全文获取类型
收费全文 | 1644篇 |
免费 | 41篇 |
国内免费 | 8篇 |
专业分类
化学 | 1281篇 |
晶体学 | 19篇 |
力学 | 4篇 |
数学 | 53篇 |
物理学 | 336篇 |
出版年
2023年 | 9篇 |
2020年 | 20篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 104篇 |
2012年 | 80篇 |
2011年 | 75篇 |
2010年 | 55篇 |
2009年 | 58篇 |
2008年 | 92篇 |
2007年 | 108篇 |
2006年 | 112篇 |
2005年 | 96篇 |
2004年 | 85篇 |
2003年 | 85篇 |
2002年 | 61篇 |
2001年 | 33篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 24篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 17篇 |
1974年 | 17篇 |
1973年 | 23篇 |
1968年 | 9篇 |
排序方式: 共有1693条查询结果,搜索用时 93 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.
We demonstrate the potential of femtosecond two-color pulse interferometry for in vitro optical glucose monitoring, by dispersion of the group refractive index in a glucose solution sample with respect to a red-color
light and a blue-color light. By comparison with femtosecond one-color pulse interferometry, the basic performance of the
present system with regard to sensitivity, quantitativeness, and tolerance to surrounding disturbances, is evaluated. The
resulting accuracy and precision of glucose determination are 77 and 118mg/dl for 10-mm-sample-thickness, respectively. This
near-common-path configuration of the two-color pulse light provides good stability to fluctuations of sample temperature,
which is important in clinical applications. Considering the performance of femtosecond two-color pulse interferometry as
an optical glucose sensor, a suitable measurement site for in vivo optical glucose monitoring is discussed. 相似文献
4.
Endoscopic Observation of Tissue by Narrowband Illumination 总被引:6,自引:0,他引:6
Kazuhiro Gono Kenji Yamazaki Nobuyuki Doguchi Tetsuo Nonami Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Hirohisa Machida Yasushi Sano Shigeaki Yoshida Yasuo Hamamoto Takao Endo 《Optical Review》2003,10(4):211-215
We propose a new illumination method for a medical endoscope: narrow band imaging (NBI), in which the spectral bandwidth of the filtered light is narrowed. To confirm how the spectral specifications of the filtered light influence a reproduced image, an experiment was conducted observing the endoscopic images of the back mucosa of a human tongue. In addition, the effect of NBI on endoscopic images was investigated through preliminary clinical tests in colonoscopy and upper gastrointestinal endoscopy. It has been shown that NBI can enhance the capillary pattern and the crypt pattern on the mucosa. These patterns are useful features for diagnosing an early cancer. 相似文献
5.
35Cl NQR as well as heat capacity measurements of [(PyO)H][AuCl4] and its deuterated analog [(PyO)D][AuCl4] revealed successive phase transitions at 70.5 and 62.5 K, and at 71 and 63 K, respectively. The NQR frequency varied continuously through the upper transition point while discontinuously through the lower transition point. In the intermediate-temperature phase a remarkable decrease in the signal intensity was observed. These NQR observations as well as the feature of the heat capacity anomaly in which a broad peak is succeeded by a sharp peak with decreasing temperature suggest a possibility of normal-incommensurate-commensurate phase sequence. 相似文献
6.
Abstract— Irradiation of near-UV light in the presence of FeCl3 caused oxidation of adenosine with concomitant reduction of Fe(III) under either aerobic or anaerobic atmosphere. Major photoproducts were adenine and adenosine-5'-aldehyde, showing that oxidation took place mostly at the ribose moiety of adenosine. Detailed study showed that the reaction proceeded by the light absorption due to Fe(III) at 300-350 nm. 相似文献
7.
In proportion to the environmental pollution problems caused by organotin compounds, the genotoxicities of tin compounds in the environments have become of interest so as to estimate their safety in recent years. In this work, isolated λ-DNA (double-strand DNA) was incubated with inorganic tin(II) and tin(IV) and five organotin compounds [n-butyltin trichloride, di(n-butyltin) dichloride, methyltin trichloride, dimethyltin dichloride and trimethyltin chloride] in reaction systems both with and without hydrogen peroxide (H2O2) content. The tin compounds tested in this study did not induce DNA breakage in the absence of hydrogen peroxide. Divalent inorganic tin (SnCl2) and tetravalent inorganic tin (SnCl4) caused DNA breakage in the presence of hydrogen peroxide (10 mM), and the DNA damage activity of inorganic tin was much more potent in divalent inorganic tin (SnCl2) than in tetravalent inorganic tin (SnCl4). Divalent inorganic tin (SnCl2) induced DNA breakage in a concentration-dependent fashion at concentrations greater than 0.1 mM of SnCl2 in the presence of hydrogen peroxide (10 mM). DNA breakage was not caused by n-butyltin compounds and methyltin compounds either in the presence or in the absence of hydrogen peroxide. 相似文献
8.
9.
Let m be an integer with m3. Let K and K be perfect fields of characteristic p and p such that (p,m)=1 and (p,m)=1, respectively. Moreover let A and A be algebraic function fields over K and K defined by xm+ym=a(0, ak) and xm+ym=a(a0 ak), respectively. Put g=(m–1)(m–2)/2. Denote by M(K,p,a) and M(K,p,a) the Hasse-Witt matrices of A and A with respect to the canonical bases of holomorphic differentials. Then we show that if p+p0(mod.m) then rank M(K,p,a)+rank M(K,p,a)=g and if pp1 (mod.m) then rank M(K,p,a)=rank M(K,p,a). 相似文献
10.
Complexation of a hydrophobic thiazorylazophenol with Ni2+ at sodium dodecylsulfate micellar surface
Complexation of thiazorylazododecylphenol (TADP) with Ni2+ at the surface of sodium dodecylsulfate (SDS) micelles has been spectrophotometrically studied. Complicated spectral changes are analyzed by a factor and multivariate analysis, which implies the formation of [TDAP(OH-)Ni]0 as well as a simple 1:1 complex of Ni2+ with TDAP at the micellar interface. All of the equilibrium constants required to describe this system are substantially affected by electrolyte concentrations. Coexistent electrolytes vary the surface potential of the micelle, and in turn influence the equilibria taking place on the micellar surface. The electrostatic potential estimated based on the equilibrium shifts is more negative than that calculated according to Poisson-Boltzmann theory, which simply involves electrostatic effects. This disagreement is possibly caused by different aqueous environments around the micelle from bulk solution, which also facilitate the formation of unusual complex such as [TDAP(OH-)Ni]0. 相似文献