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81.
The complexes Ru(L1-CH3)(CO)3Cl, RuL2(CO)2Cl2, and RuL3(CO)2Cl2 (L1= 6-methoxy-5,8-quinolinedione, L2 = 7-amino-6-methoxy-5,8-quinolinedione, L3 = 6,6'-dimethoxycarbonyl-2,2'-bipyridine) were prepared by reaction of L1-L3 with the tricarbonyldichlororuthenium(II) dimer. L1-L3 act as bidentates through the ortho oxygen atoms, the pyridyl nitrogen and the adjacent quinone oxygen, and the bipyridyl nitrogens, respectively. RuL3(CO)2Cl2 is characterized by X-ray crystallography. 15N NMR correlation spectra give upfield shifts of around 60 ppm for the pyridyl nitrogens that are coordinated to the metal, while 13C NMR correlation spectra give a downfield shift of 10 ppm for the quinone carbonyl group that is coordinated to the metal. The electrochemistry of RuL2(CO)2Cl2 is examined, and the implications for the formation of metal complexes of the antitumor antibiotic streptonigrin, which cleaves DNA in the presence of metal ions, are discussed. 相似文献
82.
Lisheng Chi Ian Swainson Jae-Hyuk Her Osvald Knop 《Journal of solid state chemistry》2005,178(5):1376-1385
The perovskite-structured compound methylammonium lead chloride orders into a low-temperature phase of space group Pnma, in which at 80 K each of the orthorhombic axes , and is doubled with respect to the room temperature disordered cubic phase (). The structure was solved by ab initio methods using the programs EXPO and FOX. This unusual cell basis for space group Pnma is not that of a standard tilt system. This phase, in which the methylammonium ions, are ordered shows distorted octahedra. The octahedra possess a bond angle variance of 60.663°2 and a quadratic elongation of 1.018, and are more distorted than those in the ordered phase of methylammonium lead bromide. There is also an alternating long and short Pb-Cl bond along a, due to an off-center displacement of Pb within the octahedron. This suggests that the most rigid unit is actually the methylammonium cation, rather than the PbCl6 octahedra, in agreement with existing spectroscopic data. 相似文献
83.
Streeter I Wain AJ Thompson M Compton RG 《The journal of physical chemistry. B》2005,109(25):12636-12649
An in situ electrochemical electron spin resonance (ESR) study on the electro-oxidation of para-chloroaniline, para-bromoaniline, and para-iodoaniline dissolved in acetonitrile at gold electrodes is reported. ESR spectra obtained using a tubular flow cell reveal the presence of a paramagnetic dimer product derived from para-aminodiphenylamine, during oxidative electrolysis, suggesting the coupling of reactive electrogenerated radical cations with neutral parent haloaniline molecules. The ESR signal intensity behaves in a manner expected for a radical species reacting with second-order kinetics, suggesting the paramagnetic dimer is, itself, unstable. The theory describing the ESR signal intensity flow rate behavior for this reaction mechanism is developed for the tubular arrangement and used to extract mechanistic and kinetic data from the experimental results for the cases of para-chloroaniline and para-bromoaniline. Further mechanistic aspects, including proton and halide ion expulsion during dimerization, are explored voltammetrically and with the aid of digital simulations using Digisim. Comparison of the ESR signal and voltammetric measurements suggests that an additional mechanism operates which does not lead to paramagnetic products. Additionally, the in situ electrolysis of N,N-dimethyl-para-bromoaniline is reported to generate the stable radical cation of N,N,N',N'-tetramethylbenzidine, and a mechanism of electro-oxidation is, thus, proposed. 相似文献
84.
James A. Ballantine Jonathan D. Barton James F. Carter Jeremy P. Davies Keith Smith Geoffrey Stedman Eric E. Kingston 《Journal of mass spectrometry : JMS》1988,23(1):1-5
The mass spectra of a number of aliphatic nitro compounds have been studied using electron Ionization (EI) and a variety of chemical Ionization (CI) techniques in attempts to obtain relative molecular mass information. The use of positive ion ammonia chemical Ionization techniques gave very satisfactory results, providing abundant [M + NH4]+ ions, not only from both primary and secondary nitro compounds, but also from the much more labile tertiary nitro compounds. However, the use of methane and isobutane positive ion CI or EI conditions resulted in facile fragmentation with little relative molecular mass information being made available. Negative ion CI using methane, isobutane or ammonia as moderating gases all gave abundant [M ? 1]? ions with primary and secondary nitro compounds but at much reduced sensitivity. 相似文献
85.
Rosenthal SJ Tomlinson I Adkins EM Schroeter S Adams S Swafford L McBride J Wang Y DeFelice LJ Blakely RD 《Journal of the American Chemical Society》2002,124(17):4586-4594
To explore the potential for use of ligand-conjugated nanocrystals to target cell surface receptors, ion channels, and transporters, we explored the ability of serotonin-labeled CdSe nanocrystals (SNACs) to interact with antidepressant-sensitive, human and Drosophila serotonin transporters (hSERT, dSERT) expressed in HeLa and HEK-293 cells. Unlike unconjugated nanocrystals, SNACs were found to dose-dependently inhibit transport of radiolabeled serotonin by hSERT and dSERT, with an estimated half-maximal activity (EC(50)) of 33 (dSERT) and 99 microM (hSERT). When serotonin was conjugated to the nanocrystal through a linker arm (LSNACs), the EC(50) for hSERT was determined to be 115 microM. Electrophysiology measurements indicated that LSNACs did not elicit currents from the serotonin-3 (5HT(3)) receptor but did produce currents when exposed to the transporter, which are similar to those elicited by antagonists. Moreover, fluorescent LSNACs were found to label SERT-transfected cells but did not label either nontransfected cells or transfected cells coincubated with the high-affinity SERT antagonist paroxetine. These findings support further consideration of ligand-conjugated nanocrystals as versatile probes of membrane proteins in living cells. 相似文献
86.
RECOVERY OF Escherichia coli K-12 FROM NEAR-ULTRAVIOLET RADIATION-INDUCED MEMBRANE DAMAGE 总被引:2,自引:0,他引:2
Abstract A wild-type Escherichia coli K-12 strain was irradiated with broad-band near-ultraviolet radiation (from Black-Light Blue fluorescent lamps) and after holding at 37°C for various times in a complex recovery medium, was assessed for viability on either complex medium (YENB) or minimal medium containing a high inorganic salt content. A near-ultraviolet radiation fluence was used which reduced the surviving fraction to approximately 10% when assessing for viability on the complex medium plates. A near-ultraviolet radiation induced sensitivity to inorganic salt was observed which was largely recoverable by holding treated cells in a complex recovery medium. The majority of the recovery process occurred in the initial 2 h post-irradiation holding period. No inhibition of the recovery process was produced by adding chloramphenicol (40 μg/m l ) or penicillin G (11 units/m l ) to the recovery medium, indicating that neither protein synthesis nor cell wall synthesis, respectively, were required for recovery. However, by adding bacitracin, an antibiotic which acts in part by inhibiting membrane synthesis, to the recovery medium, an effect on recovery from salt sensitivity was observed. At the concentrations of bacitracin used (0.6 and 0.2 units/m l ), little or no effect was observed on unirradiated cells, but both concentrations decreased the amount of recovery of irradiated cells. These results demonstrate that recovery from near-ultraviolet radiation-induced salt sensitivity occurs, it is independent of cell growth and the effect of bacitracin suggests that membrane synthesis may be required for recovery. 相似文献
87.
Alwyn G. Davies Rajaveen Sivasubramaniam 《Journal of organometallic chemistry》2006,691(16):3556-3561
The thermolysis of the butyltin chlorides at 200-300 °C in the liquid phase has been investigated by 1H, 13C, and 119Sn NMR spectroscopy. The stabilities follow the order: Bu2SnCl2 > Bu3SnCl > BuSnCl3. Only tributyltin chloride showed any evidence of redistribution, giving dibutyltin dichloride, together with metallic tin, butane, and but-1-ene, which would be formed by decomposition of tetrabutyltin. Dibutyltin dichloride decomposed to give mainly butane with no other apparent liquid organotin compound. Butyltin trichloride gave butane, some butene, and metallic tin, and showed no evidence of forming tributyltin chloride by the redistribution reaction, which would have environmental implications for its use in the CVD coating of glass. 相似文献
88.
Blackmore IJ Gibson VC Hitchcock PB Rees CW Williams DJ White AJ 《Journal of the American Chemical Society》2005,127(16):6012-6020
The 2,6-bis(alpha-iminoalkyl)pyridines 2,6-[ArNC(CR(3))](2)C(5)H(3)N [R = H, D; Ar = 2,6-i-Pr(2)C(6)H(3) (DIPP), 2,6-Me(2)C(6)H(3) (DMP)] react with MeLi in Et(2)O to give a binary mixture of products: the pyridine N-methylated species 2,6-[ArNC(CR(3))](2)C(5)H(3)N(Me)Li(OEt(2)) and the deprotonated/dedeuterated species 2-[ArNC(CR(3))],6-[ArNC(=CR(2))]C(5)H(3)NLi(OEt(2)). For R = D, the product ratio is 2:1 in favor of the N-methylated product, while, for R = H, the deprotonated product is favored by 5:1, increasing to 8:1 in toluene solvent. Warming solutions of the N-methylated species leads to clean conversion to the thermodynamically preferred deprotonated species. Crossover experiments show that MeLi is re-formed and dissociates from the terdentate ligand before deprotonating the ketimine methyl unit. For MgR(2) (R = Et, i-Pr) and ZnR(2) (R = Et) reagents, N-alkylation products are formed exclusively, but derivatives containing bulky aryl substituents are found to undergo further rearrangement to 2-alkylated species, arising by migration of the alkyl group of the N-alkyl moiety to the adjacent ring carbon atom. The reversibility of the N-alkylation process has been probed using deuterio-labeled Mg alkyl reagents and mixed alkyl zinc species. A cationic zinc derivative is shown to undergo "reverse" alkyl migration, from the heterocycle nitrogen atom to the zinc center. EPR spectroscopy reveals a paramagnetic intermediate in which the unpaired electron is delocalized over the heterocycle and di-imine moieties of the ligand, indicating that the N-alkylation reactions proceed via single electron-transfer processes. 相似文献
89.
Surface passivation of luminescent colloidal quantum dots with poly(dimethylaminoethyl methacrylate) through a ligand exchange process 总被引:1,自引:0,他引:1
Wang XS Dykstra TE Salvador MR Manners I Scholes GD Winnik MA 《Journal of the American Chemical Society》2004,126(25):7784-7785
Polydimethylaminoethyl methacrylate (PDMAEMA) was used as a multidentate ligand to modify the surface of CdSe/ZnS core-shell colloidal quantum dots in toluene with trioctylphosphine oxide (TOPO) as the surface ligand. Adsorption of PDMAEMA was accompanied by release of TOPO. The process is free of agglomeration, and the modified nanocrystals become soluble in methanol. The photoluminescence properties are well-preserved in either toluene or methanol. 相似文献
90.
Abstract— Following UV irradiation at 254 nm and treatment with hot piperidine, single-stranded 49-mer and 12-mer oligodeoxyribonucleotides have been shown by gel-sequencing experiments to contain a prominent alkali-labile cleavage site that maps to adenine in the sequence element 5'-TTGATC-3'. This behavior is abolished by single base substitutions within the photoreactive tract and does not occur with duplex DNA. The distinctive properties of the photolesion are consistent with the formation of an abasic site through initial loss of a photomodified adenine base of unknown structure. The presence of an abasic site is supported by the observations that the alkaline cleavage fragments are terminally phosphorylated and that strand scission can also be effected by spermidine and the tripeptide Lys-Trp-Lys. 相似文献