全文获取类型
收费全文 | 4671篇 |
免费 | 84篇 |
国内免费 | 10篇 |
专业分类
化学 | 3255篇 |
晶体学 | 21篇 |
力学 | 76篇 |
数学 | 1015篇 |
物理学 | 398篇 |
出版年
2020年 | 34篇 |
2019年 | 37篇 |
2016年 | 83篇 |
2015年 | 60篇 |
2014年 | 42篇 |
2013年 | 135篇 |
2012年 | 106篇 |
2011年 | 162篇 |
2010年 | 114篇 |
2009年 | 128篇 |
2008年 | 148篇 |
2007年 | 147篇 |
2006年 | 148篇 |
2005年 | 140篇 |
2004年 | 112篇 |
2003年 | 104篇 |
2002年 | 105篇 |
2001年 | 60篇 |
2000年 | 77篇 |
1999年 | 67篇 |
1998年 | 65篇 |
1997年 | 59篇 |
1996年 | 75篇 |
1995年 | 82篇 |
1994年 | 62篇 |
1993年 | 70篇 |
1992年 | 97篇 |
1991年 | 96篇 |
1990年 | 79篇 |
1989年 | 76篇 |
1988年 | 64篇 |
1987年 | 68篇 |
1986年 | 70篇 |
1985年 | 89篇 |
1984年 | 97篇 |
1983年 | 86篇 |
1982年 | 82篇 |
1981年 | 113篇 |
1980年 | 62篇 |
1979年 | 80篇 |
1978年 | 79篇 |
1977年 | 94篇 |
1976年 | 67篇 |
1975年 | 84篇 |
1974年 | 88篇 |
1973年 | 66篇 |
1972年 | 56篇 |
1971年 | 50篇 |
1970年 | 38篇 |
1967年 | 36篇 |
排序方式: 共有4765条查询结果,搜索用时 750 毫秒
951.
952.
Conditional probabilities are one promising and widely used approach to model uncertainty in information systems. This paper discusses the DUCK-calculus, which is founded on the cautious approach to uncertain probabilistic inference. Based on a set of sound inference rules, derived probabilistic information is gained by local bounds propagation techniques. Precision being always a central point of criticism to such systems, we demonstrate that DUCK need not necessarily suffer from these problems. We can show that the popular Bayesian networks are subsumed by DUCK, implying that precise probabilities can be deduced by local propagation techniques, even in the multiply connected case. A comparative study with INFERNO and with inference techniques based on global operations-research techniques yields quite favorable results for our approach. Since conditional probabilities are also suited to model nonmonotonic situations by considering different contexts, we investigate the problems of maximal and relevant contexts, needed to draw default conclusions about individuals. 相似文献
953.
954.
Helmut Bnnemann 《Angewandte Chemie (International ed. in English)》1985,24(4):248-262
The cocyclization of alkynes with cyano compounds using organocobalt catalysts of the type [YCoL] has evolved into a versatile and technically useful method for synthesizing pyridine and its derivatives. An important advance came with the realization that the organo group Y remains attached to the cobalt throughout the catalytic cycle. This opened up the possibility of optimizing the catalyst by varying the controlling ligand Y. 相似文献
955.
956.
Based on structural data of lipid A from Chlamydia trachomatis strains, chemically pure tetra- and pentaacyl 1,4′-bisphosphoryl as well as the related 4′-monophosphoryl derivatives of lipid A were synthesized. (R)-3-Hydroxyicosanoic acid as a chiral constituent was prepared via Noyori-reduction of methyl-3-oxoicosanoic acid. Synthetic intermediates were O-acylated with myristoic acid residues at positions 3 and 3′ and N-acylated with (R)-3-hydroxyicosanoic acid at both glucosamine units. Efficient purification methods for highly hydrophobic long-chain tri-, tetra- and pentaacyl progenitors of lipid A have been developed. Purity and homogeneity of the synthetic target compounds were confirmed by NMR and MS-data as well as a sensitive immunostaining approach. The tetra- and pentaacyl species serve as biomedical probes to investigate the endotoxic potential of chlamydial lipid A and to clarify its role in Chlamydia associated infections. 相似文献
957.
958.
959.
960.