全文获取类型
收费全文 | 648篇 |
免费 | 34篇 |
国内免费 | 44篇 |
专业分类
化学 | 326篇 |
晶体学 | 14篇 |
力学 | 58篇 |
综合类 | 2篇 |
数学 | 157篇 |
物理学 | 169篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 21篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 106篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 18篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 43篇 |
2000年 | 32篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1973年 | 4篇 |
1969年 | 3篇 |
1967年 | 7篇 |
1966年 | 6篇 |
1965年 | 7篇 |
1964年 | 5篇 |
1962年 | 9篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1956年 | 3篇 |
1955年 | 4篇 |
1933年 | 4篇 |
排序方式: 共有726条查询结果,搜索用时 15 毫秒
11.
H. Enginar P. Ünak F. Yurt F. Zümrüt Biber 《Journal of Radioanalytical and Nuclear Chemistry》2002,251(3):473-479
An oestrogen derivative 3,17-a-oestradiolyl propyl 1,4,8,11-tetraazacyclotetradecanyl-1-(4-methylbenzoic acid)ester (ESTCPTA) that is 3,17-a-oestradiolyl propinol coupled to 1-(4-methylbenzoic acid)1,4,8,11-tetraazacyclotetradecane (CPTA) was synthesized in five steps. The product was purified by recrystallization in ethyl alcohol, and analysed by NMR and IR spectroscopy. ESTCPTA was labeled with 99mTc and radio thin layer chromatography (RTLC) and radio-paper electrophoresis were used to determine the radiochemical yields. Specific activity was approximately 23.7 GBq/mmol and the labeling yield was over 95%. The biodistribution studies were performed on female Albino Wistar rats. The rats were sacricified by ether narcotization at certain time intervals and the activity of the organs was counted by a gamma counter. The activity per gram tissue was calculated and time activity curves were generated. 相似文献
12.
Y. D. Kurt G. S. Pozan İ. Kızılcıklı B. Ülküseven 《Russian Journal of Coordination Chemistry》2007,33(11):844-849
Mixed ligand complexes of dioxomolybdenum(VI) with 2-hydroxybenzaldehyde 4-phenyl-S-methylthiosemicarbazone (H2L) were prepared with the formula [MoO2(L)D] (D = H2O, methyl, n-butyl, and n-undecyl alcohol, DMF, DMSO, pyridine, 4-picoline, and 3,5-lutidine). The compounds were characterized by elemental
analysis, IR and 1H NMR spectroscopy. The thermal decomposition of the compounds were investigated by using TGA, DTG, and DTA methods in air,
and the thermal behavior depending on the second ligand molecule was discussed. A single crystal of the DMF coordinated complex
was studied by X-ray diffractometry.
The text was submitted by the authors in English. 相似文献
13.
Template reactions of 2,4-dihydroxy-, 2,5-dihydroxy-, 2-hydroxy-3-methoxy- and 2-hydroxy-4-methoxy-benzaldehyde with methoxy- and hydroxy-substituted salicylaldehyde S-methylthiosemicarbazones in the presence of NiCl2 and FeCl3 resulted in the corresponding hydroxy- and methoxy-substituted N1,N4-diarylidene-S-methylthiosemi-carbazone complexes. Characterization of the compounds, [Fe(L)Cl] and [Ni(L)], was accomplished by means of elemental analysis, conductivity and magnetic measurements, i.r. and 1H-n.m.r. spectra. A systematic trend has been observed for the chemical shift values of the aromatic protons in the spectra of complexes. 相似文献
14.
8-Hydroxyquinoline (8-HOQ) is known as an important chelating agent for several metal ions. This compound is practically insoluble in water. For this reason, in this study its water soluble sulfate salt has been used for complexing uranyl ions and the stability constants of the complex have been determined. The Irving-Rosotti method computing the Calvin-Bjerrum pH-titration data, was applied. Finally, the stability constants of the complex formed between (8-HOQN-H)2SO4 and uranyl ions were found to be lgK1=8.25 and lgK2=4.15, the overall stability constant being {ie55-1}. 相似文献
15.
Summary Let (W, H, ) be an abstract Wiener space and letR(w) be a strongly measurable random variable with values in the set of isometries onH. Suppose that Rh is smooth in the Sobolev sense and that it is a quasi-nilpotent operator onH for everyhH. It is shown that (R(w)h) is again a Gaussian (0, |h|
H
2
)-random variable. Consequently, if (e
i
,i)W
* is a complete, orthonormal basis ofH, then
defines a measure preserving transformation, a rotation, onW. It is also shown that if for some strongly measurable, operator valued (onH) random variableR, (R(w+k)h) is (0, |h|
H
2
)-Gaussian for allk, hH, thenR is an isometry and Rh is quasi-nilpotent for allHH. The relation between the stochastic calculi for these Wiener pathsw and
, as well as the conditions of the inverbibility of the map
are discussed and the problem of the absolute continuity of the image of the Wiener measure under Euclidean motion on the Wiener space (i.e.
composed with a shift) is studied.The research of the second author was supported by the Fund for the Promotion of Research at the TechnionDedicated to the memory of Albert Badrikian 相似文献
16.
Ülo Lumiste 《Results in Mathematics》1995,27(3-4):284-301
The orbits of Lie groups acting in Euclidean spaces by isometries are extrinsically symmetric iff they are parallel, i.e. satisfy ${\overline \nabla} h =0 $ Submanifolds characterized by the integrability condition $ {\overline R}\o\ h =0 $ of this system ${\overline \nabla} h =0$ are called semi-parallel (or semi-symmetric, extrinsically); they are the 2nd order envelopes of the symmetric orbits. For the orthogonal Veronese action, corresponding to the map well-known from the algebraic geometry, all symmetric orbits will be determined, as well as their 2nd order envelopes. The results are essential for the classification of the semi-parallel submanifolds. 相似文献
17.
A. Ülger 《Monatshefte für Mathematik》1996,121(4):353-379
LetA be a commutative Banach algebra with a nonempty spectrum A. By weak we denote the relative weak topology induced on A by (A
*,A
**). In this note we study some properties of the topological space (A, weak) and present some applications of the results obtained and tools used to amenability, weakly compact homomorphisms, weakly compact subsets of the spectrum of the uniform algebras and to a characterization of the synthesizable ideals of the algebraA. 相似文献
18.
Takuma Shinya Nakashima Noriyuki Tantirungkij Manee Kinoshita Shinichi Okada Hirosuke Sew TatsÜji Yoshida Toshiomi 《Applied biochemistry and biotechnology》1991,28(1):327-340
Applied Biochemistry and Biotechnology - A NADPH/NADH-dependent xylose reductase gene was isolated from the xylose-assimilating yeast,Pichia stipitis. DNA sequence analysis showed that the gene... 相似文献
19.
H. Ozakay P. Ünak Z. Biber F. Yurt 《Journal of Radioanalytical and Nuclear Chemistry》1998,230(1-2):231-233
The most suitable way of determination iodine-deficiency is to measure iodine concentrations in water and urine. For this reason, a method that can determine iodide concentrations in drinking water and suitable for routine analysis, is developed. Water samples have been collected from four Aegean localities: Izmir, Salihli, Ödemis and Tire situated in the western Turkey. The method is based on substochiometric isotope dilution analysis. Iodile concentrations vary within 9.86–85.14 μg/l ranges in the analyzed samples. Mean value is 44.92±22.07 μg/l. 相似文献
20.
Labeling conditions of synkavit (2-methyl-1,4-naphthoquinol disodium phosphate) with iodine-125 have been studied. In this study, labeling temperature, reaction time, successive using of iodogen coated tubes, iodogen amount and synkavit concentrations have been determined to get optimum conditions for maximum labeling. Final results showed that when the labeling temperature, reaction time, synkavit concentration, and iodogen amount were, at room temperature, 15 min (in the case of successive using of three iodogen coated tubes), 2 mg ml–1 and 5 mg, respectively; labeling yield was 90% and specific activities of the order of 555 GBq mmol–1 (15 Ci mmol–1) have been obtained. 相似文献