全文获取类型
收费全文 | 891篇 |
免费 | 9篇 |
国内免费 | 5篇 |
专业分类
化学 | 653篇 |
晶体学 | 11篇 |
力学 | 6篇 |
数学 | 48篇 |
物理学 | 187篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 31篇 |
2012年 | 28篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 16篇 |
2008年 | 42篇 |
2007年 | 36篇 |
2006年 | 37篇 |
2005年 | 37篇 |
2004年 | 40篇 |
2003年 | 33篇 |
2002年 | 31篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 25篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 29篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 13篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1965年 | 4篇 |
排序方式: 共有905条查询结果,搜索用时 15 毫秒
1.
Daisuke Matsuura 《Tetrahedron letters》2006,47(9):1371-1374
An efficient and stereodefined strategy is described for the asymmetric synthesis of a new styryllactone from the stem bark of Goniothalamus cardiopetalus, cardiobutanolide. The synthetic process is based on requisite manipulation of the functionalized bicyclic lactol-lactone intermediate incorporating the glucuronolactone-derived skeleton in a complete stereoselective manner. 相似文献
2.
Sonoko Kikuchi Kazuteru Kawauchi Sadatsugu Ooki Masaru Kurosawa Hisashi Honjho Teruo Yagishita 《Analytical sciences》2004,20(8):1111-1112
Using Raman spectroscopy without any preparation, we analyzed the brominated flame retardant, polybromodiphenyl ethers (PBDEs), which has been prohibited by the European Union. The typical Raman bands of PBDEs, which are clearly different from those of other brominated flame retardants, are from 100 to 300 cm(-1). In our analysis, the detection limit was about 100 ppm, and the analysis took about 1 min, whereas the usual method of solvent extraction using gas chromatography/mass spectroscopy takes 50 h. 相似文献
3.
T Niwa H Yoshizumi A Tatematsu S Matsuura T Nagatsu 《Journal of chromatography. A》1989,493(2):347-352
4.
Takuya Hasegawa Hirotaka Matsuura Kazumi Inagaki Hiroki Haraguchi 《Analytical sciences》2003,19(1):147-150
The major-to-ultratrace elements in human bone-marrow fluid were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry), and ICP-MS (inductively coupled plasma mass spectrometry). The bone-marrow fluid sample was centrifuged prior to acid digestion to exclude the bone piece from bone marrow, and then digested with nitric acid. As a result, 20 elements could be determined over the concentration range from 1610 microg g(-1) for Na to 0.00043 microg g(-1) for W. It was found that Fe, Zn and Sb were enriched by ca. 264-, 7- and 15-fold, respectively, in bone-marrow fluid, compared to those in human blood serum. Alkali metals (K, Rb, Cs), except for Na, were also significantly enriched in bone-marrow fluid. Furthermore, the concentrations of various elements, such as Fe, P, Al, Zn, Cu, Se, Zr, Sn, Ag and W, were significantly higher than those in open seawater. 相似文献
5.
Katsumasa Iwai Yi-Wei Shi Mitsunobu Miyagi Yuji Matsuura 《Optics & Laser Technology》2007,39(8):1528-1531
An improved coating method was proposed in order to form a uniform polymer layer in the fabrication of cyclic olefin polymer-coated silver (COP/Ag) hollow fiber. A COP solution was flowed in a closed loop, in which the silver-coated tube was used as a part of the loop. Owing to the constant flowing speed of the COP solution and the airtight flowing environment, a COP layer was uniformly formed. The hollow fibers attain high performance and deliver multi-wavelength laser light from the infrared to the visible simultaneously. The method was successfully applied to the fabrication of practical hollow fibers with 2 m length for the near and mid-infrared lasers. 相似文献
6.
HPLC determination of (+)-pseudoephedrine and (-)-ephedrine in Japanese herbal medicines containing Ephedra herb using solid-phase extraction 总被引:2,自引:0,他引:2
Ichikawa M Udayama M Imamura K Shiraishi S Matsuura H 《Chemical & pharmaceutical bulletin》2003,51(6):635-639
We developed a rapid and simple HPLC method combined with solid-phase extraction (SPE) for quantitative analysis of (+)-pseudoephedrine (PEP) and (-)-ephedrine (EP) in Japanese herbal (Kampo) medicines such as Kakkon-to, Sho-seiryu-to, Goshaku-san and Bofu-tsusho-san. SPE was performed on TOYOPAK IC-SP M containing propylsulfonic groups. Determination of PEP and EP was carried out using ion-pair reversed-phase HPLC with sodium dodecyl sulfate. N-Benzyldiethylamine was used as an internal standard. The analytical procedure was validated with regard to specificity, linearity, accuracy, and precision. These data suggest that the analytical method developed in this study is useful for quantitative analysis of PEP and EP in various formulations of Kampo medicine containing Ephedra herb. 相似文献
7.
8.
Abstract— A new method of using hydroxylamine as the reagent was developed to determine the concentrations of chlorophylls a and b in plant extracts accurately and sensitively. The method is based on the principle that hydroxylamine reacts in a short time with the aldehyde group of chlorophyll b in 95 per cent methanol at pH 5.8 to afford a derivative having a red band similar in position to the red band of chlorophyll a , while the spectrum of chlorophyll a is unaffected by the treatment with hydroxylamine. The method includes the measurements of absorbanlce for the mixture of a plant extract with hydroxylamine and for the reagent blank at a single wavelength, 666 mμ, and the concentrations of chlorophylls a and b are calculated from the absorbance value for the reagent blank and the increment of absorbance due to the reaction. By measuring this increment directly by difference photometry, one can determine a low concentration of chlorophyll b relative to chlorophyll a . The contents of chlorophylls in matured and etiolated leaves were determined by the method, and the errors included in this method were shown to be smaller than those in a commonly used technique including the measurements at two different wavelengths. 相似文献
9.
10.
Terai T Araho D Osakabe K Katai M Narama I Matsuura T Katakawa J Tetsumi T Sato M 《Chemical & pharmaceutical bulletin》2000,48(1):142-144
The structure of iso-grayanotoxin II, a new diterpenoid from Leucothoe grayana MAX., has been determined as 3 beta,5 beta,6 beta,14 beta,16 alpha-pentahydroxygrayanotox-9(10)-ene by spectroscopic and X-ray crystallographic analysis. The lethal dosage level of iso-grayanotoxin II in mice was lower than that of grayanotoxin III. 相似文献