首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   364篇
  免费   7篇
  国内免费   1篇
化学   217篇
晶体学   1篇
力学   14篇
数学   34篇
物理学   106篇
  2024年   2篇
  2023年   5篇
  2022年   35篇
  2021年   40篇
  2020年   19篇
  2019年   12篇
  2018年   13篇
  2017年   17篇
  2016年   14篇
  2015年   9篇
  2014年   13篇
  2013年   26篇
  2012年   14篇
  2011年   32篇
  2010年   15篇
  2009年   17篇
  2008年   11篇
  2007年   17篇
  2006年   13篇
  2005年   1篇
  2004年   1篇
  2003年   3篇
  2002年   5篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1992年   2篇
  1991年   3篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   3篇
  1984年   1篇
  1982年   2篇
  1979年   2篇
  1977年   1篇
  1976年   3篇
  1974年   1篇
排序方式: 共有372条查询结果,搜索用时 15 毫秒
11.
Microwave irradiation (MI) process characteristically enables extremely rapid “in‐core” heating of dipoles and ions, in comparison to conventional thermal (conductance) process of heat transfer. During the process of nanoparticles synthesis, MI both modulates functionality behaviors as well as dynamic of reaction in favorable direction. So, MI providing a facile, favorable and alternative approach during nanoparticles synthesis nanoparticles with enhanced catalytic performances. Although, conventionally used reducing and capping reagents of synthetic origin, are usually environmentally hazardous and toxic for living organism. But, in absence of suitable capping agent; stability, shelf life and catalytic activity of metallic nanoparticles adversely affected. However, polymeric templates which emerged as suitable choice of agent for both reducing and capping purposes; bearing additional advantages in terms of catalyst free one step green synthesis process with high degree of biosafety and efficiency. Another aspect of current works was to understand role of process variables in growth mechanism and catalytic performances of microwave processed metallic nanoparticles, as well as comparison of these parameters with conventional heating method. However, due to poor prediction ability with previously published architect OFAT (One factor at a time) design with these nanoparticles as well as random selection of process variables with their different levels, such comparison couldn't be possible. Hence, using gum Ghatti (Anogeissus latifolia) as a model bio‐template and under simulated reaction conditions; architect of QbD design systems were integrated in microwave processed nanoparticles to establish mechanistic role these variables. Furthermore, in comparison to conventional heating; we reported well validated mathematical modeling of process variables on characteristic of nanoparticles as well as synthesized gold nanoparticles of desired and identical dimensions, in both thermal and microwave‐based processes. Interestingly, despite of identical dimension, MI processed gold nanoparticles bearing higher efficiency (kinetic rate) against remediation of hazardous nitro dye (4‐nitrophenol), into safer amino (4‐aminophenol) analogues.  相似文献   
12.
13.
Journal of Solid State Electrochemistry - Graphene nanosheets (G) and pure, as well as doped Mg-, Mn-, V-Li4Ti5O12, spinel structure have been synthesized. As-prepared materials were characterized...  相似文献   
14.
Silver chloride was found to be stable even after calcination at 650 °C for 10 h. SEM studies revealed the morphology of silver chloride as hexagonal particles. TEM studies show the size of silver chloride particles to have an average size of 6–7 nm. Thermal studies suggest that silver chloride nanoparticles behave like ionic liquid or molten salt in the range of 455–650 °C.  相似文献   
15.
Organotin complexes have been synthesized by refluxing 2-mercapto-5-methyl benzimidazole with R2SnCl2/R3SnCl (R = Me, n-Bu, Ph) in 1:1 molar ratio in the first step. In the second step, synthesized organotin(IV) complexes were treated with CS2 and R2SnCl2/R3SnCl/PdCl2 to yield homo- and heterobimetallic complexes. The composition of the synthesized complexes, the bonding behavior of the donor groups, and structural assignments were studied by elemental analysis and different spectral techniques, including IR and multinuclear NMR (1H, 13C). The IR data shows bidentate nature of the ligand which is also confirmed by semiempirical study, while NMR data confirms the four-coordinated geometry in solution. The free ligand and its respective homo- and heterobimetallic complexes were screened in vitro against a number of microorganisms to assess their biocidal properties. The biological activity data show that complexes exhibits significant antibacterial and antifungal activities as compared to ligand with few exceptions.  相似文献   
16.
Cellulose - Microcrystalline cellulose (MCC) is a semi-crystalline material with inherent variable crystallinity due to raw material source and variable manufacturing conditions. MCC crystallinity...  相似文献   
17.
Electromagnetic interference (EMI) shielding has become a phenomenon of great concern and there is growing demand towards the synthesis of materials with better EMI shielding effectiveness (EMI SE). This work highlights the preparation of Polyaniline-Yttrium Oxide (PANI-Y2O3) composites for EMI shielding applications in the frequency range from 12.4 to 18 GHz (Ku-band). The structure and morphology of the composites were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). EMI SE, microwave absorption and reflection, dielectric properties of the composites are discussed in detail. All the computations were based on microwave scattering parameters measured by transmission line waveguide technique. The observed results show absorption dominant EMI shielding in these composites with EMI SE of ?19 to ?20 dB, which mainly depends on the dielectric loss of the composites. Through the results of our observations, we propose these composites to be potential materials for microwave absorption and EMI shielding applications.  相似文献   
18.
More than 90% of diabetic patients suffer from sexual dysfunction, including diminished sperm count, sperm motility, and sperm viability, and low testosterone levels. The effects of Momordica charantia (MC) were studied by estimating the blood levels of insulin, glucose, glycosylated hemoglobin (HbA1c), testosterone (TST), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in diabetic rats treated with 250 and 500 mg/kg b.w. of the total extract. Testicular antioxidants, epididymal sperm characteristics, testicular histopathology, and lesion scoring were also investigated. Testicular mRNA expression of apoptosis-related markers such as antiapoptotic B-cell lymphoma-2 (Bcl-2) and proapoptotic Bcl-2-associated X protein (Bax) were evaluated by real-time PCR. Furthermore, caspase-3 protein expression was evaluated by immunohistochemistry. MC administration resulted in a significant reduction in blood glucose and HbA1c and marked elevation of serum levels of insulin, TST, and gonadotropins in diabetic rats. It induced a significant recovery of testicular antioxidant enzymes, improved histopathological changes of the testes, and decreased spermatogenic and Sertoli cell apoptosis. MC effectively inhibited testicular apoptosis, as evidenced by upregulation of Bcl-2 and downregulation of Bax and caspase-3. Moreover, reduction in apoptotic potential in MC-treated groups was confirmed by reduction in the Bax/Bcl-2 mRNA expression ratio.  相似文献   
19.
Faisal  Muhammad  Saeed  Aamer  Shahzad  Danish  Dar  Parsa  Larik  Fayaz Ali 《Molecular diversity》2020,24(2):571-592
Molecular Diversity - Aldehydes and ketones are parts of millions of compounds and are important classes of chemicals which serve as important precursors for the synthesis of library of compounds....  相似文献   
20.
The possibility of simultaneous induction and detection, with an intense single mode ir laser, of the Autler Townes splittings of certain rovibrational lines in diatomics is discussed. A model based on the accurately known molecular parameters and dipole matrix elements of CO is used to exhibit the power splitting effect for the case of two quantum excitation. The power splitting effect, which exhibits a threshold as a function of laser intensity is clearly discernable in both the two and one quantum absorption profiles as well as in the total absorption spectrum. Using a simple qualitative rule we predict that such rovibrational line splittings should also be observable in an analogous set of transitions in other diatomics.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号