全文获取类型
收费全文 | 733篇 |
免费 | 23篇 |
国内免费 | 6篇 |
专业分类
化学 | 464篇 |
晶体学 | 10篇 |
力学 | 25篇 |
数学 | 51篇 |
物理学 | 212篇 |
出版年
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 39篇 |
2010年 | 38篇 |
2009年 | 26篇 |
2008年 | 41篇 |
2007年 | 47篇 |
2006年 | 52篇 |
2005年 | 49篇 |
2004年 | 48篇 |
2003年 | 25篇 |
2002年 | 28篇 |
2001年 | 11篇 |
2000年 | 22篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 12篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有762条查询结果,搜索用时 15 毫秒
751.
Tetsuya Shimada Satoshi Hamatani Shingo Onodera Yohei Ishida Haruo Inoue Shinsuke Takagi 《Research on Chemical Intermediates》2013,39(1):269-278
Time-resolved fluorescence and steady-state spectroscopic measurements were performed with +4-charged cationic porphyrins adsorbed on an anionic-type clay (Sumecton SA; SSA) surface at a low molecular loading level (10 % vs. cation-exchange capacity of clay) corresponding to an occupied area of ca 50 nm2 per molecule. Absorption spectra indicated no interaction between transition moments of the porphyrins on the clay surface. An efficient energy-transfer process from donor to acceptor porphyrin was observed on the clay surface even under low porphyrin loading conditions. The efficiency of energy transfer obtained from the steady-state measurement was 65 %. Real-time behavior of the porphyrins was successfully captured during energy transfer. The rate constant of the energy transfer obtained from time-resolved fluorescence measurements was found to be 5.3 × 108 s?1. According to the efficiency and the rate constant, it is proposed that the adsorbed porphyrins did not have a uniform and fixed distribution. 相似文献
752.
Midori Fukaya Ryuji Uesugi Hirokazu Ohashi Yuta Sakai Masaaki Sudo Atsushi Kasai Hidenari Kishimoto Masahiro Osakabe 《Photochemistry and photobiology》2013,89(2):424-431
Plant‐dwelling mites are potentially exposed to solar ultraviolet‐B (UVB) radiation that causes deleterious and often lethal effects, leading most mites to inhabit the lower (underside) leaf surfaces. However, in species of spider mite belonging to the Genus Panonychus, a substantial portion of individuals occur on upper leaf surfaces. We investigated whether the upper leaf surfaces of citrus trees are favorable for P. citri, and to what extent they are tolerant to UVB radiation. If eggs are not adequately protected from UVB damage, females may avoid ovipositing on the upper surfaces of sunny leaves. To test this, we conducted laboratory experiments using a UVB lamp, and semioutdoor manipulative experiments. As a result, P. citri eggs are tolerant to UVB. Field studies revealed that the ratio of eggs and adult females on upper leaf surfaces were larger for shaded than for sunny leaves. However, 64–89% of eggs hatched successfully even on sunny upper leaf surfaces. Nutritional evaluation revealed that whether on sunny or shaded leaves, in fecundity and juvenile development P. citri reaped the fitness benefits of upper leaf surfaces. Consequently, P. citri is tolerant to UVB damage, and inhabiting the upper surfaces of shaded leaves is advantageous to this mite. 相似文献
753.
Y. Kishimoto Y. Kawasaki Y. Ideta G. Ghosh L.C. Gupta 《Journal of Physics and Chemistry of Solids》2008,69(12):3153-3155
To investigate the electronic states in YRuB2 and LuRuB2, we have carried out 11B NMR measurements. In the normal state, the spin-lattice relaxation rates 1/T1's in these compounds are proportional to the temperature T. 1/T1's show a small coherence peak just below the superconducting transition temperature Tc and decrease exponentially well below Tc. YRuB2 and LuRuB2 are found to be BCS superconductors with the energy gap 2Δ(0)=3.52 kBTc. 相似文献
754.
Design of patterned media for an areal density of 1 Tbit/in2 with thermal stability is presented based on perpendicular M–H loops of the media. Required perpendicular magnetic anisotropy was estimated to be achieved with known materials. However, it is indicated that magnetostatic interaction between the dots becomes a limiting factor for achieving higher densities. Recording simulation using a Karlqvist pole head on the designed media exhibited possibility of the recording of 1 Tbit/in2. Shift margin of the write head in the cross-track direction was found to be increased with elongated dots in the down-track direction. Recording simulation with an FEM-analyzed field of a side-shielded multi-surface pole head exhibited successful recording with increased cross-track shift margins as well as the effect of the elongated dot shape. 相似文献
755.
Shingo Kanehira Kiyotaka Miura Kazuyuki Hirao Naoya Shibata Yuichi Ikuhara 《Applied Physics A: Materials Science & Processing》2008,92(4):913-916
We show a unique technique to form dense dislocations locally inside a MgO single crystal with a rock-salt type structure
using femtosecond (fs) laser irradiation. Cross-shaped patterns of micrometer size, originating from densely introduced dislocations,
are formed spontaneously around the focal point. We controlled the three-dimensional propagation of the dislocations by adjusting
the pulse energy of the fs laser and NA of objective lens. The technique may open up a new field of dislocation technology
for optical applications. 相似文献
756.
Abe S Ebihara T Enomoto S Furuno K Gando Y Ichimura K Ikeda H Inoue K Kibe Y Kishimoto Y Koga M Kozlov A Minekawa Y Mitsui T Nakajima K Nakajima K Nakamura K Nakamura M Owada K Shimizu I Shimizu Y Shirai J Suekane F Suzuki A Takemoto Y Tamae K Terashima A Watanabe H Yonezawa E Yoshida S Busenitz J Classen T Grant C Keefer G Leonard DS McKee D Piepke A Decowski MP Detwiler JA Freedman SJ Fujikawa BK Gray F Guardincerri E Hsu L Kadel R Lendvai C Luk KB Murayama H O'Donnell T Steiner HM Winslow LA 《Physical review letters》2008,100(22):221803
The KamLAND experiment has determined a precise value for the neutrino oscillation parameter Deltam21(2) and stringent constraints on theta12. The exposure to nuclear reactor antineutrinos is increased almost fourfold over previous results to 2.44 x 10(32) proton yr due to longer livetime and an enlarged fiducial volume. An undistorted reactor nu[over]e energy spectrum is now rejected at >5sigma. Analysis of the reactor spectrum above the inverse beta decay energy threshold, and including geoneutrinos, gives a best fit at Deltam21(2)=7.58(-0.13)(+0.14)(stat) -0.15+0.15(syst) x 10(-5) eV2 and tan2theta12=0.56(-0.07)+0.10(stat) -0.06+0.10(syst). Local Deltachi2 minima at higher and lower Deltam21(2) are disfavored at >4sigma. Combining with solar neutrino data, we obtain Deltam21(2)=7.59(-0.21)+0.21 x 10(-5) eV2 and tan2theta12=0.47(-0.05)+0.06. 相似文献
757.
Wen Ji Yuan Takao Yasuhara Tetsuro Shingo Kenichiro Muraoka Takashi Agari Masahiro Kameda Takashi Uozumi Naoki Tajiri Takamasa Morimoto Meng Jing Tanefumi Baba Feifei Wang Hanbai Leung Toshihiro Matsui Yasuyuki Miyoshi Isao Date 《BMC neuroscience》2008,9(1):1-11
Background
A recent human clinical trial of an Alzheimer's disease (AD) vaccine using amyloid beta (Aβ) 1–42 plus QS-21 adjuvant produced some positive results, but was halted due to meningoencephalitis in some participants. The development of a vaccine with mutant Aβ peptides that avoids the use of an adjuvant may result in an effective and safer human vaccine.Results
All peptides tested showed high antibody responses, were long-lasting, and demonstrated good memory response. Epitope mapping indicated that peptide mutation did not lead to epitope switching. Mutant peptides induced different inflammation responses as evidenced by cytokine profiles. Ig isotyping indicated that adjuvant-free vaccination with peptides drove an adequate Th2 response. All anti-sera from vaccinated mice cross-reacted with human Aβ in APP/PS1 transgenic mouse brain tissue.Conclusion
Our study demonstrated that an adjuvant-free vaccine with different Aβ peptides can be an effective and safe vaccination approach against AD. This study represents the first report of adjuvant-free vaccines utilizing Aβ peptides carrying diverse mutations in the T-cell epitope. These largely positive results provide encouragement for the future of the development of human vaccinations for AD. 相似文献758.
Shinohara Y Imai R Kishimoto H Yagi N Amemiya Y 《Journal of synchrotron radiation》2010,17(6):737-742
An indirectly illuminated X-ray area detector is employed for X-ray photon correlation spectroscopy (XPCS). The detector consists of a phosphor screen, an image intensifier (microchannel plate), a coupling lens and either a CCD or CMOS image sensor. By changing the gain of the image intensifier, both photon-counting and integrating measurements can be performed. Speckle patterns with a high signal-to-noise ratio can be observed in a single shot in the integrating mode, while XPCS measurement can be performed with much fewer photons in the photon-counting mode. By switching the image sensor, various combinations of frame rate, dynamic range and active area can be obtained. By virtue of these characteristics, this detector can be used for XPCS measurements of various types of samples that show slow or fast dynamics, a high or low scattering intensity, and a wide or narrow range of scattering angles. 相似文献
759.
760.
Hideyuki Kaneko Shingo Matsuo Nobuo Kawahara Junji Saito Tomoaki Matsugi Norio Kashiwa 《Macromolecular Symposia》2007,260(1):9-14
Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment. 相似文献