全文获取类型
收费全文 | 61508篇 |
免费 | 6169篇 |
国内免费 | 7838篇 |
专业分类
化学 | 51306篇 |
晶体学 | 984篇 |
力学 | 2346篇 |
综合类 | 439篇 |
数学 | 5204篇 |
物理学 | 15236篇 |
出版年
2024年 | 78篇 |
2023年 | 568篇 |
2022年 | 1297篇 |
2021年 | 1472篇 |
2020年 | 1716篇 |
2019年 | 2598篇 |
2018年 | 1689篇 |
2017年 | 2756篇 |
2016年 | 2327篇 |
2015年 | 2123篇 |
2014年 | 2816篇 |
2013年 | 4873篇 |
2012年 | 3642篇 |
2011年 | 4028篇 |
2010年 | 3125篇 |
2009年 | 3766篇 |
2008年 | 3800篇 |
2007年 | 3871篇 |
2006年 | 3531篇 |
2005年 | 3220篇 |
2004年 | 3164篇 |
2003年 | 2567篇 |
2002年 | 2672篇 |
2001年 | 1867篇 |
2000年 | 1670篇 |
1999年 | 1309篇 |
1998年 | 1204篇 |
1997年 | 1030篇 |
1996年 | 984篇 |
1995年 | 942篇 |
1994年 | 766篇 |
1993年 | 603篇 |
1992年 | 590篇 |
1991年 | 406篇 |
1990年 | 281篇 |
1989年 | 261篇 |
1988年 | 249篇 |
1987年 | 182篇 |
1986年 | 149篇 |
1985年 | 145篇 |
1984年 | 133篇 |
1983年 | 52篇 |
1982年 | 121篇 |
1981年 | 150篇 |
1980年 | 140篇 |
1979年 | 161篇 |
1978年 | 111篇 |
1977年 | 89篇 |
1976年 | 78篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. F. Mironov L. M. Burnaeva G. A. Khlopushina I. V. Konovalova M. A. Kurykin A. I. Rakhmatullin 《Russian Chemical Bulletin》1996,45(12):2858-2860
Benzo-1,3,2,dioxaphosphorin-4-ones react with hexafluoroacetone imine to form 2-R-2,5-dioxo-3,3-bis(trifluoromethyl)-6,7-benzo,1,4,2-oxozaphosphepanes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp. 3008–3010, December, 1996. 相似文献
992.
From phasebarograms it is possible to construct phase diagrams. We show on example of the system Bi/Se/O how follow ternary sections from the total pressure measurements in equilibrium and how we can attribute the barogram of the ternary region Bi2Se3/Bi2O2Se/Se to the binary system Bi2Se3/Se. The knowledge of the ternary system Bi/Se/I and its coexistent pressure courses allow to followT-p-x conditions for the chemical transport of phases from this system. 相似文献
993.
Yu. N. Ogibin A. I. Ilovaisky V. M. Merkulova G. I. Nikishin 《Russian Chemical Bulletin》1995,44(3):507-510
The effect of anions of the supporting electrolyte (F–, dialkylphosphate, TsO–, and BF
4
–
and other electrolysis conditions (anode material, temperature, substrate concentration) on the selectivity of the direct anodic oxidation ofp-methoxytoluene in methanol into 4-methoxybenzaldehyde dimethylacetal was studied. The highest selectivity was obtained in the presence of fluoride anion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 524–527, March, 1995.This work was financially supported by the Ministry of Science, High School and Technical Policy of the Russian Federation within the scope of the State scientific-technical program Ecologically harmless processes of chemistry and chemical technology (project No. 1.140 Low-tonnage chemical products) and by the International Science Foundation (Grant Ch-2-1246-0923). 相似文献
994.
995.
The title compounds were prepared by reaction of CaSb2, SrSb2, or BaSb3 with the transition metals and antimony in sealed silica tubes. They crystallize with the cubic LaFe4P12-structure, which was refined from single-crystal X-ray data of CaFe4Sb12, SrRu4Sb12, and BaRu4Sb12 to residuals of R = 0.014, 0.016, and 0.014, respectively. The thermal parameters of the alkaline earth ions increase with decreasing ionic size. The Sb? Sb distances are greater in the iron compound than they are in the two ruthenium compounds. This is rationalized to be due to a larger portion of electrons in antibonding Sb? Sb states in the iron compound. 相似文献
996.
核/壳结构增韧剂对环氧树脂的抗冲改性 总被引:7,自引:0,他引:7
核/壳结构增韧剂对环氧树脂的抗冲改性张明耀,张会轩,杨海东,冯之榴(吉林工学院化学工程系长春130012)(中国科学院长春应用化学研究所长春)关键词核/壳结构,增韧剂,环氧树脂,共混核/壳结构增韧剂是用分步乳液聚合技术制造的一种复合乳胶粒子,其核为橡... 相似文献
997.
5,7,8位取代的喹诺酮类化合物定量构效关系的量子化学研究 总被引:2,自引:0,他引:2
5,7,8位取代的喹诺酮类化合物定量构效关系的量子化学研究俞庆森,朱龙观,林瑞森,蔡国强(浙江大学化学系杭州310027)关键词:氟喹喏酮类,定量构效关系,CNDO/2氟喹诺酮类是一类重要的抗感染化疗药物 ̄[1],近十年对其研究进展神速 ̄[2],结构... 相似文献
998.
用INDO/CI方法研究了含有Fe-Fe键的原子簇体系[Fe2S2X4]^2-(X=Cl,Br,I)的电子光谱及电子结构,对于这些多谱带体系,谱带波数计算值与实验值符合,在谱带的指认分析中,发现了πd^1→πd等新的跃迁方式,对跃迁方式作了解释和分类,并讨论了谱带的电荷转移性质,此外,还对体系的化学键等性质进行了分析。 相似文献
999.
Pentacoordinate complex cations of the general formula [(C6F5)2SbL3]3+ stabilized as solid salts in combination with tetraphenylborate (BPh4), tetrafluorobroate (BF4) anions, where L=DMSO, Ph3AsO, PyO, DMF, α-, β- and γ-picoline have been isolated. The newly formed complexes were characterized by elemental analysis, molar conductance measurements, solid-state IR and and NMR. From these results, a five-fold coordination around antimony was required. 相似文献
1000.
Study on the Phase Diagram of CsCl-CeCl3-HCl(11%)-H2O System and the Properties of the Compounds 总被引:2,自引:0,他引:2
The equilibrium solubility of CsCl-CeCl3-HCl(11%)-H2O qua-ternary system at 25℃ has been determined by the physicchemical analysis method ,and the phase diagram was plotted, Two new double salts 3CsCl.CeCl3.3H2O and CsCl.CeCl3.4H2O obtained from the complicated system were identified and characterized by XRD,TG-DTA ,DSC,UV and fluorescence spectroscopy, Studies on the fluorescence excitation and emission show that 3CsCl.CeCl3.3H2O and CsCl.CeCl3.4H2O have upconversion luminescence of infrared-visible range,and the upconversion emission intensity increases with the increase of ratio of CeCl3 in CsCl. 相似文献