全文获取类型
收费全文 | 178篇 |
免费 | 26篇 |
国内免费 | 59篇 |
专业分类
化学 | 168篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 11篇 |
物理学 | 72篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 19篇 |
2007年 | 28篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
排序方式: 共有263条查询结果,搜索用时 234 毫秒
1.
2.
维库溴铵、罗库溴铵和泮库溴铵是一类广泛使用的非去极化肌松剂,使用过程中引起过敏反应甚至死亡的情况时有发生,快速检测血液中该类肌松剂的浓度,可为临床早期诊断提供有价值的信息。该类肌松剂为强极性的季铵盐类化合物,在反相色谱柱上难以保留,主要采用离子对色谱法进行分离。采用离子对色谱法时,加入的离子对试剂有离子抑制作用,可降低质谱灵敏度,还会污染质谱系统。该文建立了高效液相色谱-串联质谱(HPLC-MS/MS)同时检测血液中3种季铵盐类肌松剂的检测方法。血液样品经稀释、高速离心后,上清液过Bond Elut AL-N固相萃取柱净化,用0.45 μm的微孔滤膜过滤后检测。采用ZIC-cHILIC色谱柱(50 mm×2.1 mm, 3.0 μm)分离,以乙腈和0.1%甲酸水溶液为流动相,梯度洗脱,在ESI+、多反应检测(MRM)模式下检测。3种季铵盐类肌松剂在血液中的基质效应为88.1%~95.4%,在各自范围内线性关系良好,相关系数(R2)均大于0.996,检出限为0.2~0.8 ng/mL,定量限为0.5~2.0 ng/mL,加标回收率为92.8%~110.6%,相对标准偏差(RSD)为3.2%~9.4%。该方法灵敏度高,准确性好,操作简便,可用于血液样品中维库溴铵、罗库溴铵和泮库溴铵的快速检测。 相似文献
3.
4.
Chaotic ant swarm optimization (CASO) is a powerful chaos search algorithm for optimization problems, but it is often easy to be premature convergence. To overcome the weakness, this paper presents a CASO with passive congregation (CASOPC). Passive congregation is one type of biological information sharing mechanisms that allow animals to aggregate into groups and help to enhance the exploitation of animals. By introducing passive congregation strategy into the CASO, a modified evolution equation based on the CASO is proposed in the CASOPC. The modified evolution equation cannot only employ the parallel search of all ants and the well exploration ability of the CASO, but also stress and control the exploitation by passive congregation coefficient c in the stage of evolution. Due to linearly increasing c in the CASOPC, the exploration and exploitation ability of ants are well balanced so that premature convergence can be avoided and good performance can be achieved. In order to estimate the capability of the CASOPC, it is tested with a set of 5 benchmark functions with 30 dimensions and compared to the CASO. Experimental results indicate that the CASOPC improves the search performance on the benchmark functions significantly. 相似文献
5.
Polycrystalline alumina (Al2O3) substrates, found in many electronic devices and proposed as dosemeters in emergency situations, were invstigated using a scanning electron microscope (SEM) equipped with cathodoluminescence (CL) and elemental analysis probes. The characteristics of the CL spectra, surface morphology, and impurity content of the Al2O3 substrates were examined and compared with those of single crystal dosimetry-grade Al2O3:C. Whereas the CL spectrum, measured from 250 to 800 nm, for the Al2O3:C, contained resolved bands located at ∼340 nm and at ∼410 nm, the spectrum measured with the Al2O3 substrate was significantly broader, extending from ∼250 to ∼450 nm, and also included a narrow band at 695 nm. While it is likely that the accepted model of recombination at F+ (∼340 nm) and F (∼410 nm) in Al2O3:C also applies to the substrate, it is suggested that the presence of impurities within the alumina give rise to additional recombination centres. The 695 nm emission has been assigned to a Cr3+ ion impurity in previous work on alumina and a band indicated at ∼300 nm may be associated with Mg2+ or Ca2+, the presence of which was confirmed by elemental mapping. Comparison of the spatial distribution of CL with the surface morphology and elemental composition of the samples indicates that the components of the emission spectrum can be qualitatively correlated with impurity content and morphological features of the samples. 相似文献
6.
Hongren Chen Fengying Hong Dr. Guang Shao Dr. Deyu Hang Lei Zhao Prof. Zhuo Zeng 《化学:亚洲杂志》2014,9(12):3418-3430
By using three synthetic protocols, a series of fluorocarbon and hydrocarbon N‐heterocyclic imidazole‐based liquid crystals (LCs) and related imidazolium‐based ionic liquid crystals (ILCs) have been prepared. The ring size of the N‐heterocycle and the length of the N‐terminal chain (on the imidazolium unit in the ILCs) were modified, and the influence of these structural parameters on liquid‐crystal phases was investigated by means of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). These new ILCs exhibit a disordered smectic phase (SmA), good thermal stabilities, a broad smectic phase range, a high dipole moment, relatively low melting points, but high clearing points and strong emission fluorescence relative to imidazole‐based LCs. These encouraging results have led us to believe these fluorocarbon and hydrocarbon N‐heterocyclic imidazole‐based LCs and related imidazolium‐based ILCs could be used as new liquid‐crystalline materials. 相似文献
7.
8.
Xinhui Si Liancun ZhengXinxin Zhang Min LiJianhong Yang Ying Chao 《Applied mathematics and computation》2011,218(7):3515-3521
In this paper, the asymptotic solution for the similarity equation of the laminar flow in a porous pipe with suction at expanding and contracting wall has been obtained using the singular perturbation method. However, this solution neglects exponentially small terms in the matching process. To take into account these exponentially small terms, a method involving the inclusion of exponentially small terms in a perturbation series was used to find the two solutions analytically. The series involving the exponentially small terms and expansion ratio predicts dual solutions. Furthermore, the result indicates that the expansion ratio has much important influence on the solutions. When the expansion ratio is zero, it is a special case that Terrill has discussed. 相似文献
9.
《中国化学快报》2020,31(11):2960-2964
Three fluorescent BINOL-Si complexes (FS1, FS2 and FS3) were rationally designed and synthesized to detect diethyl chlorophosphate (DCP), a mimic of lethal nerve agents. These three fluorescent probes showed green, yellow and orange fluorescence, respectively. Moreover, the series of fluorescent probes has the characteristics of fast response time (≤ 4 s), low detection limit (0.0097 μmol/L), high sensitivity and naked eye detection. More important, a fiber optic sensor capable of detecting DCP vapor in real time was also prepared for the first time, the lowest detection limits (down to 4.4 ppb) were all lower than that of the IDLH (immediately dangerous to life or health) concentration of Sarin (7.0 ppb). 相似文献
10.