全文获取类型
收费全文 | 651篇 |
免费 | 12篇 |
国内免费 | 49篇 |
专业分类
化学 | 659篇 |
晶体学 | 8篇 |
力学 | 1篇 |
物理学 | 44篇 |
出版年
2023年 | 14篇 |
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 60篇 |
2012年 | 30篇 |
2011年 | 43篇 |
2010年 | 28篇 |
2009年 | 49篇 |
2008年 | 51篇 |
2007年 | 44篇 |
2006年 | 43篇 |
2005年 | 40篇 |
2004年 | 45篇 |
2003年 | 12篇 |
2002年 | 20篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有712条查询结果,搜索用时 0 毫秒
41.
Hydrotris(3, 5‐dimethylpyrazol‐1‐yl)borate and hydrotris(3‐phenylpyrazol‐1‐yl)borate decompose during reactions with [ReOCl3(PPh3)2] and [NEt4]2[Re(CO)3Br3], respectively. The generated pyrazole ligands form complexes with the rhenium(V) oxo and the rhenium(I ) tricarbonyl cores. X‐ray crystal structures of the oxo‐bridged dimer [Cl(PPh3)(O)Re(μ‐O)(μ‐Me2pz)2Re(O)(HMe2pz)Cl] ( 1 ) and [Re(CO)3(HPhpz)2(Phpz)] ( 2 ) (HMe2pz = 3, 5‐dimethylpyrazole, HPhpz = 3‐phenylpyrazole) show that the substituted pyrazoles can readily deprotonate and act as monodentate or bridging anionic ligands. Re‐N bond lengths between 2.09 and 2.14Å have been observed for the bridging and between 2.12 and 2.23Å for the terminal pyrazole ligands. 相似文献
42.
43.
A. R. Hajipour S. E. Mallakpour I. Mohammadpoor-Baltork H. Adibi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2805-2811
Benzyltriphenylphosphonium peroxymonosulfate in the presence of bismuth chloride was found to be an efficient and mild reagent for the dethioacetalization of 1,3-dithiolanes and 1,3-dithianes to the corresponding carbonyl compounds under aprotic conditions. 相似文献
44.
Majid M. Heravi Fereshteh Hydarzadeh Yahya Farhangi Mitra Ghassemzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1473-1475
Primary and secondary trimethylsilyl ethers are effeciently converted to the corresponding carbonyl compounds using HZSM-5 zeolite-supported CrO 3 under microwave irradiation in solventless system. 相似文献
45.
46.
The reduction of a variety of carbonyl compounds was efficiently carried out with NaBH4/DOWEX(R)50WX4 system. The reactions were performed to give the corresponding alcohols derivatives in perfect yields in THF at room temperature. Reduction of acyloins and a‐diketones by this reducing system produced efficiently the corresponding vicinal diols. Also, the reduction of aldehydes over ketones has been accomplished successfully by this system. Regioselectivity of this system was also investigated with exclusive 1,2‐reduction of conjugated carbonyl compounds to their corresponding allylic alcohols in high to excellent yields. 相似文献
47.
Dagobert Achatz Markus A. Lang Alfons Vlkl Wolf Peter Fehlhammer Wolfgang Beck 《无机化学与普通化学杂志》2005,631(12):2339-2346
Carbonyl Complexes of Chromium, Molybdenum and Tungsten with Isocyano Acetate. Reactions of Coordinated Isocyanoacetate. Stabilization of Isocyanoacetic Acid and Isocyanoacetyl Chloride at the Metal Atom. Isocyanopeptides The reactions of [(OC)5MCNCH2CO2Et] (M = Cr, W) with Na[N(SiMe3)2] or with KOH afford the isocyanoacetate complexes [(OC)5MCNCH2CO2]? ( 1,2 ). Similarly, the complex [(OC)3Mo(CNCH2CO2?Li+)3] ( 4 ) was obtained from [(OC)3Mo(CNCH2CO2Et)3] ( 3 ) and LiOH. Protonation of 1 and 2 affords the sublimable isocyanoacetic acid complexes [(OC)5MCNCH2CO2H] ( 5 , 6 ; M = Cr, W) in which the functional isocyanide is stabilized at the metal atom. Reactions of [(OC)5WCNCH2CO2?K+] and of [(OC)3Mo(CNCH2CO2?Li+)3] with oxalyl dichloride give the isocyanoacetyl chloride compounds [(OC)5WCNCH2COCl] ( 9 ) (sublimable) and [(OC)3Mo(CNCH2COCl)3] ( 10 ); the latter ( 10 ) was not isolated. Complexes 9 and 10 were reacted in situ with β‐alanine, glycine, phenylalanine and methionine esters as well as the peptide esters GlyGlyOEt, PhePheOMe, Phe‐β‐AlaOMe, and GlyGlyGlyOMe to form the isocyanoacetyl amino acid esters ( 11 ‐ 14 ) and the isocyanoacetyl peptide esters ( 15 ‐ 18 ) which are stabilized at the molybdenum atom. 相似文献
48.
49.
Henrik Braband 《Journal of organometallic chemistry》2004,689(12):2066-2072
fac-[M(CO)3X3]2− complexes (M=Re, X=Br; M=Tc, X=Cl) react with thiourea derivatives under formation of stable rhenium(I) and technetium(I) complexes. The composition of the products can be controlled by the steric requirements of the ligands and their ability to form chelates.The products of reactions with tetramethylthiourea, Me4tu (I), N,N-diethylthiocarbamoylbenzamidine, H2Et2tcb (II), and morpholinylthiocarbamoylbenzamidine, H2morphtcb (III), have been studied by X-ray crystallography showing that the products belong to three different structural types. A mononuclear complex of the composition fac-[Re(CO)3Br(Me4tu)2] has been isolated with tetramethylthiourea, whereas the thiocarbamoylbenzamidines deprotonate and act as N,S-chelating ligands. This results in the formation of a dimeric [Tc(CO)3(HEt2tcb-N,S)]2 complex with a central, almost square Tc2S2 unit and a monomeric compound of the composition [Tc(CO)3(Hmorphtcb-N,S)(H2morphtcb-S)]. The latter compound contains a neutral, S-bonded morpholinylthiocarbamoylbenzamidine in the unusual imine form in addition to a chelate-bonded Hmorphtcb− ligand. 相似文献
50.
WenXiangHU XueJunHOU QingTaoPENG 《中国化学快报》2002,13(12):1199-1202
In this paper,a new HPLC method was established to determine the earbonyl compounds in air.As the absorbent,2,4-dinitrophenylhydrazint(2,4-DNPH)reaeted with earbonyls specifieally,which form the corresponding 2,4-dinitrophenylhydrazones,then analyzed by HPLC.The chromatographic conditions,the recovery rate,stability of samples,reagent blank,sampling efficiency were all studied systematically.The results showed that this established method had high sensitivity and good selectivity compared with other analytical methods,and it can detemine ten earbonyl compounds in air in 26 min simultancously. 相似文献