全文获取类型
收费全文 | 22793篇 |
免费 | 2793篇 |
国内免费 | 2178篇 |
专业分类
化学 | 17593篇 |
晶体学 | 326篇 |
力学 | 1013篇 |
综合类 | 187篇 |
数学 | 2062篇 |
物理学 | 6583篇 |
出版年
2024年 | 26篇 |
2023年 | 274篇 |
2022年 | 438篇 |
2021年 | 571篇 |
2020年 | 669篇 |
2019年 | 710篇 |
2018年 | 524篇 |
2017年 | 530篇 |
2016年 | 889篇 |
2015年 | 849篇 |
2014年 | 1043篇 |
2013年 | 1540篇 |
2012年 | 1835篇 |
2011年 | 1980篇 |
2010年 | 1352篇 |
2009年 | 1228篇 |
2008年 | 1526篇 |
2007年 | 1337篇 |
2006年 | 1381篇 |
2005年 | 1279篇 |
2004年 | 1066篇 |
2003年 | 916篇 |
2002年 | 989篇 |
2001年 | 562篇 |
2000年 | 499篇 |
1999年 | 441篇 |
1998年 | 354篇 |
1997年 | 330篇 |
1996年 | 319篇 |
1995年 | 290篇 |
1994年 | 222篇 |
1993年 | 212篇 |
1992年 | 189篇 |
1991年 | 173篇 |
1990年 | 141篇 |
1989年 | 118篇 |
1988年 | 112篇 |
1987年 | 87篇 |
1986年 | 106篇 |
1985年 | 121篇 |
1984年 | 80篇 |
1983年 | 52篇 |
1982年 | 73篇 |
1981年 | 73篇 |
1980年 | 53篇 |
1979年 | 44篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
As stimulated Brillouin scattering (SBS) materials, solids have many advantages such as compactness, innoxiousness, and ease of handling. The SBS threshold and reflectivity of K8 glass, a solid material, are investigated. A SBS phase control experiment using K8 glass to achieve coherent beam combination is performed with a self-phase-control technique below the optical damage threshold. The experimental results show that the short-term phase has been stabilized well with λ/33.8 fluctuation during 256 shots (25.6 s), and that the long-term phase change with non-convective K8 glass is much slower than that with convective HT-70 liquid. 相似文献
992.
Wen-Bin Chen Gui-Yu Jin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):543-549
In this article, we incorporated the organic phosphorus group on to a triazolothiadiazole ring to prepare the title compounds fused 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole heterocyclic compounds. From the results on biological activities, we found that most compounds showed weak activities, and thus the structures need to be further optimized for improved activity. 相似文献
993.
Efficient and accurate procedure for selecting ground motions matching target response spectrum 总被引:2,自引:0,他引:2
Linear and nonlinear response history analyses have become popular in seismic design and seismic performance evaluation procedures. The accuracy of analysis results depends not only on the accurate analytic models for structures but also on the proper selection of input ground motions. The purpose of this study is to develop a computationally efficient and accurate procedure for selecting ground motions considering the target response spectrum mean and variance, and the correlations between response spectra of different periods. In this procedure, a number of response spectra are simulated equal to the number of ground motions to be selected, using a Monte Carlo simulation. Subsequently, ground motions are selected from a ground motion library to individually match the simulated response spectra, using the proposed selection procedure. This procedure is computationally efficient and accurate in selecting a ground motion that best matches a simulated response spectrum and in determining a scaling factor for the selected ground motion. In order to further improve the selection result, multiple sets of simulated response spectra are considered. The accuracy and efficiency of the proposed procedure are verified with numerical examples. 相似文献
994.
995.
Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine 下载免费PDF全文
A new, convenient and efficient AgNO3‐catalyzed strategy for the preparation of 2‐(benzo[d]azol‐2‐yl)phenol derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO3 as a readily available and low‐cost benign oxidant at low catalyst loadings with excellent functional group tolerance. 相似文献
996.
Fang Dong Rong-Zhang Jin Jian-Quan Liu Xiang-Shan Wang 《Research on Chemical Intermediates》2017,43(11):5995-6006
997.
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
998.
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
999.
1000.
Effects of silica nanoparticle addition on polymer semiconductor wettability and carrier mobility in solution‐processable organic transistors on hydrophobic substrates 下载免费PDF全文
Takashi Nagase Masashi Yoshikawa Saori Yamazaki Takashi Kobayashi Yoshiki Michiwaki Seiji Watase Mitsuru Watanabe Kimihiro Matsukawa Hiroyoshi Naito 《Journal of Polymer Science.Polymer Physics》2016,54(4):509-516
The effects of the addition of silica nanoparticles (SNPs) on wettability of regioregular poly(3‐hexylthiophene) (P3HT) organic semiconductor solutions on hydrophobic substrates and the carrier mobility in organic field‐effect transistors (OFETs) made of these films are investigated. The dewetting of films made from P3HT solutions on hydrophobic substrates modified with octadecyltrichlorosilane (ODTS) is markedly suppressed after the addition of SNPs with phenyl surfactants. This enables us to fabricate continuous P3HT/SNPs films with high crystallinity by the conventional spin‐coating technique, leading to higher mobility compared with P3HT FETs fabricated on non‐modified substrates. Moreover, the addition of SNPs with larger diameters compensates for the degradation of mobility associated with the increase in the concentration of SNPs. Solution‐processed P3HT/SNPs FETs on ODTS‐modified substrates exhibit a field‐effect mobility of 1.3 × 10?2 cm2 V?1 s?1, which is almost comparable to that of P3HT FETs without SNPs (2.1 × 10?2 cm2 V?1 s?1). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 509–516 相似文献