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排序方式: 共有471条查询结果,搜索用时 112 毫秒
101.
102.
M. Maczka W. Paraguassu P.T.C. Freire F.E.A. Melo 《Journal of solid state chemistry》2004,177(6):2002-2006
A high-pressure Raman scattering study of the tungstate Al2(WO4)3 is presented. This study showed the onset of two reversible phase transitions at 0.28±0.07 and 2.8±0.1 GPa. The pressure evolution of Raman bands provides strong evidences that both the transitions involve rotations/tilts of nearly rigid tungstate tetrahedra and that the structure of the stable phase in the 0.28-2.8 GPa range may be the same as the structure of the ambient pressure, low-temperature monoclinic (C2h5) ferroelastic phase of Al2(WO4)3. 相似文献
103.
Luciana A. I. de Azeredo Leda R. Castilho Selma G. F. Leite Rosalie R. R. Coelho Denise M. G. Freire 《Applied biochemistry and biotechnology》2003,108(1-3):749-755
Streptomyces are important microorganisms because of their capacity to produce numerous bioactive molecules. In the present work protease
production, by Streptomyces sp. 594 isolated from a Brazilian Cerrado soil, was maximized by optimizing a low-cost culture medium composition (casitone
and sugarcane molasses) using statistical experimental design. The final protease activity (56 U/mL) was 2.8-fold and 58-fold
higher than that obtained in the beginning of this study, and in a previous work, using an actinomycete selection medium,
respectively. Protease production, not growth associated, appeared to be modulated by an inducer system, whereby the C/N ratio
seemed to play a significant role. 相似文献
104.
Joo C. F. Nunes Raquel O. Cristvo Mara G. Freire Valria C. Santos-Ebinuma Joaquim L. Faria Cludia G. Silva Ana P. M. Tavares 《Molecules (Basel, Switzerland)》2020,25(24)
l-asparaginase (ASNase, EC 3.5.1.1) is an aminohydrolase enzyme with important uses in the therapeutic/pharmaceutical and food industries. Its main applications are as an anticancer drug, mostly for acute lymphoblastic leukaemia (ALL) treatment, and in acrylamide reduction when starch-rich foods are cooked at temperatures above 100 °C. Its use as a biosensor for asparagine in both industries has also been reported. However, there are certain challenges associated with ASNase applications. Depending on the ASNase source, the major challenges of its pharmaceutical application are the hypersensitivity reactions that it causes in ALL patients and its short half-life and fast plasma clearance in the blood system by native proteases. In addition, ASNase is generally unstable and it is a thermolabile enzyme, which also hinders its application in the food sector. These drawbacks have been overcome by the ASNase confinement in different (nano)materials through distinct techniques, such as physical adsorption, covalent attachment and entrapment. Overall, this review describes the most recent strategies reported for ASNase confinement in numerous (nano)materials, highlighting its improved properties, especially specificity, half-life enhancement and thermal and operational stability improvement, allowing its reuse, increased proteolysis resistance and immunogenicity elimination. The most recent applications of confined ASNase in nanomaterials are reviewed for the first time, simultaneously providing prospects in the described fields of application. 相似文献
105.
Valber A. Pedrosa Josiane Caetano Sergio A. S. Machado Renato S. Freire Mauro Bertotti 《Electroanalysis》2007,19(13):1415-1420
Studies on the immobilization of acetylcholinesterase onto a SAM gold electrode and the use of the fabricated biosensor for the determination of carbaryl and parathion are presented. The influence of pH, ionic strength, enzyme loading and concentration of glutaraldehyde on the response of the biosensor was investigated . The amperometric biosensor developed in this study provided linearity to parathion and carbaryl in the 2.0 a 30.0×10?6 mol L?1 concentration range. The detection limits under the optimum working conditions were found to be 9.3 μg L?1 for parathion and 9.0 μg L?1 for carbaryl. The enzyme electrode was found to be stable for 7 days. 相似文献
106.
F. L. Freire Jr E. C. Montenegro 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1987,7(3):239-241
A new method to perform the calculation the limits of the electron capture cross-section in the Strong Potential Born Approximation is presented. Within this approach, the high velocity limit is obtained by a simple algebraic procedure as an alternative derivation to the complex variable analysis used previously. 相似文献
107.
Freire J. L. F. Perrut V. A. Braga A. M. B. Vieira R. D. Ribeiro A. S. Rosas M. A. P. 《Experimental Techniques》2015,39(5):70-79
Experimental Techniques - Laboratory tests were conducted to understand and describe how the reinforcement layers of a carbon fiber epoxy composite material can enable a steel line pipe specimen... 相似文献
108.
Eleonora Freire Griselda Polla Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(2):186-190
The asymmetric unit of the title salt [systematic name: bis(4‐(2,3‐dichlorophenyl)‐1‐{4‐[(2‐oxo‐1,2,3,4‐tetrahydroquinolin‐7‐yl)oxy]butyl}piperazin‐1‐ium) oxalate–oxalic acid (1/1)], 2C23H28Cl2N3O2+·C2O42−·C2H2O4, consists of one protonated aripiprazole unit (HArip+), half an oxalate dianion and half an oxalic acid molecule, the latter two lying on inversion centres. The conformation of the HArip+ cation differs from that in other reported salts and resembles more the conformation of neutral Arip units in reported polymorphs and solvates. The intermolecular interaction linking HArip+ cations is also similar to those in reported Arip compounds crystallizing in the space group P, with head‐to‐head N—H...O hydrogen bonds generating centrosymmetric dimers, which are further organized into planar ribbons parallel to (01). The oxalate anions and oxalic acid molecules form hydrogen‐bonded chains running along [010], which `pierce' the planar ribbons, interacting with them through a number of stronger N—H...O and weaker C—H...O hydrogen bonds, forming a three‐dimensional network. 相似文献
109.
Mônica F. Belian Ricardo O. Freire Gilberto F. de Sá Severino Alves Jr. 《Journal of luminescence》2010,130(10):1946-1442
A new Eu(III)/Tb(III) binuclear coordination compound with red and yellow emissions in solution and solid state, respectively, has been prepared. The lanthanide (Ln) ions are coordinated to crown ethers (C) and bridged by a dipyridyl (dipy) ligand. Ln/C and Ln/C/dipy complexes were also synthesized as precursors for the bimetallic compounds. The homo- and heterobimetallic Ln(III) complexes were characterized by elemental analysis as well as infra-red, absorption (UV-visible) and emission spectroscopies. The heterobimetallic complex geometry was predicted using the Sparkle/AM1 model and suggested to a chemical environment of very low symmetry around the lanthanide ions (C1), in agreement with the luminescence spectrum. The Eu(III) and Tb(III) complexes display intense red and green emissions, respectively, in the solid state at room temperature. 相似文献
110.
Lafayette N. J. de Windt Dr. Zulema Fernández Dr. Manuel Fernández-Míguez Prof. Dr. Félix Freire Prof. Dr. Anja R. A. Palmans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(1):e202103691
An in-depth study of the supramolecular copolymerization behavior of N- and C-centered benzene-1,3,5-tricarboxamides (N- and C-BTAs) has been conducted in methylcyclohexane and in the solid state. The connectivity of the amide groups in the BTAs differs, and mixing N- and C-BTAs results in supramolecular copolymers with a blocky microstructure in solution. The blocky microstructure results from the formation of weaker and less organized, antiparallel hydrogen bonds between N- and C-BTAs. In methylcyclohexane, the helical threefold hydrogen-bonding network present in C- and N-BTAs is retained in the mixtures. In the solid state, in contrast, the hydrogen bonds of pure BTAs as well as their mixtures organize in a sheet-like pattern, and in the mixtures long-range order is lost. Drop-casting to kinetically trap the solution microstructures shows that C-BTAs retain the helical hydrogen bonds, but N-BTAs immediately adopt the sheet-like pattern, a direct consequence of the lower stabilization energy of the helical hydrogen bonds. In the copolymers, the stability of the helical aggregates depends on the copolymer composition, and helical aggregates are only preserved when a high amount of C-BTAs is present. The method outlined here is generally applicable to elucidate the copolymerization behavior of supramolecular monomers both in solution as well as in the solid state. 相似文献