全文获取类型
收费全文 | 367篇 |
免费 | 57篇 |
国内免费 | 35篇 |
专业分类
化学 | 253篇 |
晶体学 | 3篇 |
力学 | 10篇 |
综合类 | 1篇 |
数学 | 52篇 |
物理学 | 140篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 11篇 |
2014年 | 27篇 |
2013年 | 20篇 |
2012年 | 33篇 |
2011年 | 32篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 24篇 |
2005年 | 26篇 |
2004年 | 8篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
排序方式: 共有459条查询结果,搜索用时 0 毫秒
31.
Xiaowei Zhang Xinpeng Diao Luya Li Yuqian Zhang Man Liao Guohua Zhang Lantong Zhang 《Journal of separation science》2022,45(14):2458-2477
Ginkgolide B is a dietary diterpene with multiple pharmacological activities. However, current research on ginkgolide B is not comprehensive. The current study analyzed the metabolic profile of ginkgolide B in vivo and in vitro using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. To detect and identify the different metabolites in ginkgolide B, a novel data processing method was used as an assistant tool. A total of 53 different metabolites of ginkgolide B (38 phase I metabolites and 15 phase II metabolites) were detected relative to blank samples. The biotransformation route of ginkgolide B was identified as oxidation, dehydroxylation, hydrogenation, decarbonylation, demethylation, sulfate conjugation, glucose conjugation, methylation, and acetylation. The current study demonstrated a method for rapidly detecting and identifying metabolites and provided useful information to further characterize the pharmacology and mechanism of ginkgolide B. A method for the analysis of other diterpene metabolic components in vivo and in vitro was also established. 相似文献
32.
A phytochemical investigation of Ajuga forrestii Diels led to the isolation of 14 compounds, including eight neo-clerodane diterpenes (1–8), two phytoecdysteroids (9, 11), one stigmastane sterol (10) and three iridoid glycosides (12–14). The structures of these compounds were identified by spectroscopic methods and a comparison of their data with those reported in the literature. This is the first report of compounds 1–14 from A. forrestii. The cytotoxic activities of the aqueous extract of A. forrestii and several compounds have been studied and the chemotaxonomic significance of isolated compounds has also been summarised. 相似文献
33.
利用单-(6-氧-对甲基苯磺酰基)-β-环糊精和2-呋喃甲硫醇反应得到单修饰环糊精, 单[6-硫-6-(2-甲基呋喃)]-β-环糊精. 通过X-ray衍射分析及核磁光谱等方法研究了其在溶液和固态中形成线状超分子的分子自组装行为. 结果表明, 化合物在固态中通过呋喃基团从第二面羟基连续插入到另一个环糊精的空腔, 形成了互锁式螺旋柱状超分子, 而且在溶液中也显示了相似的自组装行为, 其键合常数K及聚合度n分别为450 mol-1·L和1.9. 相似文献
34.
A rapid, sensitive and environmentally friendly method for the analysis of 14 anilines in water samples by dispersive liquid–liquid
microextraction based on solidification of floating organic drop (DLLME-SFO) prior to gas chromatography–mass spectrometry
(GC-MS) was developed and optimized. In the proposed method, cyclohexane was used as the extraction solvent as its toxicity
was much lower than that of the solvent usually used in dispersive liquid–liquid microextraction (DLLME). In the optimized
conditions, the method exhibited good analytical performance. Based on a signal-to-noise ratio of 3, limits of detection for
anilines were in the range of 0.07 to 0.29 μg L−1, and the linear range was 0.5–200 μg L−1 with regression coefficients (r
2) higher than 0.9977. It was efficient for qualitative and quantitative analysis of anilines in water samples. The relative
standard deviations varied from 2.9 to 8.6 % depending on different compounds indicating good precision. Tap water and river
water were selected for evaluating the application to real water samples. The relative recoveries of anilines for the two
real samples spiked with 10 μg L−1 anilines were in the scope of 78.2–114.6 % and 77.3–115.6 %, respectively. 相似文献
35.
Kou-Lin Zhang Yan Chang Li-Min Yuan Guo-Wang Diao 《Journal of solid state chemistry》2011,184(5):1263-1272
One homochiral 1D coordination polymer [Cu(ATIBDC)(2,2′-bipy)]·3H2O·CH3OH (1) and three achiral 1D coordination polymers: [Cd(ATIBDC)(2,2′-bipy)(H2O)]·3H2O (2), [Cd(ATIBDC)(phen)(H2O)]·4H2O (3), and [Mn(ATIBDC)(phen)2]·5H2O (4) have been synthesized and characterized (H2ATIBDC=5-amino-2,4,6-triiodoisophthalic acid, 2,2′-bipy=2,2′-bipyridine, and phen=1,10-phenanthroline). Extended high dimensional network architectures are further constructed with the help of weak secondary interactions, such as hydrogen bonding, aromatic stacking, and halogen bonding (C-I…π and C-I…N/O). Complex 1 crystallizes in the monoclinic system with chiral space group P2(1) and exhibits a right-handed 21 helical chain structure. The homochirality of 1 was confirmed by CD spectrum. Interestingly, two new configurations of decameric water cluster are found in 3 and 4. The acyclic tetrameric cluster (H2O)3(CH3OH) in 1 and (H2O)4 in 2 array into highly ordered helical infinite chains. Thermal stabilities of all the complexes have been studied. Solid state fluorescent properties of the Cd(II) complexes have been explored. 相似文献
36.
首先制备了不同周期的染料掺杂全息液晶/聚合物光栅并进行激光抽运实验, 得到了激光器的调谐曲线,确定了激光器在574 nm到685 nm的谱带里均可以实现激光输出, 即激光器具有110 nm左右的可调谐范围. 之后, 通过温控仪控制样品的温度, 对周期为610 nm的染料掺杂全息液晶/聚合物光栅进行激光抽运, 探测不同温度下的输出激光光谱, 观察到随着温度由20℃升高到65℃, 激光器的中心波长由627.9 nm减小到623 nm, 产生了4.9 nm的波长蓝移. 相似文献
37.
在对不同晶相比硅薄膜的实验研究的基础上,利用有效介质理论估算了这种两相材料的光吸 收系数、迁移率寿命乘积及带隙宽度等参量,计算机模拟了不同结晶比硅薄膜电池的伏安特 性及光谱响应;结果为随着本征层微晶成分的增多,电池的开路电压逐渐减小,短路电流逐 渐增大,本征层的最佳厚度逐渐增大,填充因子有降低的趋势,电池的效率随晶相比的增大 而减小. 电池的光谱响应曲线表明,随晶相比的增大电池的长波响应明显提高. 根据这些模 拟结果,分析讨论了在考虑Lambertian背反射的情况下,非晶/微晶叠层电池的底电池采用 晶相比为40%—50%的两相硅薄膜材料做本征层是最佳选择.
关键词:
两相硅薄膜
太阳能电池
计算机模拟 相似文献
38.
沉积物中石英ESR测年功率饱和效应的初步研究 总被引:2,自引:0,他引:2
介绍了几组沉积物中石英ESR功率饱和效应的基础实验情况,认为在用石英进行ESR测年时,微波功率的选择是一个重要参数,它直接影响累积剂量(AD)的求取,从而严重影响测年结果。在某些特定的地质环境下(如黄土,海洋沉积物),采用比较高的微波功率,可从沉积物石英的E'心得到较老沉积物(大于50万年)可信的ESR年代。 相似文献
39.
40.
Xiaoli Cui Dianlu Jiang Peng Diao Junxin Li Zhenbin Jia Ruting Tong Xinkui Wang 《中国化学会会志》1999,46(4):571-576
The electrochemical behavior of the gold electrode modified by hybrid bilayer membranes in different concentrations of Fe(CN)63?/Fe(CN)64? was investigated by electrochemical impedance spectroscopy and cyclic voltammetry technology. The electron transfer between gold and the redox species separated by the hybrid bilayers assembly was completed by an electron tunneling process. A detailed equivalent circuit for electron transport across the HBMs is proposed. It was found that the apparent effective thickness of the hybrid bilayer membranes was lower than that of the sum of the chain length of octadecanethiol and phospholipid so some possible collapsed sites might exist at the hybrid bilayer membranes. 相似文献