全文获取类型
收费全文 | 1184篇 |
免费 | 55篇 |
国内免费 | 2篇 |
专业分类
化学 | 845篇 |
晶体学 | 19篇 |
力学 | 17篇 |
数学 | 59篇 |
物理学 | 301篇 |
出版年
2023年 | 16篇 |
2022年 | 28篇 |
2021年 | 36篇 |
2020年 | 45篇 |
2019年 | 63篇 |
2018年 | 52篇 |
2017年 | 39篇 |
2016年 | 57篇 |
2015年 | 44篇 |
2014年 | 106篇 |
2013年 | 120篇 |
2012年 | 73篇 |
2011年 | 75篇 |
2010年 | 39篇 |
2009年 | 36篇 |
2008年 | 44篇 |
2007年 | 32篇 |
2006年 | 32篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 18篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有1241条查询结果,搜索用时 15 毫秒
41.
A photoredox catalytic ensemble consisting of CuO‐Fe2O3 nanocomposites and oligomeric derivative of phenazine has been developed. The prepared system acts as an efficient photoredox catalyst for C?N bond formation reaction via SET mechanism under ‘green’ conditions (aerial environment, mixed aqueous media, recyclable), requiring less equivalents of base and amine substrate. The present study demonstrates the significant role of supramolecular assemblies as photooxidants and reductants upon irradiation and their important contribution towards the activation of the metallic centre through energy transfer and electron transfer pathways. The potential of oligomer 4 : CuO‐Fe2O3 has also been explored for C?C bond formation reactions via the Sonogashira protocol. 相似文献
42.
43.
44.
45.
46.
47.
The infectious disease burden imposed by trypanosomatidae family continues to create burden in countries that are least equipped
to bring new medicines to the clinic. For sickness caused by this family of parasites (African trypanosomiasis, Chagas disease,
and leishmaniasis) no vaccines are available, and currently available drugs suffer from insufficient efficacy, excessive toxicity,
and steady loss of effectiveness due to resistance. Availability of the genome sequence of pathogens of this family offers
a unique avenue for the identification of novel common drug targets for all three pathogens. Sirtuin family of nicotinamide
adenine dinucleotide (NAD)-dependent deacetylases are remarkably conserved throughout evolution from archaebacteria to eukaryotes
and plays an important role in trypanosomatidae biology and virulence. In order to gain insight for selective drug design,
three-dimensional (3D) models of L. major, L. infantum, T. brucie, and T. cruzi sirtuin were constructed by homology modeling and compared with human sirtuin. The molecular electrostatic potentials and
cavity depth analysis of these models suggest that the inhibitor binding catalytic domain has various minor structural differences
in the active site of trypanosomal and human sirtuin, regardless of sequence similarity. These studies have implications for
designing effective strategies to identify inhibitors that can be developed as novel broad-spectrum antitrypanosomal drugs. 相似文献
48.
The current work entails development of rapid, sensitive, and inexpensive high-performance liquid chromatographic method of quercetin dihydrate using the quality by design approach. Quality target method profile was defined and critical analytical attributes (CAAs) were earmarked. Chromatographic separation was accomplished on a C18 column using acetonitrile and ammonium acetate buffer (35:65) %v/v (containing 0.1% acetic acid, pH 3.5) as mobile phase at 0.7?mL/min flow rate with UV detector at 237?nm. Screening studies using fractional factorial design revealed that organic modifier, injection volume, column temperature, and buffer strength have significant influence on method CAAs, namely, peak area, retention time, and peak tailing. The critical method parameters were systematically optimized using Box–Behnken design. Response surface mapping was used along with numerical optimization and desirability function for identifying the optimal chromatographic conditions. Linearity was observed in the drug concentration ranging between 2 and 50?µg/mL. Accuracy analysis revealed mean % recovery between 93.6 and 96.2%, while precision study revealed mean % recovery between 93.7 and 96.5%. Limits of detection and quantification of the developed method were found to be 12.1 and 36.6?ng/mL. Overall, the studies construed successful development of chromatographic method of quercetin with enhanced method performance. 相似文献
49.
50.
The ring opening polymerization of L-lactide was studied in bulk using stannous octoate as initiator. In some experiments, triphenylphosphine, a Lewis base was also used as co-initiator. The polymerization was carried out at 130°C up to 29 h. The monomer was used after recrystallizing three times with dry toluene. Experiments were carried out using a wide range of monomer to initiator ratio. The averages and distributions of molar masses of resulting PLA have been determined by means of size exclusion chromatography, SEC. It is shown that the (mode, process) procedure of dispersion of the catalyst in polymerization system affects the molar mass distribution of the product as is evidenced by the bimodality or even trimodality observed in the SEC chromatograms. 相似文献