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141.
1introductionChitosan,adeacetylatedderivativeofchitin,isnatUralpolysaccharideswithfreeaminogroups.Itcanactasanexcellentadsorbenttoadsorbnotonlyvariousorganiccompoundsincludingpolychlorinatedbiphenyls,proteinsandnucleicacids,butalsometalions[1~sl.ChitosanhasbeenwidelyemployedasaneffectivecoagulatingagentinactivatedsludgeplantSandfoodprocessingfactories,andalsoinpreparation,concentTationandpurificationofmetalionsinhydrometallurgy.Chitosanbehavesasanaturalchelatingpolymer.Chitosanundergoeschela… 相似文献
142.
Joseph H. Reibenspies Erach R. Talaty Mashitah M. Yusoff 《Journal of chemical crystallography》1997,27(12):727-730
The crystal and molecular structure of (RS)-N-Tert-butyl-2-anilino-3,3-dimethylbutanamide, a derivative of an amino acid that was obtained by highly selective cleavage of 1,3-di-tert-butylaziridinone by aniline, is described. The racemic mixture of the amide crystallizes in the space groupP 21/n with four molecules per unit cell. Crystal Data:a=10.483(2) Å,b=6.206(1) Å,c=24.767(5) Å,β=90.39(3),V=1611.5(6) A3,R(F)[I>2σ(I)]=0.0679.wR(F 2) [I>2σ(I)]=0.1148. 相似文献
143.
144.
I. B. Dzvinchuk S. A. Kartashov A. V. Vypirailenko U. Doller M. O. Lozinskii 《Chemistry of Heterocyclic Compounds》2004,40(5):570-574
The possibility has been studied of converting quaternary 3-anilino-1,5-dimethylpyrazolium salts into 3-anilino-1,5-dimethylpyrazole, the first representative of the 1-alkyl-3-arylaminopyrazoles. The dependence of the reaction direction on the nature of the substituent at position 2 has been clarified. The most effective result was obtained with a cyanoethyl substituent. On boiling the initial salt with aqueous ammonia the target product is isolated in quantitative yield. Syntheses of the initial salts are described. C-Sulfonation was detected on interacting 3-anilino-1-benzoyl-3-methylpyrazole and dimethyl sulfate, with the formation of p-(3-amino-1,2,5-trimethylpyrazolio)benzenesulfonate. 相似文献
145.
Masakazu Yoshikawa Katsunori Koso Kyoichi Yonetani Satoshi Kitamura Satoshi Kimura 《Journal of polymer science. Part A, Polymer chemistry》2005,43(2):385-396
Molecularly imprinted polymeric membranes were prepared from various oligopeptide tweezers by the adoption of N‐α‐tert‐butoxycarbonyl‐D ‐tryptophan (Boc‐D ‐Trp) or N‐α‐tert‐butoxycarbonyl‐L ‐tryptophan (Boc‐L ‐Trp) as a print molecule. The chiral recognition ability of the formed molecular recognition sites was dependent on the absolute configuration of the print molecule adopted in the membrane preparation (molecular imprinting) process, whereas the candidate oligopeptide tweezers consisted of the L ‐amino acid residues. In other words, the membranes imprinted by the D ‐isomer recognized the D ‐isomer in preference to the corresponding L ‐isomer, and vice versa. The affinity constant between the target molecule and the chiral recognition site from the oligopeptide tweezers was higher than that from a single‐strand oligopeptide derivative. Those membranes selectively transported the enantiomer, which was preferentially incorporated into the membrane by dialysis. The permselectivities for these membranes exceeded their adsorption selectivities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 385–396, 2005 相似文献
146.
本文在速率方程基础上通过数值模拟方法 ,对镥的激光共振电离通道 :5d6s2 2 D3 /2 (5 73.6 5 5nm)→5d6s6 p4F3 /2 (6 4 2 .5 18nm)→ 6s6 p2 4P1/2 (6 4 3.5 4 8nm)→Autoionizationstate的激光诱导同位素选择性进行了研究。在实际实验条件下用这一方法计算得到的激光波长对激光诱导同位素选择性的关系与实验结果相符合。探讨了在偏振激光作用的情况下各种激光参数 (波长、带宽和激光强度 )对激光诱导同位素选择性的影响 ,并提出了在一定实验条件下激光共振电离质谱计较为准确地测定同位素比值的方法。这一理论方法 ,同样适用于研究其它元素的激光共振电离同位素选择性和选择激光同位素分离电离通道 相似文献
147.
Manganese‐Catalyzed Synthesis of cis‐β‐Amino Acid Esters through Organometallic CH Activation of Ketimines
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M. Sc. Weiping Liu M. Sc. Daniel Zell Dr. Michael John Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2015,54(13):4092-4096
Manganese‐catalyzed C? H functionalization reactions of ketimines set the stage for the expedient synthesis of cis‐β‐amino acid esters through site‐ and regioselective alkene annulations. The organometallic C? H activation occurred efficiently with high functional group tolerance, delivering densely functionalized β‐amino acid derivatives with ample scope. 相似文献
148.
Dr. Yi Jiang Lei-Li Sun Guang-Zong Ren Xiang Niu Wen-zhou Hu Prof. Zhi-Qiang Hu 《ChemistryOpen》2015,4(3):378-382
The development of novel selective probes with high sensitivity for the detection of Al3+ is widely considered an important research goal due to the importance of such probes in medicine, living systems and the environment. Here, we describe a new fluorescent probe, N′-(4-diethylamino-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (1), for Al3+. Probe 1 was evaluated in a solution of acetonitrile/water (1:1 v/v). Compared with previously reported probes for Al3+, probe 1 can be synthesized easily and in high yield. A Job plot confirmed that probe 1 is able to complex Al3+ in a 1:1 ratio, and the binding constant was determined to be 4.25×108 m−1. Moreover, the detection limit was as low as 6.7×10−9 m, suggesting that probe 1 has a high sensitivity. Common coexistent metal ions, such as K+, Co2+, Ca2+, Ba2+, Ni2+, Pb2+, Hg2+, Ce2+, Zn2+, Cd2+, Fe3+, showed little or no interference in the detection of Al3+ in solution, demonstrating the high selectivity of the probe. Finally, the ability of probe 1 to act as a fluorescent probe for Al3+ in living systems was evaluated in Gram-negative bacteria, Escherichia coli, and confocal laser scanning microscopy confirmed its utility. The results of this study suggest that 1 has appropriate properties to be developed for application as a fluorescent probe of Al3+ for use in biological studies. 相似文献
149.
Tauseef Ahmad Rangreez Mu Naushad Hamid Ali 《International journal of environmental analytical chemistry》2015,95(6):556-568
In this study, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) zirconium(IV) monothiophosphate composite cation exchanger was prepared by sol–gel precipitation method. The presence of sulphur in the cation exchanger enhances affinity towards the heavy metal ions which can improve the selectivity of the material. The selectivity studies showed that the material is selective towards Pb(II) ions. To characterise the material, several physicochemical properties were also studied which includes X-ray, scanning electron microscopy and transmission electron microscopy studies. The ion-exchange behaviour of this cation exchanger was studied by using some of the selected properties like ion-exhange capacity for various metal ions, elution, effect of eluent concentration, thermal effect on ion-exchange capacity (IEC). The results of IEC and physicochemical properties revealed that the material is nanocomposite, crystalline, chemically, mechanically and thermally stable. The analytical ability of this cation exchanger was demonstrated in binary separation of Pb(II) ions from a mixture of other metal ions. The recovery is qualitative and the separations are reproducible. 相似文献
150.
Aromatic Interactions in Organocatalyst Design: Augmenting Selectivity Reversal in Iminium Ion Activation
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Dr. Constantin Daniliuc Dr. W. Bernd Schweizer Prof. Dr. Ryan Gilmour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10031-10038
Substituting N‐methylpyrrole for N‐methyindole in secondary‐amine‐catalysed Friedel–Crafts reactions leads to a curious erosion of enantioselectivity. In extreme cases, this substrate dependence can lead to an inversion in the sense of enantioinduction. Indeed, these closely similar transformations require two structurally distinct catalysts to obtain comparable selectivities. Herein a focussed molecular editing study is disclosed to illuminate the structural features responsible for this disparity, and thus identify lead catalyst structures to further exploit this selectivity reversal. Key to effective catalyst re‐engineering was delineating the non‐covalent interactions that manifest themselves in conformation. Herein we disclose preliminary validation that intermolecular aromatic (CH–π and cation–π) interactions between the incipient iminium cation and the indole ring system is key to rationalising selectivity reversal. This is absent in the N‐methylpyrrole alkylation, thus forming the basis of two competing enantio‐induction pathways. A simple L ‐valine catalyst has been developed that significantly augments this interaction. 相似文献