全文获取类型
收费全文 | 3855篇 |
免费 | 53篇 |
国内免费 | 6篇 |
专业分类
化学 | 2707篇 |
晶体学 | 14篇 |
力学 | 36篇 |
数学 | 560篇 |
物理学 | 597篇 |
出版年
2021年 | 25篇 |
2016年 | 51篇 |
2015年 | 45篇 |
2014年 | 39篇 |
2013年 | 98篇 |
2012年 | 80篇 |
2011年 | 96篇 |
2010年 | 65篇 |
2009年 | 88篇 |
2008年 | 111篇 |
2007年 | 122篇 |
2006年 | 125篇 |
2005年 | 129篇 |
2004年 | 112篇 |
2003年 | 98篇 |
2002年 | 126篇 |
2001年 | 64篇 |
2000年 | 75篇 |
1999年 | 66篇 |
1998年 | 65篇 |
1997年 | 55篇 |
1996年 | 53篇 |
1995年 | 74篇 |
1994年 | 59篇 |
1993年 | 64篇 |
1992年 | 56篇 |
1991年 | 50篇 |
1990年 | 63篇 |
1989年 | 85篇 |
1988年 | 55篇 |
1987年 | 68篇 |
1986年 | 67篇 |
1985年 | 92篇 |
1984年 | 71篇 |
1983年 | 60篇 |
1982年 | 66篇 |
1981年 | 60篇 |
1980年 | 70篇 |
1979年 | 76篇 |
1978年 | 87篇 |
1977年 | 90篇 |
1976年 | 66篇 |
1975年 | 55篇 |
1974年 | 53篇 |
1973年 | 48篇 |
1972年 | 35篇 |
1971年 | 37篇 |
1970年 | 23篇 |
1968年 | 27篇 |
1960年 | 23篇 |
排序方式: 共有3914条查询结果,搜索用时 78 毫秒
991.
Christen M Hünenberger PH Bakowies D Baron R Bürgi R Geerke DP Heinz TN Kastenholz MA Kräutler V Oostenbrink C Peter C Trzesniak D van Gunsteren WF 《Journal of computational chemistry》2005,26(16):1719-1751
We present the latest version of the Groningen Molecular Simulation program package, GROMOS05. It has been developed for the dynamical modelling of (bio)molecules using the methods of molecular dynamics, stochastic dynamics, and energy minimization. An overview of GROMOS05 is given, highlighting features not present in the last major release, GROMOS96. The organization of the program package is outlined and the included analysis package GROMOS++ is described. Finally, some applications illustrating the various available functionalities are presented. 相似文献
992.
993.
Günther Kraft und Heinz Dosch 《Fresenius' Journal of Analytical Chemistry》1972,260(4):261-267
Zusammenfassung Wichtige Einflußgrößen für voltametrische Indikationen sind neben der Titrationsgeschwindigkeit die Polarisationsstromdichte, die Menge an zu titrierender Substanz und die Titranskonzentration. Als optimale Bedingungen werden ermittelt: 0,001 M Maßlösungen bei Polarisationsströmen von 1 A für Drahtelektroden von je 10 mm2 Oberfläche und Arbeiten in Titrationsvolumina von 30–50 ml. Wird in Volumina von etwa 2 ml titriert, können die Polarisationsströme etwa um den Faktor 5 höher sein. Der Titrationsverbrauch soll zwischen etwa 3 und 7 ml liegen, die Titrationsgeschwindigkeit kleiner als 0,2 ml/min sein. Für Titrationen von 250–500 g Zn werden so Genauigkeiten von 0,6 g erreicht.Die Optimierung der Versuchsbedingungen hat ferner Wege für Titrationen von wenigen Nanogramm Metall eröffnet und dazu geführt, daß voltametrische und amperometrische Indikationskurven mit voll vergleichbarem Habitus und korrespondierender Absolutlage erhalten werden.
Vortrag anläßlich der Analytikertagung in Düsseldorf am 3. und 4. 6. 1971. 相似文献
Optimization of experimental parameters for the voltametric indication of complexometric titrations
Essential factors of influence for voltametric indications are the titration rate, the polarization current density, the amount of substance to be titrated and the concentration of the titrating solution. Optimum conditions are: 0.001 M volumetric solutions, polarization currents of 1 A, wire electrodes of 10 sq. mm surface each and titration volumes of 30 to 50 ml. If the titration is performed in about 2 ml, the polarization currents may be about 5-fold higher. The consumption of titrating solution should be within the range of 3 to 7 ml and the titration rate inferior to 0.2 ml/min. In this way, accuracies of 0.6 g are reached for titrations of 250–500 g Zn.The optimization of the conditions has furthermore opened possibilities for titrations of a few ng of metal only and permits to obtain voltametric and amperometric indication curves, whose shapes and positions in the mV and A scale, respectively, are fully comparable.
Vortrag anläßlich der Analytikertagung in Düsseldorf am 3. und 4. 6. 1971. 相似文献
994.
Heinz Oberhammer 《Journal of Molecular Structure》1978,48(3):389-394
The molecular structure of bis(trifluoromethyl)mercury has been determined by electron diffraction of gases. The best agreement between experiment and model was obtained for freely rotating CF3 groups and the following geometric parameters (r°α values): C-F = 1.345(3) Å, Hg-C = 2.101(5) Å and <FCF = 106.8°(0.2). The effect of CH3/CF3 substitution on the Hg-C bond length is discussed. 相似文献
995.
Heinz J. Dietrich 《Journal of polymer science. Part A, Polymer chemistry》1968,6(8):2255-2264
The polymerizations of the novel 2-(chlorinated methyl)-4-methylene-1,3-dioxolanes derived from mono-, di-, and trichloroacetaldehyde were investigated. Poly-2-trichloromethyl-4-methylene-1,3-dioxolane was of particular interest because of its high hydrolytic stability and nonflammability. The monomers could be polymerized with cationic catalysts via the methylene functions without cleavage of the dioxolane rings. This selectivity was due to the acetal-stabilizing negative substituents and to the use of Lewis acid complexes of low reactivity as catalysts. In contrast to previously reported poly-4-methylene-1,3-dioxolanes, the title polymers were high-melting colorless solids of good to excellent fire resistance. 相似文献
996.
Dieter Fenske Heinz Teichert Heinz Prokscha Werner Renz Hermann J. Becher 《Monatshefte für Chemie / Chemical Monthly》1980,111(1):177-191
The unusual properties of bis(diphenylphosphino)maleic anhydride and similar ditertiary phosphines has prompted the synthesis of analogous arsines and stibines. Bis(diphenylarsino)maleic anhydride,-maleic thioanhydride and-N-methyl maleic imide, bis(diphenylstibino)maleic anhydride (5) and-maleic thioanhydride are obtained as crystalline yellow or red compounds by the reaction of the corresponding 2,3-dichloromaleic acid derivatives with diphenyl(trimethylsilyl)arsine and-stibine resp. The uv/vis spectra and characteristic i.r. bands of selected compounds are given and compared with those of the corresponding phosphines. The strong shift of C=C to lower wavenumbers observed in all compounds has caused the determination of crystal and molecular structure of5 by x-ray diffraction. Bond distances and angles are given. The complex formation of the new diarsine ligands has been examined by the preparation of Ni-, Cr- and Mo-carbonyl derivatives. As the first organylsulfane substituted maleic acid derivatives bis(phenylthio)maleic thioanhydride,-N-methyl-maleic imide and-maleic acid dimethylester are synthesized and described. 相似文献
997.
From equilibration experiments with ferrocenyl cyclohexanes substituted at position 4, an average conformational free enthalpy of 2.9±0.1 kcal/mole was established for the ferrocenyl group. The spatial requirement of ferrocenyl at the equilibrium equatorial ? axial is approximately equivalent to that of the phenyl residue (3.0±0.1 kcal/mole). 相似文献
998.
As the first set of stereomeric donor-acceptor cyclophanes with TCNQ as an acceptor, and were synthesized; their charge-transfer absorptions differ strongly as a consequence of the different donor-acceptor orientation. 相似文献
999.
Tetraphenylcyclobutadienepalladium dichloride reacts with 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene or with sodium with abstraction of halide to give the sandwich compound bis(tetraphenylcyclobutadiene)palladium(0). The structure of the latter is elucidated by spectroscopic methods and its reactions with Br2, H2, K and HNO3 are described. 相似文献
1000.
Rainer Kahner Benedikt Waerder Hasan Kemal Arslan Heinz Rehage 《Colloid and polymer science》2010,288(4):461-468
In this publication we describe a new self-association process, which leads to the formation of ultra-thin alginate layers
at the interface between oil and water. The water phase contains a highly dilute solution of sodium alginate. These macromolecules
are negatively charged and they are not surface active. The oil phase contains a small concentration of positively charged
surfactants. At the interface between oil and water, the cationic surfactants tend to form complexes with the negatively charged
alginate polyelectrolytes in the aqueous solutions. This leads to striking adsorption processes of the solved polysaccharide
molecules at the oil-water interface. Upon the addition of calcium ions, a cross-linking process sets in and one obtains the
thin viscoelastic membranes, which are anchored at the interface between oil and water. The thickness of these membranes is
of the order of 0.2 mm. Similar structures can also be formed by solving positively charged Gemini surfactants in the oil
phase. In this case, the cationic surfactant molecules induce the adsorption processes of alginate macromolecules, and they
also act as cross-linking compounds. In a series of experiments, we measured the surface rheological properties of these ultra-thin
alginate membranes. The results of these investigations point to the presence of electrostatically stabilized membranes. Special
interest was given to the influence of the guluronate content of the alginates, which is important for the cross-linking mechanism
according to the egg-box model. Finally, this article finishes with the discussion of the proposed building mechanisms of
these membranes. 相似文献