全文获取类型
收费全文 | 10372篇 |
免费 | 1178篇 |
国内免费 | 948篇 |
专业分类
化学 | 8157篇 |
晶体学 | 53篇 |
力学 | 1420篇 |
综合类 | 155篇 |
数学 | 537篇 |
物理学 | 2176篇 |
出版年
2024年 | 15篇 |
2023年 | 120篇 |
2022年 | 236篇 |
2021年 | 335篇 |
2020年 | 449篇 |
2019年 | 368篇 |
2018年 | 378篇 |
2017年 | 387篇 |
2016年 | 535篇 |
2015年 | 471篇 |
2014年 | 538篇 |
2013年 | 1135篇 |
2012年 | 639篇 |
2011年 | 634篇 |
2010年 | 440篇 |
2009年 | 509篇 |
2008年 | 479篇 |
2007年 | 614篇 |
2006年 | 525篇 |
2005年 | 501篇 |
2004年 | 436篇 |
2003年 | 365篇 |
2002年 | 351篇 |
2001年 | 235篇 |
2000年 | 226篇 |
1999年 | 184篇 |
1998年 | 177篇 |
1997年 | 173篇 |
1996年 | 135篇 |
1995年 | 134篇 |
1994年 | 91篇 |
1993年 | 120篇 |
1992年 | 103篇 |
1991年 | 71篇 |
1990年 | 62篇 |
1989年 | 39篇 |
1988年 | 44篇 |
1987年 | 35篇 |
1986年 | 31篇 |
1985年 | 28篇 |
1984年 | 27篇 |
1983年 | 8篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1973年 | 10篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
71.
Inside Cover: Interim Anatase Coating Layer Stabilizes Rutile@CrxOy Photoanode for Visible‐Light‐Driven Water Oxidation (ChemPhysChem 7/2015) 下载免费PDF全文
72.
Magnetic mixed hemimicelles solid‐phase extraction coupled with high‐performance liquid chromatography for the extraction and rapid determination of six fluoroquinolones in environmental water samples 下载免费PDF全文
In this study, a mixed hemimicelle solid‐phase extraction method based on Fe3O4 nanoparticles coated with sodium dodecyl sulfate was applied for the preconcentration and fast isolation of six fluoroquinolones in environmental water samples before high‐performance liquid chromatography determination. The main factors affecting the extraction efficiency of the analytes, such as amount of surfactant, amount of Fe3O4 nanoparticles, extraction time, sample volume, sample pH, ionic strength, and desorption conditions, were investigated and optimized. The method has detection limits from 0.05 to 0.1 ng/mL and good linearity (r ≥ 09948) in the range 0.1–200 ng/mL depending on the fluoroquinolone. The enrichment factor is ~200. The recoveries (at spiked levels of 1, 5, and 50 ng/mL) are in the range of 79–120%. 相似文献
73.
基于非离子表面活性剂Triton X-100,以浊点萃取结合荧光光度法测定水中的苯酚,考察影响浊点萃取的各种因素。在pH=3.0的磷酸氢二钠-磷酸二氢钾缓冲溶液中,采用2.0mL Triton X-100(5%)、82℃平衡温度、8min平衡时间的条件下,苯酚被萃取到Triton X-100表面活性剂相与水相分开,用于环境水样中苯酚的测定,结果令人满意。 相似文献
74.
75.
Dag Viktor Nilsson 《Mathematical Methods in the Applied Sciences》2017,40(4):1053-1080
We consider a two‐dimensional inviscid irrotational flow in a two layer fluid under the effects of gravity and interfacial tension. The upper fluid is bounded above by a rigid lid, and the lower fluid is bounded below by a rigid bottom. We use a spatial dynamics approach and formulate the steady Euler equations as a Hamiltonian system, where we consider the unbounded horizontal coordinate x as a time‐like coordinate. The linearization of the Hamiltonian system is studied, and bifurcation curves in the (β,α)‐plane are obtained, where α and β are two parameters. The curves depend on two additional parameters ρ and h, where ρ is the ratio of the densities and h is the ratio of the fluid depths. However, the bifurcation diagram is found to be qualitatively the same as for surface waves. In particular, we find that a Hamiltonian‐Hopf bifurcation, Hamiltonian real 1:1 resonance, and a Hamiltonian 02‐resonance occur for certain values of (β,α). Of particular interest are solitary wave solutions of the Euler equations. Such solutions correspond to homoclinic solutions of the Hamiltonian system. We investigate the parameter regimes where the Hamiltonian‐Hopf bifurcation and the Hamiltonian real 1:1 resonance occur. In both these cases, we perform a center manifold reduction of the Hamiltonian system and show that homoclinic solutions of the reduced system exist. In contrast to the case of surface waves, we find parameter values ρ and h for which the leading order nonlinear term in the reduced system vanishes. We make a detailed analysis of this phenomenon in the case of the real 1:1 resonance. We also briefly consider the Hamiltonian 02‐resonance and recover the results found by Kirrmann. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
76.
《化学:亚洲杂志》2017,12(4):387-391
Facilitating charge‐carrier separation and transfer is fundamentally important to improve the photocatalytic performance of semiconductor materials. Herein, two‐dimensional hexagonal WO3 nanoplates were synthesized by a two‐step route: rapid evaporation and solid‐phase sintering. The as‐prepared WO3 exhibits an enhanced activity of photocatalytic water oxidation compared to bulk monoclinic WO3. The electron dynamics analysis reveals that a more efficient charge‐carrier separation in the former can be obtained, the origin of which can be attributed to an increased number of surface defects in hexagonal WO3 nanoplates. This work not only presents a novel and simple method to produce two‐dimensional hexagonal WO3 nanoplates, but also demonstrates that surface defects and two‐dimensional geometric structures can promote the charge separation, which may be extended to the design of other efficient photocatalysts. 相似文献
77.
《化学:亚洲杂志》2017,12(14):1773-1779
There is increasing demand for superhydrophobic materials, which can be used for separating oil and water efficiently. To avoid secondary pollution, it is desirable to prepare such materials with green technology. Here, we present an environmentally benign method for fabricating superhydrophobic materials by using organic base based solvents in which cellulose can be dissolved and activated. The dissolved cellulose could be chemically modified with a silanization reagent, and the solvent could be recycled after CO2 was removed. The obtained cellulose nanocoating exhibited excellent hydrophobic effects. By spraying it on filter paper (water contact angle (WCA)=165°) for oil and water separation, the separation efficiency of more than 95 % was achieved; ultrasonication of an ordinary sponge in its dispersion (WCA=163°), meant it could be used as an oil absorber. It can also absorb a certain amount of bisphenol A (BPA), with the concentration decreasing by 66 % from the original concentration (0.1 mm ). Besides the high separation efficiency, it is resistant to a wide range of pH solutions, which means that it could be used in harsh environments. More importantly, the process is cost‐effective, the solvent can be recycled, and the whole process is green. Thus, the activation method provides a green route for the preparation of other cellulose‐based materials. 相似文献
78.
《化学:亚洲杂志》2017,12(8):936-946
The effective synthesis of extended conjugated N ,N ‐dialkylamino‐nor ‐dihydroxanthene‐based fluorophores is described from diversely functionalized salicylic aldehydes. The access to these original fluorescent derivatives proceeded in two steps through a one‐pot construction of the unusual nor ‐dihydroxanthene (nor ‐DHX) scaffold followed by a diversification step providing a wide variety of nor ‐DHX‐hemicyanine fused dyes emitting in the range of 730–790 nm. The versatility of our approach has enabled a further extension to the late‐stage introduction of negatively/positively charged polar groups onto their terminal nitrogen heterocyclic subunit, thereby giving access to the first water‐soluble and/or bioconjugatable members of this emerging class of NIR fluorophores. Our water‐solubilizing method is easily implementable, and the nor ‐DHX‐hemicyanine skeleton maintains satisfying fluorescence quantum yields (5–20 %) under physiological conditions. Finally, the bioconjugation ability of fluorescent derivatives bearing a free carboxylic acid was demonstrated through the covalent labeling of a model protein, namely, bovine serum albumin. 相似文献
79.
In this paper, we firstly establish the existence theorem of the global weak solutions of the Cauchy problem for the shallow water wave model of moderate amplitude, then following the idea in Xin and Zhang’s work (see Xin and Zhang, 2002), we prove the uniqueness of global weak solutions using the localization analysis in the transport equation theory. Finally, several travelling wave solutions are derived. 相似文献
80.
《Journal of separation science》2017,40(7):1434-1448
The amount of water adsorbed on polar columns plays important role in hydrophilic interaction liquid chromatography. It may strongly differ for the individual types of polar columns used in this separation mode. We measured adsorption isotherms of water on an amide and three diol‐bonded stationary phases that differ in the chemistry of the bonded ligands and properties of the silica gel support. We studied the effects of the adsorbed water on the retention of aromatic carboxylic acids, flavonoids, benzoic acid derivatives, nucleic bases, and nucleosides in aqueous‐acetonitrile mobile phases over the full composition range. The graphs of the retention factors versus the volume fraction of water in mobile phase show “U‐profile” characteristic of a dual hydrophilic interaction–reversed phase retention mechanism. The minimum on the graph that marks the changing retention mechanism depends on the amount of adsorbed water. The linear solvation energy relationship model suggests that the retention in the hydrophilic interaction liquid chromatography mode is controlled mainly by proton–donor interactions in the stationary phase, depending on the column type. Finally, the accuracy of hydrophilic interaction liquid chromatography gradient prediction improves for columns that show a high water adsorption. 相似文献