全文获取类型
收费全文 | 2019篇 |
免费 | 268篇 |
国内免费 | 149篇 |
专业分类
化学 | 1540篇 |
晶体学 | 23篇 |
力学 | 76篇 |
综合类 | 15篇 |
数学 | 195篇 |
物理学 | 587篇 |
出版年
2024年 | 3篇 |
2023年 | 34篇 |
2022年 | 55篇 |
2021年 | 50篇 |
2020年 | 52篇 |
2019年 | 80篇 |
2018年 | 70篇 |
2017年 | 53篇 |
2016年 | 83篇 |
2015年 | 99篇 |
2014年 | 111篇 |
2013年 | 147篇 |
2012年 | 180篇 |
2011年 | 190篇 |
2010年 | 124篇 |
2009年 | 96篇 |
2008年 | 138篇 |
2007年 | 115篇 |
2006年 | 132篇 |
2005年 | 102篇 |
2004年 | 95篇 |
2003年 | 61篇 |
2002年 | 64篇 |
2001年 | 23篇 |
2000年 | 21篇 |
1999年 | 37篇 |
1998年 | 22篇 |
1997年 | 28篇 |
1996年 | 32篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1938年 | 1篇 |
排序方式: 共有2436条查询结果,搜索用时 0 毫秒
81.
T. ?alkus E. Kazakevi?ius A. Ke?ionis V. Kazlauskien? J. Mi?kinis A. Dindune Z. Kanepe J. Ronis M. Dudek M. Bu?ko J. R. Dygas W. Bogusz A. F. Orliukas 《Ionics》2010,16(7):631-637
Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were sintered. The surfaces of the ceramics were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Li1.3Al0.15Y0.15Ti1.7(PO4)3 samples were tested in solid galvanic cells Ag|O2+CO2|Li2CO3|Li1.3Al0.15Y0.15Ti1.7(PO4)3|LiMnO2+Mn2O3|O2|Ag. The electromotive force measurements of this cell indicated that investigated samples are practically pure Li-ion conductors. Impedance spectroscopy studies have been performed in the frequency range 10?2–3·109 Hz and temperatures from ?57 °C to 334 °C. Three dispersion regions related to Li+ ionic transport in bulk, grain boundaries of the ceramics and to polarization of electrodes have been found. Total conductivity changes according to Arrhenius law in the studied temperature range, but an anomalous behavior was observed for the bulk conductivity of the ceramics. 相似文献
82.
提出一种采用Kohonen网络算法进行12电极电容CT系统的图像重建的方法.该网络由输入和输出两层神经元组成,输入为12电极电容CT系统测量所得的66个电容值,输出对应管道介质的空间分布模式.该网络采用竞争算法无监督学习,实验结果证明,该网络有较强的抗噪声能力,可重建出较精确的介质分布图像 相似文献
83.
A liquid chromatographic chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was applied to the resolution of 15 analytes, including racemic rasagiline, a chiral drug for the treatment of Parkinson's disease, and its analogues. The composition of mobile phase was optimized to be ethanol/acetonitrile/acetic acid/triethylamine (80:20:0.2:0.3, v/v/v/v) by evaluating the chromatographic results for the resolution of five selected analytes under various mobile phase conditions. Under the optimized mobile phase conditions, racemic rasagiline was resolved quite well with a separation factor of 1.48 and resolution of 2.71 and its 14 analogues were also resolved reasonably well with separation factors of 1.06–1.54 and resolutions of 0.54–2.11. Among 15 analytes, racemic rasagiline was resolved best except for just one analyte. The analyte structure–enantioselectivity relationship indicated that racemic rasagiline has the most appropriate structural characteristics for resolution on the chiral stationary phase. 相似文献
84.
The anion derived from diethyl malonate reacts with a series of halides readly under microwave irradiation, and the isolated yield of alkylated products varying from 64% to 86%. 相似文献
85.
Rodríguez de Rivera P. J. Rodríguez de Rivera Mi. Socorro F. Rodríguez de Rivera M. Callicó G. M. 《Journal of Thermal Analysis and Calorimetry》2020,142(1):461-471
Journal of Thermal Analysis and Calorimetry - The purpose of the calorimetric sensor developed is to measure the heat flux transmitted by conduction between the human body surface and a thermostat... 相似文献
86.
Fluid Dynamics - Both numerical methods and wind tunnel tests were used to reduce skin friction for a hypersonic body. A hypersonic cone was tested under three different free-stream flow... 相似文献
87.
Journal of Statistical Physics - We construct for the first time examples of non-frustrated, two-body, infinite-range, one-dimensional classical lattice–gas models without periodic... 相似文献
88.
Wei Huang Mi Wang Zhou Hu Lingling Wang Junxin Cao Dewen Kong 《Acta Mechanica Solida Sinica》2021,34(1):137-148
In this study,the strain rate-dependent dynamic tensile behavior of ZrB2-20%SiC ceramic composite was investigated using experimental and numerical approaches.The split Hopkinson pressure bar apparatus was used to measure the dynamic splitting tensile response at strain rates of 17-67 s?1.The experiment results demonstrate a significant strain rate dependence of the dynamic tensile behavior of the ZrB2-SiC ceramic composite.The dynamic tensile strength increased linearly with the strain rate,from 288 MPa at 17 s?1to 654 MPa at 67 s?1.Moreover,a strain rate-dependent tensile strength was introduced into a modified JH-2 model to describe the dynamic tensile behavior and fracture process of ZrB2-SiC ceramics.The numerical results of dynamic tensile strength agree well with the experimental result.Moreover,the fracture process of ZrB2-SiC ceramics under dynamic tension was further studied by combining high-speed images and numerical results.The effect of strain rate on the fracture process and failure patterns of the ZrB2-SiC ceramic composite could be verified by the modified JH-2 model. 相似文献
89.
90.
Sonodynamic therapy (SDT) is a novel tumor therapy method. We investigated membrane fluidity, activity of the enzymes and membrane morphology in vitro post hematoporphyrin-SDT treatment. Furthermore, the potential mechanisms behind the changes in membrane fluidity and enzymic activity were discussed. Tumor cells were exposed to ultrasound at 1.75 MHz for up to 3 min in the presence and absence of hematoporphyrin. Fluorescence polarization, contents of Malonaldehyde, and levels of free fatty acid were assessed. Activity of enzymes was checked by the plumbic nitrate detection method. For the morphologic study, a scanning electron microscope was used to observe the cellular surface. Ultrasonically induced cell damage increased in the presence of HPD (from 15% to 24%). Compared with ultrasound treatment alone, the fluidity decreased from 5.037 to 3.908, malonaldehyde content and free fatty acid level increased from 0.743 nmol/mL to 0.979 nmol/mL and from 237.180 μmol/L to 730.769 μmol/L, respectively, post ultrasound combined with HPD treatment. Inactivity of adenylate cyclase and guanylate cyclase and significant deformation of the cellular surface were also observed post SDT treatment. Our results suggested that alterations in membrane modality and lipid composition played important roles in SDT-mediated inhibition of tumor growth, even inducing tumor cell death, which might be attributed to a sono-chemical activation mechanism. 相似文献