全文获取类型
收费全文 | 15587篇 |
免费 | 2900篇 |
国内免费 | 1582篇 |
专业分类
化学 | 10740篇 |
晶体学 | 127篇 |
力学 | 1130篇 |
综合类 | 109篇 |
数学 | 2030篇 |
物理学 | 5933篇 |
出版年
2024年 | 34篇 |
2023年 | 311篇 |
2022年 | 463篇 |
2021年 | 543篇 |
2020年 | 661篇 |
2019年 | 556篇 |
2018年 | 507篇 |
2017年 | 493篇 |
2016年 | 749篇 |
2015年 | 751篇 |
2014年 | 823篇 |
2013年 | 1108篇 |
2012年 | 1359篇 |
2011年 | 1507篇 |
2010年 | 992篇 |
2009年 | 928篇 |
2008年 | 1052篇 |
2007年 | 890篇 |
2006年 | 909篇 |
2005年 | 657篇 |
2004年 | 568篇 |
2003年 | 414篇 |
2002年 | 419篇 |
2001年 | 317篇 |
2000年 | 322篇 |
1999年 | 336篇 |
1998年 | 308篇 |
1997年 | 308篇 |
1996年 | 286篇 |
1995年 | 248篇 |
1994年 | 216篇 |
1993年 | 209篇 |
1992年 | 157篇 |
1991年 | 127篇 |
1990年 | 130篇 |
1989年 | 92篇 |
1988年 | 76篇 |
1987年 | 64篇 |
1986年 | 45篇 |
1985年 | 45篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1957年 | 2篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
81.
Jiqin Deng 《Journal of Mathematical Analysis and Applications》2007,332(1):475-486
In this paper, by using the fixed point theory, under quite general conditions on the nonlinear term, we obtain an existence result of bounded positive solutions of Schrödinger equations in two-dimensional exterior domains. 相似文献
82.
现代免疫分析技术研究进展 总被引:1,自引:0,他引:1
本文着重分析了各种标记免疫分析方法的发展状况,指出更多的非同位素标记物的使用,自动化分析等将是免疫分析法的未来发展趋势。 相似文献
83.
Chongyu Mei Junqiao Ding Bing Yao Yanxiang Cheng Zhiyuan Xie Yanhou Geng Lixiang Wang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1746-1757
Two orange phosphorescent iridium complex monomers, 9‐hexyl‐9‐(iridium (III)bis(2‐(4′‐fluorophenyl)‐4‐phenylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐PIr) and 9‐hexyl‐9‐(iridium(III)bis(2‐(4′‐fluorophenyl)‐4‐methylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐MIr), were successfully synthesized. The Suzuki polycondensation of 2,7‐bis(trimethylene boronate)‐9,9‐dioctylfluorene with 2,7‐dibromo‐9,9‐dioctylfluorene and Br‐PIr or Br‐MIr afforded two series of copolymers, PIrPFs and MIrPFs, in good yields, in which the concentrations of the phosphorescent moieties were kept small (0.5–3 mol % feed ratio) to realize incomplete energy transfer. The photoluminescence (PL) of the copolymers showed blue‐ and orange‐emission peaks. A white‐light‐emitting diode with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/PIr05PF (0.5 mol % feed ratio of Br‐PIr)/Ca/Al exhibited a luminous efficiency of 4.49 cd/A and a power efficiency of 2.35 lm/W at 6.0 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.46, 0.33). The CIE coordinates were improved to (0.34, 0.33) when copolymer MIr10PF (1.0 mol % feed ratio of Br‐MIr) was employed as the white‐emissive layer. The strong orange emission in the electroluminescence spectra in comparison with PL for these kinds of polymers was attributed to the additional contribution of charge trapping in the phosphorescent dopants. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 1746–1757, 2007 相似文献
84.
We show that between any two nodes of a cubic, planar, three-connected graph there are three paths whose lengths are 0, 1, and 2 modulo 3, respectively. The proof is by a rather extensive case analysis. Counterexamples show that all three hypotheses (i.e., planarity, degree-three, and three-connectivity) are necessary. 相似文献
85.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献
86.
本文描述了用膜吸收法测量激光等离子体辐射温度空间分布的原理和方法给出了柱形缝靶轴向辐射温度随空间位置变化的特征,对测量结果进行了分析讨论。 相似文献
87.
88.
四溴双酚A锑铝双金属化合物的合成及其阻燃性能 总被引:1,自引:0,他引:1
以四溴双酚A(TBA)合成了在水和空气中稳定的四溴双酚A合锑铝双金属化合物(TBASA).通过IR、1HNMR和元素分析予以表征,并研究了其对聚乙烯(PE)和聚环氧乙烷(PEO)的阻燃性能.结果表明,这种分子中含有溴、锑和铝的化合物,对聚乙烯和聚环氧乙烷等高聚物材料有高的阻燃性能与消烟效果. 相似文献
89.
稳态锁模产生4ps激光脉冲 总被引:1,自引:0,他引:1
首次利用GaAs光电导开关,控制Nd:YLF激光器腔内Q值,实现稳态锁模,获得脉宽和能量稳定性极高的4ps激光脉冲。 相似文献
90.
The grain boundary is an interface and the surface tension is one of its important thermodynamic properties. In this paper,
the surface tension of the ∑9 grain boundary for α-Fe at various temperatures and pressures is calculated by means of Computer
Molecular Dynamics (CMD). The results agree satisfactorily with the experimental data. It is shown that the contribution of
entropy to surface tension of grain boundary can be ignored.
The project supported by the National Natural Science Foundation of China and the Science Foundation of Chinese Academy of
Sciences. 相似文献