首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   26555篇
  免费   2978篇
  国内免费   2769篇
化学   13392篇
晶体学   277篇
力学   964篇
综合类   187篇
数学   1717篇
物理学   5924篇
综合类   9841篇
  2024年   73篇
  2023年   338篇
  2022年   684篇
  2021年   703篇
  2020年   720篇
  2019年   685篇
  2018年   585篇
  2017年   605篇
  2016年   934篇
  2015年   1043篇
  2014年   1286篇
  2013年   1632篇
  2012年   1927篇
  2011年   1958篇
  2010年   1528篇
  2009年   1419篇
  2008年   1651篇
  2007年   1426篇
  2006年   1384篇
  2005年   1338篇
  2004年   1082篇
  2003年   1009篇
  2002年   1270篇
  2001年   1019篇
  2000年   795篇
  1999年   814篇
  1998年   535篇
  1997年   525篇
  1996年   505篇
  1995年   445篇
  1994年   390篇
  1993年   359篇
  1992年   315篇
  1991年   266篇
  1990年   241篇
  1989年   207篇
  1988年   192篇
  1987年   114篇
  1986年   89篇
  1985年   71篇
  1984年   37篇
  1983年   29篇
  1982年   21篇
  1981年   20篇
  1980年   9篇
  1979年   7篇
  1974年   2篇
  1971年   2篇
  1957年   6篇
  1936年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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   
992.
993.
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   
994.
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   
995.
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   
996.
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   
997.
998.
999.
1000.
Novel heterogeneous tungsten species in mesoporous silica SBA‐16 catalysts based on ship‐in‐a‐bottle methodology are originally reported for oxidizing cyclopentene (CPE) to glutaric acid (GAC) using hydrogen peroxide (H2O2). For all W‐SBA‐16 catalysts, isolated tungsten species and octahedrally coordinated tungsten oxide species are observed while WO3 crystallites are detected for the W‐SBA‐16 catalysts with Si/ W = 5, 10, and 20. The specific surface areas and the corresponding total pore volumes decrease significantly as increasing amounts of tungsten incorporated into the pores of SBA‐16. Using tungsten‐substituted mesoporous SBA‐16 heterogeneous catalysts, high yield of GAC (55%) is achieved with low tungsten loading (for Si/W = 30, ~13 wt%) for oxidation of CPE. The W‐SBA‐16 catalysts with Si/W = 30 can be reused five times without dramatic deactivation. In fact, low catalytic activity provided by bulk WO3 implies that the highly distributed tungsten species in SBA‐16 and the steric confinement effect of SBA‐16 are key elements for the outstanding catalytic performance.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号