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951.
Heitor Fernando Nunes de Oliveira Christophe Farès Roberto Rinaldi 《Chemical science》2015,6(9):5215-5224
In this report, 1-butyl-3-methylimidazolium chloride ([C4C1im]Cl) is demonstrated to enhance the kinetics of acid-catalysed hydrolysis of 1,4-β-glucans in binary solvent mixtures. [C4C1im]Cl plays other roles in the reaction beyond acting as a solvent for cellulose, as currently accepted. In fact, the presence of the IL increases the Hammett acidity of the catalyst dissolved in the reaction medium. The kinetic data from cellobiose and cellulose hydrolysis directly correlate with the acid strength found for p-toluenesulfonic acid in the different reaction media studied here. The current report identifies neglected, but yet very important phenomena occurring in cellulose depolymerisation. 相似文献
952.
Rubí Zamudio-Vázquez Sa?ka Ivanova Miguel Moreno Maria Isabel Hernandez-Alvarez Ernest Giralt Axel Bidon-Chanal Antonio Zorzano Fernando Albericio Judit Tulla-Puche 《Chemical science》2015,6(8):4537-4549
The synthesis of a new small library of quinoxaline-containing peptides is described. After cytotoxic evaluation in four human cancer cell lines, as well as detailed biological studies, it was found that the most active compound, RZ2, promotes the formation of acidic compartments, where it accumulates, blocking the progression of autophagy. Further disruption of the mitochondrial membrane potential and an increase in mitochondrial ROS was observed, causing cells to undergo apoptosis. Given its cytotoxic activity and protease-resistant features, RZ2 could be a potential drug candidate for cancer treatment and provide a basis for future research into the crosstalk between autophagy and apoptosis and its relevance in cancer therapy. 相似文献
953.
Javier Galeano Miguel-ngel Gomez Fernando Rivas Javier M. Buldú 《Entropy (Basel, Switzerland)》2021,23(7)
The aim of the current study was twofold: (i) to investigate the distribution of the strike positions of badminton players while quantifying the corresponding standard entropy and using an alternative metric (spatial entropy) related to winning and losing points and random positions; and (ii) to evaluate the standard entropy of the receiving positions. With the datasets of 259 badminton matches, we focused on the positions of players’ strokes and the outcome of each point. First, we identified those regions of the court from which hits were most likely to be struck. Second, we computed the standard entropy of stroke positions, and then the spatial entropy, which also considers the order and clustering of the hitting locations in a two-dimensional Euclidean space. Both entropy quantifiers revealed high uncertainty in the striking position; however, specific court locations (i.e., the four corners) are preferred over the rest. When the outcome of each point was taken into account, we observed that the hitting patterns with lower entropy were associated with higher probabilities of winning points. On the contrary, players striking from more random positions were more prone to losing the points. 相似文献
954.
955.
The growing interest on first- and second-generation biofuels requires the development of thermodynamic tools with predictive capacity for mixtures containing a wide variety of organo-oxygenated compounds, water and hydrocarbons. Modeling this type of mixtures is challenging due to the presence of association and solvation effects. In this work, we present a revision of the group contribution with association equation of state (GCA-EoS) parameters, with the purpose of extending and improving the predictive capacity of the model for systems containing water, alcohols and hydrocarbons. 相似文献
956.
Fernando Silva Lopes Osmar Antunes Junior Ivano G.R. Gutz 《Electrochemistry communications》2010,12(10):1387-1390
Successful coupling of electrochemical preconcentration (EPC) to capillary electrophoresis (CE) with contactless conductivity detection (C4D) is reported for the first time. The EPC–CE interface comprises a dual glassy carbon electrode (GCE) block, a spacer and an upper block with flow inlet and outlet, pseudo-reference electrode and a fitting for the CE silica column, consisting of an orifice perpendicular to the surface of a glassy carbon electrode with a bushing inside to ensure a tight press fit. The end of the capillary in contact with the GCE is slant polished, thus defining a reproducible distance from the electrode surface to the column bore. First results with EPC–CE–C4D are very promising, as revealed by enrichment factors of two orders of magnitude for Tl, Cu, Pb and Cd ion peak area signals. Detection limits for 10 min deposition time fall around 20 nmol L?1 with linear calibration curves over a wide range. Besides preconcentration, easy matrix exchange between accumulation and stripping/injection favors procedures like sample cleanup and optimization of pH, ionic strength and complexing power. This was demonstrated for highly saline samples by using a low conductivity buffer for stripping/injection to improve separation and promote field-enhanced sample stacking during electromigration along the capillary. 相似文献
957.
958.
Fernando Moyano Dr. Patricia G. Molina Dr. Juana J. Silber Prof. Leonides Sereno Prof. N. Mariano Correa Prof. 《Chemphyschem》2010,11(1):236-244
Herein, we investigate the behavior of the electroactive molecular probe 6‐propionyl‐2‐dimethyl amino naphthalene (PRODAN) in large unilamellar vesicles (LUV) formed with the phospholipid 1,2‐di‐oleoyl‐sn‐glycero‐3‐phosphatidylcholine (DOPC) by using cyclic voltammetry (CV). The CV studies in pure water confirm our previous spectroscopic results that PRODAN self‐aggregates due to its low water solubility. Moreover, the electrochemical results also reveal that the PRODAN aggregated species are non‐electroactive within the studied electrochemical potential region. In DOPC LUV media, the redox behavior of PRODAN shows how the LUV bilayer interacts with PRODAN aggregated species to form PRODAN monomer species. Moreover, the electrochemical response of PRODAN allows us to propose a model for explaining the electrochemical experimental results and—in conjunction with our measurements—for calculating the value of the partition constant (Kp) of PRODAN between the water and LUV bilayer pseudophases. This value coincides with that obtained through an independent technique. Moreover, our electrochemical model allows us to calculate the diffusion coefficient (D) for the DOPC LUV, which coincides with the D value obtained through dynamic light scattering (DLS). Thus, our data clearly show that electrochemical measurements could be a powerful alternative approach to investigate the behavior of nonionic electroactive molecules embed in a confined environment such as the LUV bilayer. Moreover, we believe that this approach can be used to investigate the behavior of non‐optical molecular drugs embedded in bilayer media. 相似文献
959.
Estela Giménez Fernando Benavente José Barbosa Victoria Sanz-Nebot 《Analytical and bioanalytical chemistry》2010,398(1):357-365
2,5-Dihydroxybenzoic acid (DHB) has been demonstrated to be a more suitable matrix than 3,5-dimethoxy-4-hydroxycinnamic acid
(sinapinic acid, SA) to obtain reliable molecular mass values of intact glycoproteins because it prevents sugar fragmentation.
Lack of spot homogeneity during the crystallization step was prevented by drying the sample-matrix mixture under vacuum conditions.
Nevertheless, this sample-matrix preparation procedure requires a specific experimental setup and may be time-consuming. In
this work, we investigated the effectiveness of different ionic liquid matrices (ILMs) with SA and DHB on the ionization of
a set of intact glycoproteins with several degrees of glycosylation. The obtained results demonstrate that some of the tested
ILMs allow detection of the studied intact glycoproteins. Furthermore, the selected optimum conditions solve the reproducibility
issue of using the DHB as a solid matrix without the vacuum drying method and, surprisingly, avoid sugar fragmentation when
both SA and DHB were used as ILMs. 相似文献
960.
Ghiulendan Aptisa Fernando Benavente Victoria Sanz-Nebot Elisabeta Chirila José Barbosa 《Analytical and bioanalytical chemistry》2010,396(4):1571-1579
Modelling electrophoretic mobility as a function of pH can be simultaneously used for determination of ionization constants
and for rapid selection of the optimum pH for separation of mixtures of the modelled compounds. In this work, equations describing
the effect of pH on electrophoretic behaviour were used to investigate migration of a series of polyprotic amphoteric peptide
hormones between pH 2 and 12 in polybrene-coated capillaries. Polybrene (hexadimethrin bromide) is a polymer composed of quaternary
amines that is strongly adsorbed by the fused-silica inner surface, preventing undesired interactions between the peptides
and the inner capillary wall. In polybrene-coated capillaries the separation voltage must be reversed, because of the anodic
electroosmotic flow promoted by the polycationic polymer attached to the inner capillary wall. The possibility of using polybrene-coated
capillaries for determination of accurate ionization constants has been evaluated and the optimum pH for separation of a mixture
of the peptide hormones studied has been selected. Advantages and disadvantages of using bare fused-silica and polybrene-coated
capillaries for these purposes are discussed. 相似文献