全文获取类型
收费全文 | 18508篇 |
免费 | 3210篇 |
国内免费 | 2924篇 |
专业分类
化学 | 13381篇 |
晶体学 | 311篇 |
力学 | 1077篇 |
综合类 | 391篇 |
数学 | 2048篇 |
物理学 | 7434篇 |
出版年
2024年 | 68篇 |
2023年 | 349篇 |
2022年 | 686篇 |
2021年 | 698篇 |
2020年 | 681篇 |
2019年 | 751篇 |
2018年 | 608篇 |
2017年 | 663篇 |
2016年 | 805篇 |
2015年 | 869篇 |
2014年 | 1108篇 |
2013年 | 1452篇 |
2012年 | 1655篇 |
2011年 | 1795篇 |
2010年 | 1280篇 |
2009年 | 1270篇 |
2008年 | 1324篇 |
2007年 | 1248篇 |
2006年 | 1052篇 |
2005年 | 915篇 |
2004年 | 763篇 |
2003年 | 579篇 |
2002年 | 573篇 |
2001年 | 514篇 |
2000年 | 491篇 |
1999年 | 360篇 |
1998年 | 255篇 |
1997年 | 210篇 |
1996年 | 224篇 |
1995年 | 174篇 |
1994年 | 186篇 |
1993年 | 157篇 |
1992年 | 143篇 |
1991年 | 121篇 |
1990年 | 105篇 |
1989年 | 99篇 |
1988年 | 63篇 |
1987年 | 62篇 |
1986年 | 51篇 |
1985年 | 57篇 |
1984年 | 38篇 |
1983年 | 23篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 21篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Stability, internal modes and internal oscillation of 12-pearled necklace solitons in photorefractive crystal with imprinted Bessel photonic lattices are investigated. It is shown that the imaginary parts of internal modes are negligible comparing with real parts. The stable solitons perform long-distance and quasi-periodic oscillation of intensity and shape under the perturbation of internal modes. 相似文献
83.
Wafer-Level Testable High-Speed Silicon Microring Modulator Integrated with Grating Couplers 下载免费PDF全文
A wafer-level testable silicon-on-insulator-based microring modulator is demonstrated with high modulation speed, to which the grating couplers are integrated as the fiber-to-chip interfaces. Cost-efflcient fabrications are realized with the help of optical structure and etching depth designs. Grating couplers and waveguides are patterned and etched together with the same slab thickness. Finally we obtain a 3-dB coupling bandwidth of about 6Ohm and 10 Gb/s nonreturn-to-zero modulation by wafer-level optical and electrical measurements. 相似文献
84.
85.
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
86.
Xia Ren Jiaying Xiong Lingzhi Liang Yin Chen Guisen Zhang 《Molecules (Basel, Switzerland)》2022,27(9)
Here, we explored the possible interaction between duloxetine and SEP-363856 (SEP-856) in depression-related reactions. The results showed that oral administration of duloxetine showed powerful antidepressant-like effects in both the forced swimming test (FST) and the suspension tail test (TST). SEP-856 orally administered alone also exerted an antidepressant-like effect in FST and TST, especially at doses of 0.3, 1, and 10 mg/kg. In addition, duloxetine (15 mg/kg) and SEP-856 (15 mg/kg) both showed antidepressant-like effects in the sucrose preference test (SPT). Most importantly, in the above experiments, compared with duloxetine alone, the simultaneous use of duloxetine and SEP-856 caused a more significant antidepressant-like effect. It is worth noting that doses of drug combination in FST and TST did not change the motor activities of mice in the open-field test (OFT). Thus, duloxetine and SEP-856 seem to play a synergistic role in regulating depression-related behaviors and might be beneficial for refractory depression. 相似文献
87.
88.
Structural stability in terms of the decomposition temperature in LiMn2O4 was systematically investigated by a series of high-temperature and high-pressure experiments.LiMn2O4 was found to have structural stability up to 5 GPa at room temperature.Under ambient pressure,the compound decomposed at 1300℃.The decomposition temperature decreased with increasing pressure,yielding more complex decomposed products.Below the decomposition temperature,the crystal structure of LiMn2O4 varied with pressure.The presented results in this study offer new insights into the thermal and pressure stability of LiMn2O4 materials as a cathode for lithium-ion batteries that can operate under extreme conditions.Therefore,these findings may serve as a useful guide for future work for improving lithium-ion batteries. 相似文献
89.
在密度泛函理论的B3PW91水平上, 优化计算了AlmNin (m+n=2–4)团簇的几何结构、团簇基态的结合能、最高占据轨道与最低空轨道之间的能级间隙和可能的分离能. 结果表明, 随着团簇尺寸的增加, 能级间隙呈现奇偶振荡规律; Al2Ni2团簇具有最高的结合能, 易分离成Ni原子和Al2Ni团簇; 含Al的合金团簇最易先分离出一个Al原子, 而含Ni的合金团簇没有这种趋势. 相似文献
90.
Highly charged ions (HCIs) have huge potential energy due to their high charge state. When a HCI reaches a solid surface, its potential energy is released immediately on the surface to cause a nano-scale defect. Thus, HCIs are expected to be useful for solid-surface modifications on the nano-scale. We investigate the defects on a highly oriented pyrolytic graphite (HOPG) surface induced by slow highly charged Ar^q+ ions with impact energy of 20-2000qeV with scanning probe microscopy (SPM). In order to clarify the role of kinetic and potential energies in surface modification, the nano-defects are characterized in lateral size and height corresponding to the kinetic energy and charge state of the HCIs. Both the potential energy and kinetic energy of the ions may influence the size of nano-defect. Since potential energy increases dramatically with increasing charge state, the potential energy effect is expected to be much larger than the kinetic energy effect in the case of extremely high charge states. This implies that pure surface modification on the nano-scale could be carried out by slow highly charged ions. The mean size of nano-defect region could also be controlled by selecting the charge state and kinetic energy of HCI. 相似文献