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201.
202.
非束缚核9He的实验研究 总被引:1,自引:1,他引:0
简要介绍了目前有关非稳定核^9He的实验和理论研究现状.现代壳模型理论计算表明。He的基态自旋宇称为1/2^+,而不是1/2^-,即存在自旋宇称翻转现象.到目前为止,实验上虽然观测到了^9He的几个共振态,但还不能确认其基态的能量和自旋宇称值.利用新的实验技术——逆运动学弹性共振散射,对^9He核进行研究,给出了共振态的自旋宇称可能的取值范围.在ISOL型次级束装置上的实验有望能给出^9He核能级的精确测量.The status of theoretical and experimental investigations on unbound nucleus()~(9)He is briefly introduced. The results of modern shell model suggest that the ground state of~(9)He should be 1/2~(+) instead of 1/2~(- )as expected by the normal shell ordering. Therefore, it means that the parity inversion which was well known in~(11)Be occurs also in~(9)He ground state. Recently, some resonance states were observed in transfer reactions and final-state reaction, but their spin-parities cannot be exact... 相似文献
203.
U. Leinberger E. Berdermann F. Heine S. Heinz O. Joeres P. Kienle I. Koenig W. Koenig C. Kozhuharov A. Schröter H. Tsertos C. Hofmann G. Soff 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):249-256
We present the first energy and angle resolved measurements of e+e−-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical
results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the
nucleus. The 1.76 MeV E0 transition in 90Zr (90Sr source) and the 1.77 MeV M1 transition in 207Pb (207Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer
of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders
of magnitude higher β− and γ background from the same source and to yield essentially background-free sum spectra despite the large background.
Using the ability of the ORANGE setup to directly determine the opening angle of the e+e−–pairs (Θe+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θe+e−≤ 180°). In the 90Zr case the correlation could be deduced for a wide range of energy differences E
Δ of the pairs (−530 keV ≤E
Δ≤ 530 keV). The 90Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in 207Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic
character. This is again in agreement with the new theoretical results.
Received: 22 April 1997 / Revised version: 16 December 1997 相似文献
204.
葛愉成 叶沿林 郑涛 王全进 李智焕 李湘庆 江栋兴 A.Ozawa Y.Yamaguchi C.Wu R.Kanungo D.Fang I.Tanihata 《中国物理 C》2004,28(3):262-267
报道了经仔细设计的150MeV 6He+9Be实验,并在质心系大角度处测量10Be和11Be同位素产物的实验数据.鉴别得到相应于单中子转移的371个10Be事件,同时观测到了相应于双中子转移的5个11Be事件.由此得到相应微分截面分别为(0.11±0.02)mb/sr(θcm≈137.4°)和(1.0±0.7)μb/sr(θcm≈133.4°),结果表明在所研究的反应体系中,单中子转移截面要比双中子转移截面约大100倍.在6He由5He-n和α-2n组成的集团模型下,利用零力程扭曲波玻恩近似(DWBA)的计算程序,在数量级上重现了单、双中子转移反应的实验数据 相似文献
205.
R. E. Tribble F. Abegglen G. Chubarian H. L. Clark G. Derrig G. Kim D. May G. A. Souliotis G. Tabacaru 《The European physical journal. Special topics》2007,150(1):255-258
The Cyclotron Institute at Texas A&M University is carrying out an upgrade project
which will lead to accelerated radioactive ion beams at intermediate energies. The project
involves recommissioning a K150 cyclotron for acceleration of stable beams which will be used
to produce radioactive ions. Both light-ion and heavy-ion guides will be used
to stop and transport the radioactive ions to a charge breeding electron cyclotron resonance ion
source. Following charge breeding, highly-charged ions will be injected into the K500 cyclotron,
accelerated and then transported to existing equipment to carry out experiments. 相似文献
206.
G. A. Souliotis A. L. Keksis B. C. Stein M. Veselsky M. Jandel D. V. Shetty S. N. Soisson S. Wuenschel S. J. Yennello 《The European physical journal. Special topics》2007,150(1):325-327
Recent efforts to produce and separate neutron-rich rare
isotopes in peripheral collisions below the Fermi energy are
presented. The experiments have been performed at the Cyclotron
Institute of Texas A&M University employing beams from the K500
Superconducting Cyclotron. Two magnetic separators were used: the
MARS recoil separator and the Superconducting Solenoid Line (BigSol
Line). An enhanced production of neutron-rich nuclides in comparison
with high-energy fragmentation mechanisms has been observed and
attributed to the role of the N/Z and the nuclear periphery of the
target. From a practical viewpoint, these reactions below or around
the Fermi energy offer a novel way to access very neutron-rich rare
isotopes. The experience obtained in the production of rare isotope
beams (RIB) below the Fermi energy will be exploited in the ongoing
RIB upgrade of the Cyclotron Institute that will involve production,
stopping and reacceleration of rare isotopes. 相似文献
207.
A. Andrighetto C. M. Antonucci S. Cevolani C. Petrovich M. Santana Leitner 《The European Physical Journal A - Hadrons and Nuclei》2006,30(3):591-601
The target system is one of the key issues for the facilities aimed at the production of neutron-rich radioactive ion beams.
In the framework of the SPES project (Study for the Production of Exotic Species), the possibility of using a target configuration
with a proton beam (40MeV, 0.2mA) directly impinging on multiple uranium carbide disks is investigated. The 238U fission fragments constitute the source for the exotic beams and for this purpose the disks are placed inside a graphite
box at 2000 °C. The target is split into several thin disks in order to allow the cooling of the system by thermal radiation. In this way
about ∼ 1013 fissions s
-1 are obtained with a relative simple system and with relative low costs. Further steps have been performed compared to previous
publications and now all the main parameters of the system have been analysed by means of calculation codes: the fission rates
and the fission fragment distribution; the power deposition and the thermal analysis; the thermo-mechanical behaviours of
the disks; the effusive and diffusive extraction release properties of the target. 相似文献
208.
J.A. Nolen 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):255-261
There are several nuclear physics laboratories in North America that have on-going research using energetic and stopped radioactive
beams. These include the large ISOL-type programs ISAC at TRIUMF and HRIBF at Oak Ridge and the in-flight fragmentation program
at the NSCL of Michigan State University. There are also smaller, more specialized, programs using a variety of techniques
at the 88-inch cyclotron of Berkeley, ATLAS at Argonne, the Cyclotron Institute of Texas A&M University, the Nuclear Structure
Laboratory at Notre Dame University, and the Nuclear Structure Laboratory at SUNY/Stony Brook. There are also three projects
on the horizon in North America for new capabilities in both the near term and more distant future. The intensities of the
in-flight fragment beams at the NSCL will be increased dramatically very soon as the Coupled Cyclotron Project will be completed
and commissioned for research by mid-2001. A new project, ISAC-II, has been approved in Canada. For the longer term, the United
States is considering construction of a major new facility, the Rare Isotope Accelerator (RIA), which would have a very high-intensity
heavy-ion driver linac. The RIA facility is proposed to utilize both ISOL and in-flight production mechanisms.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
209.
Ch. E. Düllmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):75-80
In recent years, the concept of physical preseparation of single atoms was
introduced into the field of transactinide chemistry. In this approach, the
transactinide element of interest is isolated in a physical recoil separator
and then extracted from this machine. The beam as well as the unwanted
reaction products are strongly suppressed, allowing for the investigation of
new chemical systems that were not accessible before.
The most important aspects of the technique are discussed and the advantages
for chemistry experiments with transactinides are presented, using some of
the chemical studies that were performed with preseparated isotopes as
examples. 相似文献
210.