全文获取类型
收费全文 | 6113篇 |
免费 | 1015篇 |
国内免费 | 845篇 |
专业分类
化学 | 4764篇 |
晶体学 | 102篇 |
力学 | 320篇 |
综合类 | 34篇 |
数学 | 699篇 |
物理学 | 2054篇 |
出版年
2024年 | 31篇 |
2023年 | 116篇 |
2022年 | 218篇 |
2021年 | 240篇 |
2020年 | 281篇 |
2019年 | 288篇 |
2018年 | 240篇 |
2017年 | 213篇 |
2016年 | 342篇 |
2015年 | 350篇 |
2014年 | 383篇 |
2013年 | 498篇 |
2012年 | 535篇 |
2011年 | 561篇 |
2010年 | 398篇 |
2009年 | 364篇 |
2008年 | 376篇 |
2007年 | 309篇 |
2006年 | 317篇 |
2005年 | 239篇 |
2004年 | 240篇 |
2003年 | 178篇 |
2002年 | 229篇 |
2001年 | 169篇 |
2000年 | 114篇 |
1999年 | 107篇 |
1998年 | 68篇 |
1997年 | 66篇 |
1996年 | 48篇 |
1995年 | 36篇 |
1994年 | 51篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 32篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 6篇 |
排序方式: 共有7973条查询结果,搜索用时 0 毫秒
11.
The rate of nucleophilic substitution at the phosphorus centre of dialkyl methylphosphonates by methoxide and ethoxide has been studied to investigate the possible involvement of hexacoordinated phosphorus species in this reaction. For alkoxide concentrations less than ca. 1.5 M the rate increases with the square of alkoxide concentration. However, consideration of the activity of the alkoxides, represented by an appropriate acidity function, reveals that only one equivalent of alkoxide is involved in the rate-determining step. Thus, there is no requirement to invoke the intermediacy of a hexacoordinated species in the reaction pathway. © John Wiley & Sons, Inc. 相似文献
12.
13.
The central zinc(II) atom in the title complex is tetrahedrally coordinated by four nitrogen atoms derived from 4‐methyl‐5‐imidazolecarboxyaldehyde ligands with Zn? N in the range 2.007(3) to 2.026(4) Å. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
14.
A one‐dimensional zinc(II) coordination polymer has been constructed from zinc(II), 4,4′‐biphenyldicarboxylate and pyridine in which each zinc(II) atom is coordinated by two pyridine ligands and two monodentate 4,4′‐biphenyldicarboxylate ligands that define a distorted tetrahedral geometry. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
15.
DING Xuantong YANG Qingwei YAN Long wen LIU Yi HUANG Yuan LIU Zetian HONG Wenyu SHI Peilan 《核工业西南物理研究院年报(英文版)》2004,(1):1-4
The main mission the HL-2A tokamak is of the experiments on to explore the divertor physics and to investigate the plasma confinement, transport and instabilities with high power auxiliary heating and advanced fuelling, it is necessary to develop more new diagnostics and increase the spatial and temporal resolutions of the measurements for exist system. Up to now, about 30 diagnostic systems have been moved from HL-1M to HL-2A tokamak. Other 10 diagnostic systems are being designed and installed on the device. In developed in last 2 years, will be presented. 相似文献
16.
由于腔模与激子对压力的依赖关系不同,所以可以选择不同的压力使激子和光场处于不同的耦合状态,从而实现对耦合的调谐。利用这种办法,我们观测到了代表激子与光场强耦合作用的Rabi分裂。由于在我们现有样品结构中压力对激子本征行为的影响很小,与以前报道的温度、电场等调谐方式相比,这种调谐方法不仅可以有效地调谐半导体微腔内激子与腔模的耦合程度,而且能够保持激子的本征性质在整个调谐过程中基本不变。这有助于研究在强耦合过程中激子极化激元的本征性质。将实验结果与压力下激子与腔模耦合理论进行拟合,得出了正确的Rabi分裂值。 相似文献
17.
18.
19.
Modeling synchronization and suppression of spontaneous otoacoustic emissions using Van der Pol oscillators: effects of aspirin administration 总被引:1,自引:0,他引:1
Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (suppression and synchronization) can be qualitatively simulated by the behavior of a single driven Van der Pol oscillator. Analytical and numerical investigations of a model of spontaneous otoacoustic emissions based on such an oscillator (with appropriate parametric changes in the nonlinear and negative damping components) lead to predictions of the nature of the changes in suppression and synchronization (frequency-locking) tuning curves when the levels of spontaneous otoacoustic emissions are modified. Observations of the suppression and synchronization of spontaneous otoacoustic emissions by external tones of different frequencies and levels were obtained while the levels of spontaneous emissions were altered by aspirin administration. Modeling an emission as a single Van der Pol oscillator qualitatively accounts for: (1) the reduction of the level of an external tone required to suppress the emission by a decibel amount equivalent to the level reduction induced by aspirin administration; (2) the broadening of the frequency-locking tuning curve of an emission whose level is reduced; and (3) the pulling of the emission frequency by an external tone. It does not account for: (1) the observed asymmetry in the slopes of the external-tone suppression curves (more gradual for frequencies of the suppressor tone higher, rather than lower, than that of the emission); and (2) the frequency pushing of the emission by an external tone. 相似文献
20.
A simple “chimney” method was used to eliminate the voids in an arrangement of quantum dots sized 2 nm on a solid substrate, which resulted in a large well ordered superlattice of area in the order more than 1 μm2. Based on the principle of speeding up the interparticle interaction of nanoparticles to overcome the particle-substrate one, a lateral centripetal force originated from a glass tube acting as a chimney in a simple evaporation device is imposed. This method allows the packing process to be controlled in a mechanical force field, that is, with the same nanogold dispersion different patterns on a substrate—from separate dots to an ordered compact monolayer or even a multilayer structure—could be easily obtained. 相似文献