全文获取类型
收费全文 | 126042篇 |
免费 | 1810篇 |
国内免费 | 146篇 |
专业分类
化学 | 69633篇 |
晶体学 | 1518篇 |
力学 | 4313篇 |
综合类 | 1篇 |
数学 | 15242篇 |
物理学 | 37291篇 |
出版年
2021年 | 1235篇 |
2020年 | 1561篇 |
2019年 | 1517篇 |
2018年 | 2088篇 |
2017年 | 2167篇 |
2016年 | 3303篇 |
2015年 | 1972篇 |
2014年 | 2794篇 |
2013年 | 5576篇 |
2012年 | 4728篇 |
2011年 | 5515篇 |
2010年 | 3850篇 |
2009年 | 3653篇 |
2008年 | 5120篇 |
2007年 | 4930篇 |
2006年 | 4590篇 |
2005年 | 4080篇 |
2004年 | 3544篇 |
2003年 | 3212篇 |
2002年 | 3201篇 |
2001年 | 3164篇 |
2000年 | 2463篇 |
1999年 | 1888篇 |
1998年 | 1676篇 |
1997年 | 1582篇 |
1996年 | 1586篇 |
1995年 | 1454篇 |
1994年 | 1460篇 |
1993年 | 1532篇 |
1992年 | 1518篇 |
1991年 | 1396篇 |
1990年 | 1416篇 |
1989年 | 1360篇 |
1988年 | 1312篇 |
1987年 | 1266篇 |
1986年 | 1182篇 |
1985年 | 1469篇 |
1984年 | 1593篇 |
1983年 | 1361篇 |
1982年 | 1424篇 |
1981年 | 1304篇 |
1980年 | 1228篇 |
1979年 | 1264篇 |
1978年 | 1413篇 |
1977年 | 1388篇 |
1976年 | 1229篇 |
1975年 | 1196篇 |
1974年 | 1198篇 |
1973年 | 1176篇 |
1967年 | 867篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献
112.
113.
D. Fong J. H. Hamilton A. V. Ramayya J. K. Hwang C. Goodin K. Li J. Kormicki J. O. Rasmussen Y. X. Luo S. C. Wu I. Y. Lee A. V. Daniel G. M. Ter-Akopian G. S. Popeko A. S. Fomichev A. M. Rodin Yu. Ts. Oganessian M. Jandel J. Kliman L. Krupa J. D. Cole M. A. Stoyer R. Donangelo W. C. Ma 《Physics of Atomic Nuclei》2006,69(7):1161-1167
The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be
Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the
“hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode.
The text was submitted by the authors in English. 相似文献
114.
115.
O.G. Kosareva N.A. Panov N. Akozbek V.P. Kandidov Q. Luo S.A. Hosseini W. Liu J.-F. Gravel G. Roy S.L. Chin 《Applied physics. B, Lasers and optics》2006,82(1):111-122
We demonstrate a three orders of magnitude increase and stability in the backscattered fluorescence signal from nitrogen molecules
by terawatt femtosecond laser pulse induced air filaments using a new method. The method is based on squeezing the initial
beam diameter using a telescope. The effect of laser shot-to-shot fluctuations was included in numerical simulations by a
random distribution of the initial intensity in both squeezed and non-squeezed beams. Statistical processing of the simulation
results shows that the average diameter of plasma channels as well as the total amount of free electrons generated in a bunch
of multiple filaments in air is larger in the squeezed beam. Shot-to-shot stability of the simulated plasma density increases
in the squeezed beam. The change of this plasma density with propagation distance is in good qualitative agreement with the
change of the range-corrected nitrogen fluorescence signal with distance.
PACS 42.65.Jx; 42.60.Jf; 42.68.Ay; 42.68.Wt 相似文献
116.
Inverse diffusion problems allow the diffusion coefficients to be determined from experimental concentration profiles. Solutions
of the inverse diffusion problem are unstable toward perturbations of the initial concentration profiles. By the example of
inverse diffusion problem solution for a model binary system it is demonstrated that the use of the production entropy to
minimize the discrepancy functional stabilizes the solution even for significant perturbations of the initial concentration
profile. The choice of the entropy production for the smoothing component of the discrepancy functional is physically adequate
to the formulated problem, and the entropy production can be used to solve inverse problems of heat and mass transfer.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 79–83, June, 2006. 相似文献
117.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
118.
O. A. Zmeev 《Russian Physics Journal》2003,46(3):318-324
In the present work, the diffusion approximation of the capital is constructed for the mathematical model of a social insurance fund with random expenditures for social programs. The discontinuous hysteresis control of the fund capital is considered. 相似文献
119.
Hyperfine Interactions - In this paper, the conditions for which three-dimensional crystalline ion beams were attained in the rf quadrupole storage ring PALLAS at a velocity of around 2800 m/s are... 相似文献
120.
Faitel'son E. A. Korkhov V. P. Aniskevich A. N. Starkova O. A. 《Mechanics of Composite Materials》2004,40(1):57-66
The results of a complex study of structural changes in a cured Norpol 440 polyester resin under the action of damp environment and mechanical loading are presented. A considerable effect of absorbed moisture on the structure and some characteristics of the material is revealed by using thermophysical methods and X-ray diffractometry. The joint effect of moisture and mechanical stress is estimated by investigating the creep in stationary and nonstationary moisture conditions. The anisotropy of the material structure formed during creep is evaluated from the results of dilatometric measurements. It is found that the degree of anisotropy of the material after creep accompanied by moisture sorption is higher than that after creep in the conditions of moisture equilibrium with atmosphere. It is established that the aftercure and relaxation of the residual creep deformation come to an end at heating to 80-85°C. At a further rise in temperature and repeated heating, changes in the material structure are not observed. 相似文献