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101.
Mi Yang Li Chen Cheng‐Shou Zhao Heng‐Zhen Huang Jun‐Sheng Wang Yu‐Zhong Wang 《先进技术聚合物》2009,20(4):378-383
A novel phosphorus–nitrogen thermotropic liquid crystalline poly(ester‐imide) (PN‐TLCP) derived from p‐acetoxybenzoic acid (ABA), terephthalic acid (TPA), acetylated 2‐(6‐oxide‐6H‐dibenz<c,e><1,2>oxa phosphorin‐ 6‐yl)‐1,4‐dihydroxy phenylene (DOPO‐AHQ) and N,N'‐hexane‐1,6‐diylbis(trimellitimide) was prepared by melt transesterification. The chemical structure, the mesophase behavior, and the thermal properties of the copolymer were investigated with Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), elemental analysis, wide‐angle X‐ray diffraction (WAXD), hot‐stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PN‐TLCP exhibited a nematic mesophase with a strong birefringence at a low and broad mesomorphic temperature ranging from 220 to 350°C, an initial flow temperature as low as about 190°C and a glass transition temperature of about 160°C. PN‐TLCP has also good thermal stability, high char residues and excellent flame retardancy (limiting oxygen index, LOI = 71 and UL‐94 V‐0 rating). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
102.
Mesoporous carbon materials: synthesis and modification 总被引:1,自引:0,他引:1
Porous carbon materials are of interest in many applications because of their high surface area and physicochemical properties. Conventional syntheses can only produce randomly porous materials, with little control over the pore-size distributions, let alone mesostructures. Recent breakthroughs in the preparation of other porous materials have resulted in the development of methods for the preparation of mesoporous carbon materials with extremely high surface areas and ordered mesostructures, with potential applications as catalysts, separation media, and advanced electronic materials in many scientific disciplines. Current syntheses can be categorized as either hard-template or soft-template methods. Both are examined in this Review along with procedures for surface functionalization of the carbon materials obtained. 相似文献
103.
Weidong Shang Sheng‐Nan Su Rong Shi Ze‐Dong Mou Guo‐Qiang Yu Xia Zhang Dawen Niu 《Angewandte Chemie (International ed. in English)》2021,60(1):385-390
We here report glycosyl sulfoxides appended with an aryl iodide moiety as readily available, air and moisture stable precursors to glycosyl radicals. These glycosyl sulfoxides could be converted to glycosyl radicals by way of a rapid and efficient intramolecular radical substitution event. The use of this type of precursors enabled the synthesis of various complex C‐linked glycoconjugates under mild conditions. This reaction could be performed in aqueous media and is amenable to the synthesis of glycopeptidomimetics and carbohydrate‐DNA conjugates. 相似文献
104.
BasedonthefirstideaspresentedbyBeck',anewmethodcalledalternatingpulsecurrent-chronopotentiometricstrippinganalysis(APC-CPSA)hasbeendeveloped.Inthistechnique,duringthestrippingstepthecurrentimposedontheelectrol,ysi$cellcomprisesofanalternatingpulsecurrent(APC)andtheinherentdirectcurrentofCPSA.TheAPCisoperatedwithahighfrequencyinasquarewavemode.isandiRisdefinedastheanodicandcathodicpulsecurrent,respectively,isandtRisthetimeforwhichthesecurrentsflow.So,whenisandiRalternates,partsofthestri… 相似文献
105.
Zhang S Lukoyanova O Echegoyen L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(10):2846-2853
Two C(60) hexakis-adducts (2 and 3) were synthesized by using a protection-deprotection strategy. The symmetric fullerene tetrakis-adduct 8 was obtained by anthracene removal from the hexakis-adduct 7. Reaction of 8 with terpyridylglycine or pyridylglycine afforded two hexakis-adducts, 2 and 3. By using the retro-cyclopropanation reaction, the four malonate addends located on the equatorial belt of the hexakis-adducts were removed to afford two trans-1 bis-adducts, 4 and 5, with terpyridyl- or pyridylpyrrolidine groups. The structures of 2 and 3 were confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and (1)H, (13)C, and COSY NMR, and UV-visible spectroscopy. The cyclic voltammograms of fullerene multiadducts 2, 3, and 9 show irreversible reductions. Self-assembled monolayers (SAMs) of 1 and 3 were formed on gold surfaces through nitrogen adsorption. SAMs of 3 represent the first example of a fullerene hexakis-adduct formed on gold surfaces through nitrogen adsorption. Controlled potential electrolyses (CPE) were conducted to prepare trans-1 bis-adducts 4 and 5 modified with terpyridyl and pyridyl groups. 相似文献
106.
提出了一种把矩阵分解应用于雷达目标的逆合成孔径雷达成像(ISAR)三维重构的方法。通过对目标运动场景建模,将目标的ISAR成像过程化,推导出图像序列中散射点二维位置坐标与原目标三维坐标的投影矩阵关系,利用正交投影下的矩阵分解基本方法,从观测矩阵中分解出原目标散射点的三维位置矩阵,进而实现目标的三维位置重构,仿真结果验证了该方法的有效性。 相似文献
107.
Five solid complexes of zinc with L‐α‐methionine, L‐α‐phenylalanine and L‐α‐histidine were prepared. The constant‐volume combustion energies of the complexes, ΔEc (coordination), were determined by a precise rotating bomb calorimeter at 298.15 K. They were ‐ 2969.03 ± 0.34, ‐2929.46 ± 1.59, ‐9597.13 ± 6.12, ‐4378.98 ± 3.27 and ‐14047 ± 6.75 kJ/mol, respectively. Their standard enthalpies of combustion, ΔHθm,c(coordination, s, 298.15 K), and standard enthalpies of formation, ΔHθm,f (coordination, s, 298.15 K), were calculated. They were ‐2959.73 ± 0.34, ‐2923.88 ± 1.59, ‐9649.18 ± 6.12, ‐4373.40 ± 3.27, ‐14048.53 ± 6.75 kj/mol and ‐1180.94 ± 0.92, ‐1401.26 ± 1.77, ‐2501.69 ± 6.50, ‐1381.47 ± 3.49, ‐1950.19 ± 7.65 kJ/mol, respectively. 相似文献
108.
Xiao‐Nan Jiang Chang‐Liang Sun Chang‐Sheng Wang 《Journal of computational chemistry》2010,31(7):1410-1420
A scheme is proposed in this article to predict the cooperativity in hydrogen bond chains of formamides, acetamides, and N‐methylformamides. The parameters needed in the scheme are derived from fitting to the hydrogen bonding energies of MP2/6‐31+G** with basis set superposition error (BSSE) correction of the hydrogen bond chains of formamides containing from two to eight monomeric units. The scheme is then used to calculate the individual hydrogen bonding energies in the chains of formamides containing 9 and 12 monomeric units, in the chains of acetamides containing from two to seven monomeric units, in the chains of N‐methylformamides containing from two to seven monomeric units. The calculation results show that the cooperativity predicted by the scheme proposed in this paper is in good agreement with those obtained from MP2/6‐31+G** calculations by including the BSSE correction, demonstrating that the scheme proposed in this article is reasonable. Based on our scheme, a cooperativity effect of almost 240% of the dimer hydrogen bonding energy in long hydrogen bond formamide chains, a cooperativity effect of almost 190% of the dimer hydrogen bonding energy in long hydrogen bond acetamide chains, and a cooperativity effect of almost 210% of the dimer hydrogen bonding energy in long hydrogen bond N‐methylformamide chains are predicted. The scheme is further applied to some heterogeneous chains containing formamide, acetamide, and N‐methylformamide. The individual hydrogen bonding energies in these heterogeneous chains predicted by our scheme are also in good agreement with those obtained from Møller‐Plesset calculations including BSSE correction. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
109.
110.
Dynamics of ice nucleation on water repellent surfaces 总被引:3,自引:0,他引:3
Alizadeh A Yamada M Li R Shang W Otta S Zhong S Ge L Dhinojwala A Conway KR Bahadur V Vinciquerra AJ Stephens B Blohm ML 《Langmuir : the ACS journal of surfaces and colloids》2012,28(6):3180-3186
Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications. 相似文献