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991.
《Journal of Coordination Chemistry》2012,65(19):3481-3491
[Cu(L)(NO3)2] (1) and [Cu(L)(H2O)2](SCN)2 (2) [L?=?3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.07,12)docosane] have been prepared and structurally characterized by single-crystal X-ray diffraction at 100?K. For these constrained macrocycle complexes, copper(II) exists in a tetragonally distorted octahedral environment with the four nitrogen atoms of the macrocyclic ligands and two oxygen atoms from either nitrate or water in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans-III conformation. The Cu–N distances are 2.021(2)–2.047(2)?Å and typical but the axial ligands are weakly coordinating, with Cu–O bond lengths, 2.506(2)?Å for 1 and 2.569(2)?Å for 2, due to the pseudo Jahn–Teller effect. The crystals are stabilized by a 3-D network by intra and intermolecular hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms and nitrate in 1, and intermolecular hydrogen bonds are formed by water and thiocyanates in 2. The electronic absorption and IR spectral properties are also discussed. 相似文献
992.
Dr. Matthias W. Löble María Casimiro Dr. Dominique T. Thielemann Dr. Pascual Oña‐Burgos Prof. Dr. Ignacio Fernández Prof. Dr. Peter W. Roesky Prof. Dr. Frank Breher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(17):5325-5334
2D 1H,89Y heteronuclear shift correlation through scalar coupling has been applied to the chemical‐shift determination of a set of yttrium complexes with various nuclearities. This method allowed the determination of 89Y NMR data in a short period of time. Multinuclear NMR spectroscopy as function of temperature, PGSE NMR‐diffusion experiments, heteronuclear NOE measurements, and X‐ray crystallography were applied to determine the structures of [Y5(OH)5(L ‐Val)4(Ph2acac)6] ( 1 ) (Ph2acac=dibenzoylmethanide, L ‐Val=L ‐valine), [Y( 2 )(OTf)3] ( 3 ), and [Y2( 4 )(OTf)5] ( 5 ) ( 2 : [(S)P{N(Me)N?C(H)Py}3], 4 : [B{N(Me)N?C(H)Py}4]?) in solution and in the solid state. The structures found in the solid state are retained in solution, where averaged structures were observed. NMR diffusion measurements helped us to understand the nuclearity of compounds 3 and 5 in solution. 1H,19F HOESY and 19F,19F EXSY data revealed that the anions are specifically located in particular regions of space, which nicely correlated with the geometries found in the X‐ray structures. 相似文献
993.
Dr. Jean‐François Létard Dr. Saket Asthana Helena J. Shepherd Dr. Philippe Guionneau Dr. André E. Goeta Naohiko Suemura Ryuta Ishikawa Prof. Sumio Kaizaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):5924-5934
A comprehensive study of the magnetic and photomagnetic behaviors of cis‐[Fe(picen)(NCS)2] (picen=N,N′‐bis(2‐pyridylmethyl)1,2‐ethanediamine) was carried out. The spin‐equilibration was extremely slow in the vicinity of the thermal spin‐transition. When the cooling speed was slower than 0.1 K min?1, this complex was characterized by an abrupt thermal spin‐transition at about 70 K. Measurement of the kinetics in the range 60–70 K was performed to approach the quasi‐static hysteresis loop. At low temperatures, the metastable HS state was quenched by a rapid freezing process and the critical T(TIESST) temperature, which was associated with the thermally induced excited spin‐state‐trapping (TIESST) effect, was measured. At 10 K, this complex also exhibited the well‐known light‐induced excited spin‐state‐trapping (LIESST) effect and the T(LIESST) temperature was determined. The kinetics of the metastable HS states, which were generated from the freezing effect and from the light‐induced excitation, was studied. Single‐crystal X‐ray diffraction as a function of speed‐cooling and light conditions at 30 K revealed the mechanism of the spin‐crossover in this complex as well as some direct relationships between its structural properties and its spin state. This spin‐crossover (SCO) material represents a fascinating example in which the metastability of the HS state is in close vicinity to the thermal spin‐transition region. Moreover, it is a beautiful example of a complex in which the metastable HS states can be generated, and then compared, either by the freezing effect or by the LIESST effect. 相似文献
994.
Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II) > Cu(II) > Cd(II) > Ni(II) > Mn(II) and Zn(II) > Cu(II) > Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn > Cd > Cu > Ni > Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8. 相似文献
995.
《Physics and Chemistry of Liquids》2012,50(6):641-648
The complex formation reaction between N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) di-Schiff base ligand as an electron donor and iron(III) chloride as an electron acceptor have been studied spectrophometrically in methanol at 28°C. The values of equilibrium constants, K and molar absorptivities, ε were obtained from the Benesi–Hildebrand, Scott and Foster–Hammick–Wardley equations. The results indicate the formation of 1?:?1 charge transfer complex. The absorption band energy of the complex, E CT, the ionization potential of the BPIE Schiff base ligand, I D, and the Gibbs energy changes of the above reaction, ΔG 0, were calculated. Finally, the kinetics of the complex formation reaction were studied and was found to be second-order in each reactant. The values of the rate constants of the forward and reverse reactions k 1 and k ?1 were determined. 相似文献
996.
In situ-generated (bis-DPPMB)-Cu(OTf)2 complex has been examined to catalyze a tandem olefin migration and Prins cyclization of an alkenol with various aldehydes. The reaction proceeded with electron-rich aromatic aldehydes at room temperature and provided functionalized tetrahydropyrans in good yields. An efficient synthesis of the bis-DPPMB ligand has also been described. 相似文献
997.
《Analytical letters》2012,45(15):3373-3395
ABSTRACT Porous solid siloxane polymer carrying glycinate functional group of formula –(CH2)3NHCH2COOH has been prepared by the sol-gel process. Treatment of aqueous solutions of divalent metal ions with the polysiloxane glycinate ligand system demonstrates that this material exhibits high potential for preconcentration of metal ions (Cu2+, Zn2+ and Cd2+). The ligand system chemisorbs these divalent metal ions, at optimum conditions, in the order: Cd2+ < Zn2+ < Cu2+. The uptake of copper ions is concentration dependent but it is independent on the presence of other competing ions. Treatment of the glycinate ligand system with acidic solution results in leaching of bound ligands. The highest leaching occurs in presence of copper ions at low pH 相似文献
998.
《Analytical letters》2012,45(15):2411-2429
Abstract A nickel(II) [Ni(II)] ion-selective electrode was prepared by incorporating a new N-S Schiff base ligand, glyoxal-bis(S-benzyldithiocarbazate) (GBSB), as a neutral carrier into the PVC matrix. The proposed electrode exhibits an excellent near-Nernstian response for Ni2+ ions, ranging from 2.8 × 10?7 to 1.0 × 10?1 mol/L with a detection limit of 1.2 × 10?7 mol/L and a slope of 31.9 ± 0.3 mV/dec in pH 4.0 nitrate buffer solution at 25°C. It has an appropriate response time and suitable reproducibility and can be used for at least 3 months. The operational pH range of the proposed electrode is 4.0–7.5. The response mechanism is discussed in view of the alternating current (AC) impedance technique. In addition, the electrode was successfully used as an indicator electrode in potentiometric titration of Ni2+ ion and in the direct determination of Ni2+ ion in milk power and chocolate samples. 相似文献
999.
Effect of fulvic acid on neodymium uptake by goethite 总被引:1,自引:0,他引:1
Christopher R. Armstrong 《Journal of colloid and interface science》2012,387(1):228-233
Experimental studies of the interaction of aqueous neodymium (Nd), Suwannee River fulvic acid (FA), and solid phase goethite were conducted. Results from blank systems (individual Nd and FA), binary systems (Nd-goethite, FA-goethite, and Nd-FA), and ternary systems (Nd-FA-goethite) at 0.1 mol/kg and 25 °C are reported.In the binary Nd-goethite system a classic sorption edge is observed, whereby virtually all Nd is removed from solution above the goethite point of zero charge (PZC). Similarly, the binary FA-goethite system exhibits strong FA sorption; However in this system near complete removal of FA from solution is observed below the goethite PZC. In the binary Nd-FA system, both aqueous Nd and FA feature a sharp decrease in concentration at ca. pH 9.Various experiments in the ternary system were conducted. For all concentrations, FA enhanced Nd sorption below the goethite PZC, attributed to the formation of a Type B ternary surface complex (mineral-ligand-metal ion). Notably, the 100 ppm FA ternary system showed anomalously high dissolved Nd in solution above the PZC (i.e., Nd sorption suppression) and a concomitant increase in goethite dissolution (∼9 ppm total Fe3+ observed above circa pH 9.5).Our results suggest that Nd-FA complexation plays a key role in Nd uptake by goethite, and that this process is largely governed by pH: Whereas at pHs below the goethite PZC, Nd-FA complexation facilitates Nd sorption, above the PZC, and particularly at elevated FA concentrations, the formation of aqueous Nd-FA complexes suppresses Nd removal. Moreover, under these conditions, goethite dissolution may also play a role in mitigating Nd uptake by goethite. 相似文献
1000.
《Journal of Coordination Chemistry》2012,65(5):825-832