全文获取类型
收费全文 | 459篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
化学 | 365篇 |
力学 | 19篇 |
数学 | 38篇 |
物理学 | 76篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 28篇 |
2019年 | 31篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 44篇 |
2015年 | 23篇 |
2014年 | 26篇 |
2013年 | 65篇 |
2012年 | 35篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 14篇 |
2007年 | 18篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有498条查询结果,搜索用时 15 毫秒
1.
2.
Bosman AW Vestberg R Heumann A Fréchet JM Hawker CJ 《Journal of the American Chemical Society》2003,125(3):715-728
A new strategy for the preparation of functional, multiarm star polymers via nitroxide-mediated "living" radical polymerization has been explored. The generality of this approach to the synthesis of three-dimensional macromolecular architectures allows for the construction of nanoscopically defined materials from a wide range of different homo, block, and random copolymers combining both apolar and polar vinylic repeat units. Functional groups can also be included along the backbone or as peripheral/chain end groups, thereby modulating the reactivity and polarity of defined portions of the stars. This modular approach to the synthesis of three-dimensional macromolecules permits the application of these tailored materials as multifunctional hosts for hydrogen bonding, nanoparticle formation, and as scaffolds for catalytic groups. Examples of applications of the functional stars in catalysis include their use in a Heck-type coupling as well as an enantioselective addition reaction. 相似文献
3.
4.
Atta-ur-Rahman Nasim S Baig I Sener B Orhan I Ayanoglu F Choudhary MI 《Natural product research》2004,18(5):465-471
Two new isoflavones 1 and 2 along with eleven known compounds 3-13, have been isolated for the first time from the rhizomes of Iris soforana. The structures of these compounds were determined on the basis of spectroscopic methods and found to be 5,3'-dihydroxy-4'-methoxy-6,7-methylenedioxyisoflavone (1) (Soforanarin A), and 5,7,5'-trimethoxy-6,3',4'-trihydroxyisoflavone (2) (Soforanarin B). 相似文献
5.
In supersonic adiabatic two-phase flows of steam, under the influence of supersonic acceleration, the fluid loses its equilibrium conditions and becomes supersaturated. Following this condition and to restore the fluid to equilibrium, micro droplets of water form in the absence of any surface or foreign particles. This phenomenon is called homogeneous nucleation and the formed minute small droplets grow along the fluid flow path. The formation of these droplets and their growth causes the release of the latent heat of evaporation to the gas phase particularly in the nucleation region, and results in an increase in the flow pressure which is called the condensation shock. In this paper, and in continuation of the series of papers by the authors, in addition to analytically solving the adiabatic gas-liquid supersonic flow of steam in a convergent-divergent channel, a novel solution to controlling the undesired effects of this pressure rise (condensation shock) is presented. In the proposed method, with the help of cooling the divergent section of the nozzle, the analytical model for the 1D non-adiabatic two-phase steam flows is further developed which shows considerable decrease in the intensity of the formed condensation shock. Also the growth rate of the formed droplets due to the cooling of the steam flow has higher importance than the nucleation itself. 相似文献
6.
Synthesis of diaryl sulfides via nickel ferrite‐catalysed C─S bond formation in green media 下载免费PDF全文
NiFe2O4 magnetic nanoparticles (MNPs) were synthesized, characterized and applied as an air‐stable, inexpensive and magnetically separable nanocatalyst for the synthesis of structurally diverse sulfides. Efficient methodologies were developed for the synthesis of unsymmetric diaryl sulfides via odourless and one‐pot reactions of triphenyltin chloride/S8 or arylboronic acid/S8 as thiolating agents with aryl halides or nitroarenes as starting materials in the presence of base (K2CO3 or NaOH) and NiFe2O4 MNPs as a catalyst in water or poly (ethylene glycol) as solvent at 80–110 °C. Free from ligand and the unpleasant smell of thiols and with the use of magnetically reusable nanocatalyst, green solvents and commercially available and cheap sulfur source and starting materials, these methods are more eco‐friendly and practical than available protocols for the synthesis of sulfides. 相似文献
7.
8.
Mandana Amiri Zahra Tofighi Ali Khodayari Abolfazl Bezaatpour Shabnam Sohrabnezhad Vladyslav Mishyn Rabah Boukherroub Sabine Szunerits 《应用有机金属化学》2020,34(10):e5871
We report a Cu-based metal–organic framework (MOF) decorated by CuO nanostructures as an efficient catalyst for the oxygen evolution reaction (OER). MIL-53(Cu) was synthesized by a hydrothermal approach using 1,4-bezenedicarboxylic acid as organic precursor and further annealed at 300°C to form CuO nanostructures on its surface. The produced electrocatalyst, CuO@MIL-53(Cu), was characterized using various techniques. Under alkaline conditions, the developed electrocatalyst exhibited an overpotential of 801 and 336 mV versus RHE at 10 and 1 mA cm−2, respectively. The reproducibility of the catalytic performance was validated using several electrodes. It was confirmed that the CuO hair-like nanostructures grown on MIL-53(Cu) using thermal treatment exhibit high OER activity, good kinetics and durability. CuO@MIL-53(Cu) is an economic noble-metal-free OER electrocatalyst. It has potential for application as anode material for sustainable energy technologies like batteries, fuel cells and water electrolysis. 相似文献
9.
Amir Shakouri Reza Parvan Nasim Adljouy Jalal Abdolalizadeh 《Biomedical chromatography : BMC》2020,34(1):e4709
Hyaluronidase (Hyal) can be employed to accomplish a diversity of complications related to hyaluronic acid (HA). Hyal contains some classes of catalysts that cleave HA. This enzyme is detected in several human tissues as well as in animal venoms, pathogenic organisms and cancers. Destructive cancer cells regularly increase the CD44 receptor existing in a cell membrane. This receptor acts as an exact receptor for HA, and HA is recognized to motivate the migration, spread, attack and metastasis of cancer cells. Nearly all of the methods used to purify Hyal are highly costly and not proper for industrial applications. This survey aims to review different methods of Hyal purification, which acts as an anticancer agent by degrading HA in tissues and thus inhibiting the CD44–HA interaction. Hyal can be successfully employed in the management of cancer, which is associated with HA–CD44. This review has described different methods for Hyal purification to prepare an origin to develop a novel purification technique for this highly appreciated protein. Using multiple columns is not applicable for the purification of Hyal and thus cannot be used at the industrial level. It is better to use affinity chromatography of anti-Hyal for Hyal with one-step purification. 相似文献
10.
Taghavizadeh Yazdi Mohammad Ehsan Modarres Masoomeh Amiri Mohammad Sadegh Darroudi Majid 《Research on Chemical Intermediates》2019,45(3):1105-1116
Research on Chemical Intermediates - We have synthesized silver nanoparticles (Ag-NPs) via a simple and eco-friendly method through the utilization of aqueous aerial parts of Salvia leriifolia... 相似文献