全文获取类型
收费全文 | 1919篇 |
免费 | 56篇 |
国内免费 | 14篇 |
专业分类
化学 | 1664篇 |
晶体学 | 14篇 |
力学 | 9篇 |
综合类 | 1篇 |
数学 | 70篇 |
物理学 | 231篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 11篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 31篇 |
2014年 | 47篇 |
2013年 | 104篇 |
2012年 | 102篇 |
2011年 | 118篇 |
2010年 | 69篇 |
2009年 | 60篇 |
2008年 | 124篇 |
2007年 | 120篇 |
2006年 | 129篇 |
2005年 | 107篇 |
2004年 | 124篇 |
2003年 | 76篇 |
2002年 | 82篇 |
2001年 | 40篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 15篇 |
1997年 | 30篇 |
1996年 | 13篇 |
1995年 | 21篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1974年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有1989条查询结果,搜索用时 15 毫秒
51.
A catalytic immuno-reactor for the determination of human serum albumin (HSA) was constructed by using immobilized antibody and an amperometric detector. A sandwich assay with hemin-labeled antibody to catalyze the decomposition of hydrogen peroxide was used, the catalytic activity of the hemin-antibody conjugate being determined by measuring the decrease in hydrogen peroxide concentration. The reaction of hemin-labeled antibody with antigen was complete within 30 min and the current decrease was correlated with the HSA concentration. The relative standard deviation was about 9% at an HSA concentration of 1 mg ml?1. 相似文献
52.
A nanosecond laser photolysis study was carried out for the Cr(III) porphyrin complexes of 2,3,7,8,12,13,17,18-octaethylporphyrin, [Cr(OEP)(Cl)(L)], and of 5,10,15,20-tetramesitylporphyrin, [Cr(TMP)(Cl)(L)], in toluene containing water and an excess amount of L (L = axial ligand). The laser photolysis generates the triplet excited state of the parent complex as well as a five-coordinate complex, [Cr(porphyrin)(Cl)], produced by the photodissociation of the axial ligand L. The yields for the formation of the triplet state and the photodissociation of L are found to markedly depend on the nature of both L and porphyrin ligand. The five-coordinate [Cr(porphyrin)(Cl)] readily reacts with both H(2)O and L in the bulk solution to give [Cr(porphyrin)(Cl)(H(2)O)] and [Cr(porphyrin)(Cl)(L)], respectively. The axial H(2)O ligand in [Cr(porphyrin)(Cl)(H(2)O)] is then substituted by the ligand L to regenerate the original complex [Cr(porphyrin)(Cl)(L)]. In principle, the substitution reaction takes place by the dissociative mechanism: the first step is the dissociation of H(2)O from [Cr(porphyrin)(Cl)(H(2)O)], followed by the reaction of the five-coordinate [Cr(porphyrin)(Cl)] with the ligand L to regenerate [Cr(porphyrin)(Cl)(L)]. The rate constants for this ligand substitution reaction are found to exhibit bell-shaped ligand concentration dependence. The detailed kinetic analysis revealed that both ligands L and H(2)O in toluene make a hydrogen bond with the axial H(2)O ligand in [Cr(porphyrin)(Cl)(H(2)O)] to yield dead-end complexes for the substitution reaction. The reaction mechanisms are discussed on the basis of the substituent effects of the porphyrin peripheral groups and the kinetic parameters determined from the temperature dependence of the rate constants. 相似文献
53.
54.
55.
56.
57.
The concentration of potassium was determined by a combination of flow injection analysis (FIA) with an all-solid-state potassium sensor detection. The all-solid-state potassium-selective electrode possessing long-term potential stability was fabricated by coating an electroactive polypyrrole/poly(4-styrenesulfonate) film electrode with a plasticized poly(vinyl chloride) membrane containing valinomycin. The simple FIA system developed in this laboratory demonstrated sensitivity identical to that in the batch system and achieved considerably rapid assay (150 samples h−1). Analyses of soy sauce and control serum samples by this FIA system yielded results in good agreement with those obtained by conventional measurements. 相似文献
58.
Miura T Goto K Waragai H Matsumoto H Hirose Y Ohmae M Ishida HK Satoh A Inazu T 《The Journal of organic chemistry》2004,69(16):5348-5353
The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS. 相似文献
59.
Katayama H Satoh K Takeuchi M Deguchi-Tawarada M Oda Y Nagasu T 《Rapid communications in mass spectrometry : RCM》2003,17(10):1071-1078
Improvement of in-gel digestion efficiency is highly desirable for one- or two-dimensional gel electrophoretic separation and mass spectrometric (MS) analysis in proteomics, because the resultant increases in sequence coverage and MS signal intensity lead to higher confidence in protein identification. Here an optimized in-gel digestion system, in combination with thin-gel separation and negative staining in a high-throughput format using 96-well plates, is described. The combination of negative staining and protein separation on a 0.9 mm thick gel showed a clear improvement in in-gel digestion efficiency in comparison with the more typical protocols such as the combination of silver staining and a 1.0 mm gel. In addition, the use of 96-well plates to increase throughput did not decrease the efficiency of this strategy when the stirring of the gel pieces in processes such as destaining, washing, gel-shrinking and peptide extraction was performed by sonication instead of shaking the plates. This procedure was optimized and applied to identify proteins of the postsynaptic density fraction; 105 proteins were identified after SDS-PAGE separation. 相似文献
60.
Phenols are ethynylated at the ortho position with silylated chloroethyne in the presence of a catalytic amount of GaCl3 and lithium phenoxide. The lithium salt is essential for the catalysis, and addition of 2,6-di(tert-butyl)-4-methylpyridine inhibits desilylation and hydration of the products. The reaction can be applied to various substituted phenols giving the ortho-ethynylated products in high yields, and the turnover numbers based on GaCl3 are between 8 and 10. The reaction mechanism involves addition of in situ formed phenoxygallium to the haloethyne followed by the elimination of GaCl3. 相似文献