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731.
A continuously-fed crystallization chamber that allows for kinetic path control through the crystallization phase diagram (from labile/nucleation to metastable/growth) was fabricated and used to crystallize lysozyme. A lumped kinetic model was developed, and parameters for heterogeneous nucleation kinetics were determined. Heterogeneous nucleation was found to have faster nucleation kinetics and slower growth kinetics than homogeneous nucleation, as expected. The major contributions of the new device are (1) to allow better control of the chemical environment for studies of crystal nucleation and growth, and (2) to allow lumped-model analysis of those studies to extract kinetic parameters. 相似文献
732.
We consider an S=1 Heisenberg chain with strong exchange (Delta=J(z)/J(perpendicular)) and single-ion uniaxial anisotropy (D) in a magnetic field (B) along the symmetry axis. The low-energy spectrum is described by an effective S=1/2 XXZ model that acts on two different low-energy sectors for a finite range of fields. The vacuum of each sector exhibits Ising-like antiferromagnetic ordering coexisting with the finite spin stiffness obtained from the exact solution of the XXZ model. In this way, we demonstrate the existence of a spin supersolid phase. We also compute the full Delta-B quantum phase diagram using a quantum Monte Carlo method. 相似文献
733.
Dasgupta A Das PK Dias RS Miguel MG Lindman B Jadhav VM Gnanamani M Maiti S 《The journal of physical chemistry. B》2007,111(29):8502-8508
The interaction behavior of DNA with different types of hydroxylated cationic surfactants has been studied. Attention was directed to how the introduction of hydroxyl substituents at the headgroup of the cationic surfactants affects the compaction of DNA. The DNA-cationic surfactant interaction was investigated at different charge ratios by several methods like UV melting, ethidium bromide exclusion, and gel electrophoresis. Studies show that there is a discrete transition in the DNA chain from extended coils (free chain) to a compact form and that this transition does not depend substantially on the architecture of the headgroup. However, the accessibility of DNA to ethidium bromide is preserved to a significantly larger extent for the more hydrophilic surfactants. This was discussed in terms of surfactant packing. Observations are interpreted to reflect that the surfactants with more substituents have a larger headgroup and therefore form smaller micellar aggregates; these higher curvature aggregates lead to a less efficient, "patch-like" coverage of DNA. The more hydrophilic surfactants also presented a significantly lower cytotoxicity, which is important for biotechnological applications. 相似文献
734.
Sanchita Sengupta Daniel Ebeling Sameer Patwardhan Xin Zhang Hans vonBerlepsch Christoph Bttcher Vladimir Stepanenko Shinobu Uemura Carsten Hentschel Harald Fuchs Ferdinand C. Grozema Laurens D. A. Siebbeles Alfred R. Holzwarth Lifeng Chi Frank Würthner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(26):6484-6488
735.
It is gradually more significant to optimally select base stations in the design of cellular networks, as the customers stipulate cheaper and better wireless services. From a set of prospective site locations, a subset needs to be preferred which optimizes two critical objectives: service coverage and financial cost. Discovering the optimum base station locations for a cellular radio network is considered as a mathematical optimization problem. In the context of mobile communication, an efficient algorithm for the base-station placement problem is developed in this paper. The intention is to place a given number of base-stations in a given convex region and to assign range to each of them such that every point in the region is covered by at least one base-station and the maximum range assigned is curtailed. It is basically covering a region by a given number of equal radius circles where the objective is to minimize the radius. A computational method for finding good coverings of a square with equal circles is presented. An algorithm is designed that determines the optimal locations of base stations without performing an exhaustive search. The proposal will try to minimize the number of installed towers, makes tower’s location feasible, and provides full area coverage with an intention to reduce the overlapping. 相似文献
736.
737.
The laser photolysis‐laser‐induced fluorescence method was used for measuring the kinetic parameters of the reaction of OH radicals with CF3CH2OCH2CF3 (2,2,2‐trifluoroethyl ether), in the temperature range of 298–365 K. The bimolecular rate coefficient at 298 K, kII(298), was measured to be (1.47 ± 0.03) × 10?13 cm3 molecule?1 s?1, and the temperature dependence of kII was determined to be (4.5 ± 0.8) × 10?12exp [?(1030 ± 60)/T] cm3 molecule?1 s?1. The error quoted is 1σ of the linear regression of the respective plots. The rate coefficient at room temperature is very close to the average of the three previous measurements, whereas the values of Ea/R and the A‐factor are higher than the two previously reported values. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 519–525, 2010 相似文献
738.
739.
Dhananjay Soren Mohanlal Jana Subhabrata Sengupta Anil K. Ghosh 《Applied biochemistry and biotechnology》2010,162(2):373-389
A low molecular weight endo-xylanase (EC 3.2.1.8) was purified from an edible mushroom Termitomyces clypeatus grown in submerged medium with oat spelt xylan. Xylanase was purified to apparent homogeneity by ammonium sulfate fractionation
and gel filtration chromatography. Its molecular weight was determined by gel filtration chromatography and sodium dodecyl
sulfate-polyacrylamide gel electrophoresis to be 12 kDa. The enzyme was found to be most active at 50°C and pH 5.0, being
most stable at pH 6.5. The Km for oat spelt xylan was determined to be 10.4 mg/ml. The specificities of the enzyme was observed to be highly specific towards
oat spelt xylan and was inhibited by mercuric chloride (HgCl2), N-bromosuccinimide, and trans-1,2-diaminocyclohexane-N′,N′,N′,N′-tetraacetic acid strongly. The inhibitory action of N-bromosuccinimide on enzyme confirmed the presence of one tryptophan
residue in its substrate-binding site. Amino acid analysis for xylanase showed the presence of high amount of hydrophobic
serine, glycine, threonine, and alanine residues. The N-terminal sequencing study for the previously purified and characterized
56 kDa xylanolytic amyloglucosidase reveal the presence of 33.30% identity with glucoamylase chain A from Aspergillus awamori. The N-terminal sequence analysis of the present 12 kDa enzyme showed highest similarity (72.22% identity) towards xylanase
from Neurospora crassa. 相似文献
740.
Rupam Dinda Paresh Kumar Majhi Parbati Sengupta Sagarika Pasayat Saktiprosad Ghosh Larry R. Falvello Thomas C.W. Mak 《Polyhedron》2010
The syntheses and characterization of alkali metal complexes [{VO2L}M(H2O}n] (1 and 2) [M = Na+ (1), K+ (2)] of anionic cis-dioxovanadium(V) species (LVO2−) of the Schiff base 2-hydroxybenzoylhydrazone of 2-hydroxybenzaldehyde have been reported. The number of coordinated water molecules in [{VO2L}M(H2O}n] decreases as the charge density of the alkali metal ion decreases (n = 5 for Na+ and 1 for K+). These compounds represented M+-mediated supramolecular assembly [{VO2L}M(H2O}n]∝ with an infinite polymeric structure containing an alternating array of cis-dioxo vanadium(V), [VO2L]−, units and aquated metal ion centres, as confirmed by X-ray crystallographic investigation of both. All the compounds are characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. 相似文献