全文获取类型
收费全文 | 80437篇 |
免费 | 2583篇 |
国内免费 | 299篇 |
专业分类
化学 | 51375篇 |
晶体学 | 539篇 |
力学 | 1668篇 |
综合类 | 1篇 |
数学 | 12830篇 |
物理学 | 16906篇 |
出版年
2022年 | 523篇 |
2021年 | 749篇 |
2020年 | 1137篇 |
2019年 | 976篇 |
2018年 | 859篇 |
2017年 | 825篇 |
2016年 | 1994篇 |
2015年 | 1675篇 |
2014年 | 1969篇 |
2013年 | 3831篇 |
2012年 | 3782篇 |
2011年 | 4487篇 |
2010年 | 2408篇 |
2009年 | 2106篇 |
2008年 | 4268篇 |
2007年 | 4032篇 |
2006年 | 3855篇 |
2005年 | 3522篇 |
2004年 | 2936篇 |
2003年 | 2452篇 |
2002年 | 2360篇 |
2001年 | 1416篇 |
2000年 | 1313篇 |
1999年 | 1015篇 |
1998年 | 941篇 |
1997年 | 949篇 |
1996年 | 1122篇 |
1995年 | 919篇 |
1994年 | 988篇 |
1993年 | 1025篇 |
1992年 | 914篇 |
1991年 | 714篇 |
1990年 | 760篇 |
1989年 | 644篇 |
1988年 | 689篇 |
1987年 | 695篇 |
1986年 | 605篇 |
1985年 | 951篇 |
1984年 | 934篇 |
1983年 | 792篇 |
1982年 | 911篇 |
1981年 | 817篇 |
1980年 | 801篇 |
1979年 | 713篇 |
1978年 | 727篇 |
1977年 | 688篇 |
1976年 | 613篇 |
1975年 | 591篇 |
1974年 | 556篇 |
1973年 | 520篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Markus Bödenler Ludovic de Rochefort P. James Ross Nicolas Chanet Geneviève Guillot Gareth R. Davies 《Molecular physics》2019,117(7-8):832-848
ABSTRACTFast field-cycling (FFC) nuclear magnetic resonance relaxometry is a well-established method to determine the relaxation rates as a function of magnetic field strength. This so-called nuclear magnetic relaxation dispersion gives insight into the underlying molecular dynamics of a wide range of complex systems and has gained interest especially in the characterisation of biological tissues and diseases. The combination of FFC techniques with magnetic resonance imaging (MRI) offers a high potential for new types of image contrast more specific to pathological molecular dynamics. This article reviews the progress in FFC-MRI over the last decade and gives an overview of the hardware systems currently in operation. We discuss limitations and error correction strategies specific to FFC-MRI such as field stability and homogeneity, signal-to-noise ratio, eddy currents and acquisition time. We also report potential applications with impact in biology and medicine. Finally, we discuss the challenges and future applications in transferring the underlying molecular dynamics into novel types of image contrast by exploiting the dispersive properties of biological tissue or MRI contrast agents. 相似文献
32.
Tereshchenko E. D. Cherniakov S. M. Yurik R. Yu. Rietveld M. T. Häggström I. 《Radiophysics and Quantum Electronics》2020,62(10):667-676
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar... 相似文献
33.
34.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
35.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
36.
37.
38.
Partially supported by NSF Grants. 相似文献
39.
40.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献