全文获取类型
收费全文 | 1653篇 |
免费 | 206篇 |
国内免费 | 219篇 |
专业分类
化学 | 477篇 |
晶体学 | 7篇 |
力学 | 903篇 |
综合类 | 40篇 |
数学 | 214篇 |
物理学 | 437篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 28篇 |
2021年 | 56篇 |
2020年 | 53篇 |
2019年 | 47篇 |
2018年 | 53篇 |
2017年 | 67篇 |
2016年 | 83篇 |
2015年 | 72篇 |
2014年 | 99篇 |
2013年 | 113篇 |
2012年 | 81篇 |
2011年 | 103篇 |
2010年 | 69篇 |
2009年 | 116篇 |
2008年 | 121篇 |
2007年 | 93篇 |
2006年 | 108篇 |
2005年 | 89篇 |
2004年 | 71篇 |
2003年 | 75篇 |
2002年 | 53篇 |
2001年 | 49篇 |
2000年 | 52篇 |
1999年 | 49篇 |
1998年 | 38篇 |
1997年 | 27篇 |
1996年 | 40篇 |
1995年 | 31篇 |
1994年 | 31篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有2078条查询结果,搜索用时 500 毫秒
111.
112.
113.
Xue Bai Shujin Li Bin Cong Xia Li Xia Guo Lujun He Jian Ye Li Pei 《Electrophoresis》2010,31(17):2944-2948
MiniSTR loci have been demonstrated to be an effective approach in recovering genetic information from degraded specimens, because of the reduced PCR amplicon sizes which improved the PCR efficiency. Eight non‐combined DNA index system miniSTR loci suitable for the Chinese Han Population were analyzed in 300 unrelated Chinese Han individuals using two novel five fluorescence‐labeled miniSTR multiplex systems(multiplex I: D10S1248, D2S441, D1S1677 and D9S2157; multiplex II: D9S1122, D10S1435, D12ATA63, D2S1776 and Amelogenin). The allele frequency distribution and forensic parameters in the Chinese Han Population were reported in this article. The Exact Test demonstrated that all loci surveyed here were found to be no deviation from Hardy–Weinberg equilibrium. The accumulated power of discrimination and power of exclusion for the eight loci were 0.999999992 and 0.98, respectively. The highly degraded DNA from artificially degraded samples and the degraded forensic case work samples was assessed with the two miniSTR multiplex systems, and the results showed that the systems were quite effective. 相似文献
114.
A non-closed hydrothermal synthetic processing is improved to synthesize Sm3+ doped β-NaYbF4 nano-phosphors at 98 °C without any high-temperature and high-pressure treatments as a final step. Novel green, red, and near-infrared broadband (799-873 nm) upconversion emissions of Sm3+-doped β-NaYbF4 nano-phosphors under 980 nm excitation are observed. These UC emissions can be assigned to the Sm3+ transitions of 4GJ, 4F3/2 and 6F11/2→6HJ. The half-width of 873 nm emission band is broadened nearly two-fold through the annealing treatment for nano-phosphors. The upconversion process in Yb3+-Sm3+ system is discussed based on energy transfer mechanisms. 相似文献
115.
CUI YuanQing & YANG Wei School of Aerospace Engineering Applied Mechanics Tongji University Shanghai China University Office Zhejiang University Hangzhou 《中国科学:物理学 力学 天文学(英文版)》2011,(5)
Experimental results indicate three regimes for cracking in a ferroelectric double cantilever beam (DCB) under combined electromechanical loading. In the loading, the maximum amplitude of the applied electric field reaches almost twice the coercive field of ferroelectrics. Thus, the model of small scale domain switching is not applicable any more, which is dictated only by the singular term of the crack tip field. In the DCB test, a large or global scale domain switching takes place instead, which is driven... 相似文献
116.
Xue-Long HeMei Liu Guan-Jun YangSheng-Qiang Fan Chang-Jiu Li 《Applied Surface Science》2011,258(4):1377-1384
Flexible Pt counter electrodes (CEs) were prepared on indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) substrate by electroless deposition. The correlation between the microstructure and the property of the Pt CEs was investigated. Results showed that isolated Pt nanoparticles were uniformly distributed on the ITO surface at a short deposition duration, and then grew with the deposition duration, leading to the interconnection of adjacent Pt nanoparticles. The interconnection of Pt nanoparticles was beneficial to the electrical property of the Pt CEs, while it was unfavorable to the electrocatalytic property of the Pt CEs. A microstructure model was proposed to explain the correlation between the microstructure and the property of the Pt CEs. In addition, the Pt CEs showed low charge transfer resistance (1.66-0.58 Ω cm2), which was comparable to that (1.16 Ω cm2) of the conventional sputtered Pt CE. The high electrocatalytic property of the electroless deposited Pt CEs makes the assembled DSCs present comparable energy conversion efficiency of the DSCs using sputtered Pt CE. 相似文献
117.
进入特高含水期后,开展注采系统调整挖潜剩余油是油田持续稳产的关键.为了提高特高含水阶段油田采收率,提出井震结合方法精细标定构造层位、认识储层特征,构建地质模型并数值模拟剩余油分布,针对剩余油应用井震结合解释成果设计注采系统调整方案并优化相应注水强度.实验区块研究结果表明:特高含水期,采用井震结合注采系统调整方法最终产油量和采收率分别提高31.21×10~4t和1.54%,能够达到有效挖潜剩余油的目的;而改变注水强度对最终开发效果影响显著,随着注水强度增加,采收率先增大后减小,存在最佳的注水强度为9m~3/d·m. 相似文献
118.
对变系数组合ZK方程进行白噪声扰动得到的Wick型随机组合ZK方程进行了研究.在Kondratiev分布空间(S)-1中利用白噪声分析,Hermite变换和多项式展开法,得到Wick型随机组合ZK方程的白噪声泛函解和变系数组合ZK方程的精确解. 相似文献
119.
P.V. Yasniy I.B. Okipnyi P.O. Maruschak R.T. Bishchak A.P. Sorochak 《Theoretical and Applied Fracture Mechanics》2011,56(2):63-67
Fracture toughness of heat-resistant steel can be increased by a preliminary thermomechanical loading called warm pre-stressing (WPS). The procedure creates a plastic deformed area around the crack tip and hence allows larger service loads to be tolerated by the cracked specimen. It is shown that a hydrogenation in the preloading stage decreases the fracture toughness of material.Investigations are also presented of the applicability of physical and mechanical approaches for the prediction of cleavage stress of materials after preliminary plastic deformation (PPD) effects and hydrogenation. Different schemes of the plastic deformation and influence of hydrogenation are considered in the preloading stage to provide different levels cleavage stress of steel 15Kh2MFA. 相似文献
120.
This paper describes an Integer Programming model for generating stable loading patterns for the Pallet Loading Problem under several stability criteria. The results obtained during evaluation show great improvement in the number of stable patterns in comparison with results reported earlier. Moreover, most of the solved cases also ensure optimality in terms of utilization of a pallet. 相似文献