全文获取类型
收费全文 | 758篇 |
免费 | 38篇 |
国内免费 | 3篇 |
专业分类
化学 | 493篇 |
晶体学 | 5篇 |
力学 | 17篇 |
数学 | 172篇 |
物理学 | 112篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 27篇 |
2019年 | 29篇 |
2018年 | 20篇 |
2017年 | 7篇 |
2016年 | 30篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 38篇 |
2012年 | 41篇 |
2011年 | 52篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 32篇 |
2007年 | 18篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1995年 | 7篇 |
1992年 | 11篇 |
1987年 | 4篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1969年 | 7篇 |
1964年 | 4篇 |
1944年 | 6篇 |
1943年 | 7篇 |
1912年 | 4篇 |
1911年 | 4篇 |
1910年 | 6篇 |
1907年 | 4篇 |
1906年 | 4篇 |
排序方式: 共有799条查询结果,搜索用时 15 毫秒
161.
Heterologous Expression,Biosynthetic Studies,and Ecological Function of the Selective Gq‐Signaling Inhibitor FR900359
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Max Crüsemann Raphael Reher Isabella Schamari Dr. Alexander O. Brachmann Dr. Tsubasa Ohbayashi Markus Kuschak Dr. Davide Malfacini Alexander Seidinger Marta Pinto‐Carbó René Richarz Tatjana Reuter Dr. Stefan Kehraus Dr. Asis Hallab Misty Attwood Prof. Dr. Helgi B. Schiöth Dr. Peter Mergaert Dr. Yoshitomo Kikuchi Prof. Dr. Till F. Schäberle Prof. Dr. Evi Kostenis Prof. Dr. Daniela Wenzel Prof. Dr. Christa E. Müller Prof. Dr. Jörn Piel Prof. Dr. Aurélien Carlier Prof. Dr. Leo Eberl Prof. Dr. Gabriele M. König 《Angewandte Chemie (International ed. in English)》2018,57(3):836-840
The cyclic depsipeptide FR900359 (FR), isolated from the tropical plant Ardisia crenata, is a strong and selective inhibitor of Gq proteins, making it an indispensable pharmacological tool to study Gq‐related processes, as well as a promising drug candidate. Gq inhibition is a novel mode of action for defense chemicals and crucial for the ecological function of FR, as shown by in vivo experiments in mice, its affinity to insect Gq proteins, and insect toxicity studies. The uncultured endosymbiont of A. crenata was sequenced, revealing the FR nonribosomal peptide synthetase (frs) gene cluster. We here provide a detailed model of FR biosynthesis, supported by in vitro enzymatic and bioinformatic studies, and the novel analogue AC‐1, which demonstrates the flexibility of the FR starter condensation domains. Finally, expression of the frs genes in E. coli led to heterologous FR production in a cultivable, bacterial host for the first time. 相似文献
162.
Perspectives on bioenergy and biotechnology in Brazil 总被引:4,自引:0,他引:4
Adalberto Pessoa-Jr Inêes Conceição Roberto Marcelo Menossi Raphael Revert dos Santos Sylvio Ortega Filho Thereza Christina Vessoni Penna 《Applied biochemistry and biotechnology》2005,121(1-3):59-70
Brazil is one of the world’s largest producers of alcohol from biomass at low cost and is responsible for more than 1 million
direct jobs. In 1973, the Brazilian Program of Alcohol (Proalcool) stimulated the creation of a bioethanol industry that has
led to large economic, social, and scientific improvements. In the year 1984, 94.5% of Brazil’s cars used bioethanol as fuel.
In 2003/2004, 350.3 million of sugarcane produced 24.2 million t of sugar and 14.4 billion L of ethanol for an average 4.3
million cars using ethanol. Since its inception, cumulative investment in Proalcool totals US$11 billion, and Brazil has saved
US$27 billion in oil imports. The ethanol production industry from sugarcane generates 152 times more jobs than would have
been the case if the same amount of fuel was produced from petroleum, and the use of ethanol as a fuel is advantageous for
environmental reasons. In 2003, one of the biggest Brazilian ethanol industries started consuming 50% of the residual sugarcane
bagasse to produce electrical energy (60 MW), a new alternative use of bioenergy for the Brazilian market. Other technologies
for commercial uses of bagasse are in development, such as in the production of natural fibers, sweeteners (glucose and xylitol),
single-cell proteins, lactic acid, microbial enzymes, and many other products based on fermentations (submerged and semisolid).
Furthermore, studies aimed at the increase in the biosynthesis of sucrose and, consequently, ethanol productivity are being
conducted to understand the genetics of sugarcane. Although, at present, there remain technical obstacles to the economic
use of some ethanol industry residues, several research projects have been carried out and useful data generated. Efficient
utilization of ethanol industry residues has created new opportunities for new value-added products, especially in Brazil,
where they are produced in high quantities. 相似文献
163.
The synthesis, characterization and X‐ray crystal structures of two 2‐naphthyl‐substituted pyrazoles ‐ 3‐(2‐naphthyl) pyrazole ( 1 ) and 5‐(2‐naphthyl)‐3‐trifluoromethyl‐pyrazole ( 3 ) ‐ are reported. In addition, the isolation and structural characterization of 5‐hydroxy‐3‐(2‐naphthyl)‐5‐trifluoromethyl‐4,5‐dihydropyrazole ( 2 ), an intermediate of the synthesis of 3 , is included. Two simple methods of dehydration of 2 are also presented. 相似文献
164.
Caterina Minelli Christoph Frommen Christian Hinderling Raphael Pugin Harry Heinzelmann Martha Liley 《Colloid and polymer science》2006,284(5):482-488
Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin
electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer
thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer
films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration
of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which
demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density
of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are
induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under
certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates. 相似文献
165.
Anomalous dissociative behavior of the major glycosylated component of the cellulosome of clostridium thermocellum 总被引:1,自引:0,他引:1
Ely Morgenstern Edward A. Bayer Raphael Lamed 《Applied biochemistry and biotechnology》1991,30(2):129-136
The cellulosome of Clostridium thermocellum is a highly cohesive multienzyme complex that is capable of completely solubilizing insoluble cellulose. One of the major cellulosomal components, the glycosylated S1 subunit, is believed to play an important structural role and normally migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an Mr of 210,000. It is shown here that by simply altering the conditions (pH or ionic strength) of the environment prior to electrophoresis, a different migratory profile for S1 emerges, yielding a collection of bands, all of which migrate faster than the parent band. The original electrophoretic behavior of S1 can be reproduced on restoration of the original pH and ionic strength. These results may bear important significance for the physiological role of the S1 subunit in facilitating the observed synergistic action of the other (cellulolytic) components of the cellulosome. 相似文献
166.
We prove for a general class of Gibbsian Random Field on that the set of tempered Gibbs states is compact. This class contains the Euclidean random fields. Moreover if the interaction is attractive, there is a unique minimal and maximal Gibbs state – and +×± are unique translation invariant ant and have the global Markov property. We also prove that uniqueness of the tempered Gibbs state is equivalent to the magnetizationsm
±=±(q
x
) being equal which is true if the pressure is differentiable. 相似文献
167.
Raphael Ed. Liesegang 《Fresenius' Journal of Analytical Chemistry》1943,126(5):172-177
Zusammenfassung Die Art des Papiers kann den Ausfall der Capillaranalyse von Farbstoffgemischen usw. erheblich beeinflussen. Man kann aus den Bildern oft Schlüsse ziehen auf die Eigenschaften des Papiers. Einfluß auf den Ausfall der Capillaranalyse haben auch der Gehalt der aufsteigenden Flüssigkeiten an Alkohol, Schutzkolloiden, ihr pH-Wert usw.Ein abgeändertes Verfabren besteht darin, einen Tropfen der Farbstofflösung auf Papier eintrocknen und dann reines Wasser oder andere Lösemittel hochsteigen zu lassen. Diese Begrenzung der Menge des capillar Aufsteigenden schafft eine ähnliche Wirkung wie die Entwicklung in der Chromatographie. Genügt das Auseinanderziehen der einzelnen Farbbänder noch nicht, so kann man nachträglich senkrecht dazu nochmals eine Flüssigkeit hochsteigen lassen. 相似文献
168.
Edisher G. Kvesitadze Tamara B. Lomitashvili Maia P. Khutsishvili Raphael Lamed Edward A. Bayer 《Applied biochemistry and biotechnology》1995,50(2):137-143
A heat-stable enzyme was isolated from the cellulase complex of a thermophilic strain of the micromyceteThielavia terrestris. The purified enzyme exhibited both endoglucanase and xylanase activities and had a mol mass of 69,000 Daltons and an isoelectric
point of 6.4. When the cells were grown at 48°C, the initial activity of the purified enzyme using carboxymethylcellulose
as a substrate was 150 nkat/mg and the Michaelis constant was 6.6 g/L. The heat stability of the enzyme was high, losing only
20% of the initial activity after a 6-h incubation at 65 °C. When cultures were grown on microcrystalline cellulose and xylose
was added after 48 h of growth, endoglucanase and xylanase activities were more than doubled. Similar increases in these activities
were observed by growing the cultures on straw. 相似文献
169.
A classical electromagnetic calculation of the lifetime of an emitting electric dipole near a material slab is presented. The lifetime is deduced from the imaginary part of the electric field Green's tensor associated with the stratified medium. The method is applied not only to the well known case of metallic reflectors, but also to magnetic reflectors and to negative refractive index slabs. The frequency dependence of the nonradiative decay rate at small distances is analyzed and interpreted in terms of the surface polariton modes of the slab. 相似文献
170.
Marcel Ritter Vincensius S. P. Oetama Daniel Schulze Katrin Muetzlaff Anja K. Meents Dr. Raphael A. Seidel Dr. Helmar Görls Prof. Dr. Matthias Westerhausen Prof. Dr. Wilhelm Boland Prof. Dr. Georg Pohnert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6205-6213
The degradation of chlorophyll, the omnipresent green pigment, has been investigated intensively over the last 30 years resulting in many elucidated tetrapyrrolic degradation products. With a comparison to the degradation of the structurally similar heme, we hereby propose a novel additional chlorophyll degradation mechanism to mono- and dipyrrolic products. This is the first proof of the occurrence of a family of mono- and dipyrrols in leaves that are previously only known as heme degradation products. This product family is also found in spit and feces of herbivores with specific metabolomic patterns reflecting the origin of the samples. Based on chromatographic and mass spectrometric evidence as well as on mechanistic considerations we also suggest several tentative new degradation products. One of them, dihydro BOX A, was fully confirmed as a novel natural product by synthesis and comparison of its spectroscopic data. 相似文献