全文获取类型
收费全文 | 2926篇 |
免费 | 71篇 |
国内免费 | 5篇 |
专业分类
化学 | 1985篇 |
晶体学 | 32篇 |
力学 | 39篇 |
综合类 | 1篇 |
数学 | 125篇 |
物理学 | 820篇 |
出版年
2023年 | 18篇 |
2022年 | 18篇 |
2020年 | 32篇 |
2019年 | 39篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 56篇 |
2015年 | 42篇 |
2014年 | 52篇 |
2013年 | 128篇 |
2012年 | 126篇 |
2011年 | 185篇 |
2010年 | 88篇 |
2009年 | 86篇 |
2008年 | 187篇 |
2007年 | 174篇 |
2006年 | 175篇 |
2005年 | 189篇 |
2004年 | 168篇 |
2003年 | 141篇 |
2002年 | 128篇 |
2001年 | 65篇 |
2000年 | 63篇 |
1999年 | 46篇 |
1998年 | 36篇 |
1997年 | 41篇 |
1996年 | 44篇 |
1995年 | 42篇 |
1994年 | 40篇 |
1993年 | 37篇 |
1992年 | 55篇 |
1991年 | 30篇 |
1990年 | 25篇 |
1989年 | 33篇 |
1988年 | 24篇 |
1987年 | 33篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 32篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 30篇 |
1978年 | 22篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 11篇 |
排序方式: 共有3002条查询结果,搜索用时 15 毫秒
1.
This paper proposes and analyzes a GaAs traveling-wave optical modulator which uses a modulated coplanar strip electrode with periodic cross-tie overlay. This slow-wave structure can be designed to satisfy phase velocity and impedance matching conditions simultaneously. The dominant conductor loss in the slow-wave structure is reduced using the modulated coplanar strip electrode. The calculated 3-dB modulation bandwidth (100 GHz) is much wider than the bandwidth limit (30 GHz) of conventional electrode structures that are limited by phase velocity mismatch.This work was supported by the U.S. Army Research Office under contract DAAL-03-88-K-0005 and the Texas Advanced Technology Program. 相似文献
2.
Akihide Itoh Taisuke Nagasawa Yanbei Zhu Kyue-Hyung Lee Eiji Fujimori Hiroki Haraguchi 《Analytical sciences》2004,20(1):29-36
In order to elucidate the distributions of the elements among the particulate and dissolved fractions in pond water, major-to-ultratrace elements in different sizes of particles as well as in the filtrate passed through the 0.05 microm filter were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The different sizes of particle samples (ca. 100-300 microg each) were collected on the membrane filters with pore sizes of 10, 3.0, 1.2, 0.4, 0.2 and 0.05 microm, respectively, by sequential fractionation. As a result, about 40 elements in different sizes of particles could be determined by ICP-AES and ICP-MS, after acid digestion using HNO3/HF/HClO4. Then, the fractional distribution factors of major-to-ultratrace elements among the particulate and dissolved fractions were estimated from the analytical results. The total contents of Al, Fe, Ti, REEs (rare earth elements), Bi, Pb and Ag in the particulate fractions (larger than 0.05 microm) were more than 80-90%, while those of Ca, Sr, Cs, W, Ba, Mn and Co in the dissolved fraction, which corresponded to the filtrate passed through the 0.05 microm membrane filter, were more than 80%. It was further found that the fractional distributions of Cu and Zn in the dissolved fraction were ca. 50%. In addition, the enrichment factors (EFs) of the elements in the particulate fractions with particle sizes of 3.0-10 microm and 0.05-0.2 microm were estimated to elucidate their geochemical characteristics in natural water. 相似文献
3.
We prove here that the surface of the regular icosahedron can be triangulated with 8
non-obtuse and with 12 acute triangles. We also show these numbers to be smallest
possible. 相似文献
4.
Applying tight-binding approximation and spin pairing of like charge carriers in a pair of excitons created in a lattice, the possibility of forming a bound exciton-exciton state is studied. It is found that, provided there exists strong exciton-lattice interaction, such a bound state may be formed and its energy may lie within the valence band deforming the material into a crystalline solid with no energy gap. Lowering of the energy is calculated in naphthalene and anthracene crystals where some experimental results are known. The excess energy released after the formation of such bound state can be adequate, depending on the material, to desorb neutral atoms or eject of electrons from surfaces. 相似文献
5.
Tsuyoshi Katayama 《Queueing Systems》1992,11(3):299-306
This paper derives a conservation law for mean waiting times in a single-server multi-class service queueing system (M
X/G/1 type queue) with setup times which may be dependent on multiple customer classes and its arrival batch size by using the work decomposition property in the queueing system with vacations. 相似文献
6.
We investigate low-temperature behaviors of a system with chirality-pair interaction on a one-dimensional lattice. In the course of the investigation, we evaluate asymptotic forms of the characteristic values of the integral equation satisfied by the Mathieu functions. It turns out that the low-temperature behavior of correlation length of the chirality-pair correlation function is different from the one for the Ising model of spin ±1 but akin to the one for the Ising model of infinite spin. 相似文献
7.
Koichi Itoh Takeji Takui 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(2):29
This review paper deals with an overview of molecule-based magnetism as a rapidly developing interdisciplinary field, topological symmetry rule as the first principle of spin alignment in organic open-shell systems in the ground state, the proposal of organic through-bond 1D and 2D ferro- and superparamagnets and the detection of the first organic high-spin molecule, m-phenylenebis(phenylmethylene) in the quintet ground state (S = 2), followed by extended organic high-spin systems with π-conjugation such as aromatic hydrocarbons having S = 3, 4, 5. The paper also describes a theoretical approach to the understanding of electronic spin structures of organic high-spin molecules by invoking both Heisenberg and Hubbard model Hamiltonians, weakly interacting intramolecular high-spin systems from both experimental and theoretical sides, the spin density distribution of the first organic high-spin molecule in terms of electron- nuclear multiple resonance spectroscopy and the detection and characterization of ionic high-spin hydrocarbons, emphasizing the establishment of high spin chemistry underlying organic molecular magnetism. 相似文献
8.
9.
Hiroshi Sakurai Fumitake Itoh Katsuyoshi Takano Hiromi Oike 《Journal of Physics and Chemistry of Solids》2004,65(12):2083-2088
A novel technique of measuring a magnetic Compton profile using the grazing angle geometry against a sample surface (Grazing Incidence Magnetic Compton Profile) has been successively developed. Measurements of a magnetic moment and a magnetic Compton profile are possible for a Fe 200 nm film on a thick glass substrate. The estimated thinnest limit for measurements is 100 nm for a Fe film. 相似文献
10.
Yoshiaki Yasuno Yasunori Sutoh Shuichi Makita Masahide Itoh Toyohiko Yatagai 《Optical Review》2003,10(5):498-500
A spectral interferometric optical coherence tomography (OCT) system which has polarization sensitivity is developed. This system reduces the mechanical scanning dimension by employing the principle of spectral interferometry, and measures a two dimensional cross-sectional image of biological tissue with one dimensional mechanical scanning. Sixteen OCT images with different polarization conditions are measured, and two dimensional distributions of each element of the Müller matrix of a sample to be measured are calculated. 相似文献