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101.
Truong Xuan Vuong Joseph Stephen Tu Binh Minh Thu Thuy Thi Nguyen Tuan Hung Duong Dung Thuy Nguyen Pham 《Molecules (Basel, Switzerland)》2022,27(22)
Heavy metal contamination in agricultural land is an alarming issue in Vietnam. It is necessary to develop suitable remediation methods for environmental and farming purposes. The present study investigated the effectiveness of using peanut shell-derived biochar to remediate the two heavy metals Zn and Pb in laboratory soil assays following Tessier’s sequential extraction procedure. The concentration of heavy metals was analyzed using Inductively coupled plasma mass spectrometry (ICP-MS). This study also compared the effectiveness of the blend of biochar and apatite applied and the mere biochar amendment on the chemical fractions of Pb and Zn in the contaminated agricultural soil. Results have shown that the investigated soil was extremely polluted by Pb (3047.8 mg kg−1) and Zn (2034.3 mg kg−1). In addition, the pH, organic carbon, and electrical conductivity values of amended soil samples increased with the increase in the amendment’s ratios. The distribution of heavy metals in soil samples was in the descending order of carbonate fraction (F2) > residue fraction (F5) > exchangeable fraction (F1) > Fe/Mn oxide fraction (F3) > organic fraction (F4) for Pb and F5 F2 > F1 > F3 > F4 for Zn. The peanut shell-derived biochar produced at 400 °C and 600 °C amended at a 10% ratio (PB4:10 and PB6:10) could significantly reduce the exchangeable fraction Zn from 424.82 mg kg−1 to 277.69 mg kg−1 and 302.89 mg kg−1, respectively, and Pb from 495.77 mg kg−1 to 234.55 mg kg−1 and 275.15 mg kg−1, respectively, and immobilize them in soil. Amending the biochar and apatite combination increased the soil pH, then produced a highly negative charge on the soil surface and facilitated Pb and Zn adsorption. This study shows that the amendment of biochar and biochar blended with apatite could stabilize Pb and Zn fractions, indicating the potential of these amendments to remediate Pb and Zn in contaminated soil. 相似文献
102.
This paper reports the results of an analytical study comparing capillary gas chromatography (GC) operated in the normal mode with 2 new GC techniques, comprehensive GC (GC x GC) and targeted (or selective) multidimensional GC, which use a longitudinally modulated cryogenic system (LMCS), recently developed in our laboratory. A high-temperature application of derivatized sterols, of interest in fecal pollution monitoring, was chosen for this work. A directly connected coupled-column ensemble was used, comprising a nonpolar column and a moderately polar column. With LMCS, effluent from the first column is zone-compressed in a cryogenic trap and then pulsed to a short second column, producing narrower peaks with sharp, tall peak responses at the detector. The modulator is operated at a constant frequency, e.g., 0.25 s(-1), to produce the GC x GC result, or is moved in a predefined manner so that whole peaks are selectively trapped and subsequently pulsed through to the second column in the targeted mode. Standard solutions containing a mixture of 7 sterols and 5-alpha-cholestane internal standard were used. Detection sensitivity is increased by a factor of >25 with the use of LMCS. The estimated limit of detection was about 0.1 microg/mL when normal GC with flame ionization detection (GC/FID) and a 1.0 microL splitless injection volume were used, compared with 0.02 and 0.004 microg/mL for the LMCS operated in GC x GC and selective modes, respectively. Calibration curves for GC/FID were linear over the 0.1-2.0 microg/mL range tested. Reproducibilities for the GC x GC and normal GC modes were comparable; generally, relative standard deviations (RSD) were on the order of 3-4%, based on raw peak responses. Improved reproducibility was found for selective LMCS operation, at an RSD of around 2%; with internal standardization, better results were achieved. The coupled-column arrangement allowed complete separation of sterol peaks from overlapping impurity peaks in a number of instances with LMCS modes, and its use should improve data quality over that of normal GC operation, in which the overlapping peaks interfere with measurement of peak response in the normal mode. 相似文献
103.
Jimmy Truong Ravish K. Akhani Lazaros Kakalis Wayne F.K. Schnatter 《Tetrahedron letters》2010,51(6):921-4837
1-Chloroalkynes and 1-bromohexyne undergo cycloaddition reactions with ethoxyvinylketeneiron(0) complexes to form chloro and bromocatechols. With most substituents, the halogen is incorporated ortho to the phenolic hydroxyl group regioselectively. With chloroethyne, chlorohexyne, and methyl chloropropiolate, the reverse regioselection is observed. Ab initio calculations reveal that the products are, in most cases, nearly isoenergetic, which indicates that the intermediate ketene-alkyne adduct geometry must be important in determining the product distribution. 相似文献
104.
The kinetics of the hydrogen abstraction at alkanes by formyl radicals is investigated using the reaction class transition
state theory (RC-TST) approach combined with the linear energy relationship (LER) or the barrier height grouping (BHG). The
rate constants of a reaction in this class can be estimated through those of the reference reaction, CHO + C2H6, which are obtained from rate constants of the reaction that involves the smallest species, namely CHO + CH4, using the explicit RC-TST scaling. The thermal rate constants of this smallest reaction are evaluated at the canonical variational
transition state theory (CVT) with the corrections from the small-curvature tunneling (SCT) and hindered rotation (HR) treatments.
Our analyses indicate that less than 40% systematic errors, on the average, exist in the predicted rate constants using both
the LER approach, where only reaction energy is needed, and the BHG approach, where no additional information is needed; while
comparing to explicit rate calculations the differences are less than 60%.
Contribution to Mark S. Gordon 65th Birthday Festschrift Issue. 相似文献
105.
Truong Son Pham László Balázs Imre Petneházy Zsuzsa Jászay 《Tetrahedron: Asymmetry》2010,21(3):346-351
An enantioselective Michael addition of diethyl cyanomethyl phosphonate to chalcones catalysed by bifunctional catalysts based on cinchona alkaloids has been developed, producing enantiomerically enriched cyanophosphonate precursors of α-substituted β-aminophosphonates. 相似文献
106.
The dissociation mechanism of a water molecule at an oxygen vacancy on the MgO(100) surface was studied by using the embedded cluster method at the DFT/B3 LYP level, while the energetic information was refined by using the IMOMO method at the CCSD level. We found that a water molecule initially adsorbs on one of the magnesium ions surrounding the vacancy site with a binding energy of 15.98 kcal mol(-1). It then can dissociate on the MgO(100) surface along two possible dissociation pathways. One pathway produces a hydroxyl group bonded to the original magnesium with a proton filling the vacancy via a transition state with a barrier of 4.67 kcal mol(-1) relative to the adsorbed water configuration. The other pathway yields two hydroxy groups; the hydroxy group originally belonging to the water molecule fills the vacancy, while the hydrogen atom binds with the surface oxygen to form the other hydroxy group. Hydrogen atoms of these hydroxy groups can recombine to form a hydrogen molecule and the surface is healed. Although the barrier (14.09 kcal mol(-1)) of the rate-controlling step of the latter pathway is higher than that of the former one, the energies of all of its stationary points are lower than that of the separated reactants (H(2)O+cluster). The effects of water coadsorption are modeled by placing an additional water molecule near the active center, which suggests that the more coadsorbed water molecules further stabilize the hydroxy species and prevent the hydrogen molecule formation through the latter pathway. The results support the photoemission spectral evidence of water dissociation on the defective MgO(100) surface at low water coverage. 相似文献
107.
In this paper we introduce and study enhanced notions of relative Pareto minimizers for constrained multiobjective problems
that are defined via several kinds of relative interiors of ordering cones and occupy intermediate positions between the classical
notions of Pareto and weak Pareto efficiency/minimality. Using advanced tools of variational analysis and generalized differentiation,
we establish the existence of relative Pareto minimizers for general multiobjective problems under a refined version of the
subdifferential Palais-Smale condition for set-valued mappings with values in partially ordered spaces and then derive necessary
optimality conditions for these minimizers (as well as for conventional efficient and weak efficient counterparts) that are
new in both finite-dimensional and infinite-dimensional settings. Our proofs are based on variational and extremal principles
of variational analysis; in particular, on new versions of the Ekeland variational principle and the subdifferential variational
principle for set-valued and single-valued mappings in infinite-dimensional spaces. 相似文献
108.
Shulim Kaliman Frank Kutzschebauch Tuyen Trung Truong 《Israel Journal of Mathematics》2018,228(1):229-247
A smooth complex quasi-affine algebraic variety Y is flexible if its special group SAut(Y) of automorphisms (generated by the elements of one-dimensional unipotent subgroups of Aut(Y)) acts transitively on Y, and an algebraic variety is stably flexible if its product with some affine space is flexible. An irreducible algebraic variety X is locally stably flexible if it is a union of a finite number of Zariski open sets each of which is stably flexible. The main result of this paper states that the blowup of a locally stably flexible variety along a smooth algebraic subvariety (not necessarily equidimensional or connected) is subelliptic, and, therefore, it is an Oka manifold. 相似文献
109.
Le Xuan Truong Le Thi Phuong Ngoc Alain Pham Ngoc Dinh Nguyen Thanh Long 《Nonlinear Analysis: Real World Applications》2010,11(3):1289-1303
This paper is concerned with the existence and the regularity of global solutions to the linear wave equation associated the boundary conditions of two-point type. We also investigate the decay properties of the global solutions to this problem by the construction of a suitable Lyapunov functional. Finally, we present some numerical results. 相似文献
110.
Tran Duc Thiep Truong Thi An Nguyen Tuan Khai Phan Viet Cuong Nguyen The Vinh 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):161-167
We have determined the isomeric ratio of 85m,gSr in photonuclear reactions of natural strontium induced by bremsstrahlungs with end-point energies in the giant dipole resonance
(GDR) region as well as the isomeric ratios of 85m,gSr and 84m,gRb produced at 65 MeV bremsstrahlung. In GDR region the target was irradiated at electron accelerator Microtron MT-25 of the
Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The target irradiation with 65 MeV
bremsstrahlung was performed at the linear electron accelerator of the Pohang Neutron Facility, Pohang, South Korea. The gamma
spectra of the samples irradiated in both cases were measured with spectroscopic systems consisting of 8192 channel analyzer
and high-energy resolution (180 keV at gamma ray 1332 keV of 60Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results
were discussed and compared with those of other authors. 相似文献