全文获取类型
收费全文 | 5916篇 |
免费 | 455篇 |
国内免费 | 386篇 |
专业分类
化学 | 895篇 |
晶体学 | 27篇 |
力学 | 911篇 |
综合类 | 45篇 |
数学 | 517篇 |
物理学 | 1478篇 |
综合类 | 2884篇 |
出版年
2024年 | 20篇 |
2023年 | 38篇 |
2022年 | 96篇 |
2021年 | 104篇 |
2020年 | 142篇 |
2019年 | 112篇 |
2018年 | 102篇 |
2017年 | 153篇 |
2016年 | 181篇 |
2015年 | 150篇 |
2014年 | 247篇 |
2013年 | 357篇 |
2012年 | 310篇 |
2011年 | 316篇 |
2010年 | 269篇 |
2009年 | 319篇 |
2008年 | 318篇 |
2007年 | 335篇 |
2006年 | 321篇 |
2005年 | 280篇 |
2004年 | 279篇 |
2003年 | 240篇 |
2002年 | 234篇 |
2001年 | 218篇 |
2000年 | 185篇 |
1999年 | 197篇 |
1998年 | 151篇 |
1997年 | 154篇 |
1996年 | 151篇 |
1995年 | 112篇 |
1994年 | 100篇 |
1993年 | 90篇 |
1992年 | 89篇 |
1991年 | 84篇 |
1990年 | 65篇 |
1989年 | 67篇 |
1988年 | 55篇 |
1987年 | 35篇 |
1986年 | 26篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有6757条查询结果,搜索用时 31 毫秒
1.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
2.
采用DIS数字信息化系统,对不同浓度的蓝墨水溶液在激光光源照射下的透射平均照度及照度分布图像进行实验研究,得到了平均照度值随溶液浓度变化的规律。对不同颜色塑料膜片对白炽灯光源透过照度值及照度分布图像进行实验研究得到及其相关之规律。 相似文献
3.
The possibility of realizing SASE Free Election Laser in x-ray waveband with EM-wave wiggler is studied in this paper. SASE effect including saturation length, saturation power and nonlinear process is explored through a 3-D simulation code. A utilization of seed light from laser plasma x-ray is also analyzed, which demonstrates the feature of shortening the interaction length for saturation. The results show that sizeable output power of x-ray laser would be generated with a middle energy electron beam. 相似文献
4.
本文研究了酸性铬蓝K体系用于同时测定钙和慎的显色条件,借助多波长线性回归法处理数据,提出光度测定钙和镁的简便方法,免去了分离手续。应用于三个水样中钙、镁含量的测定,结果满意。 相似文献
5.
6.
7.
8.
用增量有限元法计算金属流动 总被引:1,自引:0,他引:1
利用增量有限元理论 ,对金属材料的变形过程进行模拟。为了模拟工程中塑性变形较大的构件的变形规律 ,在每个加载步迭代完成后自动实现坐标更新。 相似文献
9.
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
10.
Stress-Strain State in the Zone of Load Transfer in a Composite Specimen under Uniaxial Tension 总被引:2,自引:2,他引:0
Kulakov V. L. Tarnopol'skii Yu. M. Arnautov A. K. Rytter J. 《Mechanics of Composite Materials》2004,40(2):91-100
The stress-strain state in the zone of load transfer in a uniaxially stretched specimen made of a unidirectional epoxy carbon-fiber-reinforced plastic (CFRP) is investigated. A parametric analysis of the influence of geometric and mechanical characteristics of the specimen on its stress-strain state is performed by means of finite-element modeling. The parameters allowing us to significantly reduce the dangerous concentration of transverse and tangential stresses are revealed. The mechanical tensile characteristics of a high-strength pultruded unidirectional CFRP are determined experimentally, and the size effect of its strength is estimated. 相似文献