全文获取类型
收费全文 | 169篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 91篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 32篇 |
物理学 | 46篇 |
出版年
2022年 | 2篇 |
2019年 | 3篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 14篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 3篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1944年 | 1篇 |
1938年 | 2篇 |
1935年 | 1篇 |
1902年 | 1篇 |
1891年 | 1篇 |
排序方式: 共有176条查询结果,搜索用时 31 毫秒
41.
42.
Thin films of CuSc1−xMgxO2+y have been rendered conducting by intercalation of oxygen. Hole conductivities up to of order 10 S/cm can be achieved at the expense of visible transparency, especially in the blue region of the spectrum. Hole conductivities up to 100 S/cm have been achieved in pressed pellets of K-doped BaCuSF, and a band-gap of 3.2 eV has been measured on undoped films. 相似文献
43.
44.
45.
46.
M. S. Jovanović J. Brborić S. Vladimirov B. Zmbova LJ. Vuksanović D. Živanov-Stakić V. Obradović 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):321-324
A new diiodine substituted IDA derivative, 2,4-diiodine-6-methyl IDA (DIIODIDA) was synthesized and labeled with99mTc. It was established that99mTc-DIIODIDA had high radiochemical purity. Biodistribution and influence of bilirubin on99mTc-DIIODIDA biokinetics has been studied in rats and compared to the corresponding results for99mTc-SOLCOIODIDA. Related to99mTc-SOLCOIODIDA,99mTc-DIIODIDA has much better biliary exretion (55.18 versus 43.63%). No change of99mTc-DIIODIDA biokinetics, under influence of bilirubin was noticed. Biliary excretion of99mTc-SOLCOIODIDA has been reduced for about 60%. The protein binding of99mTc-DIIODIDA and99mTc-SOLCOIODIDA were also determined, using in vitro method of precipitation. These results showed that99mTc-DIIODIDA hepatobiliary imaging agent is superior to the presently used99mTc-monoiodine IDA derivatives. 相似文献
47.
C. C. Coffin G. Grinling F. G. H. Tate 《Analytical and bioanalytical chemistry》1935,102(5-6):198-199
48.
Several implementation methods of quantum computation algorithm by conventional computer have been explored for large-scale
emulation. Due to the lack of quantum effects, these methods generally require exponential growth of the size of the hardware
with increase of the number of qubits. In this paper, the spatial coding, which is an effective digital optical computing
technique, is studied as an efficient implementation method of quantum computation algorithms. In the proposed scheme, quantum
information is represented by the intensity and the phase of elemental cells. We confirmed correct operation of the quantum
teleportation algorithm by computer simulation. We also demonstrated a photonic implementation of some of the quantum gates
experimentally. 相似文献
49.
Devos A Lukas L Suykens JA Vanhamme L Tate AR Howe FA Majós C Moreno-Torres A van der Graaf M Arús C Van Huffel S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(1):164-175
The purpose was to objectively compare the application of several techniques and the use of several input features for brain tumour classification using Magnetic Resonance Spectroscopy (MRS). Short echo time 1H MRS signals from patients with glioblastomas (n = 87), meningiomas (n = 57), metastases (n = 39), and astrocytomas grade II (n = 22) were provided by six centres in the European Union funded INTERPRET project. Linear discriminant analysis, least squares support vector machines (LS-SVM) with a linear kernel and LS-SVM with radial basis function kernel were applied and evaluated over 100 stratified random splittings of the dataset into training and test sets. The area under the receiver operating characteristic curve (AUC) was used to measure the performance of binary classifiers, while the percentage of correct classifications was used to evaluate the multiclass classifiers. The influence of several factors on the classification performance has been tested: L2- vs. water normalization, magnitude vs. real spectra and baseline correction. The effect of input feature reduction was also investigated by using only the selected frequency regions containing the most discriminatory information, and peak integrated values. Using L2-normalized complete spectra the automated binary classifiers reached a mean test AUC of more than 0.95, except for glioblastomas vs. metastases. Similar results were obtained for all classification techniques and input features except for water normalized spectra, where classification performance was lower. This indicates that data acquisition and processing can be simplified for classification purposes, excluding the need for separate water signal acquisition, baseline correction or phasing. 相似文献
50.
Kurita J Shimahara H Utsunomiya-Tate N Tate S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,163(1):163-173
The chemical shifts of nuclei that have chemical shielding anisotropy, such as the 15N amide in a protein, show significant changes in their chemical shifts when the sample is altered from an isotropic state to an aligned state. Such orientation-dependent chemical shift changes provide information on the magnitudes and orientation of the chemical shielding tensors relative to the molecule's alignment frame. Because of the extremely high sensitivity of the chemical shifts to the sample conditions, the changes in chemical shifts induced by adding aligned bicelles do not arise only from the protein alignment but should also include the accumulated effects of environmental changes including protein-bicelle interactions. With the aim of determining accurate 15N chemical shielding tensor values for solution proteins, here we have used magic angle sample spinning (MAS) to observe discriminately the orientation-dependent changes in the 15N chemical shift. The application of MAS to an aligned bicelle solution removes the torque that aligns the bicelles against the magnetic field. Thus, the application of MAS to a protein in a bicelle solution eliminates only the molecular alignment effect, while keeping all other sample conditions the same. The observed chemical shift differences between experiments with and without MAS therefore provide accurate values of the orientation-dependent 15N chemical shifts. From the values for ubiquitin in a 7.5% (w/v) bicelle medium, we determined the 15N chemical shielding anisotropy (CSA) tensor. For this evaluation, we considered uncertainties in measuring the 1H-15N dipolar couplings and the 15N chemical shifts and also structural noise present in the reference X-ray structure, assuming a random distribution of each NH bond vector in a cone with 5 degrees deviation from the original orientation. Taking into account these types of noise, we determined the average 15N CSA tensor for the residues in ubiquitin as Delta sigma=-162.0+/-4.3 ppm, eta=0.18+/-0.02, and beta=18.6+/-0.5 degrees, assuming a 1H-15N bond length of 1.02 A. These tensor values are consistent with those obtained from solid-state NMR experiments. 相似文献