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排序方式: 共有603条查询结果,搜索用时 15 毫秒
151.
Cristina Molleda José A. García-Vazquez M. Antonia Mendiola José R. Masaguer 《Transition Metal Chemistry》1987,12(5):389-393
Summary
N-(o-hydroxybenzylidene)-2-aminobenzimidazole (HL) andN-(o-hydroxybenzylidene)-2(2-aminophenyl)benzimidazole (HL) react with CoX2 (X=Cl, Br, or NCS) and FeCl3 yielding complexes of general formulae [Co(HL)2X2], [Co(HL)2X2], [FeCl2(HL)2] [FeCl4], and [FeCl2(HL)2][FeCl4]. Moreover, it was possible to isolate the complexes [Co(HL)Br2] [Co(L)Cl] and [Co(L)Cl]. The complexes were characterized by elemental analyses, i.r. and electronic spectroscopies and conductivity and magnetic measurements at different temperatures. 相似文献
152.
M. Antonia Maj Abdelilah Alla Jordi J. Bou Concepcin Herranz Sebastin Muoz-Guerra 《European Polymer Journal》2004,40(12):2699-2708
Two sets of AA · BB-type polyamides (PLyTA) were synthesized from natural compounds L-lysine and D- or L-tartaric acid via the active ester polycondensation method. The carboxyl and hydroxyl side groups were orthogonally protected as methyl ester and methyl ether, respectively. Direct reaction of methyl L-lysinate dihydrochloride with bis(pentachlorophenyl) di-O-methyl tartaric acid led to the aregic polyamide ar-PLyTA, whereas isoregic (ir-PLyTA) and syndioregic (sr-PLyTA) polyamides were obtained by polycondensation of specifically designed amide–aminoacid and amide–diamine monomeric precursors, respectively. These polyamides have intrinsic viscosities in the 0.50–0.76 dl g−1 range, display optical activity, and are readily soluble in chloroform. They start to decompose well above 200 °C and display glass-transition temperatures at 100–105 °C. DSC and X-ray diffraction results indicated that these polyamides are not crystalline but they seem to adopt a partially ordered phase. No differences in properties other than optical rotation were observed between PLyTA made of D- and L-tartaric acid. 相似文献
153.
Antonia Zaprjanowa D. Trendafelov M. Semerdschiewa 《Monatshefte für Chemie / Chemical Monthly》1972,103(1):229-233
Zusammenfassung Mittels physikalisch-chemischer Analyse wurde das System K4Fe(CN)6/KOH/H2O untersucht. Es wurde gezeigt, daß bei 30° bzw. 40°C KOH stark aussalzend auf die Kaliumeisen(II)-cyanidlösungen wirkt, wobei die feste Gleichgewichtsphase nicht dehydratisiert wird, sondern als K4Fe(CN)6·3H2O erhalten bleibt. In der Isotherme bei 60°C bleibt die feste Phase — bis zur KOH-Konzentration 15% — K4Fe(CN)6·3H2O. Über diese Konzentration hinaus tritt Entwässerung ein und die feste Phase stellt K4Fe(CN)6 dar. Es wurde festgestellt, daß die Eisen(II)-cyanwasserstoffsäure (in kleinen Konzentrationen) die Löslichkeit des Kaliumeisen(II)-cyanids erhöht.
Mit 4 Abbildungen 相似文献
Investigation of the salting out and dehydratation effect of potassium hydroxide upon solutions of K4Fe(CN)6
The system K4Fe(CN)6/KOH/H2O was investigated by means of physico-chemical analysis. It was shown that at 30° and 40°C KOH has a strong salting out effect upon the solutions of K4Fe(CN)6, but the equilibrium solid phase is not dehydrated and remains K4Fe(CN)6·3H2O. In the isotherm at 60°C the solid phase remains K4Fe(CN)6·3H2O up to a concentration of 15% KOH. Beyond this concentration dehydration occurs and the solid phase represents K4Fe(CN)6. It was found that H4Fe(CN)6 acid (in small concentrations) increases the solubility of K4Fe(CN)6.
Mit 4 Abbildungen 相似文献
154.
Francia F Giachini L Palazzo G Mallardi A Boscherini F Venturoli G 《Bioelectrochemistry (Amsterdam, Netherlands)》2004,63(1-2):73-77
The coupling between electron transfer and protein dynamics has been studied at room temperature in isolated reaction centers (RCs) from the photosynthetic bacterium Rhodobacter sphaeroides by incorporating the protein in polyvinyl alcohol (PVA) films of different water/RC ratios. The kinetic analysis of charge recombination shows that dehydration of RC-containing PVA films causes reversible, inhomogeneous inhibition of electron transfer from the reduced primary quinone acceptor (Q(A)(-)) to the secondary quinone Q(B). A more extensive dehydration of solid PVA matrices accelerates electron transfer from Q(A)(-) to the primary photooxidized electron donor P(+). These effects indicate that incorporation of RCs into dehydrated PVA films hinders the conformational dynamics gating Q(A)(-) to Q(B) electron transfer at room temperature and slows down protein relaxation which stabilizes the primary charge-separated state P(+)Q(A)(-). A comparison with analogous effects observed in trehalose-coated RCs suggests that protein motions are less severely reduced in PVA films than in trehalose matrices at comparable water/RC ratios. 相似文献
155.
Bonadio F Senna MC Ensling J Sieber A Neels A Stoeckli-Evans H Decurtins S 《Inorganic chemistry》2005,44(4):969-978
Reactions between the complex [MnII(L)]2+, where L is a N3O2 macrocyclic ligand, and different cyanometalate precursors such as [M(CN)n]m- (M(III) = Cr, Fe; M(II) = Fe, Ni, Pd, Pt) lead to cyano-bridged molecular assemblies exhibiting a variety of structural topologies. The reaction between [MnII(L)]2+ and [FeII(CN)6]4- forms a trinuclear complex with formula [(MnII(L)(H2O))2(FeII(micro-CN)2(CN)4)] x 2MeOH x 10H2O (1) which crystallizes in the triclinic space group P1. The reaction between [MnII(L)]2+ and [M(II)(CN)4]2-, where M(II) = Ni (2), Pd (3), Pt (4), gives rise to three isostructural linear chain compounds with stoichiometry [(MnII(L))(M(II)(micro-CN)2(CN)2)]n and which crystallize in the monoclinic space group C2/c. The self-assembly between [MnII(L)]2+ with [M(III)(CN)6]3-, where M(III) = Cr (5), Fe (6, 7, 8), forms three types of compounds. Compounds 5 and 6 are isostructural (monoclinic, space group P2(1)/n), and the structures comprise anionic linear chains [(MnII(L))(M(III)(micro-CN)2(CN)4)]n(n-) with cationic trinuclear complexes [(MnII(L)(H2O))2(M(III)(micro-CN)2(CN)4)]+ as counterions. Using an excess of K3[FeIII(CN)6], an analogous compound to 6 but with K+ as counterion is obtained (7), which crystallizes in the triclinic space group P1. Compound 8 consists of 2-D layers with formula [(MnII(L))3(FeIII(micro-CN)4(CN)2)(FeIII(micro-CN)2(CN)4)]n x 2nMeOH; it crystallizes in the monoclinic space group P2(1)/n. The magnetic properties were investigated for all samples. In particular, compound 5, which shows antiferromagnetic exchange interactions between Mn(II) and Cr(III) ions through cyanide bridging ligands, has been studied in detail; the magnetic exchange parameter amounts to J = -7.5(7) cm(-1). Compound 8 shows a magnetically ordered phase below 6.4 K which is confirmed by M?ssbauer spectroscopy; two hyperfine split spectra were observed below Tc from which IJI values of 2.1 and 1.6 cm(-1) could be deduced. 相似文献
156.
Moreno Frías M Jiménez Torres M Garrido Frenich A Martínez Vidal JL Olea-Serrano F Olea N 《Biomedical chromatography : BMC》2004,18(2):102-111
A study was undertaken to determine the extent of organochlorine pesticide (OP) and polychlorinated biphenyl (PCB) contamination in infant formula milk and in the human milk, fat and serum of women from an agricultural area in Southern Spain. A procedure is proposed that simultaneously detects trace levels of lindane, endosulfan-ether, vinclozolin, aldrin, endosulfan-lactone, endosulfan-alpha, 4,4'DDE, 2,4'DDT, endosulfan-beta, 4,4'DDT, kepone, endosulfate-sulfate, methoxychlor, mirex, 2,3,4 PCB, 2,2',4,5 PCB, 2,3,4,5 PCB and 2,2',3,3',6,6'PCB. After liquid-liquid or solid-liquid extraction, the extract of the sample was cleaned by high performance liquid chromatography (HPLC) and the fi rst eluted fraction was analysed by gas chromatography (GC) with mass spectrometry (MS) detector in tandem mode. To evaluate the validity of the method the following parameters were studied: linearity, detection limits, quantification limits, specificity, percentage recovery and precision. A study of the uncertainty associated with the analytical method was also carried out. 相似文献
157.
Bradley AE Hatter JE Nieuwenhuyzen M Pitner WR Seddon KR Thied RC 《Inorganic chemistry》2002,41(7):1692-1694
The novel complex 1-butyl-3-methylimidazolium mu(4)-(O,O,O',O'-ethane-1,2-dioato)-bis[bis(nitrato-O,O)dioxouranate(VI)] (1) has been precipitated from a room-temperature ionic liquid medium containing 1-butyl-3-methylimidazolium nitrate, nitric acid, and acetone. X-ray analysis of complex 1 shows the unit cell contains four [C(4)mim](+) cations and two independent [[UO(2))(NO(3))(2)](2)(mu(4)-C(2)O(4))](2-) moieties, both of which are located about inversion centers. The [C(4)mim](+) cations are arranged such that they produce large channels in which the anions are located. This arrangement of [[(UO(2))(NO(3))(2)](2)(mu(4)-C(2)O(4))](2-) groups is unique to this compound. Crystal data for compound 1: M = 1154.56, monoclinic, space group P2(1)/c, a = 15.452(2) A, b = 20.354(3) A, c = 10.822(4) A, beta = 106.84(2) degrees, U = 3258(1) A(-)(3), Z = 4, mu = 10.023 mm(-1), R(int) = 0.0788. 相似文献
158.
Urinary concentrations of phenols or their metabolites have been used as biomarkers to assess the prevalence of exposure to
these compounds in the general population. Total urinary concentrations, which include both free and conjugated (glucuronide
and sulfated) forms of the compounds, are usually reported. From a toxicologic standpoint, the relative concentrations of
the free species compared with their conjugated analogs can be important because conjugation may reduce the potential biologic
activity of the phenols. In this study, we determined the percentage of glucuronide and sulfate conjugates of three phenolic
compounds, bisphenol A (BPA), 2,5-dichlorophenol (2,5-DCP), and 2-hydroxy-4-methoxybenzophenone (benzophenone-3, BP-3) in
30 urine samples collected between 2000 and 2004 from a demographically diverse group of anonymous adult volunteers. We used
a sensitive on-line solid phase extraction–isotope dilution–high performance liquid chromatography–tandem mass spectrometry
method. These three phenols were detected frequently in the urine samples tested. Only small percentages of the compounds
(9.5% for BPA, and 3% for 2,5-DCP and BP-3) were excreted in their free form. The percentage of the sulfate conjugate was
about twice that of the free compound. The glucuronide conjugate was the major metabolite, representing 69.5% (BPA), 89% (2,5-DCP),
and 84.6% (BP-3) of the total amount excreted in urine. These results are in agreement with those reported before which suggested
that BPA-glucuronide was an important BPA urinary metabolite in humans. To our knowledge, this is the first study describing
the distribution of urinary conjugates of BP-3 and 2,5-DCP in humans. 相似文献
159.
Surface roughness effects in turbulent boundary layers 总被引:7,自引:7,他引:0
The effects of surface roughness on a turbulent boundary layer are investigated by comparing measurements over two rough
walls with measurements from a smooth wall boundary layer. The two rough surfaces have very different surface geometries although
designed to produce the same roughness function, i.e. to have nominally the same effect on the mean velocity profile. Different
turbulent transport characteristics are observed for the rough surfaces. Substantial effects on the stresses occur throughout
the layer showing that the roughness effects are not confined to the wall region. The turbulent energy production and the
turbulent diffusion are significantly different between the two rough surfaces, the diffusion having opposite sign in the
region γ/δ < 0.5. Although velocity spectra exhibit differences between the three surfaces, the mean energy dissipation rate
does not appear to be significantly affected by the roughness.
Received: 19 August 1998/Accepted: 16 February 1999 相似文献
160.
Georg Süss-Fink Susanne Haak Vincent Ferrand Antonia Neels Helen Stoeckli-Evans 《Journal of organometallic chemistry》1999,580(2):371
The reaction of the mixed-metal carbonyl cluster anion [H2Ru3Ir(CO)12]− with PPh3, PMe3, P(OPh)3, AsPh3 or SbPh3 leads to the mono-substituted derivatives [H2Ru3Ir(CO)11L]− (L=PPh3 1, L=PMe3 2, L=P(OPh)3 3, L=AsPh3 4, L=SbPh3 5). Protonation of the anions 1–5 gives the neutral trihydrido derivatives H3Ru3Ir(CO)11L (L=PPh3 6, L=PMe3 7, L=P(OPh)3 8, L=AsPh3 9, L=SbPh3 10). All new tetranuclear clusters invariably show a tetrahedral arrangement of the Ru3Ir skeleton, as predicted for 60 e systems. The ligand L is coordinated to one of the ruthenium atoms, except in the case of L=PMe3 where two substitution isomers are observed. While the anionic isomers [H2Ru3Ir(CO)11(PMe3)]− (2) could not be separated, the corresponding neutral isomers H3Ru3Ir(CO)11(PMe3) (7) could be resolved by thin-layer chromatography. In isomer 7a, the phosphine ligand is coordinated to one of the ruthenium atoms, whereas in isomer 7b the PMe3 ligand is bonded to the iridium atom. The molecular structures of 1, 7b, 8 and 9 were confirmed by a single-crystal X-ray structure analysis. 相似文献