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991.
Ian C. McNeill 《Macromolecular Symposia》1993,74(1):11-20
The relationship between flammability and thermal degradation is the consequence of the burning cycle needed to sustain fire. Thermal degradation behaviour of polymers is discussed in relation to generation of fuel and other products, including flame quenchers, and the production of char. The thermal degradation behaviour of the main classes of fire retardant is considered and illustrated by examples of the ways in which specific fire retardants exert their effect on a particular polymer. 相似文献
992.
Squaramides are remarkable four-membered ring systems derived from squaric acid that are able to form up to four hydrogen bonds. A high affinity for hydrogen bonding is driven through a concomitant increase in aromaticity of the ring. This hydrogen bonding and aromatic switching, in combination with structural rigidity, have been exploited in many of the applications of squaramides. Substituted squaramides can be accessed via modular synthesis under relatively mild or aqueous conditions, making them ideal units for bioconjugation and supramolecular chemistry. In this tutorial review the fundamental electronic and structural properties of squaramides are explored to rationalise the geometry, conformation, reactivity and biological activity. 相似文献
993.
Mason K Gass IA White FJ Papaefstathiou GS Brechin EK Tasker PA 《Dalton transactions (Cambridge, England : 2003)》2011,40(12):2875-2881
The syntheses, structures and magnetic properties of six iron complexes stabilised with the derivatised salicylaldoxime ligands Me-saoH(2) (2-hydroxyethanone oxime) and Et-saoH(2) (2-hydroxypropiophenone oxime) are discussed. The four hexanuclear and two octanuclear complexes of formulae [Fe(8)O(2)(OMe)(4)(Me-sao)(6)Br(4)(py)(4)]·2Et(2)O·MeOH (1·2Et(2)O·MeOH), [Fe(8)O(2)(OMe)(3.85)(N(3))(4.15)(Me-sao)(6)(py)(2)] (2), [Fe(6)O(2)(O(2)CPh-4-NO(2))(4)(Me-sao)(2)(OMe)(4)Cl(2)(py)(2)] (3), [Fe(6)O(2)(O(2)CPh-4-NO(2))(4)(Et-sao)(2)(OMe)(4)Cl(2)(py)(2)]·2Et(2)O·MeOH (4·2Et(2)O·MeOH), [HNEt(3)](2)[Fe(6)O(2)(Me-sao)(4)(SO(4))(2)(OMe)(4)(MeOH)(2)] (5) and [HNEt(3)](2)[Fe(6)O(2)(Et-sao)(4)(SO(4))(2)(OMe)(4)(MeOH)(2)] (6) all are built from a series of edge-sharing [Fe(4)(μ(4)-O)](10+) tetrahedra. Complexes 1 and 2 display a new μ(4)-coordination mode of the oxime ligand and join a small group of Fe-phenolic oxime complexes with nuclearity greater than six. 相似文献
994.
Zhang X Taylor D Thomas R Penfold J Tucker I 《Langmuir : the ACS journal of surfaces and colloids》2011,27(7):3569-3577
The manipulation of the adsorption of the anionic surfactant, sodium dodecyl sulfate, SDS, onto hydrophilic silica by the polyelectrolytes, polyethyleneimine, PEI, ethoxylated PEI, and the polyamine, pentaethylenehexamine, has been studied using neutron reflectometry. The adsorption of a thin PEI layer onto hydrophilic silica promotes a strong reversible adsorption of the SDS through surface charge reversal induced by the PEI at pH 7. At pH 2.4, a much thicker adsorbed PEI layer is partially swelled by the SDS, and the SDS adsorption is now no longer completely reversible. At pH 10, there is some penetration of SDS and solvent into a thin PEI layer, and the SDS adsorption is again not fully reversible. Ethoxylation of the PEI (PEI-EO(1) and PEI-EO(7)) results in a much weaker and fragile PEI and SDS adsorption at both pH 3 and pH 10, and both polymer and surfactant desorb at higher surfactant concentrations (>critical micellar concentration, cmc). For the polyamine, pentaethylenehexamine, adsorption of a layer of intermediate thickness is observed at pH 10, but at pH 3, no polyamine adsorption is evident; and at both pH 3 and pH 10, no SDS adsorption is observed. The results presented here show that, for the amine-based polyelectrolytes, polymer architecture, molecular weight, and pH can be used to manipulate the surface affinity for anionic surfactant (SDS) adsorption onto polyelectrolyte-coated hydrophilic silica surfaces. 相似文献
995.
Patel BA Arundell M Quek RG Harvey SL Ellis IR Florence MM Cass AE Schor AM O'Hare D 《Analytical and bioanalytical chemistry》2008,390(5):1379-1387
We have fabricated a six individual addressable gold working electrode microarray. The device is wirebonded to an eight-pin
DIL package that can be easily interconnected to an external multi-channel potentiostat. A polyion complex film coating on
the electrode surface provides a suitable coating for the growth of cells. The responses of oxygen and nitric oxide were assessed
on uncoated and coated devices using electroanalytical methods. The film coating reduced the diffusion current by approximately
20% in both cases. No changes in the electrochemical mechanism were observed. Simultaneous recordings were obtained for 2 h
in the presence of the cells, thus the device is stable for the duration of the bioanalytical measurements. Measurements were
conducted to study the simultaneous changes in oxygen and nitric oxide levels in cultured fibroblast cells in the presence
of growth hormones that cause cell proliferation. Increases in oxygen consumption of the cells were coupled with increases
in nitric oxide levels when in the presence of the growth hormones. Use of a biological detergent to cause an oxidative burst
resulted in a large increase in the current for potentials set to detect nitric oxide and oxygen. 相似文献
996.
Ian Westmoreland 《Journal of organometallic chemistry》2006,691(10):2228-2236
Treatment of chiral non-racemic salicyloxazoline proligands HL with tetrabenzylzirconium(IV) gave species [L2Zr(CH2Ph)2]. Reactions of KL with ZrCl4(THF)2 gave similar chloro complexes. One example of a benzyl complex was shown to exist as the Λ-trans,cis,cis diastereomer by X-ray crystallography. DFT calculations showed the observed isomer to be the most stable by 35 kJ mol−1, indicating that thermodynamic diastereoselection for this species is excellent. Examination of the chiral environment about the benzyl co-ligands indicates however that the degree of expression of the chirality of the structure in what would be the site of metal-based reactions is poor in comparison to related systems. Variable temperature 1H NMR data are consistent with this in that the low temperature spectrum exhibits a very small chemical shift difference between the chemically inequivalent benzylic CH atoms, and at higher temperatures dissociation of the portion of the ligand that contains the chiral information, i.e., the oxazoline unit, leads to apparent equivalence. 相似文献
997.
We report rate coefficients (k(tot,N(i))) for total removal of CN(X(2)Sigma(+), v = 2, N(i)) radicals from selected rotational levels (N(i) = 0, 1, 6, 10, 15 and 20) and for state-to-state rotational energy transfer (k(i-->f)) between levels N(i) and other rotational levels N(f) in single collisions with N(2). CN radicals have been generated using two sources: (a) the pulsed laser photolysis of ICN at 266 nm, which generates translationally 'hot' CN radicals; and (b) the pulsed laser photolysis of NCNO at 570 nm, which generates CN radicals with translational energies close to the average value at 298 K. Comparison of the values of k(tot,N(i)) obtained using these two sources of CN demonstrates: firstly, that the same results are obtained as long as time is allowed for the translationally hot CN radicals generated from ICN to be thermalised before radicals are promoted to a specific rotational level in v = 2 using a tuneable infrared 'pump' laser operating at ca. 2.45 micro m; and secondly, that the rate coefficients decrease, but the averaged cross-sections remain approximately constant, as the excess translational energy in CN radicals is moderated by collisions. With NCNO as the source of CN radicals, the observed values of k(tot,N(i)) do not depend on the delay between the pulses from the photolysis and pump lasers. Finally, we demonstrate that, for the non-reactive collision partner N(2) and with allowances made for the rate coefficients that are too small to measure directly, the sum of the state-to-state rate coefficients, Sigma(f)k(i-->f), for rotational energy transfer from a selected initial level N(i) agrees quite well with the value of k(tot,N(i)) for total transfer from the same initial level. The values of k(tot,N(i)) and of the state-to-state rate coefficients are compared with similar, earlier, results in which helium and argon were the collision partners. The relevance of these results to the study of collisions of CN with reactive collision partners is briefly discussed. 相似文献
998.
José Luis Serrano Luis García José Pérez Eduardo Pérez Joaquín García Gregorio Sánchez Gregorio López Ian J.S. Fairlamb Malva Liu 《Polyhedron》2008
The dinuclear hydroxo complex [{Pd(μ-OH)(Phox)}2] (I) (Phox = 2-(2-oxazolinyl)phenyl) reacts in a 1:2 molar ratio with several imidate ligands to yield new cyclometallated palladium complexes [{Pd(μ-NCO)(Phox)}2] containing asymmetric imidate –NCO– bridging units. [–NCO– = succinimidate (succ) (1), phtalimidate (phtal) (2), maleimidate (mal) (3), 2,3-dibromomaleimidate (2,3-diBrmal) (4) and glutarimidate (glut) (5)]. The reaction of these complexes with tertiary phosphines provides novel mononuclear N-bonded imidate derivatives of the general formula [Pd(imidate)(Phox)(PR3)] [R = Ph (a), 4-F–C6H4 (b) or CH2CH2CN (c)]. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, FAB, 1H, 13C and 31P). The single-crystal structures of compounds 4, 4a and 5a have been established. 相似文献
999.
Gopinahtan Sankar N. Raveendran Shiju Ian D. Watts Serge Nikitenko Wim Bras 《Research on Chemical Intermediates》2008,34(5-7):649-658
The structure of iron and managanese ions substituted in the framework of nanoporous AlPO-5 is determined by ex situ and in situ X-ray absorption spectroscopy. Fe K-edge XANES and EXAFS studies clearly indicate that iron ions are present as Fe(III) in octahedral coordination in the assynthesised material and tetrahedral coordination in the calcined material in both pure FeAlPO-5 and FeMnalPO-5. XANES and EXAFS results also indicate that reaction with hydrogen peroxide causes the removal of Fe(III) ions from the framework. Mn K-edge XANES and EXAFS of FeMnAlPO-5 samples indicate that Mn(II) ions are present in the framework, tetrahedrally coordinated, in the as-synthesised material but upon calcination it is found that the Mn(II) ions are removed from the framework, suggesting a different synthesis strategy is necessary to stabilise the Mn(II) ions in the framework simultaneously with Fe(III) ions. 相似文献
1000.
Christopher J. Smith Stefanie Shillingford Anthony M. Edge Christopher Bailey Ian D. Wilson 《Chromatographia》2008,67(9-10):673-678
High temperature liquid chromatography (HTLC), with water as the mobile phase, combined with ICP-MS tuned to the detection of Br, for quantification, and a linear ion trap MS, for structural identification, were applied to determine the disposition and metabolic fate of 2-, 3- and 4-bromobenzoic acids (BBAs) following in vitro incubation with rat hepatocytes at 4 mM. The separation of the metabolites was performed using a thermal gradient to increase the eluotropic strength of the aqueous mobile phase through the run to elute less polar components. The use of highly aqueous solvents for separations involving ICP-MS is advantageous because the water does not change the conductivity of the plasma thereby providing a more stable system. The improved system stability resulted in better sensitivity, as shown by the increased signal intensity for HTLC compared to conventional reversed-phase separations. Using HTLC to investigate the in vitro metabolic fate of the BBAs showed the major route of metabolism to be glycine conjugation, irrespective of the structure of the parent, but with different amounts produced depending on the positional isomer. The comparison of HTLC with the conventional methodology showed that chromatography at elevated temperatures had no effect on the observed metabolite profile. HTLC was also applied to urine obtained from an in vivo sample and showed an improved chromatographic peak shape compared to conventional liquid chromatography (LC) whilst providing the same analytical result. 相似文献