全文获取类型
收费全文 | 11962篇 |
免费 | 1520篇 |
国内免费 | 2830篇 |
专业分类
化学 | 12790篇 |
晶体学 | 187篇 |
力学 | 354篇 |
综合类 | 145篇 |
数学 | 61篇 |
物理学 | 2775篇 |
出版年
2024年 | 55篇 |
2023年 | 180篇 |
2022年 | 407篇 |
2021年 | 547篇 |
2020年 | 755篇 |
2019年 | 575篇 |
2018年 | 397篇 |
2017年 | 428篇 |
2016年 | 484篇 |
2015年 | 510篇 |
2014年 | 561篇 |
2013年 | 955篇 |
2012年 | 806篇 |
2011年 | 649篇 |
2010年 | 507篇 |
2009年 | 606篇 |
2008年 | 623篇 |
2007年 | 658篇 |
2006年 | 691篇 |
2005年 | 608篇 |
2004年 | 629篇 |
2003年 | 530篇 |
2002年 | 593篇 |
2001年 | 396篇 |
2000年 | 363篇 |
1999年 | 293篇 |
1998年 | 285篇 |
1997年 | 275篇 |
1996年 | 265篇 |
1995年 | 287篇 |
1994年 | 228篇 |
1993年 | 221篇 |
1992年 | 211篇 |
1991年 | 149篇 |
1990年 | 133篇 |
1989年 | 90篇 |
1988年 | 84篇 |
1987年 | 60篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 542 毫秒
101.
O. N. Babkina O. M. Chukanova E. E. Faingol"d N. M. Bravaya 《Russian Chemical Bulletin》2004,53(4):785-790
Quantitative characteristics of changes in the energy of charge transfer from -bonded ligands to metal are presented for the series of structurally similar ansa-metallocene complexes of IVB Group elements. The changes are caused by the solvation effect, replacement of -bonded chlorine ligands by methyl groups and of bridging ethylene groups by dimethylsilylene moieties, introduction of the methyl substituent into position 2 and phenyl substituent into position 4 of the indenyl system, variation of the transition metal in metallocene, and formation of complexes with polymethylalumoxane (MAO) at different AlMAO/Zr ratios. These effects are found to be additive. 相似文献
102.
Urea can be sorbed by coordination (or complexation)with transitional metalpolyacrylic acid complex and transitional metal-polyacrylamide containing polyethylenepolyamine ligand complexes. The experimental results indicate that the sorbents can sorb about 60mg urea per gram of sorbent at 37℃ and the concentration of urea was 1300.0rag/1 in NaH_2PO_4 and Na_2HPO_4 buffer solution (pH=7.0) and the urea sorption capacity was affected by many factors such as other competive ligands, sorption time, pH and the concentration of urea. 相似文献
103.
104.
105.
河口水体中痕量稀土元素的共沉淀预富集-电感耦合等离子体质谱法测定研究 总被引:3,自引:0,他引:3
建立了氢氧化铟共沉淀预富集 -电感耦合等离子体质谱法测定河口水体中痕量稀土元素的方法。实验结果表明 ,在80mg·L -1的In3 +和pH9.5的实验条件下 ,在1.0L水样中添加5.0~200.0ng的混合稀土标准溶液 ,均能定量回收 ,回收率在82.2 %~106.9 %之间。方法的分析流程空白为0.04(Tb)~10.17(La)ng·L -1,检出限在0.17(Yb)~1.46(La)ng·L-1之间 ,精密度 (RSD ,n=3)小于11.7 % ,可满足河口淡水和海水样品中的痕量稀土元素定量分析的要求 相似文献
106.
107.
本文报道了一种新的配体:10-乙基-3-甲酰吩噻嗪缩肼基二硫代甲酸甲酯(HL)及其金属配合物的合成。采用了元素分析、质谱、核磁共振、红外光谱对配体及其金属配合物进行了表征。此外,并应用紫外、荧光和Z-扫描技术,测定了配体及其金属配合物的荧光最佳发射波长(λmaxem)、荧光量子产率(Φf)、寿命(τ)和非线性光学性质。结果表明它们在DMF溶液中都能发射出较强的橄榄色荧光,配体及其金属配合物都有双光子吸收,并且金属配合物的非线性光学效应比配体明显增强。用半经验量子化学方法(RHF/PM3)计算结果与实验值较为吻合。 相似文献
108.
电化学超级电容器电极材料的研究进展 总被引:9,自引:0,他引:9
回顾了电化学超级电容器电极材料的研究进展,并对不同电极材料的储能原理和性能特点进行了简要的阐述。参考文献29篇。 相似文献
109.
H. M. Parekh P. K. Panchal M. N. Patel 《Journal of Thermal Analysis and Calorimetry》2006,86(3):803-807
Some new coordination polymers of Mn(II),
Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), obtained from the interaction of
metal acetate with dipotassium salt of N,N’-di(carboxyethylidene)terephthalaldehydediimine
(K2SB) are described. The products, which have been
characterized by elemental analyses, magnetic measurements, thermogravimetric
analyses, electronic and infrared spectral studies, have composition, [M(SB)(H2O)2]n. These colored coordination polymers are non-hygroscopic and quite stable
at room temperature. On the basis of analytical data and IR studies, a 1:1
metal to ligand stoichiometry has been suggested to these coordination polymers.
The IR studies have also revealed that ligands are coordinated to metal ion
through carboxy oxygen and azomethine nitrogen. All the studies suggested
tetradentate nature of the ligand with octahedral symmetry of the coordination
polymers. All the coordination polymers are insoluble in acetone, ethanol,
chloroform, methanol, benzene, DMF and DMSO. The thermal decomposition of
the coordination polymers is studied and indicates that not only the coordinated
water is lost but also that the decomposition of the ligand from the coordination
polymers is necessary to interpret the successive mass loss. 相似文献
110.
Conventional criteria and indices of aromaticity, including electronic, geometric, energetic and magnetic aspects have been applied to examine the aromaticity of five typical transition metal heterocyclic complexes, i.e. six-membered osmabezene 1 and iridabenzene 2, five-membered cobaltacyclopentadiene 3 and iridacyclopentadiene 4, and four-membered tungstacyclobutadiene 5. The results show that the cyclic, planar, conjugated and Hückel 4n+2 rule’s criteria in the transition-metal-containing heterocycles of the five complexes studied are all met. Five quantitative aromaticity indices, including Bird aromatic index (In), homodesmotic reaction aromatic stabilization energy (HASE), absolute hardness (η), diamagnetic susceptibility exaltation (Λ) and NMR chemical shift (δH), qualitatively lead to a consistent and affirmative conclusion that all of them are aromatic. However, they fail to draw a common conclusion for their relative magnitudes of aromaticity, which proves once again the multidimensional character of aromaticity. 相似文献