全文获取类型
收费全文 | 2692篇 |
免费 | 48篇 |
国内免费 | 5篇 |
专业分类
化学 | 1706篇 |
晶体学 | 13篇 |
力学 | 27篇 |
数学 | 505篇 |
物理学 | 494篇 |
出版年
2020年 | 27篇 |
2019年 | 29篇 |
2016年 | 39篇 |
2015年 | 23篇 |
2014年 | 37篇 |
2013年 | 82篇 |
2012年 | 54篇 |
2011年 | 82篇 |
2010年 | 59篇 |
2009年 | 42篇 |
2008年 | 76篇 |
2007年 | 78篇 |
2006年 | 61篇 |
2005年 | 90篇 |
2004年 | 79篇 |
2003年 | 54篇 |
2002年 | 42篇 |
2001年 | 40篇 |
2000年 | 41篇 |
1999年 | 40篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 35篇 |
1994年 | 36篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 35篇 |
1990年 | 20篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 40篇 |
1985年 | 46篇 |
1984年 | 41篇 |
1983年 | 36篇 |
1982年 | 48篇 |
1981年 | 52篇 |
1980年 | 45篇 |
1979年 | 35篇 |
1978年 | 48篇 |
1977年 | 42篇 |
1976年 | 37篇 |
1975年 | 26篇 |
1974年 | 32篇 |
1973年 | 24篇 |
1972年 | 27篇 |
1971年 | 34篇 |
1970年 | 29篇 |
1968年 | 22篇 |
1967年 | 37篇 |
排序方式: 共有2745条查询结果,搜索用时 31 毫秒
181.
Hermann Ehrlich Thomas Hanke René Born Christiane Fischer Andrej Frolov Tobias Langrock Ralf Hoffmann Uwe Schwarzenbolz Thomas Henle Paul Simon Dorin Geiger Vasily V. Bazhenov Hartmut Worch 《Journal of membrane science》2009
In the present work, we show for the first time, that N?-carboxymethyllysine is the major product of the in vitro non-enzymatic glycation reaction between fibrillar collagen and glucuronic acid. Dual diffusion membrane system was effectively used for oriented crystal growth of octacalcium phosphate/hydroxyapatite on the biomimetically carboxymethylated collagen fibrils. We hypothesize that the function of biomimetically carboxymethylated collagen is to increase the local concentration of corresponding ions in such a way that a critical nucleus of ions can be formed, leading to the formation of the mineral under specific micro-environment conditions achieved by using diffusion membrane system. 相似文献
182.
Markus Bacher Karl Baumann Hermann Knapp Andrea Steck Sigrid Teibl 《Magnetic resonance in chemistry : MRC》2009,47(1):71-83
The complete 1H and 13C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
183.
Hermann Boerner 《Mathematische Zeitschrift》1932,34(1):293-319
Ohne ZusammenfassungErster Teil der von der philosophischen Fakultät der Universität Leipzig als Inaugural-Dissertation zugelassenen Arbeit Über einige Eigenwertprobleme und ihre Anwendung in der Variationsrechnung. 相似文献
184.
A nonlinear analysis is made for a degenerate two-photon ring laser near its critical point corresponding to a self-pulsing instability by using the slaving principle and normal form theory. It turns out that the system undergoes two kinds of transitions, a usual Hopf bifurcation to a stable or unstable limit cycle and a co-dimension two Hopf bifurcation where the limit cycles disappear. An analytical criterion is given to distinguish the super-from the sub-critical bifurcation. We have also solved the equations numerically to confirm and to supplement our analytical results. In the case of super-critical bifurcation, a period-doubling bifurcation sequence to chaos is also observed with the decrease in pumping. 相似文献
185.
In this paper we give upper and lower bounds for each eigenvalue λ
n
of Hill's differential equation. We apply the results to toroidal surfaces of revolution in order to get estimates for the
eigenvalues of the Laplacian in terms of curvature expressions; they are sharp for the flat torus. As an example, we investigate
the standard torus in IR3; here, the bounds depend on the radii only. 相似文献
186.
Kurt Eger Johannes Georg Pfahl Gerd Folkers Hermann J. Roth 《Journal of heterocyclic chemistry》1987,24(2):425-430
The synthesis of the difficult to obtain pyrrolo[2,3-d]pyrimidine-2,4-diamine (4) is reported. Furthermore, some unexpected reactions on the 2-aminopyrrole-3-carbonitrile system are described 15-17. 相似文献
187.
Local models on the basis of the surface cluster approach have been applied extensively in the study of surface and adsorbate systems. The energetic details of the adsorbate-substrate interaction can be characterized in these models by the constrained space orbital variation (CSOV) method. This method allows a detailed study of adsorbate binding in different surface sites. Further, consequences of the chemisorptive interaction for adsorbate valence photoemission and vibrational properties of adsorbed molecules can be studied. 相似文献
188.
Tobias S. Hermann Thomas M. Klapötke Burkhard Krumm Jörg Stierstorfer 《无机化学与普通化学杂志》2017,643(2):149-151
Two highly energetic nitric acid esters were synthesized from the dimer of dihydroxyacetone. 1,3‐Dinitratoacetone ( 1 ) and its dimer 2,5‐bis(nitratomethyl‐2,5‐nitrato)‐1,4‐dioxane ( 2 ) were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, and elemental analysis. The thermal behavior was investigated with DTA measurements. Although showing the same atomic stoichiometry, dimer 2 shows significantly higher sensitivities measured by BAM methods (drophammer and friction tester). Due to the high oxygen content of 62.2 %, 1 and 2 were evaluated as potential high energy dense oxidizers. 相似文献
189.
Wolfgang Petz Diego M. Andrada Markus Hermann Gernot Frenking Bernhard Neumüller 《无机化学与普通化学杂志》2017,643(16):1096-1099
The formation and X‐ray structure analysis of the PtIV complex [(CH2C{PPh2C6H4}2)PtI2] is reported. The molecule possesses the orthometalated ligand (PPh3)2C→CH2, which serves via its C2 fragment as an unprecedented four‐electron σ donor. 相似文献
190.
L. Mercadier J. Hermann C. Grisolia A. Semerok 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
The plasma produced by the irradiation of a hydrogen and deuterium containing carbon fiber composite with infrared laser pulses of 4-ns pulse duration has been investigated. The experiments were carried out under argon at reduced pressure. Microscopic analyses of the irradiated sample surface were performed to measure the ablation depth. Time- and space-resolved optical emission spectroscopy was applied to characterize the evolution of spectral line emission as a function of time and distance from the surface. Particular attention was paid to the time-of-flight characteristics of the hydrogen and deuterium Balmer α spectral lines. According to the different atomic masses of both isotopes, the expansion of hydrogen into the low pressure argon atmosphere was found to be slightly faster than that of deuterium. The effect of plume segregation is pressure dependent and tends to increase the analytical signal of heavy atoms with respect to lighter ones during laser-induced breakdown spectroscopy. 相似文献