent O. Petersen Klaus Bock Helmut Brade 《Monatshefte für Chemie / Chemical Monthly》2002,133(4):561-570
Summary. Methyl glycosides of Kdo and a (2→8)-linked Kdo disaccharide were prepared which contain a deuterium label at C-8 of the reducing unit. The label was introduced in fair
diastereoselectivity upon reduction of an aldehyde group using a chiral borane complex derived from N-benzyloxycarbonyl-(S)-proline which produced the 8-(S)-deuterated derivative as the major isomer. Further coupling with a Kdo bromide gave the α-(2→8)-linked disaccharide in good yield. The deprotected disaccharide serves as a model for NMR spectroscopic
studies on the side chain conformation of a carbohydrate epitope from the bacterial pathogen Chlamydia.
Received September 17, 2001. Accepted October 17, 2001 相似文献