全文获取类型
收费全文 | 1411篇 |
免费 | 35篇 |
专业分类
化学 | 1011篇 |
晶体学 | 10篇 |
力学 | 15篇 |
数学 | 97篇 |
物理学 | 313篇 |
出版年
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 20篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 55篇 |
2012年 | 46篇 |
2011年 | 84篇 |
2010年 | 51篇 |
2009年 | 47篇 |
2008年 | 73篇 |
2007年 | 88篇 |
2006年 | 74篇 |
2005年 | 52篇 |
2004年 | 55篇 |
2003年 | 66篇 |
2002年 | 45篇 |
2001年 | 33篇 |
2000年 | 24篇 |
1999年 | 22篇 |
1997年 | 31篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 16篇 |
1993年 | 25篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1966年 | 7篇 |
排序方式: 共有1446条查询结果,搜索用时 109 毫秒
1.
Tetsuo Irifune Chiaki Ueda Shohei Ohshita Hiroaki Ohfuji Takehiro Kunimoto Toru Shinmei 《高压研究》2020,40(1):96-106
ABSTRACTNano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25?GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ~1700°C at 15?GPa to ~1900°C at 25?GPa. The NPD having grain sizes less than ~50?nm was synthesized at temperatures below ~2000°C at 15?GPa and ~2300°C at 25?GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10?nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions. 相似文献
2.
3.
Phosphonic acid analogues of acylcarnitine were prepared in an optically active form expecting CPT I inhibitory activities. The synthetic methodology was based on catalytic asymmetric dihydroxylation of β,γ-unsaturated phosphonates and subsequent regioselective amination via the cyclic sulfates. 相似文献
4.
An optical fiber multi-function device consisting of a single gradient-index-rod lens and a multi-facet blazed reflection
grating is proposed to simultaneously realize functions of wavelength demultiplexing and optical signal distribution in a
multimode optical fiber transmission system. We analyzed the demultiplexing characteristics and the tolerance of optical components
using the ray trace method. This device can realize not only low loss optical signal distribution but also offers improved
demultiplexing characteristics in comparison with the previously proposed demultiplexer-multiposition switch. The following
characteristics are expected from the design using commercially available optical components: a working band of 0.64–0.88
μm, channel separation of 34–36 nm, 3 dB bandwidth of 27–28 nm, channel cross-talk of less than - 40 dB and minimum excess
insertion loss of 0.9–2.1 dB. 相似文献
5.
A. I. Fedoseev S. G. Lushnikov S. N. Gvasaliya S. Kojima 《Physics of the Solid State》2006,48(6):1102-1105
The behavior of acoustic phonons in crystals of a relaxor ferroelectric, namely, the lead scandium tantalate PbSc1/2Ta1/2O3 (PST), is studied in the vicinity of the diffuse phase transition. The behavior of longitudinal and transverse acoustic phonons in a PST single crystal is examined using Brillouin scattering. The phonon subsystem is found to behave anomalously in the vicinity of T = 297 K, which can probably be assigned to the existence of a phase transition. Analysis of the results obtained yields the values of the elastic moduli C11, C12, and C44 for the cubic phase of the crystal over a wide temperature range. 相似文献
6.
7.
M. Wada Y. Ishida T. Nakamura Y. Kanai T. M. Kojima A. Takamine Y. Yamazaki K. Okada A. Yoshida T. Kubo I. Katayama S. Ohtani V. Varentsov H. Wollnik V. Lioubimov H. A. Schuessler 《Hyperfine Interactions》2006,173(1-3):153-163
A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being build as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell. The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of dc electric fields and inhomogeneous rf fields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV 8Li ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. Recently our first spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic ions of 10Be and 7Be from the RIPS were trapped and laser cooled in a linear rf trap and the specific mass shifts of these isotopes were measured for the first time. 相似文献
8.
9.
K. M. Kojima 《Applied magnetic resonance》1997,13(1-2):111-122
Muon spin relaxation (μSR) and nuclear magnetic resonance (NMR) are powerful probes of magnetism, which have been extensively applied to studies of spin gap systems. Comparison of results obtained with the two techniques gives complementary results, as each is sensitive to different aspects of spin gap magnetism. We discuss recent μSR measurements of the spin ladder compounds Sr n?1Cu n+1O2n , pure and doped Haldane materials (Y2?x Ca x )Ba(Ni1?y Mg y )O5, and doped spin Peierls compounds (Cu1?x Zn x )(Ge1?y Si y )O3. 相似文献
10.
Using temperature-modulated
differential scanning calorimetry, the melting behaviour of poly(oxytetramethylene)-alt-(aromatic oligoamide) (POTM-alt-AOA)
has been studied in comparison with that of polyoxytetramethylene glycohols
(POTMGs). The apparent melting temperature of the block copolymers is found
to be less than that of the corresponding POTMGs by approximately 30°C.
The relaxation time of melting of a POTM segment has been estimated and compared
with that of POTMG. The relaxation time of POTM-alt-AOA
is slightly shorter than that of POTMG when the molar mass of the POTM segment
is 2900; however, it is longer when the molar mass is 1400. 相似文献