全文获取类型
收费全文 | 1325篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
化学 | 962篇 |
晶体学 | 24篇 |
力学 | 11篇 |
数学 | 74篇 |
物理学 | 315篇 |
出版年
2023年 | 9篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 19篇 |
2017年 | 8篇 |
2016年 | 29篇 |
2015年 | 28篇 |
2014年 | 38篇 |
2013年 | 40篇 |
2012年 | 65篇 |
2011年 | 62篇 |
2010年 | 45篇 |
2009年 | 35篇 |
2008年 | 79篇 |
2007年 | 64篇 |
2006年 | 75篇 |
2005年 | 56篇 |
2004年 | 46篇 |
2003年 | 58篇 |
2002年 | 39篇 |
2001年 | 42篇 |
2000年 | 35篇 |
1999年 | 24篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 30篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 13篇 |
1973年 | 8篇 |
1969年 | 8篇 |
1968年 | 8篇 |
1966年 | 8篇 |
排序方式: 共有1386条查询结果,搜索用时 156 毫秒
101.
Yusuke Arai Tetsuji Yano Shuichi Shibata 《Journal of Sol-Gel Science and Technology》2004,32(1-3):189-194
Microspheres of refractive index of nD > 2.0 have been investigated. The organic-inorganic hybrid microspheres of nD = 1.72 were prepared by the vibrating orifice technique using titanium-tetra-n-butoxide (TTBu) and diphenyldimethoxysilane (DPhDMS). For lasing demonstration, Eu3+-doped microspheres were prepared using europium (III) thenoyltrifluoroacetonate [Eu(TTFA)3] as the dopant. The particles have good spherical shape, smooth surface and high optical transparency. The diameters of the particles could be controlled to within 0.1 m. Subsequent heating of the microspheres at 550°C under oxygen atmosphere resulted in an increase in the refractive index up to nD = 2.6 with retention of the spherical shape. Resonant emission was confirmed from Eu3 +-doped microspheres after heating at 400–550°C, by pumping with the 514.5 nm line of a CW- Ar+laser. 相似文献
102.
Li G Dobhal MP Graham A Shibata M Zheng G Kozyrev A Pandey RK 《The Journal of organic chemistry》2003,68(10):3762-3772
The thermolysis products obtained by refluxing a series of vic-dihydroxychlorins in o-dichlorobenzene are characterized. Depending on the nature of substrates, this methodology provides an access for novel carbon-carbon linked chlorin-chlorin dimers and chlorin-porphyrin dimers with fixed and flexible orientations. The configuration of the linkers in the symmetrical and unsymmetrical dimers was confirmed by extensive NMR (COSY, ROESY) and molecular modeling studies. The molecular modeling studies of the energy-optimized dimers with flexible orientation confirmed that one of the chlorin units of the dimeric structure is tilted toward the opposite ring as evident by the shielding effect in the resonances of some of the protons in the (1)H NMR spectroscopy. Among the dimers with fixed orientation, compared to the free-base analogues, the related mono- and di-Zn(II) complexes produced a decreased fluorescence intensity, suggesting a possibility of the faster energy transfer via intersystem crossing (ISC) in the metalated derivatives than the corresponding free-base analogues to produce the corresponding excited triplet states. The photosensitizing efficacy of the monomers and the related dimers was also compared in radiation-induced fibrosarcoma (RIF) tumor cells at variable drug/light doses. In preliminary screening, compared to monomers, the corresponding carbon-carbon linked dimers produced enhanced photosensitizing efficacy. 相似文献
103.
104.
Tetsutaro Shibata 《Journal of Mathematical Analysis and Applications》2003,283(2):431-439
We consider the nonlinear eigenvalue problem on an interval
105.
Eisenstein BI Ernst J Gladding GE Gollin GD Hans RM Johnson E Karliner I Marsh MA Plager C Sedlack C Selen M Thaler JJ Williams J Edwards KW Sadoff AJ Ammar R Bean A Besson D Zhao X Anderson S Frolov VV Kubota Y Lee SJ Poling R Smith A Stepaniak CJ Urheim J Ahmed S Alam MS Athar SB Jian L Ling L Saleem M Timm S Wappler F Anastassov A Eckhart E Gan KK Gwon C Hart T Honscheid K Hufnagel D Kagan H Kass R Pedlar TK Thayer JB von Toerne E Zoeller MM Richichi SJ Severini H Skubic P Undrus A Savinov V 《Physical review letters》2001,87(6):061801
Using 12.7 fb(-1) of data collected with the CLEO detector at CESR, we observed two-photon production of the cc states chi(c0) and chi(c2) in their decay to pi(+)pi(-)pi(+)pi(-). We measured gamma(gammagamma)(chi(c))xB(chi(c)-->pi(+)pi(-)pi(+)pi(-)) to be 75+/-13(stat)+/-8(syst) eV for the chi(c0) and 6.4+/-1.8(stat)+/-0.8(syst) eV for the chi(c2), implying gamma(gammagamma)(chi(c0)) = 3.76+/-0.65(stat)+/-0.41(syst)+/-1.69(br) keV and gamma(gammagamma)(chi(c2)) = 0.53+/-0.15(stat)+/-0.06(syst)+/-0.22(br) keV. Also, cancellation of dominant experimental and theoretical uncertainties permits a precise comparison of gamma(gammagamma)(chi(c0))/gamma(gammagamma)(chi(c2)), evaluated to be 7.4+/-2.4(stat)+/-0.5(syst)+/-0.9(br), with QCD-based predictions. 相似文献
106.
Ammar R Bean A Besson D Davis R Kwak N Zhao X Anderson S Frolov VV Kubota Y Lee SJ Mahapatra R O'Neill JJ Poling R Riehle T Smith A Stepaniak CJ Urheim J Ahmed S Alam MS Athar SB Jian L Ling L Saleem M Timm S Wappler F Anastassov A Duboscq JE Eckhart E Gan KK Gwon C Hart T Honscheid K Hufnagel D Kagan H Kass R Pedlar TK Schwarthoff H Thayer JB von Toerne E Zoeller MM Richichi SJ Severini H Skubic P Undrus A Chen S Fast J Hinson JW Lee J Miller DH Shibata EI Shipsey IP Pavlunin V 《Physical review letters》2001,86(7):1167-1170
Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the Sigma(*+)(c) charmed baryon, and an updated measurement of the mass of the Sigma(+)(c) baryon. We find M(Sigma(*+)(c))-M(Lambda(+)(c)) = (231.0+/-1.1+/-2.0) MeV, and M(Sigma(+)(c))-M(Lambda(+)(c)) = (166.4+/-0.2+/-0.3) MeV, where the errors are statistical and systematic, respectively. 相似文献
107.
H. Hayashi Y. Akita O. Suematsu M. Shibata M. Asai T. K. Sato S. Ichikawa I. Nishinaka Y. Nagame A. Osa K. Tsukada T. Ishii Y. Kojima A. Taniguchi 《The European Physical Journal A - Hadrons and Nuclei》2007,34(4):363-370
Q
β values of the neutron-rich isotopes of 160-165Eu and 163Gd were measured for the first time using a total absorption bismuth germanate (BGO) detector, and previously obtained data
on 158, 159Pm , 159, 161Sm and 166Tb were re-analyzed. These radioactive sources were prepared by an on-line mass separator (Tokai-ISOL) following the 238U (p,f reaction. The deduced Q
β values are the following: 6085(80)keV for 158Pm , 3805(65)keV for 159Sm , 5460(140)keV for 159Pm , 4705(60)keV for 160Eu , 5065(130)keV for 161Sm , 3705(60)keV for 161Eu , 5575(60)keV for 162Eu , 4690(70)keV for 163Eu , 3170(70)keV for 163Gd , 6430(70)keV for 164Eu , 5800(120)keV for 165Eu , and 4695(70)keV for 166Tb . Moreover, the deduced mass excesses and two-neutron separation energies ( S
2n values) were compared with those of the atomic mass evaluations and theoretical predictions. 相似文献
108.
描述了如何使用蒙特卡罗方法评估产生在加速器屏蔽混凝土中的感生放射性. 使用EGS4程序模拟了NaI闪烁探测器测量屏蔽混凝土块表面剂量率时, 对于半径和厚度的响应. 结果发现,在屏蔽混凝土块半径和厚度分别达到40cm和30cm时, 表面剂量率达到饱和. 研究了东京大学SF回旋加速器北墙位置8和位置9的表面剂量率, 并和使用NaI闪烁探测器的测量结果进行了对比, 发现模拟和实验结果符合很好. 并且, 获得了表面剂量和表面感生放射性之间的转换系数, 对于60Co转换系数为0.90(Bq·g-1)·(μSv·h-1)-1, 对于152Eu转换系数为1.26(Bq·g-1)·(μSv·h-1)-1. 这样, 就可以通过NaI闪烁探测器表面剂量的测量结果简单评估加速器设备屏蔽混凝土中的感生放射性. 相似文献
109.
110.