全文获取类型
收费全文 | 19566篇 |
免费 | 3179篇 |
国内免费 | 3787篇 |
专业分类
化学 | 16135篇 |
晶体学 | 353篇 |
力学 | 1038篇 |
综合类 | 271篇 |
数学 | 1983篇 |
物理学 | 6752篇 |
出版年
2024年 | 75篇 |
2023年 | 393篇 |
2022年 | 718篇 |
2021年 | 775篇 |
2020年 | 883篇 |
2019年 | 925篇 |
2018年 | 820篇 |
2017年 | 766篇 |
2016年 | 971篇 |
2015年 | 1031篇 |
2014年 | 1280篇 |
2013年 | 1517篇 |
2012年 | 1665篇 |
2011年 | 1691篇 |
2010年 | 1400篇 |
2009年 | 1298篇 |
2008年 | 1346篇 |
2007年 | 1111篇 |
2006年 | 1113篇 |
2005年 | 1027篇 |
2004年 | 923篇 |
2003年 | 750篇 |
2002年 | 854篇 |
2001年 | 748篇 |
2000年 | 545篇 |
1999年 | 420篇 |
1998年 | 259篇 |
1997年 | 165篇 |
1996年 | 199篇 |
1995年 | 152篇 |
1994年 | 132篇 |
1993年 | 125篇 |
1992年 | 91篇 |
1991年 | 98篇 |
1990年 | 66篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 28篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1959年 | 3篇 |
1957年 | 2篇 |
1936年 | 4篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Xin Liang Li Li Yan Dong Wei Dong Hongxia Cui Chunhui Xia Tao Xu Chaozhong Wang Jie Zhang Tingting Liu Huimin Sui Chao Gao 《Molecules (Basel, Switzerland)》2022,27(9)
Estrogens added illegally to dietary supplements are hazardous to human health. Traditional detection and analysis methods have many limitations, and we have developed an assay that combines thin-layer chromatography with Raman imaging microscopy (TLC-RIM). The five estrogens (estrone, estradiol, estriol, ethinyl estradiol, and diethylstilbestrol) were initially separated by TLC, then detected by area scanning Raman imaging with a 532 nm laser under a microscope. Raman spectra were obtained for each estrogen, which were used for detecting estrogen illegally added to botanical dietary supplements. The LOD of each estrogen was 0.4, 1.0, 0.8, 0.2, and 0.2 mg/mL, respectively. The matrix in the real sample did not interfere with the detection of estrogens. The method was fast, sensitive, stable, specific, and reliable. 相似文献
52.
Motivated by recent theoretical and experimental advances in quantum simulations using alkaline earth(AE)atoms,we put forward a proposal to detect the Kondo physics in a cold atomic system.It has been demonstrated that the intrinsic spin-exchange interaction in AE atoms can be significantly enhanced near a confinement-induced resonance(CIR),which facilitates the simulation of Kondo physics.Since the Kondo effect appears only for antiferromagnetic coupling,we find that the conductivity of such system exhibits an asymmetry across a resonance of spin-exchange interaction.The asymmetric conductivity can serve as the smoking gun evidence for Kondo physics in the cold atom context.When an extra magnetic field ramps up,the spin-exchange process near Fermi surface is suppressed by Zee-man energy and the conductivity becomes more and more symmetric.Our results can be verified in the current experimental setup. 相似文献
53.
探索了L波段的高功率线极化径向线阵列天线。基于三角形栅格形式实现了径向线圆形平面阵列天线,分析并给出了径向线并联馈电网络,并以同轴馈电的水平单圆环线极化天线为基础,利用径向线并联馈电网络设计出了间距小于一个波长下L波段高功率线极化径向线阵列天线。研究结果表明:这种结构实现径向线阵列天线的线极化辐射是可行的,该天线在中心频率1.57 GHz下,增益为19.97 dBi,轴比为-52.06 dB,反射系数为0.105 2;在1.37~1.77 GHz的频率范围内增益大于18.64 dBi,轴向轴比值小于-46.45 dB。 相似文献
54.
Xudong Li Renpeng Yan Xin Yu Deying Chen Jing Gao 《Journal of Russian Laser Research》2013,34(6):586-592
We improve the performance of an acousto-optical Q-switched Nd:YAG 946 nm laser using a convex–plane cavity. We obtain the highest output average power of 2.3 W with a pulse width of 15.3 ns in a 10 kHz 946 nm laser with a convex–plane cavity. The maximum peak power 15.0 kW is about three times higher than that in a plane–plane cavity. Also we investigate the output performances of the pulsed 946 nm laser with the convex–plane cavity at 20 and 50 kHz. 相似文献
55.
实验研究了大模面积光子晶体光纤飞秒激光器在近零色散点展宽脉冲锁模的束缚态运转.获得了双脉冲束缚态锁模,以及脉冲间隔不相等的多脉冲束缚态锁模,实验发现束缚态的子脉冲间距具有随机性.通过建立光纤锁模激光器的数值模型,分析了激光器束缚态锁模建立的动力学过程,在一定抽运强度下,激光器存在多个稳态,或者单脉冲运转,或者子脉冲间隔不相等的束缚态运转,这取决于锁模建立阶段半导体可饱和吸收镜(SESAM)对噪声信号的随机提取.并提出了抑制束缚态的方法,模拟得出此项技术可直接获得的最大单脉冲能量为19.6 nJ,考虑到40%左右的压缩损耗,可得到压缩至76 fs的最短脉冲,单脉冲能量为11.8 nJ.数值模拟结果能很好的与实验相符合. 相似文献
56.
Shengkai Li Zhaotian Zhu Xinqi Cai Minghui Song Shen Wang Qing Hao Long Chen Zhuo Chen 《中国化学》2021,(6):1491-1497
Main observation and conclusion
Surface-enhanced Raman spectroscopy(SERS)-based bioanalytical technique involves the interaction of SERS-active substrate with c... 相似文献
57.
Main observation and conclusion
With the rapid development of the wearable electronics,the flexible supercapacitor with high energy density has attracted more a... 相似文献
58.
59.
A reliable method for direct synthesis of β‐dichlorosubstituted acetanilides is reported. The key transformation involves the oxidative and catalytic cleavage of a carbon‐carbon bond in the presence of iodine trichloride (ICl3). In this protocol ICl3 is used not only as the catalyst but also as the oxidant which widely broadens the scope of its application in organic synthetic chemistry. 相似文献
60.
Yanpei Luo Xin Zhou Jiangwei Zhang Yu Qi Zheng Li Fuxiang Zhang Can Li 《Journal of Energy Chemistry》2021,(12):385-390
The hybridization between the outmost s orbitals of metal (Bi3+,Sn2+,Pb2+,Ag+) and O 2p orbitals has been widely employed to develop innovative semiconductors w... 相似文献