全文获取类型
收费全文 | 7961篇 |
免费 | 154篇 |
国内免费 | 612篇 |
专业分类
化学 | 7715篇 |
晶体学 | 328篇 |
力学 | 30篇 |
综合类 | 16篇 |
数学 | 142篇 |
物理学 | 496篇 |
出版年
2024年 | 7篇 |
2023年 | 61篇 |
2022年 | 130篇 |
2021年 | 114篇 |
2020年 | 186篇 |
2019年 | 217篇 |
2018年 | 204篇 |
2017年 | 275篇 |
2016年 | 243篇 |
2015年 | 150篇 |
2014年 | 224篇 |
2013年 | 414篇 |
2012年 | 1371篇 |
2011年 | 388篇 |
2010年 | 309篇 |
2009年 | 415篇 |
2008年 | 491篇 |
2007年 | 544篇 |
2006年 | 413篇 |
2005年 | 403篇 |
2004年 | 298篇 |
2003年 | 251篇 |
2002年 | 196篇 |
2001年 | 162篇 |
2000年 | 153篇 |
1999年 | 166篇 |
1998年 | 126篇 |
1997年 | 93篇 |
1996年 | 98篇 |
1995年 | 97篇 |
1994年 | 75篇 |
1993年 | 63篇 |
1992年 | 68篇 |
1991年 | 54篇 |
1990年 | 41篇 |
1989年 | 26篇 |
1988年 | 11篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有8727条查询结果,搜索用时 15 毫秒
891.
《Journal of Coordination Chemistry》2012,65(18):1689-1694
A mercury(II) chloride adduct of ferron (7-iodo-8-hydroxyquinoline-5-sulfonic acid), [HgCl2 (C9H6INO4)·H2O] has been synthesized and characterized by X-ray diffraction analysis and spectroscopic studies. The compound crystallizes in P21/c space group, a?=?8.919(3), b?=?23.216(3), c?=?7.714(3)?Å, β?=?95.79(3)°. The coordination geometry around mercury is distorted square planar [(2+2) coordination] with two short Hg–Cl bonds [2.308(2) and 2.309(18)?Å] and two long Hg–O(sulfonate) [2.738(4)?Å] and Hg–O(water) [2.889(4)?Å] bonds. The sulfonic group is deprotonated, the proton having migrated to the quinoline N atom that forms intermolecular hydrogen bonds. The inversion related organic ligands are stacked over one another. The crystal structure is further stabilized by a C–H···O, O–H···O and N–H···O hydrogen bonds. 相似文献
892.
《Journal of Coordination Chemistry》2012,65(3):325-331
A novel one-dimensional complex, [Cd(NIT4py)2(DTB)2(H2O)2] (1), (where NIT4py is 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and DTB is 3,5-dinitrobenzoate) has been synthesized and characterized by elemental analyses, IR and electronic spectra, single-crystal X-ray diffraction and magnetic measurements. The Cd(II) ion lies in a distorted octahedral environment with two nitrogen atoms from two NIT4py ligands and two oxygen atoms from two DTB molecules in the basal plane, and two oxygen atoms from two water molecules in axial positions. [Cd(NIT4py)2(DTB)2(H2O)2] units are connected to form one-dimensional chains by intermolecular hydrogen bonds. The complex exhibits intramolecular antiferromagnetic interactions. 相似文献
893.
《Journal of Coordination Chemistry》2012,65(5):493-498
Two new binuclear copper(II) complexes, Cu(tacn)Cu(oxpn)(ClO4)2·C2H5OH (1), and Cu(tacn)Cu(oxap)(ClO4)2·CH3OH (2), have been prepared from the planar fragment Cu(oxpn) and Cu(oxap) (tacn denotes 1,4,7-triazacyclononane, oxpn and oxap stand for the dianions of N,N′-bis(3-aminopropyl)oxamide, and N,N′-bis(2-aminopropyl)oxamide, respectively). The complexes have been characterized by means of elemental analyses and IR, and UV spectra. The crystal structure of compound 1 shows that copper(II) coordinates to the four nitrogen atoms of oxpn in a square-planar environment and the other copper(II) ion is in a distorted square-pyramidal environment. 相似文献
894.
《Journal of Coordination Chemistry》2012,65(7):759-775
The interaction of tin(II) and tin(IV) chlorides with norfloxacin (NOR) has been investigated. Elemental analysis, infrared, mass spectra and thermal analysis have been used to characterize the isolated solid complexes. The results support the formation of complexes with the formula [Sn(NOR)2]Cl2·4H2O and [Sn(NOR)3]Cl4. The infrared spectra of the isolated solid complexes suggested that NOR act as bidentate ligand through the carbonyl oxygen atom and one oxygen atom of the carboxylic group forming six-membered rings with the tin ions. The interpretation, mathematical analysis and evaluation of kinetic parameters of thermogravimetric (TGA) and its differential (DTG), such as entropy of activation, pre-exponential factors, activation energy evaluated by using Coats–Redfern and Horowitz–Metzger equations are carried out for two complexes. The data obtained indicate that the two complexes decompose in one stage and general mechanisms describing the decomposition are suggested. Furthermore, the electronic, and 1H?NMR spectra have been studied. 相似文献
895.
《Journal of Coordination Chemistry》2012,65(9):1015-1024
Mercury(II) and lead(II) complexes with 2,2′-bis(4,5-dimethylimidazole) (DmImH), [Hg(DmImH)(SCN)2] and [Pb(DmImH)(NCS)2], have been synthesized and characterized by IR specta and elemental analyses. The molecular structure of [Pb(DmImH)(NCS)2] n is polymeric with four-coordinate lead atoms. The [Hg(DmImH)(SCN)2] complex is built up of monomeric Hg(SCN)2 units with one “DmImH” ligand coordinated to the Hg atom via the two N atoms in a distorted tetrahedral environment. The thiocyanate ligands are coordinated to lead via nitrogen, but to mercury via the sulfur. There are π–π stacking interactions between the parallel aromatic rings in the mercury(II) complex. 相似文献
896.
《Journal of Coordination Chemistry》2012,65(10):1089-1099
Aquabis(N,N-dimethylglycinato)copper(II) dihydrate, [Cu(dmg)2(H2O)]·2H2O, has been synthesized and characterized by elemental analysis, FT-IR, magnetic data, thermal analysis, solution UV-visible spectroscopy, X-ray crystal structure analysis and electrospray ionization mass spectroscopy. The square pyramidal copper(II) complex crystallizes in the orthorhombic space group P212121. The complex cleaves circular plasmid DNA (pBR322) in the presence of H2O2. The extent of cleavage varies with the concentration range of the complex, the type of buffer used, pH of buffer and the concentration of H2O2. Hydroxyl radical scavenger can inhibit the nucleolytic ability of this complex. 相似文献
897.
《Journal of Coordination Chemistry》2012,65(3):339-346
New water-soluble zinc(II) Schiff-base complexes derived from amino acids (glycine, L-phenylalanine, and L-valine) and salicylaldehyde-5-sulfonates (sodium salicylaldehyde-5-sulfonate and sodium 3-methoxy-salicylaldehyde-5-sulfonate) have been synthesized. The complexes were characterized by elemental analysis, IR, electronic, 1H?NMR, and 13C?NMR spectra. In the IR spectra of the complexes, the large difference between the asymmetric νas(COO) and symmetric νs(COO) carboxylate stretch, Δν(νas(COO)–νs(COO)) of 199–247?cm?1, indicates monodentate coordination of the carboxylate group. Spectral data showed that in these complexes the ligand is a tridentate ONO moiety, coordinating to the metal through its phenolic oxygen, imine nitrogen, and carboxyl oxygen. 相似文献
898.
《Journal of Coordination Chemistry》2012,65(7):763-769
A novel dinuclear nickel(II) complex Ni2(NO3)4(APTY)4 (1) (APTY?=?1,5-dimethyl-2-phenyl-4-{[(1E)-pyridine-4-ylmethylene]amino}-1,2-dihydro-3H-pyrazol-3-one), was synthesized by solvothermal reaction of Ni(NO3)2?·?6H2O with APTY in methanol at 353?K. The structure consists of centrosymmetric dimers resulting from octahedrally coordinated Ni atoms bridged by APTY ligands. Weak intermolecular interactions (C–H?···?N, C–H?···?O hydrogen bonding, C–H?···?π and π–π stacking interactions) are responsible for a supramolecular assembly of molecules in the lattice. Magnetic measurements over 1.8–300?K show weak antiferromagnetic coupling between Ni(II) ions with J?=?2.969?cm?1, g?=?2.280, θ?=??5.903. 相似文献
899.
《Journal of Coordination Chemistry》2012,65(8):877-889
Two new complexes of imidazole alcohols, 4-hydroxymethylimidazole (4-CH2OHim) and 4-hydroxymethyl-5-methylimidazole (4-CH2OH-5-CH3im), with cobalt(II) of formula [CoL2(H2O)2](NO3)2 were obtained. These compounds were described through single X-ray diffraction studies, spectroscopic (Ir. Far-IR, UV-Vis-NIR) and magnetic measurements. In the present complexes imidazole ligands are bidentate coordinating the heterocyclic ring through pyridine-like nitrogen and the oxygen atom of the hydroxymethyl group (chromophore CoN2O4). The shape of Co(II) coordination polyhedra is that of a distorted octahedron, with the equatorial plane defined by the 4-CH2OHim (or 4-CH2OH-5-CH3im) bidentate ligands and two water molecules occupying axial positions (i.e. trans to each other). Formation of successive cobalt(II) complexes with 4-CH2OH-5-CH3im in aqueous solution was followed quantitatively by potentiometry. 相似文献
900.
《Journal of Coordination Chemistry》2012,65(11):1165-1171
Reactions of 3,6-bis(2′-pyridyl)pyridazine derivatives (n-dppn)¶ with MX2(PhCN)2 (M?=?Pd, Pt; X?=?Cl,?Br) have been investigated. The new complexes cis-[PdCl2(n-dppn)] (n?=?5,?6,?8,?12), cis-[PtCl2(n-dppn)]?·?H2O (n?=?5,?6), cis-[PtCl2(8-dppn)] and cis-[PtBr2(5-dppn)] have been characterized by elemental analyses, conductivity measurements, infrared, electronic and 1H-NMR spectra. 相似文献