全文获取类型
收费全文 | 4229篇 |
免费 | 96篇 |
国内免费 | 19篇 |
专业分类
化学 | 3269篇 |
晶体学 | 37篇 |
力学 | 52篇 |
数学 | 469篇 |
物理学 | 517篇 |
出版年
2023年 | 19篇 |
2022年 | 91篇 |
2021年 | 96篇 |
2020年 | 62篇 |
2019年 | 63篇 |
2018年 | 49篇 |
2017年 | 48篇 |
2016年 | 112篇 |
2015年 | 99篇 |
2014年 | 122篇 |
2013年 | 231篇 |
2012年 | 221篇 |
2011年 | 259篇 |
2010年 | 150篇 |
2009年 | 148篇 |
2008年 | 266篇 |
2007年 | 222篇 |
2006年 | 233篇 |
2005年 | 216篇 |
2004年 | 181篇 |
2003年 | 147篇 |
2002年 | 150篇 |
2001年 | 77篇 |
2000年 | 50篇 |
1999年 | 51篇 |
1998年 | 37篇 |
1997年 | 49篇 |
1996年 | 53篇 |
1995年 | 47篇 |
1994年 | 44篇 |
1993年 | 38篇 |
1992年 | 44篇 |
1991年 | 38篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 36篇 |
1984年 | 27篇 |
1983年 | 21篇 |
1982年 | 43篇 |
1981年 | 39篇 |
1980年 | 37篇 |
1979年 | 26篇 |
1978年 | 22篇 |
1977年 | 23篇 |
1976年 | 17篇 |
1956年 | 19篇 |
1955年 | 37篇 |
1954年 | 57篇 |
排序方式: 共有4344条查询结果,搜索用时 15 毫秒
61.
Varghese N Shetye GS Bandyopadhyay D Gobalasingham N Seo J Wang JH Theiler B Luk YY 《Langmuir : the ACS journal of surfaces and colloids》2012,28(29):10797-10807
Single-chain surfactants usually emulsify and stabilize oily substances into droplets in an aqueous solution. Here, we report a coassembly system, in which single types of anionic or non-ionic surfactants emulsify a class of water-soluble nonamphiphilic organic salts with fused aromatic rings in aqueous solutions. The nonamphiphilic organic salts are in turn promoted to form droplets of water-based liquid crystals (chromonic liquid crystals) encapsulated by single-chain surfactants. The droplets, stabilized against coalescence by encapsulated in a layer (or layers) of single chain surfactants, are of both nonspherical tactoid (elongated ellipsoid with pointy ends) and spherical shapes. The tactoids have an average long axis of ~9 μm and a short axis of ~3.5 μm with the liquid crystal aligning parallel to the droplet surface. The spherical droplets are 5-10 μm in diameter and have the liquid crystal aligning perpendicular to the droplet surface and a point defect in the center. Cationic and zwitterionic surfactants studied in this work did not promote the organic salt to form droplets. These results illustrate the complex interplay of self-association and thermodynamic incompatibility of molecules in water, which can cause new assembly behavior, including potential formation of vesicles or other assemblies, from surfactants that usually form only micelles. These unprecedented tactoidal shaped droplets also provide potential for the fabrication of new soft organic microcapsules. 相似文献
62.
Guo S Fabian O Chang YL Chen JT Lackowski WM Barbara PF 《Journal of the American Chemical Society》2011,133(31):11994-12000
A new phenomenon is presented in which electrogenerated chemiluminescence (ECL) is generated and propagates laterally as self-reinforcing waves as a result of the oxidation of a poly(9,9-dioctylfluorene-co-benzothiadiazole) thin film. In an ordered array of Au electrode posts that act as effective ECL nucleation sites, soliton-like waves were observed to expand from each site and annihilate upon collision with each other. Simulations of the ECL response supported the experimental observations that the ECL waves propagate at a constant speed. A correlated diffusion mechanism involving the correlated motion of ions, injected holes, and solvent molecules is proposed to interpret the experimental data qualitatively. A rapid increase in the diffusion coefficient of these species in the polymer results in a sharp interface between non-oxidized and oxidized polymer phases wherein the electrochemical (EC) oxidation and mass transport of all pertinent species take place. EC oxidation of conjugated polymers of this type has important implications for the understanding of these materials and their modes of operation in EC conjugated polymer devices. 相似文献
63.
Jan Urbaniak Jan M. Skowroński Barbara Olejnik 《Journal of Solid State Electrochemistry》2010,14(9):1629-1635
In the present work, a simple method of preparation of FeCl4−- graphite intercalation compounds from HCl/FeCl3 solution with the aid of chemical oxidant is presented. Based on X-ray diffraction measurements it was concluded, that stages
8, 6, and 5 FeCl4−-graphite intercalation compounds were obtained. The compounds thus obtained were thermally treated to obtain Fe2O3-exfoliated graphite composites. The dispersion of Fe2O3 in the exfoliated graphite flakes was examined with the aid of the energy dispersive X-ray analysis combined with a scanning
electron microscopy. Electrochemical behavior of electrodes was investigated in 6 M KOH solution. Electrochemical investigations
proved the formation of FeOOH on the surface of exfoliated graphite during the anodic process. Besides, electrochemical investigations
showed that the lower limit potential strongly affects the redox behavior of the Fe2O3-EG electrode. 相似文献
64.
This article presents theoretical advances in computational modeling of dissolution at mineral–water interfaces with specific
emphasis on silicates. Two different Monte Carlo methods have been developed that target equilibrium properties and kinetics
in silicate–water dissolution. The equilibrium properties are explored using the combined reactive Monte Carlo and configurational
bias Monte Carlo (RxMC-CBMC) method. The new RxMC-CBMC method is designed to affordably simulate the three-dimensional structure
of the mineral with explicit water molecules. The kinetics of the overall dissolution process is studied using a stochastic
kinetic Monte Carlo method that utilizes rate constants obtained from accurate ab initio calculations. Both these methods
provide important complementary perspective of the complex dynamics involving chemical and physical interactions at the mineral–water
interface. The results are compared to experimental and previous computational data available in the literature. 相似文献
65.
66.
Jinhua Wang Dr. Barbara Wicher Dr. Victor Maurizot Prof. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1031-1038
Quinoline based aromatic amide foldamers are known to adopt stable folded conformations. We have developed a synthetic approach to produce similar oligomers where all amide bonds, or part of them, have been replaced by an isosteric vinylene group. The results of solution and solid state structural studies show that oligomers exclusively containing vinylene linkages are not well folded, and adopt predominantly flat conformations. In contrast, a vinylene segment flanked by helical oligoamides also folds in a helix, albeit with a slightly lower curvature. The presence of vinylene functions also result in an extension of π-conjugation across the oligomer that may change charge transport properties. Altogether, these results pave the way to foldamers in which both structural control and specific electronic properties may be engineered. 相似文献
67.
Zbigniew Gregorowicz Barbara Piwowarska Franciszek Buhl und Krystyna Kania 《Fresenius' Journal of Analytical Chemistry》1968,237(5):347-351
Zusammenfassung Es wurde eine UV-spektrophotometrische Methode zur Bestimmung der 2,2-Dicinchoninsäure beschrieben. Messung erfolgt bei pH 10 bei dem Absorptionsmaximum von 260 nm. Der Bestimmungsbereich beträgt 1,71–20,52 g der 2,2-Dicinchonin-Ionen in 25 ml Lösung. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Zn2+, Hg2+ und Al3+ in 100fachem sowie Pb2+ in 10fachem Überschuß verursachen keine Störungen. Blei in 20 fachem sowie Ag+ und Hg2
2+ in einfachem Überschuß verursachen Ausscheidung von Niederschlägen.
Summary An UV-spectrophotometric method for the determination of 2,2-dicinchonic acid is described. The absorption is measured in a solution of pH 10 at the maximum of 260 nm.The range of application of the method was 1,71 to 20,52 g of DC2– ions in 25 ml of solution. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Al3+, Zn2+, Hg2+ ions present in hundredfold excess do not interfere with the determination. Ag+, Hg2 2+ ions in one-fold and Pb2+ ion in twenty-fold excess cause the deposition of a precipitate, but five-fold and ten-fold excess of Pb2+ does not interfere.相似文献
68.
Barbara Burnat Tadeusz Blaszczyk Andrzej Leniart 《Journal of Solid State Electrochemistry》2014,18(11):3111-3119
Stainless steel ISO 5832–9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and γ-globulins) on the corrosion of ISO 5832–9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol–gel method and heated at temperatures of 400 and 800 °C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L?1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 °C. The serum proteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in protein-containing solutions. 相似文献
69.
Using chiral probes shown to be sensitive to the presence of mobile phase additives, a memory effect for these additives by an amylosic column was demonstrated. Exposure to these additives gave prolonged chromatographic performance changes even after their removal from the mobile phase. This finding is consistent with strong binding of the additives to the stationary phase. A procedure to remove bound additives was developed. 相似文献
70.
We have earlier shown the possibility of preparation of crosslinked porous polymers by ionizing radiation-initiated reactions, and here we give an overview of the irradiation conditions—porous properties relationship for several methacrylate type copolymers. We illustrate the possible applications by an environment-friendly chromatographic column using water as eluent and a chemically stable scintillating polymer with excellent ion-binding capacity for possible continuous monitoring of radioactivity in natural waters. 相似文献