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61.
Dasilva-Carbalhal J García-Río L Gómez-Díaz D Mejuto JC Pérez-Lorenzo M 《Journal of colloid and interface science》2005,292(2):591-594
A study was carried out on the influence of different polyethylene glycol dimethyl ethers (glymes) on the conductance percolation of AOT/isooctane/water microemulsions. The glymes used were chosen on the basis of this chain length (the number of polymeric units). In all cases we observed a decrease in the percolation threshold on increasing the amount of a glyme added to the microemulsion. We observed a correlation between the effect exerted by the glyme and its chain length, which shows the importance of including them in the interface for the percolative phenomenon. Such inclusion modifies the properties of the AOT film, facilitating the exchange of matter between droplets. 相似文献
62.
Solid-phase spectrophotometric microdetermination of iron with ascorbic acid and ferrozine 总被引:1,自引:0,他引:1
M. L. Fernández-de Córdova A. Ruíz-Medina A. Molina-Díaz 《Analytical and bioanalytical chemistry》1997,357(1):44-49
A very sensitive and selective method for the determination of trace amounts of iron has been developed, based on the reduction
of Fe(III) to Fe(II) by ascorbic acid, followed by chromogenic chelation of Fe(II) with ferrozine. The complex Fe(II)-ferrozine
is easily sorbed on a dextran-type anion-exchange gel packed in a 1 mm cell, and the absorbance of the gel is measured directly
at 569 and 800 nm. The extended linear range of the determination is 0.5–10 ng ml-1 of iron (apparent molar absorptivity=4.4×107 l mol-1 cm-1) and the precision (RSD) 1.3% for a concentration of 5 ng ml-1 of iron (n=10). The detection limit for a sample volume of 1000 ml, using 0.040 g of anion-exchanger, corresponds to 0.12 ng ml-1. The method has been successfully applied to the determination of iron in natural and waste waters, wine, soil extract and
previously digested vegetal tissues, drugs and human hair.
Received: 20 November 1995/Revised: 23 January 1996/Accepted: 26 January 1996 相似文献
63.
The structure of the trimolecular liquid mixture of 2:6:1 cyclohexene, tert-butyl alcohol, and water has been investigated using hydrogen/deuterium substitution neutron scattering techniques, and a three-dimensional structural model refined to be consistent with the experimental data has been built using the technique of Empirical Potential Structure Refinement. The model shows a well-mixed solution of the three molecular components where the competing interactions between the nonpolar cyclohexene and polar water molecules are balanced in the solution leading to largely pure-alcohol-like interactions between the tert-butyl alcohol molecules. Cyclohexene molecules favor direct solvation by alcohol methyl groups while water molecules are accommodated, dispersed throughout the solution, via hydrogen bonding interactions with the alcohol molecule hydroxyl groups. Rare occurrences of direct cyclohexene-water interactions are of the classic hydrophobic hydration type and no evidence is found for microscopic heterogeneity in the trimolecular mixture in contrast to the general findings for binary alcohol-water solutions. 相似文献
64.
V. V. A. Fernandez N. Tepale J. C. Sánchez-Díaz E. Mendizábal J. E. Puig J. F. A. Soltero 《Colloid and polymer science》2006,284(4):387-395
The synthesis of nanostructured poly(N-isopropylacrylamide) (polyNIPA) hydrogels by a two-stage polymerization process is reported here. The process involves the
synthesis of slightly crosslinked polyNIPA nanoparticles by inverse (w/o) microemulsion polymerization; then, these particles
are dried, cleaned and dispersed in an aqueous solution of NIPA and a crosslinking agent (N,N-methylene-bis-acrylamide or NMBA) and polymerized to produce the nanostructured hydrogels. Their swelling and de-swelling
kinetics, volume phase transition temperatures (T
VPT) and mechanical properties at the equilibrium swollen state are investigated as a function of the weight ratio of polyNIPA
particles to monomer (NIPA). The nanostructured gels exhibit larger equilibrium water uptake, faster swelling and de-swelling
rates and similar T
VPT than those of the conventional ones; moreover, the elastic and Young moduli are larger than those of the conventional hydrogels
at similar swelling ratios. The fast swelling and de-swelling kinetics are explained in terms of the controlled inhomogeneities
introduced by the method of synthesis. 相似文献
65.
Meseguer B Alonso-Díaz D Griebenow N Herget T Waldmann H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(21):3943-3957
Protein kinaseC (PKC) is linked to the signal-induced modulation of a wide variety of cellular processes, such as growth, differentiation, secretion, apoptosis, and tumor development. The design and synthesis of small molecules that regulate these different cellular signaling systems is at the forefront of modern drug design. Herein we report a) an efficient method for the synthesis of indolactamV (6), a PKC activator, and its N13-des(methyl) analogues (19) using a regioselective organometallic transformation, a convenient aminomalonate derivative (10) to introduce the appropriate functionality and an enantiospecific enzymic hydrolysis as key steps; b) the use of this method in the first solid-phase synthesis of a teleocidin library modifying the N-13, C-12 and C-7 alkyl chains, and, therefore, producing a library of potential activators and/or inhibitors of PKC of the general structure (32); c) the activation of PKC by selected members of the library using a MARCKS translocation in vivo assay system; d) the observation that some of these analogues are nearly as effective as the natural PKC activators phorbol dibutyrate and (-)-indolactam V (6), and e) the observation that some of these analogues have different potential to induce down-regulation of members of the PKC gene family after chronic stimulation. 相似文献
66.
Pérez González M Gonzalez Díaz H Molina Ruiz R Cabrera MA Ramos de Armas R 《Journal of chemical information and computer sciences》2003,43(4):1192-1199
A new application of TOPological Sub-structural MOlecular DEsign (TOPS-MODE) was carried out in herbicides using computer-aided molecular design. Two series of compounds, one containing herbicide and the other containing nonherbicide compounds, were processed by a k-Means Cluster Analysis in order to design the training and prediction sets. A linear classification function to discriminate the herbicides from the nonherbicide compounds was developed. The model correctly and clearly classified 88% of active and 94% of inactive compounds in the training set. More specifically, the model showed a good global classification of 91%, i.e., (168 cases out of 185). While in the prediction set, they showed an overall predictability of 91% and 92% for active and inactive compounds, being the global percentage of good classification of 92%. To assess the range of model applicability, a virtual screening of structurally heterogeneous series of herbicidal compounds was carried out. Two hundred eighty-four out of 332 were correctly classified (86%). Furthermore this paper describes a fragment analysis in order to determine the contribution of several fragments toward herbicidal property; also the present of halogens in the selected fragments were analyzed. It seems that the present TOPS-MODE based QSAR is the first alternate general "in silico" technique to experimentation in herbicides discovery. 相似文献
67.
A normal coordinates analysis for the M(NH3)2+ 4 complex ions in Td symmetry (M = Zn, Cd, Co) and in D4h symmetry (M = Cu, Pd, Pt) has been undertaken on the basis of a General Valence Force Field (GVFF), using simplified molecular models. Throughout the course of the present work, we have relaxed the point mass approximation for the NH3-ligands in order to investigate, on a quantitative basis, some relevant ligand - framework coupling vibrations. The simplest molecular model able to accomplish this purpose is to treat the ammino group, in a linear ligator approximation. We show that these model calculations provide a satisfactory set of vibrational frequencies as well as consistent sets of force constants. 相似文献
68.
Severo Vázquez-Prieto Esperanza Paniagua Hugo Solana Florencio M. Ubeira Humberto González-Díaz 《Molecular diversity》2017,21(3):713-718
In the last years, the encryption of system structure information with different network topological indices has been a very active field of research. In the present study, we assembled for the first time a complex network using data obtained from the Immune Epitope Database for fungi species, and we then considered the general topology, the node degree distribution, and the local structure of this network. We also calculated eight node centrality measures for the observed network and compared it with three theoretical models. In view of the results obtained, we may expect that the present approach can become a valuable tool to explore the complexity of this database, as well as for the storage, manipulation, comparison, and retrieval of information contained therein. 相似文献
69.
Dr. Lina M. Aguirre-Díaz Marcelo Echeverri Dr. Katherine Paredes-Gil Dr. Natalia Snejko Dr. Berta Gómez-Lor Prof. Dr. Enrique Gutiérrez-Puebla Prof. Dr. M. Ángeles Monge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5298-5306
Three new cadmium-based coordination polymers, denoted [Cd(hfipbb)(4,4’-bipy)] ( CdPF-1 ), [Cd(hfipbb)(2,2’-bipy)] ( CdPF-2 ), and [Cd(hfipbb)(1,10-phen)] ( CdPF-3 ), have been hydrothermally synthesized by using the well-known V-shaped organic linker 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), together with different nitrogenated auxiliary linkers. Considering the d10 configuration of the transition metal selected, the luminescent properties for these CdPF-n materials were explored, finding that materials CdPF-2 and CdPF-3 act as excellent sensors in the detection of explosive nitro aromatic compounds. The photoluminescence properties of CdPF-2 and CdPF-3 revealed that significant and sensitive fluorescence quenching was observed toward NP (nitrophenol) for CdPF-2 and PA (picric acid) for CdPF-3 in MeOH suspensions. 相似文献
70.
The 19 F-1 H heterocorrelated NMR experiments enable the final assignments of structures of six difluorocyclopropane (mono, bis and tris gem) sesquiterpene lactones of helenalin and parthenin series. 相似文献