全文获取类型
收费全文 | 526篇 |
免费 | 11篇 |
专业分类
化学 | 221篇 |
力学 | 9篇 |
数学 | 74篇 |
物理学 | 233篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 22篇 |
2012年 | 21篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 12篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1967年 | 6篇 |
1928年 | 3篇 |
1916年 | 4篇 |
排序方式: 共有537条查询结果,搜索用时 15 毫秒
21.
WST-1 and nitroblue tetrazolium (NBT) were used to quantify production of superoxide ions by leukocytes of the American alligator in whole blood. Because of the difficulty of isolating healthy leukocytes in alligators, these compounds were employed in whole blood instead of leukocyte preparations commonly used in other studies. The detection of superoxide was concentration- and time-dependent and linear with serial dilutions of whole blood. WST-1 reduction was inhibited by superoxide dismutase, indicating that the reduction was due to the presence of superoxide. Light microscopy revealed that superoxide production occurred in leukocytes, with no detectable contributions from other blood components. 相似文献
22.
G. Blois G. H. Sambrook Smith J. L. Best R. J. Hardy J. R. Lead 《Experiments in fluids》2012,53(1):51-76
This paper presents results of an experimental study investigating the mean and temporal evolution of flow within the pore space of a packed bed overlain by a free-surface flow. Data were collected by an endoscopic PIV (EPIV) technique. EPIV allows the instantaneous velocity field within the pore space to be quantified at a high spatio-temporal resolution, thus permitting investigation of the structure of turbulent subsurface flow produced by a high Reynolds number freestream flow (Re s in the range 9.8?×?103?C9.7?×?104). Evolution of coherent flow structures within the pore space is shown to be driven by jet flow, with the interaction of this jet with the pore flow generating distinct coherent flow structures. The effects of freestream water depth, Reynolds and Froude numbers are investigated. 相似文献
23.
24.
25.
Benjamin Radel Edme H. Hardy Zorana Djuric Markus Mahlbacher Michael Haist Harald S. Müller 《Magnetic resonance in chemistry : MRC》2019,57(10):836-844
Not only in low-field nuclear magnetic resonance, Laplace inversion is a relevant and challenging topic. Considerable conceptual and technical progress has been made, especially for the inversion of data encoding two decay dimensions. Distortion of spectra by overfitting of even moderate noise is counteracted requiring a priori smooth spectra. In this contribution, we treat the case of simple and fast one-dimensional decay experiments that are repeated many times in a series in order to study the evolution of a sample or process. Incorporating the a priori knowledge that also in the series dimension evolution should be smooth, peak position can be stabilized and resolution improved in the decay dimension. It is explained how the standard one-dimensional regularized Laplace inversion can be extended quite simply in order to include regularization in the series dimension. Obvious improvements compared with series of one-dimensional inversions are presented for simulated as well as experimental data. For the latter, comparison with multiexponential fitting is performed. 相似文献
26.
27.
28.
Weisshoff H Preiss A Nehls I Win T Mügge C 《Analytical and bioanalytical chemistry》2002,373(8):810-819
A hyphenated HPLC-(1)H NMR method for the identification and quantification of PAHs in soil samples has been developed and applied to a PAH reference sample provided by the Federal Institute for Materials Research and Testing (BAM, Berlin, Germany). The results were compared with those obtained by HPLC-DAD, HPLC-F, and GC-MS analyses of the same sample. 相似文献
29.
Miller RI Kiefl RF Brewer JH Sonier JE Chakhalian J Dunsiger S Morris GD Price AN Bonn DA Hardy WH Liang R 《Physical review letters》2002,88(13):137002
Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories. 相似文献
30.
Benzocyclobutene 10 and 3-oxabicyclo [3.2.0]hepta-1, 4-diene 11 are formed by gas-phase pyrolysis of the title compound 9 . The results are discussed with reference to the estimated reaction parameters. It is found that the activation due to oxygen in 9 is relatively weak in comparison to its effect on the reactivity of oxaquadricyclanes 1 . 相似文献