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81.
The axial single-crystal magnetic circular dichroism spectra of Cs3ZnCl5/Co2+ and Cs3ZnBr5/Co2+ have been measured over the 4000–7000 cm?1 region of the 4A2 → 4T1 (F) transition at ambient and liquid-helium temperature. The B/D and C/D terms obtained give transition moment ratios, 〈t2∥m∥t2〉/〈e∥m∥t2〉, in accord with the value required (?3/2) by a dynamic ligand-polarisation model for d-electron transition probabilities in tetrahedral metal complexes. 相似文献
82.
Determination of tin in soil by continuous hydride generation and inductively coupled plasma mass spectrometry 总被引:2,自引:0,他引:2
A method was investigated for the determination of Sn in soil samples by KOH fusion followed by continuous hydride generation coupled with inductively coupled plasma mass spectrometry (HG-ICP-MS). Sample solutions in 3.0 M HCl were mixed in line with a solution of 2.4% NaBH4 and 0.25 M KOH to generate stannane gas. The mixture was delivered continuously to a gas/liquid separator and the stannane gas was introduced into a Perkin-Elmer Sciex Elan 6000 ICP-MS for concentration measurements. A method detection limit of 0.45 mg/kg was sufficient for Sn levels commonly found in soil samples. Sn concentrations as low as 2.5 mg/kg were reproducibly measured in soil samples. Sample results by HG-ICP-MS agreed within ±17% relative difference to results by instrumental neutron activation analysis (INAA) and within ±6% relative difference to results by KOH fusion followed by inductively coupled plasma optical emission spectroscopy (ICP-OES). 相似文献
83.
C. Damas M. Adibnejad A. Benjelloun A. Brembilla M. C. Carré M. L. Viriot P. Lochon 《Colloid and polymer science》1997,275(4):364-371
Cationic amphiphilic polymers (e.g. polyvinylpyridinium bromides and polyvinylimidazo-lium bromides) adopt a compact coiled
form in aqueous solutions. In the case of former polymers, the resulting hydrophobic microdomains are evidenced only by fluorescence
spectroscopy if a molecular rotor (DMAC) is used as a fluorescent probe, while the behaviour of the latter can be studied
in aqueous solution by using both types of fluorescent probes, i.e., pyrene and the molecular rotor. The purpose of the present
investigation deals with a comparative study between the magnitude of the local viscosity and the polarity of the hydrophobic
microdomains generated by poly(3-hexadecyl-1-vinylimidazolium bromide) in an aqueous medium using pyrene and DMAC as fluorescent
probes. Moreover, the results are compared with the data obtained with micelles of conventional surfactants such as the homopolymer
repetitive unit model and CTAB.
Received: 3 June 1996 Accepted: 29 September 1996 相似文献
84.
Summary Salts of the anions [SnX5]–, [SnX4Cl, [SnX3Cl2]–, [SnX3]–, [PbX3]–, [SbX4]–, [SbX3Cl]–, [SbX2Cl2]–, [BiX4]–, [AuCl2]–, [AuX2]–, [AuXCl]–, [AuX4]–, [Au2X6]2– and [PtX4]2–, where X– = C6F5S–, have been isolated and characterised. The neutral SbX3 and BiX3 species, have also been isolated and shown to be pyramidal monomers (19F.n.m.r., i.r., and Raman spectral evidence). Various physical properties of the complexes prepared, as well as their stereochemistries (where these could be ascertained), are similar to those of the known corresponding halogeno compounds of these elements. These results further demonstrate the pseudo-halide nature of the pentafluorothiophenoxide ion.Author to whom all correspondence should be directed at: Laboratoire de Chimie de Coordination, Uniyersité Louis Pasteur, 67008 Strasbourg, France. 相似文献
85.
Ernesto Carmona Jose M. Marin Manuel L. Poveda Robin D. Rogers Jerry L. Atwood 《Journal of organometallic chemistry》1982,238(4):C63-C66
The reduction of [WCl4(PMe3)3] with dispersed sodium, under dinitrogen, gives cis-[W(N2)2(PMe3)4], while under ethylene trans-[W(C2H4)2(PMe3)4] is obtained. The ethylene complex can also be prepared by displacement of the dinitrogen molecules in cis-[W(N2)2(PMe3)4] by ethylene at room temperature and pressure. Interaction of cis-[M(N2)2(PMe3)4] complexes (M = Mo, W), with PMe3, under helium or argon, yields [M(N2)(PMe3)5]. The molybdenum complex crystallizes in the orthorhombic space group Pnma, with a 22.063(6), b 12.106(4), c 9.745(4) Å. The Mo—P distance trans to the dinitrogen ligand (2.483(7) Å) is slightly longer than the average of the other four Mo—P bonds (2.460(5) Å). 相似文献
86.
The phenomenon of enthalpy-entropy compensation in gas chromatography is examined. Using 53 probe solutes that span a wide range in size (dispersive interaction), dipolarity, hydrogen-bond-donor and hydrogen-bond-acceptor strength, enthalpy-entropy compensation is not observed, while for probe solutes within a homologous series enthalpy-entropy compensation is observed as predicted by the linear salvation energy relationship methodology. 相似文献
87.
Roberto Dallocchio Barbara Sechi Alessandro Dessì Bezhan Chankvetadze Sergio Cossu Victor Mamane Robin Weiss Patrick Pale Paola Peluso 《Electrophoresis》2021,42(17-18):1853-1863
2’-(4-Pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs (TCIBP = 3,3’,5,5’-tetrachloro-2-iodo-4,4’-bipyridyl) are chiral compounds that showed interesting inhibition activity against transthyretin fibrillation in vitro. We became interested in their enantioseparation since we noticed that the M-stereoisomer is more effective than the P-enantiomer. Based thereon, we recently reported the enantioseparation of 2’-substituted TCIBP derivatives with amylose-based chiral columns. Following this study, herein we describe the comparative enantioseparation of both 2’-(4-pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs on four cellulose phenylcarbamate-based chiral columns aiming to explore the effect of the polymer backbone, as well as the nature and position of substituents on the side groups on the enantioseparability of these compounds. In the frame of this project, the impact of subtle variations of analyte and polysaccharide structures, and mobile phase (MP) polarity on retention and selectivity was evaluated. The effect of temperature on retention and selectivity was also considered, and overall thermodynamic parameters associated with the analyte adsorption onto the CSP surface were derived from van ’t Hoff plots. Interesting cases of enantiomer elution order (EEO) reversal were observed. In particular, the EEO was shown to be dependent on polysaccharide backbone, the elution sequence of the two analytes being P-M and M-P on cellulose and amylose tris(3,5-dimethylphenylcarbamate), respectively. In this regard, a theoretical investigation based on molecular dynamics (MD) simulations was performed by using amylose and cellulose tris(3,5-dimethylphenylcarbamate) nonamers as virtual models of the polysaccharide-based selectors. This exploration at the molecular level shed light on the origin of the enantiodiscrimination processes. 相似文献
88.
An analytical study on the use of graphite-epoxy composite (GEC) electrodes for differential pulse anodic stripping voltammetry (DPASV) of heavy metals is presented. This study is accompanied by microscopic observations of the electrode surface before and after the stripping step in comparison to glassy carbon electrode. GEC electrodes show much better accumulation properties and consequently acceptable behaviour which makes them suitable as working electrodes in the DPASV of heavy metals. Lead determination in real water samples in a batch system as well as some preliminary results in a flow-through system are presented. The detection limits in batch measurements were 100ppb for Cd, 10pb for lead and 50ppb for copper. The detection limit for lead in the flow-through system was similar to that in the batch. The results obtained show that these low cost and easy to prepare materials can be of interest in future research concerning stripping techniques of heavy metals and other analytes. 相似文献
89.
Robin D. Rogers Philip D. Richards 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):631-638
The title complex was crystallized from a saturated solution of 18-crown-6 in nitromethane at 5°C and cooled to –150°C prior to X-ray diffraction data collection. At –150° C 18-crown-6·2(CH3NO2) is monoclinic,P21/n witha=9.290(2),b=7.864(6),c=13.627(8) Å, =1000.84(4)° andD
calc=1.31 g cm–3 for Z=2. Leastsquares refinement using 1521 independent observed reflections [F
o5(F
o)] led to a final conventionalR value of 0.041. The complex at –150°C is isostructural with its room temperature structure with the exception of the orientation of the methyl hydrogen atoms and their crown ether oxygen interactions. The methyl group hydrogen atoms were fully refined isotropically. The crown ether resides around a center of inversion and hasD
3d symmetry. There is one methyl hydrogen...crown interaction at 2.35(3) Å, one apparently bifurcated hydrogen bond utilizing a second methyl hydrogen atom (2.55(3), 2.65(3) Å) and the third hydrogen atom is actually directed away from the crown ring (closest H...O contact=2.67(3) Å).
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82048 (5 pages).For part 2, see reference [24]. 相似文献
90.
Robin D. Clark 《Journal of heterocyclic chemistry》1983,20(5):1393-1395
N-substituted 4-(2-morpholinyl)indoles were prepared from 1-(t-butoxycarbonyl)-4-acetylindole (7) which was itself prepared from 4-cyanoindole. Bromination of ketone 7, followed by reaction with amines and subsequent sodium borohydride reduction, gave amino alcohols. These were converted to α-chloro amides that were cyclized to lactams. Lithium aluminum hydride reduction served both to remove the t-BOC protecting group and to reduce the lactams to the 4-(2-morpholinyl) indoles. 相似文献