全文获取类型
收费全文 | 841篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
化学 | 601篇 |
晶体学 | 14篇 |
力学 | 11篇 |
数学 | 54篇 |
物理学 | 187篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 53篇 |
2011年 | 52篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 57篇 |
2007年 | 32篇 |
2006年 | 56篇 |
2005年 | 58篇 |
2004年 | 36篇 |
2003年 | 41篇 |
2002年 | 44篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1968年 | 3篇 |
1967年 | 4篇 |
排序方式: 共有867条查询结果,搜索用时 62 毫秒
1.
J. Kobayashi Y. Izumi M. Kumakura Y. Takahashi 《Applied physics. B, Lasers and optics》2006,83(1):21-25
By stabilizing the beam pointing of optical trapping beams, we have succeeded in stable formation of Bose–Einstein condensate
(BEC) of 87Rb with all-optical method. The thermal effect of acousto-optic modulator (AOM) is usually one of the most serious problems
to induce beam-pointing instability, especially for high power CO2 laser. By passing the beam through AOM twice, we have improved the beam pointing from about 4.8 mrad to less than 0.4 mrad,
which has been experimentally confirmed to be small enough to stably form BEC at the crossed region of CO2 lasers as well as to perform experiments using an optical lattice which might have been affected by beam-pointing instability.
PACS 32.80.Pj; 42.79.Jq; 03.75.Mn 相似文献
2.
Yasumitsu Matsuo Takehiko Ijichi Hironori Yamada Junko Hatori Seiichiro Ikehata 《Central European Journal of Physics》2004,2(2):357-366
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and
investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current
at around the coercive electric fieldE
c
of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET)
based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than
that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such
devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the
organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the
initial drain current ofE
G
=0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E
c
). From these results, it is suggested that the PEN-FET becomes a memory device. 相似文献
3.
4.
Yoshinori Nishiwaki Masahiko Shimoyama Toshio Nakanishi Toshio Ninomiya Izumi Nakai 《Analytical sciences》2006,22(10):1297-1300
Total reflection X-ray fluorescence spectrometry (TXRF) has been applied for trace elemental analysis of small glass fragments. A small glass sample (a fragment with weight less than 0.5 mg) was decomposed by 100 microg of HF/HNO3 acid; the material was condensed to 10 microl and was dried on a Si wafer. Since the size of the dried residue on the Si wafer was less than 1 cm in diameter, an incident X-ray beam with about 1 cm in width could effectively excite elemental components in such a small glass fragment. The precision of the present technique was checked by analyzing the glass fragments (<0.5 mg) from NIST SRM612; the relative standard deviations (RSD) of less than 8.1% were achieved for elemental ratios that were normalized by Sr. Fragments (<0.5 mg) obtained from 23 figured sheet glasses were used as samples for estimating the utility of this technique to forensic discrimination. Comparison of five elemental ratios of Ti/Sr, Mn/Sr, Zn/Sr, Rb/Sr, and Pb/Sr calculated from X-ray fluorescence spectra was effective in distinguishing glass fragments that could not be differentiated by their refractive indexes (RI). 相似文献
5.
Kazuhiko Nakano Toshihiro Nakamura Izumi Nakai Akira Kawase Makoto Imai Mikio Hasegawa Yohichi Ishibashi Isamu Inamoto Kazuhuyu Sudou Masaru Kozaki Akira Tsuruta Akihiro Ono Kazutoshi Kakita Mamoru Sakata 《Analytical sciences》2006,22(9):1265-1268
The Japan Society for Analytical Chemistry has developed some new plastic certified reference materials (CRMs) for the analysis of mercury in polyester disks using XRF analysis. These CRMs (named as JSAC 0621-0625) were prepared by casting polyesters including a toluene solution of organometallic compounds as a standard. Concentrations of the five levels of mercury ranged from 0 to 250 mg/kg. Homogeneity tests of prepared disks had shown excellent results. Interlaboratory comparison study for the certification was performed by 15 laboratory participants. The z-scores in robust statistical method was applied for the evaluation of outliers. The certified values were assigned after discarding outliers. The uncertainties of certified values were determined as the confidence levels of 95%. 相似文献
6.
7.
In order to investigate the interactions of poly(2-diethylaminoethyl methacrylate) (PDEAEMA) with methyl orange and its homologs in solution, temperature dependence of the complex formation has been examined in detail by the measurements of transmittance and specific conductance for the systems. Furthermore, the binding course of dyes to PDEAEMA has been studied on the basis of thermodynamic parameters obtained from equilibrium dialysis experiments at different temperatures. It was observed that the flocculation process shifted to lower dye concentrations in accordance with increasing hydrophobicity of the dyes in the order, methyl orange < ethyl orange < butyl orange, and the process of complex formation was characterized by three separate regions according to the slope of specific conductivity-mixing ratio curve for mixtures of PDEAEMA and dye. The temperature dependences of F,H and S suggest that, for dyes-PDEAEMA complex formation, the hydrophobic interaction is predominant at a low temperature but the electrostatic interaction becomes important as the temperature increases. 相似文献
8.
Yuasa H Izumi T Mitsuhashi N Kajihara Y Hashimoto H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6478-6490
Hinged di- and trisaccharides incorporating 2,4-diamino-beta-D-xylopyranoside as a hinge unit (Hin) were synthesized. Bridging of the diamino group of Hin by carbonylation or chelation to a metal ion results in a conformational change from (4)C1 to (1)C4, which in turn causes a bending of the oligosaccharides. In this study, the bending abilities of the hinged oligosaccharides were compared, in terms of the reactivities toward carbonylation and chelation. Di- or trisaccharides containing a 6-O-glycosylated mannopyranoside or galactopyranoside at their reducing ends had bending abilities similar to that of the Hin monosaccharide, probably because there were neither attractive nor repulsive interactions between the reducing and nonreducing ends. However, when Hin was attached at O2 of methyl mannopyranoside (Man alphaMe), the bending ability was dependent on the nonreducing sugar and the reaction conditions. Typically, a disaccharide--Hin beta(1,2)Man alphaMe--was difficult to bend under all the tested reaction conditions, and the bent population in the presence of Zn(II) was only 4%. On the other hand, a trisaccharide--Man alpha(1,3)Hin beta(1,2)Man alphaMe--was bent immediately after the addition of Zn(II) or Hg(II), and the bent population reached 75%, much larger than those of all the other hinged trisaccharides ever tested (<40%). This excellent bending ability suggests an attractive interaction between the reducing and nonreducing ends. The extended conformation was recovered by the addition of triethylenetetramine, a metal ion chelator. Reversible, quick, and efficient bending of the hinged trisaccharide was thus achieved. 相似文献
9.
Mingdeng Wei Kiyomi Okabe Hironori Arakawa Yesutake Teraoka 《Reaction Kinetics and Catalysis Letters》2002,77(2):381-387
SiO2 was modified by hexagonal mesoporous silica to form a mixture with meso-/macroporous sizes and used as support of Co catalysts for Fischer-Tropsch synthesis in a slurry phase. A synergistic effect on the activity of Co catalyst was found. The catalytic properties are related to the state of surface Co and the character of support. 相似文献
10.
2,3-Dideoxy-3-fluoro-α-d-ribose 1-phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β-d-guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1. 相似文献