全文获取类型
收费全文 | 12344篇 |
免费 | 2035篇 |
国内免费 | 2003篇 |
专业分类
化学 | 9409篇 |
晶体学 | 169篇 |
力学 | 716篇 |
综合类 | 172篇 |
数学 | 1326篇 |
物理学 | 4590篇 |
出版年
2024年 | 9篇 |
2023年 | 268篇 |
2022年 | 272篇 |
2021年 | 363篇 |
2020年 | 536篇 |
2019年 | 487篇 |
2018年 | 400篇 |
2017年 | 421篇 |
2016年 | 597篇 |
2015年 | 586篇 |
2014年 | 713篇 |
2013年 | 953篇 |
2012年 | 1040篇 |
2011年 | 1142篇 |
2010年 | 750篇 |
2009年 | 793篇 |
2008年 | 827篇 |
2007年 | 689篇 |
2006年 | 663篇 |
2005年 | 619篇 |
2004年 | 491篇 |
2003年 | 437篇 |
2002年 | 495篇 |
2001年 | 401篇 |
2000年 | 326篇 |
1999年 | 310篇 |
1998年 | 192篇 |
1997年 | 166篇 |
1996年 | 200篇 |
1995年 | 161篇 |
1994年 | 167篇 |
1993年 | 152篇 |
1992年 | 123篇 |
1991年 | 100篇 |
1990年 | 86篇 |
1989年 | 89篇 |
1988年 | 60篇 |
1987年 | 61篇 |
1986年 | 57篇 |
1985年 | 38篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1959年 | 4篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
101.
102.
Wenran Feng Chizi Liu Guangliang Chen Guling Zhang Weichao Gu Erwu Niu Si-Ze Yang 《Applied Surface Science》2007,253(11):4923-4927
Hard films prepared by pulsed high energy density plasma (PHEDP) are characterized by high film/substrate adhesive strength, and high wear resistance. Titanium carbonitride (TiCN) films were deposited onto YG11C (ISO G20) cemented carbide cutting tool substrates by PHEDP at room temperature. XRD, XPS, SEM, AES, etc. were adopted to analyze the phases (elements) composition, microstructure and the interface of the films, respectively. The results show that, the uniform dense films are composed of grains ranging from 70 to 90 nm. According to the AES result, there is a broad transition layer between the film and the substrate, due to the ion implantation effect of the PHEDP. The transition layer is favorable for the film/substrate adhesion. 相似文献
103.
104.
本文提出一种利用材料Hugoniot数据研究高压下离子晶体中微观离子状态及其离子间排斥作用势的新方法。对氢化锂晶体进行研究时,我们得到Li~+和H~-离子之间排斥作用势函数,结果表明文献〔1〕中提出的离子压缩效应具有客观性。 相似文献
105.
Super-Wavelets and Decomposable Wavelet Frames 总被引:4,自引:0,他引:4
A wavelet frame is called decomposable whenever it is equivalent to a superwavelet frame of length greater than one. Decomposable
wavelet frames are closely related to some problems on super-wavelets. In this article we first obtain some necessary or sufficient
conditions for decomposable Parseval wavelet frames. As an application of these conditions, we prove that for each n > 1 there
exists a Parseval wavelet frame which is m-decomposable for any 1 < m ≤ n, but not k-decomposable for any k > n. Moreover,
there exists a super-wavelet whose components are non-decomposable. Similarly we also prove that for each n > 1, there exists
a Parseval wavelet frame that can be extended to a super-wavelet of length m for any 1 < m ≤ n, but can not be extended to
any super-wavelet of length k with k > n. The connection between decomposable Parseval wavelet frames and super-wavelets is
investigated, and some necessary or sufficient conditions for extendable Parseval wavelet frames are given. 相似文献
106.
A new synthetic method for the manufacture of glutaric dialdehyde is investigated. Glutaric dialdehyde was prepared by the
addition-hydrolysis reaction of benzimidazolium salt with saturated dihalide as the di-Grignard reagent. The yield of glutaric
dialdehyde by this method can reach 73%. Both infrared spectra and melting point of the compound were consistent with those
reported earlier.
Translated from Journal of Northwest University (Natural Science Edition), 2005, 35(2) (in Chinese) 相似文献
107.
R. Silvennoinen K. -E. Peiponen T. Asakura Yan-Fang Zhang Cong Gu K. Ikonen E. J. Morley 《Optics and Lasers in Engineering》1992,17(2)
The specular reflectance of cold-rolled aluminum surface is studied using a fiber optic system. An approximation for the determination of surface roughness is presented. 相似文献
108.
In this article, the linear and nonlinear shear rheological behaviors of polylactide (PLA)/clay (organophilic‐montmorillonite) nanocomposites (PLACNs) were investigated by an Advanced Rheology Expanded System rheometer. The nanocomposites were prepared by master batch method using a twin‐screw extruder with poly(ε‐caprolactone) (PCL) as a compatibilizer. The presence of org‐MMT leads to obvious pseudo‐solid‐like behaviors of nanocomposite melts. The behaviors caused by the formation of a “percolating network” derived from the reciprocity among the strong related sheet particles. Therefore, the storage moduli, loss moduli, and dynamic viscosities of PLACNs show a monotonic increase with MMT content. Nonterminal behaviors exists in PLACNs nanocomposites. Besides the PLACNs melts show a greater shear thinning tendency than pure PLA melt because of the preferential orientation of the MMT layers. Therefore, PLACNs have higher moduli but better processibility compared with pure PLA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3189–3196, 2007 相似文献
109.
Below a critical thickness, of about 60 nm, the glass transition temperature of polystyrene (PS) films decreases with film thickness, as demonstrated using free‐standing films. A geometrical model is developed here describing this phenomenon in the case of ideal (Gaussian) chains. This model, which can be considered as an application of the free volume model, assumes that the decrease of the glass transition temperature from thick to ultrathin films is due to the modification of the interpenetration between neighboring chains. The theoretical curve deduced from the model is in excellent agreement with the PS experimental results, without using any adjustable parameters. From these results, it can be concluded that new chain motions, usually buried in bulk samples, are expressed by the presence of the surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 10–17, 2007 相似文献
110.
Synthesis of enantiomeric-pure cyclohexenyl nucleoside building blocks for oligonucleotide synthesis
Lipases were used for the resolution of (±) (4aR, 7R, 8aS)-2-phenyl-4a,7,8,8a-tetrahydro-4H-1,3-benzodioxine. This separation was carried out on preparative scale and used for the synthesis of eight phosphoramidites of cyclohexenyl nucleosides (d- and l-series). 相似文献