全文获取类型
收费全文 | 268991篇 |
免费 | 6351篇 |
国内免费 | 3626篇 |
专业分类
化学 | 151393篇 |
晶体学 | 3697篇 |
力学 | 10522篇 |
综合类 | 220篇 |
数学 | 31666篇 |
物理学 | 81470篇 |
出版年
2021年 | 2472篇 |
2020年 | 2890篇 |
2019年 | 2941篇 |
2018年 | 3528篇 |
2017年 | 3584篇 |
2016年 | 5339篇 |
2015年 | 3982篇 |
2014年 | 5371篇 |
2013年 | 11877篇 |
2012年 | 10643篇 |
2011年 | 12512篇 |
2010年 | 8765篇 |
2009年 | 8280篇 |
2008年 | 11417篇 |
2007年 | 11192篇 |
2006年 | 10512篇 |
2005年 | 9514篇 |
2004年 | 8403篇 |
2003年 | 7248篇 |
2002年 | 7041篇 |
2001年 | 7616篇 |
2000年 | 5835篇 |
1999年 | 4248篇 |
1998年 | 3517篇 |
1997年 | 3453篇 |
1996年 | 3575篇 |
1995年 | 3119篇 |
1994年 | 3240篇 |
1993年 | 3088篇 |
1992年 | 3368篇 |
1991年 | 3276篇 |
1990年 | 3065篇 |
1989年 | 2959篇 |
1988年 | 2859篇 |
1987年 | 2812篇 |
1986年 | 2812篇 |
1985年 | 3757篇 |
1984年 | 3784篇 |
1983年 | 3165篇 |
1982年 | 3429篇 |
1981年 | 3189篇 |
1980年 | 2966篇 |
1979年 | 3154篇 |
1978年 | 3337篇 |
1977年 | 3368篇 |
1976年 | 3377篇 |
1975年 | 3109篇 |
1974年 | 3203篇 |
1973年 | 3209篇 |
1972年 | 2458篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
A. N. Vasiliev V. N. Grishin A. M. Davidenko A. A. Derevschikov Yu. A. Matulenko Yu. M. Melnik A. P. Meschanin V. V. Mochalov L. V. Nogach S. B. Nurushev A. F. Prudkoglyad P. A. Semenov L. F. Soloviev V. L. Solovianov V. Yu. Khodyrev K. E. Shestermanov A. E. Yakutin N. S. Borisov V. N. Matafonov A. B. Neganov Yu. A. Plis Yu. A. Usov A. N. Fedorov A. A. Lukhanin 《Physics of Atomic Nuclei》2004,67(8):1487-1494
Results are presented that were obtained by measuring single-spin asymmetry in the inclusive production of neutral pions in the reaction p+p ↑→ π 0+X at x F≈0. A beam of 70-GeV protons was extracted directly from the vacuum chamber of the accelerator by means of a bent single crystal. For transverse momenta in the range 1.0<p T<3.0 GeV/c, the single-spin asymmetry independently measured by two detectors is zero within the errors. This result is in agreement with Fermilab data obtained at 200 GeV, but it is at odds with CERN data measured at 24 GeV. 相似文献
962.
A. N. Enyashin V. V. Ivanovskaya Yu. N. Makurin A. L. Ivanovskii 《Physics of the Solid State》2004,46(8):1569-1573
A comparative analysis of the stability factors and electronic structure of two possible crystalline forms of small fullerene C28 and endohedral fullerene Zn@C28 with diamond and lonsdaleite structures is performed using a cluster model. Atoms of elements that, when placed inside C28 cages, have no significant effect on the stability of free small-fullerene molecules are shown to be able to dramatically change the electronic properties and reactivity of the C28 skeleton and to be favorable for forming small-fullerene crystalline modifications, which are covalent crystals. In contrast, if the presence of foreign atoms inside C28 cages stabilizes the isolated nanoparticles, then molecular crystals (such as C60 fullerites) are formed due to weak van der Waals forces. 相似文献
963.
964.
G. M. Ter-Akopian A. V. Daniel A. S. Fomichev G. S. Popeko A. M. Rodin Yu. Ts. Oganessian J. H. Hamilton A. V. Ramayya J. Kormicki J. K. Hwang D. Fong P. Gore J. D. Cole M. Jandel J. Kliman L. Krupa J. O. Rasmussen I. Y. Lee A. O. Macchiavelli P. Fallon M. A. Stoyer R. Donangelo S. -C. Wu W. Greiner 《Physics of Atomic Nuclei》2004,67(10):1860-1865
Ternary fission of 252Cf was studied at Gammasphere using eight ΔE×E particle telescopes. Helium, beryllium, boron, and carbon light charged particles (LCPs) emitted with kinetic energy more than 9, 21, 26, and 32 MeV, respectively, were identified. The 3368-keV γ transition from the first 2+ excited state in 10Be was found and the population probability ratio N(2+)/N(0+) = 0.160 ± 0.025 was estimated. No evidence was found for 3368-keV γ rays emitted from a triple molecular state. For the first time, charge distributions are obtained for ternary fission fragments emitted with helium, beryllium, and carbon LCPs. 相似文献
965.
The crystallization of nickel nanoclusters is investigated using a molecular dynamics simulation with tight-binding potentials. The formation of a cluster structure depends on the cooling conditions. Slow cooling results in the formation of a face-centered cubic structure, whereas fast cooling, according to the data obtained in 40% of the simulation experiments, leads to the formation of an icosahedral structure. The molecular dynamics simulation experiments demonstrate the possibility of controlling the formation of a structure of nickel nanoclusters during crystallization. 相似文献
966.
967.
M. L. Bonardi C. Birattari F. Groppi L. Gini H. S. C. Mainardi 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):415-419
Radionuclides of very high specific activity A
S(t) have great relevance for applications in the life sciences. Updated definitions of A
S are given. The real A
S(t) must be measured by analytical and radioanalytical techniques. No-carrier-added (NCA) radionuclides have A
S(NCA) sometimes close to the carrier-free (CF) value A
S(CF). The accurate knowledge of excitation functions of nuclear reactions vs. ion beam energy is mandatory to maximize A
S(NCA); the minimization of isotopic dilution factor IDF(t) has been achieved too. A range of accelerator production and radioanalytical QC methods for A
S(NCA) optimization and determination is presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
968.
Processes of the inelastic magnetic and weak scattering of tritium-beta-source antineutrinos on the bound electrons of a germanium atom are considered. The results obtained by calculating the spectra and cross sections are presented for the energy-transfer range between 10 eV and 18 keV. 相似文献
969.
The reactions of bis(trimethylstannyl)ethyne, Me3Sn–C?C–SnMe3 ( 4 ), with trimethylsilyl‐ or dimethylsilyl‐dialkylboryl‐substituted alkenes 1 – 3 afford organometallic‐substituted allenes 5 , 6 and 8 , 9 in high yield. In the case of (E)‐2‐trimethylsilyl‐3‐diethylboryl‐2‐pentene ( 1) , a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by 29Si and 119Sn NMR, and the products were characterized by an extensive NMR data set (1H, 11B, 13C, 29Si, 119Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
970.
K. Popov-Pergal L. Cuckovic M. Rancic M. Pergal D. Djokovic 《Chemistry of Heterocyclic Compounds》2003,39(8):1090-1093
A series of methyl 2-(arylidene-2,4-dioxotetrahydrothiazol-3-yl)propionates were prepared. A study of the 3D structure was performed. The log P values are given for all the synthesized compounds. 相似文献