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211.
We discuss the impact of density functional electronic structure calculations for understanding the organometallic chemistry of transition metal (TM) surface complexes and clusters. Examples will cover three types of systems, mainly of interest in the context of heterogeneous catalysis: (i) supported carbonyl complexes of rhenium on MgO and of rhodium in zeolites, (ii) TM clusters with CO ligands and adsorbates, and (iii) metal clusters exhibiting chemical bonds with atomic carbon. The first group of case studies promotes the concept that surface groups of oxide supports are bonded to TM complexes in the same way as common (poly-dentate) ligands are bonded in coordination compounds. The second group of examples demonstrates various “ligand effects” of TM clusters. Finally, we illustrate how carbido centers stabilize TM clusters and modify the propensity for adsorption at the surface of such clusters. 相似文献
212.
19F NMR Spectroscopic Evidence and Calculation of the Statistical Formation of Mixed Cluster Anions [(Mo6Br Cl )F ]2?, n = 0 – 8 The complete system of the innersphere mixed clusters (Mo6BrCl)4+ is formed by exchange of innersphere bound Cli against outersphere bound Bra on tempering the solid [(Mo6Cl)Br] at 500°C for 16 h. After conversion with conc. HCl into (H3O)2[(Mo6BrCl)Cl] and precipitation of the outer Cla with AgBF4 in ethanol, treatment with tetrabutylammonium(TBA)fluoride yields (TBA)2 [(Mo6BrCl)F], a mixture of 22 different species. According to the sets of chemical equivalent fluorine atoms in total 55 19F nmr signals are expected, which are really observed in the high resolution 1D-19F-nmr spectrum. Using increments of chemical shifts, peak intensities and multiplet structures as well as the 2D-19F/19F-COSY spectrum the complete and unambiguous assignment of all resonances is achieved. From the measured integral intensities the distribution of the different compounds is determined, revealing statistical formation of the geometrical isomers. 相似文献
213.
Koridze A. A. Zdanovich V. I. Lagunova V. Yu. Petukhova I. I. Dolgushin F. M. Starikova Z. A. Ezernitskaya M. G. Petrovskii P. V. 《Russian Chemical Bulletin》2002,51(5):876-886
The thermal reaction of Ru3(CO)10(-Ph2PCH2PPh2) (1) with enyne PhCH=CHCCPh afforded the trinuclear ruthenium clusters Ru3(CO)6{3-P(Ph)CH2PPh2}{3-C(Ph)=CHCC(Ph)(1,2-C6H4)C(=0)} (2), Ru3(-H)(CO)5{3-P(Ph)CH2PPh2}{3-C(Ph)=CHCC(Ph)(1,2-C6H4)C(—0)} (3), and Ru3(CO)6(-CO){3-P(Ph)CH2PPh2}{3-C(C=CPh2)CH=C(H)Ph} (4) and also two isomers of Ru3(CO)5(-CO)(-Ph2PCH2PPh2){3-C4Ph2(CH=CHPh)2} (5a and 5b). Clusters 2, 3, and 4 were characterized by IR spectroscopy, 1H and 31P NMR spectroscopy, and X-ray diffraction analysis. The reaction of complex 1 with enyne FcCH=CHCCFc gave rise to the Ru3(CO)6{3-P(Ph)CH2PPh2}{3-C(Fc)=CHCC(Fc)(1,2-C6H4)C(=0)} (6) and Ru3(-H)(CO)5{3-P(Ph)CH2PPh2}{3-C(Fc)=CHCC(Fc)(1,2-C6H4)C(—0)} (7) clusters. According to the spectral data, the latter compounds are isostructural to complexes 2 and 3, respectively. 相似文献
214.
215.
Preparation and characterization of the first derivatives of the fused macropolyhedral anion [B22H22]2− are reported. The species [B22H21OH]2− (1) and [B22H21OEt]2− (2) are obtained from workup of the products of the reaction between HgBr2 and [NBzlEt3]2[B22H22]; a cluster involving the conjoining of a closo-B12 icosahedron with a nido-B10 cluster. Washing the products with ethanol followed by thin-layer chromatography allows the isolation of 1 and 2, reproducibly, in yields of 27 and 20%, respectively. The species were characterized by NMR spectroscopy, elemental analysis and X-ray diffraction studies. The crystal structure determinations of the two species identify novel features. Apparently the influence of the O atoms in the ions [B22H21OH]2− and [B22H21OEt]2− results in the lengthening of what was a gunwale B---B connection adjacent to the junction of the two cages such that the distances are 2.180 and 2.230 Å, respectively. These latter are longer than the corresponding distance in the parent species [B22H22]2−, which is 2.09 Å; quite long for a normal B---B distance. Thus it is assumed that these B atoms, in 1 and 2, one of which bears the substituent, are not bonded to each other. 相似文献
216.
The LiHe+
n
, the NaHe+
n
, and the MgHe+
n
complexes with n=1, 2, 3, 4 were studied using ab initio calculations with the MP2/6-311+G(3df, 3pd) method. The complexes are found to be stable. For the n=1 complexes, previous results were available and the calculations performed are in good agreement with those results. This lends credibility to the results obtained for the complexes with higher n. 相似文献
217.
采用ab initio RHF,MP2和B3LYP方法以及LanL2DZ和SDD基组计算了四面体锌族卤素阴离子化合物(MX42-,M=Zn(Ⅱ),Cd(Ⅱ),Hg(Ⅱ);X=F-,Cl-,Br-,I-)和钛族卤化物(MX4,M=Ti(Ⅳ),Zr(Ⅳ),Hf(Ⅳ);X=F-,Cl-,Br-,I-)的几何构型和振动频率。计算结果表明,LanL2DZ基组是合适的基组,能得到合理的电荷分布,几何参数以及振动频率。在锌族卤化物的计算中发现,角弯曲振动频率与实测值相当一致,键伸缩振动频率略为偏低,这主要是由于计算的键长略为偏长所致。MP2方法计算的振动频率更接近于实测值。在钛族卤化物的计算中,三种计算方法都相当地再现了实测值,而以B3LYP方法更为满意。 相似文献
218.
Jingyi Cai Haoshan Wei Prof. Yong Zhang Rui Cai Dr. Xueru Zhang Prof. Yan Wang Prof. Jiaqin Liu Prof. Hark Hoe Tan Prof. Ting Xie Prof. Yucheng Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7300-7306
Efficient separation of photogenerated electron–hole pairs is a crucial factor for high-performance photocatalysts. Effective electron–hole separation and migration could be achieved by heterojunctions with suitable band structures. Herein, a porous SrTiO3/SrSO4 heterojunction is prepared by a sol-gel method at room temperature followed by an annealing process. XRD characterization suggests high crystallinity of the heterostructure. A well-defined interface between the two phases is confirmed by high-resolution (HR)TEM. The photocatalytic H2 evolution productivity of the SrTiO3/SrSO4 heterojunction with Pt as co-catalyst reaches 396.82 μmol g−1 h−1, which is 16 times higher than that of SrTiO3/Pt. The boosted photocatalytic activity of SrTiO3/SrSO4/Pt can be ascribed to the presence of SrSO4, which promotes the transfer and migration of photogenerated carriers by forming the heterojunction and porous structure, which provides a large amount of active sites. This novel porous heterostructure brings new ideas for the development of high-efficiency photocatalysts for H2 release. 相似文献
219.
220.
《Angewandte Chemie (International ed. in English)》2017,56(43):13249-13252
The reaction of [(DippForm)2Ln(thf)2] with an excess of elemental sulfur in toluene resulted in the formation of the trinuclear polysulfide coordination clusters [(DippForm)3Ln3S12] (Ln=Sm, Yb; DippForm=N,N′‐bis(2,6‐diisopropylphenyl)formamidinate). These are the first f element coordination clusters (LnnSx) with a larger polysulfide unit (n and x>2). The formation of the coordination clusters can be rationalized by the reductive cleavage of S8 with divalent lanthanides. 相似文献