全文获取类型
收费全文 | 17729篇 |
免费 | 1361篇 |
国内免费 | 3590篇 |
专业分类
化学 | 18510篇 |
晶体学 | 561篇 |
力学 | 121篇 |
综合类 | 70篇 |
数学 | 157篇 |
物理学 | 3261篇 |
出版年
2024年 | 35篇 |
2023年 | 225篇 |
2022年 | 492篇 |
2021年 | 519篇 |
2020年 | 788篇 |
2019年 | 612篇 |
2018年 | 555篇 |
2017年 | 759篇 |
2016年 | 815篇 |
2015年 | 670篇 |
2014年 | 857篇 |
2013年 | 1339篇 |
2012年 | 1999篇 |
2011年 | 1194篇 |
2010年 | 851篇 |
2009年 | 1057篇 |
2008年 | 1095篇 |
2007年 | 1237篇 |
2006年 | 1014篇 |
2005年 | 923篇 |
2004年 | 759篇 |
2003年 | 707篇 |
2002年 | 557篇 |
2001年 | 414篇 |
2000年 | 412篇 |
1999年 | 396篇 |
1998年 | 335篇 |
1997年 | 305篇 |
1996年 | 275篇 |
1995年 | 251篇 |
1994年 | 217篇 |
1993年 | 195篇 |
1992年 | 179篇 |
1991年 | 126篇 |
1990年 | 95篇 |
1989年 | 67篇 |
1988年 | 55篇 |
1987年 | 44篇 |
1986年 | 41篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 21篇 |
1976年 | 16篇 |
1973年 | 14篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
《Analytical letters》2012,45(14):1743-1748
Abstract The chromatographic behaviour of 32 metal ions has been studied on paper Impregnated with Zirconium(IV) antimonate in aqueous HCI and mixed solvent system containing dimethyisul phoxide and dioxane. Several Important binary and ternary separations have been achieved. Quantitative separation of Hg(ll) from Ni2+, Pb2+, Pd2+, Ru3+, Rh3+, Bi3+, Co2+, Cd2+ and Gd3+ is described. 相似文献
82.
《Journal of Coordination Chemistry》2012,65(10):1545-1552
Lead(II) 4,4,4-trifluoro-1-naphthyl-1,3-butanedione (Htfnb) complexes of 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy), [Pb2(bpy)2(tfnb)2] (1) and [Pb2(phen)2(tfnb)2] (2), have been synthesized and characterized by elemental analysis, IR, spectroscopy and X-ray crystallography. The self-assembly of 1 and 2 is likely to be caused by C–H ··· F–C, C–H ··· O and π–π stacking interactions. 相似文献
83.
《Journal of Coordination Chemistry》2012,65(21):3764-3771
The crystal structure of [Zn2(2-pmOpe)2Cl4] (2-pmOpe?=?diethyl (pyridin-2-ylmethyl)phosphate) was determined by X-ray-diffraction method. The compound was also characterized by IR, far-IR, 1H, and 31P NMR spectroscopy. In this compound, 2-pmOpe is a bidentate N,O-bridging ligand and Zn(II) are slightly distorted tetrahedral ZnNOCl2. Zn(II) ions are doubly bridged by the 2-pmOpe ligands, resulting in a dinuclear species. The structure is stabilized by intermolecular C–H?···?O and C–H?···?Cl hydrogen bonds. The spectral properties are in agreement with the structural data. 相似文献
84.
《Journal of Coordination Chemistry》2012,65(22):2449-2460
The synthesis and characterization of [Cu(4-MeOsal)2(2-pyme)2] (1) and [Cu(3-Mesal)2(2-pyme)2] (2) (where 4-MeOsal?=?4-methoxysalicylate, 3-Mesal?=?3-methylsalicylate and 2-pyme?=?2-pyridylmethanol) are reported. The composition and stereochemistry as well as the mode of coordination have been determined by elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 1.8–300?K. The crystal structures of Cu(4-MeOsal)2(2-pyme)2 and Cu(3-Mesal)2(2-pyme)2 have been determined. 相似文献
85.
Synthesis and crystal structure of bis(m-hydroxybenzoato(1-))bis(benzimidazole) copper(II) dihydrate
《Journal of Coordination Chemistry》2012,65(7):629-636
The crystal structure of the title complex was determined by single-crystal X-ray diffraction methods. The unit cell contains two independent molecules, A and B. B is a mononuclear Cu(II) complex with square-planar coordination geometry formed by two benzimidazole molecules and two hydroxylbenzoate anions. A is a dimer of B, formed by bridging hydroxybenzoate, and copper assumes square-pyramidal geometry. Aromatic π–π stacking is observed between parallel benzimidazole rings of neighboring A molecules. IR spectra of the compound are assigned in line with the crystal structure. 相似文献
86.
《Journal of Coordination Chemistry》2012,65(2):165-173
The title complex has been synthesized and characterized by elemental and thermal analysis, IR and electronic spectroscopy, conductivity studies and X-ray crystallography. In the crystal, the complex has two-fold symmetry and the copper atom adopts square pyramidal coordination. Bond valences for Cu were computed. Cu–O(propionate) bonds are slightly stronger than the Cu–N bonds, and the Cu–O(water) bond is distinctly weaker. Molecules are linked by O–H···O hydrogen bonds to form infinite hydrogen-bonded chains along the y axis. 相似文献
87.
《Journal of Coordination Chemistry》2012,65(13):1537-1539
The results of a spectrophotometric investigation of the reaction of the biologically active salt 1-benzoylethylpyridinium-4-aldoxime chloride with aquapentacyanoferrate(II) ion are presented. In spite of the presence of two donor sites, only the carbonyl group of the ligand coordinates to the iron centre. Reaction kinetics are consistent with a dissociative mechanism. 相似文献
88.
《Journal of Coordination Chemistry》2012,65(5):832-841
The liquid–liquid extraction of copper(II) with Schiff bases in chloroform from sulfate media is studied for pH and concentration of the extractant. Stoichiometry coefficients of the extracted species are determined by the slope analysis method. With salicylideneaniline, the copper(II) is extracted as a mixed chelate complex, CuL2HL. In the presence of substituent, the copper is extracted as simple chelates, CuL2. The trends in the values of extraction constants were explained in terms of the nature of the substituents. 相似文献
89.
《Journal of Coordination Chemistry》2012,65(1-3):17-23
The DNA cleavage properties of two cationic manganese porphyrins possessing different peripheral substituents were compared. The identical nature of the strand scission patterns of the porphyrins on a 139 base pair restriction fragment of pBR-322 DNA, along with other evidence, suggests that the porphyrin is end-on bound via the minor groove in a melted or partially melted region of DNA. This unusual binding mode underscores the potential of outisde binding cationic metalloporphyrins as probes for low melting regions of DNA 相似文献
90.
介绍了一种简便易行的降低疏松固体物质冲击波温度的方法,其要点是用液体石蜡充填样品的空隙。以用粉末锐钛矿压装成型的样品为例,对比了不充填和充填液态石蜡时冲击波作用的结果。在同样的冲击加载条件下(均为钢飞片,撞击速度为3.16 km/s),估算两种样品中达到的压力分别为36.3 GPa和46.8 GPa,平均温度分别约为4.7×103 ℃和2.0×103 ℃,即:充填液态石蜡的样品中压力增加了约10 GPa,但平均温度降低了近3×103 ℃。对冲击后回收样品的分析结果表明,不充填石蜡样品的主要产物为金红石,即冲击波产生的高温起了主要作用。而充填液态石蜡时,主要生成β-TiO2高压相,即高压起了主要作用。 相似文献