全文获取类型
收费全文 | 1402篇 |
免费 | 26篇 |
国内免费 | 5篇 |
专业分类
化学 | 978篇 |
晶体学 | 11篇 |
力学 | 16篇 |
数学 | 57篇 |
物理学 | 371篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 22篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 22篇 |
2013年 | 85篇 |
2012年 | 40篇 |
2011年 | 52篇 |
2010年 | 27篇 |
2009年 | 39篇 |
2008年 | 67篇 |
2007年 | 63篇 |
2006年 | 55篇 |
2005年 | 49篇 |
2004年 | 47篇 |
2003年 | 65篇 |
2002年 | 59篇 |
2001年 | 35篇 |
2000年 | 49篇 |
1999年 | 38篇 |
1998年 | 22篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 41篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 20篇 |
排序方式: 共有1433条查询结果,搜索用时 15 毫秒
941.
T. Idehara K. Shibutani H. Nojima M. Pereyaslavets K. Yoshida I. Ogawa T. Tatsukawa 《International Journal of Infrared and Millimeter Waves》1998,19(10):1303-1316
Electron beam misalignment in a submillimeter-wave gyrotron strongly affects its total efficiency as well as excitation of rotating and counterrotating modes. Some of misalignment phenomena were studied theoretically and experimentally. 相似文献
942.
943.
A flow injection system for the simultaneous determination of uranium and thorium has been developed by using selective masking and a spectrophotometric detector with two flow cells aligned with the same optical path. The injected sample solution was first mixed with a reagent solution containing Chromazurol S (CAS) and cetyltrimethylammonium chloride (CTMAC), and the total absorbance of uranium- and thorium-CAS complexes was measured in the first flow cell at 620 nm. The sample stream was then mixed with an EDTA solution in order to convert the thorium-CAS complex to a thorium-EDTA complex, and the absorbance of the uranium-CAS complex was measured in the second flow cell. The detection limits were 10 microg dm(-3) for uranium and 7 microg dm(-3) for thorium. The calibration graphs were linear (r < 0.9998) at least over the ranges of 0.1 to 10 mg dm(-3) for uranium and 0.08 to 8 mg dm(-3) for thorium. The RSDs were less than 1.5% (n = 3) in the calibration range. Uranium and thorium of up to the 6-fold concentration to each other could be determined in admixtures with relative errors of less than 3.3%. The sample throughput was 24 per hour. The proposed system was successfully applied to the analysis of a uranium-thorium ore mock solution by coupling with anion-exchange in a magnesium nitrate medium to eliminate interference from coexisting elements. 相似文献
944.
Nobuaki Takahashi Weerapong Thongnum Takanari Ogawa Satoshi Tanaka Sumio Takahashi 《Optical Review》2003,10(2):106-110
A fiber-Bragg-grating (FBG) vibration sensor, in which an FBG acts as an intensity-modulator for incident narrow spectrum light such as a laser, is thermally stabilized. Sensitivity of the sensor is kept constant over a wide range of temperature by feeding back a fraction of the output signal into the laser source in such a way that by shifting the oscillation wavelength of the laser the dc component of the detected photocurrent remains unchanged regardless of change in the environmental temperature. Variation in the sensor sensitivity is reduced to as small as 3 dB after the stabilization, although it is more than 55 dB without the stabilization. 相似文献
945.
946.
Kanta Yanagida Hideyuki Ogawa Kaoru Omichi Sumihiro Hase 《Journal of chromatography. A》1998,800(2):1196-198
Addition of a monosaccharide residue to a pyridylaminated (PA)-N-linked sugar chain results in an increment or decrement in the elution time on reversed-phase HPLC, the difference being defined as the partial elution time of the residue. Based on this principle, an empirical rule was deduced, which states that the elution time is roughly equal to the sum of the partial elution times of the component sugar residues [Anal. Biochem., 167 (1987) 321–326]. In practice, however, some partial elution times obtained from different pairs of mother PA-sugar chains are found to deviate, and consequently the closeness of the elution times of PA-sugar chains calculated therefrom to the observed times is reduced in such cases. To improve the reliability of the additivity rule and to generalize elution times so that they are less dependent on minor alterations in the elution conditions, we have devised a new scale for elution time, which we have named a reversed-phase scale. The elution times on the reversed-phase scale (the R values) are read from a conversion curve constructed using the elution times of eight selected standard PA-sugar chains. The partial elution times on the reversed-phase scale of 22 monosaccharide residues were calculated from the R values of 93 PA-sugar chains. The R values obtained by summing the partial elution times of all the component monosaccharide residues became much closer to the R values obtained from the reversed-phase scale, compared to the results obtained using the previous method. In addition, the R values were less influenced by minor change in the elution conditions. These features of the new scale allow more accurate structural assignment of sugar chains. 相似文献
947.
Mixtures of ammonium-nitrate and alcohol (ANA) are usable as range propellants in ballistics. The molecular mass and specific
energy are controlled by altering the type of alcohol used and by varying their molar ratio. This is confirmed by experiments
carried out in a 25-mm-bore single-stage gun with ANA using smokeless powder as igniter. It is found that an important parameter
determining propellant performance is the quantity of the smokeless powder used for igniting the mixture.
Received 23 September 1998 / Accepted 5 May 1999 相似文献
948.
Fe K-edge X-ray absorption fine structure (XAFS) measurements were performed in order to elucidate the formation mechanism of single-walled carbon nanotubes (SWCNTs) grown on natural magnesite by pyrolyzing methane gas. It was clearly shown by XAFS analyses that iron metal fine particles, which were reduced from iron oxides by methane gas, worked as a catalyst for SWCNT growth. Structural characteristics of the initial iron state in the natural magnesite were also discussed. 相似文献
949.
J Sakaguchi H Nishino N Ogawa Y Iwanaga S Yasuda H Kato Y Ito 《Chemical & pharmaceutical bulletin》1992,40(1):202-211
Novel N-[[dialkylamino)ethoxy]benzyl]benzamide derivatives (II-1-51), derived from the structural modification of metoclopramide (I), were synthesized and examined for their pharmacological activities. Among them, N-[4-[2-(dimethylamino)ethoxy]benzyl]-3,4-dimethoxybenzamide (II-34) which exhibited well balanced gastrointestinal prokinetic and antiemetic activities was selected as a new type of gastrointestinal prokinetic agent. 相似文献
950.