全文获取类型
收费全文 | 166篇 |
免费 | 5篇 |
专业分类
化学 | 133篇 |
力学 | 3篇 |
数学 | 24篇 |
物理学 | 11篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有171条查询结果,搜索用时 15 毫秒
131.
Polymorphic transition and stability problems during amorphous drug formulation are the major limiting factors in pharmaceutical technology. The purpose of the study was to evaluate the ability of polyglycolized glycerides (Gelucire) in protection of amorphous form of drug during compression and shelf life with lower proportion. Amorphous etoricoxib (AET) was prepared by spray drying technique. Tablets of AET and melt granules of AET (MG-AET) with Gelucire 50/13 were prepared. Tablets parameters like hardness, disintegration and content uniformity were evaluated. Tablets were evaluated immediately after compression and on storage for 3 months at ambient conditions to determine degree of transformation using X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and dissolution profiles. Spray drying yielded the amorphous etoricoxib. Content uniformity in the tablet was in between 95 to 105%. Other parameters like disintegration and hardness were well within the limits. The results showed significant difference in the degree of crystallinity between AET tablet and MG-AET tablet. MG-AET tablet showed absence of crystallinity after 3 months storage. The reason could be formation of hydrogen bonding between the Gelucire and AET. Also Gelucire can be tableted very easily under low pressure and showed elastic recovery. Gelucire yielded a soft embedding during tableting, which prevented the polymorphic transformation. Polyglycolized glycerides (Gelucire 50/13) are able to protect amorphous etoricoxib during compression. As excipient required is low, it became possible to prepare tablet formulation as compared to other excipient like polyvinylpyrrolidon (PVP). 相似文献
132.
To further develop laser-induced breakdown spectroscopy (LIBS) as an analytical technique, it is necessary to better understand the fundamental processes and mechanisms taking place during the plasma evolution. This paper addresses the very early plasma dynamics (first 100 ns) using direct plasma imaging, light scattering, and transmission measurements from a synchronized 532-nm probe laser pulse. During the first 50 ns following breakdown, significant Thomson scattering was observed while the probe laser interacted with the laser-induced plasma. The Thomson scattering was observed to peak 15–25 ns following plasma initiation and then decay rapidly, thereby revealing the highly transient nature of the free electron density and plasma equilibrium immediately following breakdown. Such an intense free electron density gradient is suggestive of a non-equilibrium, free electron wave generated by the initial breakdown and growth processes. Additional probe beam transmission measurements and electron density measurements via Stark broadening of the 500.1-nm nitrogen ion line corroborate the Thomson scattering observations. In concert, the data support the finding of a highly transient plasma that deviates from local thermodynamic equilibrium (LTE) conditions during the first tens of nanoseconds of plasma lifetime. The implications of this early plasma transient behavior are discussed in the context of plasma–analyte interactions and the role on LIBS measurements. 相似文献
133.
Polyion‐Sensitive Polymeric Membrane‐Based Pulstrode as a Potentiometric Detector in Liquid Chromatography
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Potentiometric polyion‐sensitive polymeric membrane electrodes are capable of detecting a wide variety of polyionic macromolecules. Herein, we utilize this lack of selectivity to report the first application of this sensor technology as a detector in liquid chromatography (LC). A reversible polycation pulstrode based on tridodecylmethylammonium‐dinonylnaphthalene sulfonate doped within a polymeric membrane is employed as the LC detector. Poly‐arginines/protamine mixtures are separated by cation‐exchange/affinity chromatography on an immobilized heparin column, with eluted polycation peptide bands clearly observed via the pulstrode detector. The LC‐pulstrode system is further applied to follow the production of different polycation peptides derived from thermolysin catalyzed protamine digestion. 相似文献
134.
A Chatterjee Sushil Kamerkar A K Jethra S Padmini M P Diwakar S S Pande M D Ghodgaonkar 《Pramana》2001,57(1):135-139
Experiments with multi-detector arrays have special requirements and place higher demands on computer data acquisition systems.
In this contribution we discuss data acquisition systems with special emphasis on multi-detector arrays and in particular
we describe a new data acquisition system, AMPS which we have developed recently which is in regular use in experiments at
the Pelletron Laboratory, Mumbai. This includes the in-house development of a dedicated crate controller, PC interface card
and software. 相似文献
135.
136.
137.
Rita M. A. Nayeem Gaur Diwakar G. B. Rout B. K. Pandey A. K. Sarangi 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(3):1413-1415
Geological rock samples collected from Narwapahar uranium mines, UCIL, Jaduguda were analysed for the estimation of uranium concentration (U3O8) by beta–gamma method which is a physical technique and same set of samples were analysed by pellet fluorimetry technique which is a chemical technique. 28 samples were analysed by beta–gamma method and values varied between 240 and 2,500 ppm. Samples were analysed by pellet fluorimetry and values varied between 260 and 2,300 ppm. The results obtained were well comparable by both the techniques. 相似文献
138.
Siva Sankar Murthy Bandaru Shatrughn Bhilare Carola Schulzke Anant R. Kapdi 《Chemical record (New York, N.Y.)》2021,21(1):188-203
Phosphines have, in combination with transition metals, played a pivotal role in the rapid development of efficient catalytic processes. Caged phosphines constitute a class of three‐dimensional scaffolds providing unique control over steric and electronic properties. The versatility of the caged phosphine ligands has been demonstrated elegantly by the groups of Verkade, Gonzalvi as well as Stradiotto. Our research group has also been working extensively for the past several years in the development of 1,3,5‐triaza‐7‐phosphaadamantane‐based caged ligands and in this personal note we have summarized these applications pertaining to the modification of biologically useful nucleosides and heteroarenes. 相似文献
139.
A NIR excitation of Er3+ doped Lithium modified tellurite (Li:TeO2) glass results in antistokes fluorescent emission near 380, 530, 551 and 654 nm (ultraviolet, green and red regions) in addition to NIR Stokes emission. The antistokes emissions are ascribed to transition from the excited 4G11/2, 4S3/2(2H11/2) and 4F9/2 levels in Er3+. The excitation involves three and two incident photons. On excitation with the green laser line at 532 nm also leads to similar emissions. The mechanisms involved in these processes are discussed on the basis of the known energy level diagram and the upconversion efficiency has been calculated. Lifetime of the 4S3/2 level has been measured. The temperature dependence of the upconversion process has also been investigated. 相似文献
140.
A Flexible Composite Mechanical Energy Harvester from a Ferroelectric Organoamino Phosphonium Salt
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)
Thangavel Vijayakanth Dr. Anant Kumar Srivastava Farsa Ram Priyangi Kulkarni Dr. Kadhiravan Shanmuganathan Dr. Balu Praveenkumar Prof. Dr. Ramamoorthy Boomishankar 《Angewandte Chemie (International ed. in English)》2018,57(29):9054-9058
A new binary organic salt diphenyl diisopropylamino phosphonium hexaflurophosphate (DPDP?PF6) was shown to exhibit a good ferroelectric response and employed for mechanical energy harvesting application. The phosphonium salt crystallizes in the monoclinic noncentrosymmetric space group Cc and exhibits an H‐bonded 1D chain structure due to N?H???F interactions. Ferroelectric measurements on the single crystals of DPDP?PF6 gave a well‐saturated rectangular hysteresis loop with a remnant (Pr) polarization value of 6 μC cm?2. Further, composite devices based on polydimethylsiloxane (PDMS) films for various weight percentages (3, 5, 7, 10 and 20 wt %) of DPDP?PF6 were prepared and examined for power generation by using an impact test setup. A maximum output peak‐to‐peak voltage (VPP) of 8.5 V and an output peak‐to‐peak current (IPP) of 0.5 μA was obtained for the non‐poled composite film with 10 wt % of DPDP?PF6. These results show the efficacy of organic ferroelectric substances as potential micropower generators. 相似文献