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991.
Smith RM Chienthavorn O Saha S Wilson ID Wright B Taylor SD 《Journal of chromatography. A》2000,886(1-2):289-295
Superheated deuterium oxide has been investigated as an eluent for reversed-phase HPLC on a polystyrene-divinylbenzene column with UV, 1H NMR and MS detection using a series of sulfonamides as model compounds. In the course of these studies, a selective, specific and efficient deuteration of the methyl groups on a pyrimidine ring was observed during chromatography of certain of the sulfonamides. The potential of this methodology for producing deuterium-labelled compounds from substances bearing suitable substituents is considered. The utility of HPLC-NMR-MS as a means for studying on-column reactions is discussed. 相似文献
992.
Saha Badal C. Dien Bruce S. Bothast Rodney J. 《Applied biochemistry and biotechnology》1998,(1):115-125
Corn fiber, which consists of about 20% starch, 14% cellulose, and 35% hemicellulose, has the potential to serve as a low
cost feedstock for production of fuel ethanol. Currently, the use of corn fiber to produce fuel ethanol faces significant
technical and economic challenges. Its success depends largely on the development of environmentally friendly pretreatment
procedures, highly effective enzyme systems for conversion of pretreated corn fiber to fermentable sugars, and efficient microorganisms
to convert multiple sugars to ethanol. Several promising pretreatment and enzymatic processes for conversion of corn fiber
cellulose, hemicellulose, and remaining starch to fermentable sugars were evaluated. These hydrolyzates were then examined
for ethanol production in bioreactors, using genetically modified bacteria and yeast. Several novel enzymes were also developed
for use in pretreated corn fiber saccharification.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
993.
Majji Shankar Arijit Saha Somratan Sau Arghadip Ghosh Vincent Gandon Akhila K. Sahoo 《Chemical science》2021,12(18):6393
An unconventional cobalt(iii)-catalyzed one-pot domino double annulation of aryl thioamides with unactivated alkynes is presented. Sulfur (S), nitrogen (N), and o,o′-C–H bonds of aryl thioamides are involved in this reaction, enabling access to rare 6,6-fused thiopyrano-isoquinoline derivatives. A reverse ‘S’ coordination over a more conventional ‘N’ coordination of thioamides to the Co-catalyst specifically regulates the formation of four [C–C and C–S at first and then C–N and C–C] bonds in a single operation, a concept which is uncovered for the first time. The power of the N-masked methyl phenyl sulfoximine (MPS) directing group in this annulation sequence is established. The transformation is successfully developed, building a novel chemical space of structural diversity (56 examples). In addition, the late-stage annulation of biologically relevant motifs and drug candidates is disclosed (17 examples). The preliminary photophysical properties of thiopyrano-isoquinoline derivatives are discussed. Density functional theory (DFT) studies authenticate the participation of a unique 6π-electrocyclization of a 7-membered S-chelated cobaltacycle in the annulation process.A Co-catalyzed one-pot double annulation of sulfoximine bearing thioamides with alkynes for the synthesis of [6,6]-fused thiopyrano-isoquinolines is disclosed. The annulation involves a 6π-electrocyclization of 7-membered S-chelated cobaltacycle. 相似文献
994.
Sushanta?Saha Pradip?Kumar?Ghosh Ambikesh?MahapatraEmail author 《Transition Metal Chemistry》2005,30(6):706-711
Nucleophilic substitution of Pd(RaaiR′)Cl2 [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R—C6H4— N=N—C3H2NN-1-R′; where R= H(a)/Me(b)/Cl(c) and R′ = Et(1)/Bz(2)] with adenine (A) in MeCN–water (1:1) at 298 K, to form [Pd(A)2]Cl2, has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support a nucleophilic association path. The reaction follows the rate law, rate = {a+k [A] 02[Pd(RaaiR′)Cl2]: first-order in Pd(RaaiR′)Cl2 and second-order in A. The rate increases as follows: Pd(RaaiEt)Cl2(1) < Pd(RaaiBz)Cl2(2) and Pd(MeaaiR′)Cl2(b) < Pd(HaaiR′)Cl2(a) < Pd(ClaaiR′)Cl2(c). External addition of Cl− (LiCl) suppresses the rate (rate 1/[Cl−]). The activation parameters,
H0 and
S0
of the reactions were calculated from the Eyring plot and support the proposed mechanism. 相似文献
995.
Ritz variational calculation for the singly excited states of compressed two‐electron atoms 下载免费PDF全文
Jayanta K. Saha Sukhamoy Bhattacharyya Tapan K. Mukherjee 《International journal of quantum chemistry》2016,116(23):1802-1813
A detailed analysis on the effect of spherical impenetrable confinement on the structural properties of two‐electron ions in states has been performed. The energy values of 1sns [ ] ( ) states of helium‐like ions ( ) are estimated within the framework of Ritz variational method using explicitly correlated Hylleraas‐type basis sets. The correlated wave functions used here are consistent with the finite boundary conditions due to spherical confinement. A comparative study between the singlet and triplet states originating from a particular electronic configuration shows incidental degeneracy and the subsequent level‐crossing phenomena. The thermodynamic pressure felt by the ion inside the sphere pushes the energy levels toward continuum. Critical pressures for the transition to strong confinement regime (where the singly excited two‐electron energy levels cross the corresponding one‐electron threshold) as well as for the complete destabilization are also estimated. 相似文献
996.
Sudipta?Saha S.?K.?Mohanta Sayani?Biswas R.?Palit S.?N.?MishraEmail author 《Hyperfine Interactions》2016,237(1):121
The magnetic hyperfine field of Ba in ferromagnetic Ni has been measured by time differential perturbed angular distribution technique using the 13 ns 10+ isomeric state in 132Ba as probe which was populated in the reaction 12C(124Sn, 4n) 132Ba at beam energy of 60 MeV. The hyperfine field extracted from the observed Larmor precession frequency comes out to be ?84(5) kG. Our experimental results show good agreement with theoretical calculations performed within local density approximation of the density functional theory. The hyperfine field data presented here would be useful towards accurate determination of g-factor in other high spin states in Ba isotopes. 相似文献
997.
A novel attempt for finding comparatively accurate solution for sine‐Gordon equation comprising Riesz space fractional derivative 下载免费PDF全文
In this paper, a numerical procedure involving Chebyshev wavelet method has been implemented for computing the approximate solution of Riesz space fractional sine‐Gordon equation (SGE). Two‐dimensional Chebyshev wavelet method is implemented to calculate the numerical solution of space fractional SGE. The fractional SGE is considered as an interpolation between the classical SGE (corresponding to α = 2) and nonlocal SGE (corresponding to α = 1). As a consequence, the approximate solutions of fractional SGE obtained by using Chebyshev wavelet approach were compared with those derived by using modified homotopy analysis method with Fourier transform. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
998.
SERS Enhancement on the Basis of Temperature‐Dependent Chemisorption: Microcalorimetric Evidence 下载免费PDF全文
Chandra Nath Roy Dr. Debasmita Ghosh Dr. Somrita Mondal Somashree Kundu Susmita Maiti Dr. Abhijit Saha 《Chemphyschem》2016,17(24):4144-4148
The mechanism of surface‐enhanced Raman spectroscopy (SERS) is not very clear in view of the magnitude of the contribution of electromagnetic factor as well as the chemical mechanism. This report presents the extent of adsorption at different temperatures in terms of signal enhancements in SERS employing silver nanoparticles (AgNPs) of various shapes as substrate and dye molecules, crystal violet or Rhodamine 6G, as model Raman probes. Initially, the SERS signal increases with increasing temperature until a maximum intensity is reached, before it gradually decreases with increasing temperature. This trend is independent of the shape of the Raman substrates and probes. However, the temperature at which maximum intensity is obtained may depend upon the nature of the Raman probe. The energetics involved in the chemisorption process between dye molecules and AgNPs were determined through isothermal titration calorimetry and their implications for the observed SERS signals were assessed. The maximum heat change occurred at the temperature at which the maximum signal enhancement in SERS was obtained and the enhanced interaction at optimum temperature was confirmed by absorption spectroscopy. 相似文献
999.
Dr. Bharat Kumar Dr. Gyandshwar Kumar Rao Soumen Saha Prof. Ashok K. Ganguli 《Chemphyschem》2016,17(1):155-161
Herein, we report the synthesis of Cu/Cu2O nanocomposites by a one‐step hydrothermal process at 180 °C, for which the resulting morphology is dependent on the hydrothermal reaction time (24, 72, and 120 h). With a longer reaction time of 120 h, a rod‐shape morphology is obtained, whereas at 72 and 24 h assemblies of nanoparticles are obtained. The rod‐shaped (120 h) particles of the Cu/Cu2O nanocomposites show a much higher efficiency (6.3 times) than the agglomerates and 2.5 times more than the assemblies of nanoparticles for the hydrogen‐evolution reaction. During the oxygen‐evolution reaction, the nanorods produce a current that is 5.2 and 3.7 times higher than that produced by the agglomerated and assembled nanoparticles, respectively. The electrocatalysts are shown to be highly stable for over 50 cycles. As catalysts for organic synthesis, a 100 % yield is achieved in the Sonogashira cross‐coupling reaction with the nanorods, which is higher than with the other nanocomposite particles. This result demonstrates the significant enhancement of yield obtained with the nanorods for cross‐coupling reactions. 相似文献
1000.
Platchkov S Pomatsalyuk R Prout DL Punjabi VA Pussieux T Quemener G Ransome RD Ravel O Roblin Y Roche R Rowntree D Rutledge GA Rutt PM Saha A Saito T Sarty AJ Serdarevic-Offermann A Smith TP Soldi A Sorokin P Souder P Suleiman R Templon JA Terasawa T Todor L Tsubota H 《Physical review letters》2000,84(15):3265-3269
We have measured the cross section for quasielastic 1p-shell proton knockout in the 16O(e,e(')p) reaction at omega = 0.439 GeV and Q2 = 0.8 (GeV/c)(2) for missing momentum P(miss)=355 MeV/c. We have extracted the response functions R(L+TT), R(T), R(LT), and the left-right asymmetry, A(LT), for the 1p(1/2) and the 1p(3/2) states. The data are well described by relativistic distorted wave impulse approximation calculations. At large P(miss), the structure observed in A(LT) indicates the existence of dynamical relativistic effects. 相似文献