全文获取类型
收费全文 | 8974篇 |
免费 | 1359篇 |
国内免费 | 1782篇 |
专业分类
化学 | 10706篇 |
晶体学 | 27篇 |
力学 | 233篇 |
综合类 | 52篇 |
数学 | 231篇 |
物理学 | 866篇 |
出版年
2024年 | 25篇 |
2023年 | 109篇 |
2022年 | 256篇 |
2021年 | 311篇 |
2020年 | 469篇 |
2019年 | 261篇 |
2018年 | 294篇 |
2017年 | 263篇 |
2016年 | 447篇 |
2015年 | 504篇 |
2014年 | 507篇 |
2013年 | 707篇 |
2012年 | 699篇 |
2011年 | 564篇 |
2010年 | 562篇 |
2009年 | 646篇 |
2008年 | 831篇 |
2007年 | 602篇 |
2006年 | 613篇 |
2005年 | 553篇 |
2004年 | 485篇 |
2003年 | 509篇 |
2002年 | 225篇 |
2001年 | 214篇 |
2000年 | 216篇 |
1999年 | 158篇 |
1998年 | 143篇 |
1997年 | 173篇 |
1996年 | 171篇 |
1995年 | 143篇 |
1994年 | 101篇 |
1993年 | 100篇 |
1992年 | 74篇 |
1991年 | 41篇 |
1990年 | 34篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Paolo Zatta Tamas KissMario Suwalsky Guy Berthon 《Coordination chemistry reviews》2002,228(2):271-284
Aluminium has been known as a neurotoxic agent to experimental animals since the last century (Arch. Exp. Pharmacol. 40 (1897) 98). However, great interest arose in it bioinorganic chemistry as well biology when it was demonstrated to be the causative agent in pathologies related to the long-term dialysis treatment of uremic subjects with renal failure (Life Chem. 11 (1994) 197), and as a potential etiopathogenic cofactor for several neurodegenerative diseases. The inorganic biochemistry of aluminium is still largely to be discovered. In this review the pro-oxidative property of aluminium toward biological membrane will be presented and its implications in involvement in human pathology will be discussed in an interdisciplinary frame from the bioinorganic point of view. 相似文献
52.
I. E. Karpeiskaya L. F. Godunova E. S. Levitina M. R. Lyubeznova E. I. Klabunovskii E. S. Shpiro G. N. Baeva E. D. Lubuzh L. B. Krentsel' A. D. Litmanovich N. A. Plate 《Russian Chemical Bulletin》1992,41(10):1858-1867
Pd complexes have been obtained from linear and cross-linked copolymers ofR,S-, R-, andS-1-(4-vinylphenyl)ethylamine (1) with styrene and divinylbenzene. Reduction of these compounds gave catalysts which were active in the reductive solvolysis of -acetaminocinnamic acid azlactone (2) and hydrogenation of the solvolysis products -acetamidocinnamic acid (ACA), its esters, and its 1-phenylethylamide. The catalysts showed no enantioselective properties in the reductive hydrolysis, but were more active than the catalyst obtained in the absence of the polymer (the monomeric analog). The use of polymeric catalysts has shown that, in reductive aminolysis, the chiral nucleophile plays the dominant part in determining the stereoselectivity of the reaction, rather than the chiral ligand of the catalytic complex. The polymer matrix stabilizes the low-valent state of the palladium in the complex. In the hydrogenation of ACA and its esters, the catalyst on the cross-linked polymer is much more active than its monomeric analog, but showed no enantioselectivity. Hydrogenation of acetamidocinnamic acidR-andS-1-phenylethylamides on a chiral Pd-polymer catalyst occurred with double asymmetric induction.Deceased.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 117912 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2368–2380, October, 1992. 相似文献
53.
54.
The thickness and the porosity of a deposit during ultrafiltration experiments are determined using an electrochemical method. Twenty microelectrodes are mounted flush to a ceramic plane membrane and maps of deposit thickness are determined for three inlet/outlet distributors configurations. Combining an electrochemical method and a step transient method, the determination of the thickness and the porosity of a particles deposit is performed. These local thickness and porosity values are analyzed thanks to wall shear stress local measurements obtained in a previous work [Sep. Sci. Technol. 37 (10) (2002) 2251]. The results emphasize the heterogeneity of the deposit thickness, especially in zones of low wall shear stress. Furthermore, the porosity values of the deposit are ranged between 0.3 and 0.8 as a function of the location at the membrane surface. 相似文献
55.
56.
从(-)-(1S,2R,4S)-5,6-二亚甲基双环[2.2.1]庚-2-醇(I)和(-)-(1S,2S,4S)-5,6-二亚甲基双环[2.2.1]庚-2-醇(Ⅱ)出发,合成了它们的醚类和取代苯甲酸酯类光学纯的衍生物。通过[α]D测定和构型分析,发现它们是含有3个手性碳(C1,C2和C4)的桥环化合物,其旋光性与构型的关系均符合可极化度多级圆球不对称性模型。 相似文献
57.
58.
59.
Composite membranes were prepared by (a) infiltrating NAFION with SiO2-P2O5-ZrO2 sol, and (b) recasting a film using NAFION solution containing SiO2-P2O5-ZrO2 sol. The membranes were characterized by Differential Thermal Analysis and ac-impedance spectroscopy as a function of relative humidity. The influences of the heat treatment (80°C–150°C) and cleaning on the electrical properties were investigated. The incorporation of SiO2-P2O5-ZrO2 gels into NAFION lead to improvements in its thermal stability and proton conductivity. 相似文献
60.
KEIKO TAKAHASHI HIDEKI YOKOMIZO KATSURO ISHIYAMA MASAHIKO KITSUTA MEGUMI OHASHI 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):95-99
Asymmetric reduction of indol-3-pyruvic acid (IPA) with NaBH4 in aqueous solution in the presence of various cyclodextrins (α-, β-, γ-, mono-6-amino-6-deoxy-β- and di-6ABamino-6AB-deoxy-β-cyclodextrin) was investigated. From the NMR and circular dichroism spectral studies, the conformation of the CyD–substrate complexes is suggested; the part of carboxylic group stay in the cavity of α-CyD, whole of IPA in β-CyD, two molecules in a γ-CyD cavity, and IPA(s) is/are on the rim of the cavity of mono-6-amino-6-deoxy-β- and di-6ABamino-6AB-deoxy-β-CyD (AβCyD, DAβCyD) with electrostatic interaction between amino group and carboxylic group. This conformational difference provides in the difference in the optical selectivity of reduction. 相似文献