全文获取类型
收费全文 | 256篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 195篇 |
晶体学 | 8篇 |
力学 | 2篇 |
数学 | 16篇 |
物理学 | 46篇 |
出版年
2024年 | 7篇 |
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
1999年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1984年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 31 毫秒
261.
Amit Dubey Braja Gopal Mishra Divya Sachdev M. Sowmiya 《Reaction Kinetics and Catalysis Letters》2008,93(1):149-155
Aluminated mesoporous silica (Al-SBA-15) with different amounts of Al contents were synthesized and used for the synthesis
of 3,4-dihydropyrimidine-2(1H)-ones in the liquid phase, as well as under microwave conditions. The catalytic activity results
showed very high conversion and yields of the products over many substituted aromatic aldehydes. 相似文献
262.
The reaction-based cost effective detection of CN(-) over the most competitive ions, F(-) and Ac(-), by a commercially available dye has been developed. The experimental results are in good agreement with the theory. An application in the form of 'dip-sticks' which provides an instant information, has been demonstrated. 相似文献
263.
Subasa C. Sahoo N. Venkataramani Shiva Prasad Murtaza Bohra R. Krishnan 《Applied Physics A: Materials Science & Processing》2012,106(4):931-935
Cobalt ferrite thin films of different thicknesses were pulsed-laser deposited onto a fused quartz substrate held at ambient
temperature (RT) by varying deposition time. The samples were ex-situ annealed at 750°C in air for 2 hours. All the films
were characterized by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The spontaneous magnetization,
4πM
S
, was found to be 6130 G for the 50 nm thick sample, and this is higher than that for the bulk cobalt ferrite of 5300 G, by
16%. The 4πM
S
was found to decrease with the increase in film thickness and an overall decrease of 32% was observed, when the film thickness
increased from 50 nm to 600 nm. In contrast the films of the same thicknesses, when deposited at substrate temperature of
750°C showed an increase of 4πM
S
with the increase in film thickness. The thickness dependence of 4πM
S
in these nanocrystalline thin films has been explained in terms of the cation distribution and the grain size, which are
sensitive to the substrate temperature during deposition. 相似文献
264.
Vivek P. Chavda Jinal Ajabiya Divya Teli Joanna Bojarska Vasso Apostolopoulos 《Molecules (Basel, Switzerland)》2022,27(13)
The prevalence of obesity and diabetes is an increasing global problem, especially in developed countries, and is referred to as the twin epidemics. As such, advanced treatment approaches are needed. Tirzepatide, known as a ‘twincretin’, is a ‘first-in-class’ and the only dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) receptor agonist, that can significantly reduce glycemic levels and improve insulin sensitivity, as well as reducing body weight by more than 20% and improving lipid metabolism. This novel anti-diabetic drug is a synthetic peptide analog of the human GIP hormone with a C20 fatty-diacid portion attached which, via acylation technology, can bind to albumin in order to provide a dose of the drug, by means of subcutaneous injection, once a week, which is appropriate to its a half-life of about five days. Tirzepatide, developed by Eli Lilly, was approved, under the brand name Mounjaro, by the United States Food and Drug Administration in May 2022. This started the ‘twincretin’ era of enormously important and appealing dual therapeutic options for diabetes and obesity, as well as advanced management of closely related cardiometabolic settings, which constitute the leading cause of morbidity, disability, and mortality worldwide. Herein, we present the key characteristics of tirzepatide in terms of synthesis, structure, and activity, bearing in mind its advantages and shortcomings. Furthermore, we briefly trace the evolution of this kind of medical agent and discuss the development of clinical studies. 相似文献
265.
Indira S. Divya Saravanan Kandasamy Shodai Hasebe Toshiyuki Sasaki Hideko Koshima Krzysztof Wo
niak Sunil Varughese 《Chemical science》2022,13(31):8989
As an emerging class of flexible materials, mechanically bendable molecular crystals are broadly classified as elastic or plastic. Nevertheless, flexible organic crystals with mutually exclusive elastic and plastic traits, with contrasting structural requirements, co-existing under different stress settings are exceptional; hence, it is imperative to establish the concurring factors that beget this rare occurrence. We report a series of halogen-substituted benzil crystals showing elastic bending (within ∼2.45% strain), followed by elastoplastic deformation under ambient conditions. Under higher stress settings, they display exceptional plastic flexibility that one could bend, twist, or even coil around a capillary tube. X-ray diffraction, microscopy, and computational data reveal the microscopic and macroscopic basis for the exciting co-existence of elastic, elastoplastic, and plastic properties in the crystals. The layered molecular arrangement and the weak dispersive interactions sustaining the interlayer region provide considerable tolerance towards breaking and making upon engaging or releasing the external stress; it enables restoring the original state within the elastic strain. Comparative studies with oxalate compounds, wherein the twisted diketo moiety in benzil was replaced with a rigid and coplanar central oxalate moiety, enabled us to understand the effect of the anisotropy factor on the crystal packing induced by the C O⋯C tetral interactions. The enhanced anisotropy depreciated the elastic domain, making the oxalate crystals more prone to plastic deformation. Three-point bending experiments and the determined Young''s moduli further corroborate the co-existence of the elastic and plastic realm and highlight the critical role of the underlying structural elements that determine the elastic to plastic transformation. The work highlights the possible co-existence of orthogonal mechanical characteristics in molecular crystals and further construed the concurrent role of microscopic and macroscopic elements in attaining this exceptional mechanical trait.Structural and mechanical studies of benzil and oxalate crystals highlight the microscopic and macroscopic basis for the co-existence of orthogonal mechanical traits and the elastic to plastic transformation under different stress settings. 相似文献
266.
Deepak Kumar Sharma Athira Suresh Rachana Kumari Sidhikh Kumar Divya Bajpai Tripathy 《Macromolecular Symposia》2024,413(1):2200205
Most people utilize cosmetics to enhance or improve their physical appearance, regardless of their gender, race, or age. Heavy metals (HMs) are impurities or ingredients in many cosmetic products. According to recent studies, these metals can result in a variety of skin and health issues. Numerous studies demonstrate that the mismanaged formulation of such products without sufficient standardization of toxic metals throughout the production process is the primary reason for the high level of HM contamination in the samples. In order to prevent human exposure to such dangerous HMs, it is vital to monitor and manage the fate of HMs in cosmetic items, especially unbranded ones. Due to the wasteful interest of producers in making extra profit, the standards are not being imposed. Moreover, consumers are also ready to compromise with the product due to their unawareness of its hazardous impact on their skin and bodies. Short-term results on their looks may cause fatal effects on their health. Another significant issue that requires attention is the lack of safety regulations in the country for evaluating HMs in cosmetic products. Additionally, there is an urgent need to establish acceptable limits for potential impurities in cosmetic products that must be enforced at local levels. This review provides a comprehensive insight into the content of HMs in cosmetics and their effects on several organs and the site of application. 相似文献
267.
Baardman Lennart Cristian Rares Perakis Georgia Singhvi Divya Skali Lami Omar Thayaparan Leann 《Mathematical Programming》2023,197(1):1-26
Mathematical Programming - In this paper, we present a new framework of bi-level unconstrained minimization for development of accelerated methods in Convex Programming. These methods use... 相似文献