全文获取类型
收费全文 | 29443篇 |
免费 | 6101篇 |
国内免费 | 11315篇 |
专业分类
化学 | 21773篇 |
晶体学 | 1188篇 |
力学 | 2329篇 |
综合类 | 1492篇 |
数学 | 4987篇 |
物理学 | 15090篇 |
出版年
2024年 | 73篇 |
2023年 | 279篇 |
2022年 | 981篇 |
2021年 | 1019篇 |
2020年 | 998篇 |
2019年 | 930篇 |
2018年 | 892篇 |
2017年 | 1338篇 |
2016年 | 965篇 |
2015年 | 1429篇 |
2014年 | 1720篇 |
2013年 | 2313篇 |
2012年 | 2151篇 |
2011年 | 2516篇 |
2010年 | 2466篇 |
2009年 | 2787篇 |
2008年 | 2926篇 |
2007年 | 2671篇 |
2006年 | 2757篇 |
2005年 | 2402篇 |
2004年 | 1919篇 |
2003年 | 1356篇 |
2002年 | 1354篇 |
2001年 | 1553篇 |
2000年 | 1670篇 |
1999年 | 964篇 |
1998年 | 472篇 |
1997年 | 396篇 |
1996年 | 359篇 |
1995年 | 303篇 |
1994年 | 330篇 |
1993年 | 343篇 |
1992年 | 280篇 |
1991年 | 220篇 |
1990年 | 231篇 |
1989年 | 242篇 |
1988年 | 196篇 |
1987年 | 161篇 |
1986年 | 147篇 |
1985年 | 94篇 |
1984年 | 115篇 |
1983年 | 108篇 |
1982年 | 74篇 |
1981年 | 83篇 |
1980年 | 64篇 |
1979年 | 48篇 |
1978年 | 30篇 |
1977年 | 14篇 |
1965年 | 21篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
102.
Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems. 相似文献
103.
Reduction of Dislocations in GaN Epilayer Grown on Si (111) Substrates using a GaN Intermedial Layer 下载免费PDF全文
GaN intermedial layers grown under different pressures are inserted between GaN epilayers and AIN/Si(111) substrates. In situ optical reflectivity measurements show that a transition from the three-dimensional (3D) mode to the 2I) one occurs during the GaN epilayer growth when a higher growth pressure is used during the preceding GaN intermedial layer growth, and an improvement of the crystalline quality of GaN epilayer will be made. Combining the in situ reflectivity and transmission electron microscopy (TEM) measurements, it is suggested that the lateral growth at the transition of growth mode is favourable for bending of dislocation lines, thus reducing the density of threading dislocations in the epilayer. 相似文献
104.
Chaos Synchronization Criterion and Its Optimizations for a Nonlinear Transducer System via Linear State Error Feedback Control 下载免费PDF全文
Global chaos synchronization of two identical nonlinear transducer systems is investigated via linear state error feedback control. The sufficient criterion for global chaos synchronization is derived firstly by the Gerschgorin disc theorem and the stability theory of linear time-varied systems. Then this sufficient criterion is further optimized in the sense of reducing the lower bounds of the coupling coefficients with two methods, one based on Gerschgorin disc theorem itself and the other based on Lyapunov direct method. Finally, two optimized criteria are compared theoretically. 相似文献
105.
以可溶性聚酰亚胺为反应底物,经氯甲基化反应制得氯甲基化聚酰亚胺,再以氯甲基为活性反应中心,在聚酰亚胺侧链上接枝聚丙二醇单丁醚(PPG),从而得到PPG侧链修饰聚酰亚胺.所制备的产物结构经红外光谱和核磁共振氢谱得以证实.介电常数及吸附脱附测试结果表明:经过大体积侧链PPG修饰后,聚合物的介电常数明显降低,由3.147降低至2.976;比体积和比表面积增大.同时,所制得的聚合物具有优良的溶解性能,在微电子工业中易于加工应用. 相似文献
106.
A novel power generator has been achieved to convert vibration to electrical energy via the piezoelectric effect. The generator obtained by micro fabrication process mainly consists of silicon based frame and composite cantilever. The prototype tested at resonant vibration generates 1.15μW of effective power to a 20.4-kΩ resistance load. The potential of this work is to offer miniaturization solutions for power generators, and with the proposed method the ambient ubiquitous vibration can be harvested effectively as endless energy source to form an integrated self-powering system. 相似文献
107.
ZHANG Liangmin SHAO Zongshu ZHANG Jingwen MU Xiaodong CHEN Huanchu JIANG Minhua 《Chinese Journal of Lasers》1996,5(3):235-241
Mutually Pumped Phase Conjugation of Three Incoherent Beams with a Novel Photorefractive CrystalMutuallyPumpedPhaseConjugatio... 相似文献
108.
109.
The dynamic viscoelastic response of the two-phase polymer blend systems shows the characteristics of the thermorheologically complex materials. In this paper theoretical equations for describing the dynamic viscoelastic response of such polymer blend systems have been established by means of the mechanical modeling technique. The dynamic viscoelastic response of the blend systems at any blend composition can be predicted theoretically by using the equations established, provided that the dynamic viscoelastic response of the two pure components and the mechanical model parameters are known in advance. Thus, we provide an effective method for studying the dynamic mechanical properties and the molecular relaxation characteristics of the two-phase polymer blend systems. 相似文献
110.
树脂吸附法处理水杨酸甲酯生产废水的研究 总被引:7,自引:0,他引:7
采用吸附树脂NDA—99处理水杨酸甲酯生产废水,结果表明该树脂时废水中的5磺基水杨酸及水杨酸均具有良好的吸附—脱附性能.废水经预处理和吸附处理后,CODCr由57000-59000mg/L降至6300mg/L左右,去除率接近89%.用IBV8%NaOH 3BVH2O作脱附剂,在温度为60℃、流量为IBV/h的条件下,脱附率接近100%,树脂可重复使用.高浓度脱附液经酸化、浓缩、冷却结晶,可回收5—磺基水杨酸,回收率为95%左右。纯度为78%。 相似文献