全文获取类型
收费全文 | 1030篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
化学 | 773篇 |
晶体学 | 5篇 |
力学 | 6篇 |
数学 | 79篇 |
物理学 | 209篇 |
出版年
2023年 | 5篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 22篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 32篇 |
2012年 | 43篇 |
2011年 | 64篇 |
2010年 | 34篇 |
2009年 | 33篇 |
2008年 | 69篇 |
2007年 | 72篇 |
2006年 | 43篇 |
2005年 | 49篇 |
2004年 | 58篇 |
2003年 | 63篇 |
2002年 | 39篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 15篇 |
1975年 | 17篇 |
1974年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有1072条查询结果,搜索用时 15 毫秒
61.
Kohara T Koyama T Fujimura M Tanaka H Maeda J Fujimoto T Yamamoto I Arita M 《Chemical & pharmaceutical bulletin》2002,50(6):818-821
The oxidation behavior of Y-931, a potent atypical antipsychotic drug, was compared with that of clozapine and olanzapine. In two enzymatic systems (horseradish peroxidase (HRP)/glutathione (GSH) and HRP/H(2)O(2)/GSH) which generate thiyl radicals, clozapine markedly strengthened the electron paramagnetic resonance (EPR) signal for the radical. Olanzapine, Y-931 and the major metabolites (compounds 1-3) had no or minimal effect on the intensity of this signal. In addition, the redox potential values for the three derivatives were in accord with the EPR spin trapping results. In toxicological experiments in human leukocytes, a concentration-dependent toxicity was observed when neutrophils were incubated with clozapine (1-10 micromol/l) and H(2)O(2) (1 mmol/l). However, Y-931 and olanzapine did not show remarkable toxicity under the conditions. 相似文献
62.
Tsutsumi T Amakura Y Nakamura M Brown DJ Clark GC Sasaki K Toyoda M Maitani T 《The Analyst》2003,128(5):486-492
The chemical-activated luciferase expression (CALUX) assay is a reporter gene assay that detects dioxin-like compounds based on their ability to activate the aryl hydrocarbon receptor (AhR) and thus expression of the reporter gene. In this paper, the CALUX assay was examined for its application in the screening of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in retail fish. The sample extracts were cleaned up on a sulfuric acid-silica gel column followed by an activated carbon column, and the AhR activity of the separated PCDD/F and dioxin-like PCB fractions was determined using the assay. The quantitative limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was 0.98 pg ml(-1) (0.19 pg assay(-1) in the standard curve, corresponding to 0.16 pg g(-1) of CALUX-based toxic equivalency (2,3,7,8-TCDD equivalents) in the tested sample. Recovery tests in which dioxins were added to fish samples resulted in acceptable recoveries (77-117%). The CALUX assay performed well in the analysis of dioxins in fish samples and a comparative study revealed a strong correlation between the CALUX assay and high-resolution gas chromatography-high-resolution mass spectrometry analysis for the determination of PCDD/Fs (r = 0.89) and dioxin-like PCBs (r = 0.91) in retail fish (n = 22). These data revealed that the CALUX assay would be a useful screening method for PCDD/Fs and dioxin-like PCBs in retail fish. 相似文献
63.
64.
65.
Abstract Some dicarhoxyphenylphosphonic acids (DCPPA) were prepared by new process. We succeeded in introducing two carhoxyl groups into the phenyl group of phenylphosphonic acid. The dialkyl iso- and tere-phthalate (DACB) were conveniently hrominated with NBS /H2SO4 system to provide the corresponding hromidcs (DACBB) in good yields and good selectivities. 相似文献
66.
Self‐Assembled Fibers Containing Stable Organic Radical Moieties: Alignment and Magnetic Properties in Liquid Crystals
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hiroki Eimura Yoshikazu Umeta Prof. Dr. Hiroko Tokoro Prof. Dr. Masafumi Yoshio Prof. Dr. Shin‐ichi Ohkoshi Prof. Dr. Takashi Kato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(26):8872-8878
Macroscopically oriented stable organic radicals have been obtained by using a liquid–crystalline (LC) gel composed of an l ‐isoleucine‐based low molecular weight gelator containing a 2,2,6,6‐tetramethylpiperidine 1‐oxyl moiety. The LC gel has allowed magnetic measurements of the oriented organic radical. The gelator has formed fibrous aggregates in liquid crystals via intermolecular hydrogen bonds. The fibrous aggregates of the radical gelator are formed and oriented on cooling by applying a magnetic field to the mixture of liquid crystals and the gelator. Superconducting quantum interference device (SQUID) measurements have revealed that both oriented and nonoriented fibrous aggregates exhibited antiferromagnetic interactions, in which super‐exchange interaction constant J is estimated as ?0.89 cm?1. 相似文献
67.
Pd‐initiated polymerization of diazo compounds bearing dialkoxyphosphinyl group and hydrolysis of the resulting polymers and oligomers to afford phosphonic acid‐containing products
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hiroaki Shimomoto Akira Oda Motoki Kanayama Tomoya Sako Tomomichi Itoh Eiji Ihara Naohiro Hoshikawa Akihiko Koiwai Naoki Hasegawa 《Journal of polymer science. Part A, Polymer chemistry》2016,54(12):1742-1751
Pd‐initiated polymerization and oligomerization of diazo compounds containing a dialkoxyphosphinyl group are described. Polymerization of 2‐dialkoxyphosphinylethyl diazoacetates with π‐allylPdCl‐based initiating systems afforded C? C main chain polymers bearing phosphonate on each main chain carbon atom. The quantitative transformation of the side chain phosphonate to phosphonic acid resulted in the formation of water soluble polymers having the acid groups accumulated around their main chains, although the carbonyl ester linkage in the side chain was cleaved via intramolecular acid‐assisted hydrolysis in water at 80 °C. Pd‐initiated oligomerization of diethyl diazomethylphosphonate yielded an oligomeric product bearing diethoxyphosphiny groups directly attached to its main chain carbons, with unexpected incorporation of azo group in the main chain framework. Hydrolysis of the phosphonate of the oligomer afforded a water‐soluble product, which was revealed to show higher proton conductivity than poly(vinylphosphonic acid) under certain conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1742–1751 相似文献
68.
The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]0.64 and [AN]1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are kd = 2.78 × 10?6 sec?1, ΔH? = 40.8 kcal/mole, and ΔS? = 19.5 cal/mole-deg, respectively. 相似文献
69.
70.
Mitsunori Oda Takanori Kajioka Kazuya Ikeshima Ryuta Miyatake Shigeyasu Kuroda 《合成通讯》2013,43(13):2335-2343
The trimethylsilyl enol ether of l-acetylcyclohepta-1,3,5-triene was transformed to 3,3-dialkyl-1,2,3,8-tetrahydroazulen-1-one by a two-step sequence involving the Mukaiyama aldol reaction with ketones and the subsequent Nazarov cyclization. 相似文献