全文获取类型
收费全文 | 404篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
化学 | 290篇 |
晶体学 | 11篇 |
力学 | 4篇 |
数学 | 64篇 |
物理学 | 62篇 |
出版年
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 18篇 |
2014年 | 17篇 |
2013年 | 21篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 34篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1961年 | 1篇 |
1888年 | 1篇 |
1887年 | 1篇 |
排序方式: 共有431条查询结果,搜索用时 15 毫秒
31.
In this paper we model concession contracts between a public and a private party, under dynamic uncertainty arising both from the volatility of the cash flow generated by the project and by the strategic behaviour of the two parties. Under these conditions we derive three notions of equilibrium price and apply the model to a case study for one of the most important concession contracts in Italy. 相似文献
32.
Paulo Ventura Araújo 《Elemente der Mathematik》2000,55(4):135-141
33.
In the literature, decision models and techniques for supplier selection do not often consider inventory management of the items being purchased as part of the analysis. In this article, two mixed integer nonlinear programming models are proposed to select the best set of suppliers and determine the proper allocation of order quantities while minimizing the annual ordering, inventory holding, and purchasing costs under suppliers’ capacity and quality constraints. The first model allows independent order quantities for each supplier while the second model restricts all order quantities to be of equal size, as it would be required in a multi-stage (supply chain) inventory model. Illustrative examples are used to highlight the advantages of the proposed models over a previous model introduced in the literature. 相似文献
34.
35.
36.
In this paper we obtain a finite Hilbert-style axiomatization of the implicationless fragment of the intuitionistic propositional calculus. As a consequence we obtain finite axiomatizations of all structural closure operators on the algebra of {–}-formulas containing this fragment. Mathematics Subject Classification: 03B20, 03B22, 06D15. 相似文献
37.
Antonio Selva Pietro Traldi Paolo Ventura Renato Pellegata 《Journal of mass spectrometry : JMS》1986,21(6):343-345
Electron impact mass spectra and collisional activation/mass-analysed ion kinetic energy spectra of some phthalamic acids and their deuterium labelled analogues suggested that the genesis of [M ? 1]+ ions is due to the loss of an aromatic hydrogen ortho to the amidic group, as for aromatic amides and thioamides. 相似文献
38.
Diketopyrrolopyrrole‐Porphyrin Conjugates with High Two‐Photon Absorption and Singlet Oxygen Generation for Two‐Photon Photodynamic Therapy
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)
Julie Schmitt Prof. Valérie Heitz Dr. Angélique Sour Dr. Frédéric Bolze Dr. Hussein Ftouni Prof. Jean‐Francois Nicoud Dr. Lucia Flamigni Dr. Barbara Ventura 《Angewandte Chemie (International ed. in English)》2015,54(1):169-173
Two‐photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two‐photon absorption and singlet‐oxygen generation. Reported here are two new diketopyrrolopyrrole‐porphyrin conjugates as robust two‐photon absorbing dyes with high two‐photon absorption cross‐sections within the therapeutic window. Furthermore, for the first time the singlet‐oxygen generation efficiency of diketopyrrolopyrrole‐containing systems is investigated. A preliminary study on cell culture showed efficient two‐photon induced phototoxicity. 相似文献
39.
Natural estrogens in dairy products: Determination of free and conjugated forms by ultra high performance liquid chromatography with tandem mass spectrometry
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chiara Cavaliere Anna Laura Capriotti Patrizia Foglia Susy Piovesana Roberto Samperi Salvatore Ventura Aldo Lagan 《Journal of separation science》2015,38(20):3599-3606
Natural estrogens are synthesized by mammals in different amounts depending on the developmental stage and pregnancy/lactation period, and they may pass into milk, where they are mostly present as glucuronated and sulfated forms. In modern dairy practices, about 75% of milk is produced from pregnant cows; therefore, the amount of hormones that may pass into milk could be of concern. While estrogen determination in milk has been investigated in depth, the individual determination of estrogens and their conjugated forms in dairy products has not been fully addressed. The aim of this work was to develop and assess a sensitive method, using the peculiar retention properties of graphitized carbon black, to extract natural free estrogens and their major conjugated metabolites, without any enzymatic cleavage, from yogurt, cheese, and butter. The free and conjugated estrogens were eluted in two distinct fractions from the solid‐phase extraction cartridge and analyzed separately by ultra high performance liquid chromatography coupled to tandem mass spectrometry. Recoveries were higher than 80% for all the three sample typologies. The highest matrix effects were observed for butter, which was richest in lipid content, but was below 30%. A survey on some commercial dairy products suggests that production processes decreased estrogen content. 相似文献