全文获取类型
收费全文 | 377篇 |
免费 | 29篇 |
国内免费 | 17篇 |
专业分类
化学 | 41篇 |
力学 | 9篇 |
综合类 | 4篇 |
数学 | 26篇 |
物理学 | 8篇 |
综合类 | 335篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 17篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 15篇 |
2012年 | 19篇 |
2011年 | 13篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 24篇 |
2004年 | 34篇 |
2003年 | 13篇 |
2002年 | 21篇 |
2001年 | 23篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有423条查询结果,搜索用时 359 毫秒
1.
2.
Butyltins were analyzed in waters from California river and lake marinas and were detected at the part per trillion (ppt) level in most locations. The tributyltin:dibutyltin (TBT/DBT) ratios in the fresh waters were similar to those in their saline counterparts indicating like rates of degradation in the two salinity regimes. 相似文献
3.
4.
A multiparameter boundary-value problem of fresh infiltration water seepage in a drained fringe above quiescent saline water is solved in the direct statement and studied in detail. 相似文献
5.
We have carried out some photon interaction measurements using 59.54 keV γ-rays from a 241Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation
studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes
as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the
γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation
coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric
studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge
energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture
absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded
scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the
mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with
theoretical values derived from the XCOM package. 相似文献
6.
7.
Atsushi Mizuike 《中国化学会会志》1990,37(2):117-124
Trace element speciation has recently become one of the most important problems in water analysis. Proper combination of preconcentration techniques with instrumental determination methods is essential to speciation analysis, because sensitivity and selectivity of direct determination methods are generally lacking. The present paper describes such preconcentration techniques as filtration, centrifugation, flotation and sorption, which have been developed in the author's laboratory for the speciation of heavy metals in river and pond waters by electron microscopy, X-ray microanalysis and chemical analysis. The application of freeze concentration to the speciation of silica in high-purity waters is also discussed. 相似文献
8.
应用奇象记忆法记忆英语单词的实验研究 总被引:1,自引:0,他引:1
大多数英语学习者都感到识记过的英语单词很容易遗忘且不易回忆。针对这种情况 ,本实验研究在深入了解有关英语单词记忆法的基础上 ,利用奇象记忆法原理作指导进行了一项英语单词记忆实验研究。实验结果表明 :利用奇象记忆法记忆英语单词保持率高于其它记忆方法 相似文献
9.
李益群 《湖南城市学院学报(自然科学版)》2003,12(4):64-65
高校合并重组时,应当十分重视教学档案的收存,使其在人事安排、学校管理、教学改革、教学评估等工作中发挥应有的作用,适应信息时代的要求,为高校教学服务。 相似文献
10.
采用几种不同的溶剂提取连翅中的抗菌有效成分。通过抑菌试验筛选出抗菌作用最强的制剂 ,然后通过对鲜鱼制品的保存试验和新鲜度的常规检测 ,证实该制剂能有效地抑制鱼制品的腐败 ,是鱼制品等食品的一种良好的天然防腐剂 相似文献