全文获取类型
收费全文 | 14666篇 |
免费 | 2169篇 |
国内免费 | 2875篇 |
专业分类
化学 | 12309篇 |
晶体学 | 259篇 |
力学 | 560篇 |
综合类 | 210篇 |
数学 | 1407篇 |
物理学 | 4965篇 |
出版年
2024年 | 45篇 |
2023年 | 243篇 |
2022年 | 485篇 |
2021年 | 542篇 |
2020年 | 568篇 |
2019年 | 599篇 |
2018年 | 486篇 |
2017年 | 519篇 |
2016年 | 677篇 |
2015年 | 760篇 |
2014年 | 934篇 |
2013年 | 1239篇 |
2012年 | 1321篇 |
2011年 | 1405篇 |
2010年 | 1081篇 |
2009年 | 982篇 |
2008年 | 1134篇 |
2007年 | 1045篇 |
2006年 | 913篇 |
2005年 | 744篇 |
2004年 | 627篇 |
2003年 | 512篇 |
2002年 | 489篇 |
2001年 | 436篇 |
2000年 | 345篇 |
1999年 | 285篇 |
1998年 | 209篇 |
1997年 | 154篇 |
1996年 | 148篇 |
1995年 | 127篇 |
1994年 | 119篇 |
1993年 | 93篇 |
1992年 | 71篇 |
1991年 | 66篇 |
1990年 | 69篇 |
1989年 | 33篇 |
1988年 | 39篇 |
1987年 | 22篇 |
1986年 | 28篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
非线性光纤方向耦合器孤子动力特性分析 总被引:2,自引:0,他引:2
利用变分方法,导出了双曲正割型光孤子在非线性光纤耦合器中传输时满足的动力学方程组,分析了该方程组的平衡点性态,讨论了光孤子的开关特性.指出参数|β|<2π.是能实现完全的开关操作的必要条件. 相似文献
2.
3.
This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described. 相似文献
4.
基于Lee等人的离子温度梯度模导致的反常热能输运系数,本文研究了辅助加热托卡马克等离子体的能量约束行为,并对自举电流的效应作了初步考虑。结果表明,计算得到的能量约束时间随等离子体电流I_p和托卡马克大半径R增大而增长,随注入功率P_t、环向场B_t以及等离子体小半径α的增大而缩短。这些结果与Kaye-Goldston的经验约束定标具有相同的趋势。自举电流的存在总是导致能量约束时间的增加,当自举电流与总电流的比值γ较小时,能量约束时间的增加率约为γ/2。此外,自举电流将造成锯齿反转半径的减小。 相似文献
5.
Xiao‐Hui Liu Yan‐Guo Li Ying Lin Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1272-1281
The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. 1H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007 相似文献
6.
物理实验课程考核、评估体系初探 总被引:4,自引:0,他引:4
对物理实验课程考核、评估方法进行了探讨,提出了物理实验课程考核、评估体系及实施细则.重点介绍了体系中的核心部分——正规的物理实验课程考试. 相似文献
7.
西咪替丁的应用进展 总被引:2,自引:0,他引:2
劳英 《宁波大学学报(理工版)》2002,15(2):89-92
综述了近年来国内外报道的H2受体抗拮剂-西咪替丁应用于除治疗消化性溃疡以外的其他疾病的进展情况,以其为临床用药提供参考。 相似文献
8.
9.
In this article, the linear and nonlinear shear rheological behaviors of polylactide (PLA)/clay (organophilic‐montmorillonite) nanocomposites (PLACNs) were investigated by an Advanced Rheology Expanded System rheometer. The nanocomposites were prepared by master batch method using a twin‐screw extruder with poly(ε‐caprolactone) (PCL) as a compatibilizer. The presence of org‐MMT leads to obvious pseudo‐solid‐like behaviors of nanocomposite melts. The behaviors caused by the formation of a “percolating network” derived from the reciprocity among the strong related sheet particles. Therefore, the storage moduli, loss moduli, and dynamic viscosities of PLACNs show a monotonic increase with MMT content. Nonterminal behaviors exists in PLACNs nanocomposites. Besides the PLACNs melts show a greater shear thinning tendency than pure PLA melt because of the preferential orientation of the MMT layers. Therefore, PLACNs have higher moduli but better processibility compared with pure PLA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3189–3196, 2007 相似文献
10.
Ying‐Ling Liu Chuan‐Shao Wu Yie‐Shun Chiu Wen‐Hsuan Ho 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2354-2367
A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003 相似文献