全文获取类型
收费全文 | 29062篇 |
免费 | 5599篇 |
国内免费 | 8441篇 |
专业分类
化学 | 21762篇 |
晶体学 | 944篇 |
力学 | 1989篇 |
综合类 | 1056篇 |
数学 | 3907篇 |
物理学 | 13444篇 |
出版年
2024年 | 95篇 |
2023年 | 417篇 |
2022年 | 1093篇 |
2021年 | 1135篇 |
2020年 | 1142篇 |
2019年 | 1124篇 |
2018年 | 1002篇 |
2017年 | 1388篇 |
2016年 | 1254篇 |
2015年 | 1479篇 |
2014年 | 1856篇 |
2013年 | 2325篇 |
2012年 | 2422篇 |
2011年 | 2543篇 |
2010年 | 2328篇 |
2009年 | 2314篇 |
2008年 | 2636篇 |
2007年 | 2302篇 |
2006年 | 2310篇 |
2005年 | 1979篇 |
2004年 | 1489篇 |
2003年 | 1104篇 |
2002年 | 1072篇 |
2001年 | 1121篇 |
2000年 | 1035篇 |
1999年 | 681篇 |
1998年 | 453篇 |
1997年 | 340篇 |
1996年 | 334篇 |
1995年 | 265篇 |
1994年 | 261篇 |
1993年 | 221篇 |
1992年 | 234篇 |
1991年 | 163篇 |
1990年 | 173篇 |
1989年 | 143篇 |
1988年 | 128篇 |
1987年 | 139篇 |
1986年 | 100篇 |
1985年 | 77篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 33篇 |
1979年 | 38篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1965年 | 13篇 |
1964年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
WU Jiada WU Changzheng ZHONG Xiaoxia SONG Zhoumo LI Fuming 《Chinese Journal of Lasers》1997,6(2):161-168
l.IntroductionowingtotheirpromisingproPertiesandPOtentialapplications,transitionmetalni-trideshavedrawngreatattentionandthepreparationandinvestigationofthesecom-poundshavebeenasubjectbothofscientificandoftechnologicalinterest.Transitionmetalnitridescombineadvantagesofexce1lenthardness,highmeltingPOint,goodchemi-calstabilityandhigheIectricalconductivity[11,henceoverlaySofthesecompoundshavefoundwideappIicationsinvariousfie1ds.Molybdenumnitrides,inparticular,havealsoemergedasverypromisingcandi… 相似文献
93.
研究全稳定广义生灭最小Q过程的可配称性,获得广义生灭最小Q过程是可配称的充分必要条件,以及最小Q过程是唯一的可配称Q过程的充分必要条件. 相似文献
94.
95.
Prisoner's Dilemma Game with Heterogeneous Influential Effect on Regular Small-World Networks 下载免费PDF全文
The effect of heterogeneous influence of different individuals on the maintenance of co-operative behaviour is studied in an evolutionary Prisoner's Dilemma game with players located on the sites of regular small-world networks. The players interacting with their neighbours can either co-operate or defect and update their states by choosing one of the neighbours and adopting its strategy with a probability depending on the pay off difference. The selection of the neighbour obeys a preferential rule: the more influential a neighbour, the larger the probability it is picked. It is found that this simple preferential selection rule can promote continuously the co-operation of the whole population with the strengthening of the disorder of the underlying network. 相似文献
96.
Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells 下载免费PDF全文
A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias. 相似文献
97.
Dongheng Zhang Wen-Hua Sun Junxian Hou Suyun Jie Fei Chang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):264-272
The polymerization of cyclopentadiene (CPD) was effectively initiated by methylaluminoxane (MAO) to generate poly(cyclopentadiene) (polyCPD). The effects on the polymerization of some reaction parameters such as the monomer concentration, the initiator concentration, and solvents were investigated. The conversion of CPD was monitored with gas chromatography to investigate the reaction kinetics. The polymerization rate was proportional to the concentrations of MAO in the first order and of the CPD monomer in the second order, and a reasonable cationic polymerization mechanism was suggested on the basis of the kinetic study. PolyCPD obtained at a low temperature could be dissolved in toluene or chloroform, and this indicated lower cross‐coupling during the polymerization reaction. 1H NMR and IR analysis of the polymer indicated that there were almost equal amounts of 1,2‐enchainment and 1,4‐enchainment in the polymer chain. The measurement of polyCPD showed its unique properties as a potential candidate for stable wrappings or electronic packaging materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 264–272, 2006 相似文献
98.
99.
本文对广义风险过程中的渐近方差作了非参数估计,得出并证明了两个定理,为广义风险过程中破产概率的区间估计作了理论准备. 相似文献
100.
乌骨鸡磷脂侧链脂肪酸的GC-MS分析 总被引:1,自引:1,他引:0
用氯仿:甲醇(2:1)超声提取乌骨鸡总磷脂,丙酮脱油精制后,经皂化、甲酯化处理,应用GC-MS联用技术对其侧链脂肪酸组成进行分析,并以面积归一法,计算各脂肪酸的相对百分含量.结果显示,乌骨鸡总磷脂中含有硬脂酸27.46%、花生四烯酸21.39%、油酸18.22%、亚油酸16.67%、棕榈酸12.13%、二十二碳六烯酸(DHA) 2.26%、二十碳三烯酸1.71%、棕榈油酸0.16%.不饱和脂肪酸和多不饱和脂肪酸的含量分别为60.41%和42.03%.乌骨鸡磷脂侧链脂肪酸中高比例的多不饱和脂肪酸和花生四烯酸含量是乌骨鸡磷脂的显著特征. 相似文献