全文获取类型
收费全文 | 2142篇 |
免费 | 62篇 |
国内免费 | 11篇 |
专业分类
化学 | 1424篇 |
晶体学 | 10篇 |
力学 | 55篇 |
数学 | 286篇 |
物理学 | 440篇 |
出版年
2024年 | 3篇 |
2023年 | 27篇 |
2022年 | 72篇 |
2021年 | 87篇 |
2020年 | 55篇 |
2019年 | 74篇 |
2018年 | 60篇 |
2017年 | 47篇 |
2016年 | 123篇 |
2015年 | 63篇 |
2014年 | 103篇 |
2013年 | 135篇 |
2012年 | 184篇 |
2011年 | 178篇 |
2010年 | 100篇 |
2009年 | 84篇 |
2008年 | 109篇 |
2007年 | 128篇 |
2006年 | 99篇 |
2005年 | 97篇 |
2004年 | 79篇 |
2003年 | 47篇 |
2002年 | 42篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有2215条查询结果,搜索用时 15 毫秒
111.
César IC Byrro RM de Santana E Silva Cardoso FF Mundim IM de Souza Teixeira L Rezende KR da Silva EP Gomes SA de Sousa VA Bonfim RR Pianetti GA 《Biomedical chromatography : BMC》2012,26(7):851-856
A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐13C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
112.
113.
Montalbano F Candeias NR Veiros LF André V Duarte MT Bronze MR Moreira R Gois PM 《Organic letters》2012,14(4):988-991
The dative N-B bond was used to simply assemble heterocycles with a skeleton akin to the 5-oxofuro[2,3-b]furan motif. Twenty-five new N-B heterocycles were prepared via a highly efficient one-pot four-component reaction in yields and diastereoselectivities up to 95% and >97%, respectively. Several reaction intermediates were discovered using electrospray ionization mass spectroscopy which set the basis for the mechanism elucidation using DFT calculations. 相似文献
114.
Lidia Moreira Lima Tiago Fernandes da Silva Carlos Eduardo da Silva Monteiro Cristiane Aparecida-Silva Walfrido Bispo Júnior Aline Cavalcanti de Queiroz Magna Suzana Alexandre-Moreira Gisele Zapata-Sudo Eliezer J. Barreiro 《Molecules (Basel, Switzerland)》2021,26(16)
Acylhydrazones are still an important framework to the design of new bioactive compounds. As treatment of chronic pain represents a clinical challenge, we decided to modify the structure of LASSBio-1514 (1), previously described as anti-inflammatory and analgesic prototype. Applying the homologation as a strategy for molecular modification, we designed a series of cyclopentyl- (2a–e), cyclobutyl- (3a–e), and cyclopropylacylhydrazones (4a–e) that were synthetized and evaluated in murine models of inflammation and pain. A comparison of their in silico physicochemical and drug-like profile was conducted, as well as their anti-inflammatory and analgesic effect. Compounds 4a (LASSBio-1755) and 4e (LASSBio-1757) displayed excellent in silico drug-like profiles and were identified as new analgesic lead-candidates in acute and chronic model of pain, through oral administration. 相似文献
115.
Journal of Thermal Analysis and Calorimetry - We report data obtained from the spinodal decomposition in samples of two compositions of intermetallic Cu–Al–Mn shape memory alloys.... 相似文献
116.
Mirtha Navarro-Hoyos Elizabeth Arnez-Serrano Silvia Quesada-Mora Gabriela Azofeifa-Cordero Krissia Wilhelm-Romero María Isabel Quirs-Fallas Diego Alvarado-Corella Felipe Vargas-Huertas Andrs Snchez-Kopper 《Molecules (Basel, Switzerland)》2021,26(21)
There is an increased interest in plum research because of their metabolites’ potential bioactivities. In this study, the phenolic profiles of Prunus domestica commercial cultivars (Methley, Pisardii and Satsuma) in Costa Rica were determined by Ultra Performance Liquid Chromatography coupled with High Resolution Mass Spectrometry using a quadrupole-time-of-flight analyzer (UPLC-ESI-QTOF MS) on enriched phenolic extracts obtained through Pressurized Liquid Extraction (PLE) under acidic and neutral extraction conditions. In total, 41 different phenolic compounds were identified in the skin and flesh extracts, comprising 11 flavan-3-ols, 14 flavonoids and 16 hydroxycinnamic acids and derivatives. Neutral extractions for the skins and flesh from all of the cultivars yielded a larger number of compounds, and were particularly rich in the number of procyanidin trimers and tetramers when compared to the acid extractions. The total phenolic content (TPC) and antioxidant potential using the DPPH and ORAC methods exhibited better results for neutral extracts with Satsuma skins and Methley flesh, which showed the best values (685.0 and 801.6 mg GAE/g extract; IC50 = 4.85 and 4.39 µg/mL; and 12.55 and 12.22 mmol TE/g extract, respectively). A Two-Way ANOVA for cytotoxicity towards AGS gastric adenocarcinoma and SW620 colon adenocarcinoma indicated a significant difference (p < 0.05) for PLE conditions, with better results for neutral extractions, with Satsuma skin delivering the best results (IC50 = 60.7 and 46.7 µg/mL respectively) along with Methley flesh (IC50 = 76.3 and 60.9 µg/mL, respectively). In addition, a significant positive correlation was found between TPC and ORAC (r = 0.929, p < 0.05), as well as a significant negative correlation (p < 0.05) between TPC and cytotoxicity towards AGS and SW620 cell lines (r = −0.776, and −0.751, respectively). A particularly high, significant, negative correlation (p < 0.05) was found between the number of procyanidins and cytotoxicity against the AGS (r = −0.868) and SW620 (r = −0.855) cell lines. Finally, the PCA clearly corroborated that neutral extracts are a more homogenous group exhibiting higher antioxidant and cytotoxic results regardless of the part or cultivar; therefore, our findings suggest that PLE extracts under neutral conditions would be of interest for further studies on their potential health benefits. 相似文献
117.
118.
Diego Lomonaco Francisco Jonas Nogueira Maia Selma Elaine Mazzetto 《Journal of Thermal Analysis and Calorimetry》2013,111(1):619-626
In this study, the thermal-oxidative stability of poly(methyl methacrylate), PMMA, 1 % additivated with replenishable phenolic lipids is evaluated by thermogravimetric (TG/DTG) analyses and differential scanning calorimetry (DSC) analyses. Since technical cashew nutshell liquid (CNSL), a byproduct from the cashew industry, is composed basically of two phenolic lipids, cardanol and cardol, the utilization of this industrial waste and its main components as a new source of bioadditives for use as antioxidants is evaluated. The TG analyses revealed that addition of the phenolic constituent of CNSL increased the thermal stability of PMMA films considerably. The results obtained were also confirmed by DSC analyses. 相似文献
119.
Carmen Palermo Marilena Muscarella Donatella Nardiello Marco Iammarino Diego Centonze 《Analytical and bioanalytical chemistry》2013,405(2-3):1015-1023
In the present work a sensitive and accurate method by ion chromatography and conductimetric detection has been developed for the determination of biogenic amines in food samples at microgram per kilogram levels. The optimized extraction procedure of trimethylamine, triethylamine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine from real samples, as well as the separation conditions based on a multilinear gradient elution with methanesulfonic acid and the use of a weak ionic exchange column, have provided excellent results in terms of resolution and separation efficiency. Extended calibration curves (up to 200 mg/kg, r?>?0.9995) were obtained for all the analyzed compounds. The method gave detection limits in the range 23–65 μg/kg and quantification limits in spiked blank real samples in the range 65–198 μg/kg. Recovery values ranged from 82 to 103 %, and for all amines, a good repeatability was obtained with precision levels in the range 0.03–0.32 % (n?=?4). The feasibility and potential of the method were tested by the analysis of real samples, such as tinned tuna fish, anchovies, cheese, wine, olives, and salami. Figure
IEC‐CD multiresidual method for accurate determinations of biogenic amines in foodstuffs 相似文献
120.
Aysun apc Mlanie M. Lorion Hui Wang Nina Simon Maria Leidenberger Mariana C. BorgesSilva Diogo R. M. Moreira Yongping Zhu Yuqing Meng Jia Yun Chen Yew Mun Lee Oliver Friedrich Barbara Kappes Jigang Wang Lutz Ackermann Svetlana B. Tsogoeva 《Angewandte Chemie (International ed. in English)》2019,58(37):13161-13161