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971.
On the basis of the isoelectric point of an enzyme and the doping principle of conducting polymers, choline oxidase was doped
in a polyaniline film to form a biosensor. The amperometric detection of choline is based on the oxidation of the H2O2 enzymatically produced on the choline biosensor. The response current of the biosensor as a function of temperature was determined
from 3 to 40°C. An apparent activation energy of 22.8 kJ·mol−1 was obtained. The biosensor had a wide linear response range from 5 × 10−7 to 1 × 10−4 M choline with a correlation coefficient of 0.9999 and a detection limit of 0.2 μM, and had a high sensitivity of 61.9 mA·M−1·cm−2 at 0.50 V and at pH 8.0. The apparent Michaelis constant and the optimum pH for the immobilized enzyme are 1.4 mM choline
and 8.4, respectively, which are very close to those of choline oxidase in solution. The effect of selected organic compounds
on the response of the choline biosensor was studied. 相似文献
972.
Toshiyuki Osakai Junpei Sawada Hirohisa Nagatani 《Analytical and bioanalytical chemistry》2009,395(4):1055-1061
The spectrofluorometric behavior of a membrane potential-sensitive dye, 1-(3-sulfonatopropyl)-4-[β-{2-(di-N-butylamino)-6-naphthyl}vinyl]pyridinium betaine (di-4-ANEPPS), at the polarized 1,2-dichloroethane/water interface was studied
by means of potential-modulated fluorescence (PMF) spectroscopy. The results, combined with those from cyclic and alternating
current voltammetry, clearly suggested that the dye adsorbed at the interface underwent a reorientation with increasing the
interfacial potential, giving a well-developed PMF response as well as a voltammetric response. In addition to the PMF response,
another PMF response was observed by addition of dilauroyl phosphatidylcholine (DLPC). This additional response was well explained
in terms of a reorientation of di-4-ANEPPS at the interface, which would be induced by the potential-dependent desorption
of DLPC from the interface. Thus, the present study supported the reorientation/solvatochromic mechanism for the membrane
potential-sensitive dye rather than the electrochromic mechanism. 相似文献
973.
A novel amperometric sensor for uric acid based on ordered mesoporous carbon modified pyrolytic graphite electrode was developed.
Uric acid oxidation was easily catalyzed by this electrode in a phosphate buffer solution at pH 7.0, with an anodic potential
decrease about 140 mV compared to bare pyrolytic graphite electrode. The uric acid level was determined by the amperometric
method, at a constant potential of 0.31 mV, the catalytic current of uric acid vs. its concentration showed a good linearity
in the range of 1.0 × 10−6−1.0 × 10−4 mol L−1, with a correlation coefficient of 0.999. The detection limit was 4.0 × 10−7 mol L−1. The proposed method could be effectively used for uric acid amperometric sensing in human urine. 相似文献
974.
Masakuni Tako Takeshi Teruya Yukihiro Tamaki Teruko Konishi 《Colloid and polymer science》2009,287(12):1445-1454
The 1H-nuclear magnetic resonance spectrum showed that the l-rhamnosyl residues of native gellan gum were coinvolved in both a small number of 4C1-pyranose conformations and a large number of 1C4-pyranose conformations, whereas for deacylated polymer, almost of the residues were involved in 4C1-pyranose conformation. The flow curves of native gellan gum showed plastic behavior above 0.2%. The elastic modulus stayed
at a constant value with increase in temperature up to 40 °C, then decreased rapidly. The elastic modulus increased with addition
of CaCl2 (6.8 mM) and stayed constant value with increase in temperature up to 65 °C, then decreased rapidly. The stronger elastic
modulus was observed in deacylated gellan gum with addition of CaCl2. The elastic modulus of native gellan gum showed larger value than that in aqueous solution in the presence of urea (4.0 M).
Intra- and intermolecular associations of native gellan gum molecules in the presence of Ca+2 were proposed. 相似文献
975.
R. M. Queiroz Luiza H. O. Pires Ruth C. P. de Souza J. R. Zamian A. G. de Souza G. N. da Rocha Filho C. E. F. da Costa 《Journal of Thermal Analysis and Calorimetry》2009,97(1):163-166
Hydrotalcite was synthesised by co-precipitation method, calcined and characterized by XRD, BET, IR and TG/DTA/DTG analyses
and tested as solid base catalyst in the transesterification of soybean oil with methanol, achieving a methyl ester content
of 99.5%. The thermal decomposition of hydrotalcite calcined occurred in four mass loss steps at 28, 105, 203 and 400 °C.
The hydrotalcite was recovered and through a simple evaluation by TG/DTA/DTG techniques it was found that at 500 °C is the
temperature, where the organic matter should be eliminated from the catalyst. This study shows the importance of thermal analysis
in the evaluation of the recovery temperature of hydrotalcite. 相似文献
976.
Matthew B. Kerby Jane C. Urban Lea Mouallem Anubhav Tripathi 《Applied biochemistry and biotechnology》2009,159(1):208-220
Proposed methods for detecting circulatory system disease include targeting ultrasound contrast agents to inflammatory markers
on vascular endothelial cells. For antibody-based therapies, soluble forms of the targeted adhesion proteins of the immunoglobulin
superfamily (IgSF) reduce adhesion yet were left unaccounted in prior reports. Microspheres labeled simply with a maximum
level of antibodies can reduce the diagnostic sensitivity by adhering to proteins expressed normally at a low level, while
sparsely coated particles may be rendered ineffective by circulating soluble forms of the targeted proteins. A new microdevice
technique is applied to simultaneously measure the adhesion profile to a series of IgSF-protein-coated surfaces. In this investigation,
we quantify the in vitro binding characteristics of 5-μm microspheres to oriented intercellular adhesion molecule-1 (ICAM-1)
and vascular cell adhesion molecule-1 (VCAM-1) protein-coated surfaces in the presence of human serum at physiological concentrations.
Defined regions of a slide were coated with recombinant chimeric Fc-human ICAM-1 and VCAM-1 in variable ratios but constant
total concentration. Monoclonal human anti-ICAM-1 or anti-VCAM-1 antibodies in competition with non-binding mouse anti-rabbit
antibodies coat the microsphere surface at a constant surface density with variable yet controlled surface activities. Using
multiple slide surface IgSF protein and microsphere antibody concentrations, an adhesion profile was developed for the microspheres
with and without IgSF proteins from human serum, which demonstrated that exposure to serum reduced microsphere binding, on
average, more than 50% compared to the no-serum condition.. The serum effects were limited to antibodies on the microsphere,
since binding inhibition was reversed after rinsing serum from the system and fresh antibody-coated microspheres were introduced.
This analysis quantifies the binding effects of soluble IgSF proteins from human serum on antibody-based targeted ultrasound
detection and drug delivery methods. 相似文献
977.
W. Z. Zhang Ma Shuang M. C. Zhu Liu Lei E. J. Gao 《Russian Journal of Coordination Chemistry》2009,35(12):874-878
A novel complex [Zn(Qina)2(DMSO)2] · 2DMSO (I) (Qina = quinaldic acid, DMSO = dimethyl sulfoxide) has been synthesized and characterized by X-ray diffraction, elementary analysis, and IR spectrum. The unit cell parameters for complex I: a = 8.2884(11), b = 22.015(3), c = 9.0685(12) Å, β = 100.61(0)°, V = 1626.41(40) Å3, Z = 2, space group, P21/n. In the complex I, the Zn(II) atom was six-coordinated to form a distorted octahedral geometry by two Qina ligands and two dimethyl sulfoxide molecules. The crystal structure is stabilized by hydrogen bonds, C - H... π, π-π stacking interaction between adjacent complexes. The binding of the complex I with calf thymus DNA has been investigated by fluorescence spectroscopic studies. The result suggested that the complex intercalates into DNA base pairs. 相似文献
978.
A convenient and inexpensive approach to the generation of 3-phenylcyclopropenes is described. Reaction of these compounds with a range of dienophiles and dipolarophiles led to the stereoselective formation of [4+2]- and [3+2]-cycloadducts, which were exclusively exo-3-phenyl-cis-1,2-disubstituted cyclopropanes. Efficient trapping of 1-lithio-3-phenylcyclopropene with different electrophiles is also discussed. Ab initio calculations suggest that the lowest energy conformation of 3-phenylcyclopropene has the plane of the benzene ring perpendicular to the cyclopropene π-bond but with a low rotation barrier. 相似文献
979.
The enantioselective O-allylic alkylation of acetophenone oxime with various Morita-Baylis-Hillman (MBH) carbonates has been accomplished by the catalysis of a commercially available cinchona alkaloid (DHQD)2PHAL. The corresponding O-allylic products were obtained in moderate to excellent yields up to 96% ee. 相似文献
980.
Alexander Pechenik D.H. Whitmore Mark A. Ratner 《Journal of solid state chemistry》1985,58(1):103-113
A Monte Carlo method is developed for simulation of mixed ionic conductivity in β″-alumina-type materials. The conduction plane of these materials is represented by a lattice gas model in which monovalent and divalent cation carriers diffuse via a vacancy mechanism and interact through a nearest-neighbor coulombic repulsion. By comparing experimental data for pure Na+ and pure Ba2+ β″-aluminas with simulation results, it is possible to estimate the near-neighbor interaction energies εi and jump barriers Ui for both kinds of ions. On the basis of these estimations the total ionic conductivity of Na+Ba2+ β″-alumina is calculated as a function of temperature and concentration of carriers. As Ba2+ replaces Na+, the conductivity initially increases as more vacancies become available. For very high temperatures, this increase continues until exchange is complete; but at lower temperatures, the conductivity reaches a peak for some optimal composition, and then drops off as the number of Ba2+, and hence the strength of ionic correlation, goes up. The presence of ordering in the fully exchanged (all Ba2+) case manifests itself in substantial curvature of the Arrhenius plots for conductivity. The activation energy for conductivity as a function of Ba2+ mole fraction (XBa2+) shows a pronounced rise near an X value of , in agreement with recent experimental observations. 相似文献