全文获取类型
收费全文 | 1259篇 |
免费 | 57篇 |
国内免费 | 2篇 |
专业分类
化学 | 1103篇 |
晶体学 | 7篇 |
力学 | 13篇 |
数学 | 68篇 |
物理学 | 127篇 |
出版年
2023年 | 13篇 |
2022年 | 110篇 |
2021年 | 98篇 |
2020年 | 33篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 35篇 |
2016年 | 67篇 |
2015年 | 53篇 |
2014年 | 74篇 |
2013年 | 99篇 |
2012年 | 113篇 |
2011年 | 96篇 |
2010年 | 62篇 |
2009年 | 50篇 |
2008年 | 64篇 |
2007年 | 63篇 |
2006年 | 46篇 |
2005年 | 51篇 |
2004年 | 33篇 |
2003年 | 28篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有1318条查询结果,搜索用时 31 毫秒
981.
A new three nuclear triple-stranded helicate complex M3L3 containing Na+/Li+ ions has been synthetized and characterised by 1H, 23Na, 7Li solution NMR, ESI-MS and X-ray crystallography. 相似文献
982.
JPC – Journal of Planar Chromatography – Modern TLC - Flavonoid glycosides from the aerial parts (leaves, flowers, and fruits) of Peucedanum tauricum Bieb. (Apiaceae) have been analyzed... 相似文献
983.
Wójciak-Kosior M Krzaczek T Matysik G Skalska A 《Journal of separation science》2005,28(16):2139-2143
HPTLC combined with densitometric method was used to determine the content of oleanolic acid in acetone extract from the Lamii albi flos L. The plant extract was separated on Si 60 HPTLC plates and determined with the use of two densitometric methods: measurement of fluorescence and absorbance. The content of oleanolic acid was statistically calculated. In a measurement of absorbance in 1 g of the dry Lamii albi flos L. 1458 microg of oleanolic acid was determined (0.147%). In a fluorescence method in 1 g of the plant material 1516 microg of oleanolic acid was determined (0.149%). 相似文献
984.
An efficient silylative coupling of trisubstituted vinylsilanes with dialkoxy(vinyl)boranes is described. Under optimum conditions the reaction offers a selective route to 1-(silyl)-1-(boryl)ethenes, which are potentially attractive intermediates in organic synthesis 相似文献
985.
Enzymes may be used to develop an environmentally friendly alternative to the conventional polluting technologies in textile
finishing. The action of the unlabeled and fluorescent labeled proteolytic enzymes subtilisin and trypsin on wool was examined.
Scanning electron micrographs and a diffusion study, based on fluorescence microscopy, localized the enzymatic attack on the
fiber. A kinetic study was carried out by monitoring the amino acid content of the treatment liquor.
Enzymatic action is not confined to the fiber surface. To limit attack to the surface and reduce wool damage new treatment
methods such as enzyme immobilization onto a solid carrier must be investigated. 相似文献
986.
A. T. Adorno R. A. G. Silva A. G. Magdalena 《Journal of Thermal Analysis and Calorimetry》2007,87(3):759-762
Thermal behavior of α-(Cu–Al–Ag) alloys, i.e. alloys
with composition less than about 8.5 mass% Al, was studied using differential
scanning calorimetry (DSC), differential thermal analysis (DTA), scanning
electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray
diffractometry (XRD). The results indicated that the presence of silver introduces
new thermal events ascribed to the formation of a silver-rich phase and, after
addition higher amounts than 8 mass% Ag to the Cu–8 mass% Al alloy it
is possible to observe the formation of the γ1
phase (Al4Cu9), which is only
observed in alloys containing minimum of 9 mass% Al. These results may be
attributed to some Ag characteristics and its interaction with Cu and Al. 相似文献
987.
We present an implementation of the polarizable continuum model for the calculation of solvent effects on electronic circular dichroism spectra. The computational model used is density functional theory in the length-gauge formulation, and gauge-origin independence is ensured through the use of London atomic orbitals. Results of calculations carried out for methyloxirane and bicyclic ketones, camphor, norcamphor, norbornenone, and fenchone are presented, and the theoretically obtained solvent effects are compared with experimental observations. 相似文献
988.
Iwona akomska Magdalena Barwioek Edward Szyk Boenna Golankiewicz 《Transition Metal Chemistry》2007,32(1):70-73
The preparation and spectroscopic study (1H, 13C, 15NNMR, 13CP MAS NMR, IR) of new PdII complexes with 6,8-dimethylimidazo[1,5-a]-1,3,5-triazin-4(3H)-one (6,8-DiMe-4-O-IMT) (1) and 6,8-dimethyl-2-thioxo-2,3-dihydroimidazo[1,5-a]-1,3,5-triazin-4(1H)-one (6,8-DiMe-4-O-2-S-IMT) (2) is reported. The spectroscopic data indicate a square planar geometry with two N(7) bonded heterocycles and two cis-chloride anions. The final product of the thermal decomposition of cis-PdCl2(6,8-DiMe-4-O-IMT)2
(3) is metallic Pd, whereas for cis-PdCl2(6,8-DiMe-4-O-2-S-IMT)2
(4) it is metallic Pd plus C. 相似文献
989.
Magdalena Kloskowska Antoni Konitz Wiesaw Wojnowski Barbara Becker 《无机化学与普通化学杂志》2006,632(15):2424-2428
The title compound, [Sn(μ–S){SSi(OtBu)3}2]2 ( 1 ), containing four–coordinated tin(IV), crystallizes in two polymorphic modifications. The orthorhombic 1a –form has been obtained in the reaction of (tBuO)3SiSH and Et3N with SnCl2, whereas the triclinic 1b –form in the reaction with SnCl4 as substrate. The crystal and molecular structures of both polymorphs ( 1a as a redetermination) have been determined by a single–crystal X–ray diffraction study at room temperature. The title compound was shown to react with ammonia and ammonia complexes of some d–block metal cations giving products of Sn–S bond cleavage. 相似文献
990.
Makowska-Grzyska MM Jeppson PC Allred RA Arif AM Berreau LM 《Inorganic chemistry》2002,41(19):4872-4887
Using a mixed nitrogen/sulfur ligand possessing a single internal hydrogen bond donor (N,N-bis-2-(methylthio)ethyl-N-(6-amino-2-pyridylmethyl)amine (bmapa)), we prepared and structurally and spectroscopically characterized a series of zinc complexes possessing a single alcohol ([(bmapa)Zn(MeOH)](ClO(4))(2) (1)), formamide ([(bmapa)Zn(DMF)](ClO(4))(2) (3), [(bmapa)Zn(NMF)](ClO(4))(2) (4)), or sulfoxide ([(bmapa)Zn(DMSO)](ClO(4))(2) (7), [(bmapa)Zn(TMSO)](ClO(4))(2) (8)) ligand. X-ray crystallographic characterization was obtained for 1.MeOH, 3, 4, 7.DMSO, and 8. To enable studies of the influence of the single hydrogen bond donor amino group of the bmapa ligand on the chemistry of zinc/neutral oxygen donor binding interactions, analogous alcohol ([(bmpa)Zn(MeOH)](ClO(4))(2) (2)), formamide ([(bmpa)Zn(DMF)](ClO(4))(2) (5), [(bmpa)Zn(NMF)](ClO(4))(2) (6)), and sulfoxide ([(bmpa)Zn(DMSO)](ClO(4))(2) (9), [(bmpa)Zn(TMSO)](ClO(4))(2) (10)) complexes of the bmpa (N,N-bis-2-(methylthio)ethyl-N-(2-pyridylmethyl)amine) ligand system were generated and characterized. Of these, 2, 5, 6, and 9.2DMSO were characterized by X-ray crystallography. Solution spectroscopic methods ((1)H and (13)C NMR, FTIR) were utilized to examine the formamide binding properties of 3-6 in CH(3)CN and CH(3)NO(2) solutions. Conclusions derived from this work include the following: (1) the increased donicity of formamide and sulfoxide donors (versus alcohols) makes these competitive ligands for a cationic N/S-ligated zinc center, even in alcohol solution, (2) the inclusion of a single internal hydrogen bond donor, characterized by a heteroatom distance of approximately 2.80-2.95 A, produces subtle structural perturbations in N/S-ligated zinc alcohol, formamide, or sulfoxide complexes, (3) the heteroatom distance of a secondary hydrogen-bonding interaction involving the oxygen atom of a zinc-coordinated alcohol, formamide, and sulfoxide ligand is reduced with increasing donicity of the exogenous ligand, and (4) formamide displacement on a N/S-ligated zinc center is rapid, regardless of the presence of an internal hydrogen bond donor. These results provide initial insight into the chemical factors governing the binding of a neutral oxygen donor to a N/S-ligated zinc center. 相似文献