全文获取类型
收费全文 | 522篇 |
免费 | 4篇 |
国内免费 | 8篇 |
专业分类
化学 | 191篇 |
晶体学 | 12篇 |
力学 | 6篇 |
数学 | 141篇 |
物理学 | 184篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 36篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 18篇 |
2009年 | 23篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 26篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1972年 | 7篇 |
1930年 | 2篇 |
排序方式: 共有534条查询结果,搜索用时 46 毫秒
151.
By surveying the most used methods for evaluating the kinetic parameters from nonisothermal experiments, a new classification scheme of the methods is proposed. For each method the number of principles and theoretical approximations required to derive the equation which grounds it, is considered as a comparison criterion. The methods are, finally, classified into classes of equivalence. As a result of the analysis it is also suggested that the activation energy, as calculated from nonisothermal data, should be given as a range of values instead of a unique value. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 313–327, 1998. 相似文献
152.
Mihaela Monica Constantin Ctlina Gabriela Corbu Sorin Mocanu Elena Irina Popescu Marin Micutz Teodora Staicu Raluca omoghi Bogdan Tric Vlad Tudor Popa Aurica Precupas Iulia Matei Gabriela Ionita 《Molecules (Basel, Switzerland)》2022,27(1)
Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements. 相似文献
153.
R. Cristescu C. Popescu S. Grigorescu D. Mihaiescu R.J. Narayan I. Stamatin 《Applied Surface Science》2009,255(24):9873-9876
We report the thin film deposition by matrix-assisted pulsed laser evaporation (MAPLE) of a polymer conjugate with an hydrophilic sequence between metronidazole molecules that was covalently attached to both oligomer ends of carboxylate poly(ethylene glycol) (PEG 1.5-metronidazole). A pulsed KrF* excimer laser was used to deposit the drug-polymer composite films. Fourier transform infrared spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical properties similar to the starting materials. The dependence of the surface morphology on incident laser fluence is given. 相似文献
154.
155.
156.
Popescu G Deflores LP Vaughan JC Badizadegan K Iwai H Dasari RR Feld MS 《Optics letters》2004,29(21):2503-2505
By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda/5500, which is stable over several hours. The results obtained on epithelial and red blood cells demonstrate the potential of this instrument for quantitative investigation of the structure and dynamics associated with biological systems without sample preparation. 相似文献
157.
158.
Given a principal ideal domain R of characteristic zero, containing1/2, and a two-cone X of appropriate connectedness and dimension,we present sufficient algebraic conditions for the Hopf algebraFH(X; R) to be isomorphic with the universal enveloping algebraof an R-free graded Lie algebra; here, F stands for free part(that is, quotient by the R-torsion), H for homology, and forthe Moore loop space functor. 2000 Mathematics Subject Classification55P35, 55P62, 57T05, 17B70, 17B35. 相似文献
159.
Lucre
iu M. Popescu 《Journal of computational physics》2000,160(2):5565
An extension of the alias sampling technique for distribution functions depending on a number of parameters was developed. It takes advantage of modern computer architectures with large amounts of cheap memory, by using discrete representations of probability distribution functions. The sampling is done by fast interpolation techniques involving only elementary logical and arithmetical operations, allowing one to keep a higher degree of accuracy as the grids spacing is controlled by the user. By this method it is possible to obtain the value of interest by direct interpolation between the sampled values obtained with the same set of random numbers for the grid values of the parameters adjacent to the values of interest. Sampling tests carried for the case of Molière electron multi-scatter angle distribution show that this method can be successfully used in Monte Carlo codes for sampling complex probability distributions. 相似文献
160.
M. Ivaşcu D. Popescu E. Drăgulescu V. Avrigeanu C. Beşliu N. Martalogu 《Nuclear Physics A》1974,218(1):104-108
Mean lives and excitation energies of the lowest levels in64Ni,66Zn and68Zn were measured with the aid of the (α, α′γ) and (α, pγ) reactions. The γ-rays were detected in coincidence with the outgoing particles. The following mean lives were determined from DSA measurements: 400 ± 150 fs for the level at Ex = 1.35 MeV in 64Ni; 270 ± 100, 210 ± 110, 330 ± 200, 80 ± 70 fs for the levels at Ex = 1.87, 2.45, 2.83, 2.94 MeV in 66Zn, and 1300 ± 300, > 160, 600 ± 200 fs for the levels at Ex = 1.08, 1.89 and 2.76 MeV in 68Zn, respectively. 相似文献