全文获取类型
收费全文 | 248篇 |
免费 | 7篇 |
专业分类
化学 | 123篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 17篇 |
物理学 | 110篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有255条查询结果,搜索用时 15 毫秒
211.
Keiko Nakada Seiya Kondo Yoshiteru Matsumoto Masamichi Yamanaka 《Tetrahedron letters》2017,58(49):4612-4616
Dynamic covalent chemistry is an effective technique for the preparation of complex organic compounds. We succeeded in synthesizing a cage-shaped compound through the aggregation of two types of functional molecules. More specifically, a tris-imine 5 was quantitatively obtained by reacting a C3-symmetric trialdehyde 1 with a triamine 4 in acetonitrile in the presence of a trifluoroacetic acid catalyst. We also achieved the synthesis of the corresponding triamine 9 and the acetylated derivative 10 through reduction of the tris-imine CN double bonds and subsequent acetylation. 相似文献
212.
Satoshi Tsutsui Masami Nakada Saburo Nasu Yoshinori Haga Tetsuo Honma Etsuji Yamamoto Hitoshi Ohkuni Yoshichika Ōnuki 《Hyperfine Interactions》2000,126(1-4):335-340
We have performed 238U Mössbauer spectroscopy of uranium-based heavy fermion superconductors, UPd2Al3 and URu2Si2, in order to investigate their physical properties, mainly their magnetic properties. The slow relaxation of magnetic hyperfine interaction in a paramagnetic state and the static hyperfine field has been observed in an antiferromagnetic ordered state for each compound. The line-widths have maximum at their characteristic temperatures where their magnetic susceptibilities have maximum values. 相似文献
213.
Signal Formation of Image-Edge Motion Based on Biological Retinal Networks and Implementation into an Analog Metal-Oxide-Silicon Circuit 总被引:1,自引:0,他引:1
Hitoshi Yamada Takashige Miyashita Masahiro Ohtani Kimihiro Nishio Hiroo Yonezu Yuzo Furukawa 《Optical Review》2001,8(5):336-342
A simplified model was proposed for the formation of edge signals and generation of motion signals of a target based on the information processing mechanisms of outer and inner retinas of a vertebrate. Analog metal-oxide-silicon (MOS) integrated circuits were designed based on the model. Simulation program with integrated circuit emphasis (SPICE) simulation results showed the performance of local adaptation over a wide dynamic range in the outer retinal circuit and generation of the velocity signal of a moving edge in the inner retinal circuit. Preliminary experimental results showed local adaptation in a given input range in the outer retinal circuit and the generation of motion pulsed signals in the inner retinal circuit. 相似文献
214.
Wakayama Tatsuki Nakada Eiju Asada Yasuo Miyake Jun 《Applied biochemistry and biotechnology》2000,84(1-9):431-440
Hydrogen production by photosynthetic bacteria provides an efficient energy conversion method under low light intensity. However,
under strong illumination, such as midday sunlight, the efficiency drops. This prevents the method from being applied industrially.
To overcome this problem, we examined a method to thin out the excessive illumination. Light was given intermittently to reduce
the total energy flux. The on/off ratio was set at 1/1 throughout the study, so that the time average of the light energy
flux became half the continuous illumination. By keeping the time-average light flux constant (0.6 kW·m−2), the effects of the cycle period were examined in the range of hours to seconds. The hydrogen production rate was greatly
affected by the cycle period, but cell growth and substrate consumption rates remained almost constant. The 30-min light/dark
cycle (30 min on and 30 min off) provided the highest rate of hydrogen production (22 L·m−2·24 h−1). At the shorter cycles, the rate decreased except that there was a suboptimum at about 40 s. Under excessive light intensity
(1.2 kW·m−2), the light-to-hydrogen conversion efficiency was greatly enhanced. The hydrogen production rate during the 30-min cycle
was twice as high as during a 12-h cycle under the same conditions. 相似文献
215.
T. Saito J. Wang T. Kitazawa M. Takahashi M. Takeda M. Nakada T. Nakamoto N. M. Masaki T. Yamashita M. Saeki 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(2):319-323
Four types of neptunyl(VI) hydroxides have been synthesized by chemical oxidation of Np(IV) instead of ozone oxidation of Np(V) which caused the partial oxidation to the heptavalent state. NpO2(OH)2 (I) and NpO2(OH)2·H2O (orthorhombic type) (II) have been obtained by adding pyridine to the solution at 373K and 343K, respectively. NpO2(OH)2·H2O (hexagonal type) (III) and NpO2(OH)2·xH2O·yNH3 (x+y=1) (IV) have been prepared by using LiOH and NH4OH, respectively. The four materials have been characterized by X-ray powder diffraction patterns, thermogravimetric analysis and237Np Mössbauer spectra. The237Np Mössbauer spectrum of (I) measured first time as anhydrous neptunyl(VI) hydroxide (δ=?46.2 mm/s,e 2 qQ=193 mm/s and η=0.16 at 4.8K) has more distinct five-line Mössbauer pattern than those of (II), (III) and (IV). The Mössbauer spectra for (II), (III) and (IV) are slightly different from each other. The structural information has been obtained from these data. 相似文献
216.
W. Bell K. Braune G. Claesson D. Drijard M. A. Faessler H. G. Fischer H. Frehse R. W. Frey S. Garpman W. Geist C. Gruhn P. Hanke M. Heiden W. Herr P. G. Innocenti T. J. Ketel E. E. Kluge I. Lund G. Mornacchi T. Nakada I. Otterlund B. Povh A. Putzer B. Rensch E. Stenlund T. J. M. Symons R. Szwed O. Ullaland M. Wunsch CERN-Heidelberg-Lund Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,22(2):109-118
Two-particle rapidity correlations have been studied for αα, αp, andp p interactions at the CERN ISR using the Split-Field Magnet (SFM) detector. In order to isolate the true two-particle correlations, the analysis was performed at fixed charged multiplicity. In the framework of a simple cluster model, it is found that cluster widths as well as cluster multiplicities are the same for αα, αp, andp p interactions, and both decrease with increasing charged multiplicity. 相似文献
217.
The European Physical Journal C - LHCb is a dedicated experiment to study CP violation and other rare processes in the B meson system at LHC. It is designed to exploit the large sample of Bd and Bs... 相似文献
218.
1H-F-Alkene-1-phosphonates, easily accessible from F-alkanoyl chlorides, underwent dephosphorylation on treatment with a catalytic amount of fluoride ion at O°C to room temperature to give terminal F-alkylacetylenes in good yields. 相似文献
219.
Title azaannulenes, the paratropic and diatropic vinylogues of pyridine, were synthesized starting from the annulenones. 相似文献
220.
T. Nakamoto M. Nakada N. M. Masaki M. Saeki T. Yamashita N. N. Krot 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(2):257-261
237Np Mössbauer spectrum of the heptavalent neptunium compound [Co(NH3)6][NpO4(OH)2]·2H2O was remeasured for certification of the previous investigations. The isomer shift value of the Mössbauer spectrum showed a characteristic value for the heptavalent neptunium at 4.7K. Although the spectrum seemed to consist of two quadrupole-split peaks as previously reported byStone et al., the fitting with using two quadrupole-split peaks did not give a good agreement withStone's data. 相似文献