全文获取类型
收费全文 | 1043篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
化学 | 821篇 |
晶体学 | 36篇 |
力学 | 24篇 |
数学 | 33篇 |
物理学 | 170篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 24篇 |
2021年 | 33篇 |
2020年 | 16篇 |
2019年 | 36篇 |
2018年 | 32篇 |
2017年 | 37篇 |
2016年 | 44篇 |
2015年 | 25篇 |
2014年 | 45篇 |
2013年 | 103篇 |
2012年 | 81篇 |
2011年 | 84篇 |
2010年 | 48篇 |
2009年 | 48篇 |
2008年 | 69篇 |
2007年 | 60篇 |
2006年 | 72篇 |
2005年 | 48篇 |
2004年 | 39篇 |
2003年 | 25篇 |
2002年 | 23篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1084条查询结果,搜索用时 15 毫秒
131.
Eleven constituents were characterised by gas chromatography–mass spectrometry analysis, and five molecules were isolated using column chromatography. The in vitro study of the extract and isolated molecules against KB and SiHa cell lines revealed oleanolic acid (1) and oleic acid (2) as potent cytotoxic molecules with potential anticancer activity. The IC50 values of n-hexane extract (CPHF), oleanolic acid (1) and oleic acid (2) were >300, 56.08 and 70.7 μg/mL (μM), respectively, against KB cell lines and >300, 47.24 and 80.2 μg/mL (μM), respectively, against SiHa cell lines. 相似文献
132.
133.
Nonsteroidal Anti‐inflammatory Drug‐based N‐Allylidene Benzohydrazides and 1‐Acyl‐2‐pyrazolines: Their Synthesis as Potential Cytotoxic Agents In Vitro 下载免费PDF全文
Kavitha Kankanala V. Ranga Reddy Yumnam Priyadarshini Devi Lakshmi Narasu Mangamoori D. Rambabu K. Mukkanti Sarbani Pal 《Journal of heterocyclic chemistry》2015,52(1):105-113
A series of 1‐acyl‐2‐pyrazoline derivatives derived from nonsteroidal anti‐inflammatory drugs was designed as potential anticancer agents. Synthesis of these compounds was carried out via the condensation reaction of chalcones and acid hydrazides under heating. The methodology did not require the use of any costly reagents or catalysts, and the acid hydrazide reactants were readily prepared from mefenamic acid or ibuprofen. A variety of 1‐acyl‐2‐pyrazolines was prepared in good to excellent yields. An N‐allylidene benzohydrazide intermediate was isolated during the reaction optimization study, the structure of which was confirmed unambiguously by X‐ray single crystal data. A range of N‐allylidene benzohydrazides were also prepared in good yields. Some of the compounds synthesized showed promising cytotoxic activities when tested against HCT‐15 human colon cancer cell line in vitro. 相似文献
134.
M. Subathra P. Santhakumar Sureddi Satyam Naidu M. Lakshmi Narasu T. M. A. Senthilkumar Sunil K. Lal 《Applied biochemistry and biotechnology》2014,172(7):3635-3645
The conventional avian influenza vaccines rely on development of neutralizing antibodies against the HA and NA antigens. However, these antigens are highly variable, and hence there is a need for better vaccine candidates which would offer broader protection in animals. The M1 of avian influenza is another major structural protein that has conserved epitopes that are reported to induce CD8+ T cells and can contribute to protection against morbidity and mortality from influenza. Hence in an effort to study the immune response of rM1 either alone or in combination with rHA, the hemagglutinin (HA) and matrix protein (M1) of A/Hatay/2004/H5N1 strain of avian influenza were expressed in Pichia pastoris as his-tagged proteins and purified through Ni-NTA chromatography. The His-tag was removed using TEV protease cleavage site and the immunogenicity of purified rHA and rM1 either alone or in combination was determined in mice. One group of mice was immunized with 5 μg of purified rHA, the other group was immunized with rM1, and a third group of mice were immunized with 5 μg of rHA and rM1. All the animals were boosted twice, once on 28 days postimmunization (dpi) and the second on 42 dpi. The immune response was evaluated by enzyme-linked immunosorbent assay (ELISA) and hemagglutination inhibition (HI) assay. The group of mice immunized with rHA and rM1 together showed significantly higher immune response against rHA and rM1 than mice immunized with either HA or M1 antigens. The addition of rM1 with rHA resulted in increased HI titer in animals immunized with both the antigens. These results suggest that the HA and M1 expressed in P. pastoris can be utilized in combination for the development of faster and cost-effective vaccines for circulating and newer strains of avian influenza and would aid in combating the disease in a pandemic situation, in which production time matters greatly. 相似文献
135.
136.
Nano palladium supported on high‐surface‐area metal–organic framework MIL‐101: an efficient catalyst for Sonogashira coupling of aryl and heteroaryl bromides with alkynes 下载免费PDF全文
Manne Annapurna T. Parsharamulu P. Vishnuvardhan Reddy M. Suresh Pravin R. Likhar Mannepalli Lakshmi Kantam 《应用有机金属化学》2015,29(4):234-239
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
137.
An efficient copper-aluminum hydrotalcite catalyst for asymmetric hydrosilylation of ketones at room temperature 总被引:1,自引:0,他引:1
Kantam ML Laha S Yadav J Likhar PR Sreedhar B Jha S Bhargava S Udayakiran M Jagadeesh B 《Organic letters》2008,10(14):2979-2982
A catalyst system consisting of a copper-aluminum hydrotalcite-chiral diphosphine ligand effects asymmetric hydrosilylation of several ketones, using polymethylhydrosiloxane (PMHS) as the stoichiometric reducing agent at room temperature, with moderate-to-excellent enantioselectivities. The catalyst is recovered by simple centrifugation, and the efficiency of the catalyst remains almost unaltered even after several cycles. 相似文献
138.
139.
M. Lakshmi Kantam Thekkathu Ramani Lakkoju Chakrapani K.Vijay Kumar 《Tetrahedron letters》2008,49(9):1498-1501
The direct asymmetric aldol reactions of aromatic and heteroaromatic aldehydes with acetone to afford chiral β-hydroxy carbonyl compounds in good yields and good to moderate enantioselectivities are realized using nanocrystalline copper(II) oxide in the presence of (1S,2S)-(−)-1,2-diphenylethylenediamine at −30 °C. The catalyst can be reused for four cycles with consistent activity and enantioselectivity. 相似文献
140.