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941.
Mandal Madhuri Ranjan Jana Nikhil Kundu Subrata Kumar Ghosh Sujit Panigrahi Mruganka Pal Tarasankar 《Journal of nanoparticle research》2004,6(1):53-61
This paper reports the evolution of a new class of core–shell type, that is, Aucore–Agshell bimetallic nanoparticles by seed mediated technique for surface enhanced Raman scattering (SERS) study. Here it is demonstrated how to control the thickness of Ag-shell with the variation of gold seed (15 nm) to Ag ion concentration which in turn control the particle size in the range from 50 to 100 nm with increase of shell thickness. For 50 nm core–shell particles the thickness of the shell was 17 nm, for 70 nm particles the thickness was 27 nm and for 100 nm the thickness was 42 nm. SERS study was performed on those particles using the analyte crystal violet (CV) to examine the impact of the size and field effects of the bimetallics on SERS spectra. A surprising finding is that a small particle as low as 50 nm have been found to be highly efficient for SERS, even it enables the detection of a selected dye molecule down to single molecular level. The sensitivity of the SERS detection limit has been improved further with an activating reagent like NaCl. The newly modeled bimetallic system establishes a relationship between the local electromagnetic (EM) field effect and chemical effect (CE) on the enhancement of SERS spectra, which provides further insight into the enhancement mechanism of SERS. 相似文献
942.
An amine-templated cobalt(II) sulfate with the kagome lattice, prepared for the first time, exhibits magnetic properties comparable to those of the analogous Fe(III) compounds. 相似文献
943.
The highly active Friedel-Crafts alkylation (FCA) catalyst, [Ir(COD)Cl(SnCl3)(SnCl4)(arene)]+Cl- (1-SnCl4), is easily generated in one-pot from [Ir(COD)Cl]2 or [Ir(COD)(mu-Cl)Cl(SnCl3)]2 (1) and SnCl4. The reaction of arenes, heteroarenes with benzyl, and allyl alcohols is promoted by 1-SnCl4 (1 mol %) with high turnover frequency. Kinetic evidence is presented to establish FCA pattern. From dual-catalyst combination studies varying the transition metal and main group metal partner, the efficiency of the present catalysts is attributed to the electrophilic "IrIII-SnIV" core. 相似文献
944.
Sengupta S Drew MG Mukhopadhyay R Achari B Banerjee AK 《The Journal of organic chemistry》2005,70(19):7694-7700
[reaction: see text] An efficient, flexible, and stereoselective convergent route for constructing the trans-10-hydroxy-1,1-dimethyloctahydrodibenzo[a,d]cyclohepten-7-ones (5a-c) was achieved via intramolecular Heck reaction. This strategy has been successfully implemented for the syntheses of (+/-)-komaroviquinone (3) through (+/-)-coulterone dimethyl ether (5c) and (+/-)-faveline methyl ether (1a). 相似文献
945.
Choudhury Utpal Roy Banerjee Saumen Banerjee Rupendranath 《Transition Metal Chemistry》2002,27(1):42-46
In aqueous acid, hydrazine reduces [MnIV
3(-O)4(bipy)4(H2O)2]4+, (1), quantitatively to [MnIII,IV
2(-O)2(bipy)4]3+, (2), and Mn2+ if [N2H+
5] 2 × (stoichiometric amount). At higher [N2H+
5], reduction proceeds up to Mn2+. The reduction of (1) to (2) is strongly catalysed by Mn2+ and the absorbance (A
t
) versus time (t) graphs have sigmoidal shapes. The graphs become steeper with increasing amounts of added Mn2+ and N2H+
5, but remain unchanged when [H+] is changed. The A
t
– t graphs, under various experimental conditions, can all be simulated with a single set of second order rate constants, estimated for the individual steps in a proposed reaction scheme, in which the catalytic action of Mn2+ involves a one-electron and a two-electron reduced form of (1), but not (1) itself. The absence of any proton-dependence of the reaction rate refutes an electroprotic mechanism and an inner-sphere mechanism appears to be most likely for the reduction of (1) by N2H+
5 相似文献
946.
A layered iron sulfate of the composition [H3N(CH2)2NH2(CH2)2NH2(CH2)2NH3][FeII3F6(SO4)2], possessing a distorted Kagome lattice, prepared hydrothermally, is found to exhibit magnetic hysteresis like a ferrimagnet besides the characteristics of a frustrated system, like those of a spin glass. 相似文献
947.
948.
[reaction: see text] The reaction of ketone enolates with phosphonate aldehyde 2 afforded cyclopentenols 3 or keto esters 4 in a one-pot procedure. 相似文献
949.
Sudhansu S. Biswal Debajyoti Choudhury Rohini M. Godbole Ritesh K. Singh 《Pramana》2007,69(5):777-782
We examine, in a model independent way, the sensitivity of a linear collider to the couplings of a light Higgs boson to a
pair of gauge bosons, including the possibility of CP violation. We construct several observables that probe the various possible
anomalous couplings. For an intermediate mass Higgs, a collider operating at a center of mass energy of 500 GeV and with an
integrated luminosity of 500 fb−1 is shown to be able to constrain the ZZH vertex at the few per cent level, with even higher sensitivity for some of the couplings. However, lack of sufficient number
of observables as well as contamination from the ZZH vertex limits the precision to which anomalous part of the WWH coupling can be probed.
相似文献
950.
In case of spacetimes with single horizon, there exist several well- established procedures for relating the surface gravity
of the horizon to a thermodynamic temperature. Such procedures, however, cannot be extended in a straightforward manner when
a spacetime has multiple horizons. In particular, it is not clear whether there exists a notion of global temperature characterizing
the multi-horizon spacetimes. We examine the conditions under which a global temperature can exist for a spacetime with two
horizons using the example of Schwarzschild–De Sitter (SDS) spacetime. We systematically extend different procedures (like
the expectation value of stress tensor, response of particle detectors, periodicity in the Euclidean time etc.) for identifying
a temperature in the case of spacetimes with single horizon to the SDS spacetime. This analysis is facilitated by using a
global coordinate chart which covers the entire SDS manifold. We find that all the procedures lead to a consistent picture
characterized by the following features: (a) In general, SDS spacetime behaves like a non-equilibrium system characterized
by two temperatures. (b) It is not possible to associate a global temperature with SDS spacetime except when the ratio of
the two surface gravities is rational. (c) Even when the ratio of the two surface gravities is rational, the thermal nature
depends on the coordinate chart used. There exists a global coordinate chart in which there is global equilibrium temperature
while there exist other charts in which SDS behaves as though it has two different temperatures. The coordinate dependence
of the thermal nature is reminiscent of the flat spacetime in Minkowski and Rindler coordinate charts. The implications are
discussed. 相似文献