全文获取类型
收费全文 | 295篇 |
免费 | 23篇 |
专业分类
化学 | 231篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 47篇 |
物理学 | 29篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 19篇 |
2015年 | 21篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 28篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有318条查询结果,搜索用时 31 毫秒
31.
A Rh catalyzed, no-chelate-assisted C-H activation/oxidative olefination reaction of bromoarenes has been discovered, in which the latter ones seem to act as a substrate, terminal oxidant, and catalyst modifier. 相似文献
32.
Lorenz C Hoffmann A Gross G Windhagen H Dellinger P Möhwald K Dempwolf W Menzel H 《Macromolecular bioscience》2011,11(2):234-244
A fast and simple approach for immobilization using copolymers as interlayers is reported. The synthesized copolymers form stable self-assembled layers on implant materials like, e.g., titanium in a simple coating/drying/washing sequence and have functional groups which can bind proteins from an aqueous solution. The copolymer films have been characterized via ellipsometry and contact angle measurements and were tested for biocompatibility. An immunoassay was used to determine the amount of BMP2 and demonstrated an approximately 10-fold increase as compared to previously used self-assembled monolayers. A BMP2-responsive cell line with luciferase detection was used to determine the biological activity of the bound signaling protein. 相似文献
33.
The aim of this paper is to devise an adaptive timestep control in the contact-stabilized Newmark method (ContacX) for dynamical contact problems between two viscoelastic bodies in the framework of Signorini’s condition. In order to construct
a comparative scheme of higher order accuracy, we extend extrapolation techniques. This approach demands a subtle theoretical
investigation of an asymptotic error expansion of the contact-stabilized Newmark scheme. On the basis of theoretical insight
and numerical observations, we suggest an error estimator and a timestep selection which also cover the presence of contact.
Finally, we give a numerical example. 相似文献
34.
A series of phosphanes with imidazolyl substituents were prepared as hemilabile PN ligands. The corresponding gold(I) complexes were tested as bifunctional catalysts in the Markovnikov hydration of 1-octyne, as well as in the synthesis of propargylamines by the three component coupling reaction of piperidine, benzaldehyde, and phenylacetylene. While the activity in the hydration of 1-octyne was low, the complexes are potent catalysts for the three component coupling reaction. In homogeneous solution the conversions to the respective propargylamine were considerably higher than under aqueous biphasic conditions. The connectivity of the imidazolyl substituents to the phosphorus atom, their substitution pattern, as well as the number of heteroaromatic substituents have pronounced effects on the catalytic activity of the corresponding gold(I) complexes. Furthermore, formation of polymetallic species with Au(2), Au(3), and Au(4) units has been observed and the solid-state structures of the compounds [(5)(2)Au(3)Cl(2)]Cl and [(3c)(2)Au(4)Cl(2)]Cl(2) (3c = tris(2-isopropylimidazol-4(5)-yl phosphane, 5 = 2-tert-butylimidazol-4(5)-yldiphenyl phosphane) were determined. The gold(I) complexes of imidazol-2-yl phosphane ligands proved to be a novel source for bis(NHC)gold(I) complexes (NHC = N-heterocyclic carbene). 相似文献
35.
Simeonika Rangełowa‐Jankowska Dawid Jankowski Dr. Beata Grobelna Prof. Ignacy Gryczyński Prof. Zygmunt Gryczyński Dr. Robert Bogdanowicz Prof. Piotr Bojarski 《Chemphyschem》2011,12(13):2449-2452
The first observation of strong directional surface‐plasmon‐coupled emission (SPCE) of Rhodamine 110 in silica nanofilms deposited on silver nanolayers is reported. The preparation of the material is described in detail. The intensity of SPCE exceeds 10 times that of free space fluorescence and total linear light polarization in the SPCE ring is observed. A new experimental setup and an original data collection method is presented. Our material completely preserves its fluorescence properties for at least eight months. 相似文献
36.
37.
Aequationes mathematicae - In this paper the concept of symmetrized convex stochastic processes is introduced. Some characterizations involving Hermite–Hadamard type inequalities and a... 相似文献
38.
Dawid Maliszewski Agnieszka Wrbel Beata Kolesiska Justyna Frczyk Danuta Drozdowska 《Molecules (Basel, Switzerland)》2021,26(13)
A series of new analogs of nitrogen mustards (4a–4h) containing the 1,3,5-triazine ring substituted with dipeptide residue were synthesized and evaluated for the inhibition of both acetylcholinesterase (AChE) and β-secretase (BACE1) enzymes. The AChE inhibitory activity studies were carried out using Ellman’s colorimetric method, and the BACE1 inhibitory activity studies were carried out using fluorescence resonance energy transfer (FRET). All compounds displayed considerable AChE and BACE1 inhibition. The most active against both AChE and BACE1 enzymes were compounds A and 4a, with an inhibitory concentration of AChE IC50 = 0.051 µM; 0.055 µM and BACE1 IC50 = 9.00 µM; 11.09 µM, respectively. 相似文献
39.
40.
A. P. Dawid 《Journal of multivariate analysis》1985,17(3):304-315
Several general results are presented whereby various properties of independence or conditional independence between certain random variables may be deduced from the symmetries enjoyed by their joint distributions. These are applied to the distributions of sample correlation and canonical correlation coefficients when the underlying data-distribution has suitable orthogonal invariance. A typical result is that, for a random sample of observations on three independent normal variables, r12, r13, and r23.1 are mutually independent. 相似文献