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排序方式: 共有440条查询结果,搜索用时 31 毫秒
431.
《Journal of Coordination Chemistry》2012,65(3-4):191-195
Abstract A direct method of obtaining PbEnI2.DMSO is reported. The crystal structure of the compound was determined by X-ray techniques. PbEnI2.DMSO is triclinic, space group P 1, C4H14I2N2PbS, a=10.225(3), b=10.132(3), c=6.900(2) Å; α=90.83(2), β=88.30(2), γ=106.35(4)°; V=685.6(4) Å3; z=2, calculated density 2.92 gcm?3. Neutral PbEnI2 complexes are associated with DMSO molecules via H-bonds. The lead(II) ion is covalently linked with a chelated En molecule (Pb-N 2.46–2.48 Å) and I? anions (Pb-I 3.087–3.343 Å). Covalently bonded atoms form an umbrella-like coordination Pb(II) polyhedron. The side containing the lone electron pair of the lead(II) ion has coordination completed by two I? anions of neighbouring molecules with the Pb-I 3.621–3.627 Å. 相似文献
432.
The formation of multiple molecular ions, especially due to sodium adduct ion formation, is commonly observed in electrospray mass spectrometry and may make reproducible and sensitive quantitation difficult. The objective of this work was to investigate the underlying mechanism involved in the suppression of multiple molecular ion formation and to improve the sensitivity of detection for the two anti-neoplastic agents paclitaxel and docetaxel. The results showed that alkylamine additives could significantly improve the detection of paclitaxel and docetaxel by suppression of multiple molecular ions through preferential formation of a predominant alkylamine adduct ion. Possible binding sites, binding interactions and binding competition were investigated for the sodium adduct and alkylamine adduct ions using various experimental techniques. The formation of a predominant amine adduct ion may be due to increased surface activity in the droplet. The optimal alkylamine for both analytes was octylamine, which increased peak heights of paclitaxel and docetaxel 4.8 and 3.7-fold (n = 3), respectively. The precision of the signals for the analytes was also improved 5.7-fold. A quantitative assay in plasma for paclitaxel was partially validated for the calibration range 1.0-1000 ng/mL (r = 0.9977) when using 0.05% octylamine as a reconstitution solution additive. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.5 and 0.9 ng/mL, respectively. Acceptable precision, accuracy, specificity and sample stability were demonstrated for this assay. This approach may prove useful for other analytes with similar binding sites. 相似文献
433.
Determination of BAPTA-AM, the acetoxymethyl tetraester of BAPTA, in rat plasma by liquid chromatography tandem mass spectrometry 总被引:1,自引:0,他引:1
Zheng F Hang T Wu C Di B Liu W Xu J Zhai C Sun D Liu J Wei W 《Journal of mass spectrometry : JMS》2006,41(12):1615-1622
BAPTA-AM is the acetoxymethylester of the calcium chelator BAPTA and has demonstrated efficacy in several animal models of cerebral ischemia. This paper describes the development of a method for the determination of BAPTA-AM in rat plasma by liquid chromatography/tandem mass spectrometry. Owing to multiple ester groups in the structure of BAPTA-AM, [M + Na](+) was chosen as the analytical ion for quantification of BAPTA-AM. During the analytical method development, a high percentage of organic solvent and the addition of an amount of sodium acetate and formic acid in the mobile phase were found to favor the sensitivity and reproducibility of [M + Na](+). Poor fragmentation was usually observed in the MS/MS spectra of sodium adduct ions. However, abundant and reproducible fragment ions were observed for the BAPTA-AM sodium adduct ion, and therefore the traditional selective reaction-monitoring mode was used to further improve the sensitivity of MS detection. Because of the lability of the ester bond, a combination of fluoride and hydrochloric acid was applied to minimize the enzymatic hydrolysis, and acetonitrile was chosen to avoid the chemical hydrolysis or solvolysis during the sample collection and preparation procedure. On the basis of these studies, a rapid, sensitive and reproducible method for the determination of BAPTA-AM in rat plasma, using LC/ESI-MS/MS and a simple protein precipitation procedure, was developed and validated. Also, the present method was successfully applied to the determination of BAPTA-AM plasma concentrations for pharmacokinetic studies in rats. 相似文献
434.
The synthesis of quinolones from Morita-Baylis-Hillman (MBH) adducts is reported. The quinolone skeleton is formed via a TFA-mediated cyclization of the MBH adduct, and a mechanism study using ESI(+)-MS(/MS) has indicated the role played by TFA in this key reaction step. The total syntheses of Norfloxacin and a benzyl quinolone carboxylic acid (BQCA) derivative are described. Norfloxacin is a fluoroquinolonic antibacterial drug whereas BQCA is M1 receptor positive allosteric modulator and seem to provide access to new potential drugs for Alzheimer disease, pain, and sleep disorders. The syntheses of these two important quinolones exemplify the versatility and potentiality of the approach. 相似文献
435.
Subhasish Biswas 《Tetrahedron》2010,66(39):7781-7786
DABCO-mediated Morita-Baylis-Hillman reactions of several 1-substituted-indole-2-carboxaldehydes are disclosed. It was discovered that carboethoxy or tert-butoxycarbonyl groups installed at N-1 undergo cleavage under the reaction conditions to afford 2-substituted indoles. Utility of the N-substituted adducts for preparing a variety of annulated indoles has been exemplified. 相似文献
436.
A ternary adduct Cu[S2P(OCH2CH2Ph)2]2·bipy(bipy=α,α'-bipyridine) was syn-thesized and characterized by elemental analysis,IR and single-crystal X-ray diffraction.The crystal belongs to the triclinic system,space group P1 with a=10.2320(2),b=11.5249(3),c=18.0916(3),α=98.95(1),β =103.601(1),γ=91.272(2)°,V=2044.49(7)3,Z=2,Dc=1.453 g/cm3,T=153(2) K,C42H44CuN2O4P2S4,Mr=894.51,λ(MoKα)=0.71073,μ=0.86 mm-1,S=0.999,(△/σ)max=0.002,the final R=0.0243 and wR=0.0704.A total of 9221 unique reflections were collected,of which 8573 with Ⅰ 2σ(Ⅰ) were observed.The Cu(Ⅱ) atom is five-coordinated in a rather distorted trigonal bipyramidal geometry(τ value=0.537).The Cu-S distances range from 2.3491(4) to 2.4829(4) ,and the Cu-N distances are 1.9987(12) and 2.0584(11) ,respectively.An interesting feature of this adduct resides in its two-dimensional(2D) open framework constructing through hydrogen bonding and π-π interactions. 相似文献
437.
Sebastiano Mantovani Angela Pintus Dr. Alessandro Kovtun Dr. Giulio Bertuzzi Dr. Manuela Melucci Prof. Marco Bandini 《European journal of organic chemistry》2023,26(37):e202300641
A new metal-free synthetic approach to functionalized indenes is documented. The use of commercially available graphene oxide (GO) allowed the direct access to indenyl cores (yield up to 80 %) via intramolecular Friedel-Crafts-type allylic alkylations with readily available Morita-Baylis-Hillman alcohols. Combined experimental and spectroscopic investigations contributed to shed light on the reaction mechanism dealing with a nanostructured carbon material-based C−C bond forming reaction. 相似文献
438.
《Mendeleev Communications》2023,33(1):9-10
Diels–Alder adducts of levoglucosenone with isoprene, butadiene and piperylene in the presence of AlCl3 smoothly react with acetaldehyde or benzaldehyde to give products of the ene reaction, the hydroxy group of the primary intermediates participating in the formation of semiketal moiety. The yields of the reaction products depend both on the Lewis acid used (AlCl , BF ·Et O, ZnBr , SnCl or EtAlCl2) and on the nature of the substrate. 相似文献
439.
制备44连吡啶基二卤加和物MX244′bipyn仍然有较大困难。这类化合物数量不多且已报道的多为难处理的微晶材料。本文在室温下通过简单的操作合成了新的碘化汞连吡啶乙烷加和物HgI2bpean。X射线单晶衍射分析表明其中的汞原子通过与两个碘原子以及吡啶乙烷的两个氮原子配位形成扭曲的四面体构型。每个HgI2单元由bpea桥连形成锯齿状链。其非线性光学性质用8纳秒激光在532nm波长进行了研究。该化合物相对于入射光表现为一定的光学吸收和强的自聚焦效应,其三阶非线性吸收系数α2=1.1×10-11m·W-1折射系数n2=5.29×10-18m2·W-1。 相似文献
440.
Samantha A. Ranaweera Bruno Donnadieu William P. Henry Mark G. White 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(4):142-148
The stepwise addition of Cu2+ ions to the nonplanar cyclic Schiff base 5,9,14,18-tetramethyl-1,4,10,13-tetraazacyclooctadeca-5,8,14,17-tetraene-7,16-dione (H4daaden, C18H28N4O2), yields a one-end-open dinuclear copper chelate. The pyridine adduct of the dinuclear copper chelate, namely, [μ-6,11-dimethyl-7,10-diazahexadeca-5,11-diene-2,4,13,15-tetraolato(4−)](pyridine)dicopper(II), [Cu2(C16H20N2O4)(C5H5N)], was characterized by single-crystal X-ray crystallography. The two CuII atoms of the copper chelate display different coordination modes, i.e. inner-N2O2 and outer-O2O2. The Cu atom which is bonded in the outer-O2O2 mode is axially bonded to a pyridine molecule, which suggests that the electron-donating ability of the O2O2 site to the Cu atom is poor. As a result, the O2O2-bonded Cu atom has a coordination number of five, showing square-bipyramidal geometry around the Cu atom. The N2O2-coordinated site provides sufficient electron density to the other Cu atom to be stabilized with a coordination number of four, showing square-planar geometry around the Cu atom. The electron-donating ability of the ligand coordination sites plays a key role in determining the coordination number of the Cu atoms of the dicopper chelate. 相似文献