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81.
Francesca Goldoni Dario Iarossi Adele Mucci Luisa Schenetti 《Journal of heterocyclic chemistry》1997,34(6):1801-1804
3,4′-Dibromo-2,2′-bithiophene was converted, in high yield, into the corresponding dibutoxy derivative. The 1H 13C and nmr data are discussed in comparison with those of 3,3′- and 4,4′-dibutoxy-2,2′-bithiophene in relation to regiochemistry. 相似文献
82.
Francesca CardonaEnrico Faggi Francesca LiguoriMartina Cacciarini Andrea Goti 《Tetrahedron letters》2003,44(11):2315-2318
Practical syntheses of nitrone 8 by two different approaches from sugars are reported. Its use as a versatile intermediate in highly selective 1,3-dipolar cycloaddition reactions constitutes the key step for novel total syntheses of hyacinthacine A2 (3) and 7-deoxycasuarine (20) by simple transformations of a common isoxazolidine adduct. 相似文献
83.
Air quality in Province of Trieste was studied in terms of PM10 trends. Observed correlations between PM10 and atmospheric pollutants produced by combustion are in evidence. Nitrogen oxides and PM10 are critical parameters for air quality in Province of Trieste. Wind speed has a diluting action higher than rain for all pollutants. 相似文献
84.
[structure: see text] The first example of two discrete calix[8]arene conformational isomers, 2 and 2a, has been obtained by exhaustive benzylation of 1,5-tetramethylene-bridged calix[8]arene 1. It is demonstrated, with the aid of X-ray crystallography, that these atropisomers have two 3/4-cone halves oriented syn or anti with respect to the bridge/bridgeheads moiety. VT NMR studies indicate that the tert-butyl-through-the-annulus inversion is inhibited in 1, while groups larger than n-hexyl or benzyl are required for curtailing the O-through-the-annulus route. 相似文献
85.
Bazzicalupi C Bencini A Bencini A Bianchi A Corana F Fusi V Giorgi C Paoli P Paoletti P Valtancoli B Zanchini C 《Inorganic chemistry》1996,35(19):5540-5548
Solutions containing Zn(II) and Cu(II) complexes with [15]aneN(3)O(2) rapidly adsorb atmospheric CO(2) to give {[ZnL](3)(&mgr;(3)-CO(3))}.(ClO(4))(4) (2) and {[CuL](3)(&mgr;(3)-CO(3))}.(ClO(4))(4) (4) complexes. The crystal structures of both complexes have been solved (for 2, space group R3c, a, b = 22.300(5) ?, c = 17.980(8) ?, V = 7743(4) ?(3), Z = 6, R = 0.0666, R(w)(2) = 0.1719; for 4, space group R3c, a, b = 22.292(7) ?, c = 10.096(8) ?, V = 7788(5) ?(3), Z = 6, R = 0.0598, R(w)(2) = 0.1611), and the spectromagnetic behavior of 4 has been studied. In both compounds a carbonate anion triply bridges three metal cations. Each metal is coordinated by one oxygen of the carbonate, three nitrogens, and an oxygen of the macrocycle; the latter donor weakly interacts with the metals. Although the two compounds are isomorphous, they are not isostructural, because the coordination geometries of Zn(II) in 2 and Cu(II) in 4 are different. The mixed complex {[CuZn(2)L(3)](&mgr;(3)-CO(3))}.(ClO(4))(4) has been synthesized. X-ray analysis (space group R3c, a, b = 22.323(7) ?, c = 17.989(9) ?, V = 7763(5) ?(3), Z = 6, R = 0.0477, R(w)(2) = 0.1371) and EPR measurements are in accord with a &mgr;(3)-carbonate bridging one Cu(II) and two Zn(II) ions in {[CuZn(2)L(3)](&mgr;(3)-CO(3))}(4+). Both the Zn(II) and Cu(II) cations exhibit the same coordination sphere, almost equal to that found in the trinuclear Zn(II) complex 2. The systems Zn(II)/L and Cu(II)/Lhave been studied by means of potentiometric measurements in 0.15 mol dm(-)(1) NaCl and in 0.1 mol dm(-)(3) NaClO(4) aqueous solutions; the species present in solution and their stability constants have been determined. In both systems [ML](2+) species and hydroxo complexes [M(II)LOH](+) (M = Zn, Cu) are present in solution. In the case of Cu(II), a [CuL(OH)(2)] complex is also found. The process of CO(2) fixation is due to the presence of such hydroxo-species, which can act as nucleophiles toward CO(2). In order to test the nucleophilic ability of the Zn(II) complexes, the kinetics of the promoted hydrolysis of p-nitrophenyl acetate has been studied. The [ZnLOH](+) complex promotes such a reaction, where the Zn(II)-bound OH(-) acts as a nucleophile to the carbonyl carbon. The equilibrium constants for the addition of HCO(3)(-) and CO(3)(2)(-) to the [ZnL](2+) complex have been potentiometrically determined. Only [ML(HCO(3))](+) and [ML(CO(3))] species are found in aqueous solution. A mechanism for the formation of {[ML](3)(&mgr;(3)-CO(3))}.(ClO(4))(4) is suggested. 相似文献
86.
Presti ML Ragusa S Trozzi A Dugo P Visinoni F Fazio A Dugo G Mondello L 《Journal of separation science》2005,28(3):273-280
Traditional hydrodistillation (HD), supercritical fluid extraction (SFE), organic solvent extraction (SE), and water microwave assisted hydrodistillation (MAHD) techniques were compared and evaluated for their effectiveness in the isolation of rosemary essential oil. The microwave assisted hydrodistillation technique was optimized in terms of both delivered power and time duration. The extracts/distillates were analyzed by GC and GC-MS. Microwave distillation, which exploits the physical action of microwaves on plants, showed a series of advantages over the other approaches: low cost, use of water in sample pre-treatment step, greatly reduced isolation time, and attainment of high quality essential oil distillate. Moreover, the absence of environmental impact of this innovative technique was also emphasized. 相似文献
87.
Francesca Porta Sergio Cenini Sergio Giordano Maddalena Pizzotti 《Journal of organometallic chemistry》1978,150(2):261-271
The complexes M(CO)2(PPh3)3 (I, M = Fe; II, M = Ru) readily react with H2 at room temperature and atmospheric pressure to give cis-M(H)2(CO)2(PPh3)2 (III, M = Fe;IV,M = Ru). I reacts with O2 to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis-Ru(O2)(CO)2(PPh3)2(V). Even compound IV reacts with O2 to give V with displacement of H2; this reaction has been shown to be reversible and this is the first case where the displacement of H2 by O2 and that of O2 by H2 at a metal center has been observed. III and IV are reduced to M(CO)3(PPh3)2 by CO with displacement of H2; Ru(CO)3- (PPh3)2 is also formed by treatment of IV with CO2, but under higher pressure. Compounds II and IV react with CH2CHCN to give Ru(CH2CHCN)(CO)2- (PPh3)2(VI) which reacts with H2 to reform the hydride IV.cis-Ru(H)2(CO)2(PPh3)2(IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H2 and O2 on the “Ru(CO)2(PPh3)2” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO)2(PPh3)3(II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere. 相似文献
88.
Ambrosi G Dapporto P Formica M Fusi V Giorgi L Guerri A Micheloni M Paoli P Pontellini R Rossi P 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3468-3474
The synthesis and characterization of two new macrocyclic ligands, the bis-macrocyclic compound 2,6-bis(1,4,13-triaza-7,10-dioxacyclopentadec-1-ylmethyl)phenol (L) and 38-methoxy-1,4,13,16,19,28-hexaaza-7,10,22,25-tetraoxatricyclo[14.14.7.1(32,36)]octatriconta-32,34,Delta(36,38)-triene (L1) are reported. Equilibrium studies of basicity and coordination properties toward metal ions such as Cu(II), Zn(II), Cd(II) and Pb(II) were performed for ligand by potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, I= 0.15 mol dm(-3)). L behaves as a hexaprotic base (logK(1)= 10.93, logK(2)= 9.70, logK(3)= 8.79, logK(4)= 8.05, logK(5)= 6.83, logK(6)= 2.55). All metal ions form stable mono- and dinuclear complexes: logK(MLH(-1))= 25.61 for Cu(II), 15.37 for Zn(II), 12.58 for Cd(II) and 13.79 for Pb(II); logK(M(2)LH(-1))= 31.61 for Cu(II), 23.38 for Zn(II), 24.49 for Cd(II) and 23.68 for Pb(II). All these dinuclear species show a great tendency to add the OH(-) group: the equilibrium constant for the addition reaction was found to be logK(M(2)LH(-1)OH)= 4.77 for Cu(II), 5.66 for Zn(II), 2.8 for Cd(II) and 3.18 for Pb(II). In the case of Ni(II), kinetic inertness prevents the possibility of solution studies. The dinuclear solid adducts [Ni(2)H(-1)L(N(3))(3)].EtOH and [Cu(2)H(-1)L(N(3))](ClO(4))(2) were characterized by X-ray analysis. 相似文献
89.
Natalizia Miceli Andreana Marino Ayşegül Köroğlu Francesco Cacciola Paola Dugo Luigi Mondello 《Natural product research》2020,34(11):1636-1641
AbstractThe purpose of this study was to conduct a comparative evaluation of some biological properties of methanol and water extracts of leaves of five Juniperus taxa growing in Turkey: J. communis L. var. communis (Jcc), J. communis L. var. saxatilis Pall. (Jcs), J. drupacea Labill. (Jd), J. oxycedrus L. subsp. oxycedrus (Joo), J. oxycedrus L. subsp. macrocarpa (Sibth. & Sm.) Ball. (Jom). The antioxidant properties were examined in vitro; both in the DPPH and in the reducing power tests, Joo methanol extract resulted the most active (IC50?=?0.09?±?0.01mg/mL and ASE/mL?=?2.56?±?0.06). In the TBA assay, Jcs methanol extract exhibited the highest activity (IC50?=?4.39?±?0.47?μg/mL). The extracts displayed bacteriostatic activity against Staphylococcus aureus, and Jd methanol extract resulted the most effective (MIC?=?19.53?μg/mL); no effect on the S. aureus biofilm formation was observed. The extracts resulted non-toxic in the Artemia salina lethality bioassay. Finally, the phenolic profile of the methanol extracts was characterized by HPLC-PDA/ESI-MS. 相似文献
90.
Ridi F Fratini E Mannelli F Baglioni P 《The journal of physical chemistry. B》2005,109(30):14727-14734
In the cement industry, the extrusion technique is used to produce flat shapes with improved resistance to compression. Extrusion is a plastic-forming process that consists of forcing a highly viscous plastic mixture through a shaped die. The material should be fluid enough to be mixed and to pass through the die, and on the other hand, the extruded specimen should be stiff enough to be handled without changing in shape or cracking. These characteristics are industrially obtained by adding cellulosic polymers to the mixture. The aim of this work is to understand the action mechanism of these additives on the major pure phases constituting a typical Portland cement: tricalcium silicate (C(3)S), dicalcium silicate (C(2)S), tricalcium aluminate (C(3)A), and tetracalcium iron-aluminate (C(4)AF). In particular, a methylhydroxyethyl cellulose (MHEC) was selected from the best-performing polymers for further study. The effect of this additive on the hydration kinetics (rate constants, activation energies, and diffusional constants) was evaluated by means of differential scanning calorimetry (DSC) while the hydration products were studied by using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). MHEC addition in calcium silicate pastes produces an increase in the induction time without affecting the nucleation-and-growth period. A less dense CSH gel was deduced from the diffusional constants in the presence of MHEC. Moreover, CSH laminar features and poorly structured hydrates were noted during the first hours of hydration. In the case of the aluminous phases, the additive inhibits the growth of stable cubic hydrated phases (C(3)AH(6)), with the advantage of the metastable hexagonal phases being formed in the earliest minutes of hydration. 相似文献