全文获取类型
收费全文 | 70490篇 |
免费 | 12548篇 |
国内免费 | 7176篇 |
专业分类
化学 | 48945篇 |
晶体学 | 624篇 |
力学 | 4634篇 |
综合类 | 310篇 |
数学 | 8166篇 |
物理学 | 27535篇 |
出版年
2024年 | 76篇 |
2023年 | 1536篇 |
2022年 | 1583篇 |
2021年 | 2329篇 |
2020年 | 3063篇 |
2019年 | 2842篇 |
2018年 | 2470篇 |
2017年 | 2262篇 |
2016年 | 3455篇 |
2015年 | 3307篇 |
2014年 | 3955篇 |
2013年 | 5142篇 |
2012年 | 6580篇 |
2011年 | 6724篇 |
2010年 | 4467篇 |
2009年 | 4252篇 |
2008年 | 4591篇 |
2007年 | 4107篇 |
2006年 | 3754篇 |
2005年 | 3130篇 |
2004年 | 2421篇 |
2003年 | 1887篇 |
2002年 | 1652篇 |
2001年 | 1413篇 |
2000年 | 1291篇 |
1999年 | 1485篇 |
1998年 | 1276篇 |
1997年 | 1254篇 |
1996年 | 1262篇 |
1995年 | 1040篇 |
1994年 | 922篇 |
1993年 | 762篇 |
1992年 | 676篇 |
1991年 | 580篇 |
1990年 | 503篇 |
1989年 | 381篇 |
1988年 | 332篇 |
1987年 | 274篇 |
1986年 | 250篇 |
1985年 | 204篇 |
1984年 | 143篇 |
1983年 | 102篇 |
1982年 | 79篇 |
1981年 | 67篇 |
1980年 | 66篇 |
1979年 | 32篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 30篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 320 毫秒
71.
通过改装多旋翼无人机(UAV)和搭载各类载荷以及联合地基观测设备对大柴旦地区大气、环境以及气溶胶参数进行测量。利用获得的数据资料,对该地区近地层气溶胶粒子数浓度(即单位体积空气中气溶胶粒子的数目)、消光系数以及气象要素等特征进行了分析。结果表明,在大柴旦地区,近地层气溶胶粒子数浓度日变化显著,呈现双峰形态,气溶胶粒子数浓度的变化范围为75~220 cm-3,消光系数的变化范围为0.004~0.038 km-1;当风速小于6 m/s时,气溶胶粒子数浓度与风速呈负相关关系;当风速大于6 m/s时,二者呈正相关关系;相对湿度对气溶胶粒子的影响较小,这可能是由于该地区以沙尘型气溶胶为主,吸湿性较弱。本研究基于多旋翼无人机探测平台,可以有效地获得近地层精细化大气、环境结构,有助于研究人员了解该地区气溶胶的结构、变化特征以及建立气溶胶模式,同时也为气溶胶及大气环境参数探测方法提供了技术支撑及思路拓展。 相似文献
72.
Liu Wei Liu Haiding Wang Chunguang Wang Dongzhe 《Journal of Solid State Electrochemistry》2022,26(6):1409-1419
Journal of Solid State Electrochemistry - The maximum pit volume is a significant parameter to evaluate the pitting extent on metal materials, which could be associated with the charge transfer... 相似文献
73.
A Lower Bound Sequence for the Minimum Eigenvalue of Hadamard Product of an M-Matrix and its Inverse
Czechoslovak Mathematical Journal - We propose a lower bound sequence for the minimum eigenvalue of Hadamard product of an M-matrix and its inverse, in terms of an S-type eigenvalues inclusion set... 相似文献
74.
Luo Dajuan Liu Bingqian Gao Rong Su Lixia Su Yonghuan 《Journal of Solid State Electrochemistry》2022,26(3):749-759
Journal of Solid State Electrochemistry - Cortisol, a steroid hormone, has been confirmed as a kind of biomarker that reflects the stress response of psychobiology and related adverse health... 相似文献
75.
Acta Mathematicae Applicatae Sinica, English Series - In this paper, we consider the statistical inferences in a partially linear model when the model error follows an autoregressive process. A... 相似文献
76.
Cao Hongmei Deng Shenzhen Tie Zhiwei Tian Jinlei Liu Lili Niu Zhiqiang 《中国科学:化学(英文版)》2022,65(9):1725-1732
Science China Chemistry - Synchronously reducing/self-assembling strategy on Zn substrate was designed to fabricate large-area cation-doped hydrated V2O5/multi-walled carbon nanotube (D-HVO/MWCNT)... 相似文献
77.
An oriented tetrahedron defined on four vertices is a set of four cyclic triples with the property that any ordered pair of vertices is contained in exactly one of the cyclic triples. A tetrahedral quadruple system of order with index , denoted by , is a pair , where is an ‐set and is a set of oriented tetrahedra (blocks) such that every cyclic triple on is contained in exactly members of . A is pure if there do not exist two blocks with the same vertex set. When , the spectrum of a pure TQS has been completely determined by Ji. In this paper, we show that there exists a pure if and only if and . A corollary is that a simple also exists if and only if and . 相似文献
78.
In recent years, clapping synchronization between individuals has been widely studied as one of the typical synchronization phenomena. In this paper, we aim to reveal the synchronization mechanism of clapping interactions by observing two individuals’ clapping rhythms in a series of experiments. We find that the two synchronizing clapping rhythm series exhibit long-range cross-correlations(LRCCs);that is, the interaction of clapping rhythms can be seen as a strong-anticipation process. Previous studies have demonstrated that the interactions in local timescales or global matching in statistical structures of fluctuation in long timescales can be sources of the strong-anticipation process. However, the origin of the strong anticipation process often appears elusive in many complex systems. Here, we find that the clapping synchronization process may result from the local interaction between two clapping individuals and may result from the more global coordination between two clapping individuals. We introduce two stochastic models for mutually interacting clapping individuals that generate the LRCCs and prove theoretically that the generation of clapping synchronization process needs to consider both local interaction and global matching. This study provides a statistical framework for studying the internal synchronization mechanism of other complex systems. Our theoretical model can also be applied to study the dynamics of other complex systems with the LRCCs, including finance, transportation, and climate. 相似文献
79.
The purpose of this article is to investigate high‐order numerical approximations of scalar conservation laws with nonlocal viscous term. The viscous term is given in the form of convolution in space variable. With the help of the characteristic of viscous term, we design a semidiscrete local discontinuous Galerkin (LDG) method to solve the nonlocal model. We prove stability and convergence of semidiscrete LDG method in L2 norm. The theoretical analysis reveals that the present numerical scheme is stable with optimal convergence order for the linear case, and it is stable with sub‐optimal convergence order for nonlinear case. To demonstrate the validity and accuracy of our scheme, we test the Burgers equation with two typical nonlocal fractional viscous terms. The numerical results show the convergence order accuracy in space for both linear and nonlinear cases. Some numerical simulations are provided to show the robustness and effectiveness of the present numerical scheme. 相似文献
80.
Liu Cungen Gao Chuang Liu Xiaoping Wang Huanqing Zhou Yucheng 《Nonlinear dynamics》2021,104(4):3655-3670
Nonlinear Dynamics - This paper is devoted to the adaptive finite-time prescribed performance control (FTPPC) for stochastic nonlinear systems with unknown virtual control coefficients (UVCCs),... 相似文献