全文获取类型
收费全文 | 1298篇 |
免费 | 121篇 |
国内免费 | 93篇 |
专业分类
化学 | 1007篇 |
晶体学 | 14篇 |
力学 | 42篇 |
综合类 | 3篇 |
数学 | 170篇 |
物理学 | 276篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 29篇 |
2021年 | 39篇 |
2020年 | 37篇 |
2019年 | 51篇 |
2018年 | 38篇 |
2017年 | 32篇 |
2016年 | 51篇 |
2015年 | 52篇 |
2014年 | 48篇 |
2013年 | 68篇 |
2012年 | 102篇 |
2011年 | 87篇 |
2010年 | 70篇 |
2009年 | 55篇 |
2008年 | 73篇 |
2007年 | 61篇 |
2006年 | 65篇 |
2005年 | 66篇 |
2004年 | 53篇 |
2003年 | 41篇 |
2002年 | 61篇 |
2001年 | 59篇 |
2000年 | 41篇 |
1999年 | 33篇 |
1998年 | 14篇 |
1997年 | 22篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1512条查询结果,搜索用时 15 毫秒
21.
J. Lorenzen H. Morgner W. Bußert M. -W. Ruf H. Hotop 《Zeitschrift für Physik A Hadrons and Nuclei》1983,310(3):141-152
High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(Ne(3s 3 P 2,3 P 0) atoms are reported. The electron spectra for Ne(3 P 2)+H(D) are very broad: The high energy part due to formation of NeH+ (NeD+) bound states (associative ionization), amounts to about 30% of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depthD e [Ne(3 P 2)?H,D]= 2.0(1) eV. The spectra for Ne(3 P 0)+H, D are comparatively narrow with much lower cross sections than the one for the Ne(3 P 2) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1 eV. A perturbation calculation of the Ne(3s)+H(1s) potential energy curves at large distances explains the observed difference between the Ne(3 P 2)+H(D) and Ne(3 P 0)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(3 P 2)+H(D) spectra is due to the2 Σ potential. 相似文献
22.
23.
24.
Constantin Bu?e Dhaou Lassoued Thanh Lan Nguyen Olivia Saierli 《Integral Equations and Operator Theory》2012,74(3):345-362
Let u μ, x, s (., 0) be the solution of the following well-posed inhomogeneous Cauchy Problem on a complex Banach space X $$\left \{\begin{array}{ll}\dot{u}(t) = A(t)u(t) + e^{i\mu t}x, \quad t > s \\ u(s) = 0. \end{array} \right.$$ Here, x is a vector in X,?μ is a real number, q is a positive real number and A(·) is a q-periodic linear operator valued function. Under some natural assumptions on the evolution family ${\mathcal{U} = \{U(t, s): t \geq s\}}$ generated by the family {A(t)}, we prove that if for each?μ, each s?≥ 0 and every x the solution u μ, x, s (·, 0) is bounded on R + by a positive constant, depending only on x, then the family ${\mathcal{U}}$ is uniformly exponentially stable. The approach is based on the theory of evolution semigroups. 相似文献
25.
阐述基于Mie散射理论和激光技术而研制的云粒子探测仪的相关问题。利用m量级的小孔光阑模拟感应区域的散射光,并对系统的探测敏感区域面积进行测定;通过使用不同直径的标准粒子对系统进行标定,得到可靠的响应曲线,用于定量测量云粒子尺度谱及粒子数密度。在进行了一系列实验室内的实验之后,将仪器装载在飞机上进行穿云飞行测量实验,表明了该仪器在飞行过程中工作正常、稳定,并且能够即时地显示采样区内云粒子尺度谱分布和数浓度;通过分析探测得到的数据,并与云粒子谱分布进行比较,确认了探测数据有效可靠,反映了该仪器具有良好的测云能力。 相似文献
26.
Transport properties of La0.8Ba0.2MnO3 thin films deposited by the sol–gel method were investigated. It has been found that resistivity plateaus occurred in the ρ–T curves after application of a dc bias current over a critical value. A current of 200 μA could induce a huge resistance variation ∼1200% in these La0.8Ba0.2MnO3 films near room temperature, demonstrating a colossal electroresistance effect. Such strange transport behavior suggests the formation of conductive filaments and that the multi-phase coexistence is sensitive to external stimuli. This phenomenon may find applications in sensing and logic devices. 相似文献
27.
{Well-posedness of degenerate differential equations with infinite delay in Holder continuous function spaces 下载免费PDF全文
Using operator-valued $\dot{C}^\alpha$-Fourier multiplier results on vector- valued H\"older continuous function spaces, we give a characterization for the $C^\alpha$-well-posedness of the first order degenerate differential equations with infinite delay $(Mu)"(t) = Au(t) + \int_{-\infty}^t a(t-s)Au(s)ds + f(t)$ ($t\in\R$), where $A, M$ are closed operators on a Banach space $X$ such that $D(A)\cap D(M)\neq \{0\}$, $a\in L^1_{\rm{loc}}(\R_+)\cap L^1(\mathbb{R}_+; t^\alpha dt)$. 相似文献
28.
Let Q G denote the signless Laplacian matrix of a graph G. An eigenvalue μ of Q G is said to be a main Q-eigenvalue of G if μ has an eigenvector which is not orthogonal to an all-ones vector e. We give some basic properties of main Q-eigenvalues. For a graph G of order n, G is called Q-controllable if G has n distinct main Q-eigenvalues. We show that a graph H is generalized Q-cospectral with a Q-controllable G if and only if H is Q-controllable and there exists a unique rational orthogonal matrix R such that R e = e, Q H = R ? Q G R. 相似文献
29.
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
30.