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排序方式: 共有129条查询结果,搜索用时 15 毫秒
1.
Phelps T. J. Siegrist R. L. Korte N. E. Pickering D. A. Strong-Gunderson J. M. Palumbo A. V. Walker J. F. Morrissey C. M. Mackowski R. 《Applied biochemistry and biotechnology》1994,45(1):835-845
Applied Biochemistry and Biotechnology - Soil column studies were used to evaluate petroleum hydrocarbon (PHC) remediation in soils from Kwajalein Atoll. Treatments included controls, and... 相似文献
2.
It is apparent that, in electro-chromatographic separations, the change of area undergone by the initial spot of test solution plays a part in the final interpretation of results almost as important as the actual movement of the centre of the spot.Several interesting facts have emerged from this research concerning the role of the carrier electrolyte on tlie movement, the spot size, and the stability of complex salts. 相似文献
3.
The dithiocarbene complex W(CO)5[C(SCH3)2 reacts with tertiary phosphines, PPh2CH3, PPh(CH3)2, P(C2H5)3 and P(OCH3)3 to form the phosphorane complexes W(CO)5[CH3S)2C-PR3] and with HPPh2 to form the phosphine complex W(CO)5[PPh2[CH(SCH3)2]. Kinetic studies of both types of reactions show that their rates are first order each in W(CO)5[C(SCH3)2] and in the phosphorus ligand. A mechanism involving rate determining phosphorus attack at the carbene carbon followed by rapid rearrangement to the product is consistent with this rate law. Rate constants for the reactions increase with increasing nucleophilicities of the phosphines: P(OCH3)3 < PPh2H < PPh2CH3 ? PPh(CH3)2 < P(C2H5)3. The ΔH values decrease (P(OCH3)3 > PPh2H > PPh2(CH3) > PPh(CH3)2 > P(C2H5)3) as the nucleophilicities of the phosphines increase. The ΔS values (≈-30 e.u.) remain essentially constant for all the reactions. The cyclic dithiorcarbenes W(CO)5[CS(CH2)nS], wheren- 3 or 4, react with PPh2(CH3) to form the cyclic phosphorane complexes, W(CO)5[S(CH2)nSC-PPh2(CH3)]. The 6- and 7- membered cyclic dithiocarbenes also react with PPh2H to form the phosphine complexes, W(CO)5 {PPh2- [CS(CH2)nS(H)]}. 相似文献
4.
Abbas H Pickering AL Long DL Kögerler P Cronin L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(4):1071-1078
Molecular growth processes utilizing a beta-octamolybdate synthon and {Ag2} dimers are described and the directing influence of "encapsulating" cations and coordinating solvent is also demonstrated. The growth of two 1D chains, (nBu4N)2n[Ag2Mo8O26]n (1) and (nBu4N)2n[Ag2Mo8O26(CH3CN)2]n (2), is achieved when nBu4N+ ions are used, and the diameter of the chains can be expanded by the coordination of CH3CN solvent (2). The formation of a type of gridlike structure in which 1D chains are crossed-over each other in alternatively packed layers is achieved in DMSO as the solvent; DMSO acts as a linking group to give (nBu4N)2n[Ag2Mo8O26(dmso)2]n (3), which, similar to 1 and 2, still incorporates the Bu4N+ ions that exert an "encapsulating" influence. However, in (HDMF)n[Ag3(Mo8O26)(dmf)4]n (4) the relatively bulky Bu4N+ ions are exchanged for protonated DMF cations, thereby allowing the chains to condense to a 2D array. The building block concept is further enforced by the isolation of a "monomeric" unit (Ph4P)2[Ag2Mo8O26(dmso)4] (5), which is isolated when the Ph4P+ ions are so "encapsulating" as to prevent aggregation of the {Ag-Mo8-Ag} building blocks. The nature of the AgAg dimers in each of the compounds 1-4 is examined by DFT calculations and the interplay between these Ag-Ag interactions and the structure types is described. 相似文献
5.
Vogensen SB Greenwood JR Varming AR Brehm L Pickering DS Nielsen B Liljefors T Clausen RP Johansen TN Krogsgaard-Larsen P 《Organic & biomolecular chemistry》2004,2(2):206-213
(RS)-3-Hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid (5-HPCA)(), which is a conformationally constrained cyclised analogue of AMPA has previously been described as causing glutamate receptor mediated excitations of spontaneously firing cat spinal interneurons in a similar fashion to AMPA. We have now prepared the enantiomers of through chiral chromatographic resolution of (RS)-3-(carboxymethoxy)-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid () followed by a stereoconservative hydrolysis resulting in the enantiomers of with high enantiomeric excess (% ee [greater-than-or-equal] 99). The absolute configurations indicated by an X-ray analysis of (-)- monohydrate were confirmed by comparing observed and ab initio calculated electronic circular dichroism spectra and by stereoconservative synthesis of (S)- from (S)-AMPA, the pharmacologically active form of AMPA. The pharmacological effects at native and cloned (GluR1-4) AMPA receptors were shown to reside exclusively with (R)-(+)-, in striking contrast to the usual stereoselectivity trend among AMPA receptor agonists. The reasons for this anomalous behaviour became clear upon docking both enantiomers of to the agonist binding site of GluR2. 相似文献
6.
7.
The main objective of this study was to assess the effect of stearic acid vapour treatment on hemp fibre mats produced using dynamic sheet forming, and the potential use of these treated mats as reinforcement in polypropylene matrix composites. Stearic acid was successfully applied through vapour treatment, appearing to form a layer on fibre surfaces. It was found that the presence of stearic acid increased hydrophobicity and thermal stability of fibre mats. It was also found to increase thermal stability of polypropylene matrix composites as well as their strength.
相似文献8.
The metal content of a series of contaminated sediments has been determined by equilibrating ion-exchange resins of different types (held in porous cages) with aqueous suspensions of the sediments. H(+)-form exchangers took up high proportions of the Cu, Pb, Zn and Cd contents with recoveries depending on whether the acid functional groups were strong. Na(+)-form exchangers took up a smaller, loosely bound, labile fraction. The metal ions held on the exchangers were back-extracted into 0.05M EDTA and determined by flame AAS. Dissolution of sediment components led to the exchangers also taking up large amounts of Ca, Mg, Fe and Al. The exchange-resin technique provides an alternative means of subdividing the metal content of sediments into different "labile" or "available" fractions. Possible advantages include minimal re-adsorption of released metal ions by the sediment phases, retention of only "labile" species (ions or complexes), and a transfer mechanism which may resemble the action of plant roots more closely than chemical extractant processes do. 相似文献
9.
Pickering AL Seeber G Long DL Cronin L 《Chemical communications (Cambridge, England)》2004,(2):136-137
Isolated polymeric Ag(I) coordination tubes are self-assembled from the rigid triamino ligands cis,cis-1,3,5-triaminocyclohexane (cis-tach) and cis,trans-1,3,5-triaminocyclohexane (trans-tach), forming two topologically equivalent framework motifs. 相似文献
10.
Parenty AD Smith LV Pickering AL Long DL Cronin L 《The Journal of organic chemistry》2004,69(18):5934-5946
A new class of phenanthridinium derivative has been isolated from the reaction of 2-bromoethyl-phenanthridinium bromide with a range of primary amines in excellent yields. The reaction pathway is unprecedented and proceeds via three cascade steps: nucleophilic attack of a primary amine on the iminium moiety of a heteroaromatic ring system and cyclization to form a five-membered ring, followed by hydride loss to yield a rearomatized dihydro-1H-imidazo[1,2-f]phenanthridinium derivative. A range of NMR phase transfer experiments were carried out to elucidate the mechanistic pathway, and the methodology has been further developed by means of a biphasic system using N-bromosuccinimide as a co-oxidizing agent. The method has also been extended to other N-heterocyclic cation derivatives such as quinolinium and quinazolinium. 相似文献