全文获取类型
收费全文 | 896篇 |
免费 | 144篇 |
国内免费 | 299篇 |
专业分类
化学 | 694篇 |
晶体学 | 51篇 |
力学 | 45篇 |
综合类 | 15篇 |
数学 | 104篇 |
物理学 | 430篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 31篇 |
2021年 | 35篇 |
2020年 | 29篇 |
2019年 | 26篇 |
2018年 | 30篇 |
2017年 | 31篇 |
2016年 | 34篇 |
2015年 | 40篇 |
2014年 | 37篇 |
2013年 | 63篇 |
2012年 | 68篇 |
2011年 | 67篇 |
2010年 | 72篇 |
2009年 | 93篇 |
2008年 | 86篇 |
2007年 | 82篇 |
2006年 | 84篇 |
2005年 | 63篇 |
2004年 | 49篇 |
2003年 | 38篇 |
2002年 | 25篇 |
2001年 | 31篇 |
2000年 | 46篇 |
1999年 | 23篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 20篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1969年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有1339条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
自动寻峰是进行光谱原位探测、实时自动分析的必要环节,对拓展光谱分析技术到长期海洋监测、石油录井等应用领域具有重要意义。该研究以实验室中获得的LIBS/Raman光谱数据,对Gaussian,Lorenz,Voigt三种线型函数构建的对称零面积变换函数进行了比较研究。结果证明各个光谱峰都存在一个最优的对称零面积变换函数,但三种变换函数在各自的最优化参数下获得的峰位、峰宽一致;以实验室中LIBS和Raman光谱定量实验数据对该方法的测试还证明,对称零面积变换寻峰方法对信号的大范围动态变化适应性强,弱峰识别能力达到或优于人工识别水平,有望应用于将来的LIBS/Raman自动原位分析中去。 相似文献
5.
The problem of calculating the non-retarded Van der Waals type of interaction between two spherical voids in an electron gas is presented from a new approach. The formulation is based on an integral equation for the self-induced density oscillations derived from a semi-classical treatment of the density-density response theory for inhomogeneous electron systems. The interaction energy between two identical voids is found to obey d-6 law for large separation d between the voids, the law being determined by the dipolar plasma oscillations alone. 相似文献
6.
Skorodumova NV Simak SI Lundqvist BI Abrikosov IA Johansson B 《Physical review letters》2002,89(16):166601
The microscopic mechanism behind the extraordinary ability of ceria to store, release, and transport oxygen is explained on the basis of first-principles quantum mechanical simulations. The oxygen-vacancy formation energy in ceria is calculated for different local environments. The reversible CeO2-Ce2O3 reduction transition associated with oxygen-vacancy formation and migration is shown to be directly coupled with the quantum process of electron localization. 相似文献
7.
The accelerators should be properly designed to make the radiation field produced by beam loss satisfy the dose limits. The radiation field for high intensity H- cyclotron includes prompt radiation and residual radiation field. The induced radioactivity in accelerator components is the dominant source of occupational radiation exposure if the accelerator is well shielded. The source of radiation is the beam loss when cyclotron is operating. In this paper, the radiation field for CYCIAE-100 is calculated using Monte Carlo method and the radioactive contamination near stripping foil is studied. A method to reduce the dose equivalent rate of maintenance staff is also given. 相似文献
8.
The performance of a domestic heat pump that uses a low quantity of propane as refrigerant has been experimentally investigated. The heat pump consists of two minichannel aluminium heat exchangers, a scroll compressor, and an electronic expansion valve. It was charged with the minimum amount of refrigerant propane required for the stable operation of the heat pump without permitting refrigerant vapor into the expansion valve at incoming heat source fluid temperature to the evaporator of +10°C. The inlet temperature of the heat source fluid passing through the evaporator was varied from +10°C to ?10°C while holding the condensing temperature constant at 35°C, 40°C, 50°C, and 60°C, respectively. The minimum refrigerant charges required at above-tested condensing temperatures were found to decrease when the condensing temperature increased and were recorded as 230 g, 224 g, 215 g, and 205 g, respectively. The results confirm that a heat pump with 5 kW capacity can be designed with less than 200 g charge of refrigerant propane in the system. Due to the high solubility of propane in compressor lubrication oil, the amount of refrigerant which may escape rapidly in case of accident or leakage is less than 150 g. 相似文献
9.
We present some singular wave solutions such as multi-peaked periodic waves, multi-peaked kink waves, multi-peaked peakons as well as kink-compactons, associated with singular curves of generalized KdV equation and modified KdV equation. When a trajectory intersects with the singular curve, it may be divided into segments. Different combinations of these segments may lead to different singular wave solutions, while at the intersection points, peaks on the waves can be observed. 相似文献
10.
Chua 's circuit with a slow-fast effect is established under certain parameter conditions. The dynamics of this slow- fast system is investigated. A spiking phenomenon can be observed in the numerical simulation. By introducing slow-fast analysis and a generalized Jacobian matrix at the non-smooth boundaries, the bifurcation mechanism for the periodic spiking solution, different from the smooth case, is discussed. 相似文献