全文获取类型
收费全文 | 477篇 |
免费 | 64篇 |
国内免费 | 58篇 |
专业分类
化学 | 255篇 |
晶体学 | 10篇 |
力学 | 40篇 |
综合类 | 1篇 |
数学 | 62篇 |
物理学 | 137篇 |
无线电 | 94篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 26篇 |
2020年 | 19篇 |
2019年 | 22篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 22篇 |
2015年 | 26篇 |
2014年 | 27篇 |
2013年 | 36篇 |
2012年 | 46篇 |
2011年 | 30篇 |
2010年 | 17篇 |
2009年 | 31篇 |
2008年 | 27篇 |
2007年 | 20篇 |
2006年 | 27篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有599条查询结果,搜索用时 0 毫秒
1.
2.
Dr. Jun Zeng Dr. Zhichao Wang Dr. Xin Huang Dr. Sabine S. Eckstein Prof. Dr. Xiaohui Lin Prof. Dr. Hailong Piao Prof. Dr. Cora Weigert Dr. Peiyuan Yin Prof. Dr. Rainer Lehmann Prof. Dr. Guowang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(21):5427-5432
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism. 相似文献
3.
In a recent work (Int. J. Solids Struct. 37 (2000) 1561) by one of the authors, an extended system for calculating critical points of equilibrium paths in imperfect structures was presented. However, the extremum nature of these points was not analyzed explicitly in that paper. In this note, we will fill in the gap and establish a sufficient condition for determining the buckling strength of imperfect structures. 相似文献
4.
硅杂环丁烷在有机硅化学中是一类非常重要的小分子环系化合物。由于硅杂环丁烷和环丁烷的环张力相似,因而显示出较高的反应活性。例如能与某些试剂作用,生成开环产物;在光解或热解条件下,产生具有Si=C结构的高活性中间体,可用以合成多种有机硅化合物。 相似文献
5.
Flow injection spectrofluorimetry with in-line Winklers procedure was developed for the dissolved oxygen (DO) determination. 2-Thionaphthol reacted with iodine produced by Winkler’s method to form fluorescence inactive disulfide compound. To automate the process completely, a 5-channel flow system with a newly designed 16-way valve was assembled. The system consisted of a dispersion coil (DC), a precipitate formation coil (PFC), a precipitate dissolving coil (PDC), and extraction coil (EC). A calibration can be constructed by using a standard iodine solution for dissolved oxygen. The calibration graph was linear over the range 1.2×10−4∼6.0×10−4 mol l−1 iodine (1.96∼9.80 mg O l−1)). The relative standard deviation (n=6) was below 0.3% for the 4×10−4 mol l−1 iodine (6.27 mg O l−1) determination. The sample throughput was 12/h. 相似文献
6.
Photocatalytic oxidation of water is a promising method to realize large-scale H2O2 production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO2(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H2 and H2O2 production. Both H2 and H2O2 are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g–1 h–1 (first 1 h) for H2 and H2O2, respectively, which is much higher than that of a commercial Pt/TiO2(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H2O2, compared with the four-electron oxidation of water to O2. 相似文献
7.
Byeong Hyo Kim Rongbi HanFengyu Piao Young Moo JunWoonphil Baik Byung Min Lee 《Tetrahedron letters》2003,44(1):77-79
N-Arylacetamides were prepared in excellent yields from nitroarenes in the presence of acetic anhydride, acetic acid and indium by a one-pot procedure. 相似文献
8.
从本征模的角度阐明了频率搅拌技术的混响原理,并根据激励信号的频域特征,系统研究了频率搅拌方式下获取实时均匀场与统计均匀场的三种有效实现途径。选取线性扫频这一搅拌方式为主要研究对象,检验了混响室频率搅拌下的最低可用频率、场均匀性与统计特性三项主要技术指标。试验结果表明:线性扫频搅拌方式下,混响室的最低可用频域与机械搅拌方式基本一致;场均匀性满足IEC 61000-4-21标准规定的容差要求;场值波动规律符合理论分布模型。 相似文献
9.
Dr. Dai Wu Xiu-Fang Mo Prof. Piao He Dr. Hai-Ru Li Prof. Xiao-Yi Yi Prof. Chao Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(40):10313-10322
Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH4][(UO2)3(HTTDS)(H2O)] ( 1 ), [(UO2)4(HTTDS)2](HIM)6 ( 2 , IM=imidazole), [(UO2)4(TTDS)(H2O)2(Phen)2] ( 3 , Phen=1,10-phenanthroline), [Zn(H2O)4]0.5[(UO2)3(HTTDS)(H2O)4] ( 4 ), and {(UO2)2[Zn(H2O)3]2(TTDS)} ( 5 ), {Zn(UO2)2(H2O)(Dib)0.5(HDib)(HTTDS)} ( 6 , Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO2)4[Cu3(u3-OH)(H2O)7](TTDS)2} ( 7 ) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H8TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO7 pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO2]2+ units as co-ligands. The second metal centers were introduced in the syntheses of 4–7 , and in all cases, they are part of the final structures, either as a counterion ( 4 ) or as a component of framework ( 5 − 7 ). Interesting, in 7 , a rare polyoxometalate [Cu3(μ3-OH)O7(O2CR)4] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO2)2(O2CR)4] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail. 相似文献
10.
Russian Physics Journal - The lateral vibration coupling mechanism is the basic law describing the current vibration behavior of a high-speed train. The main reason is that there are design defects... 相似文献