全文获取类型
收费全文 | 878篇 |
免费 | 31篇 |
国内免费 | 14篇 |
专业分类
化学 | 565篇 |
晶体学 | 8篇 |
力学 | 17篇 |
综合类 | 4篇 |
数学 | 84篇 |
物理学 | 245篇 |
出版年
2023年 | 6篇 |
2022年 | 20篇 |
2021年 | 19篇 |
2020年 | 29篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 40篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 55篇 |
2012年 | 58篇 |
2011年 | 48篇 |
2010年 | 50篇 |
2009年 | 33篇 |
2008年 | 49篇 |
2007年 | 42篇 |
2006年 | 45篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 31篇 |
2001年 | 20篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有923条查询结果,搜索用时 15 毫秒
41.
de Oliveira Elcio Cruz de Santana Maia Lúcio Abdala da Costa Lívio Garcia Lourenço Túlio Campos 《Accreditation and quality assurance》2018,23(6):365-369
Accreditation and Quality Assurance - In any commercial transaction, the presence of tolerances from specification limits is essential to ensure that the true value of the property of interest is... 相似文献
42.
43.
Rapid and sensitive ultra‐high‐pressure liquid chromatography method for quantification of antichagasic benznidazole in plasma: application in a preclinical pharmacokinetic study
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marcelo Gomes Davanço Michel Leandro de Campos Rosângela Gonçalves Peccinini 《Biomedical chromatography : BMC》2015,29(7):1008-1015
Benznidazole (BNZ) and nifurtimox are the only drugs available for treating Chagas disease. In this work, we validated a bioanalytical method for the quantification of BNZ in plasma aimed at improving sensitivity and time of analysis compared with the assays already published. Furthermore, we demonstrated the application of the method in a preclinical pharmacokinetic study after administration of a single oral dose of BNZ in Wistar rats. A Waters® Acquity UHPLC system equipped with a UV–vis detector was employed. The method was established using an Acquity® UHPLC HSS SB C18 protected by an Acquity® UHPLC HSS SB C18 VanGuard guard column and detection at 324 nm. The mobile phase consisted of ultrapure water–acetonitrile (65:35), and elution was isocratic. The mobile phase flow rate was 0.55 mL/min, the volume of injection was 1 μL, and the run time was just 2 min. The samples were kept at 25°C until injection and the column at 45°C for the chromatographic separation. The sample preparation was performed by a rapid protein precipitation with acetonitrile. The linear concentration range was 0.15–20 µg/mL. The pharmacokinetic parameters of BNZ in rats were determined and the method was considered sensitive, fast and suitable for application in pharmacokinetic studies. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
44.
Ramadan Ali Benito Campos Gerhard Dyckhoff Walter E. Haefeli Christel Herold-Mende Jürgen Burhenne 《Analytica chimica acta》2012
Retinoic acid signaling is essential for central nervous system (CNS) differentiation and appears to be impaired in tumors. Thus far, there are no established methods to quantify relevant retinoids (all-trans-retinoic acid, 9-cis-retinoic acid, 13-cis retinoic acid, and retinol) in human brain tumors. We developed a single step extraction and quantification procedure for polar and apolar retinoids in normal tissue, lipid-rich brain tumor tissues, and serum. This quantification procedure is based on high performance liquid chromatography (HPLC) with diode-array detection (DAD) using all-trans-acitretin as an internal standard and extraction by liquid–liquid partition with ethyl acetate and borate buffer at pH 9. Recovery with this extraction procedure was higher than earlier (two-step) liquid–liquid extraction procedures based on hexane, NaOH, and HCl. The overall quantification procedure was validated according to Food and Drug Administration (FDA) guidelines and fulfilled all criteria of accuracy, precision, selectivity, recovery, and stability. The overall method accuracy varied between −5.6% and +5.4% for serum and −3.8% and +6.2% for tissues, and overall precision ranged from 3.1% to 6.9% for serum and 2.1% to 8.3% for tissues (%CV batch-to-batch). The lower limit of quantification for all compounds in tumor tissue (and serum) was 3.9 ng g−1 (ng mL−1). Using this assay, photodegradation of the retinoids was evaluated and endogenous polar and apolar retinoids were quantified in sera and brain tumor tissues of patients and compared with serum and tonsil tissue concentrations of controls. It may thus serve as a suitable method for the characterization of retinoid uptake and metabolism in the respective compartments. 相似文献
45.
46.
Marcos Costa Souza William Pires Macedo Marcelo Campos M. Silva Guilherme Costa de O. Ramos Helmut G. Alt 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1047-1054
This article describes an attractive and one-pot synthesis of the title compound by phosphorylation of just prepared N-substituted guanidines from cyanamide and the desired amine. The method allows a variety of N-substituents to hang on the final phosphoryl guanidine as a function of the wider availability of commercial simple amines. 相似文献
47.
In this paper the affine connection approach will be used to calculate the elastic constants of nematic liquid crystals. Following this approach, which was originally conceived to compute the nematic viscosity coefficients, an expression for the elastic constants, without adjustable free parameters, will be formulated in terms of a temperature dependent metric, whose non‐isotropic part is proportional to the tensorial order parameter of the nematic phase. The dependence of the elastic constants on the scalar order parameter, in the geometry of the nematic molecules, and in the anisotropic part of the molecular interaction, will be determined. 相似文献
48.
Motta Neves Roberta Ornaghi Heitor Luiz Duchemin Benoit Zattera Ademir Jos Campos Amico Sandro 《Cellulose (London, England)》2022,29(6):3209-3224
Cellulose - Microcrystalline cellulose (MCC) has unique properties and its use as reinforcement for polymer composites has been increasing. However, the intrinsic incompatibility with most polymers... 相似文献
49.
Ana Elisa Ferreira Oliveira Arnaldo César Pereira Mayra Asevedo Campos de Resende Lucas Franco Ferreira 《Electroanalysis》2022,34(5):809-819
In this work, a silver/silver chloride ink is fabricated using two steps. First the silver ink is prepare using silver, nail polish and acetone. Then the silver ink is painted in a paper substrate and a silver chloride layer is deposited using a bleach solution. The result is the silver/silver chloride conductive ink. The silver ink is cheap ($2.49/g), well-dispersive and very easy to fabricate. The materials were characterized by SEM and XRD. The Ag ink showed the formation of a continuous network throughout the silver ink film with fewer agglomeration. The effective chlorination process was also observed in the Ag/AgCl characterization. Since the Ag/AgCl substrate will be used as a quasi-reference electrode, it is important to investigate the electrical properties. The Ag ink showed an average ohmic resistance of 2.27 Ω. The addition of the AgCl layer decreases the conductivity, as expected. In summary, the Ag/Ag/Cl ink developed is simple, well-dispersed, cheap and with good conductivity. Therefore, it can be used as a conductive ink in the fabrication of quasi-reference electrodes. 相似文献
50.
Jeferson Rodrigo Souza Pina Joo Victor Silva-Silva Josiwander Miranda Carvalho Heriberto Rodrigues Bitencourt Luciano Almeida Watanabe Juan Matheus Pereira Fernandes Guilherme Eduardo de Souza Anna Caroline Campos Aguiar Rafael Victorio Carvalho Guido Fernando Almeida-Souza Ktia da Silva Calabrese Patrícia Santana Barbosa Marinho Andrey Moacir do Rosario Marinho 《Molecules (Basel, Switzerland)》2021,26(11)
The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin’s antiparasitic activities were assessed against both the epimastigote (IC50 value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC50 value of 9 ± 2 µM), as well as against P. falciparum (IC50 value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC50 > 50 µM) and peritoneal macrophage (CC50 = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development. 相似文献