全文获取类型
收费全文 | 221860篇 |
免费 | 28201篇 |
国内免费 | 19290篇 |
专业分类
化学 | 102864篇 |
晶体学 | 1711篇 |
力学 | 10017篇 |
综合类 | 1046篇 |
数学 | 18618篇 |
物理学 | 60040篇 |
综合类 | 75055篇 |
出版年
2024年 | 904篇 |
2023年 | 3971篇 |
2022年 | 6405篇 |
2021年 | 7023篇 |
2020年 | 6879篇 |
2019年 | 5996篇 |
2018年 | 5682篇 |
2017年 | 5348篇 |
2016年 | 7929篇 |
2015年 | 8408篇 |
2014年 | 10907篇 |
2013年 | 13228篇 |
2012年 | 15735篇 |
2011年 | 15985篇 |
2010年 | 11588篇 |
2009年 | 11593篇 |
2008年 | 12593篇 |
2007年 | 11568篇 |
2006年 | 10531篇 |
2005年 | 9120篇 |
2004年 | 7241篇 |
2003年 | 5905篇 |
2002年 | 5704篇 |
2001年 | 5246篇 |
2000年 | 5138篇 |
1999年 | 7138篇 |
1998年 | 6357篇 |
1997年 | 6299篇 |
1996年 | 6095篇 |
1995年 | 5301篇 |
1994年 | 4771篇 |
1993年 | 4001篇 |
1992年 | 3672篇 |
1991年 | 3255篇 |
1990年 | 2840篇 |
1989年 | 2413篇 |
1988年 | 1989篇 |
1987年 | 1437篇 |
1986年 | 975篇 |
1985年 | 669篇 |
1984年 | 396篇 |
1983年 | 285篇 |
1982年 | 229篇 |
1981年 | 144篇 |
1980年 | 105篇 |
1979年 | 62篇 |
1978年 | 30篇 |
1976年 | 30篇 |
1975年 | 33篇 |
1957年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point (CMP) ... 相似文献
32.
Tuning the Basicity of Cyano‐Containing Ionic Liquids to Improve SO2 Capture through Cyano–Sulfur Interactions 下载免费PDF全文
Dr. Guokai Cui Fengtao Zhang Xiuyuan Zhou Prof. Haoran Li Prof. Jianji Wang Prof. Congmin Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5632-5639
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture. 相似文献
33.
34.
35.
Jia Tian-Cong Guo Jin-Tao Wang Zhen Zhu Xiao-Shan Zhang Qian-Xin Chen Ping Yao Kun Lv Wen-Ying Liu Guo-Guang 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(3):823-829
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of... 相似文献
36.
37.
Through molecular dynamics(MD)simulation,the dependencies of temperature,grain size and strain rate on the mechanical properties were studied.The simulation results demonstrated that the strain rate from 0.05 to 2 ns~(–1 )affected the Young’s modulus of nickel nanowires slightly,whereas the yield stress increased.The Young’s modulus decreased approximately linearly;however,the yield stress firstly increased and subsequently dropped as the temperature increased.The Young’s modulus and yield stress increased as the mean grain size increased from 2.66 to6.72 nm.Moreover,certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension.Certain phenomena such as the formation of twin structures,which were found in nanowires with larger grain size at higher strain rate and lower temperature,as well as the movement of grain boundaries and dislocation,were detected and discussed in detail.The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size.However,for larger grain size,the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire. 相似文献
38.
Random walks are a standard tool for modeling the spreading process in social and biological systems.But in the face of large-scale networks,to achieve convergence,iterative calculation of the transition matrix in random walk methods consumes a lot of time.In this paper,we propose a three-stage hierarchical community detection algorithm based on Partial Matrix Approximation Convergence(PMAC) using random walks.First,this algorithm identifies the initial core nodes in a network by classical measurement and then utilizes the error function of the partial transition matrix convergence of the core nodes to determine the number of random walks steps.As such,the PMAC of the core nodes replaces the final convergence of all the nodes in the whole matrix.Finally,based on the approximation convergence transition matrix,we cluster the communities around core nodes and use a closeness index to merge two communities.By recursively repeating the process,a dendrogram of the communities is eventually constructed.We validated the performance of the PMAC by comparing its results with those of two representative methods for three real-world networks with different scales. 相似文献
39.
40.