全文获取类型
收费全文 | 4673篇 |
免费 | 271篇 |
国内免费 | 971篇 |
专业分类
化学 | 5277篇 |
晶体学 | 111篇 |
力学 | 43篇 |
综合类 | 52篇 |
数学 | 7篇 |
物理学 | 425篇 |
出版年
2023年 | 23篇 |
2022年 | 58篇 |
2021年 | 85篇 |
2020年 | 104篇 |
2019年 | 91篇 |
2018年 | 121篇 |
2017年 | 137篇 |
2016年 | 147篇 |
2015年 | 131篇 |
2014年 | 191篇 |
2013年 | 557篇 |
2012年 | 242篇 |
2011年 | 264篇 |
2010年 | 200篇 |
2009年 | 261篇 |
2008年 | 276篇 |
2007年 | 324篇 |
2006年 | 306篇 |
2005年 | 302篇 |
2004年 | 285篇 |
2003年 | 251篇 |
2002年 | 201篇 |
2001年 | 145篇 |
2000年 | 139篇 |
1999年 | 124篇 |
1998年 | 93篇 |
1997年 | 93篇 |
1996年 | 107篇 |
1995年 | 105篇 |
1994年 | 101篇 |
1993年 | 87篇 |
1992年 | 78篇 |
1991年 | 41篇 |
1990年 | 28篇 |
1989年 | 30篇 |
1988年 | 33篇 |
1987年 | 14篇 |
1986年 | 28篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有5915条查询结果,搜索用时 15 毫秒
21.
Aït Hmaïdouch L. Mançour Billah S. El Hadek M. 《Journal of Thermal Analysis and Calorimetry》2002,69(2):659-667
The solid—liquid equilibria of the ternary system H2O—Al(NO3)3—Mg(NO3)2 were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO3)3·9H2O, Mg(NO3)2·9H2O and Mg(NO3)2·6H2O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
22.
在异源四倍体棉种中现已鉴定出22个芽黄突变体、26个芽黄基因,其中V1与V7、V2之间存在着部分同源关系。重叠牙黄基因V16V17的遗传主式独特,单体1测验的分离世代F2和BC恢复产生了黄化的单体株。鉴于杂中子生产现状,俄系统阐述了以芽黄作为指示性进行棉花杂种优势利用的可行性。 相似文献
23.
HU Qiao-Sheng HU Chang-MingLaboratory of Organofluorine Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai China 《中国化学》1997,15(3):286-288
Initiated by CrCl3/Fe redox couple, per(poly)fluoroalkyl iodides added to methyl a-acetylamino acrylate, giving B-per(poly)fluoroalkyl a-amino acid derivatives in good yields. 相似文献
24.
25.
Maryam Mirza-Aghayan Rabah Boukherroub Mahshid Rahimifard 《Journal of organometallic chemistry》2007,692(23):5113-5116
The palladium(II) chloride/triethylsilane system has been successfully applied for the selective hydrogenation of the carbon-carbon double bond of α,β-unsaturated ketones to yield the corresponding saturated carbonyl compounds. The reaction takes place under mild conditions and affords high yields. 相似文献
26.
刘建飞 《南昌大学学报(理科版)》2007,31(6):566-569
研究了不同的表面改性剂对超细氢氧化镁的表面改性.并分别以水和乙醇为溶剂,研究了表面改性后氢氧化镁的分散行为.实验结果表明,以水为溶剂的体系,六偏磷酸钠分散性能最好,而以乙醇为溶剂,硅烷偶联剂KH-550分散性能最好,其用量为基体量的5%左右,可使制备的超细氢氧化镁粒径达到0.2 μm尺度以下.试验结果对进一步认识超细氢氧化镁的性质及其应用具有重要意义. 相似文献
27.
The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates. 相似文献
28.
Maksimov R. D. Zicans J. Ivanova T. Negreeva S. N. Plume E. 《Mechanics of Composite Materials》2002,38(2):141-148
The results of experimental and theoretical investigations of elastic and thermophysical properties of poly(vinyl chloride) (PVC) and chlorinated polyethylene (CPE) blends are presented. Eight types of specimens with different ratios of weight contents of PVC and CPE (PVC/CPE = 100/0, 90/10, 80/20, 60/40, 40/60, 20/80, 10/90, and 0/100) were tested. The effect of blend composition on the elastic constants (tensile and shear modulus) is discussed. The data on the thermal conductivity, thermal diffusivity, and heat capacity of the blends investigated are also presented. 相似文献
29.
Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation 总被引:2,自引:0,他引:2
The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's(1) equations as well as the Chen and Evans(2) model were used to correlate the new data. Results are reported and compared to literature data and correlations. 相似文献
30.
Z. D. Zivkovic 《Journal of Thermal Analysis and Calorimetry》1994,41(1):99-104
The results of comparative thermal analysis (TG-DTG-DTA-DSC) of the thermal decomposition of hexamminecobalt(III) chloride in air atmosphere are reported. The kinetics and mechanism of the thermal decomposition, the process enthalpy and the variation in specific thermal capacity of the solid product reaction with temperature were determined. 相似文献