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41.
This study was conducted in a continuous three-stage system of anaerobic (R1)-anoxic(R2)-aerobic (R3) reactors with synthetic
wastewater containing phenol (1000 mg/L), chemical oxygen demand (COD) (3000 mg/L), CN− (30 mg/L), SCN−(400 mg/L), and NH
4
+
-N (600 mg/L) as principal pollutants and well-acclimated heterogeneous microbial cultures. The final effluent was partially
returned to R2 with a recycle ratio of 1. Anaerobic stage served to detoxify the feed by removing up to 80% of cyanide. Complete
SCN− removal and denitrification could be achieved in the anoxic stage by utilizing phenol as an internal source of carbon. Nitrification
efficiency of 93% was obtained in the aerobic reactor. The results demonstrated that the three-stage system can give the desired
final treated effluent quality (0 mg/L of phenol, 0.2 mg/L of CN−, 210 mg/L of COD, and 20 mg/L of NH
4
+
-N) and that the NO
3
−
-N concentration can be lowered by a higher recycle ratio. 相似文献
42.
Grindstone Chemistry--a greatly evolved version of Toda’s method of grinding solids together for solvent-free chemical reactions--has been described and its usefulness illustrated by the successful application of this technique to a simplified process for conducting the multi-component Biginelli reaction for the synthesis of physiologically active tetrahydropyrimidinones. 相似文献
43.
Wu A Mukhopadhyay P Chakraborty A Fettinger JC Isaacs L 《Journal of the American Chemical Society》2004,126(32):10035-10043
We report the synthesis and characterization of eight C-shaped methylene-bridged glycoluril dimers (1-8) bearing hydrogen-bonding amide groups on their aromatic rings. Compounds 1-6 undergo tight dimerization in CDCl3 solution (Ks > 9 x 10(5) M(-1)); binary mixtures of 1-7 form mixtures of homodimers and heterodimers in moderately selective dimerization processes (0.23 < or = Keq < or = 768; 0.253 < or = chiAB < 0.933). The high affinity formation of 1.1-6.6 is due to the commensurate nature of the geometrical constraints imposed by the pi-pi interactions and only two hydrogen bonds. The differential response of the strengths of the pi-pi interactions and H-bonds of 2.2 to changes in solvent polarity--from C6D6 to D2O--results in the formation of a solvent-independent isostructural aggregate that exhibits high affinity dimerization across the full range of solvents. 相似文献
44.
Synthesis of Some Novel Bisisoxazolidine Derivatives from Glyoxal‐derived Bisnitrones via Simultaneous Double Cycloaddition Reactions in Water 下载免费PDF全文
Simultaneous double 1,3‐dipolar cycloaddition reactions of glyoxal‐derived bisnitrones have been described in water. Significant rate acceleration and improved yields of exclusively diastereoselective and regioselective bisisoxazolidines in water have been observed at room temperature in a short reaction time compared with conventional solvents. 相似文献
45.
The micellization behavior of an anionic gemini surfactant, GA with nonionic surfactants C12E8 and C12E5 in presence of 0.1 M NaCl at 298 K temperature, has been studied tensiometrically in pure and mixed states, and the related
physicochemical parameters (cmc, γ
cmc, pC
20, Γ
max, and A
min) have been evaluated. Tensiometric profile (γ vs log [surfactant]), for conventional surfactants, generally consists of a single point of intersection; a gradually decreasing
line (normally linear, or with slight curvature) ultimately saturates in γ at a particular [surfactant], corresponding to complete monolayer saturation. The gemini, in this report, led to two unequivocal
breaks in the tensiometric isotherm. An attempt to the interpretation of the two breaks from molecular point of view is provided,
depending solely on the chemical structure of the surfactant. The gemini, even in mixed state with the conventional nonionic
surfactants C12E5 and C12E8, manifested the dual breaks; of course, the dominance of the feature decreases with increasing mole fraction of the nonionics
in the mixture. Theories of Clint, Rosen, Rubingh, Motomura, Georgiev, Maeda, and Nagarajan have been used to determine the
interaction between surfactants at the interface and micellar state of aggregation, the composition of the aggregates, the
theoretical cmc in pure and mixed states, and the structural parameters according to Tanford and Israelachvili. Several thermodynamic
parameters have also been predicted from those theories. 相似文献
46.
Brajagopal Samanta Joy Chakraborty C. R. Choudhury S. K. Dey D. K. Dey S. R. Batten P. Jensen Glenn P. A. Yap Samiran Mitra 《Structural chemistry》2007,18(1):33-41
We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing
N3 or N4 donor set along with terminal NNN− or SCN− ligands: [L1Cu(NCS)]ClO4 (1), [L2Cu(NCS)2] (2) and [L3Cu(NNN)]ClO4 (3) [L1 = NC5H4C(CH3)=N(CH2)3N=C(CH3)C5H4N, L2= Me2N–(CH2)3–N=C(CH3)C5H4N and L3 = NC5H4CH=N–(CH2)4–N=CHC5H4N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial
activities of the Schiff base ligands and their metal complexes have been studied using the disc diffusion method on the strains
of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that
show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate
or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P21/c) and 2 in triclinic (P-1) space group, respectively. 相似文献
47.
Chakraborty R Das AK Cervera ML De La Guardia M 《Analytical and bioanalytical chemistry》1996,355(1):43-47
The determination of cadmium in different sample types has been carried out by electrothermal atomization atomic absorption spectrometry with D(2)-background correction using a unpyrocoated graphite tube, after pressurized microwave-assisted digestion. Five chemical modifiers [(NH(4))(2)HPO(4), Pd(NO)(3))(2), Ni(NO(3))(2), thiourea and Triton X-100] have been assayed and nickel nitrate has been found to be most effective for an accurate determination of cadmium in mussel tissue, pig kidney and sewage sludge. The characteristic mass of the method is of the order of 1 pg and the limit of detection is lower than 0.1 ng/ml. 相似文献
48.
Dr. Uttam Chakraborty Patrick Bügel Lorena Fritsch Dr. Florian Weigend Prof. Dr. Matthias Bauer Prof. Dr. Axel Jacobi von Wangelin 《ChemistryOpen》2021,10(2):265-271
The controlled assembly of well-defined planar nanoclusters from molecular precursors is synthetically challenging and often plagued by the predominant formation of 3D-structures and nanoparticles. Herein, we report planar iron hydride nanoclusters from reactions of main group element hydrides with iron(II) bis(hexamethyldisilazide). The structures and properties of isolated Fe4, Fe6, and Fe7 nanoplatelets and calculated intermediates enable an unprecedented insight into the underlying building principle and growth mechanism of iron clusters, metal monolayers, and nanoparticles. 相似文献
49.
The vibrational spectroscopy of lithium dichloride anions microhydrated with one to three water molecules, [LiCl2(H2O)1–3]−, is studied in the OH stretching region (3800–2800 cm−1) using isomer-specific IR/IR double-resonance population labelling experiments. The spectroscopic fingerprints of individual isomers can only be unambiguously assigned after anharmonic effects are considered, but then yield molecular level insight into the onset of salt dissolution in these gas phase model systems. Based on the extent of the observed frequency shifts ΔνOH of the hydrogen-bonded OH stretching oscillators solvent-shared ion pair motifs (<3200 cm−1) can be distinguished from intact-core structures (>3200 cm−1). The characteristic fingerprint of a water molecule trapped directly in-between two ions of opposite charge provides an alternative route to evaluate the extent of ion pairing in aqueous electrolyte solutions. 相似文献
50.