全文获取类型
收费全文 | 1349篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
化学 | 1039篇 |
晶体学 | 18篇 |
力学 | 29篇 |
数学 | 62篇 |
物理学 | 246篇 |
出版年
2023年 | 5篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 25篇 |
2015年 | 20篇 |
2014年 | 25篇 |
2013年 | 55篇 |
2012年 | 50篇 |
2011年 | 63篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 75篇 |
2007年 | 76篇 |
2006年 | 88篇 |
2005年 | 69篇 |
2004年 | 84篇 |
2003年 | 77篇 |
2002年 | 58篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1986年 | 13篇 |
1985年 | 29篇 |
1984年 | 29篇 |
1983年 | 5篇 |
1982年 | 19篇 |
1981年 | 29篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 24篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1972年 | 7篇 |
1971年 | 7篇 |
排序方式: 共有1394条查询结果,搜索用时 62 毫秒
1.
Dr. Masaru Kondo Dr. Shinobu Takizawa Yuzhao Jiang Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9866-9869
The Mills reaction and cyclization of readily available 2-aminobenzyl alcohols and nitrosobenzenes using thionyl bromide provided 2H-indazoles in up to 88 % yields. In the metal-free process, acetic acid played a crucial role for the both Mills reaction and cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence. 相似文献
2.
Sonoko Kikuchi Kazuteru Kawauchi Sadatsugu Ooki Masaru Kurosawa Hisashi Honjho Teruo Yagishita 《Analytical sciences》2004,20(8):1111-1112
Using Raman spectroscopy without any preparation, we analyzed the brominated flame retardant, polybromodiphenyl ethers (PBDEs), which has been prohibited by the European Union. The typical Raman bands of PBDEs, which are clearly different from those of other brominated flame retardants, are from 100 to 300 cm(-1). In our analysis, the detection limit was about 100 ppm, and the analysis took about 1 min, whereas the usual method of solvent extraction using gas chromatography/mass spectroscopy takes 50 h. 相似文献
3.
Masaharu Asano Jinhua Chen Yasunari Maekawa Takahiro Sakamura Hitoshi Kubota Masaru Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2624-2637
A novel process comprising the UV‐induced photografting of styrene into poly(tetrafluoroethylene) (PTFE) films and subsequent sulfonation has been developed for preparing proton‐conducting membranes. Although under UV irradiation the initial radicals were mainly generated on the surface of the PTFE films by the action of photosensitizers such as xanthone and benzoyl peroxide, the graft chains were readily propagated into the PTFE films. The sulfonation of the grafted films was performed in a chlorosulfonic acid solution. Fourier transform infrared and scanning electron microscopy were used to characterize the grafted and sulfonated membranes. With a view to use in fuel cells, the proton conductivity, water uptake, and mechanical properties of the prepared membranes were measured. Even through the degree of grafting was lower than 10%, the proton conductivity in the thickness direction of the newly prepared membranes could reach a value similar to that of a Nafion membrane. In comparison with γ‐ray radiation grafting, UV‐induced photografting is very simple and safe and is less damaging to the membranes because significant degradation of the PTFE main chains can be avoided. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2624–2637, 2007 相似文献
4.
Hiroyasu Nishiguchi Hiroshi Yamada Masaru Ogura Tatsumi Ishihara Yusaku Takita 《Research on Chemical Intermediates》2003,29(7-9):755-760
The oxygen storage capacity of CeO2, Ce0.9Pr0.1O2, Pt?Rh/CeO2 and Pt?Rh/Ce0.9Pr0.1O2 was investigated by conventional GC pulse method and transient pulse techniques. It is shown that incorporation of PrOy into CeO2 matrix strongly promotes oxygen storage capacity (OSC) measured using the transient pulse technique. The improvement of OSC at low temperature is observed in Pt?Rh loaded onto CeO2 and Ce?Pr catalysts. 相似文献
5.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. E. Stronach M. Davis S. Uchida H. Takagi Y. Tokura Y. Hidaka T. Murakami E. A. Early J. T. Markert M. B. Maple C. L. Seaman 《Hyperfine Interactions》1991,63(1-4):311-317
We report muon spin relaxation/rotation measurements on sintered powder samples of Nd2−x
Ce
x
CuO4−y
and a large single crystal of Nd2CuO4−y
. We find an electronic phase diagram which is quite similar to that of hole-doped superconductors such as La2−x
Sr
x
CuO4−y
, although the doping of electrons into the system is less efficient in destroying the static moments on the copper spins.
Static magnetic order in Nd2CuO4−y
appears below about 250 K, and two spin reorientations are seen atT=75 K andT=35 K. Measurements of the magnetic field penetration depth have been unsuccessful due to the rare-earth paramagnetism of
these materials. 相似文献
6.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. L. Seaman Y. Dalichaouch M. B. Maple J. D. Garrett 《Hyperfine Interactions》1991,64(1-4):517-522
We have performed both zero field and high transverse field measurements at dilution refrigerator temperatures on a number of heavy electron systems, examining the superconducting and magnetic properties of these interesting materials. Among the materials studied to date are UBe13, URu2Si2 and U6Fe. The magnetic field penetration depth in the superconducting state of UBe13 is greater than 10000 Å, as no increase in the transverse field relaxation rate is observed belowT c . A sharp increase in the precession frequency is seen, starting atT c . This frequency shift shows little temperature dependence at low temperature; we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we have observed relaxation in high transverse field due to the formation of a flux lattice in U6Fe, a material where the electron effective mass is rather lighter than in other heavy fermion systems. The relaxation exhibits a sharp onset atT c=3.9 K, and is flat at low temperatures as expected for a conventional superconductor. 相似文献
7.
8.
9.
Masaru FukushimaTakashi Ishiwata 《Journal of Molecular Spectroscopy》2002,216(1):159-165
We have generated MgNC in supersonic free jet expansions and measured the laser-induced fluorescence excitation spectra of the C-N stretching vibronic bands of the Ã2Π-X?2Σ+ transition. Rotational analysis yields the molecular constants of the vibronic levels, (1,0,0) and (1,0,1), in the Ã2Π state. We cannot find any anomalies in the constants of these vibronic levels, while they are predicted to lie above the barrier of the isomerization reaction pathway, MgNC↔MgCN, on the Ã2Π state. On the basis of the molecular constants obtained, we discuss the fine structures of both the ground X?2Σ+ and excited Ã2Π states. 相似文献
10.
The pentafluorobenzenethiyl radical is an efficient hydrogen abstractor from an activated methylene or methine group and bis(pentafluorophenyl) disulfide is an efficient electron acceptor from the resulting radical intermediate. Thus benzyl-OTBS ether was easily converted into the corresponding pinacol, and 2-phenyl-1,3-dioxanes are converted into the monobenzoates of diols. 相似文献