全文获取类型
收费全文 | 838篇 |
免费 | 28篇 |
国内免费 | 7篇 |
专业分类
化学 | 525篇 |
晶体学 | 13篇 |
力学 | 41篇 |
数学 | 103篇 |
物理学 | 191篇 |
出版年
2022年 | 16篇 |
2021年 | 26篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 18篇 |
2014年 | 44篇 |
2013年 | 59篇 |
2012年 | 34篇 |
2011年 | 49篇 |
2010年 | 48篇 |
2009年 | 44篇 |
2008年 | 47篇 |
2007年 | 47篇 |
2006年 | 38篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 24篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 14篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 5篇 |
1956年 | 4篇 |
1948年 | 3篇 |
排序方式: 共有873条查询结果,搜索用时 31 毫秒
51.
Palanisamy Shanmugasundaram Periyasamy Murugan Vayalakkavoor T. Ramakrishnan Narayanan Srividya Perumal Ramamurthy 《Heteroatom Chemistry》1996,7(1):17-22
Synthesis of 9-alkyl, 10-alkyl, 9,10-dialkyl, and 10-aryl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)acridinedione (2a–r) are described as a new class of laser dyes. Reactions of diamines with methylene bis(cyclohexane-1,3-dione) yielded the respective bisacridinediones (3a–e). These dyes lase around 478–494 nm and are compared with the standard dye coumarin-102. © 1996 John Wiley & Sons, Inc. 相似文献
52.
Ramajayam Govindan Mohamed El-Sherbiny Khalid Mohamed Morsy Ibraheem Srinivasan Narasimhan Mohamed EL-Dosoky Mohamed Salama Fazil Ahmad Selvaraj Jayaraman Vishnu Priya Veeraraghavan Srinivasan Vengadassalapathy Surapaneni Krishna Mohan Vidhya Rekha Umapathy Gayathri Rengasamy Shazia Fathima Jaffer Hussain Maheshkumar Poomarimuthu Senthilkumar Kalimuthu 《Molecules (Basel, Switzerland)》2022,27(3)
53.
Monitoring the Transition from Spherical to Polymer‐like Surfactant Micelles Using Small‐Angle X‐Ray Scattering 下载免费PDF全文
Dr. Grethe Vestergaard Jensen Dr. Reidar Lund Dr. Jérémie Gummel Dr. Theyencheri Narayanan Prof. Jan Skov Pedersen 《Angewandte Chemie (International ed. in English)》2014,53(43):11524-11528
Despite over a century of modern surfactant science, the kinetic pathways of morphological transitions in micellar systems are still not well understood. This is mainly as a result of the lack of sufficiently fast methods that can capture the structural changes of such transitions. Herein, a simple surfactant system consisting of sodium dodecyl sulfate (SDS) in aqueous NaCl solutions is investigated. Combining synchrotron radiation small‐angle X‐ray scattering (SAXS) with fast stopped‐flow mixing schemes allows monitoring the process where polymer‐like micelles are formed from globular micelles when the salt concentration is suddenly increased. The results show that “worm‐like” micelles are formed by fusion of globular micelles and short cylinders in a fashion that bears similarities to a step‐like polymerization process. 相似文献
54.
Monisha Prasad Selvaraj Jayaraman Mohamed Ahmed Eladl Mohamed El-Sherbiny Mosaab Abdella Ebrahim Abdelrahman Vishnu Priya Veeraraghavan Srinivasan Vengadassalapathy Vidhya Rekha Umapathy Shazia Fathima Jaffer Hussain Kalaiselvi Krishnamoorthy Durairaj Sekar Chella Perumal Palanisamy Surapaneni Krishna Mohan Ponnulakshmi Rajagopal 《Molecules (Basel, Switzerland)》2022,27(5)
Natural products in the form of functional foods have become increasingly popular due to their protective effects against life-threatening diseases, low risk of adverse effects, affordability, and accessibility. Plant components such as phytosterol, in particular, have drawn a lot of press recently due to a link between their consumption and a modest incidence of global problems, such as Type 2 Diabetes mellitus (T2DM), cancer, and cardiovascular disease. In the management of diet-related metabolic diseases, such as T2DM and cardiovascular disorders, these plant-based functional foods and nutritional supplements have unquestionably led the market in terms of cost-effectiveness, therapeutic efficacy, and safety. Diabetes mellitus is a metabolic disorder categoriszed by high blood sugar and insulin resistance, which influence major metabolic organs, such as the liver, adipose tissue, and skeletal muscle. These chronic hyperglycemia fallouts result in decreased glucose consumption by body cells, increased fat mobilisation from fat storage cells, and protein depletion in human tissues, keeping the tissues in a state of crisis. In addition, functional foods such as phytosterols improve the body’s healing process from these crises by promoting a proper physiological metabolism and cellular activities. They are plant-derived steroid molecules having structure and function similar to cholesterol, which is found in vegetables, grains, nuts, olive oil, wood pulp, legumes, cereals, and leaves, and are abundant in nature, along with phytosterol derivatives. The most copious phytosterols seen in the human diet are sitosterol, stigmasterol, and campesterol, which can be found in free form, as fatty acid/cinnamic acid esters or as glycosides processed by pancreatic enzymes. Accumulating evidence reveals that phytosterols and diets enriched with them can control glucose and lipid metabolism, as well as insulin resistance. Despite this, few studies on the advantages of sterol control in diabetes care have been published. As a basis, the primary objective of this review is to convey extensive updated information on the possibility of managing diabetes and associated complications with sterol-rich foods in molecular aspects. 相似文献
55.
The enantioselective cyclization of the prochiral cyclic substrates1 to7 and26, can be carried out in theneat using S-proline as catalyst. The substrates18 to22 and27 could not be cyclized with S-proline but could be cyclized with a mixture of S-phenylalanine and d-camphorsulphonic acid.
The enantioselective cyclization of prochiral acyclic triones45 and47 and also the racemic tricarbonyl compounds54 to57 could also be carried out in theneat using S-proline as catalyst. The optically active enediones obtained in the above cyclizations could also be obtained directly
from 1,3-diones or 2-hydroxymethylene cycloalkanones in a one-pot reaction with methyl vinyl ketone (MVK) and S-proline in
the absence of solvents.13C NMR studies of the one-pot synthesis ofS-11 andS-14 reveal that the annulations involve initial formation of an acid-base complex followed by a Michael reaction and then an
enantioselective cyclization. Such enantioselective cyclizations probably occur on the surface of S-proline crystals. 相似文献
56.
We study fluctuations in the force at the boundary of a 2D granular flow. The forces are mainly impulsive at all flow rates. The probability distribution of impulses decays exponentially at large impulses, as do the forces in a static granular medium. At small impulses, the distribution evolves continuously with flow rate with no indication of the transition from collisional flow to intermittently jamming flows. However, the distribution of the time interval between collisions tends to a power law, P(tau) - tau(-3/2), showing a clear dynamical signature of the approach to jamming. 相似文献
57.
The modification of the extended 1 --> 3 anthraquinonoid monomer 1 by substitution of the central aliphatic moiety with a more rigid, aromatic moiety has allowed the syntheses of the new branched building block 6 possessing multiple, internal redox sites. This monomer was used to generate the first tier, dendritic macromolecules 8 and 9, which incorporate different internal redox centers within the infrastructure as well as the traditional peripheral multifunctionality. Using cyclic voltammetry experiments, the electrochemical response and electronic interactions between the two electroactive sites (the anthraquinonoid and nitroaromatic moieties) of these dendritic constructs were explored. 相似文献
58.
The body of knowledge necessary to observe holographic-moiré patterns in real time is introduced. The basic factors influencing fringe visibility in holographic moiré are analyzed and expressions to evaluate fringe visibility for any given displacement and deformation are given. The application of the introduced theory in the case of real-time observation is discussed. It is shown that the maximum benefits of this technique are achieved by combining it with closed-circuit TV. Several examples of application are given. 相似文献
59.
Hu X Jiao X Narayanan S Jiang Z K Sinha S Lurio LB Lal J 《The European physical journal. E, Soft matter》2005,17(3):353-359
We have used measurements of the absolute intensity of diffuse X-ray scattering to extract the interfacial tension of a buried polymer/polymer interface. Diffuse scattering was excited by an X-ray standing wave whose phase was adjusted to have a high intensity at the polymer/polymer interface and simultaneously a node at the polymer/air interface. This method permits the capillary-wave-induced roughness of the interface, and hence the interfacial tension, to be measured independently of the polymer/polymer interdiffusion. 相似文献
60.
We report a novel application of an ultrathin-polymer-film-based, resonance-enhanced x-ray waveguide as a real-time nanoprobe for elucidating dilute, yet disordered, gold nanoparticles embedded in the polymer matrix. This nanoprobe promises a sensitivity enhancement of several orders of magnitude, hence revealing in real time the lateral nanoparticle distribution with subnanometer spatial resolution. We observed that the motion of the nanoparticles is strongly anisotropic, with in-plane coalescence taking place more rapidly than out-of-plane diffusion, which can ultimately facilitate the formation of two-dimensional structures. 相似文献