全文获取类型
收费全文 | 32546篇 |
免费 | 2968篇 |
国内免费 | 3223篇 |
专业分类
化学 | 21279篇 |
晶体学 | 394篇 |
力学 | 1687篇 |
综合类 | 344篇 |
数学 | 3068篇 |
物理学 | 11965篇 |
出版年
2025年 | 55篇 |
2024年 | 362篇 |
2023年 | 649篇 |
2022年 | 960篇 |
2021年 | 1159篇 |
2020年 | 1313篇 |
2019年 | 1347篇 |
2018年 | 959篇 |
2017年 | 879篇 |
2016年 | 1361篇 |
2015年 | 1409篇 |
2014年 | 1649篇 |
2013年 | 2104篇 |
2012年 | 2493篇 |
2011年 | 2441篇 |
2010年 | 1868篇 |
2009年 | 1772篇 |
2008年 | 1982篇 |
2007年 | 1870篇 |
2006年 | 1750篇 |
2005年 | 1488篇 |
2004年 | 1175篇 |
2003年 | 1015篇 |
2002年 | 985篇 |
2001年 | 783篇 |
2000年 | 642篇 |
1999年 | 634篇 |
1998年 | 511篇 |
1997年 | 449篇 |
1996年 | 424篇 |
1995年 | 364篇 |
1994年 | 309篇 |
1993年 | 265篇 |
1992年 | 223篇 |
1991年 | 187篇 |
1990年 | 206篇 |
1989年 | 144篇 |
1988年 | 109篇 |
1987年 | 85篇 |
1986年 | 83篇 |
1985年 | 76篇 |
1984年 | 38篇 |
1983年 | 41篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1977年 | 8篇 |
1973年 | 4篇 |
1957年 | 3篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Based on the complexation between proteins and Cu(II) coupled with the time-resolved chemiluminescence (CL) technique, a highly sensitive and quantitative assay for measuring proteins in solution is described. The complexes of proteins with Cu(II) have a strongly catalytic effect on the luminol-H2O2 CL reaction. Because the CL emission produced by the complexes is much more long-lived than that by Cu(II), the CL signals originating from proteins can be easily identified and measured with a time-resolved technique. On this basis, bovine albumin fraction V (BAF V) can be quantitatively determined in the range of 0.01 - 5.0 microg/ml with a detection limit of 5.8 ng/ml. The results show that the proposed assay exhibits a small variation in the response values for the same amount of different proteins, as compared to the Lowry as well as Bradford assays. The CL assay has also been studied for the detection of immobilized proteins. 相似文献
2.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献
3.
Zhishen Mo Lixiao Wang Hongfang Zhang Ping Han Baotong Huang 《Journal of Polymer Science.Polymer Physics》1987,25(9):1829-1837
Wide-angle X-ray scattering from presumed block copolymers of polypropylene (PP) and ethylene-propylene copolymer (EPR), i.e., PP-EPR and PP-EPR-PP, synthesized by sequential polymerization with δ-TiCl3? Et2AlCl, was examined and compared with WAXS of mechanical blends and chain-transfer mixtures of PP and EPR with comparable compositions. The peak at 2θ = 20° for both the copolymers and the mixtures was attributed to the γ modification of PP in EPR. A strong variation in the ratio of diffraction intensities I040/I110 of PP in block copolymers and mixtures was explained in terms of crystallite growth in different directions. Analysis of the patterns and calculation of crystallinity, crystallite size, and lattice parameters led to the conclusion that block structure existed in the prepared copolymers. 相似文献
4.
5.
6.
7.
An indirect laser photoacoustic technique is described. The basic principle, the experimental set-up and the influencing factors are discussed in detail. This method was used to quantify phenylamine, arginine and methylene blue on membranes. The linear ranges of the calibration curve are up to two orders of magnitude. With 1 microliter of sample solution, the detection limits are 0.25, 1.52 and 0.14 pmol for phenylamine, arginine and methylene blue, respectively. 相似文献
8.
9.
Organic phase conversion of bulk (wurtzite) ZnO to nanophase (wurtzite and zinc blende) ZnO 总被引:1,自引:0,他引:1
Lauren P. Snedeker Aditi S. Risbud Ombretta Masala Jin Ping Zhang Ram Seshadri 《Solid State Sciences》2005,7(12):1500
We describe the all-organic phase conversion of bulk commercial ZnO in the wurtzite modification to sub-30 nm ZnO that we find to be partially in the zinc blende [, a=4.568(3) Å] modification. The conversion involves refluxing ZnO in 2,4-pentanedione (acetylacetone) at 413 K to form the zinc 2,4-pentanedionate, which is decomposed by heating at 573 K in an appropriate high-temperature solvent such as dibenzylether to form nanophase ZnO. This nanophase, partially zinc blende ZnO can also be obtained in a single step by heating commercial zinc 2,4-pentanedionate in refluxing dibenzylether. Thermodiffractometry suggests that the conversion of zinc blende ZnO to wurtzite ZnO commences near 650 K. 相似文献
10.
本文报导的方法是在南京大学高鸿教授研究的K_3Fe(CN)_6示波极谱滴定法(在PH8的K_2HPO_4—KH_2PO_4—KBr底液中,用0.04660mol/LK_3Fe(CN)_6标准溶液对纯抗坏血酸测定)的基础上,考虑到L—抗坏血酸(以下简称V_e)在碱性、中性介质中稳定性差,如用于V_e含量很微的果蔬测定,对结果影响大。本文改为H_2C_2O_4—KBr的酸性介质作底液,用 相似文献