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991.
Mekhman S. Yusubov Tatyana V. Funk Roza Y. Yusubova Galina Zholobova Joo Yeon Park 《合成通讯》2013,43(21):3772-3784
m-Iodosylbenzoic acid–mediated reactions of various carbonyl compounds provided α-organosulfonyloxy carbonyl compounds in good yields. The final products could be easily isolated without any chromatographic purification by simple treatment of the crude mixture with an anionic exchange resin. 相似文献
992.
Abstract α,α‐Dibromoketones (2) have been found to be a superior alternative to the conventionally used α‐bromoketones (1) for performing the Hantzsch thiazole synthesis.1 These crystalline, nonlachrymatory compounds are more reactive than 1 as demonstrated by their reaction with 3,5‐dimethyl‐1‐thiocarboxamide (5). 相似文献
993.
The work describes our attempts to synthesize the C13 to C21 fragment of brasilinolides, a 32-membered macrolide class of molecule. The C13 to C21 segment encompasses six asymmetric centers and a pyran ketal moiety. The synthesis starts from L-malic acid, and the salient features of our asymmetric synthesis are opening of epoxide, assymmetric dihydroxylation for the creation of vic-diol, and Barbier allylation. 相似文献
994.
Alessandra Ammazzalorso Maria Luisa Tricca Isabella Bruno Barbara De Filippis Mauro Di Matteo Marialuigia Fantacuzzi 《合成通讯》2013,43(22):2546-2554
The direct acylation of sulfonamides by esters represents an attractive strategy in organic chemistry, being an interesting alternative to classical approaches to N-acylsulfonamides. Here is described a simple and effective method to obtain N-acylsulfonamides of pharmaceutical interest, in a reaction promoted by titanium(IV) chloride. This strategy was successfully applied to the synthesis of a peroxisome proliferator–activated receptor α antagonist with a benzenesulfonimide moiety, ensuring an excellent yield of product. The reaction was further studied to explore the behavior of different α-bromoesters and esters and the effects of para-substitution in the benzenesulfonamide moiety. 相似文献
995.
Po S. Poon Ng 《合成通讯》2013,43(13):2261-2268
A total synthesis of (±)-cis-5-hydroxycalamenene 1 has been achieved from tetralone 5, which in turn was prepared from 5-methoxy-α-tetralone 3. Grignard reaction of compound 5 with isopropylmagnesium chloride, followed by dehydration and aromatization, provided the substituted naphthalene 7 whose conversion to (±)-cis-5-hydroxycalamenene 1 was accomplished by demethylation, formylation, and hydrogenation. 相似文献
996.
Ahmad Farouk Eweas 《合成通讯》2013,43(10):1541-1552
The ring‐closure metathesis of the diene (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐yl acrylate produced the dihydropyrone with the correct stereochemistry for Soraphen A1α synthesis. The C2,C3 stereocenters were introduced by the addition of the (Z)‐crotyl‐n‐butylstannane to the β‐alkoxyaldehyde(S)‐3‐(benzyloxy)‐2‐methylpropanal in presence of TiCl4 as a chelating catalyst to give the desired anti,syn homoallyic alcohol (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐ol. 相似文献
997.
Faxiang Tao Ying Liu Ning An 《International journal of environmental analytical chemistry》2013,93(8):605-619
α-cellulose is widely used as a target substance for isotope ratio analysis in environmental reconstructions. Its preparation includes three basic steps: organic solvent extraction, delignification and alkaline hydrolysis. Recent works have suggested omission of the first step. We have made a detailed comparison in carbon isotope ratio of α-cellulose with or without organic solvent extraction using 32 consecutive tree ring and 30 subfossil peat samples. These samples were exposed to three different chemical treatments: with organic solvent extraction as the first step (CellOE), without organic solvent extraction (CellNOE), and with organic solvent extraction as the final step (CellNOE/OE). The third treatment is used to test if organic extractives can be completely removed or if their solubility in organic solvents has been altered by delignification and alkaline hydrolysis. In tree rings and peat, δ13CC ell NOE was always significantly different from δ13CC ell OE, but the trends were not the same. In tree rings, δ13CC ell NOE was always more negative than δ13CC ell OE by ?0.31 ~ ?0.01‰. In contrast, δ13CC ell NOE in peat could be more negative or more positive than δ13CC ell OE by ?3.08 ~ 0.27‰. The third chemical treatment resulted in different patterns. For tree rings, δ13CC ell NOE/OE was still more negative than δ13CC ell OE by ?0.36 ~ ?0.08‰. However, the differences between δ13CC ell NOE/OE and δ13CC ell OE for peat varied in a more narrow range from ?0.58 to 0.61‰, compared to the differences between δ13CC ell NOE and δ13CC ell OE. These results exposed a complex chemical evolution behaviour and an incomplete removal of lipids during delignification and alkaline hydrolysis. The mean value, long-term trend and seesaw patterns for a tree ring or peat CellNOE series were significantly different from those for a CellOE series, indicating that omission of organic solvent extraction will lead to a biased inference of past environmental conditions. 相似文献
998.
采用周期性密度泛函理论研究羟基化α-石英(101)面的铀酰离子吸附行为.通过对铀酰离子的水合作用考虑水溶剂对结构的短程溶剂化效应,并通过类导体屏蔽模型(COSMO)考虑水溶剂对结构的远程溶剂化效应.吸附能计算结果和电子结构数据均表明水合铀酰离子吸附构型比氢氧化铀酰吸附构型稳定,并且在液相中两种类型的稳定吸附位均为dia-Os1Os2位.两种形式在电子结构上有很大的差异,主要是由于铀与表面作用后成键强弱程度不同,使5f轨道宽化和略微红移存在差异.在铀酰离子吸附的基础上利用卤素离子改变铀酰离子配位环境可调整体系的带隙. 相似文献
999.
《Journal of Saudi Chemical Society》2014,18(3):227-233
Formation of binary and ternary complexes of lead(II) ions with 1-(aminomethyl) cyclohexane acetic acid and some biologically important α-amino acids, such as glycine, l-alanine, l-valine, l-leucine, l-isoleucine, l-phenylalanine and l-proline was investigated using the potentiometric technique at 32 °C. The properties of mixed ligands were investigated and discussed. The acidity constants of the ligands and their stability constants were determined in 50% (v/v) DMSO-water medium under experimental conditions. The ternary complex formation was found to occur in a stepwise manner. The stability of ternary complexes was investigated and compared with that of the corresponding binary complex in terms of the parameters, Δ log K and log X. The concentration distribution of various species formed in the mixed ligand systems was evaluated. 相似文献
1000.
With 1,1,1-trifluoro-2-iodoethane as catalyst, a novel and efficient procedure has been developed for preparation of α-tosyloxyketones from ketones. In this protocol, 1,1,1-trifluoro-2-iodoethane is first oxidized by m-chloroperbenzoic acid to a hypervalent iodine intermediate. The in situ–generated active iodine species then reacts with ketones to afford the corresponding α-tosyloxyketones in good yields. 相似文献