全文获取类型
收费全文 | 143篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学 | 57篇 |
力学 | 3篇 |
数学 | 27篇 |
物理学 | 38篇 |
无线电 | 20篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1942年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有145条查询结果,搜索用时 328 毫秒
1.
Fathy A.E. Pendrick V.A. Geller B.D. Perlow S.M. Tormey E.S. Prabhu A. Tani S. 《Microwave Theory and Techniques》2002,50(10):2247-2252
We have developed an innovative semianalytical technique for various substrate material characterization. The developed technique is a measurement procedure and data-reduction formulation that takes into consideration the radiation loss in a resonant structure, allowing for a more effective means of dielectric- and conductor-loss determination for a microstrip ring resonator and its substrate material. We separate dielectric and conductor loss precisely, evaluate the contribution of each term in the overall loss performance, and analytically predict the error in their respective predicted value. 相似文献
2.
V. I. Zubkov I. S. Shulgunova A. V. Solomonov M. Geller A. Marent D. Bimberg A. E. Zhukov E. S. Semenova V. M. Ustinov 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(1):106-108
In this work, charge-carrier capture by an array of self-assembled InAs/GaAs quantum dots was directly observed for the first time by capacitance recharge. It is proposed to process the obtained transient-capture data by a similar method to that used for emission, by the box-car method. The capture activation energies are determined and compared with the emission activation energies. 相似文献
3.
4.
[reaction: see text]. Polyethylene glycol (PEG)-bound poly-L-leucine acts as a THF-soluble catalyst for the Juliá-Colonna asymmetric epoxidation of enones. Excellent enantioselectivities may be obtained even with short chain length polyleucine. FT-IR investigations have determined that the catalytically active polyleucine components of these copolymers have an alpha-helical structure. 相似文献
5.
The solvent used was dimethylformamide at neutral and alkaline pH. The equilibrium constants are determined by spectrophotometry. The rate of proton exchange has been measured as a function of temperature and concentration. The rate constants and activation energies have been measured; for uncatalyzed exchange kn=(1.5±0.5) ·· 103 M–1 sec–1, E=8±1 kcal/mole, while base-catalyzed exchange has k=(0.3±0.1) · 106 M–1 sec–1 and E=6±1 kcal/mole.We are indebted to A. I. Brodskii for assistance in this work, and to V. I. Oshkaderov and L. A. Kichakova for recording the NMR spectra. 相似文献
6.
Results of electrical conductivity measurements, thermal analysis, and X-ray diffraction studies indicate the existence of four phases, between 295 K and the melting points, in the system (Cs1?yRby)Cu4Cl3I2. These phases are designated α, á β, γ in order of decreasing temperature. The α phase is isostructural with α-RbAg4I5; the á phase is also cubic and very likely belongs to space groupP213, a subgroup ofP4132 andP4332 to which the α phase belongs. There is a high probability that the á → α transition is continuous. The á → α transition is not discernible in the conductivity measurements or thermal analysis; therefore the line of á-α transitions is presently unknown. The β phase transforms to the á and the γ phase transforms to the β phase wheny ≤ 0.36; the γ phase transforms to the α phase wheny ≥ 0.36. That is, there is a triple point aty = 0.36, T = 399K. The γ-β, β-α′, and γ-α transitions are all hysteretic and are therefore first order. The conductivities of the β phases are relatively low and the enthalpies of activation relatively high. The conductivity of the β phase decreases with increasingy. The β phase probably belongs to space groupR3, in which the Cu+ ions can be ordered. The α and á phases are the true solid electrolytes; the conductivities are high, >0.73 Ω?1cm?1 at 419 K, and the enthalpies of activation of motion of the Cu+ ions low, 0.11 eV.In the system CsCu4Cl3(I2?xClx), 0 ≤ x ≤ 0.25, the Cl? for I? substitutions affect the transitions to only a small extent relative to the stoichiometric compound. The β phase occurs for allx and transforms to á. 相似文献
7.
A. I. Brodskii B. A. Geller V. I. Oshkaderov 《Theoretical and Experimental Chemistry》1971,4(3):207-211
The compound has been used over a temperature range in dimethylsulfoxide, with trichloroacetic acid and triethylamine as catalysts. The rate constant for uncatalyzed bimolecular exchange at 25 C is kN=131 M–1 sec–1; the constant for acid-catalyzed exchange is kA=0.9 · 104 M–1 sec–1; and that for base-catalyzed exchange is kB=0.5 · 104 M–1 sec–1. The activation energy for uncatalyzed exchange is 5.75 kcal/mole. The exchange rates in dimethylformamide and acetone are higher, on account of differences in the hydrogen bond. The exchange rates of the isomers fall in the sequence ortho > para > meta, which is due to conjugation and intramolecular hydrogen bonding. The exchange mechanism is discussed. Simple relationships in dimensionless parameters are given for calculating the exchange rate from the shape of the NMR signal. 相似文献
8.
The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless person- 相似文献
9.
Daryl Geller 《Journal of Functional Analysis》1980,36(2):205-254
We derive a usable characterization of the group FT (Fourier Transform) of Schwartz space on the Heisenberg group n, in terms of certain asymptotic series. To accomplish this we study in detail the FT of multiplication and differentiation operators on n, the relation of multiple Fourier series to the FT, and the process of group contraction on n. We use our characterization to solve a form of the division problem for convolution of n, which has application to Hardy space theory. 相似文献
10.
The atomic dipole approximation has been employed to calculate the energies of electrostatic interaction between adenine and various pyrimidine derivatives. Minima of the interaction energy for various planar configurations were determined. Inclusion of the “monopole–dipole” and “dipole–dipole” terms in the multipole expansion improves considerably the agreement with experimental data. The effect of sulfur substitution has been investigated in detail. Formation of N? H…?S hydrogen bonds is less favorable than of N? H…?O bonds, due largely to the lower atomic dipole of the sulfur atom resulting from the shift of the π-electron charge toward the neighboring carbon. The results are relevant to the interactions of thiouracils in nucleic acids. 相似文献