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701.
702.
Redondo AH Körber C König S Längin A Al-Ahmad A Weinmann W 《Analytical and bioanalytical chemistry》2012,402(7):2417-2424
Ethyl glucuronide (EtG) and ethyl sulfate (EtS) are direct alcohol consumption markers widely used nowadays for clinical and
forensic applications. They are detectable in blood and urine even after consumption of trace amounts of ethanol and for a
longer time frame, being detectable even when no more ethanol is present. The instability of EtG against bacterial degradation
in contaminated urine samples and/or the possible postcollection synthesis of this metabolite in samples containing, e.g.,
Escherichia coli and ethanol, may cause false identification of alcohol uptake. Therefore, it is of paramount importance to constrict these
error sources by inhibition of any bacterial growth causing hydrolization or synthesis of EtG. This study evaluates a new
method of collecting urine samples on filter paper, dried urine spots (DUS), for simultaneous detection of EtG, EtS and creatinine,
having the great advantage of inhibiting bacterial activity. In addition, a method validation for the determination of EtG
and EtS in DUS was performed according to the FDA guidelines. Sterile-filtered urine was spiked with EtG and EtS, inoculated
with E. coli and incubated. Liquid and dried urine samples were collected after various time intervals up to 96 h. Liquid samples were
frozen immediately after collection, whereas aliquots for DUS were pipetted onto filter paper, allowed to dry and stored at
RT until analysis 1 week after. The specimens were analyzed by LC–ESI–MS/MS. As expected, degradation of EtG, but not of EtS,
was observed in contaminated liquid urine samples. However, the specimens collected on filter paper and stored at RT showed
no degradation during storage. Therefore, collecting urine samples on filter paper for EtG and EtS analysis turns out to be
a reliable method to avoid bacterial degradation of EtG and EtS, and consequently, stabilization of these ethanol metabolites
is achieved. In addition, simultaneous measurement of creatinine content as an indicator of urine dilution helps to interpret
the results. Method validation for EtG and EtS in DUS was satisfactory, showing the linearity of the calibration curves in
the studied concentration range, good precision, accuracy and selectivity. 相似文献
703.
State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the electronic states in the A(1)Σ(u)(+), c(3)Π(u), and a(3)Σ(u)(+) manifold of the strontium dimer, the spin-orbit and nonadiabatic coupling matrix elements between the states in the manifold, and the electric transition dipole moment from the ground X(1)Σ(g)(+) to the nonrelativistic and relativistic states in the A+c+a manifold. The potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to single and double excitations for the transition moments. The spin-orbit and nonadiabatic coupling matrix elements were computed with the multireference configuration interaction method limited to single and double excitations. Our results for the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate substantially from recent ab initio calculations. The potential energy curve for the spectroscopically active (1)0(u)(+) state is in quantitative agreement with the empirical potential fitted to high-resolution Fourier transform spectra [A. Stein, H. Kno?ckel, and E. Tiemann, Eur. Phys. J. D 64, 227 (2011)]. The computed ab initio points were fitted to physically sound analytical expressions, and used in converged coupled channel calculations of the rovibrational energy levels in the A+c+a manifold and line strengths for the A(1)Σ(u)(+)←X(1)Σ(g (+) transitions. Positions and lifetimes of quasi-bound Feshbach resonances lying above the (1)S(0) + (3)P(1) dissociation limit were also obtained. Our results reproduce (semi)quantitatively the experimental data observed thus far. Predictions for on-going and future experiments are also reported. 相似文献
704.
A series of meso-substituted tetra-cationic porphyrins, which have methyl and octyl substituents, was studied in order to understand the effect of zinc chelation and photosensitizer subcellular localization in the mechanism of cell death. Zinc chelation does not change the photophysical properties of the photosensitizers (all molecules studied are type II photosensitizers) but affects considerably the interaction of the porphyrins with membranes, reducing mitochondrial accumulation. The total amount of intracellular reactive species induced by treating cells with photosensitizer and light is similar for zinc-chelated and free-base porphyrins that have the same alkyl substituent. Zinc-chelated porphyrins, which are poorly accumulated in mitochondria, show higher efficiency of cell death with features of apoptosis (higher MTT response compared with trypan blue staining, specific acridine orange/ethidium bromide staining, loss of mitochondrial transmembrane potential, stronger cytochrome c release and larger sub-G1 cell population), whereas nonchelated porphyrins, which are considerably more concentrated in mitochondria, triggered mainly necrotic cell death. We hypothesized that zinc-chelation protects the photoinduced properties of the porphyrins in the mitochondrial environment. 相似文献
705.
Goulay F Rebrion-Rowe C Biennier L Le Picard SD Canosa A Rowe BR 《The journal of physical chemistry. A》2006,110(9):3132-3137
The rate coefficient of the reaction of the methylidine radical CH with anthracene has been studied over a wide temperature range (58-470 K) in a dedicated "Cinétique de Réaction en Ecoulement Supersonique Uniforme" (Reaction Kinetics in Uniform Supersonic Flow) apparatus. The reaction exhibits a slight positive temperature dependence, which can be fitted to the expression k(T) = (3.32 +/- 1.00) x 10(-10)(T/298)((0.46+/-0.14)) cm3 molecule(-1) s(-1). Even at the lowest temperature, the reaction remains very fast indicating that the kinetics are probably driven by a capture process. 相似文献
706.
Kirakci K Cordier S Perrin C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(24):6419-6425
The double salts Rb(3)[Mo(6)Br(i) (7)Y(i)Br(a) (6)](Rb(3)[MoBr(6)])(3) (Y=Se, Te) result from the partial disproportionation of the Mo(6)Br(12) octahedral-cluster-based bromide, in the presence of corresponding chalcogenides and RbBr salt (crystal data: Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Te(i)Br(a) (6)] (1), Pm$\bar 3$m (No. 221), a=12.1558(2) A, Z=1, R(1)=0.028; wR(2)=0.050; Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Se(i)Br(a) (6)] (2), Pm$\bar 3$m, a=12.144(3) A, Z=1, R(1)=0.028; wR(2)=0.050). The structures of 1 and 2 are built up from [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units characterised by a random distribution of seven bromine and one chalcogen ligands on all the eight inner positions that face cap the Mo(6) clusters. Such a distribution implies a static orientational disorder of the [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) units around the origin of the unit cell. Close-packed anionic layers based on [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units are stacked in the sequence ABC. This arrangement leads to very short Br(a)--Br(a) intercluster unit distances of 3.252 A, much lower than the sum of the van der Waals radii (3.70 A). The trivalent oxidation state of molybdenum in the Mo complexes and 24 valence electrons per Mo(6) cluster have been confirmed by magnetic susceptibility measurements. Salts 1 and 2 constitute the first examples of structurally characterised bromides containing discrete [Mo(III)Br(6)](3-) complexes obtained by means of solid-state synthesis. 相似文献
707.
Christiane Kühn Rainer Beckert Manfred Friedrich Helmar Grls 《Journal of heterocyclic chemistry》2006,43(6):1569-1574
708.
Christiane Rose Katell Peoc’h Stéphanie Chasseigneaux Claire Paquet Julien Dumurgier Fanchon Bourasset Frédéric Calon Jean-Louis Laplanche Jacques Hugon Bernadette Allinquant 《BMC neuroscience》2012,13(1):1-11
Background
Exposure to ethanol during early development triggers severe neuronal death by activating multiple stress pathways and causes neurological disorders, such as fetal alcohol effects or fetal alcohol syndrome. This study investigated the effect of ethanol on intracellular events that predispose developing neurons for apoptosis via calcium-mediated signaling. Although the underlying molecular mechanisms of ethanol neurotoxicity are not completely determined, mitochondrial dysfunction, altered calcium homeostasis and apoptosis-related proteins have been implicated in ethanol neurotoxicity. The present study was designed to evaluate the neuroprotective mechanisms of metformin (Met) and thymoquinone (TQ) during ethanol toxicity in rat prenatal cortical neurons at gestational day (GD) 17.5.Results
We found that Met and TQ, separately and synergistically, increased cell viability after ethanol (100 mM) exposure for 12 hours and attenuated the elevation of cytosolic free calcium [Ca2+]c. Furthermore, Met and TQ maintained normal physiological mitochondrial transmembrane potential (????M), which is typically lowered by ethanol exposure. Increased cytosolic free [Ca2+]c and lowered mitochondrial transmembrane potential after ethanol exposure significantly decreased the expression of a key anti-apoptotic protein (Bcl-2), increased expression of Bax, and stimulated the release of cytochrome-c from mitochondria. Met and TQ treatment inhibited the apoptotic cascade by increasing Bcl-2 expression. These compounds also repressed the activation of caspase-9 and caspase-3 and reduced the cleavage of PARP-1. Morphological conformation of cell death was assessed by TUNEL, Fluoro-Jade-B, and PI staining. These staining methods demonstrated more cell death after ethanol treatment, while Met, TQ or Met plus TQ prevented ethanol-induced apoptotic cell death.Conclusion
These findings suggested that Met and TQ are strong protective agents against ethanol-induced neuronal apoptosis in primary rat cortical neurons. The collective data demonstrated that Met and TQ have the potential to ameliorate ethanol neurotoxicity and revealed a possible protective target mechanism for the damaging effects of ethanol during early brain development. 相似文献709.
The holographic techniques are applied to the kinetic study of a photopolymerization reaction under steady state illumination. A theoretical approach of this problem is introduced which allows the intrinsic initiating activity of several amine-derived radicals to be determined. 相似文献
710.
Ansgar Stratmann Thomas Schupp Christiane Toupet Wolfgang Schilling Lukas Oberer Rene Traber 《ChemInform》2002,33(41):222-222