全文获取类型
收费全文 | 189738篇 |
免费 | 13998篇 |
国内免费 | 7618篇 |
专业分类
化学 | 114096篇 |
晶体学 | 1916篇 |
力学 | 9414篇 |
综合类 | 315篇 |
数学 | 20031篇 |
物理学 | 65582篇 |
出版年
2022年 | 1826篇 |
2021年 | 2728篇 |
2020年 | 3676篇 |
2019年 | 3417篇 |
2018年 | 3054篇 |
2017年 | 2803篇 |
2016年 | 4665篇 |
2015年 | 4254篇 |
2014年 | 5213篇 |
2013年 | 9822篇 |
2012年 | 9777篇 |
2011年 | 10902篇 |
2010年 | 7078篇 |
2009年 | 6661篇 |
2008年 | 8373篇 |
2007年 | 7951篇 |
2006年 | 7641篇 |
2005年 | 6940篇 |
2004年 | 5725篇 |
2003年 | 4881篇 |
2002年 | 4333篇 |
2001年 | 4679篇 |
2000年 | 3660篇 |
1999年 | 3361篇 |
1998年 | 2833篇 |
1997年 | 2922篇 |
1996年 | 2866篇 |
1995年 | 2719篇 |
1994年 | 2388篇 |
1993年 | 2203篇 |
1992年 | 2348篇 |
1991年 | 2224篇 |
1990年 | 2094篇 |
1989年 | 1987篇 |
1988年 | 1938篇 |
1987年 | 1880篇 |
1986年 | 1769篇 |
1985年 | 2285篇 |
1984年 | 2359篇 |
1983年 | 1941篇 |
1982年 | 2236篇 |
1981年 | 2051篇 |
1980年 | 2087篇 |
1979年 | 2060篇 |
1978年 | 2178篇 |
1977年 | 2082篇 |
1976年 | 2102篇 |
1975年 | 2044篇 |
1974年 | 1872篇 |
1973年 | 2107篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
Nonlinear Dynamics - In this paper, a (2+1)-dimensional Caudrey–Dodd–Gibbon–Kotera–Sawada system is investigated in fluid mechanics via the symbolic computation. With the... 相似文献
2.
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
3.
Mathematical Programming - Scenario generation is the construction of a discrete random vector to represent parameters of uncertain values in a stochastic program. Most approaches to scenario... 相似文献
4.
Liu Chongyang Gong Zhaohua Teo Kok Lay Wang Song 《Journal of Optimization Theory and Applications》2022,193(1-3):856-876
Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to... 相似文献
5.
Xin Liu Lili Chen Yanfeng Zhao Xianhua Song 《Mathematical Methods in the Applied Sciences》2022,45(1):77-92
In this paper, the problem of the uniform stability for a class of fuzzy fractional-order genetic regulatory networks with random discrete delays, distributed delays, and parameter uncertainties is studied. Although there is a portion of literature on using fixed point theorems to study the stability of fractional neural networks, most of them required the fractional order to be in . However, the case of the fractional-order belonging to has not been discussed. To solve it, this work proposes a novel idea of using fixed point theory to study the stability of fuzzy (0,1) order neural networks, the problem of the uniqueness of the solution of the considered genetic regulatory networks is resolved, and a novel sufficient condition to guarantee the uniform stability of above genetic regulatory networks is also derived. Eventually, an example is given to demonstrate that the obtained result is effective. 相似文献
6.
7.
Maschler Tobias Strmer-Stephan Bastian Morhard Jrg Stegmaier Thomas Tilebein Meike Griepentrog Hans W. 《Annals of Operations Research》2022,314(2):577-600
Annals of Operations Research - Selecting a vegetation layer design goes along with determining its future irrigation need. Therefore, it is essential to take a design decision that is minimising... 相似文献
8.
以过渡金属为催化衬底的化学气相沉积法(Chemical Vapor Deposition,CVD)已经可以制备与机械剥离样品相媲美的石墨烯,是实现石墨烯工业应用的关键技术之一。原子尺度理论研究能够帮助我们深刻理解石墨烯生长机理,为实验现象提供合理的解释,并有可能成为将来实验设计的理论指导。本文从理论计算的角度,总结了各种金属衬底在石墨烯CVD生长过程中的各种作用与相应的机理,包括在催化碳源裂解、降低石墨烯成核密度等,催化加快石墨烯快速生长,修复石墨烯生长过程中产生的缺陷,控制外延生长石墨烯的晶格取向,以及在降温过程中石墨烯褶皱与金属表面台阶束的形成过程等。在本文最后,我们对当前石墨烯生长领域中亟需解决的理论问题进行了深入探讨与展望。 相似文献
9.
Atopic dermatitis is characterized by leukocyte migration into the skin dermis and typically driven by excessive chemokine production at the site of inflammation. Conventional topical formulations such as gels, creams, and ointments are insufficient for this treatment because of low penetration of drug molecules into the targeted skin tissues. Herein, using a simple, green, sustainable strategy, we have developed novel primary zein nanoparticles embedded in curcumin (Cur) and coated with silk sericin (ZHSCs) for the topical delivery of Cur to penetrate into the dermis and exercise anti-dermatitis effects on the lesion with minimal side-effects. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that ZHSCs facilitate the penetration of Cur across the epidermis layer of skin to reach deep-seated sites. Notably, ZHSCs = 1:0.25 (zein-to-silk sericin mass ratios of 1:0.25) markedly elevated the skin permeability and cumulative turnover of Cur transferred, which were provided a greater than a 3.8-fold increase relative to free Cur. The special nanoparticles of ZHS = 1:0.25 possessed the deepest localization depth and experience a transition of the particle structure and core-shell separation after penetrating into the dermis of skin. In a cell model of dermatitis induced by tumor necrosis factor α/interferon γ co-stimulation, compared with free Cur, Cur-loaded ZHS nanoparticles down-regulated the generation of inflammatory cytokines and chemokines in keratinocytes through suppression of the nuclear translocation of NF-κBp65 and hence exerted an anti-dermatitis effect. This strategy may provide new avenues and direction for the demanding issues of valid topical delivery systems. 相似文献
10.
Gladkov L. L. Klenitsky D. V. Vershilovskaya I. V. Maes W. Kruk M. M. 《Journal of Applied Spectroscopy》2022,89(3):426-432
Journal of Applied Spectroscopy - The aromaticity in the lowest triplet T1-state of NH-tautomers of corrole free bases with different peripheral substitution architecture was investigated using... 相似文献