全文获取类型
收费全文 | 183422篇 |
免费 | 38430篇 |
国内免费 | 27076篇 |
专业分类
化学 | 121673篇 |
晶体学 | 2265篇 |
力学 | 12373篇 |
综合类 | 710篇 |
数学 | 22536篇 |
物理学 | 89371篇 |
出版年
2024年 | 518篇 |
2023年 | 2826篇 |
2022年 | 3011篇 |
2021年 | 4318篇 |
2020年 | 5329篇 |
2019年 | 5644篇 |
2018年 | 5013篇 |
2017年 | 5219篇 |
2016年 | 7368篇 |
2015年 | 7307篇 |
2014年 | 8370篇 |
2013年 | 11946篇 |
2012年 | 13932篇 |
2011年 | 15826篇 |
2010年 | 15707篇 |
2009年 | 15568篇 |
2008年 | 10192篇 |
2007年 | 9150篇 |
2006年 | 8286篇 |
2005年 | 7662篇 |
2004年 | 7100篇 |
2003年 | 5650篇 |
2002年 | 5230篇 |
2001年 | 5169篇 |
2000年 | 4138篇 |
1999年 | 4666篇 |
1998年 | 3949篇 |
1997年 | 3663篇 |
1996年 | 4074篇 |
1995年 | 4115篇 |
1994年 | 4109篇 |
1993年 | 3877篇 |
1992年 | 3411篇 |
1991年 | 2984篇 |
1990年 | 2497篇 |
1989年 | 2369篇 |
1988年 | 2256篇 |
1987年 | 1496篇 |
1986年 | 1550篇 |
1985年 | 1177篇 |
1984年 | 1236篇 |
1983年 | 513篇 |
1982年 | 1020篇 |
1981年 | 840篇 |
1980年 | 848篇 |
1979年 | 571篇 |
1978年 | 567篇 |
1977年 | 663篇 |
1976年 | 1085篇 |
1972年 | 553篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
E. Beinrohr M. Németh P. Tsch?pel G. T?lg 《Fresenius' Journal of Analytical Chemistry》1992,344(3):93-99
Summary Flow-through electrochemical cells with porous working electrodes made of crushed reticulated vitreous carbon and plated with mercury were used for absolute analysis of trace amounts of lead by anodic stripping coulometry with collection (ASCWC) in a flow system. The role of mercury coating, flow rate and pH were investigated. The coulombic content of the collection peak corresponded to the theoretical values calculated by Faraday's law in a concentration range from about 10–9 to 10–6 mol/l. The relative error and the relative standard deviation was +0.15% and 0.8%, respectively for 2×10–6 mol/l analyte concentration. The absolute detection limit (3 s) was 0.1 ng of Pb, the linear response range 7×104.
One leave from: Department of Analytical Chemistry, Slovak Technical University, CS-812 37 Bratislava, Czechoslovakia 相似文献
992.
In this paper the classical theorem of Zareckii about regular relations is generalized and an intrinsic characterization of regularity is obtained. Based on the generalized Zareckii theorem and the intrinsic characterization of regularity, the authors give a characterization of monotone normality of ordered spaces. A new proof of the Urysohn-Nachbin lemma is presented which is quite different from the classical one. 相似文献
993.
The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the upper critical magnetic field Hc3 at which superconductivity can nucleate is estimated. In addition, the authors locate the concentration of the order parameter, which depends on the inhomogeneous term a(x). Unlikely to the homogeneous case, the order parameter may concentrate in the interior of the superconducting material, due to the influence of the inhomogeneous term a(x). 相似文献
994.
The notion of a fuzzy retract was introduced by Rodabaugh (1981). The notion of a fuzzy pairwise retract was introduced in 2001. Some weak forms and some strong forms of α-continuous mappings were introduced in 1988 and 1997. The authors extend some of these forms to the L-fuzzy bitopological setting and construct various α-fuzzy pairwise retracts. The concept of weakly induced spaces in the case L = [0,1] was introduced by Martin (1980). Liu and Luo (1987) generalized this notion to the case that L is an arbitrary F-lattice and introduced the notion of induced L-fts. Several results are obtained, especially, for L-valued pairwise stratification spaces. 相似文献
995.
吴臻 《数学物理学报(B辑英文版)》2004,24(1):91-99
The existence and uniqueness results of fully coupled forward-backward stochastic differential equations with stopping time (unbounded) is obtained. One kind of comparison theorem for this kind of equations is also proved. 相似文献
996.
997.
Edison Munaf Toyohide Takeuchi Hiroki Haraguchi 《Fresenius' Journal of Analytical Chemistry》1992,342(1-2):154-156
Summary A continuous flow analysis is described for the determination of total mercury by cold vapor atomic absorption spectrometry. Organic mercury compounds such as methylmercury(II) chloride, ethylmercury(II) chloride and phenylmercury(II) chloride were decomposed by potassium peroxodisulphate with addition of ferric chloride as catalytic reagent. The reducing reagent used was tin(II) chloride in sodium hydroxide solution. With 1,000 mg Fe/l added in the decomposition process, we found that methylmercury(II) chloride and ethylmercury(II) chloride gave response signals similar to those of mercury(II) chloride. The proposed method was applied to the analysis of total mercury in waste water.
Permanent address: Department of Chemistry, Faculty of Mathematics and Natural Sciences, Andalas University, Padang, West Sumatra, Indonesia 相似文献
998.
In this paper, we study the homogenous quotient modules of the Hardy module on the bidisk. The essential normality of the
homogenous quotient modules is completely characterized. We also describe the essential spectrum for a general quotient module.
The paper also considers K-homology invariant defined in the case of the homogenous quotient modules on the bidisk.
This work is partially supported by the National Natural Science Foundation of China (Grant No. 10525106), the Young Teacher
Fund, the National Key Basic Research Project of China (Grant No. 2006CB805905) and the Specialized Research for the Doctoral
Program 相似文献
999.
1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. 相似文献
1000.
PURE STATE APPROACH TO C(x)_αZ_nLIBINGREN;LINQING(InstituteofMathematics,AcademiaSinica,Beijing100080,China.Projectsupportedbyth?.. 相似文献