全文获取类型
收费全文 | 216篇 |
免费 | 51篇 |
国内免费 | 41篇 |
专业分类
化学 | 107篇 |
晶体学 | 1篇 |
力学 | 15篇 |
综合类 | 1篇 |
数学 | 42篇 |
物理学 | 142篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 27篇 |
2012年 | 2篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 30篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 5篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1959年 | 3篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1948年 | 3篇 |
1947年 | 3篇 |
排序方式: 共有308条查询结果,搜索用时 156 毫秒
271.
Two Novel Copper ( Ⅱ ) Complexes with A Novel Ligand 2,4-Di (2-aminopyridine)- 6-methylpyrimidine 总被引:1,自引:0,他引:1
MAHai-rui WANGYao-yu LIUPing LIDong-sheng SHIQi-zhen LEEGene-hsiang PENGShie-ming 《高等学校化学研究》2005,21(3):365-367
Introduction The design and syntheses of multidentate Ndonor ligands have become the focus of much interest in the chemical field^[1-4] because these ligands can form multinuclear metal compounds, coordination polymers and supramolecular compounds, which play a very important role in the biological systems, magnetic materials, electric materials, 相似文献
272.
具有十二元环开放结构磷酸锌的非水合成与表征 总被引:5,自引:1,他引:4
从非水体系中制备了 Zn2 ( HPO4) 3· H3NCH2 CH2 NH3单晶 ,用 X射线测定了晶体结构 ,用红外光谱 ,DTA-TG等方法对化合物进行了表征 .晶体属三斜晶系 ,P1空间群 .晶胞参数 a=0 .82 1 5( 3 ) nm,b=0 .8557( 3 ) nm,c=0 .9760 ( 3 ) nm,α=93 .8( 3 )°,β=95.3 8( 3 )°,γ=1 0 9.75( 3 )°,V=0 .63 94 nm3,Z=2 ,Dc=2 .50 g·cm- 3.结构中的锌和磷均与氧形成四面体配位 ,Zn O4和 HPO4四面体严格交替排列 ,骨架中的氧分为二桥氧和端氧 ,端氧只向 P原子配位 .三维开放式骨架结构中沿 a轴和 b轴方向有十二元环直孔道 ,质子化的有机胺在 a轴方向的十二元环孔道中 相似文献
273.
WU Xi-Hong GONG Hai-Fang CHEN Fa-Rong ZHUANG Zhi-Xia SUN Da-Hai WANG Xiao-Ru Frank S. C. LEE 《高等学校化学学报》2000,21(Z1):36
Cinnabar, composed mainly of HgS,is often used in Traditional Chinese Medicines as part of the active ingredients in formulated drugs to treat diseases such as epilepsy,sore throat. To gain understanding on the clinical efficacy, safety and toxicity of these TCMs, information regarding not only the total concentrations of the heavy metals, but also their different chemical species is necessary. Therefore, the development of sample treatment and analytical techniques for the accurate determination and speciation of heavy metals in TCM products are of critical importance. The dual objectives of this work are to:(1) develop a leaching procedure using simulated body fluids for bioavailability and toxicity studies, and (2) investigate the possibility of Cinnabar derived mercury to bind with other constitutes in Tian Wan Bu Xin Wan using a sequential extraction scheme. 相似文献
274.
Implication knowledge is useful for drawing conclusions or confirming hypotheses based on some observed data. The challenge here is where/how to derive such knowledge. Traditional knowledge acquisition methodologies or tools have limited power in that they rely on human knowledge engineers' judgements and are applicable only under controlled situations. It would be desirable as well as imperative if we can demonstrate any automatic means of mining such implication knowledge directly from empirical data-this is because in practical applications,data samples are usually available and most importantly the automatically induced implications are less subjective and mathematically sound. As a response to this challenge, our work has developed and validated a new method of automatically discovering implication knowledge by statistically inducing the implication relationships among the data attributes in empirically-obtained sample data. 相似文献
275.
The residues of organochlorine pesticides (OCPs) may occur in Chinese herbal medicines (CHMs). It is needed to analyze CHMs for OCPs to evaluate the risk of CHMs to the health of consumers. The common technique for sample preparation in OCPs determination is Soxhlet extraction[1], which is time-consumable. Meanwhile, up to the present, no standard methods have been reported exactly for the determination of OCPs in Chinese medicines. The goal of the present research is to establish an analytical method suitable for the separation and determination of OCPs in Ganoderma Lucidum (lingzhi) and it's products. 相似文献
276.
NORMAL MODES OF A NON-LINEAR CLAMPED-CLAMPED BEAM 总被引:1,自引:0,他引:1
Non-linear modal analysis approach based on invariant manifold method proposed earlier by Shaw and Pierre (Journal of Sound and Vibration164, 85-124) is utilized here to obtain the non-linear normal modes of a clamped-clamped beam for large amplitude displacements. The results obtained for the fundamental normal mode are compared with the corresponding reported experimental and theoretical studies. The effects of modal coupling are examined in greater detail. The limitation of the present method for analyzing non-linear behavior is highlighted. 相似文献
277.
278.
279.
Applied Physics A 49, No. 5, (1989) 相似文献
280.
Mathematical programming models may contain a great deal of variations in their formulations. The same problem can be modeled as different formulations, or different problems can be modeled as the same formulations. In order to handle these variant formulations efficiently and intelligently, a model management system should be able to eliminate or recognize the variations in model formulations. We analyze possible variations involved in model formulations and categorize them into three types-syntactic, semantic and structural.The first author received support for this work from the 1991 Research Fund at Ajou University. 相似文献