全文获取类型
收费全文 | 20835篇 |
免费 | 2794篇 |
国内免费 | 2165篇 |
专业分类
化学 | 15908篇 |
晶体学 | 301篇 |
力学 | 1057篇 |
综合类 | 187篇 |
数学 | 1985篇 |
物理学 | 6356篇 |
出版年
2024年 | 15篇 |
2023年 | 270篇 |
2022年 | 342篇 |
2021年 | 577篇 |
2020年 | 680篇 |
2019年 | 677篇 |
2018年 | 513篇 |
2017年 | 532篇 |
2016年 | 908篇 |
2015年 | 851篇 |
2014年 | 1070篇 |
2013年 | 1496篇 |
2012年 | 1845篇 |
2011年 | 1911篇 |
2010年 | 1353篇 |
2009年 | 1174篇 |
2008年 | 1433篇 |
2007年 | 1221篇 |
2006年 | 1195篇 |
2005年 | 1110篇 |
2004年 | 890篇 |
2003年 | 777篇 |
2002年 | 855篇 |
2001年 | 569篇 |
2000年 | 496篇 |
1999年 | 432篇 |
1998年 | 315篇 |
1997年 | 273篇 |
1996年 | 279篇 |
1995年 | 254篇 |
1994年 | 210篇 |
1993年 | 196篇 |
1992年 | 175篇 |
1991年 | 150篇 |
1990年 | 133篇 |
1989年 | 107篇 |
1988年 | 95篇 |
1987年 | 64篇 |
1986年 | 63篇 |
1985年 | 77篇 |
1984年 | 39篇 |
1983年 | 36篇 |
1982年 | 28篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1974年 | 8篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 782 毫秒
991.
Carbon supports modified with well dispersed anatase TiO2 (C–Ti-X; X (0.25, 0.5, 0.75, and 1.0) represents mass ratio of Ti precursor to carbon) were synthesized with various Ti loadings and used to support Pd catalysts for oxygen reduction. The anatase nanoparticles increased in size with increasing Ti loading. Pd dispersion improved with increasing Ti loading up to the C–Ti-0.75, which resulted in the best catalytic activity. Although the Pd dispersion was lowest on the C–Ti-1.0, it showed better catalytic performance than the catalysts supported on C–Ti-0.25 and C–Ti-0.5. At 0.8 V (vs. RHE), the best catalytic activity achieved was respectively 2.7 and 2.7 times the mass and specific activities of Pd supported on un-modified carbon. The interaction between Pd and highly dispersed TiO2 is believed to improve the catalytic activity of Pd supported on TiO2-modified carbons. 相似文献
992.
Jin Liu Xianxue Wang Han Guo Xiaokang Shi Xiaoyu Ren Guosheng Huang 《Tetrahedron》2012,68(5):1560-1565
A novel NH4OAc/CuBr(PPh3)3-induced intermolecular Pummerer-type reaction between free (NH)-indoles and dimethylsulfoxide is first reported, which offers the 3-methylthiomethyl substituted indoles conveniently and efficiently. 相似文献
993.
Da Quan Zhang Xing Jin Bin Xie Hyung Goun Joo Li Xin Gao Kang Yong Lee 《Surface and interface analysis : SIA》2012,44(1):78-83
The corrosion inhibition of ammonium heltamolybdate (AH) and calcium gluconate (CG) for AA6061 alloy in 3% NaCl solution was investigated by the electrochemical measurements. It indicates that AH inhibits the corrosion of AA6061 alloy and acts as an anodic inhibitor. Maximum inhibition efficiency reaches 74.3% at the concentration of 1 × 10?4 mol.l?1 AH. The results of the electrochemical studies reveal AH is physically adsorbed on the AA6061 alloy surface and the adsorption follows Langmuir isotherm. The combination of AH and CG enhances the inhibition efficiency to 95.9%. The enhanced inhibition is attributed to the promotion of AH adsorption by CG. The mixture of AH and CG is a mixed‐type inhibitor and renders the corrosion potential to more positive values. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
994.
995.
Jun Dai Lin Li LiPing He KangCheng Ruan HuiBin Lu KuiJuan Jin GuoZhen Yang 《中国科学:物理学 力学 天文学(英文版)》2014,57(11):2039-2042
In this work, we parallelly detected the specific binding between microarray targets including 12 different kinds of proteins and the probe solution containing five corresponding antibodies and quantitatively analyzed the interactions between CDH13 and solution phase anti-CDH13 at six different probe concentrations by oblique-incidence reflectivity difference (OIRD) method in label-free format. The detection sensitivity reached 10 ng/mL. The experimental results indicate that the OIRD method is a promising and competing technique not only in research work but also in clinic. 相似文献
996.
Dr. Zhen Lei Zong‐Jie Guan Dr. Xiao‐Li Pei Shang‐Fu Yuan Xian‐Kai Wan Jin‐Yuan Zhang Prof.Dr. Quan‐Ming Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11156-11160
A red–near‐IR dual‐emissive nanocluster with the composition [Au10Ag2(2‐py?C≡C)3(dppy)6](BF4)5 ( 1 ; 2‐py?C≡C is 2‐pyridylethynyl, dppy=2‐pyridyldiphenylphosphine) has been synthesized. Single‐crystal X‐ray structural analysis reveals that 1 has a trigonal bipyramidal Au10Ag2 core that contains a planar Au4(2‐py?C≡C)3 unit sandwiched by two Au3Ag(dppy)3 motifs. Cluster 1 shows intense red–NIR dual emission in solution. The visible emission originates from metal‐to‐ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2‐pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time‐dependent density functional theory (TD‐DFT) calculation. 相似文献
997.
998.
Distributed wireless quantum communication networks with partially entangled pairs*Distributed wireless quantum communication networks with partially entangled pairs*Distributed wireless quantum communication networks with partially entangled pairs*Distributed wireless quantum communication networks with partially entangled pairs 下载免费PDF全文
Wireless quantum communication networks transfer quantum state by teleportation. Existing research focuses on maximal entangled pairs. In this paper, we analyse the distributed wireless quantum communication networks with partially entangled pairs. A quantum routing scheme with multi-hop teleportation is proposed. With the proposed scheme, is not necessary for the quantum path to be consistent with the classical path. The quantum path and its associated classical path are established in a distributed way. Direct multi-hop teleportation is conducted on the selected path to transfer a quantum state from the source to the destination. Based on the feature of multi-hop teleportation using partially entangled pairs, if the node number of the quantum path is even, the destination node will add another teleportation at itself. We simulated the performance of distributed wireless quantum communication networks with a partially entangled state. The probability of transferring the quantum state successfully is statistically analyzed. Our work shows that multi-hop teleportation on distributed wireless quantum networks with partially entangled pairs is feasible, 相似文献
999.
Xia Caifen Fu Boqiao Jin Jian-Cheng 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12561-12567
Journal of Thermal Analysis and Calorimetry - Nd compounds have been widely used for the promotion of growth of plant due to their excellent biophysical and biochemical properties. Mitochondria are... 相似文献
1000.