全文获取类型
收费全文 | 1081篇 |
免费 | 11篇 |
国内免费 | 5篇 |
专业分类
化学 | 552篇 |
晶体学 | 1篇 |
力学 | 14篇 |
数学 | 116篇 |
物理学 | 414篇 |
出版年
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 14篇 |
2013年 | 48篇 |
2012年 | 45篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 44篇 |
2007年 | 37篇 |
2006年 | 59篇 |
2005年 | 54篇 |
2004年 | 43篇 |
2003年 | 39篇 |
2002年 | 37篇 |
2001年 | 31篇 |
2000年 | 36篇 |
1999年 | 21篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 29篇 |
1992年 | 28篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1973年 | 8篇 |
1972年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有1097条查询结果,搜索用时 125 毫秒
91.
C Eden F Ackermann J M Bryson G P Richardson D F Andersen C B Finn 《The Journal of the Operational Research Society》2009,60(1):2-13
There is a need to bring methods to bear on public problems that are inclusive, analytic, and quick. This paper describes the efforts of three pairs of academics working from three different though complementary theoretical foundations and intervention backgrounds (ie ways of working) who set out together to meet this challenge. Each of the three pairs had conducted dozens of interventions that had been regarded as successful or very successful by the client groups in dealing with complex policy and strategic problems. One approach focused on leadership issues and stakeholders, another on negotiating competitive strategic intent with attention to stakeholder responses, and the third on analysis of feedback ramifications in developing policies. This paper describes the 10-year longitudinal research project designed to address the above challenge. The important outcomes are reported: the requisite elements of a general integrated approach and the enduring puzzles and tensions that arose from seeking to design a wide-ranging multi-method approach. 相似文献
92.
Kurt Munk Andersen 《International Journal of Mathematical Education in Science & Technology》2013,44(3):449-453
Rayleigh's principle states that the smallest eigenvalue of a regular Sturm-Liouville problem with regular boundary conditions is the minimum value of a certain functional, the so-called Rayleigh quotient, and that this value is attained at the corresponding eigenfunctions only. This can be proved by advanced methods. However, there is an elementary proof, which is presented in this note. 相似文献
93.
94.
Negative specific heat is a dramatic phenomenon where processes decrease in temperature when adding energy. It has been observed in gravo-thermal collapse of globular clusters. We now report finding this phenomenon in bundles of nearly parallel, periodic, single-sign generalized vortex filaments in the electron magnetohydrodynamic (EMH) model for the unbounded plane under strong magnetic confinement. We derive the specific heat using a steepest descent method and a mean field property. Our derivations show that as temperature increases, the overall size of the system increases exponentially and the energy drops. The implication of negative specific heat is a runaway reaction, resulting in a collapsing inner core surrounded by an expanding halo of filaments. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
95.
Klimov AB Björk G Söderholm J Madsen LS Lassen M Andersen UL Heersink J Dong R Marquardt Ch Leuchs G Sánchez-Soto LL 《Physical review letters》2010,105(15):153602
We propose an operational degree of polarization in terms of the variance of the Stokes vector minimized over all the directions of the Poincaré sphere. We examine the properties of this second-order definition and carry out its experimental determination. Quantum states with the same standard (first-order) degree of polarization are correctly discriminated by this new measure. We argue that a comprehensive quantum characterization of polarization properties requires a whole hierarchy of higher-order degrees. 相似文献
96.
Nils Byrial Andersen Gestur Ó lafsson 《Proceedings of the American Mathematical Society》2001,129(1):173-179
We formulate and prove a topological Paley-Wiener theorem for the normalized spherical Laplace transform defined on the rank 1 causal symmetric spaces , for .
97.
A (p, q, x)-latin rectangle is a rectangular matrix with x symbols in each cell such that each symbol occurs at most p times in each row and at most q times in each column. We exploit the close correspondence between (p, q, x)-latin rectangles and equitable edge-colourings of certain graphs. This paper contains results on existence and various forms of decomposition of such rectangles. In a sequel paper embedding is considered. 相似文献
98.
99.
Functional magnetic resonance imaging with intermolecular multiple-quantum coherences 总被引:4,自引:0,他引:4
Richter W Richter M Warren WS Merkle H Andersen P Adriany G Ugurbil K 《Magnetic resonance imaging》2000,18(5):489-494
For the first time, we demonstrate here functional magnetic resonance imaging (fMRI) using intermolecular multiple-quantum coherences (iMQCs). iMQCs are normally not observed in liquid-state NMR because dipolar interactions between spins average to zero. If the magnetic isotropy of the sample is broken through the use of magnetic field gradients, dipolar couplings can reappear, and hence iMQCs can be observed. Conventional (BOLD) fMRI measures susceptibility variations averaged over each voxel. In the experiment performed here, the sensitivity of iMQCs to frequency variations over mesoscopic and well-defined distances is exploited. We show that iMQC contrast is qualitatively and quantitatively different from BOLD contrast in a visual stimulation task. While the number of activated pixels is smaller in iMQC contrast, the intensity change in some pixels exceeds that of BOLD contrast severalfold. 相似文献
100.