全文获取类型
收费全文 | 1716篇 |
免费 | 71篇 |
国内免费 | 6篇 |
专业分类
化学 | 1439篇 |
晶体学 | 24篇 |
力学 | 16篇 |
数学 | 70篇 |
物理学 | 244篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 13篇 |
2020年 | 18篇 |
2019年 | 37篇 |
2018年 | 20篇 |
2017年 | 13篇 |
2016年 | 44篇 |
2015年 | 35篇 |
2014年 | 59篇 |
2013年 | 72篇 |
2012年 | 101篇 |
2011年 | 118篇 |
2010年 | 77篇 |
2009年 | 53篇 |
2008年 | 119篇 |
2007年 | 113篇 |
2006年 | 115篇 |
2005年 | 128篇 |
2004年 | 115篇 |
2003年 | 98篇 |
2002年 | 68篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1988年 | 7篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 3篇 |
排序方式: 共有1793条查询结果,搜索用时 0 毫秒
81.
82.
83.
Virginie Gueu Hongpeng You Tomokatsu Hayakawa Masayuki Nogami 《Journal of Sol-Gel Science and Technology》2007,41(3):231-236
Fluorescence and spectral hole burning properties of Eu3+ ions were studied in nanocrystals-precipitated SnO2-SiO2 glasses. The glasses were prepared to contain various amount of Eu2O3 using the sol-gel method, in which SnO2 nanocrystals were precipitated by heating in air. In the glasses containing Eu2O3 less than 1%, the Eu3+ ions were preferentially doped in the SnO2 nanocrystals and their fluorescence intensities were enhanced by the energy transfer due to the recombination of electrons
and holes excited in SnO2 crystals. The SnO2 nanocrystals-precipitated glasses exhibited the persistent spectral holes with the depth of ∼25% of the total fluorescence
intensities of the Eu3+ ions. With the increasing Eu2O3 concentration, the amount of SnO2 nanocrystals decreased and the Sn4+ ions formed the random glass structure together with the silica network. This structure change induced the fluorescence intensities
and the hole depth to decrease. 相似文献
84.
Dr. Masayuki Iwasaki Miki Iyanaga Yuta Tsuchiya Yugo Nishimura Wenjuan Li Prof. Dr. Zhiping Li Prof. Dr. Yasushi Nishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2459-2462
A catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co‐catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a PdII/PdIV mechanism. 相似文献
85.
Abstract Bacteriochlorophyll d analogues that possessed a series of bulky substituents of OMe, OCOMe, and OCO t Bu at the C71-position were synthesized (Zn-complexes of methyl 71-substituted-3-(1-hydroxy-methyl)pyropheophorbide a). Aggregation behavior of these pigments was examined in comparison with a natural-type compound (C71-H) to elucidate the effects of size of the C71-moiety on self-assembly of the chlorins. These C71-substituted Zn-chlorins formed self-aggregates in 1% THF/hexane. The aggregates gave almost the same visible absorption bands, especially a ca. 2000-cm?1 red-shifted Qy peak; the spectra were essentially similar to those of the natural-type Zn-chlorin (C71-H). All the aggregates of the C71-substituted compounds showed similar exciton-type CD couplets in the red-shifted Qy region, which were different from the feature of the couplet of the C71-H Zn-chlorin aggregate. These spectral data suggested that the C71-moiety did not interrupt the intermolecular linkages between chlorin molecules but altered the supramolecular structure which influences the long-range chirality. 相似文献
86.
87.
Masayuki Kirihara Takuya Noguchi Nobuhiro Okajima Sayuri Naito Yuki Ishizuka Aiko Harano Hiroyuki Tsukiji Ryu Takizawa 《Tetrahedron》2012,68(5):1515-1520
The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions. 相似文献
88.
89.
Masayuki Hagiwara Shojiro Kimura Haruhiko Yashiro Takanari Kashiwagi Hironori Yamaguchi Koichi Kindo 《Applied magnetic resonance》2009,36(2-4):269-274
We have developed high-field and multifrequency (HFMF) electron spin resonance (ESR) apparatus for the magnetic fields up to 65 T at frequencies up to about 6 THz. In addition to this pulsed field ESR apparatus, we are making a multifrequency ESR apparatus with very high sensitivity in a static field. We report the results of ESR studies on BaCoV2O8 and NiGa2S4, followed by recent developments and future plans of our HFMF ESR apparatus. 相似文献
90.
Makoto Uchimura Ryohei Ishige Masayuki Shigeta Yuki Arakawa Yosuke Niko Junji Watanabe Gen-Ichi Konishi 《Research on Chemical Intermediates》2013,39(1):403-414
We synthesized thermotropic liquid-crystalline polyesters in which 9,10-diphenylanthracene moieties are incorporated into the main chain type of polyester forming the chiral smectic C (Sm C*). The polymers were prepared by the isopropyltitanate-catalyzed reaction of biphenyldicarboxylic acid and the corresponding diols, with different ratios of diol of 9,10-diphenylanthracene moiety to the alkane diols (1, 5, and 10 mol %) under nitrogen atmosphere. The polymers exhibited thermotropic liquid crystals despite the presence of a bulky diphenylanthracene moiety in the main chain. The circular dichroism spectra revealed that a Sm C* phase was formed in the polymer with 1 mol % of anthracene moiety, although only an Sm A phase was formed in the other polymers. This is the first example of a Sm C* polyester containing a diphenylanthracene moiety in the main chain. Furthermore, we measured the optical properties of the polymers and found that they exhibited very high fluorescent efficiency. The fluorescence spectra of the thin film differed from that of a CH2Cl2 solution. 相似文献