全文获取类型
收费全文 | 39570篇 |
免费 | 2439篇 |
国内免费 | 1935篇 |
专业分类
化学 | 22730篇 |
晶体学 | 206篇 |
力学 | 3823篇 |
综合类 | 550篇 |
数学 | 8061篇 |
物理学 | 8574篇 |
出版年
2024年 | 32篇 |
2023年 | 353篇 |
2022年 | 608篇 |
2021年 | 968篇 |
2020年 | 1005篇 |
2019年 | 959篇 |
2018年 | 864篇 |
2017年 | 1106篇 |
2016年 | 1493篇 |
2015年 | 1115篇 |
2014年 | 1589篇 |
2013年 | 2814篇 |
2012年 | 2396篇 |
2011年 | 2073篇 |
2010年 | 1783篇 |
2009年 | 2315篇 |
2008年 | 2271篇 |
2007年 | 2568篇 |
2006年 | 2136篇 |
2005年 | 1944篇 |
2004年 | 1881篇 |
2003年 | 1556篇 |
2002年 | 1165篇 |
2001年 | 939篇 |
2000年 | 896篇 |
1999年 | 771篇 |
1998年 | 753篇 |
1997年 | 698篇 |
1996年 | 619篇 |
1995年 | 648篇 |
1994年 | 565篇 |
1993年 | 475篇 |
1992年 | 440篇 |
1991年 | 380篇 |
1990年 | 342篇 |
1989年 | 225篇 |
1988年 | 227篇 |
1987年 | 138篇 |
1986年 | 125篇 |
1985年 | 141篇 |
1984年 | 114篇 |
1983年 | 58篇 |
1982年 | 96篇 |
1981年 | 55篇 |
1980年 | 46篇 |
1979年 | 76篇 |
1978年 | 34篇 |
1977年 | 16篇 |
1976年 | 22篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Qian Jin Luo 《数学学报(英文版)》2020,36(6):711-722
Let B be the unit disc in R~2, H be the completion of C_0∞(B) under the norm■ .By the method of blow-up analysis and an argument of rearrangement with respect to the standard hyperbolic metric ■, we prove that, for any fixed■ ,the supremum■ .This is an analog of early results of Lu–Yang(Discrete Contin. Dyn. Syst., 2009) and Yang(Trans.Amer. Math. Soc., 2007), and extends those of Wang–Ye(Adv. Math., 2012) and Yang–Zhu(Ann.Global Anal. Geom., 2016). 相似文献
992.
Fanghua Lin 《数学研究通讯:英文版》2020,36(1):1-30
The first part of this article is an overview on some recent major developments in the field of analysis and partial different equations.It is a brief presentation given by the author at a round table discussion.The second part is a supplement of various details provided by several outstanding researchers on subjects. 相似文献
993.
G. Yu S. H. Jacobson N. Kiyavash 《Stochastics An International Journal of Probability and Stochastic Processes》2020,92(2):223-264
ABSTRACTWe provide an asymptotic analysis of multi-objective sequential stochastic assignment problems (MOSSAP). In MOSSAP, a fixed number of tasks arrive sequentially, with an n-dimensional value vector revealed upon arrival. Each task is assigned to one of a group of known workers immediately upon arrival, with the reward given by an n-dimensional product-form vector. The objective is to maximize each component of the expected reward vector. We provide expressions for the asymptotic expected reward per task for each component of the reward vector and compare the convergence rates for three classes of Pareto optimal policies. 相似文献
994.
995.
996.
拾取指定长度的半导体性碳纳米管对大规模制造碳纳米管场效应管具有重要意义.本文提出了一种利用原子力显微镜探针和钨针对碳纳米管进行可控长度拾取的方法并进行了碳纳米管导电性分析.在扫描电子显微镜下搭建微纳操作系统,针对切割操作过程中原子力显微镜探针、钨针和碳纳米管的接触情况进行了力学建模和拾取长度误差分析.建立了单根金属性碳纳米管、单根半导体性碳纳米管及碳纳米管束与钨针接触的电路模型,推导了接入不同性质碳纳米管后电路的电流电压特性方程.使用原子力显微镜探针对碳纳米管的空间位姿进行调整,控制钨针对碳纳米管上目标位置进行通电切割,同时获取切割电路中的电流电压数据.实验结果表明,本文提出的方法能够有效控制所拾取碳纳米管的长度,增加碳纳米管与原子力显微镜探针的水平接触长度能够减小碳纳米管形变导致的拾取长度误差,建立的电流电压特性方程能够用于分析碳纳米管的导电性. 相似文献
997.
998.
999.
Scott C. Hagen D. Michael Parrish ? 《International Journal of Computational Fluid Dynamics》2013,27(7):585-595
This paper presents an a posteriori approach to unstructured mesh generation via a localized truncation error analysis and applies it to the Western North Atlantic Tidal (WNAT) model domain. The WNAT model domain encompasses the Gulf of Mexico, the Caribbean Sea, and the North Atlantic Ocean east to the 60°W Meridian. Herein, we pay particular attention to the area surrounding the Bahamas. A bathymetric data set with fine resolution is employed in seven separate linear, harmonic simulations of shallow water tidal flow for seven different tidal-forcing constituents. Each set of simulation results is used to perform a truncation error analysis of a linear, harmonic form of the depth-averaged momentum equations for each of the seven different tidal-forcing frequencies. Truncation error is then driven to a more uniform, domain-wide value by solving for local node spacing requirements. The process is built upon successful research aiming to produce unstructured grids for large-scale domains that can be used in the accurate and efficient modeling of shallow water flow. The methodology described herein can also be transferred to other modeling applications. 相似文献
1000.
A study was conducted on the effect of atmospheric parameters,including temperature,wind speed,and relative humidity,on fine particulate mass concentrations measured in Jiading District of Shanghai,China, during the period from January 2009 to January 2010.A sensitivity analysis was applied to investigate the interaction between atmospheric parameters and particulate mass concentration.The experiment revealed that the concentration of particulates increased with particle size from 0.1 to 1.0μm,and decreased with the increase of particle size from 1.0 to 2.5μm.The effects of atmospheric parameters on fine mass concentrations were significantly particle size-dependent.The PM1.0-2.5 may come from the size increase of smaller particulates after moisture absorption.And the variation of concentrations of PM0.1-1.0 was mainly attributed to the accumulation of PM0.1.The ventilation index and dilution index were calculated on the basis of data collected in December 2009.A correlation analysis indicated that there was a significant relation between these two indexes and the particulate concentration by examining the three particle size ranges,0.0-0.1,0.1-1.0,and 1.0-2.5μm.The Spearman correlation coefficients that related the ventilation index to the concentration for the three particle size ranges were -0.45,-0.56 and -0.47, respectively,while the coefficients that related the dilution index to the concentration were -0.36,-0.42 and -0.45,respectively. 相似文献