全文获取类型
收费全文 | 46755篇 |
免费 | 1299篇 |
国内免费 | 13篇 |
专业分类
化学 | 28435篇 |
晶体学 | 238篇 |
力学 | 762篇 |
综合类 | 1篇 |
数学 | 8765篇 |
物理学 | 9866篇 |
出版年
2023年 | 334篇 |
2022年 | 290篇 |
2021年 | 469篇 |
2020年 | 672篇 |
2019年 | 624篇 |
2018年 | 962篇 |
2017年 | 878篇 |
2016年 | 1695篇 |
2015年 | 1401篇 |
2014年 | 1354篇 |
2013年 | 3069篇 |
2012年 | 2892篇 |
2011年 | 2703篇 |
2010年 | 1812篇 |
2009年 | 1511篇 |
2008年 | 2384篇 |
2007年 | 2156篇 |
2006年 | 1922篇 |
2005年 | 1990篇 |
2004年 | 1717篇 |
2003年 | 1431篇 |
2002年 | 1242篇 |
2001年 | 966篇 |
2000年 | 957篇 |
1999年 | 664篇 |
1998年 | 513篇 |
1997年 | 435篇 |
1996年 | 576篇 |
1995年 | 409篇 |
1994年 | 484篇 |
1993年 | 441篇 |
1992年 | 470篇 |
1991年 | 394篇 |
1990年 | 443篇 |
1989年 | 360篇 |
1988年 | 367篇 |
1987年 | 329篇 |
1986年 | 320篇 |
1985年 | 446篇 |
1984年 | 410篇 |
1983年 | 324篇 |
1982年 | 326篇 |
1981年 | 342篇 |
1980年 | 279篇 |
1979年 | 272篇 |
1978年 | 270篇 |
1977年 | 260篇 |
1976年 | 279篇 |
1974年 | 250篇 |
1973年 | 263篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
G. Horányi 《Journal of Radioanalytical and Nuclear Chemistry》1989,137(1):23-28
The role of electrochemistry in the discovery and interpretation of the alleged cold nuclear fusion is discussed. 相似文献
162.
A simple and accurate method is described for the determination of acctyl groups in various organic compounds. The compound is dissolved or suspended in absolute methanol and saponified with a known quantity of potassium methylate solution. The excess potassium methylate is then hydrolysed and determined as potassium hydroxide by titration, an appropriate indicator being used. 相似文献
163.
Aimée Arias-Carbajal Reádigos Roberto Cao Vázquez José R. del Bosque Arin 《Transition Metal Chemistry》1989,14(1):42-44
Summary The electronic properties of a series of cobalt(III)trans-furyldioximato-complexes of the type [CoB(FH)2X] (B=NH3, X=Cl, Br, I or NO2; B=pyridine (py) or thiocarbamide (thio), X=Cl or Br; B=imidazole (imid), X=Br), [Co(FH2)(FH)Cl2] and [Co(thio)2(FH)2]NO3 were studied by i.r., u.v. and1H and13C n.m.r. spectra The results were compared with those from the corresponding dimethylglyoximato-complexes. It was concluded that -conjugation over the equatorial plane in the furyldioximates is greater than in the dimethylglyoximates. There is some evidence of thetrans-influence of the anionic ligands in the ammines which are in the order NO
2
–
>Br–>Cl–. 相似文献
164.
E. Havránek A. Bumbálová J. Čižmárik 《Journal of Radioanalytical and Nuclear Chemistry》1984,85(1):21-31
The applicability of two nuclear analytical methods for the determination of hepatacaine hydrochloride in solution was studied, i. e. radionuclide X-ray fluorescence analysis and radiometric titrations based on precipitate formations. Methods used were evaluated on the basis of obtained sensitivity values. 相似文献
165.
In this paper we study theoretically the molecular structure of [Be(C5Me5)2], with special interest in similarities and differences found in the computed geometric parameters, depending on the treatment of the electron correlation used. Given the low energy differences found between the different configurations studied (less than 4 kcal mol−1), and the high fluxionality found in experimental studies for this compound, we analyzed the dynamics of the system by means of first principles molecular dynamics calculations. A complex dynamics is found and analyzed in terms of two molecular rearrangement processes: 1,2-sigmatropic intraring rearrangement and a ring inversion mechanism that interchanges the roles (with regard to their coordination to the central Be atom) of the two rings.Dedicated to Dr. Jeal Paul Malrieu on occasion of his 65th birthday. 相似文献
166.
A new variation of isotope dilution analysis based on double labelling and carried out on filter paper is described. The determination of microgram and submicrogram amounts of silver (labelled with (110m)Ag) by precipitation with iodide (labelled with (131)I) and of calcium (labelled with (45)Ca) by precipitation with phosphate (labelled with (32)P) are given as examples. In the first example the two radio-elements ((110m)Ag and (131)I) are measured by gamma-spectrometry, in the second one ((45)Ca and(32)P) by a beta-absorption method. A number of results show the usefulness of the method. 相似文献
167.
János Bognár 《Mikrochimica acta》1968,56(3):455-472
Zusammenfassung Durch die Einführung von Landoltschen Reaktionen auf Brom- bzw. Chlorgrundlage kann festgestellt werden, daß die heute bekannten Landoltschen Reaktionen, ganz allgemein gesprochen, katalytische Systeme sind. Die heute bekannten Landoltschen Redoxreaktionen sind im wesentlichen halogenkatalytische Reaktionen. Die Landoltschen Reaktionen auf Säure-Basen-Grundlage sind Fälle der Säure-Basen-Katalyse. Die ursprüngliche Landoltsche (Jodat-Sulfit-)Reaktion und analoge Reaktionen sind autokatalytische Systeme.
Summary By applying Landolt reactions to bromo- or chloro-based materials it was found that the now familiar Landolt reactions are catalytic systems in the general sense. The Landolt redox reactions known at present are essentially halogeno-catalytic reactions. The Landolt reactions on acid-base basis are instances of acid-base catalysis. The original Landolt (iodatesulfite) reaction and analogous reactions are autocatalytic systems.相似文献
168.
The liquid membrane extraction (MX) and the solvent extraction (SX) of pertechnetate with Aliquat 336 as a carrier has been studied. From the results of SX the percentage of pertechnetate in the inner solution in experiment with LM was proposed. It has been found that the pertraction of pertechnetate depends on the inner solution used and the most effective solutions were those with ClO
4
–
and SCN–. Effects of the carrier concentration in membranes and outer phase composition have been studied too. The results of these experiments were kinetic curves with a minimum, which may be interpreted as a result of competing processes in the systems. 相似文献
169.
Béla Lôránt 《Thermochimica Acta》1974,9(1):67-75
Complexes were prepared of zinc(II), cadmium(II), manganese(II) mercury (I and II), uranium, thorium(IV), lanthanum and iron ions with pyridine, isoquinoline, αα-dipyridyl, or o-phenanthroline ligands and bichromate or chromate ions as described on pp. 205–207 of Ref. 1. 相似文献
170.
Fernández-Nieves A de las Nieves FJ Fernández-Barbero A 《The Journal of chemical physics》2004,120(1):374-378
We perform static light scattering experiments on a dilute suspension of microgel particles and model the resultant form factors Pq by assuming an exponentially decaying dielectric permittivity. The result is that Pq is a Lorentzian function of the scattering wavevector q for length scales greater than the particle size; the width approximately corresponding to twice the particle radius. This simple model reasonably accounts for scattered light from both swollen and shrunken microgel phases. 相似文献