全文获取类型
收费全文 | 12115篇 |
免费 | 477篇 |
国内免费 | 662篇 |
专业分类
化学 | 2200篇 |
晶体学 | 58篇 |
力学 | 3447篇 |
综合类 | 33篇 |
数学 | 833篇 |
物理学 | 6683篇 |
出版年
2024年 | 17篇 |
2023年 | 111篇 |
2022年 | 125篇 |
2021年 | 136篇 |
2020年 | 237篇 |
2019年 | 264篇 |
2018年 | 231篇 |
2017年 | 233篇 |
2016年 | 493篇 |
2015年 | 466篇 |
2014年 | 546篇 |
2013年 | 629篇 |
2012年 | 527篇 |
2011年 | 859篇 |
2010年 | 572篇 |
2009年 | 798篇 |
2008年 | 795篇 |
2007年 | 751篇 |
2006年 | 763篇 |
2005年 | 653篇 |
2004年 | 620篇 |
2003年 | 543篇 |
2002年 | 419篇 |
2001年 | 300篇 |
2000年 | 321篇 |
1999年 | 225篇 |
1998年 | 316篇 |
1997年 | 167篇 |
1996年 | 130篇 |
1995年 | 174篇 |
1994年 | 128篇 |
1993年 | 109篇 |
1992年 | 89篇 |
1991年 | 76篇 |
1990年 | 53篇 |
1989年 | 60篇 |
1988年 | 51篇 |
1987年 | 38篇 |
1986年 | 37篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 21篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 13篇 |
1971年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
用经典力学和双波量子力学计算了氢原子的固有电偶极矩。双波量子理论算得的结果在经典极限下与经典力学的结果一致。普通量子力学对氢原子Stark效应中表现出来的电偶极矩难以做出很好的解释,因为一个波函数描述的是系综而不是单个粒子。经典力学和双波量子力学可描述单个粒子的行为,对永久电偶极矩的计算和解释显得自然而合理。 相似文献
92.
Fabio Scardigli 《Foundations of Physics》2007,37(8):1278-1295
The Titius–Bode law for planetary distances is reviewed. A model describing the basic features of this rule in the “quantum-like”
language of a wave equation is proposed. Some considerations about the ’t Hooft idea on the quantum behavior of deterministic
systems with dissipation are discussed. 相似文献
93.
Wolfgang W. Schoeller 《无机化学与普通化学杂志》2003,629(5):816-827
The particular role of the phosphaneiminato ligand as a donor is investigated for a) nitrenes (phosphinidenes) and carbenes and b) cubane formation with transition metals. Accordingly, and as shown for the case a) the ligand is a stronger π‐donor than an amino group and can be considered as a special case of imine‐type substituents. The latter are very effective in π‐donation. In the case b), i.e. the cubane formation with transition metals, one has to consider transition metals with a partially or completely filled d‐shell (with electrons). Hence depending on the transition metal, cubanes are build with weak ferromagnetic coupled or closed shell systems. For the cubanes with closed shell character the matter of insertion of halide anions is discussed. In the last chapter of the review the bond stretching in the dithionitrosyl complexes with rhenium is characterized. 相似文献
94.
应用密度矩阵方程计算了四能级原子系统中三阶非线性极化率随信号光和探针光频率失谐的变化关系。结果表明,由于量子干涉对信号光强度的敏感性,使四能级原子介质的交叉Kerr非线性作用大大增强,与三能级系统相比,四能级原子介质的Kerr非线性系数可增强两个数量级。 相似文献
95.
以一种新型的醌类光敏剂—菌生素 (HMB)为模型化合物 ,利用量子化学从头算HF/ 6 31G和含时密度泛函TD B3LYP/ 6 31G方法计算研究了卤代作用对醌类光敏剂分子性质和光敏活性的影响 .结果发现 ,卤代作用降低了HMB母体的HOMO和LUMO能级 (EHOMO和ELUMO)及其差值△E ,随卤族元素从上到下 ,EHOMO和ELUMO呈增大趋势 ,而△E呈减小趋势 ,使得分子激发光谱有不同程度的红移 ,在增加PQP三重态量子产率的同时降低了分子最低三重激发态的能量 ,两种作用相互抵消 ,使得卤代物的 1O2 量子产率与母体相似 ;增加了分子的绝热电子亲合势 ,使分子产生O2 -的能力下降 ;卤原子的引入 ,降低了HMB母体分子内氢键的强度 ,同时使顺式构型的分子内质子传递势垒增大 ,而使反式构型势垒减小 . 相似文献
96.
K. Suzuki S. Miyashita K. Takashina Y. Hirayama 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):232
We investigate the quantum Hall effect (QHE) in the InAs/GaSb hybridized electron–hole system grown on a conductive InAs substrate which act as a back-gate. In these samples, the electron density is constant and the hole density is controlled by the gate-voltage. Under a magnetic field perpendicular to the sample plane, the QHE appears along integer Landau-level (LL) filling factors of the net-carriers, where the net-carrier density is the difference between the electron and hole densities. In addition, longitudinal resistance maxima corresponding to the crossing of the extended states of the original electron and hole LLs make the QHE regions along integer-νnet discontinuous. Under tilted magnetic fields, these Rxx maxima disappear in the high magnetic field region. The results show that the in-plane magnetic field component enhances the electron–hole hybridization and the formation of minigaps at LL crossings. 相似文献
97.
V. F. Radantsev V. V. Kruzhaev G. I. Kulaev 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):396
The Rashba effect in metal–insulator–semiconductor (MIS) structures based on zero-gap HgCdTe is investigated experimentally and theoretically over a wide doping range NA–ND=3×1015–3×1018 cm−3. Increase of doping enlarges the magnitude of the effect at the same 2D concentration and strengthens a gate-voltage dependence of the Rashba splitting. The results demonstrate values of Rashba polarization as high as PR0.5 and a capability to control the Rashba effect strength at constant electron concentration. 相似文献
98.
D. T. Le C. P. Morath H. E. Norton D. A. Cardimona S. Raghavan P. Rotella S. A. Stintz B. Fuchs S. Krishna 《Infrared Physics & Technology》2003,44(5-6):517-526
In this paper we report studies on normal incidence, InAs/In0.15Ga0.85As quantum dot infrared photodetectors (QDIPs) in the dots-in-a-well (DWELL) configuration. Three QDIP structures with similar dot and well dimensions were grown and devices were fabricated from each wafer. Of the three devices studied, the first served as the control, the second was grown with an additional 400 Å AlGaAs blocking layer, and the third was grown on a GaAs n+ substrate with the intention of testing a single pass geometry. Spectral measurements on all three devices show one main peak in the long-wave IR (≈8 μm). The absorption was attributed to the bound-to-bound transition between the ground state of the InAs quantum dot and the ground state of the In0.15Ga0.85As well. Calibrated peak responsivity and peak detectivity measurements were performed on each device at 40, 60, and 80 K. For the same temperatures, frequency response measurements from 20 Hz to 4 kHz at a bias of Vb=−1 V were also performed. The addition of the blocking layer was shown to slightly enhance responsivity, which peaked at 2.4 A/W at 77 K, Vb=−1 V and responsivity was observed to be significantly reduced in the single pass (n+ substrate) sample. The rolloff of the frequency response was observed to be heavily dependent on temperature, bias, and irradiance. The results from the characterization of each sample are reported and discussed. 相似文献
99.
100.
简要介绍《新概念物理教程:力学》的知识体系、特色及改革新意.结合南阳师院2000级、2001级两届本科班对新教材的使用情况,制定适合我院学生实际的力学教学大纲,探索一种以知识为载体、以学生为主体、以培养学生科学素质为宗旨的新型教学模式.对教学中遇到的问题提出具体的解决办法,对使用新教材的效果进行调查分析,为力学教材的使用和力学教学改革提供一些参考。 相似文献