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121.
By two independent methods, the solubilized receptor for phosvitin (PV) has a subunit MW of 116K. Affinity chromatography, showed that only 2 of the more than 25 proteins present in the total detergent solubilized oocyte membrane extract were retained on a PV-agarose column. These proteins of MW of 116K and 100K could be eluted from PV-agarose with free PV. By gel exclusion chromatography, the receptor-125I-PV complexes elute in the void volume of a Biogel A-1.5 column. When these void fractions were assayed gy SDS-PAGE only a single protein of MW of 116K was observed in addition to 125I-PV. 相似文献
122.
Woods KK Maehigashi T Howerton SB Sines CC Tannenbaum S Williams LD 《Journal of the American Chemical Society》2004,126(47):15330-15331
The crystal structure of [d(CGCAAATTTGCG)]2 has been determined to 1.5 A resolution, representing the first high-resolution structure of this DNA fragment. The ion interactions are novel. A spermine molecule replaces a Mg2+ observed in analogous structures. Unlike lower-resolution structures, the minor groove is narrow and the major groove lacks extra Watson-Crick hydrogen bonds. In addition, a monolayer of solvent sites, including a "spine of hydration", is visible in the minor groove. The crystal of [d(CGCAAATTTGCG)]2 was grown from a solution containing spermine, magnesium, and lithium. The conformation recapitulates that of "monovalent-minus" DNA. 相似文献
123.
Expressing the residual resistivity ?0 as a force-force correlation, a first-principles basis is afforded for the low temperature expansion of the electrical resistivity ? as
(I)
where λ = const T-2 is the non-resistive mean free path arising from electron-electron scattering. λ1 is found to reflect directly long-range correlations in the electronic motions via the off-diagonal behaviour of the local density of states at the Fermi energy. 相似文献
124.
Woods M Botta M Avedano S Wang J Sherry AD 《Dalton transactions (Cambridge, England : 2003)》2005,(24):3829-3837
The gadolinium(iii) complex of S-SSSS-NO(2)BnDOTMA exhibits water exchange kinetics that are optimal for use in high relaxivity or targeted contrast agents. However, the synthesis of this ligand is hampered by the steric encumbrance imparted upon the cyclen ring by the nitrobenzyl substituent. A relatively simple modification has been used to enable the synthesis of larger quantities of a bifunctional ligand that retains similar fast water exchange properties. The gadolinium complex of S-SSS-NO(2)BnDO3MA-1A is shown to retain the rapid water exchange kinetics characteristic of a twisted square antiprismatic (TSAP) coordination geometry (tau(M)= 6 +/- 0.4 ns). 相似文献
125.
The synthesis of a novel benzazepine, 4,5,6,7,7a,8-hexahydro-7-methylphenanthro[10,1-bc]-azepine, is described. Two pathways leading from 1,2,4,5-tetrahydro-1-(o-nitrophenyl)-3H-2-benzazepin-3-one were investigated. The most successful route, utilizing a Pschorr cyclization followed by diborane reduction and Eschweiler-Clarke methylation, led to an excellent yield of the title compound. 相似文献
126.
Brewster AG Broady S Davies CE Heightman TD Hermitage SA Hughes M Moloney MG Woods G 《Organic & biomolecular chemistry》2004,2(7):1031-1043
The synthesis and alkylation of [4.3.0]-bicyclic lactams, derived from 6-oxopipecolic acid, have been investigated. Alkylation can proceed with predominantly exo-diastereoselectivity, but the efficiency of this process depends on the substitution at the hemiaminal ether system. These products can be readily deprotected to give substituted hydroxymethyl lactams in good yield. 相似文献
127.
Gibbons LK Barker AR Briere RA Makoff G Papadimitriou V Patterson JR Schwingenheuer B Somalwar SV Wah YW Winstein B Winston R Woods M Yamamoto H Swallow EC Bock GJ Coleman R Enagonio J Hsiung YB Ramberg E Stanfield K Tschirhart R Yamanaka T Gollin GD Karlsson M Okamitsu JK Debu P Peyaud B Turlay R Vallage B 《Physical review letters》1993,70(9):1199-1202
128.
Ramberg E Bock GJ Coleman R Enagonio J Hsiung YB Stanfield K Tschirhart R Yamanaka T Barker AR Briere RA Gibbons LK Makoff G Papadimitriou V Patterson JR Somalwar S Wah YW Winstein B Winston R Woods M Yamamoto H Swallow EC Blair G Gollin GD Karlsson M Okamitsu JK Debu P Peyaud B Turlay R Vallage B 《Physical review letters》1993,70(17):2525-2528
129.
The Amber biomolecular simulation programs 总被引:32,自引:0,他引:32
Case DA Cheatham TE Darden T Gohlke H Luo R Merz KM Onufriev A Simmerling C Wang B Woods RJ 《Journal of computational chemistry》2005,26(16):1668-1688
We describe the development, current features, and some directions for future development of the Amber package of computer programs. This package evolved from a program that was constructed in the late 1970s to do Assisted Model Building with Energy Refinement, and now contains a group of programs embodying a number of powerful tools of modern computational chemistry, focused on molecular dynamics and free energy calculations of proteins, nucleic acids, and carbohydrates. 相似文献
130.
Woods M Carlsson S Hong Q Patole SN Lie LH Houlton A Horrocks BR 《The journal of physical chemistry. B》2005,109(50):24035-24045
We have analyzed a kinetic model for the formation of organic monolayers based on a previously suggested free radical chain mechanism for the reaction of unsaturated molecules with hydrogen-terminated silicon surfaces (Linford, M. R.; Fenter, P. M.; Chidsey, C. E. D. J. Am. Chem. Soc 1995, 117, 3145). A direct consequence of this mechanism is the nonexponential growth of the monolayer, and this has been observed spectroscopically. In the model, the initiation of silyl radicals on the surface is pseudo first order with rate constant, ki, and the rate of propagation is determined by the concentration of radicals and unreacted Si-H nearest neighbor sites with a rate constant, kp. This propagation step determines the rate at which the monolayer forms by addition of alkene molecules to form a track of molecules that constitute a self-avoiding random walk on the surface. The initiation step describes how frequently new random walks commence. A termination step by which the radicals are destroyed is also included. The solution of the kinetic equations yields the fraction of alkylated surface sites and the mean length of the random walks as a function of time. In mean-field approximation we show that (1) the average length of the random walk is proportional to (kp/ki)1/2, (2) the monolayer surface coverage grows exponentially only after an induction period, (3) the effective first-order rate constant describing the growth of the monolayer and the induction period (kt) is k = (2ki kp)1/2, (4) at long times the effective first-order rate constant drops to ki, and (5) the overall activation energy for the growth kinetics is the mean of the activation energies for the initiation and propagation steps. Monte Carlo simulations of the mechanism produce qualitatively similar kinetic plots, but the mean random walk length (and effective rate constant) is overestimated by the mean field approximation and when kp > ki, we find k approximately ki0.7kp0.3 and Ea = (0.7Ei+ 0.3Ep). However the most striking prediction of the Monte Carlo simulations is that at long times, t > 1/k, the effective first-order rate constant decreases to ki even in the absence of a chemical termination step. Experimental kinetic data for the reaction of undec-1-ene with hydrogen-terminated porous silicon under thermal reflux in toluene and ethylbenzene gave a value of k = 0.06 min(-1) and an activation energy of 107 kJ mol(-1). The activation energy is in reasonable agreement with density functional calculations of the transition state energies for the initiation and propagation steps. 相似文献