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961.
Ying‐Fang Ting Chihliang Chang Raju Jannapu Reddy Dr. Dhananjay R. Magar Kwunmin Chen Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(23):7030-7038
Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl–camphor derivatives ( 7 a–h ). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical α,α‐disubstituted aldehydes to β‐nitroalkenes. When this asymmetric transformation was catalyzed by organocatalyst 7 f , the desired Michael adducts were obtained in high chemical yields, with high to excellent stereoselectivities (up to 98:2 diastereomeric ratio (d.r.) and 99 % enantiomeric excess (ee)). The scope of the catalytic system was expanded to encompass various aldehydes and ketones as the donor sources. The synthetic application was demonstrated by the synthesis of a tetrasubstituted‐cyclohexane derivative from (S)‐citronellal, with high stereoselectivity. 相似文献
962.
A. Sakunthala M. V. Reddy S. Selvasekarapandian B. V. R. Chowdari H. Nithya P. Chirstopher Selvin 《Journal of Solid State Electrochemistry》2010,14(10):1847-1854
The compound, lithium trivanadate (LiV3O8), was synthesized by the polymer precursor method, using the polymer polyvinylpyrrolidone. The electrochemical performance
of LiV3O8 was compared with LiV3O8 synthesized by the solid state reaction method. The prepared compounds were characterized by X-ray diffraction, scanning
electron microscopy, and high-resolution transmission electron microscopy techniques. The electrochemical performances were
studied by cyclic voltammetry and galvanostatic cycling in the voltage range of 2.0 to 4.0 V at room temperature (25 °C).
The compound prepared by the polymer precursor method was found to have a good cycling stability. A reversible capacity value
of 203 mAh/g (2.18 mol of Li) and 170 mAh/g (1.83 mol of Li) was obtained at the end of the 70th cycle, at a current density
of 30 and 120 mA/g, respectively. 相似文献
963.
P. Muralidhar Reddy Wan-Yu Hsu Jun-Fu Hu Yen-Peng Ho 《Journal of the American Society for Mass Spectrometry》2010,21(3):421-424
Microwave-assisted proteolytic digestion often yields misscleaved peptides, attributed to incomplete hydrolysis reactions
between enzymes and substrates. The number of missed cleavages is an important parameter in proteome database searching. This
study investigates how various factors affect digestion processes. Optimum conditions for microwave-assisted digestion (50
mM Tris buffer, 30 min at 60°C, and enzyme to protein molar ratio of 1:5) were determined. The digestion products obtained
from eight standard proteins were characterized based on matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS).
Experimental results indicate that the digestion temperature, reaction time, enzyme to substrate ratio, and digestion buffer
affect the number of misscleaved peptides and incomplete digestion percentages. Although all protein molecules in a sample
could be digested into peptides within a few minutes under microwave irradiation, longer reaction times or methods to maximize
the enzyme activity should be considered if digestion completeness is a major concern. 相似文献
964.
M. Penchal Reddy W. Madhuri N. Ramamanohar Reddy V.R.K. Murthy R. Ramakrishna Reddy 《Journal of magnetism and magnetic materials》2010,322(19):2819-2823
The low temperature microwave sintered NiCuZn and MgCuZn ferrites with compositions Ni0.35Cu0.05Zn0.60Fe2O4 and Mg0.35Cu0.05Zn0.60Fe2O4 were synthesized by conventional mixed oxide method. NiCuZn and MgCuZn ferrite samples obtained showed better sintered densities at 950 and 900 °C, respectively. The scanning electron micrographs of both the ferrite samples appear to be very much similar. The magnitude of initial permeability of MgCuZn ferrite samples is found to be obviously higher than those of NiCuZn ferrite samples at all sintering temperatures. This is mainly due to the fact that MgCuZn ferrite has smaller magnetocrystalline anisotropy constant and magnetostrictive constant. NiCuZn ferrites have higher saturation magnetization than MgCuZn ferrites, which is due to the higher magnetic moment of NiCuZn ferrites. Our results indicate that the microwave sintering method seems to be a potential technique in the MLCI technology. 相似文献
965.
N. Y. Sreedhar P. Reddy Prasad M. Sankara Nayak D. Rekha C. Nageswara Reddy 《中国化学会会志》2009,56(6):1139-1146
In the present paper novel column solid phase extraction procedure was developed for the determination of Cd(II) and Pb(II) in cows', goats', ewes', buffalos' and humans' milk samples using newly synthesized reagent 2,2′‐DPED3P (2,2′‐{[1,2‐diphenylethane‐1,2‐diylidene]dinitrilo}diphenol) for preconcentration and separation prior to differential pulse polarography using amberlite XAD‐2 in the ranges of pH 4.0–5.0. The sorbed elements were subsequently eluted with 10 mL of 2 M HCl elutes were analysed by differential pulse polarography (DPP). The interference of foreign ions has also been studied. Effects of various instrumental parameters are investigated and received conditions are optimized. The total metal concentration of the milk samples in the study area were in the following ranges 0.030–0.090 μg L?1 of Cd(II), 0.009–0.026 μg L?1 of Pb(II) respectively. The limits of detections were found to be 0.020 and 0.024 μg L?1 for Cd(II) and Pb(II) respectively by applying a preconcentration factor ~40. The proposed enrichment method was applied successfully for the determination of metal ions in cows', goats', ewes', buffalos' and humans' milk samples. 相似文献
966.
Attempts to synthesise iso-cladospolide-B, cladospolide-B and cladospolide-C resulted in macrolides 1, 2 and 4 along with butenolide 3. Of the three stereogenic centres, the C-4/C-5 vic-diol was obtained from tartaric acid and d-glucose, while the C-11 stereocentre was created by Jacobsen’s method. 相似文献
967.
968.
Lakshmi VV Reddy TJ Murty MR Prabhakar S Vairamani M 《Rapid communications in mass spectrometry : RCM》2006,20(14):2209-2214
The detection and identification of degradation products of scheduled chemicals, which are characteristic markers of Chemical Warfare agents (CWAs), plays a key role in verification analysis. Identification of such non-scheduled but specific markers of CWAs helps in deciphering the kind of agent that was present in the sample submitted for off-site analysis. This paper describes the stability of N,N-dialkylaminoethyl-2-chlorides, which are precursors for highly toxic chemicals like VX, in different solvents. These compounds are stable in chloroform, acetonitrile, hexane and dichloromethane but tend to undergo in situ nucleophilic substitution reaction in the presence of alcohols giving the corresponding alkyl ether. The study shows that N,N-dialkylaminoethyl alkyl ethers can be used as markers of N,N-dialkylaminoethyl-2-chlorides. A detailed degradation study of these compounds in the presence of alcohols was carried out and it was found that the reaction follows pseudo-first order kinetics. Electron ionization mass spectral data for the methyl ethers of all the compounds are briefly discussed. 相似文献
969.
Reddy PN Srikanth R Srinivas R Sharma VU Sharma GV Nagendar P 《Rapid communications in mass spectrometry : RCM》2006,20(22):3351-3360
Dissociation pathways of a series of alkali-cationized hybrid peptides, viz., Boc-alpha,beta- and -beta,alpha-carbopeptides, synthesized from C-linked carbo-beta3-amino acids [Caa (S)] and alpha-alanine (L-Ala), have been investigated by electrospray ionization tandem mass spectrometry. The positional isomers (six pairs) of the cationized alpha,beta- and beta,alpha-peptides can be differentiated by the collision-induced dissociation (CID) spectra of their [M + Cat-Boc + H]+ ions which give characteristic series of alkali-cationized C- (x(n)+, y(n)+, z(n)+) and N-terminal (a(n)+, b(n)+, c(n)+) ions. Another noteworthy difference is cationized beta,alpha-peptides eliminate a molecule of ammonia whereas this pathway is absent for alpha,beta-peptides. This is useful for identifying the presence of a beta-amino acid at the N-terminus. The CID spectra of [M + Cat-Boc + H]+ ions of these peptide acids show abundant rearrangement [b(n) + 17 + Cat]+ (n = 1 to n-1) ions which is diagnostic for distinguishing between alpha- and beta-amino acid at the C-terminus. MS(n) experiments of [b(n) + Li-H]+ ions from these hybrid peptides showed the loss of CO and 72 u giving rise to [a(n) + Li-H]+ and cationized nitrile product ions which render support to earlier proposals that b(n)+ or [b(n) + Cat-H]+ ions have protonated or cationized oxazolinone structures, respectively. 相似文献
970.
Reddy TJ Prabhakar S Ravi Kumar M Saradhi UV Vairamani M 《Journal of mass spectrometry : JMS》2006,41(1):59-70
The electron impact (EI) mass spectra of a series of N,N-dialkyl-aminoethyl-2-chlorides, N(R(1))(R(2))-CH(2)-CH(2)Cl and trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols, N(R(1))(R(2))-CH(2)-CH(2)-O-Si(CH(3))(3), where R(1) and R(2) = methyl, ethyl, propyl and isopropyl, which are precursors of VX type of compounds, are studied. All the compounds (1-20) show abundant molecular ions, in addition to a weak [M - H](+) ion, except the N,N-diisopropyl group containing compounds (8 and 18). A general EI fragmentation pattern for the above two series of compounds is discussed. The observed fragment ions are due to simple homolytic cleavages, and they are distinct to allow the identification of the compounds unequivocally including those of isomeric compounds. The primary fragmentation of compounds 1-20 is beta-cleavage, i.e. homolytic cleavage of C-C bond, which is linked to the nitrogen atom. Three types of beta-cleavages are possible for these compounds, in which the abundance of beta-cleavage product ions is found to depend on the size and structure of the alkyl group attached to nitrogen. The alpha-cleavage fragment ions are found only for N,N-dialkyl aminoethyl-2-chlorides but are absent in the corresponding trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols. The retention indices are calculated for all the studied compounds (1-20) and are in the ranges of 750.38-1079.24 for 1-10 and 905.23-1190.25 for 11-20. 相似文献