全文获取类型
收费全文 | 243篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 183篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 37篇 |
物理学 | 19篇 |
出版年
2022年 | 11篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 8篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 17篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有247条查询结果,搜索用时 15 毫秒
241.
Andrzej Gobiowski Kazimierz Stoecki Urszula Prokop Alicja Kumierowska Tadeusz Borowiecki Andrzej Denis Czesawa Sikorska 《Reaction Kinetics and Catalysis Letters》2004,82(1):179-189
The influence of K2O on the amounts of chemisorbed hydrogen on a Ni catalyst, the catalyst activity and its resistance to coking were measured.
Introducing potassium into the commercial catalyst (not into the support) appeared to enhance its resistance to coking. The
best catalytic characteristics was noticed for a system containing ~0.5 wt. % K2O. The investigations show a good agreement between the resistance to coking obtained by the temperature-programmed reaction
(TPReaction) method and by the traditional thermogravimetric method.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
242.
Artur Guchowski Ewa Czarniecka-Skubina Jarosawa Rutkowska 《Molecules (Basel, Switzerland)》2020,25(23)
This study was performed in order to assess technological characteristics, proximate composition, fatty acids profile, and microbiological safety of sous-vide processed salmon in comparison with steaming and roasting. The cooking loss was lower in the sous-vide method (6.3–9.1%) than in conventional methods (11.6–16.2%). The preparation of salmon using sous-vide was more time- and energy-consuming than steaming. The dry matter content of the salmon fillets was higher in conventionally processed samples than sous-vide due to the evaporation of water, and it was connected with total protein (r = 0.85) and lipid content (r = 0.73). Analysis of the fatty acids profile only revealed significant differences in six fatty acids. All of the heat treatment methods ensured microbiological safety with regard to coagulase-positive Staphylococcus, E. coli, Listeria monocytogenes, and Salmonella spp. However, in sous-vide (57 °C, 20 min) and steamed samples after storage Enterobacteriaceae bacteria (<104) was detected. Summing up, high parameters of sous-vide salmon cooking, when considering both technological parameters, nutritional value, and microbiological status should be recommended. 相似文献
243.
K. I. Petko T. M. Sokolenko S. Yu. Kot T. A. Kasyanchuk L. M. Yagupol’skii 《Russian Journal of Organic Chemistry》2011,47(4):563-567
Tetrachloro-1,2-difluoroethane reacted with pyrazole and imidazole sodium salts to give mixtures of the corresponding N-(1,2,2-trichloro-1,2-difluoroethyl) derivatives and (E)-1,2-difluoro-1,2-dihetarylethenes. (E)-1,2-Difluoro-1,2-di(3,5-dimethyl-1H-pyrazol-1yl)ethene was also obtained as a result of replacement of chlorine atoms in 1,2-dichloro-1,2-difluoroethene. Analogous
reaction with more nucleophilic imidazole involved replacement of not only chlorine but also fluorine atoms in 1,2-dichloro-1,2-difluoroethene,
yielding tetraimidazolyl-substituted ethylene. 相似文献
244.
Juliusz Pernak Anna ?wierczyńskaMariusz Kot Filip WalkiewiczHieronim Maciejewski 《Tetrahedron letters》2011,52(33):4342-4345
Pyrylium salts represent a new group of ionic liquids (ILs) containing a positive charge on the oxygen atom. The novel ILs were obtained starting with 4-pyrones from petroleum feedstock and renewable resources and sulfonic acids. The use of carboxylic acids instead of salts resulted in the formation of cocrystals. The synthesized pyrylium ionic liquids were stable in air and in contact with water and common organic solvents. The permanganate indices which are characteristic for prepared sulfonates were also investigated. The pyrylium ionic liquids were useful as immobilizers and dissolving agents in hydrosilylation reactions. 相似文献
245.
E. I. Zhmurikov D. Yu. Bolkhovityanov M. F. Blinov A. V. Ishchenko N. Kh. Kot A. T. Titov S. V. Tsybulya Tecchio Luigi 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):442-451
Fine-grained dense graphites of different manufacturers were tested and studied for the purpose of predicting their lifetimes
at high (∼2000°C) temperatures. The tests consisted in sample heating by electric current to a destruction temperature. The
study included a set of electron microscopy, X-ray diffraction, and electrical methods. X-ray diffraction data for initial
samples were compared with data for domestic MPG graphite. Scanning electron microscopy was applied to both initial and heated
samples. The lifetime prediction was based on the Zhurkov classical formula. It was shown that CGD, Carbone Lorraine, and
MPG graphite composites can differ appreciably in both structural characteristics and high-temperature lifetimes. 相似文献
246.
Julia Gostyska Radosaw Pankiewicz Zdzisawa Romanowska-Duda Beata Messyasz 《Molecules (Basel, Switzerland)》2022,27(11)
Allelopathy is an interaction that releases allelochemicals (chemicals that act allelopathically) from plants into the environment that can limit or stimulate the development, reproduction, and survival of target organisms and alter the environment. Lemna minor L. contains chemicals that are allelopathic, such as phenolic acids. Chemical compounds contained in L. minor may have a significant impact on the development and the rate of multiplication and lead to stronger competition, which may enhance the allelopathic potential. Allelopathic potential may exist between L. minor and C. glomerata (L) Kütz. because they occupy a similar space in the aquatic ecosystem, have a similar preference for the amount of light, and compete for similar habitat resources. L. minor and C. glomerata can form dense populations on the water surface. Allelopathy can be seen as a wish to dominate one of the plants in the aquatic ecosystem. By creating a place for the development of extensive mats, an interspecific interaction is created and one of the species achieves competitive success. It is most effective as a result of the release of chemicals by macrophytes into the aquatic environment. Therefore, allelopathy plays a significant role in the formation, stabilization, and dynamics of the structure of plant communities. 相似文献
247.
Valeriy P. Shendrikov Anna S. Alekseeva Erik F. Kot Konstantin S. Mineev Daria S. Tretiakova Abdulilah Ece Ivan A. Boldyrev 《Molecules (Basel, Switzerland)》2022,27(19)
We describe azophenylindane based molecular motors (aphin-switches) which have two different rotamers of trans-configuration and four different rotamers of cis-configuration. The behaviors of these motors were investigated both experimentally and computationally. The conversion of aphin-switch does not yield single isomer but a mixture of these. Although the trans to cis conversion leads to the increase of the system entropy some of the cis-rotamers can directly convert to each other while others should convert via trans-configuration. The motion of aphin-switches resembles the work of a mixing machine with indane group serving as a base and phenol group serving as a beater. The aphin-switches presented herein may provide a basis for promising applications in advanced biological systems or particularly in cases where on demand disordering of molecular packing has value, such as lipid bilayers. 相似文献