全文获取类型
收费全文 | 17331篇 |
免费 | 3272篇 |
国内免费 | 2465篇 |
专业分类
化学 | 12575篇 |
晶体学 | 256篇 |
力学 | 1089篇 |
综合类 | 153篇 |
数学 | 1847篇 |
物理学 | 7148篇 |
出版年
2024年 | 42篇 |
2023年 | 331篇 |
2022年 | 435篇 |
2021年 | 667篇 |
2020年 | 754篇 |
2019年 | 684篇 |
2018年 | 667篇 |
2017年 | 595篇 |
2016年 | 907篇 |
2015年 | 885篇 |
2014年 | 1144篇 |
2013年 | 1432篇 |
2012年 | 1608篇 |
2011年 | 1667篇 |
2010年 | 1233篇 |
2009年 | 1171篇 |
2008年 | 1280篇 |
2007年 | 1143篇 |
2006年 | 1044篇 |
2005年 | 832篇 |
2004年 | 642篇 |
2003年 | 497篇 |
2002年 | 460篇 |
2001年 | 419篇 |
2000年 | 360篇 |
1999年 | 345篇 |
1998年 | 253篇 |
1997年 | 241篇 |
1996年 | 258篇 |
1995年 | 195篇 |
1994年 | 152篇 |
1993年 | 130篇 |
1992年 | 121篇 |
1991年 | 79篇 |
1990年 | 94篇 |
1989年 | 66篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 46篇 |
1985年 | 49篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1957年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
2.
Wang Rong Li Xu Zhou Youshi Cao Shuxuan Xu Honghao Han Wenjuan Zhang Yuxia Liu Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The... 相似文献
3.
Geometriae Dedicata - Inspired by a recent work of Grove and Petersen (Alexandrov spaces with maximal radius, 2018), where the authors studied positively curved Alexandrov spaces with largest... 相似文献
4.
Jiraya Kiriratnikom Xun Zhang Xiaohan Cao Bo Chu Chengjian Zhang Xinghong Zhang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2262-2268
Facile construction of sulfur-rich polymers using readily available raw chemicals is an area aggressively pursued but challenging. Herein we use common feedstocks of ethylene oxide (EO), propylene oxide (PO), and carbonyl sulfide (COS) to synthesize copoly(thioether)s which are traditionally produced from unpleasant and difficult to store episulfides. In this protocol, the EO/COS coupling selectively generates a pure poly(ethylene sulfide) (PES) with melting temperature (Tm) values up to 172°C and high yields up to 98%. The EO/PO/COS terpolymerization leads to the incorporation of soft poly(propylene sulfide) (PPS) and hard PES segments together, affording a random PES-co-PPS copoly(thioether) with the complete consumption of EO and PO. Additionally, by simply varying the EO/PO feeding ratio, the obtained copoly(thioether)s possess tunable thermal properties, Tm values in the range of 76–144°C, and excellent solubility. These copolymerizations are conducted in one-pot/one-step at industrially favored reaction temperatures of 100–120°C using catalysts of common organic bases, suggesting a facile and practical manner. Especially, the copoly(thioether) exhibits high refractive indices up to 1.68 owing to its high sulfur content, suggesting a broad application prospect in optical materials. 相似文献
5.
针对圆柱形膨胀腔消声器三维建模及声学性能分析问题, 提出一种基于切比雪夫变分原理的耦合声场建模方法, 建立三维圆柱形膨胀腔消声器理论模型并搭建试验台架, 传递损失试验结果验证了理论模型的准确性. 将膨胀腔消声器内部声场分解为多个子声场, 基于子声场间压力与质点振速连续性条件, 推导声场耦合变分公式, 构建子声场拉格朗日泛函. 将子声场声压函数展开为切比雪夫-傅里叶级数形式, 通过瑞利-里兹法求解膨胀腔消声器频率、声压响应及传递损失. 计算并对比分析扩张比、扩张腔长度、进出口管偏置对膨胀腔消声器消声性能的影响. 结果表明: 扩张比增大会有效提高消声器在低频段的消声性能, 进出口管的偏置对消声器消声性能影响很小. 相似文献
6.
Jiang Rui-Yang Xin Jia-Wei Cao Cong 《International Journal of Theoretical Physics》2021,60(8):2836-2855
International Journal of Theoretical Physics - Quantum logic gates are the foundation of circuit-based quantum computation and quantum simulation. Multi-qubit quantum controlled gates are of vital... 相似文献
7.
Journal of Visualization - The increasing availability of spatiotemporal data provides unprecedented opportunities for understanding the structure of an urban area in terms of people’s... 相似文献
8.
International Journal of Theoretical Physics - We consider the stationary state of a spin-orbit coupled (SOC) binary Bose-Einstein condensates with dipole-dipole interaction (DDI). Our results are... 相似文献
9.
Nonlinear Dynamics - This paper investigates the guaranteed cost positive consensus for linear multi-agent systems (MASs) with multiple time-varying delays and switching topologies. First,... 相似文献
10.
Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect 下载免费PDF全文
A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems. 相似文献