全文获取类型
收费全文 | 14890篇 |
免费 | 1973篇 |
国内免费 | 1642篇 |
专业分类
化学 | 8685篇 |
晶体学 | 339篇 |
力学 | 1270篇 |
综合类 | 139篇 |
数学 | 3164篇 |
物理学 | 4908篇 |
出版年
2024年 | 31篇 |
2023年 | 134篇 |
2022年 | 345篇 |
2021年 | 376篇 |
2020年 | 444篇 |
2019年 | 427篇 |
2018年 | 429篇 |
2017年 | 493篇 |
2016年 | 590篇 |
2015年 | 469篇 |
2014年 | 678篇 |
2013年 | 1393篇 |
2012年 | 753篇 |
2011年 | 794篇 |
2010年 | 629篇 |
2009年 | 815篇 |
2008年 | 911篇 |
2007年 | 949篇 |
2006年 | 900篇 |
2005年 | 796篇 |
2004年 | 763篇 |
2003年 | 668篇 |
2002年 | 680篇 |
2001年 | 551篇 |
2000年 | 556篇 |
1999年 | 453篇 |
1998年 | 378篇 |
1997年 | 344篇 |
1996年 | 299篇 |
1995年 | 283篇 |
1994年 | 248篇 |
1993年 | 217篇 |
1992年 | 176篇 |
1991年 | 88篇 |
1990年 | 73篇 |
1989年 | 50篇 |
1988年 | 62篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 35篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 3篇 |
1976年 | 12篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
B. Kowalczyk 《Journal of Thermal Analysis and Calorimetry》2000,60(1):163-166
The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The
salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC
methods up to 1200°C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and
carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values
of the transition enthalpy were determinated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
262.
In the degassing process of transformer oil with ultrasonic waves ,decompostition of the oil was observed.Light hydrocarbons,including methane,ethane,ethylene ,aceylene,propane etc,were found to be released continuously from the oil into headspace within a closed vial placed in an ultrasonic field ,The gases came from decomposition of hydrocarbon molecules under cavitation effect. 相似文献
263.
A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper. The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed. It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath although the activation energy values are similar. 相似文献
264.
L. Stachowicz S. K. Singh E. Wender S. L. Girshick 《Plasma Chemistry and Plasma Processing》1993,13(3):447-461
Heat-treated rice hulls have been used as precursor material for synthesis of ultrafne SiC in a RF plasma reactor. Rice hulls containing finely distributed silica and active carbon act as a source for SiC formation. The plasma-synthesized powder contained ultrafnc -SiC with excess carbon and some unreacted silica. Post-treatment processes such as oxidation and acid (HF) treatment appear to be effective in removing the excess carbon and silica. 相似文献
265.
Effects of metal surfaces, such as aluminium, silver and gold, on the melting behavior and thermal polymerization of long-chain diynoic acids having a diacetylene group at different positions were investigated by thermal analyses using DSC, TG and other methods. The surface effects of metals were significant in the order of Ag, Al and Au. These effects are attributable to the anchoring of carboxyl group on the surface by chemisorption, which leads to unfavorable condition for polymerization of heptadeca-2,4-diynoic acid. In the case of tricosa-10,12-diynoic acid, containing a flexible methylene chain, inserted between COOH and C≡C?C≡C groups, the anchoring of COOH on the metal surface causes rather favorable effect on the polymerization. 相似文献
266.
Tae Oan Ahn Jung Ho Kim Jong Chan Lee Han Mo Jeong Jong-Yoon Park 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):435-441
A macro-azoinitiator containing polyarylate segment and azo group was prepared by the solution polycondensation of azobiscyanopentanoyl chloride and hydroxy-terminated polyarylates having viscosity-average molecular weights of 6200, 8100, and 12 400. These macro-azoinitiators were used in the radical polymerization of styrene to synthesize polyarylate-polystyrene block copolymers. Thermal properties measured by the differential scanning calorimetry indicated the phase separated morphology of the block copolymers except at low molecular weight of the block constituents. © 1993 John Wiley & Sons, Inc. 相似文献
267.
过渡金属-碱土金属铜镁异双核配合物的合成、晶体结构和性质研究 总被引:2,自引:0,他引:2
The transition metal and alkaline earth metal heterobinuclear complex[CuMg(TS)(H2O)·H2O],where TS is the schiff base N,N′-bis(3-carboxylsalidene)trimethylenediamine, was synthesised and its crystal structure was determined by the single-crystal X-ray diffraction method at room temperature. It crystallizes in the monoclinic system, space group P21/n. The lattice parameters are a=12.041(2)?, b=14.736(3)?, c=12.062(2)?, β=118.00(3)°, Z=4 with R1=0.0364. The thermal property and EPR studies of the complex according to crystal structure are also investigated. CCDC: 182408. 相似文献
268.
The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a
coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH3COO)2·2H2O is a two-stage process with Cd(CH3COO)2·H2O as intermediate. The way of Cd(CH3COO)2 decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO2 are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions
in which intermediates, Cd and CdCO3, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending
on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with
oxygen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
269.
液晶电视由于其优异的显示性能将会越来越受到青睐。本文简要综述了近年来电视用液晶材料的研究进展,归纳总结了这些液晶材料的合成方法及其热性能、介电各向异性、双折射率、粘度等特性。 相似文献
270.