全文获取类型
收费全文 | 425344篇 |
免费 | 2035篇 |
国内免费 | 755篇 |
专业分类
化学 | 174580篇 |
晶体学 | 5842篇 |
力学 | 27474篇 |
综合类 | 3篇 |
数学 | 88616篇 |
物理学 | 131619篇 |
出版年
2021年 | 3193篇 |
2020年 | 3496篇 |
2019年 | 4307篇 |
2018年 | 19846篇 |
2017年 | 20032篇 |
2016年 | 15388篇 |
2015年 | 4778篇 |
2014年 | 7345篇 |
2013年 | 12792篇 |
2012年 | 16048篇 |
2011年 | 28139篇 |
2010年 | 19004篇 |
2009年 | 19650篇 |
2008年 | 23668篇 |
2007年 | 27493篇 |
2006年 | 10544篇 |
2005年 | 13574篇 |
2004年 | 11620篇 |
2003年 | 11874篇 |
2002年 | 10100篇 |
2001年 | 8031篇 |
2000年 | 6641篇 |
1999年 | 4739篇 |
1998年 | 4512篇 |
1997年 | 4307篇 |
1996年 | 4099篇 |
1995年 | 3534篇 |
1994年 | 3543篇 |
1993年 | 3576篇 |
1992年 | 3521篇 |
1991年 | 3938篇 |
1990年 | 3911篇 |
1989年 | 3939篇 |
1988年 | 3696篇 |
1987年 | 3770篇 |
1986年 | 3458篇 |
1985年 | 3996篇 |
1984年 | 4236篇 |
1983年 | 3639篇 |
1982年 | 3833篇 |
1981年 | 3509篇 |
1980年 | 3273篇 |
1979年 | 3770篇 |
1978年 | 3845篇 |
1977年 | 3918篇 |
1976年 | 4015篇 |
1975年 | 3743篇 |
1974年 | 3584篇 |
1973年 | 3801篇 |
1972年 | 3237篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Bou-Huot Phe Véronique Bounor-Legare Laurent David Alain Michel 《Journal of Sol-Gel Science and Technology》2004,31(1-3):47-50
We study the synthesis of organic-inorganic hybrids in the molten state of the polymer without solvent, by reactive processing. The synthesis is based in a first step upon the crosslinking of ethylene vinyl acetate copolymer (EVA) through an exchange reaction between the pendant ester groups of EVA and tetrapropoxysilane (TPOS) in presence of dibutyltin oxide (DBTO) as an indispensable catalyst. Then in a second step the hydrolysis-condensation reactions of residual alkoxide groups results in silica network formation, which is covalently bonded with the organic network. An original approach was developed to correlate the evolution of the hydrolysis-condensation reactions through the assessment of propanol by gas chromatography and the evolution of the morphology through SAXS and TEM analysis. Silica-rich domains with a diameter close to 5 nm are obtained. 相似文献
992.
993.
Atomic force microscopy (AFM) has been used to visualize the plastic deformation mechanisms that are responsible for the yielding of semicrystalline polymers of low degree of crystallinity (<50%). Indeed, AFM, if operated in suitable conditions, is able to image both the amorphous and the crystalline phases. Polyamide 6 films have been drawn at temperatures T < 160 °C. Postmortem AFM observations show that, at yield, shear bands nucleate and propagate in the amorphous phase. They cross the crystalline lamellae and run over the whole surface of the sample. By crossing the lamellae, they form nanoblocks of uniform size. Neither the size of the nanoblocks nor the angle between the tensile axis and the shear bands can be explained in terms of crystal plasticity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 687–701, 2004 相似文献
994.
V.B. Fainerman V.N. Kazakov S.V. Lylyk A.V. Makievski R. Miller 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):97-102
One of the essential differences in the design of bubble pressure tensiometers consists in the geometry of the measuring capillaries. To reach extremely short adsorption times of milliseconds and below, the so-called deadtime of the capillaries must be of the order of some 10 ms. In particular, for concentrated surfactant solutions, such as micellar solutions, short deadtimes are needed to minimize the initial surfactant load of the generated bubbles. A theoretical model is derived and confirmed by experiments performed for a wide range of experimental conditions, mainly in respect to variations in deadtime and bubble volume. 相似文献
995.
EQCM and voltammetric data show that thallium(I) ions, which are adsorbed in the region of the positive surface charge, most probably, in the form of the ionic pairs, are not reduced. In this potential region, thallium(I) ions are reduced directly from the solution. At more negative potentials, the previously adsorbed stable ionic pairs slowly undergo transition into the less stable form. From this form, thallium(I) ions can be reduced or desorbed into the solution. The process is best described by a model of one electron, i.e., full charge transfer. 相似文献
996.
Andreev V. N. Kolyadko E. A. Podlovchenko B. I. 《Russian Journal of Electrochemistry》2004,40(5):580-583
Radioactive tracer studies confirm the earlier electrochemical results that carbon monoxide can virtually completely displace iodine adatoms. For the first time, it is found that iodine adatoms are not displaced by carbon monoxide when iodide anions are adsorbed in the presence of an upd silver monolayer. The possible reasons for the effect observed are discussed. 相似文献
997.
Two-Layered Poly-o-phenylenediamine/Polyaniline Composite: Electrosynthesis and Spectroelectrochemical Properties 总被引:1,自引:0,他引:1
E. Yu. Pisarevskaya E. V. Ovsyannikova N. M. Alpatova 《Russian Journal of Electrochemistry》2004,40(9):969-976
Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface. 相似文献
998.
Data on the adsorption of kryptates of alkali metals on a mercury electrode are obtained for the first time by a method of the measurement of the differential capacitance as a function of potential and are compared to one another. Shown is that there takes place a deep mutual relationship between the structure of a complex and the regularities of its adsorption. An assumption is put forth about the possibility of adsorption of a free ligand in solutions of lithium kryptate, which possesses relatively low strength. The co-adsorption of sodium kryptate with 1-adamantanol, which forms a two-dimensional condensed layer, is investigated. Established is that the C vs. E curves, obtained in 1 M Na2SO4 at a constant activity of 1-adamantanol and a varying concentration of KryptofixR 222, exhibit two distinctly pronounced portions, each of which corresponds to predominant adsorption of one of the surface-active components. The region of predominant adsorption of KryptofixR 222 expands with its concentration. 相似文献
999.
The dynamic and equilibrium surface tensions of aqueous dodecylamidoethyldimethylbenzylammonium chloride solutions of various concentrations at 16, 20, 25, 30, and 35°C are studied for the first time. The effects of the concentration and temperature on the surface tension relaxation are discussed. The possibility of two-dimensional phase transition and its effect on the dynamic behavior of surface tension are considered. 相似文献
1000.
M. A. Proskurnin N. V. Orlova A. V. Pikhtar' N. V. Osipova 《Journal of Analytical Chemistry》2004,59(5):433-437
Conditions are determined for the determination of salicylhydroxamic and acetylhydroxamic acids by thermal-lens spectrometry using iron(III) in an aqueous medium. The detection limits are 6 × 10–8 and 3 × 10–8 M, respectively. The sensitivity can be enhanced 3–6 times with the use of aqueous–organic media. 相似文献