全文获取类型
收费全文 | 1560篇 |
免费 | 29篇 |
国内免费 | 8篇 |
专业分类
化学 | 815篇 |
晶体学 | 10篇 |
力学 | 11篇 |
数学 | 206篇 |
物理学 | 555篇 |
出版年
2020年 | 21篇 |
2019年 | 16篇 |
2016年 | 30篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 45篇 |
2012年 | 36篇 |
2011年 | 56篇 |
2010年 | 42篇 |
2009年 | 30篇 |
2008年 | 43篇 |
2007年 | 61篇 |
2006年 | 53篇 |
2005年 | 38篇 |
2004年 | 41篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 30篇 |
2000年 | 32篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 21篇 |
1996年 | 28篇 |
1995年 | 33篇 |
1994年 | 37篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 22篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 24篇 |
1977年 | 28篇 |
1976年 | 14篇 |
1975年 | 18篇 |
1974年 | 19篇 |
1973年 | 11篇 |
1972年 | 12篇 |
1969年 | 13篇 |
1967年 | 12篇 |
1930年 | 12篇 |
排序方式: 共有1597条查询结果,搜索用时 31 毫秒
121.
F.?P.?He?bergerEmail author S.?Hofmann I.?Kojouharov D.?Ackermann 《The European Physical Journal A - Hadrons and Nuclei》2004,22(2):253-260
Isomeric states in 210-215Ra have been populated by the decay of the compound nuclei 216,220Ra produced in irradiations of 204,208Pb with 12C at
MeV. Published values for
-ray energies and half-lives were confirmed for
Ra. Our data for
Ra agree with the
-energies and the half-life measured at the RITU separator, University of Jyväskylä (Finland). Its decay pattern is complex. Two series of
-rays of
keV and
keV were observed. A half-life of
s was measured. The isomeric state is attributed to an 8 + state at E
* = 2053.8keV. A previously unknown isomeric state was assigned to
Ra. It has a half-life of (
)
and it decays by emission of
-rays with energies of 396.1keV and 802.0keV. It is attributed to a 13/2 + state at E
* = 1198.1 keV.PACS:
23.60. + e
decay - 27.90. + b
相似文献
122.
Orlinskii SB Schmidt J Baranov PG Hofmann DM de Mello Donegá C Meijerink A 《Physical review letters》2004,92(4):047603
Electron paramagnetic resonance and electron nuclear double resonance (ENDOR) experiments on ZnO nanoparticles reveal the presence of shallow donors related to interstitial Li and Na atoms. The shallow character of the wave function is evidenced by the multitude of 67Zn ENDOR lines and further by the hyperfine interactions with the 7Li and 23Na nuclei that are much smaller than for atomic lithium and sodium. In the case of the Li-doped nanoparticles, an increase of the hyperfine interaction with the 7Li nucleus and with the 1H nuclei in the Zn(OH)(2) capping layer is observed when reducing the size of the nanoparticles. This effect is caused by the confinement of the shallow-donor 1s-type wave function that has a Bohr radius of about 1.5 nm, i.e., comparable to the dimension of the nanoparticles. 相似文献
123.
Kleinsorge B Golovko VB Hofmann S Geng J Jefferson D Robertson J Johnson BF 《Chemical communications (Cambridge, England)》2004,(12):1416-1417
Highly purified cobalt colloids have been employed as a catalyst to grow aligned carbon nanofibres at temperatures as low as 300 degree C by dc plasma enhanced chemical vapour deposition over large areas. 相似文献
124.
A. N. Andreyev D. Ackermann F. P. Heßberger S. Hofmann M. Huyse I. Kojouharov B. Kindler B. Lommel G. Münzenberg R. D. Page K. Van de Vel P. Van Duppen K. Heyde 《The European Physical Journal A - Hadrons and Nuclei》2003,18(1):55-64
Alpha-decay of the new nuclide 184Bi has been studied in the complete-fusion reaction 93Nb(94Mo, 3n)184Bi at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of recoil-
, recoil-
-
analysis and excitation functions measurements. Two
-decaying isomeric states in 184Bi with half-life values of 13(2) ms and 6.6(1.5) ms were identified. The
-branching ratio of 180Tl was deduced for the first time as
. Improved data on the fine-structure
-decay of 186Bi were obtained in the 93Nb(95Mo, 2n)186Bi reaction. A similarity of the decay energies and half-life values of 184,186Bi is pointed out and a possible explanation for this effect is suggested.Received: 14 March 2003, Revised: 29 April 2003, Published online: 2 September 2003PACS:
23.60.+e
decay - 27.70.+q
- 27.80.+w
K. Heyde: Present address: EP-ISOLDE, CERN, CH-1211, Geneva 23, Switzerland. 相似文献
125.
Energy exchange between the longitudinal and transverse degrees of freedom of nonequipartitioned bunched beams (non-neutral plasmas) is investigated by means of 3D simulation. It is found that collective instability may lead to energy transfer in the direction of equipartition, without full progression to it, in certain bounded regions of parameter space where internal resonance conditions are satisfied, in good agreement with stability charts from an earlier derived 2D Vlasov analysis. Nonequipartitioned stable equilibria, however, exist in relatively wide regimes of parameter space. This provides evidence that such regimes may be safely used in the design of future high-intensity linacs. 相似文献
126.
H.A. Michelsen F. Liu B.F. Kock H. Bladh A. Boiarciuc M. Charwath T. Dreier R. Hadef M. Hofmann J. Reimann S. Will P.-E. Bengtsson H. Bockhorn F. Foucher K.-P. Geigle C. Mounaïm-Rousselle C. Schulz R. Stirn B. Tribalet R. Suntz 《Applied physics. B, Lasers and optics》2007,87(3):503-521
We have performed a comparison of ten models that predict the temporal behavior of laser-induced incandescence (LII) of soot.
In this paper we present a summary of the models and comparisons of calculated temperatures, diameters, signals, and energy-balance
terms. The models were run assuming laser heating at 532 nm at fluences of 0.05 and 0.70 J/cm2 with a laser temporal profile provided. Calculations were performed for a single primary particle with a diameter of 30 nm
at an ambient temperature of 1800 K and a pressure of 1 bar. Preliminary calculations were performed with a fully constrained
model. The comparison of unconstrained models demonstrates a wide spread in calculated LII signals. Many of the differences
can be attributed to the values of a few important parameters, such as the refractive-index function E(m) and thermal and
mass accommodation coefficients. Constraining these parameters brings most of the models into much better agreement with each
other, particularly for the low-fluence case. Agreement among models is not as good for the high-fluence case, even when selected
parameters are constrained. The reason for greater variability in model results at high fluence appears to be related to solution
approaches to mass and heat loss by sublimation.
PACS 65.80.+n; 78.20.Nv; 42.62.-b; 44.05.+e 相似文献
127.
From the time of CMB decoupling onwards we investigate cosmological evolution subject to a strongly interacting SU(2) gauge
theory of Yang–Mills scale, Λ ∼ 10-4 eV (masquerading as the U(1)Y factor of the SM at present). The viability of this postulate is discussed in view of cosmological and (astro-) particle
physics bounds. The gauge theory is coupled to a spatially homogeneous and ultralight (Planck-scale) axion field. As first
pointed out by Frieman et al., such an axion is a viable candidate for quintessence, i.e. dynamical dark energy, being associated
with today’s cosmological acceleration. A prediction of an upper limit for Δtmγ=0, the duration of the epoch stretching from the present to the point where the photon starts to be Meissner massive, is obtained:
Δtmγ=0∼2.2 billion years. 相似文献
128.
J. Khuyagbaatar S. Hofmann F. P. Heßberger D. Ackermann S. Antalic H. G. Burkhard S. Heinz B. Kindler A. F. Lisetskiy B. Lommel R. Mann K. Nishio H. J. Schött B. Sulignano 《The European Physical Journal A - Hadrons and Nuclei》2007,34(4):355-361
Isomeric states in 214Th and 213Th were identified by means of γ -rays measured in delayed coincidence with the implanted evaporation residues. These were
produced in irradiations of 164Dy with 54Cr projectiles and separated in-flight by the velocity filter SHIP. An isomeric state of I
π = 8+ with a half-life of (1.24±0.12) μs was identified in 214Th . The configuration π[1h
9/2 ⊗ 2f
7/2] was assigned to this state. An isomeric state with a half-life of (1.4±0.4) μs was observed in 213Th . Tentatively it was assigned to an I
π = 13/2+ state. 相似文献
129.
S. Pisana M. Cantoro A. Parvez S. Hofmann A.C. Ferrari J. Robertson 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):1
Catalyst films undergo considerable surface morphology restructuring prior to carbon nanotube nucleation, deeply influencing the nanostructures obtained. Here we study the influence of different gaseous atmospheres on the structure of thin Fe films. The morphology is influenced by process temperature and substrate interactions and varying the gas type and pressure can control the average catalyst island height. 相似文献
130.