全文获取类型
收费全文 | 53篇 |
免费 | 17篇 |
国内免费 | 44篇 |
专业分类
化学 | 55篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 16篇 |
物理学 | 34篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 15 毫秒
101.
The microcalorimetric method was used to study the antibacterial activity of two newly synthesized Schiff base compounds (H2L3' and H2L3) on Escherichia coli, trying to obtain the action on both of multiplying bacteria and non-multiplying bacteria at one experiment. The metabolic power-time curves of the bacteria treated with the compounds were obtained, and the thermokinetic parameters were analyzed, from which the antibacterial activities of these compounds were evaluated. The results showed that both of the two compounds have good activity on aerobic multiplying metabolism of E. coli, with the value of ICso 75.8 and 168.8 mg/L respectively, but have not effective action on fermentation metabolism of E. coli. The action of the compounds on the non-multiplying metabolism was investigated by taking the heat output of E. coli in the stationary phase as the guideline of the activity. The value of MSCso (minimum stationary-cidal concentration 50) of them is 118 and 187.5 mg/L, respectively. So, H2L^3 has stronger antibacterial action on E. coli than H2L^3 either for multiplying bacteria or non-multiplying bacteria, and their activity on the aerobic multiplying bacteria of E. coil is mainly shown. It does strongly suggest that the calorimetric method should play an important role in the fight against the drug-resistant bacteria. 相似文献
102.
CONOR P. McGOWAN DAVID R. SMITH JOHN A SWEKA JULIEN MARTIN JAMES D NICHOLS RICHARD WONG JAMES E LYONS LAWRENCE J NILES KEVIN KALASZ JEFFREY BRUST MICHELLE KLOPFER BRADDOCK SPEAR 《Natural Resource Modeling》2011,24(1):117-156
Abstract Adaptive management requires that predictive models be explicit and transparent to improve decisions by comparing management actions, directing further research and monitoring, and facilitating learning. The rufa subspecies of red knots (Calidris canutus rufa), which has recently exhibited steep population declines, relies on horseshoe crab (Limulus polyphemus) eggs as their primary food source during stopover in Delaware Bay during spring migration. We present a model with two different parameterizations for use in the adaptive management of horseshoe crab harvests in the Delaware Bay that links red knot mass gain, annual survival, and fecundity to horseshoe crab dynamics. The models reflect prevailing hypotheses regarding ecological links between these two species. When reported crab harvest from 1998 to 2008 was applied, projections corresponded to the observed red knot population abundances depending on strengths of the demographic relationship between these species. We compared different simulated horseshoe crab harvest strategies to evaluate whether, given this model, horseshoe crab harvest management can affect red knot conservation and found that restricting harvest can benefit red knot populations. Our model is the first to explicitly and quantitatively link these two species and will be used within an adaptive management framework to manage the Delaware Bay system and learn more about the specific nature of the linkage between the two species. 相似文献
103.
本文总结了我们近年米利用压电力显微镜(PFM)研究PMN-30%PT单晶体中铁电畴的结构及其演变的结果.选择PMN-30%PT品体是因为该组分在超声传感器等应用方面具有最大的潜力.铁电畴的观察是基于反压电现象;具体来讲就是当交变电场通过原子力显微镜探针加到晶体表面时,会引起品体表面的起伏振荡,而锁相放大器可以解出该振荡信号的振幅和相位角;其中振幅衬度反映了压电系数d33的大小,而相位衬度则反映了铁电畴的极化方向.文中介绍了平面内以及垂直平面的PFM成像技术,并演示了影响畴的图像的一些因素,其中包括静电倚效应,表层效应和机械抛光的影响.本文还利用有限无模型对PFM成像原理进行了模拟分析.着重研究了晶体中铁电畴的尺寸分布,畴与晶体取向,时间和温度的相关性,以及畴的演变过程. 相似文献
104.
The charge fcrr factor of 28Si and its energy variation are calculatedby using the statistical spectroscopic theory. A qualitative agreemznt between the theoretical results and the experimental data is obtained. 相似文献
105.
As can be expected, textile, tourism and TCM industries will be the most benefited ones after China′s joining of world trade organization. TCM industry possesses great market potential, but it had not been well recognized by international market. The major reasons include the lack of a normal standard for safety, efficacy, homogeneity and stability, the lack of a detailed study on the relationship between chemical components and pharmacological efficacy, and the lack of a quantitative standard for active ingredient, formulation technology, quality control and pharmacological and toxicological studies. 相似文献
106.
Six-carbonringsareusuallypreparedfromDiels-Alder[2rr 4tt]cyclicaddition,DieckmanncondensationorintramolecularMichaelcondensati0n.H0wever,inmostofthecases,thepreparati0nofsubstitUtedcyclohexaneshastounderg0areacti0nsequence.Toreachthisbyaone-stepreaction,sofar,isstillapr0bleminsyntheticorganicchehastry.ThisletterintendstogiveapreliminaryrePortonanewmethodtosynthesizesubstitUtedcyclohexanesthroughsingle-stepintermolecularcondensation0fanaldehydeandamethylketoneinthepresenceofanalkali.Thereact… 相似文献
107.
A technique is developed which gives explicit expressions forthe error terms associated with the asymptotic expansions ofthe Stieltjes transform of f, S f(z) = 0 f(t)/t + z dt. Here z is a complex parameter in the cut plane \arg z\ <, and f(t) is a locally integrable function on [0, ). Near infinitywe assume that f(t) is either algebraically decaying or oscillatory.From the explicit expressions, strict and realistic error boundscan be obtained. Explicit error terms are also given for asymptoticexpansions of Laplace and Fourier transforms of small argument.Our approach is based on the theory of distributions. 相似文献
108.
109.
线型1,2-邻二萘醌-1-肟(1-nqo)钌配合物的合成 总被引:1,自引:0,他引:1
报道了含C_(16)长碳链线型1,2-邻二萘醌-1-肟(1-nqo)钌配合物trans-,cis- 及cis-,cis-[Ru(1-nqo)_2(CO)(spy)] (3)及(4)含C_(18)长碳链线型1-nqo钌配合 物cis-,cis-[Ru(1-nqo)_2(CO)(opy)] (5),trans-,trans-[Ru(1-nqo)_2(opy) _2] (6)的合成。利用红外、FAB质谱、核磁共振氢谱及紫外-可见吸收光谱表征配 合物的结构,利用~1H-~1H偶合二维核磁技术对核磁共振峰进行指认。 相似文献
110.
通过三种构型的1,2-邻二萘醌-2-肟(2-nqo)钌(Ⅱ)羰基配合物trans, cis-(Ru(2-nqo)2(CO)2](1){(trans-NO,cis-O},cis-,trans-[Ru(2-nqo)2(CO)2] (2){cis-NO,trans-O}及cis,-cis-[Ru(2-nqo)2(CO)2](3){(cis-NO,cis-O)}的去羰 基取代反应,合成了含C16长碳链2-nqo钌(Ⅱ)配合物trans-,cis-[Ru(2-nqo)2 (CO)(spy)](4),cis-,trans-(Ru(2-nqo)2(CO)(spy)(5),cis-,cis-[Ru(2-nqo)2 (CO)(spy)](6)及trans-,trans-(Ru(2-nqo)2(spy)2](7){(trans-NO,trans-O)}。 对其进行了红外、紫外-可见质谱及核磁人振测试,并利用^1H-^1H偶合二维核磁 技术对核磁共振峰进行了指认。 相似文献