全文获取类型
收费全文 | 182篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 116篇 |
力学 | 6篇 |
数学 | 18篇 |
物理学 | 45篇 |
出版年
2023年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 7篇 |
2010年 | 15篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1908年 | 2篇 |
排序方式: 共有185条查询结果,搜索用时 15 毫秒
151.
Hicham Iken Frédéric Guillen Hélène Chaumat Marie-Rose Mazières Jean-Christophe Plaquevent Théodore Tzedakis 《Tetrahedron letters》2012,53(27):3474-3477
A range of alkylpyridinium bromide ionic liquids have been synthesized in a stirred reactor at multigram scale and characterized by physical methods (viscosity, conductivity, melting point, electrochemical window, and water content). One ionic liquid, octylpyridinium bromide, was chosen to be synthesized in both macro and reduced scale reactors, in order to compare its performance and to afford evidence of the advantages of a cross channel micro reactor (channel width = 1 mm) compared to a stirred reactor. 相似文献
152.
Isolation,Structure Elucidation,and (Bio)Synthesis of Haprolid,a Cell‐Type‐Specific Myxobacterial Cytotoxin 下载免费PDF全文
Heinrich Steinmetz Dr. Jun Li Dr. Chengzhang Fu Dr. Nestor Zaburannyi Dr. Birgitte Kunze Dr. Kirsten Harmrolfs Viktoria Schmitt Dr. Jennifer Herrmann Prof. Dr. Hans Reichenbach Prof. Dr. Gerhard Höfle Prof. Dr. Markus Kalesse Prof. Dr. Rolf Müller 《Angewandte Chemie (International ed. in English)》2016,55(34):10113-10117
Myxobacteria are well‐established sources for novel natural products exhibiting intriguing bioactivities. We here report on haprolid ( 1 ) isolated from Byssovorax cruenta Har1. The compound exhibits an unprecedented macrolactone comprising four modified amino acids and a polyketide fragment. As configurational assignment proved difficult, a bioinformatic analysis of the biosynthetic gene cluster was chosen to predict the configuration of each stereocenter. In‐depth analysis of the corresponding biosynthetic proteins established a hybrid polyketide synthase/nonribosomal peptide synthetase origin of haprolid and allowed for stereochemical assignments. A subsequent total synthesis yielded haprolid and corroborated all predictions made. Intriguingly, haprolid showed cytotoxicity against several cell lines in the nanomolar range whereas other cells were almost unaffected by treatment with the compound. 相似文献
153.
Oier Aizpurua-Olaizola Jone Omar Patricia Navarro Maitane Olivares Nestor Etxebarria Aresatz Usobiaga 《Analytical and bioanalytical chemistry》2014,406(29):7549-7560
High performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) has been successfully applied to cannabis plant extracts in order to identify cannabinoid compounds after their quantitative isolation by means of supercritical fluid extraction (SFE). MS conditions were optimized by means of a central composite design (CCD) approach, and the analysis method was fully validated. Six major cannabinoids [tetrahydrocannabinolic acid (THCA), tetrahydrocannabinol (THC), cannabidiol (CBD), tetrahydrocannabivarin (THCV), cannabigerol (CBG), and cannabinol (CBN)] were quantified (RSD < 10%), and seven more cannabinoids were identified and verified by means of a liquid chromatograph coupled to a quadrupole-time-of-flight (Q-ToF) detector. Finally, based on the distribution of the analyzed cannabinoids in 30 Cannabis sativa L. plant varieties and the principal component analysis (PCA) of the resulting data, a clear difference was observed between outdoor and indoor grown plants, which was attributed to a higher concentration of THC, CBN, and CBD in outdoor grown plants. Graphical Abstract
Representative figure of the identification and quantification process of cannabinoids 相似文献
154.
Débora Bellini Machado Ivone M. Sato Flávia R. O. Silva Vera Lúcia R. Salvador Júlio Takehiro Marumo Nestor Schor Maria Helena Bellini 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):97-102
Following physical examination and radiography analysis, cystotomy was performed to remove a rabbit’s single bladder stone. This rabbit urolith was analyzed by X-ray fluorescence spectrometry (EDXRF) and scanning electron microscopy (SEM). The EDXRF technique was successful for the determination of major elements (Ca, Mg, P, K and S) and presented sufficient sensitivity to also trace elements (Sr, Fe, Cu, V, Cr, Mn, Zn and Pb) determination. The results showed significant quantitative and structural variations among the urolith regions. The EDXRF technique using the fundamental parameters method and SEM attend as complementary techniques that can be useful in the management of urinary stone analysis. 相似文献
155.
156.
Guillaume Levilain Céline Rougeot Frédéric Guillen Jean-Christophe Plaquevent Gérard Coquerel 《Tetrahedron: Asymmetry》2009,20(24):2769-2771
Preferential crystallization is an effective and cheap resolution method which is limited by the nucleation of the antipode, even in the case of in situ racemization. Grinding (during an in situ racemization experiment) was done to promote the crystals stemming from the seeds by enhancing the dissolution step of smaller ones (resulting from nucleation). Thus, the solid remains of a single chirality even if the supersaturation exceeds the Ostwald limit of the antipode. 相似文献
157.
Pietro Aiena Jesú s R. Guillen 《Proceedings of the American Mathematical Society》2007,135(8):2443-2451
A bounded linear operator on a Banach space is said to satisfy ``Weyl's theorem' if the complement in the spectrum of the Weyl spectrum is the set of all isolated points of the spectrum which are eigenvalues of finite multiplicity. In this paper we show that if is a paranormal operator on a Hilbert space, then satisfies Weyl's theorem for every algebraic operator which commutes with .
158.
Flávia Gomes de Góes Rocha Karen Cristina Barbosa Chaves Cinthia Zanini Gomes Camila Barricheli Campanharo Lilia Coronato Courrol Nestor Schor Maria Helena Bellini 《Journal of fluorescence》2010,20(6):1225-1231
Renal cell carcinoma (RCC) remains one of the greatest challenges of urological oncology and is the third leading cause of
death in genitourinary cancers. RCCs are highly vascularized and are amenable to antiangiogenic therapy. Endostatin (ES) is
a fragment of collagen XVIII that possesses antiangiogenic activity. In this study, we examined the potential of erythrocyte
PpIX fluorescence spectroscopy for monitoring the efficacy of antiangiogenic therapy in metastatic renal cell carcinoma (mRCC),
using an orthotopic metastatic mouse model. Balb/C-bearing Renca cells were treated with NIH/3T3-LendSN cells. Lung weight,
nodule area, microvascular area (MVA), and erythrocyte PpIX fluorescence were evaluated. Emission spectra were obtained by
exciting the samples at 405 nm. There was a significant decrease in lung wet weight, lung nodule area and MVA in the treated
group compared to the control group (P < 0.001). Significant differences in autofluorescence shape were observed in the 620–650 nm spectral region. The most intense
fluorescence peak was observed at ∼632 nm. The autofluorescence of the control samples was about 53% higher than that of normal
blood (P < 0.05). In the group treated with ES, the autofluorescence was about 54% lower than in the control group (P < 0.05). Fluorescence intensity was positively correlated with the nodule area (R
2 = 0.8859; P < 0.001) and MVA (R
2 = 0.9431; P < 0.001) in the ES-treated group. These results demonstrate that the spectroscopic analysis method allows a selective detection
of tumor masses. This preliminary study suggests that PpIX fluorescence may be useful as a biomarker for antiangiogenic cancer
therapy. 相似文献
159.
Ruiz-Hernandez SE Grau-Crespo R Almora-Barrios N Wolthers M Ruiz-Salvador AR Fernandez N de Leeuw NH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9828-9833
We have calculated the concentrations of Mg in the bulk and surfaces of aragonite CaCO(3) in equilibrium with aqueous solution, based on molecular dynamics simulations and grand-canonical statistical mechanics. Mg is incorporated in the surfaces, in particular in the (001) terraces, rather than in the bulk of aragonite particles. However, the total Mg content in the bulk and surface of aragonite particles was found to be too small to account for the measured Mg/Ca ratios in corals. We therefore argue that most Mg in corals is either highly metastable in the aragonite lattice, or is located outside the aragonite phase of the coral skeleton, and we discuss the implications of this finding for Mg/Ca paleothermometry. 相似文献
160.
Bassolé IH Lamien-Meda A Bayala B Tirogo S Franz C Novak J Nebié RC Dicko MH 《Molecules (Basel, Switzerland)》2010,15(11):7825-7839
Essential oils from leaves of Lippia multiflora, Mentha x piperita and Ocimum basilicum from Burkina Faso were analysed by GC-FID and GC-MS. Major components were p-cymene, thymol, b-caryophyllene, carvacrol and carvone for L. multiflora, menthol and iso-menthone for M. x piperita and, linalool and eugenol for O. basilicum. The essential oils and their major monoterpene alcohols were tested against nine bacterial strains using the disc diffusion and broth microdilution methods. The essential oils with high phenolic contents were the most effective antimicrobials. The checkerboard method was used to quantify the efficacy of paired combinations of essential oils and their major components. The best synergetic effects among essential oils and major components were obtained with combinations involving O. basilicum essential oil and eugenol, respectively. As phenolic components are characterized by a strong spicy aroma, this study suggests that the selection of certain combinations of EOs could help to reduce the amount of essential oils and consequently reduce any adverse sensory impact in food. 相似文献