全文获取类型
收费全文 | 346篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 335篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 2篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 15篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 23篇 |
2006年 | 25篇 |
2005年 | 22篇 |
2004年 | 26篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有355条查询结果,搜索用时 15 毫秒
91.
Ayako Sekine Noriaki Seko Masao Tamada Yoshio Suzuki 《Radiation Physics and Chemistry》2010,79(1):16-21
A fibrous adsorbent for Hg ions was synthesized by radiation-induced emulsion graft polymerization of glycidyl methacrylate (GMA) onto a nonwoven cotton fabric and subsequent chemical modification. The optimal pre-irradiation dose for initiation of the graft polymerization of GMA, which minimized the effects of radiation damage on the mechanical strength of the nonwoven cotton fabric, was found to be 10 kGy. The GMA-grafted nonwoven cotton fabric was subsequently modified with ethylenediamine (EDA) or diethylenetriamine (DETA) to obtain a Hg adsorbent. The resulting amine-type adsorbents were evaluated for batch and continuous adsorption of Hg. In batch adsorption, the distribution coefficients of Hg reached 1.9×105 and 1.0×105 for EDA- and DETA-type adsorbents, respectively. A column packed with EDA-type adsorbent removed Hg from 1.8 ppm Hg solution at a space velocity of 100 h?1, which corresponds to 16,000 times the volume of the packed adsorbent. The adsorbed Hg on the EDA-type adsorbent could be completely eluted by 1 M HCl solution. A microbial oxidative degradation test revealed that the EDA-type adsorbent is biodegradable. 相似文献
92.
Synthesis, characterization, and catalytic reactivity of a highly basic macrotricyclic aminopyridine
Uchida N Taketoshi A Kuwabara J Yamamoto T Inoue Y Watanabe Y Kanbara T 《Organic letters》2010,12(22):5242-5245
The synthesis methods, physicochemical and structural characteristics, and catalytic reactivity of new macrocyclic proton chelators, N,N',N'-tris(p-tolyl)azacalix[3](2,6)(4-pyrrolidinopyridine) and N,N',N'-tris(p-tolyl)azacalix[3](2,6)(4-piperidinopyridine), are studied. The introduction of pyrrolidino and piperidino groups into the pyridine unit enables the enhancement of the synergistic proton affinity of the cavity of the macrotricycle giving a high basicity (pK(BH+) = 28.1 and 27.1 in CD(3)CN), resulting in a catalytic activity for the Michael addition of nitromethane with α,β-unsaturated carbonyl compounds. 相似文献
93.
We have synthesized lyoniresinol with the combined utilization of synthetic chemistry and biotechnological methods, specifically using plant cell cultures as an "enzyme source." 相似文献
94.
Heat capacity measurements have been made on ANBC(18) at temperatures from 8 to 490 K by adiabatic calorimetry. All known phases were detected. The temperatures, enthalpies and entropies of transition were determined for the phase transitions observed. On the basis of the entropy of transition to the SmC phase from the D or cubic phases, it is pointed out that the D phase of ANBC and the cubic phase of BABH might be identical in nature. It is shown that the arrangement of 'molecular' cores has a higher degree of order in the isotropic (D and cubic) phases than in the SmC phase, whereas the terminal alkoxy chains are more disordered in the isotropic phases than in the SmC phase. The degrees of disorder in the D and cubic phases relative to the SmC phase are very similar in terms of the entropy of transition per methylene group. The inverted phase sequence in ANBC (SmC D on heating) and BABH (cubic SmC) can be accounted for in terms of the competing roles in the entropy between the molecular core and the chains. 相似文献
95.
Shimazaki Y Tani F Fukui K Naruta Y Yamauchi O 《Journal of the American Chemical Society》2003,125(35):10512-10513
The one-electron oxidized species of a Ni(II)-phenolate complex has been shown to be in the Ni(II)-phenoxyl radical state at room temperature and the Ni(III)-phenolate state at < -120 degrees C, indicating that the oxidation state is temperature dependent. 相似文献
96.
Juzo Nakayama Ayako Tai Sachiko Iwasa Tomohiro Furuya Yoshiaki Sugihara 《Tetrahedron letters》2005,46(9):1395-1397
It was found that tetracyanoethylene oxide not only oxidizes sulfides to sulfoxides but also reduces sulfoxides to sulfides with generation of two molecules of carbonyl cyanide. The reaction thus also functions as a new method for generation of carbonyl cyanide. 相似文献
97.
Hashizume T. Terayama K. Shimazaki T. Itoh H. Okuno Y. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):1045-1050
We succeeded in studying the mechanism of hydrogen added carbothermic reduction process of iron-manganese oxide by means of
the new technique, simultaneous measurement of evolved gas analysis (EGA) and humidity sensor (HS). Water vapor evolved by
the reduction with hydrogen can be detected by HS. Other gas was detected by TCD. Without carbon, the hydrogen reduction process
was followed to the formation of the intermediate product between MnO and FeO and finally reduction to the mixture of MnO
and Fe. With carbon, the intermediate products between MnO and FeO was formed at about 780 K. The methane was formed in higher
temperature than 1073 K and the reduction with carbon proceeded mainly. At higher temperatures, methane decomposed to yield
nascent carbon that tended to result in the acceleration of the reduction rate with carbon. The study is concerned with the
mechanism of the hydrogen reduction of MnFe2O4 and the effect of without and with carbon on this reduction by means of combining EGA and HS.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
98.
Ohno H Miyamura K Tanaka T Oishi S Toda A Takemoto Y Fujii N Ibuka T 《The Journal of organic chemistry》2002,67(4):1359-1367
A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying the mesyloxy group to the allene was observed. 相似文献
99.
Hosoya T Hiramatsu T Ikemoto T Nakanishi M Aoyama H Hosoya A Iwata T Maruyama K Endo M Suzuki M 《Organic & biomolecular chemistry》2004,2(5):637-641
A novel method for radioisotope-free photoaffinity labeling was developed, in which a bifunctional ligand is connected to a target protein by activation of a photoreactive group, such as an aromatic azido or 3-trifluoromethyl-3H-diazirin-3-yl group, and identification of the ligated product is achieved by anchoring of a detectable tag through the Staudinger-Bertozzi reaction with an alkyl azido moiety that survives photolysis. The chemical ground of this method was confirmed using model compounds with the bifunctional group under photoirradiation in the presence of trapping agents for reactive intermediates. The utility of the method has been demonstrated by specific labeling of the catalytic portion of human HMG-CoA reductase. 相似文献
100.
Stereodivergent synthesis of the 2,3,5,6-tetrasubstituted piperidine ring system has been achieved by sequential stereocontrolled Michael-type conjugate addition reaction of appropriate enaminoesters. This methodology has been applied to the total syntheses of the poison frog alkaloids 223A and 205B. The relative stereochemistry of natural 223A at the 6-position was revised, and the absolute stereochemistry of natural 205B was determined by the present synthesis. 相似文献