全文获取类型
收费全文 | 306篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 207篇 |
晶体学 | 6篇 |
力学 | 5篇 |
数学 | 13篇 |
物理学 | 81篇 |
出版年
2023年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 6篇 |
2012年 | 23篇 |
2011年 | 23篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有312条查询结果,搜索用时 15 毫秒
91.
We demonstrate high-resolution fluorescence imaging of single molecules using near-field scanning optical microscopy (NSOM)
with a tiny aperture probe for two different wavelengths in visible range in the illumination mode of operation. The spatial
resolutions obtained at both excitation wavelengths were almost the same and the highest resolution realized was about 10
nm. To discuss the achievable resolution in aperture NSOM, we also employed a computer simulation by the finite-difference
time-domain method for various aperture sizes and wavelengths. The resolution of 10 nm is predicted to be contributed by the
single peak of localized near-field light around the rim of the aperture. 相似文献
92.
Masahiro Tatsumisago Yoshikane Shinkuma Toshiharu Saito Tsutomu Minami 《Solid State Ionics》1992,50(3-4)
Superionic conducting phase of α-AgI, which is thermodynamically stable only above 147°C, was successfully frozen at ambient temperature in various kinds of glass matrices in the systems AgI---Ag2O---MxOy (MxOy=B2O3, GeO2,P2O5 and MoO3) by a rapid quenching technique. The larger composition regions where α-AgI was frozen were observed in the systems with B2O3 and GeO2 than in the systems with P2O5 and MoO3. Since the glasses with B2O3 and GeO2 have higher glass transition temperature than those with P2O5 and MoO3, the former glasses have higher viscosities at 147° C. The former matrix glasses have stronger effect to depress the α-β transformation of AgI rather than the latter glasses in the course of rapid quenching of melts. 相似文献
93.
Nakahiro Yoshida Toshiharu Hayashi 《Annals of the Institute of Statistical Mathematics》1990,42(3):489-507
Under some regularity conditions, it is well known that the maximum likelihood estimator (MLE) is asymptotically normal and efficient. However, if the observation is contaminated, the MLE is not always an appropriate estimator. In this paper, we treat M-estimators and study their asymptotic behavior. By choosing estimation equations, robust M-estimators are presented for phase parameters. 相似文献
94.
S. Katsuki 《Solid State Communications》1981,39(6):767-769
The electronic band structure of the partially inverse spinel MgIn2S4 has been calculated on the symmetry lines ΓΛL, ΓΔX and ΓΣK by the semiempirical pseudopotential method. The general features of the band structure of MgIn2S4 are quite similar to those of the normal spinel CdIn2S4. The conduction band minimum is located at Γ and the valence band maximum is along the Σ line. The indirect energy gap (Γ1cΣ4v) is 2.50 eV. The effects of magnesium vacancy and variations in the cation distribution and in the parameter u are examined and shown to be small. 相似文献
95.
96.
97.
Naren G Masuda R Iida M Harada M Kurosu H Suzuki T Kimura T 《Dalton transactions (Cambridge, England : 2003)》2008,(13):1698-1709
Octanoylalaninato-metal (metal = calcium(II), yttrium(III), lanthanum(III), and zinc(II)) complexes were prepared and the first three metal complexes were found to readily form transparent and stable molecular glasses from methanol and chloroform solutions. The process of glass formation from solution was studied in detail. The effect of the central metal ions on the formation of glassy states was remarkable: the lanthanum and calcium complexes assumed glassy or crystalline states depending on the isolation method and the yttrium complex had a large tendency to assume an amorphous state, whereas the zinc complex did not assume a pure and stable glassy-state. The glass transition temperatures were 50 degrees C for the yttrium complex and 70-75 degrees C for the lanthanum and calcium complexes when these complexes are monohydrates prepared by a solvent-cast method, whereas they increase by 10-30 degrees for the hemihydrates which were obtained by an annealing treatment at 110 degrees C. The coordinated water was eliminated from the solid above the glass transition temperature. The glassy state was regarded as a result of the self-aggregation of the metal complex in solution by an entanglement of the methylene chains with one another. SAXS showed the presence of two disordered bilayer structures with 2.2 nm and 4.5 nm periods in the glassy states. The structures of the molecular assemblies in the solid states and solutions were compared by SAXS and NMR studies. EXAFS studies confirmed the coordination numbers of oxygen atoms around the yttrium and lanthanum atoms in the glassy states for the yttrium and lanthanum complexes to be about 7. 相似文献
98.
Nakata M Braams BJ Fujisawa K Fukuda M Percus JK Yamashita M Zhao Z 《The Journal of chemical physics》2008,128(16):164113
The reduced density matrix (RDM) method, which is a variational calculation based on the second-order reduced density matrix, is applied to the ground state energies and the dipole moments for 57 different states of atoms, molecules, and to the ground state energies and the elements of 2-RDM for the Hubbard model. We explore the well-known N-representability conditions (P, Q, and G) together with the more recent and much stronger T1 and T2(') conditions. T2(') condition was recently rederived and it implies T2 condition. Using these N-representability conditions, we can usually calculate correlation energies in percentage ranging from 100% to 101%, whose accuracy is similar to CCSD(T) and even better for high spin states or anion systems where CCSD(T) fails. Highly accurate calculations are carried out by handling equality constraints and/or developing multiple precision arithmetic in the semidefinite programming (SDP) solver. Results show that handling equality constraints correctly improves the accuracy from 0.1 to 0.6 mhartree. Additionally, improvements by replacing T2 condition with T2(') condition are typically of 0.1-0.5 mhartree. The newly developed multiple precision arithmetic version of SDP solver calculates extraordinary accurate energies for the one dimensional Hubbard model and Be atom. It gives at least 16 significant digits for energies, where double precision calculations gives only two to eight digits. It also provides physically meaningful results for the Hubbard model in the high correlation limit. 相似文献
99.
Dongchan Kim Sanghoon Kook Ryosuke Kusakari Koya Shinohara Katsuki Iijima Tetsuya Aizawa 《Proceedings of the Combustion Institute》2021,38(4):5761-5768
This study shows the structure of soot particles sampled directly from wall wetting-induced pool fires formed on the piston top in a spark-ignition direct-injection (SIDI) engine. Of particular interest is its variation with injection pressure considering the current trend of high-pressure DI system development to reduce engine-out particulate emissions. Thermophoretic particle sampling was performed for transmission electron microscope (TEM) imaging, which was post-processed for statistical analysis of key morphology and internal structure parameters. These include the size distribution of soot aggregates and primary particles as well as carbon-layer fringe-to-fringe gap and concentricity. With the fixed engine speed and load conditions, in-flame soot particles are compared to the exhaust particles sampled simultaneously at selected 5 and 15 MPa injection pressures corresponding to low-speed/low-load and high-speed/high-load in practical engine operation. From the TEM images and statistical analysis, it was found that more concentrated and taller pool fire developed for 5-MPa injection leads to smaller soot aggregates composed of smaller soot primary particles due to suppressed soot growth in fuel-rich flames. However, the soot particles formed in 15-MPa injection-induced pool fires are at a more reactive status evidenced by less defined core-shell boundaries and higher fringe separation. The higher soot reactivity results in enhanced soot oxidation, which explains smaller soot aggregates and primary particles found for the 15-MPa injection in the exhaust sample. 相似文献
100.