全文获取类型
收费全文 | 344篇 |
免费 | 8篇 |
专业分类
化学 | 248篇 |
晶体学 | 16篇 |
力学 | 9篇 |
数学 | 47篇 |
物理学 | 32篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 16篇 |
2011年 | 26篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 22篇 |
2007年 | 28篇 |
2006年 | 19篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 2篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有352条查询结果,搜索用时 31 毫秒
61.
Papish ET Taylor MT Jernigan FE Rodig MJ Shawhan RR Yap GP Jové FA 《Inorganic chemistry》2006,45(5):2242-2250
Ligands of intermediate steric bulk were designed to mimic metalloenzymes with histidine and carboxlyate binding sites. The reaction between tris(3-isopropylpyrazolyl)methane and butyllithium followed by SO3NMe3 in THF yielded the new ligand lithium tris(3-isopropylpyrazolyl)methane sulfonate (LiTpmsiPr). Various metal salts reacted with LiTpmsiPr to give the octahedral complexes M(TpmsiPr)2 (M = Zn, Cu, Ni, Co, Fe) in which each ligand has N,N,O binding to the metal. In the reaction between LiTpmsiPr and ZnCl2, in addition to the major product Zn(TpmsiPr)2, [LiTpmsiPrZnCl2].2THF was also formed as a minor product with a tetrahedral zinc atom coordinated to either N,N,Cl,Cl in the solid phase or N,N,N,Cl in acetonitrile solution. Although TpmsiPr is coordinatively flexible and can act as a bipodal or tripodal ligand, it appears to favor the formation of octahedral L2M complexes. 相似文献
62.
The neutral arene ruthenium azido complexes [(η6-p-cymene)Ru(LL)(N3)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η6-p-cymene)Ru(LL){N3C2(CO2R)2}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η6-p-cymene)Ru(LL)(N3C2HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η6-p-cymene)Ru(dppe)(N3)]+ and [(η6-p-cymene)Ru(dppm)(N3)]+ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction. 相似文献
63.
Wesley H. Monillas Glenn P. A. Yap Klaus H. Theopold 《Journal of chemical crystallography》2009,39(7):535-538
Abstract Addition LiNHPh to a [(NacNac)Cr(μ-I)]2 [NacNac = 2,4 pentane-N-N′-bis(2,6-diisopropylphenyl) ketiminato] in THF yields a dimeric anilido complex, 1, that crystallizes in P21/n with unit cell parameters a = 13.390(2) ?, b = 26.298(5) ?, c = 21.326(4) ?, β = 93.905(4)°, V = 7492(2) ?3 and Z = 4. The same reaction in the presence of aniline yields a monomeric anilido complex, 2, with a coordinated aniline molecule. Complex 2 crystallizes in P2
1
/c with unit cell parameters a = 28.530(5) ?, b = 10.8116(18) ?, c = 26.492(5) ?, β = 115.685(3)°, V = 7364(2) ?3 and Z = 8. Addition of aniline to isolated 1 yields 2. Addition of LiNPh2 to [(NacNac)Cr(μ-I)]2 in THF yields a monomeric complex that crystallizes in P21/n with the unit cell parameters a = 11.152(6) ?, b = 23.820(12) ?, c = 17.915(9) ?, β = 106.223(9)°, V = 4569(4) ?3 and Z = 4. All complexes have been spectroscopically and structurally characterized.
Graphical Abstract Addition of LiNHPh or LiNPh2 to [(NacNac)Cr(μ-I)]2 yields a dimeric or a monomeric complex whereas addition of LiNHPh in the presence of aniline yields the monomeric anilido
complex.
相似文献
64.
Wesley H. Monillas Glenn P. A. Yap Klaus H. Theopold 《Journal of chemical crystallography》2009,39(11):849-852
Abstract
The complexes (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(μ2-diisopropylacetamidinato) chromium(II) (1) and (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(μ2-dicyclohexylacetamidinato) chromium(II) (2) have been synthesized and structurally characterized. Complex 1 crystallizes in space group Pbcn with crystal cell parameters a = 10.7183(13) ?, b = 16.4093(19) ?, c = 20.687(2) ?, V = 3,638.3(7) ?3 and Z = 4. Complex 2 crystallizes in triclinic space group P-1 with crystal cell parameters a = 10.750(3) ?, b = 12.174(3) ?, c = 16.308(4) ?, α = 75.903(4)°, β = 82.137(4)°, γ = 85.511(4), V = 2,048.4(8) ?3 and Z = 2. The complexes adopt a spiro distorted square planar geometry and have similar structural parameters. 相似文献65.
Ching J Soh WL Tan CH Lee JF Tan JY Yang J Yap CW Koh HL 《Journal of separation science》2012,35(1):53-59
Conventional methods of drug discovery from natural products include bioassay-guided fractionation, which is tedious and has low efficiency. The aim of this work is to develop a platform method to rapidly identify bioactive compounds from crude plant extracts and their partially purified fractions using multivariate data analysis (MVDA). Soxhlet extraction and liquid-liquid fractionation were used to prepare different extracts and fractions from the leaves of a medicinal plant, Ardisia elliptica. The extracts and fractions were analysed chemically using GC-MS, and their ability to inhibit platelet aggregation was investigated. Two MVDA methods were developed and optimised to analyse the results. In the first method, compounds with the highest contribution scores for biological activity calculated by different models were listed as potential antiplatelet compounds. For the second MVDA method, a correlation of the concentrations of constituents and biological activities in the various extracts and fractions for each compound was done. Compounds with the highest correlation coefficients were identified as potential antiplatelet compounds. One of the predicted components was isolated, purified and confirmed to possess antiplatelet effects. This platform method can be developed and optimised for other plant extracts and biological activities, thus reducing time and cost of drug discovery while improving efficiency. 相似文献
66.
We have disclosed a new mode of a chemically regioselective switch for C-H bond functionalization of benzimidazole derivatives via a cooperative effect invoked by Ni-Al bimetallic catalysis to create a steric requirement for obtaining the linear product of styrene insertion. Yet, excluding the AlMe(3) cocatalyst switches the reaction toward branch selectivity. 相似文献
67.
Due to the importance of neuraminidase in the pathogenesis of influenza virus infection, it has been regarded as the most important drug target for the treatment of influenza. Resistance to currently available drugs and new findings related to structure of the protein requires novel neuraminidase 1 (N1) inhibitors. In this study, a consensus QSAR model with defined applicability domain (AD) was developed using published N1 inhibitors. The consensus model was validated using an external validation set. The model achieved high sensitivity, specificity, and overall accuracy along with low false positive rate (FPR) and false discovery rate (FDR). The performance of model on the external validation set and training set were comparable, thus it was unlikely to be overfitted. The low FPR and low FDR will increase its accuracy in screening large chemical libraries. Screening of ZINC library resulted in 64,772 compounds as probable N1 inhibitors, while 173,674 compounds were defined to be outside the AD of the consensus model. The advantage of the current model is that it was developed using a large and diverse dataset and has a defined AD which prevents its use on compounds that it is not capable of predicting. The consensus model developed in this study is made available via the free software, PaDEL-DDPredictor. 相似文献
68.
Metabolic activation of chemicals into covalently reactive species might lead to toxicological consequences such as tissue necrosis, carcinogenicity, teratogenicity, or immune-mediated toxicities. Early prediction of this undesirable outcome can help in selecting candidates with increased chance of success, thus, reducing attrition at all stages of drug development. The ensemble modelling of mixed features was used for the development of a model to classify the metabolic activation of chemicals into covalently reactive species. The effects of the quality of base classifiers and performance measure for sorting were examined. An ensemble model of 13 naive Bayes classifiers was built from a diverse set of 1,479 compounds. The ensemble model was validated internally with five-fold cross validation and it has achieved sensitivity of 67.4% and specificity of 93.4% when tested on the training set. The final ensemble model was made available for public use. 相似文献
69.
A pulsed laser system is realized with graphene employed as a Q-switch.The graphene is exfoliated from its solution using an optical deposition and the optical tweezer effect.A fiber ferrule that already has the graphene deposited on it is inserted into an erbium-ytterbium laser(EYL)system with linear cavity configuration.We successfully demonstrate a pulsed EYL with a pulse duration of approximately 5.9μs and a repetition rate of 20.0 kHz. 相似文献
70.
Yap JL Cao X Vanommeslaeghe K Jung KY Peddaboina C Wilder PT Nan A MacKerell AD Smythe WR Fletcher S 《Organic & biomolecular chemistry》2012,10(15):2928-2933
By conducting a structure-activity relationship study of the backbone of a series of oligoamide-foldamer-based α-helix mimetics of the Bak BH3 helix, we have identified especially potent inhibitors of Bcl-x(L). The most potent compound has a K(i) value of 94 nM in vitro, and single-digit micromolar IC(50) values against the proliferation of several Bcl-x(L)-overexpressing cancer cell lines. 相似文献