全文获取类型
收费全文 | 2683篇 |
免费 | 61篇 |
国内免费 | 9篇 |
专业分类
化学 | 2056篇 |
晶体学 | 28篇 |
力学 | 47篇 |
数学 | 126篇 |
物理学 | 496篇 |
出版年
2022年 | 21篇 |
2021年 | 20篇 |
2020年 | 33篇 |
2019年 | 35篇 |
2018年 | 31篇 |
2017年 | 17篇 |
2016年 | 54篇 |
2015年 | 40篇 |
2014年 | 49篇 |
2013年 | 105篇 |
2012年 | 112篇 |
2011年 | 125篇 |
2010年 | 81篇 |
2009年 | 87篇 |
2008年 | 154篇 |
2007年 | 108篇 |
2006年 | 147篇 |
2005年 | 142篇 |
2004年 | 120篇 |
2003年 | 106篇 |
2002年 | 90篇 |
2001年 | 53篇 |
2000年 | 66篇 |
1999年 | 40篇 |
1998年 | 28篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 22篇 |
1994年 | 43篇 |
1993年 | 27篇 |
1992年 | 42篇 |
1991年 | 22篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 42篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 40篇 |
1983年 | 31篇 |
1982年 | 40篇 |
1981年 | 40篇 |
1980年 | 41篇 |
1979年 | 39篇 |
1978年 | 29篇 |
1977年 | 35篇 |
1976年 | 30篇 |
1975年 | 25篇 |
1974年 | 22篇 |
1973年 | 17篇 |
排序方式: 共有2753条查询结果,搜索用时 15 毫秒
61.
Takashi Minoshima Yosuke Matsumoto Takanobu Amano 《Journal of computational physics》2011,230(17):6800-6823
We present a new numerical scheme for solving the advection equation and its application to Vlasov simulations. The scheme treats not only point values of a profile but also its zeroth to second order piecewise moments as dependent variables, for better conservation of the information entropy. We have developed one-and two-dimensional schemes and show that they provide quite accurate solutions within reasonable usage of computational resources compared to other existing schemes. The two-dimensional scheme can accurately solve the solid body rotation problem of a gaussian profile for more than hundred rotation periods with little numerical diffusion. This is crucially important for Vlasov simulations of magnetized plasmas. Applications of the one- and two-dimensional schemes to electrostatic and electromagnetic Vlasov simulations are presented with some benchmark tests. 相似文献
62.
Akihiko Takagi Xiobin Peng Takuya Matsumoto Atsuhiro Osuka Tomoji Kawai 《Surface science》2007,601(10):2178-2181
Conformations of two dodecameric porphyrin wheels adsorbed on a Cu(1 0 0) were probed by using scanning tunneling microscopy (STM). Whereas a wheel consisting of six meso-meso linked diporphyrins was detected as uniform ring structure, several different images with three discrete molecular heights were detected for a wheel consisting of six meso-meso, β-β,β-β triply-linked planar diporphyrins. These results indicate that the former has a conformation similar to that in a free space, while the latter has various conformations with respect to orientation of planar diporphyrin units toward the metal surface. Several discrete STM images of the latter have been interpreted in terms of possible eight conformations, which vary as to relative orientation of neighboring diporphyrin units. 相似文献
63.
Taketoshi Matsumoto Patricia Nickut Kazuya Watanabe Tatsuya Tsukuda Katharina Al-Shamery 《Surface science》2007,601(22):5226-5231
Reduction of oxidized gold nanoclusters by exposures to foreign gases and irradiation of UV photons has been investigated using X-ray photoelectron spectroscopy. Gold nanoclusters with narrow size distributions protected by alkanethiolate ligands were deposited on a TiO2(1 1 0) surface with dip coating. Oxygen plasma etching was used for removal of alkanethiolate ligands and oxidization of gold clusters. The oxidized gold clusters were exposed to CO, C2H2, C2H4, H2, and hydrogen atoms. Although, C2H4 and H2 did not show any indications of reduction of oxidized gold clusters, CO, C2H2, and hydrogen atoms reduced the oxides on gold cluster surfaces. Among them, hydrogen atoms were most effective for reduction. Irradiation of UV photons around 400 nm could also reduce the oxidized gold clusters. The photochemical reduction mechanism was proposed as follows. The photo-reduction was initiated by electronic excitation of gold clusters and oxygen atoms activated reacted with carbon atoms at the surfaces of gold clusters. Carbon species were likely absorbed in gold clusters or remained at the boundaries between gold clusters when gold clusters agglomerated during oxygen plasma exposures. As the photochemical reduction progressed, carbon atoms segregated to the surfaces of gold clusters. 相似文献
64.
Abe T Matsumoto M Hashimoto S 《The Journal of the Acoustical Society of America》2007,122(5):2697-2705
A time-domain epsilon-filter (TD epsilon-filter) is a nonlinear filter that can reduce noise while preserving a signal that varies drastically, such as a speech signal. Although the filter design is simple, it can effectively reduce noise. It is applicable not only to stationary noise but also to nonstationary noise. It cannot, however, be applied when the amplitude of noise is relatively large. This paper introduces an advanced method for noise reduction that applies an epsilon-filter to complex spectra, namely a time-frequency epsilon-filter (TF epsilon-filter). This paper also introduces noise reduction combining a TD epsilon-filter and a TF epsilon-filter. An advanced method called a variable time-frequency epsilon-filter is also proposed. First, the algorithm of the TD epsilon-filter is explained to clarify the problem. Then, the algorithms of the proposed methods are explained. By utilizing an epsilon-filter in the frequency domain, the proposed method can reduce not only noise that has a relatively small amplitude but also noise that has a relatively large amplitude. Experimental results are also given to demonstrate the performance of the proposed methods in comparison to the results of some conventional methods. 相似文献
65.
Sohei Okazaki Noriaki Okazaki Hidetaka Sugaya Ryota Takahashi Yuji Matsumoto Hideomi Koinuma Tetsuya Hasegawa 《Applied Surface Science》2006,252(7):2615-2621
We developed a scanning microwave microscope (SμM) designed for high-throughput electric-property screening as well as for rapid construction of electronic phase diagrams at low temperatures. As a sensor probe, we used a high-Qλ/4 coaxial cavity resonator to which a thin needle with ball-tip end was attached. The sensor module was mounted on the low-temperature XYZ stage, which allowed us to map out the change of resonance frequency and quality factor due to the local tip-sample interaction at low temperatures. From the measurements of combinatorial thin films, such as Ti1−xCoxO2−δ and Nd0.9Ca0.1Ba2Cu3O7−δ (NCBCO), it was demonstrated that this SμM system has enough performance for the high-throughput characterization of sample conductance under variable temperature conditions. 相似文献
66.
Hideo Matsumoto 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2009,85(2):69-82
This review addresses the distribution of genetic markers of immunoglobulin G (Gm) among 130 Mongoloid populations in the world. These markers allowed the populations to be clearly divided into 2 groups, the northern and southern groups. The northern group is characterized by high frequencies of 2 marker genes, ag and ab3st, and an extremely low frequency of the marker gene afb1b3; and the southern group, in contrast, is indicated by a remarkably high frequency of afb1b3 and low frequencies of ag and ab3st. Based on the geographical distribution of the markers and gene flow of Gm ag and ab3st (northern Mongoloid marker genes) from northeast Asia to the Japanese archipelago, the Japanese population belongs basically to the northern Mongoloid group and is thus suggested to have originated in northeast Asia, most likely in the Baikal area of Siberia. 相似文献
67.
Yousuke Fukaya Takashi Yanase Yasushi Kubota Shigeki Imai Taketoshi Matsumoto Hikaru Kobayashi 《Applied Surface Science》2010,256(18):5610-5613
We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5-10 nm) SiO2/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 °C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO2 layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 × 1022 atoms/cm2, and it increases by POA at 400 °C in wet-oxygen (2.32 × 1022 atoms/cm2) or dry-oxygen (2.30 × 1022 atoms/cm2). The leakage current density is considerably low (e.g., 10−5 A/cm2 at 8 MV/cm) and it is greatly decreased (10−8 A/cm2 at 8 MV/cm) by POA at 400 °C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO2 layer, and decreases the density of oxide fixed positive charges. 相似文献
68.
Masahito Katto Hironari Zushi Wataru Nagaya Shinya Harano Ryota Matsumoto Atushi Yokotani Masanori Kaku Shoichi Kubodera Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2010,101(2):297-301
We have developed intense vacuum ultraviolet (VUV) radiation sources for advanced material processing, such as photochemical
surface reactions and precise processing on a nanometer scale. We have constructed a new VUV laser system to generate sub-picosecond
pulses at the wavelength of 126 nm. A seed VUV pulse was generated in Xe as the 7th harmonic of a 882-nm Ti:sapphire laser.
The optimum conversion was achieved at the pressure of 1.2 Torr. The seed pulse will be amplified by the Ar2*\mathrm{Ar}_{2}^{*} media generated by an optical-field-induced ionization Ar plasma produced by the Ti:sapphire laser. We have obtained a gain
coefficient of g=0.16 cm−1. Our developing system will provide VUV ultra-short pulses with sub-μJ energy at a repetition rate of 1 kHz. 相似文献
69.
Hong FL Minoshima K Onae A Inaba H Takada H Hirai A Matsumoto H Sugiura T Yoshida M 《Optics letters》2003,28(17):1516-1518
A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands. 相似文献
70.
Low-energy spin excitations of La(1.85)Sr(0.15)Cu(1-y)Zn(y)O4 were studied by neutron scattering. In y=0.004, the incommensurate magnetic peaks show a well-defined "spin gap" below T(c). The magnetic signals at omega=3 meV decrease below T(c)=27 K for y=0.008, also suggesting the gap opening. At lower temperatures, however, the signal increases again, implying a novel in-gap spin state. In y=0.017, the spin gap vanishes and elastic magnetic peaks appear. These results clarify that doped Zn impurities induce the novel in-gap state, which becomes larger and more static with increasing Zn. 相似文献