全文获取类型
收费全文 | 7893篇 |
免费 | 1271篇 |
国内免费 | 1218篇 |
专业分类
化学 | 5961篇 |
晶体学 | 163篇 |
力学 | 398篇 |
综合类 | 94篇 |
数学 | 964篇 |
物理学 | 2802篇 |
出版年
2024年 | 14篇 |
2023年 | 94篇 |
2022年 | 191篇 |
2021年 | 239篇 |
2020年 | 324篇 |
2019年 | 335篇 |
2018年 | 272篇 |
2017年 | 251篇 |
2016年 | 355篇 |
2015年 | 409篇 |
2014年 | 459篇 |
2013年 | 640篇 |
2012年 | 683篇 |
2011年 | 710篇 |
2010年 | 503篇 |
2009年 | 507篇 |
2008年 | 564篇 |
2007年 | 547篇 |
2006年 | 461篇 |
2005年 | 427篇 |
2004年 | 339篇 |
2003年 | 277篇 |
2002年 | 281篇 |
2001年 | 247篇 |
2000年 | 174篇 |
1999年 | 192篇 |
1998年 | 142篇 |
1997年 | 119篇 |
1996年 | 120篇 |
1995年 | 82篇 |
1994年 | 83篇 |
1993年 | 71篇 |
1992年 | 48篇 |
1991年 | 38篇 |
1990年 | 28篇 |
1989年 | 33篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 23篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1909年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jiménez-Millán E Giner-Casares JJ Muñoz E Martín-Romero MT Camacho L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):14888-14899
The surface active derivative of the organic dye Acridine Orange (N-10-dodecyl-acridine orange (DAO)) has been included in mixed Langmuir monolayers with stearic acid (SA). The maximum relative content on DAO for a stable mixed monolayer is a molar ratio of X(DAO) = 0.5. Brewster angle microscopy (BAM) reveals a high homogeneity at the micrometer level for the mixed monolayer in equimolar proportion (X(DAO) = 0.5), whereas the appearance of domains occurs for lower content of DAO, i.e., X(DAO) = 0.2 and 0.1. The aggregation of the DAO headgroup leads to well-defined H-aggregates at the air/water interface for those mixed monolayers with a low content of DAO. However, for the mixed monolayers enriched in DAO, e.g., X(DAO) = 0.5, the molecular crowding prevents the formation of defined supramolecular structures. Molecular organization and tilting of the DAO headgroup is quantitatively analyzed by in situ UV-visible reflection spectroscopy. The formation of H-aggregates of the DAO headgroup can be reversibly tuned with the applied surface pressure. A molecular mechanism for the conformational rearrangement of the DAO molecule is proposed using RM1 quantum semiempirical calculations. 相似文献
992.
Wei ZhangYu Zhao Xueyuan BaiGe Hui John R. LombardiDaqing Zhao Bing Zhao 《Vibrational Spectroscopy》2011,55(1):65-68
We report on the joint application of fluorescence, ultraviolet-visible (UV-Vis) and Raman spectroscopy to the study of berberine with human serum albumin (HSA). We propose the surface-enhanced Raman scattering (SERS) technique to improve the understanding of the quenching interaction caused by berberine which could be applied in recognition process of fluorescent drugs with large biomolecules. The fluorescence and UV-Vis spectroscopic results show that the fluorescence intensity of HSA is significantly decreased in the presence of berberine, and the quenching mechanism is static. The SERS technique demonstrates clear advantages over direct measurements in physiological conditions. By means of this method, we are able to deduce important information concerning the binding property of berberine when interacting with HSA. We show the nitrogen atom is free but the dioxolane is involved in the spontaneously electrostatic inducement and subsequently hydrophobic binding. 相似文献
993.
The temperature-responsive ionic-crosslinked polymeric nanocapsules (TRICNs) were fabricated via the 'self-templating' approach from the poly(tert-butyl acrylate-co-N-isopropylacrylamide-co-acrylic acid) (poly(tBA-co-NIPAm-co-AA)) terpolymer nanoparticles prepared via the emulsifier-free emulsion polymerization. After the surface carboxyl groups of the terpolymer nanoparticles were crosslinked with calcium ions, the TRICNs were achieved after the cores of the shell-crosslinked nanoparticles had been etched by being dissolved with acetone. Transmission electron microscope (TEM) showed the particle size of the individual nanocapsules was about 200 nm with the inner diameter of about 140 nm. The lower critical solution temperature (LCST) of the TRICNs was found to be about 31°C from the dynamic light scattering (DLS) analysis. Furthermore, the nanocapsules could disintegrate in acidic media while they were stable in the neutral or alkaline media. 相似文献
994.
Novel stimuli-responsive multilayer chitosan hollow microspheres with chitosan as the unique component have been fabricated by the sequential layer-by-layer electrostatic assembly technique from the sacrificial templates (polystyrene sulfonate, PSS) with chitosan (CS) as the polycation and carboxymethyl chitosan (CMCS) as the polyanion, respectively. Their hollow structure was confirmed by the TEM analysis. The DLS analysis indicated that the multilayer chitosan microcapsules were pH and ionic strength dual-responsive. Due to the biocompatibility of the single component chitosan used, the multilayer chitosan microcapsules are expected to be used in the controlled release of drugs. 相似文献
995.
Weiwei Tang Jingjing Liang Wenqing Jiang Bing Wu Dr. Yong Zhang Prof. Dr. Dingxian Jia 《无机化学与普通化学杂志》2011,637(11):1539-1544
The lanthanide selenidogermanates [{Eu(en)3}2(μ‐OH)2]Ge2Se6 ( 1 ), [{Ho(en)3}2(μ‐OH)2]Ge2Se6 ( 2 ), and [{Ho(dien)2}2(μ‐OH)2]Ge2Se6 ( 3 ) (en = ethylenediamine, dien = diethylenetriamine) were solvothermally prepared by the reactions of Eu2O3 (or Ho2O3), germanium, and selenium in en and dien solvents respectively. Compounds 1 – 3 are composed of selenidogermanate [Ge2Se6]4– anion and dinuclear lanthanide complex cation [{Ln(en)3}2(μ‐OH)2]4+ (Ln = Eu, Ho) or [{Ho(dien)2}2(μ‐OH)2]4+. The [Ge2Se6]4– anion is composed of two GeSe4 tetrahedra sharing a common edge. The dinuclear lanthanide complex cations are built up from two [Ln(en)3]3+ or [Ho(dien)2]3+ ions joined by two μ‐OH bridges. All lanthanide(III) ions are in eight‐coordinate environments forming distorted bicapped trigonal prisms. In 1 – 3 , three‐dimensional supramolecular networks of the anions and cations are formed by N–H ··· Se and N–H ··· O hydrogen bonds. To the best of our knowledge, 1 – 3 are the first examples of selenidogermanate salts with lanthanide complex counter cations. 相似文献
996.
Qi Yu Ping Chen Yu Gao Dong Liu Jujie Mu 《Surface and interface analysis : SIA》2011,43(13):1610-1615
The aim of this article was to investigate the effects of electron irradiation in ultrahigh vacuum environment on the surface properties of high‐performance carbon/bismaleimide (BMI) composites used in aerospace. The changes in surface chemical composition with increasing irradiation fluence were studied by XPS. The evolution of surface morphology and surface roughness were observed by atomic force microscopy (AFM). The mass loss behavior occurring in the surface layer of the composites was examined. The results indicated that the electron irradiation in high vacuum caused rupture of chemical bonds and cross‐linking process in the surface layer, thereby leading to the mass loss behavior and the formation of carbonification layer in the surface of the carbon/BMI composites. The changes in the surface chemical composition were determined by a competing effect existing between the rupture of chemical bonds and the cross‐linking process at lower irradiation fluence, and by a degradation process only at higher fluence of electron irradiation. The surface morphology was altered and the surface roughness was increased significantly after electron irradiation. The mass loss ratio first increased obviously at lower fluences, and then reached a plateau value of 0.45% beyond 5 × 1015 cm?2 fluence of electron irradiation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
997.
炭化处理高烧失量硅藻土及对天然橡胶的性能补强 总被引:2,自引:0,他引:2
通过缺氧条件下煅烧富含有机质的内蒙硅藻土制备了一种含炭的硅藻土,并将这种炭化硅藻土代替部分炭黑用于天然橡胶的补强.采用红外光谱、X射线衍射、热分析、扫描电子显微镜、能谱和万能材料试验机对炭化硅藻土进行结构表征和力学性能测试.结果表明,于600℃进行2h的缺氧锻烧处理后,硅藻土中的有机质已经转化为无定形碳紧密吸附于硅藻土... 相似文献
998.
Yuling Cui Bing Zhang Bingqian Liu Huafeng Chen Guonan Chen Dianping Tang 《Mikrochimica acta》2011,174(1-2):137-144
We report on a new electrochemical biosensing strategy for the sensitive detection of hydrogen peroxide (H2O2) in foodstuff samples. It is based on a gold electrode modified with layer of graphene patterned with a multilayer made from an organic?Cinorganic hybrid nanomaterial. Initially, a layer of thionine (Th) was assembled on the surface of the graphene nanosheets, and these were then cast on the surface of the electrode for the alternate assembly of gold nanoparticles and horseradish peroxidase. The large surface-to-volume ratio and high conductivity of the nanosheets provides a benign microenvironment for the construction of the biosensor. The use of such a multilayer not only shortens the electron transfer pathway of the active center of the enzyme due to the presence of gold nanoparticles, but also enhances the electrocatalytic efficiency of the biosensor toward the reduction of H2O2. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The number of layers, the operating potential, and the pH of the supporting electrolyte were optimized. Linear response is obtained for the range from 0.5???M to 1.8?mM of H2O2, the detection limit is 10 nM (at S/N?=?3), and 95% of the steady-state current is reached within 2?s. The method was applied to sense H2O2 in spiked sterilized milk and correlated excellently with the permanganate titration method.
A new electrochemical biosensing strategy for sensitive detection of hydrogen peroxide in foodstuff was developed by using a gold electrode modified with a layer of graphene nanosheets patterned with a multilayer made from an organic?Cinorganic hybrid nanomaterial. 相似文献
999.
An aryl dicarboxylic acid amide compound TMB-5 is an efficientβ-form nucleating agent for isotactic polypropylene(iPP).Because of the solubility of TMB-5,superstructure and morphology of iPP crystals changed with melting conditions.Effects of final heating temperature(T_f)on heterogeneous nucleation of iPP/TMB-5 were investigated.It was discovered that the crystallization temperature increased with decreasing T_f value.The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt,the remaining(non-dissolved)TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt,which promoted crystallization.Complete solubility of nucleating agent caused the decreasing efficiency.TMB-5 recrystallized in the form of tiny needles,whose aggregates induced dendritic iPP crystals. 相似文献
1000.