首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1539篇
  免费   57篇
  国内免费   7篇
化学   1057篇
晶体学   13篇
力学   33篇
数学   148篇
物理学   352篇
  2023年   6篇
  2022年   12篇
  2021年   14篇
  2020年   17篇
  2019年   40篇
  2018年   23篇
  2017年   20篇
  2016年   37篇
  2015年   43篇
  2014年   34篇
  2013年   86篇
  2012年   94篇
  2011年   102篇
  2010年   54篇
  2009年   47篇
  2008年   84篇
  2007年   83篇
  2006年   85篇
  2005年   57篇
  2004年   66篇
  2003年   64篇
  2002年   65篇
  2001年   37篇
  2000年   37篇
  1999年   22篇
  1998年   24篇
  1997年   19篇
  1996年   24篇
  1995年   17篇
  1994年   13篇
  1993年   14篇
  1992年   23篇
  1991年   29篇
  1990年   23篇
  1989年   14篇
  1988年   14篇
  1987年   11篇
  1986年   14篇
  1985年   21篇
  1984年   17篇
  1983年   19篇
  1982年   12篇
  1981年   9篇
  1980年   10篇
  1979年   11篇
  1978年   4篇
  1977年   5篇
  1976年   5篇
  1975年   7篇
  1970年   3篇
排序方式: 共有1603条查询结果,搜索用时 0 毫秒
101.
Intertemporal decision making involves choices among options whose effects occur at different moments. These choices are influenced not only by the effect of reward value perception at different moments, but also by the time perception effect. One of the main difficulties that affect standard experiments involving intertemporal choices is the simultaneity of both effects on time discounting. In this paper, we unify the psychophysical laws and discount value functions using the one-parameter exponential and logarithmic functions from nonextensive statistical mechanics. Also, we propose to measure the degree of inconsistency. This quantity allow us to discriminate both effects of time and value perception on discounting process and, by integration, obtain other main quantities like impulsivity and discount functions.  相似文献   
102.
An efficient four-step biotransformation-mediated synthesis of (1S)-1-(2,6-dichloro-3-fluorophenyl)ethanol in enantiomerically pure form is described. This compound is a key intermediate required for the preparation of PF-2341066, a potent inhibitor of c-Met/ALK that is currently in clinical development. The described synthesis was used to manufacture 6 kg of the title compound and can also be employed to produce the corresponding (1R)-enantiomer.  相似文献   
103.
We study the resonances of the semiclassical Schr?dinger operator near a non-trapping energy level in the case when the potential V is not necessarily analytic on all of but only outside some compact set. Then we prove that for some and for any C > 0, P admits no resonance in the domain if V is , and if V is Gevrey with index s. Here does not depend on h and the results are uniform with respect to h > 0 small enough. Submitted 05/02/02, accepted 06/05/02 An erratum to this article is available at .  相似文献   
104.
Three-dimensional dive trajectories of three sperm whales in the Gulf of Mexico have been obtained by measuring the relative arrival times and bearings of the animals' acoustic multipath reflections, using two elements of a towed hydrophone array deployed at an unknown depth and orientation. Within the first 6-12 min of the start of a dive, the intervals between successive "clicks" of all three whales corresponded closely with the two-way travel time of an acoustic pulse traveling vertically between the animals' position and the ocean bottom. The click spectra contained multiple peaks, including a faint band of energy originally centered near 10 kHz. As the animals descended over 500 m in depth, the center frequency of this band shifted to nearly 15 kHz, but subsequently remained near this value during the rest of the dive. This frequency shift is consistent with that expected from energy scattering from an ensemble of incompressible small-scale air-filled resonators, with diameters on the order of 4 mm. One possible candidate for such an ensemble is proposed to reside in the collapsed frontal sac of the animal. A comparison of the received levels for the bottom and direct multipath arrivals indicates that the whales' acoustic directivity must range between 10-30 dB in the 5-20-kHz region.  相似文献   
105.
The 1,3-bis(diphosphinomethyl)ferrocene 3 readily reacts with [(C2H4)2RhCl]2 to form an equilibrating pair of diastereomers 8a and 8b by C-H insertion into the ferrocene.  相似文献   
106.
Excited states in 59Zn were observed for the first time following the fusion-evaporation reaction 24Mg + 40Ca at a beam energy of 60 MeV. The GASP array in conjunction with the ISIS Silicon ball and the NeutronRing allowed for the detection of γ-rays in coincidence with evaporated light particles. The mirror symmetry of 59Zn and 59Cu is discussed. Received: 28 May 2002 / Accepted: 10 July 2002 / Published online: 3 December 2002 RID="a" ID="a"Present address: Oliver Lodge Laboratory, University of Liverpool, P.O. Box 147, Liverpool, L69 7ZE, United Kingdom; e-mail: ca@ns.ph.liv.ac.uk. RID="b" ID="b"Present address: Physik-Departament, Technische Universit?t München, D-85748 Garching, Germany. Communicated by W. Henning  相似文献   
107.
Extreme Estimates for Interpolated Operators by the Real Method   总被引:3,自引:0,他引:3  
The paper establishes estimates for ideal measures of operatorsinterpolated by the real method in terms of the measures oftheir restrictions to a sequence of spaces modelled on the intersection.It also shows that the estimates are optimal.  相似文献   
108.
Tedesco PH  Martinez J 《Talanta》1984,31(2):155-161
Theoretical, experimental and statistical aspects of the polarographic method applied to simple and mixed-ligand complex formation have been studied. Some misunderstandings and erroneous interpretations have been clarified according to experimental results obtained with several systems. A criterion for establishing the number of complex species present in a simple system is proposed. For the first time the polarographic method has been applied to a mixed-ligand complex system where fourteen species co-exist.  相似文献   
109.
The autoinhibiting reaction of ozone with dimethyl sulfide (DMS), has been studied at 296°K and 1.1 kPa (8 torr) as a function of the concentrations of both reactants. The major products of the reaction are H2CO, H2O, CO, and SO2. The specific rate of primary attack of O3 on DMS is immeasurably slow. It is suggested that the rapid overall rate observed for this reaction is due to a chain reaction initiated by the very slow primary reaction. It is concluded that reaction (1) cannot be important under atmospheric conditions and that the major loss process for DMS in the atmosphere is probably reaction with photochemically generated free radicals.  相似文献   
110.
Observation of the internal luminescence of Cr2+(3d4) in GaAs under hydrostatic pressure is reported. The activation of this luminescence is correlated to the lifting of the degeneracy between the excited level of Cr2+ and the conduction band of the host material. The possible mechanisms giving rise to this luminescence are discussed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号