全文获取类型
收费全文 | 619篇 |
免费 | 34篇 |
国内免费 | 8篇 |
专业分类
化学 | 572篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 6篇 |
物理学 | 74篇 |
出版年
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 54篇 |
2011年 | 38篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 49篇 |
2007年 | 33篇 |
2006年 | 42篇 |
2005年 | 36篇 |
2004年 | 40篇 |
2003年 | 36篇 |
2002年 | 26篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有661条查询结果,搜索用时 15 毫秒
81.
Benzynes were generated from o-(trimethylsilyl)phenols using nonafluorobutanesulfonyl fluoride (NfF) by a domino process, i.e., the nonaflation of the phenolic hydroxyl group of o-(trimethylsilyl)phenols by NfF followed by the attack of the produced fluoride ion on the trimethylsilyl group. The generated benzyne immediately underwent various reactions to give polysubstituted benzenes. 相似文献
82.
Matsumoto T Itakura N Nakaya Y Tatsumi K 《Chemical communications (Cambridge, England)》2011,47(3):1030-1032
A S/SH bridged hetero-dinuclear Ru/Ge complex cation reacted with H(2) to afford the μ-S/μ-H complex. The reaction was considerably slower compared to that of the μ-S/μ-OH complex. Thus, the μ-S/μ-SH and μ-S/μ-OH complexes might provide models for the unready and ready states, respectively, of [NiFe] hydrogenase. 相似文献
83.
Yokoi T Sakuma J Maeda K Domen K Tatsumi T Kondo JN 《Physical chemistry chemical physics : PCCP》2011,13(7):2563-2570
The confined space synthesis method has been applied to the preparation of sodium tantalate (NaTaO(3)); hydrothermal reaction of NaOH and Ta(2)O(5) was carried out in the pores of a three-dimensional mesoporous carbon, which was replicated by the colloidal array of silica nanospheres (SNSs) 20 nm in size. This approach led to the formation of a colloidal array of NaTaO(3) nanoparticles 20 nm in size with a surface area of 34 m(2) g(-1). The photocatalytic performance of the colloidal array of NaTaO(3) nanoparticles for overall water splitting under UV irradiation (λ > 200 nm) was evaluated after loading a NiO cocatalyst onto NaTaO(3) samples. The NiO-loaded NaTaO(3) nanoparticles showed photocatalytic activity for overall water splitting more than three times as high as non-structured bulk NaTaO(3) particles. 相似文献
84.
Toshifumi Inouchi Dr. Takuya Nakashima Dr. Masaya Toba Prof. Tsuyoshi Kawai 《化学:亚洲杂志》2011,6(11):3020-3027
T‐shaped π‐conjugated molecules with an N‐methyl‐benzimidazole junction have been synthesized and their acid‐responsive photophysical properties owing to the change in the π‐conjugation system are discussed. T‐shaped π‐conjugated molecules consist of two orthogonal π‐conjugated systems including a phenyl thiophene extended from the 2‐position and alkyl phenylenes connected through various π‐spacers from the 4,7‐positions of the N‐methyl‐benzimidazole junction. The π‐spacers, such as thiophene, ethyne, and ethane, have an effect on the acid response of photophysical properties in terms of changes in conformation, excited‐state energy and charge‐transfer (CT) characteristics. In particular, the π‐conjugated molecule with ethynyl spacers exhibited a marked redshift in the fluorescence spectrum with a large Stokes shift upon the addition of acid, whereas the other molecules showed substantial quenching. The redshift in emission was studied in detail by temperature‐dependent fluorescence measurements, which indicated the transition to a CT state over the finite activation energy at the excited state. The change in the frontier molecular orbitals upon acid addition was further discussed by means of DFT calculations. 相似文献
85.
We report about the observation of microtubules lying underneath the cell membrane of neural process in neurons with a resolution as high as that of an electron microscope by an illumination mode photon scanning tunneling microscope. Nanoapertures used in our observations were fabricated by means of selective chemical etching and metal coating of an optical fiber. The narrowest observed tube has got an average diameter of 26 nm. Comparing this with its nominal value of 25 nm, the difference which is considered as a measure of resolution (δ) is 1 nm implying a resolution comparable to that of an electron microscope in imaging dielectric specimens. This was possible due to the presence of a boundary between the glass and the metal coating and also due to the use of an aperture of almost the same size as that of the microtubule that enhances the detection. 相似文献
86.
Issei Otsuka Ryosuke Sakai Toshifumi Satoh Ryohei Kakuchi Harumi Kaga Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5855-5863
A poly(phenylacetylene) bearing a polycarbohydrate ionophore as a graft chain (copolymer 4 ) was synthesized by the copolymerization of end‐functionalized (1→6)‐2,5‐anhydro‐3,4‐di‐O‐ethyl‐D ‐glucitol with a 4‐ethynylbenzoyl group (macromonomer 2 ) with phenylacetylene. Copolymer 4 showed a split‐type circular dichroism (CD) in the long absorption region of the conjugated polymer backbone (280–500 nm), and the CD pattern varied in response to external stimuli, such as the solvents and temperature. This suggested that 4 had a predominantly one‐handed helical conformation in the polyacetylene backbone. The CD pattern of 4 was completely inverted by the formation of a complex between the macromolecular ionophore units and the selected metal cations, that is, Ba2+, Pb2+, Sr2+, Na+, and Li+. This suggested that copolymer 4 underwent a helix–helix transition through the host–guest complexation with achiral inorganic metal cations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5855–5863, 2005 相似文献
87.
Tomoyuki Maruyama Takumi Muto Toshitaka Tatsumi Kazuo Tsushima Anthony W. Thomas 《Nuclear Physics A》2005,760(3-4):319-345
The possibility of kaon condensation in high-density symmetric nuclear matter is investigated including both s- and p-wave kaon–baryon interactions within the relativistic mean-field (RMF) theory. Above a certain density, we have a collective state carrying the same quantum numbers as the antikaon. The appearance of the state is caused by the time component of the axial-vector interaction between kaons and baryons. It is shown that the system becomes unstable with respect to condensation of K– pairs. We consider how the effective baryon masses affect the kaon self-energy coming from the time component of the axial-vector interaction. Also, the role of the spatial component of the axial-vector interaction on the possible existence of the collective kaonic states is discussed in connection with Λ-mixing effects in the ground state of high-density matter. Implications of condensation for high-energy heavy-ion collisions are briefly mentioned. 相似文献
88.
Masashi Nakagawa Tatsuo Iwasa Satoshi Kikkawa Toshifumi Takao Yasutsugu Shimonishi Motoyuki Tsuda 《Photochemistry and photobiology》1997,65(1):187-191
Abstract— We determined the structure and site of fatty acid incorporated in octopus rhodopsin using a combination of fluorescence label and enzymatic cleavage methods in conjunction with fast-atom bombardment (FAB) mass spectrometry. A single peptide containing two adjacent cysteines, Cys337 and Cys338, was successfully isolated using the fluorescence from a dye conjugated to Cys345. The FAB mass spectrometric analysis of the peptide (323phe-340 phe) revealed that two palmitoyl groups are linked to Cys337 and Cys338 via thioester bonds in octopus rhodopsin as in bovine rhodopsin. 相似文献
89.
Toshifumi Miyazawa Toshihiko Otomatsu Takashi Yamada Shigeru Kuwata 《Tetrahedron letters》1984,25(7):771-772
Copper(II) chloride was found to be an extremely efficient additive suppressing racemization in the carbodiimide mediated couplings. 相似文献
90.
Okimichi Yano Susumu Saito Yoshio Sato Toshifumi Takeda Atsushi Tanaka Yasaku Wada 《Journal of Polymer Science.Polymer Physics》1981,19(2):221-227
The dielectric loss of high-density polyethylene was measured from 1 kHz to 100 MHz with the improved calorimetric method at liquid-helium temperature for samples with different oxidation times t. Two loss peaks, centered at ca. 4 kHz and at 1 MHz, both increase in height with increasing t. On the bases of these results along with previously reported ones, the low-frequency and high-frequency losses are ascribed to the tunneling of protons of OH groups in crystalline and amorphous regions, respectively. 相似文献