全文获取类型
收费全文 | 11799篇 |
免费 | 1854篇 |
国内免费 | 1370篇 |
专业分类
化学 | 8263篇 |
晶体学 | 380篇 |
力学 | 1152篇 |
综合类 | 118篇 |
数学 | 278篇 |
物理学 | 4832篇 |
出版年
2024年 | 26篇 |
2023年 | 94篇 |
2022年 | 311篇 |
2021年 | 403篇 |
2020年 | 407篇 |
2019年 | 328篇 |
2018年 | 324篇 |
2017年 | 452篇 |
2016年 | 503篇 |
2015年 | 413篇 |
2014年 | 541篇 |
2013年 | 1145篇 |
2012年 | 656篇 |
2011年 | 679篇 |
2010年 | 493篇 |
2009年 | 618篇 |
2008年 | 678篇 |
2007年 | 728篇 |
2006年 | 703篇 |
2005年 | 642篇 |
2004年 | 614篇 |
2003年 | 533篇 |
2002年 | 540篇 |
2001年 | 429篇 |
2000年 | 437篇 |
1999年 | 387篇 |
1998年 | 305篇 |
1997年 | 274篇 |
1996年 | 234篇 |
1995年 | 214篇 |
1994年 | 199篇 |
1993年 | 180篇 |
1992年 | 150篇 |
1991年 | 60篇 |
1990年 | 63篇 |
1989年 | 44篇 |
1988年 | 48篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 7篇 |
1973年 | 6篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
11.
12.
13.
The dependence of the beam propagation factor (M
2 parameter) with the absorbed pump power in the case of monolithic microchip laser under face-cooled configuration is extensively
studied. Our investigations show that the M
2 parameter is related to the absorbed pump power through two parameters (α and β) whose values depend on the laser material properties and laser configuration. We have shown that one parameter arises due
to the oscillation of higher order modes in the microchip cavity and the other parameter accounts for the spherical aberration
associated with the thermal lens induced by the pump beam. Such dependency of M
2 parameter with the absorbed pump power is experimentally verified for a face-cooled monolithic microchip laser based on Nd3+ -doped GdVO4 crystal and the values of α and β parameters were estimated from the experimentally measured data points. 相似文献
14.
The quantum states are presented in these processions of fabricating poly-Si films. Amorphous silicon films prepared by PECVD has been crystallized by conventional furnace annealing (FA) and rapid thermal annealing (RTA), respectively. It is found that the thin films grain size present quantum states with the increasing of the gas flow ratios of SiH4, H2 mixture, substrate temperatures, frequency power, annealing temperature and time. 相似文献
15.
16.
17.
通过改变带细玻璃管的烧瓶中水的温度导致水位变化来粗略演示水的收缩情况.为较准确测定水最大密度时的温度,将2个温度计放在水下较浅处和较深处,分别测量当温度经由4℃升高时和由4℃降低时两温度计的示数,进而验证水的反常热膨胀特性. 相似文献
18.
以CF4和C6H6的混合气体作为气源,在微波电子回旋共振化学气相沉积(ECRCVD)装置中制备了氟化非晶碳薄膜(aC:F),并在N2气氛中作了退火处理以考察其热稳定性.通过傅里叶变换红外吸收谱和紫外可见光谱获得了薄膜中CC双键的相对含量和光学带隙,发现膜中CC键含量与光学带隙之间存在着密切的关联,在高微波功率下沉积的氟化非晶碳膜具有低的光学带隙和较好的热稳定性.
关键词:
氟化非晶碳膜
光学带隙
退火温度
热稳定性 相似文献
19.
The diffusion of the anti-microbial chlorhexidine digluconate (CHG) has been studied in C. albicans biofilms by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). C. albicans has been shown to become resistant to common anti-microbial agents, including CHG, when growing as a biofilm. Mass transport resistance within biofilms has commonly been suggested as a resistance mechanism, but measurement of transport for most anti-microbial agents in biofilms has proven extremely difficult because of the heterogeneity of the biofilms and the difficulty in detecting these agents within an intact biofilm. In this study, TOF-SIMS has been used to study the transport of CHG and glucose in a frozen hydrated biofilm. The TOF-SIMS images reveal a progression of CHG from the top of the biofilm to its base with time. Images suggest that there are channels within the biofilm and show preferential binding of CHG to cellular components of the biofilm. Additionally, both living and dead cells can be identified in the TOF-SIMS images by the sequestration of K+ and the presence of cell markers. This study demonstrates that TOF-SIMS has the unique potential to simultaneously observe the presence of an antimicrobial agent, concentration of nutrients, and the viability of the cell population. 相似文献
20.
During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic
long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as
unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible
existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon
by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film
repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively
increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance.
This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length
scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize
around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded
water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading
to the possible creation of a hydrophobic interfacial gap. 相似文献