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   793篇
  免费   10篇
  国内免费   1篇
化学   371篇
晶体学   11篇
力学   21篇
数学   57篇
物理学   344篇
  2024年   8篇
  2022年   13篇
  2021年   12篇
  2020年   7篇
  2019年   22篇
  2018年   18篇
  2017年   21篇
  2016年   17篇
  2015年   14篇
  2014年   28篇
  2013年   69篇
  2012年   43篇
  2011年   48篇
  2010年   39篇
  2009年   32篇
  2008年   41篇
  2007年   34篇
  2006年   23篇
  2005年   29篇
  2004年   16篇
  2003年   18篇
  2002年   20篇
  2001年   12篇
  2000年   7篇
  1999年   9篇
  1998年   6篇
  1994年   13篇
  1993年   8篇
  1992年   4篇
  1991年   7篇
  1990年   10篇
  1989年   7篇
  1988年   6篇
  1987年   6篇
  1986年   9篇
  1985年   8篇
  1984年   10篇
  1983年   5篇
  1982年   5篇
  1981年   10篇
  1980年   8篇
  1979年   7篇
  1978年   9篇
  1977年   10篇
  1976年   4篇
  1975年   6篇
  1974年   10篇
  1973年   12篇
  1971年   5篇
  1959年   5篇
排序方式: 共有804条查询结果,搜索用时 15 毫秒
31.
This paper reports on the change in the magnetic and the structural properties of Pt/Cr/Co multilayers due to 1 MeV N+-ion irradiation at room temperature. We observe irradiation induced formation of the CoCrPt ternary alloy phase at a fluence of 1×1016 ions cm?2. Phase formation is accompanied by an enhancement in the coercivity. The enhancement in the coercivity is attributed to inhomogeneous alloying and possible mixing-induced strain. These findings are explained in the light of ion beam induced recoil mixing and ionization events.  相似文献   
32.
Journal of Radioanalytical and Nuclear Chemistry - Uranium contamination in the aquatic environment is an emerging concern worldwide. With the development of the global economy, uranium...  相似文献   
33.
The current research focused on the development of Platinum–Rhodium alloy coating (Pt– Rh) on SS304 and its applications in antibacterial studies. Electrodeposition is considered to be one of the most suitable methods because it enhances the therapeutic effects of noble metals (Pt–Rh alloy). The electrodeposited coating is an economical and time-saving alternative to existing coating methods. The newly developed Pt–Rh coating was investigated using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Using the agar Petri plate and broth culture method, the antibacterial effect of the platinum-rhodium alloy was investigated against Gram-negative Escherichia coli and Gram-positive bacteria such as Staphylococcus saprophytes, Bacillus Subtilis, and Enterococcus faecalis. The Pt–Rh alloy coated samples obtained by Direct current (DC) and Pulse coating (PC 50% and PC 75%) were examined for antibacterial study. The PC 75% Pt–Rh alloy coating exhibits significant antibacterial activity, demonstrating a maximum zone of inhibition while leaving the rest of the coated samples by DC and PC 50% duty cycles. The study also found that when the concentration of Pt–Rh solution rises from 5 μL to 15 μL, so does the antibacterial activity. The findings of the study showed that electrodeposited platinum-rhodium alloy metal ions may be handy bacteriostatic in the coming years.  相似文献   
34.
Journal of Thermal Analysis and Calorimetry - Being motivated from the recent developments in biomicrofluidics, a mathematical model is presented to analyze the two-layered electrothermal flow via...  相似文献   
35.
The present study explored the schizonticidal potential of traditionally used Magnolia champaca (L.) Baill. ex. Pierre flowers, identifying constituents of interest. The extraction of phytoconstituents was carried out by microwave-assisted technique, isolated via column chromatography, and characterised by various physicochemical, spectral (IR, 1H-NMR and Mass) and chromatographic (HPTLC) techniques. Both the isolated compounds (parthenolide and costunolide diepoxide) exhibited potent schizonticidal antimalarial activity during primary screening in rodent models, with maximum parasitaemia suppression (85.18% and 83.65%, respectively) at a dose of 20 mg/kg body weight when compared to the standard drugs chloroquine and artesunate. In silico techniques were employed to identify the probable biological target and mechanism of action of these isolated compounds. Molecular docking studies also predicted the binding orientations and multi-targeted action of these compounds, in particular costunolide diepoxide with maximum affinity towards SERCA and DHFR proteins. Additionally, favourable in silico ADMET parameters were envisaged through various computational programmes.  相似文献   
36.
In this article, we have studied the bound anionic states of DNA and RNA nucleobases using the newly developed bt-PNO-EOM-CCSD method and extended basis sets. All of the five nucleobases have a single bound anionic state, which is dipole bound in nature. The electron affinity corresponding to the dipole-bound state is found to be extremely sensitive to the used basis set, and a proper agreement with the available experimental data requires a large basis set with a sufficient number of diffuse functions. Electron correlation plays a major role in stabilizing the bound anionic states of nucleobases. No valence-bound anionic states are observed for any of the nucleobases.  相似文献   
37.
Benzotrithiophene (BTT) isomers were investigated using density functional theory (DFT) and time‐dependent DFT (TD‐DFT) with the aim to explore their structures, linear optical properties, vertical and adiabatic ionization potentials (IPv and IPa), electron affinities (EAv and EAa), and reorganization energies (λ). The computed bond lengths and bond angles at the B3LYP/6–311+G (d, p) level of theory are in good agreement with experimental crystal structures of the known BTTs. These molecules are planar with zero dihedral angle, making them an ideal backbone for high charge mobility. The UV–visible spectra of BTT isomers are in the range 280–360 nm. All BTT isomers have low hole/electron reorganization energies, which is the main characteristic of good hole/electron transporting materials, and these isomers in turn have potential applications in the field of organic materials.  相似文献   
38.
A simple synthesis of chiral spironucleosides and spirobisnucleosides is described. Intramolecular 1,3-dipolar nitrone cycloaddition reaction of d-glucose-derived precursors having olefin at C-3 and nitrone at C-5, C-1, or C-2 (in nor-series) furnished bisisoxazolidinospirocycles 4-7, 11, and 12 in good yields. Reductive ring opening of the isoxazolidine moieties in 4-6 followed by construction of a nucleoside base upon the generated amino groups smoothly yielded spirobisnucleosides 17 and 18 and spironucleosides 20 and 21.  相似文献   
39.
Graphene is an atomic layer thick carbon-based material with unique two-dimensional architecture and extraordinary physiochemical, optical, electrical, and mechanical properties. Graphene and its derivatives show significant promises for the development of nanoporous ultrathin filtration membranes capable of molecular separation properties. Graphene-based nanofiltration membranes featuring distinct laminar structures can offer various novel mass-transport phenomena for purifying water, energy storage and separation, gas separation, and proton conductors. The latest developments in water purification techniques through graphene-based membranes including engineering, design, and fabrication of diverse graphene, graphene-oxide, and graphene-composite membranes are provided here in relation to their application paradigm for purifying water. The critical views on pollutant removal mechanisms for water purification along with optimization measures are specially highlighted. In addition, the challenges, shortcomings, and future prospects are pointed out. The green and large-scale synthesis technology of graphene coupling with advanced membrane fabrication techniques can promote these state-of-the-art nanofiltration membranes for a wide range of applications.  相似文献   
40.
Cadmium selenide quantum dot (CdSe QD) has been used as a dopant in ferroelectric liquid crystal (FLC) 2-methylbutyl 4-(4-decyloxybenzylideneamino) cinnamate (DOBAMBC). Effect of CdSe QD in DOBAMBC on its different electro-optical (E-O) properties has been studied in the SmC* phase. The optical micrographs recorded for the pure and composite material are showing good dispersion of QDs in the FLC matrix. Micrographs of unaligned sample cell revealed that CdSe QDs induce homeotropic alignment of FLC molecules. An appreciable change in the value of E-O parameters like tilt angle, spontaneous polarisation and response time with shifting of SmA–SmC* phase transition temperature has been observed for CdSe QD–DOBAMBC composite. The observed properties of composite system have been discussed on the basis of surface properties of QDs in FLC system.  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