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991.
An Unusual Trimeric Bimetallic Li? Zr Complex with the Backbone [Zr3(μ2-OH)3(μ3-O)Li5] by Reaction of Zirconiumorgano and Hydrido Complexes with Water The reaction of compounds of the type [(LZr)(LiH)(L′)]n and [(LZr)(LiH)(L′)(alkyne)]n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu3P, alkyne: Ph? C?C? SiMe3, CH?CH) with water at 0°C in a thf solution results in the formation of th trimeric bimetallic complex 8 [(L2Zr)3(μ2-OH)3(μ3-O)Li5(thf)8(H2O)5] in 50% yield. The X-ray analysis of 8 shows that a planar six-membered ring Zr3(μ2-OH)3 is formed. In the middle of this ring is a dianionic oxygen atom placed, coordinating to the three L2Zr centres in a planar μ3-coordination (bond angles 120,05μ). Five lithium ions stabilize the anionic backbone by bridging the biphenolato chelate ligands, which form seven-membered chelate rings with the atoms. 1H-, 13C-, and 7Li-NMR spectra exhibit that the solid state structure remains unchanged in solution (thf). 相似文献
992.
The Isotypic Compounds BaRh2Si2, BaIr2Si2, and BaPt2Ga2 – a Monoclinic Distortion Variant of the CaRh2B2 Structure The new compounds BaRh2Si2 (monoclinic, P21/c, a = 792.6(1) pm, b = 664.5(7) pm, c = 767.9(4) pm, β = 91.2(1)°, Z = 4, 2867 reflexions, 47 parameters, R = 0.024), BaIr2Si2 (monoclinic, P21/c, a = 792.47(6) pm, b = 664.28(6) pm, c = 772.22(6) pm, β = 92.181(7)°, Z = 4, 1939 reflexions, 47 parameters, R = 0.037) and BaPt2Ga2 (monoclinic, P21/c, a = 850.4(1) pm, b = 647.3(1) pm, c = 819.8(1) pm, β = 95.97(1)°, Z = 4, 1506 reflexions, 47 parameters, R = 0.038) were prepared by reaction of the elements. Their structures were determined from single crystal data. The compounds crystallize isotypically with a distortion variant of the CaRh2B2 type of structure. 相似文献
993.
The relative reaction rates of several silatranes (derivatives of 2,8.9-trioxa-5-aza- 1-silatricyclo[3.3.3.01,5]undecane) and HgCl2 in acetone-d6to yield the corresponding organomercury compound are of the order of e.g., 5 × 10?1 1 mol?1 sec?1 or slightly less, a rate that is unexpectedly high compared to the essentially inert parent organotrialkoxysilanes. Thus, the apical Si&.zsbnd;C bond of the silatrane is extraordinarily susceptible to direct electrophilic attack by mercury(II). The rates decrease in the order CH2CH, C6H5, p-ClC6H4 > CH3 > CH3CH2, CH3CH2CH2 > C6H11, ClCH2, Cl2CH, CH3CH2O. The effects of varying the solvent and the counterions are noted, and the probable mechanism is discussed. 相似文献
994.
Dirk Wulff‐Molder Manfred Meisel 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):33-34
In the title complex, tetraphenylphosphonium μ4‐nitrato‐κ4O‐cyclo‐tetrakis(μ‐acetato‐O:O′)tetra‐μ‐oxo‐tetrakis[oxovana‐dium(V)], the anion lies about a twofold axis and consists of the cyclic [V4O8] unit coordinated by four acetato ligands with interatomic V?V distances of 3.269 (1) and 3.273 (1) Å. The double‐bonded O atom [N=O 1.102 (6) and N—O 1.268 (4) Å] of the nitrato ligand links the four V atoms with V—O bond distances of 2.613 (2) and 2.813 (2) Å. The negative charge of the complex is balanced by tetraphenylphosphonium cations occupying the Na positions in the NaCl‐type ionic packing of the structure. 相似文献
995.
Dr. Daniel T. Hog Dipl.‐Chem. Florian M. E. Huber Dr. Peter Mayer Prof. Dr. Dirk Trauner 《Angewandte Chemie (International ed. in English)》2014,53(32):8513-8517
Nitidasin is a pentacyclic sesterterpenoid with a rare 5‐8‐6‐5 carbon skeleton that was isolated from the Peruvian folk medicine “Hercampuri”. It belongs to a small class of sesterterpenoids that feature an isopropyl trans‐hydrindane moiety fused to a variety of other ring systems. As a first installment of our general approach toward these natural products, we report the total synthesis of the title compound. Our stereoselective, convergent route involves the addition of a complex alkenyl lithium compound to a trans‐hydrindanone, followed by chemoselective epoxidation, ring‐closing olefin metathesis, and redox adjustment. 相似文献
996.
Katharina Monczak Katrin Peuntinger Dieter Sorsche Dr. Frank W. Heinemann Prof. Dr. Dirk M. Guldi Prof. Dr. Sven Rau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15426-15433
The synthesis of a trisheteroleptic ruthenium complex [Ru(tb)(dppz)(tmbiH2)][PF6]2 (tb=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazin, tmbiH2=5,6,5′,6′‐tetramethyl‐2,2′‐bibenzimidazole) is described. In addition, the structural characterisation by means of 1D, 2D 1H NMR spectroscopy, and mass spectrometry, along with determination of the solid‐state structure of the important precursor Ru(tb)(dppz)Cl2, supports the proposed octahedral coordination geometry. The capability of tmbiH2 to form hydrogen bonds is corroborated by the solid‐state structure. The photochemical characteristics of this complex can be described as a combination of the “light switch” effects, which are either attributed to the dppz or to the tmbiH2 ligand. To illustrate the molecule’s double switchable features, steady‐state absorption and emission measurements were performed, which include the determination of the quantum yield and the pKa values of the acidic protons of the tmbiH2 ligand. Notably, the emission lifetimes are sensitive to the solvents used. This phenomenon is due to a proton‐coupled deactivation of the excited metal‐to‐ligand charge transfer (MLCT) state of the complex. 相似文献
997.
998.
Dr. Wolfgang Baumann Dr. Dirk Michalik Fabian Reiß Prof. Dr. Axel Schulz Dr. Alexander Villinger 《Angewandte Chemie (International ed. in English)》2014,53(12):3250-3253
Following our interest in nitrogen chemistry, we now describe the synthesis, structure, and bonding of labile disilylated diazene, its GaCl3 adduct, and the intriguing trisilylated diazenium ion [(Me3Si)2N?N‐SiMe3]+, a dark blue and highly labile (Tdecomp>?30 °C) homoleptic cation of the type [R3N2]+. Although direct silylation of Me3Si‐N?N‐SiMe3 failed, the [(Me3Si)2N?N‐SiMe3]+ ion was generated in a straightforward two‐electron oxidation reaction from mercury(II) dihydrazide and Ag[GaCl4]. Moreover, previous structure data of Me3Si‐N?N‐SiMe3 were revised on the basis of new data. 相似文献
999.
Iron 10‐Thiacorroles: Bioinspired Iron(III) Complexes with an Intermediate Spin (S=3/2) Ground State 下载免费PDF全文
Dimitri Sakow Dr. Dirk Baabe Birte Böker Dr. Olaf Burghaus Dr. Markus Funk Dr. Christian Kleeberg Dr. Dirk Menzel Clemens Pietzonka Prof. Dr. Martin Bröring 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2913-2924
A first systematic study upon the preparation and exploration of a series of iron 10‐thiacorroles with simple halogenido (F, Cl, Br, I), pseudo‐halogenido (N3, I3) and solvent‐derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free‐base octaethyl‐10‐thiacorrole by iron insertion and subsequent ligand‐exchange reactions. The small N4 cavity of the ring‐contracted porphyrinoid results in an intermediate spin (i.s., S=3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X‐ray crystallography and magnetometry with 1H NMR‐, EPR‐, and Mössbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. (S=3/2)→high spin (h.s., S=5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S=1/2) state. Chemically, the iron 10‐thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10‐thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites. 相似文献
1000.
Constantin Hetzer Bettina S. Basel Sebastian M. Kopp Frank Hampel Fraser J. White Timothy Clark Dirk M. Guldi Rik R. Tykwinski 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15407-15411
A tetrameric pentacene, PT , has been used to explore the effects of exciton delocalization on singlet fission (SF). For the first time, triplet decorrelation through intramolecular triplet diffusion was observed following SF. Transient absorption spectroscopy was used to examine different decorrelation mechanisms (triplet diffusion versus structural changes) for PT and its dimeric equivalent PD on the basis of the rate and activation barrier of the decorrelation step. Charge‐separation experiments using tetracyano‐p‐quinodimethane ( TCNQ ) to quench triplet excitons formed through SF demonstrate that enhanced intersystem crossing, that is, spin catalysis, is a widely underestimated obstacle to quantitative harvesting of the SF products. The importance of spatial separation of the decorrelated triplet states is emphasized, and independent proof that the decorrelated triplet pair state consists of two (T1) states per molecule is provided. 相似文献