全文获取类型
收费全文 | 5776篇 |
免费 | 1024篇 |
国内免费 | 578篇 |
专业分类
化学 | 3742篇 |
晶体学 | 53篇 |
力学 | 255篇 |
综合类 | 30篇 |
数学 | 743篇 |
物理学 | 2555篇 |
出版年
2024年 | 23篇 |
2023年 | 130篇 |
2022年 | 200篇 |
2021年 | 224篇 |
2020年 | 228篇 |
2019年 | 196篇 |
2018年 | 182篇 |
2017年 | 177篇 |
2016年 | 288篇 |
2015年 | 253篇 |
2014年 | 316篇 |
2013年 | 389篇 |
2012年 | 485篇 |
2011年 | 552篇 |
2010年 | 333篇 |
2009年 | 332篇 |
2008年 | 359篇 |
2007年 | 330篇 |
2006年 | 317篇 |
2005年 | 262篇 |
2004年 | 195篇 |
2003年 | 173篇 |
2002年 | 197篇 |
2001年 | 152篇 |
2000年 | 126篇 |
1999年 | 155篇 |
1998年 | 129篇 |
1997年 | 108篇 |
1996年 | 105篇 |
1995年 | 73篇 |
1994年 | 54篇 |
1993年 | 52篇 |
1992年 | 49篇 |
1991年 | 59篇 |
1990年 | 32篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有7378条查询结果,搜索用时 15 毫秒
51.
Lin Hou Yujie Yuan Junxiao Ren Yinling Zhang Yongchao Wang Xiaoning Shan Qi Liu Zhenzhong Zhang 《Journal of nanoparticle research》2017,19(8):286
In this work, carbon nanomaterials, single-walled carbon nanotubes (SWNT), graphene oxide (GO), and fullerene (C60) were modified by hyaluronic acid (HA) to obtain water-soluble and biocompatible nanomaterials with high tumor-targeting capacity and then the comparative study of these hyaluronic acid-modified carbon nanomaterials was made in vitro and in vivo. The conjugates of hyaluronic acid and carbon nanomaterials, namely, HA-SWNT, HA-GO, HA-C60, were confirmed by UV/Vis spectrum, Fourier transform infrared spectroscopy (FTIR), and a transmission electron microscope (TEM). After HA modification, the sizes of HA-SWNT, HA-GO, and HA-C60 were in a range of 70 to 300 nm, and all the three HA-modified materials were at negative potential, demonstrating that HA modification was in favor of extravasation of carbon materials into a tumor site due to enhanced permeability and retention effect of tumor. Photothermal conversion in vitro test demonstrated excellent photothermal sensitivity of HA-SWNT and HA-GO. But the reactive oxygen yield of HA-C60 was the highest compared with the others under visible light irradiation, which proved the good photodynamic therapy effect of HA-C60. In addition, cytotoxicity experiments exhibited that the inhibitory efficacy of HA-SWNT was the lowest, the second was HA-C60, and the highest was HA-GO, which was consistent with the uptake degree of them. While under the laser irradiation, the cell inhibition of the HA-SWNT was the highest, the second was HA-GO, and the last was HA-C60. In vivo evaluation of the three targeting carbon nanomaterials was consistent with the cytotoxicity assay results. Taken together, the results demonstrated that HA-SWNT and HA-GO were suited for photothermal therapy (PTT) agents for their good photothermal property, while HA-C60 was used as a kind of photodynamic therapy (PDT) agent for its photodynamic effect. 相似文献
52.
A high-power 880-nm diode-directly-pumped passively mode-locked 1342 nm Nd:YVO? laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The laser mode radii in the laser crystal and on the SESAM were optimized carefully using the ABCD matrix formalism. An average output power of 2.3 W was obtained with a repetition rate of 76 MHz and a pulse width of 29.2 ps under an absorbed pump power of 12.1 W, corresponding to an optical-optical efficiency of 19.0% and a slope efficiency of 23.9%, respectively. 相似文献
53.
LD side-pumped 41 W high beam quality acousto-optical Q-switched single-rod Nd:YAG laser 总被引:2,自引:0,他引:2
We report a LD side-pumped high beam quality (M
x
2 = 1.20 and M
y
2 = 1.19) acousto-optic (AO) Q-switched single-rod Nd:YAG laser with a TEM00-mode dynamic stable cavity. At the pump power of 600 W, 41 W TEM00-mode 1064 nm laser was achieved with electro-optical conversion efficiency of 7%. The repetition rate and pulse width were
30 kHz and 102 ns, respectively with pulse energy of 1.4 mJ and peak power of 13 kW. Up to 24 W of 532 nm green laser was
generated by external frequency doubling, corresponding to 59% optical conversion efficiency. 相似文献
54.
Chaotic oscillations associated with the breakup of polarization entangled coherent states in a microchip solid-state laser 总被引:1,自引:0,他引:1
We demonstrate the breakup of spatial-polarization entangled lasing patterns, which possess vector phase singularities, and the resultant dynamic instabilities featuring chaotic oscillations. The frequency splitting between a pair of Ince-Gauss (IG) lasing modes, originally forming a coherent entanglement state, and a self-excited additional nonorthogonal IG mode through a new class of transverse effect of self-injection pattern seeding, is shown to result in modal-interference-induced modulation at the beat frequency, leading to chaotic oscillations. 相似文献
55.
X. Cai X. M. Chen Z. Y. Liu Z. Y. Shen H. P. Liu X. W. Ma M. D. Hou 《Zeitschrift für Physik A Hadrons and Nuclei》1976,355(4):439-442
The double and single ionization cross section ratios of helium by partially stripped carbon, oxygen and fluorine ions are measured for projectile charge states ranging from +1 to +4 and impact energies from 1.5 MeV to 7.5 MeV. The effective charge effect in partially stripped ion-helium collisions is studied. It is found that the effective charge qeff increases as the impinging energy increases and q eff shows a modest dependence upon the projectile charge state in the present energy range. The projectile charge state, projectile energy, projectile and target electronic state dependences of the effective charge effect may be explained using orbital interpenetrating. 相似文献
56.
57.
58.
59.
本文根据量子力学的线性叠加原理,构造了由多模(即q模时目平态的相反态|{{-Zj}〉q及多模虚相干态|{{-Zj}〉q这两者的线性叠加所组成的一种新型的多模Schrodinger猫态光场利用新近建立的多模压缩态理论,研究了态的N次方Y压缩效应,结果发现:①当压缩阶数N=Zp且p=2m(m=1,2,3,…,…)时,态。总是恒处于N-Y最小测不准态;②当压缩阶数N=2p且p=2m+1(m=0,1,2,3,…,…)时,如果各模的初始相位,态间的初始相位差以及各单模相干态光场的平均光子数之总和等满足一定的量子化条件,则态可呈现出周期性变化的、任意阶的N次方Y压缩效应;③当压缩阶数N=2P'+1时,无论p'=2m(m=0,1,2,…,…)还是p'=2m+1(m=0,1,2,3,…,……),只要各模的初始相位满足一定的量子条件,则当两态叠加几率幅满足时,态就恒处于N-Y测不准态,始终不呈现N-Y最小测不准态和N次方Y压缩;而当时,态始终不呈现N-Y测不准态、N-Y最小测不准态和N次方Y压缩效应. 相似文献
60.