全文获取类型
收费全文 | 95217篇 |
免费 | 7700篇 |
国内免费 | 12022篇 |
专业分类
化学 | 70022篇 |
晶体学 | 2626篇 |
力学 | 4183篇 |
综合类 | 607篇 |
数学 | 17010篇 |
物理学 | 20491篇 |
出版年
2024年 | 200篇 |
2023年 | 1101篇 |
2022年 | 2058篇 |
2021年 | 2010篇 |
2020年 | 2675篇 |
2019年 | 2651篇 |
2018年 | 2338篇 |
2017年 | 2635篇 |
2016年 | 3253篇 |
2015年 | 3187篇 |
2014年 | 3998篇 |
2013年 | 6560篇 |
2012年 | 5940篇 |
2011年 | 5736篇 |
2010年 | 4688篇 |
2009年 | 5921篇 |
2008年 | 6131篇 |
2007年 | 6118篇 |
2006年 | 5421篇 |
2005年 | 4819篇 |
2004年 | 4800篇 |
2003年 | 3985篇 |
2002年 | 4748篇 |
2001年 | 2794篇 |
2000年 | 2631篇 |
1999年 | 2279篇 |
1998年 | 1931篇 |
1997年 | 1610篇 |
1996年 | 1735篇 |
1995年 | 1575篇 |
1994年 | 1452篇 |
1993年 | 1072篇 |
1992年 | 1076篇 |
1991年 | 699篇 |
1990年 | 560篇 |
1989年 | 514篇 |
1988年 | 461篇 |
1987年 | 370篇 |
1986年 | 312篇 |
1985年 | 368篇 |
1984年 | 306篇 |
1983年 | 190篇 |
1982年 | 270篇 |
1981年 | 313篇 |
1980年 | 255篇 |
1979年 | 225篇 |
1978年 | 199篇 |
1977年 | 190篇 |
1976年 | 162篇 |
1973年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
C. Maurel 《Surface science》2006,600(2):442-447
Light emitted in the tunneling junction of a scanning tunneling microscope has been used to establish the electrical characteristics of nanojunctions made of Au islands deposited on flat MoS2 surfaces. It is shown that these characteristics are those of rectifying contacts when the gold islands are isolated and that they evolve toward those of ohmic contacts when the island density increases. It is observed that the rectifying behavior also evolves over time as on infinite metal/semiconductor contacts. Using the STM tip, single gold islands can be manipulated on the MoS2 surface so that their electrical behavior can be changed depending on their position with regard to the other islands. 相似文献
22.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
23.
本文使用激光诱导瞬态吸收光谱装置,研究了C60激发三重态在乙腈/甲苯混合溶剂中的光物理性质,得到了3C60的激发态寿命、自猝灭速率常数和时间分辩的瞬态吸收光谱.此外,实验中引入了哌嗪作为激发三重态猝灭剂.我们发现哌嗪能有效的猝灭3C60,猝灭速率常数kq接近扩散控制极限.改变混合溶剂的比例,相应的猝灭速率常数值也发生变化,即kq随混合溶剂极性的增加而增加,随溶剂粘度的增加而减小.稳态光解实验反映了反应物向产物转化过程中在紫外-可见波段吸收强度的变化. 相似文献
24.
基于校园网的实验管理系统的设计 总被引:2,自引:1,他引:1
主要讨论了应用实验室管理系统的必要性,并从用户需求分析、系统总体设计、功能模块的设计等方面对B/S实验室管理系统的开发进行了详细的阐述。 相似文献
25.
Nicolas Bergeron 《Mathematische Zeitschrift》2002,241(1):101-125
Let M be an arithmetic hyperbolic manifold and be a codimension 1 geodesic cycle. In this paper, we study the asymptotic growth of the -norm of the lifts of F in the congruence tower above M. We obtain an explicit value for the growth rate of this norm. In particular, we provide a new proof of a celebrated result
of Millson [Mi] on the homology of the arithmetic hyperbolic manifolds. The method is quite general and gives a new way of
getting non zero homology classes in certain locally symmetric spaces.
Received: 20 April 2001; in final form: 26 September 2001 / Published online: 28 February 2002 相似文献
26.
Chuanming Zong 《Monatshefte für Mathematik》2002,134(3):247-255
In this article we study the simultaneous packing and covering constants of two-dimensional centrally symmetric convex domains.
Besides an identity result between translative case and lattice case and a general upper bound, exact values for some special
domains are determined. Similar to Mahler and Reinhardt’s result about packing densities, we show that the simultaneous packing
and covering constant of an octagon is larger than that of a circle.
(Received 17 January 2001; in revised form 13 July 2001) 相似文献
27.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity. 相似文献
28.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations. 相似文献
29.
V. V. Kozlov 《Functional Analysis and Its Applications》2005,39(4):271-283
We discuss the symplectic geometry of linear Hamiltonian systems with nondegenerate Hamiltonians. These systems can be reduced to linear second-order differential equations characteristic of linear oscillation theory. This reduction is related to the problem on the signatures of restrictions of quadratic forms to Lagrangian planes. We study vortex symplectic planes invariant with respect to linear Hamiltonian systems. These planes are determined by the solutions of quadratic matrix equations of a special form. New conditions for gyroscopic stabilization are found. 相似文献
30.