全文获取类型
收费全文 | 40820篇 |
免费 | 4215篇 |
国内免费 | 7270篇 |
专业分类
化学 | 34489篇 |
晶体学 | 1910篇 |
力学 | 2228篇 |
综合类 | 320篇 |
数学 | 2880篇 |
物理学 | 10478篇 |
出版年
2024年 | 76篇 |
2023年 | 347篇 |
2022年 | 642篇 |
2021年 | 835篇 |
2020年 | 1158篇 |
2019年 | 1070篇 |
2018年 | 933篇 |
2017年 | 1123篇 |
2016年 | 1566篇 |
2015年 | 1510篇 |
2014年 | 1855篇 |
2013年 | 2966篇 |
2012年 | 3384篇 |
2011年 | 2370篇 |
2010年 | 2035篇 |
2009年 | 2560篇 |
2008年 | 2722篇 |
2007年 | 2815篇 |
2006年 | 2640篇 |
2005年 | 2403篇 |
2004年 | 2369篇 |
2003年 | 2024篇 |
2002年 | 2160篇 |
2001年 | 1377篇 |
2000年 | 1420篇 |
1999年 | 1140篇 |
1998年 | 1015篇 |
1997年 | 829篇 |
1996年 | 823篇 |
1995年 | 729篇 |
1994年 | 689篇 |
1993年 | 520篇 |
1992年 | 539篇 |
1991年 | 318篇 |
1990年 | 261篇 |
1989年 | 200篇 |
1988年 | 194篇 |
1987年 | 134篇 |
1986年 | 123篇 |
1985年 | 91篇 |
1984年 | 65篇 |
1983年 | 41篇 |
1982年 | 40篇 |
1981年 | 32篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1976年 | 11篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
171.
LIAO Qiu-Xia ZHANG Jian QIN Ye-Yan YAO Yuan-Gen 《结构化学》2006,25(7):789-792
1 INTRODUCTION Because of the flexibility of Pb(II) coordination sphere and the nonstereospecific nature of halide anions[1], the chemistry of lead halide complexes has been developed in recent years. Especially PbX2- based coordination polymers with nitrogen-contain- ing Lewis bases have attracted renewed interest[2~11]. The choice of ligand and the reaction condition are of great importance in determining the final topo- logy of the supramolecular materials. But the avail- able struc… 相似文献
172.
ZHOU Ming-Xiua② YANG Chuna DENG Xiao-Yana YU Wei-Feib LI Jin-Shanb a 《结构化学》2006,25(6):647-652
1 INTRODUCTION Silicon and its alloy have been widely applied in such fields as electronic industry, high-temperature structural ceramics, etc. In addition, the researches on silicon and its relevant materials greatly promote the rapid development of modern optics and infor- mation technology. Therefore, more and more at- tention is focused on the structure of silicon, oxide of silicon and the interfaces between silicon and metal or nonmetal. As an ideal passive film on the Si surface, S… 相似文献
173.
S. S. Yarovoi S. F. Solodovnikov Z. A. Solodovnikova Yu. V. Mironov V. E. Fedorov 《Journal of Structural Chemistry》2006,47(1):97-101
A cluster complex of the composition [Th(DMSO)8Cl][Re6Se7Cl7] has been obtained by interaction of ThCl4 solution in DMSO with a water solution of K3[Re6Se7Cl7] and KCl. The compound crystallizes in the rhombic space group Pbcm with unit cell parameters a = 12.262(2) Å, b = 19.653(6) Å, c = 23.603(6) Å, V = 5688(2) Å3, Z = 4, d calc = 3.282 g/cm3. The structure is built from centrosymmetric cluster anions [Re6Se7Cl7]3? and complex cations [Th(DMSO)8Cl]3+ possessing mirror-plane symmetry, half of the DMSO ligands being doubly disordered. 相似文献
174.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
175.
Yong‐Jin Kim Jin‐Woong Kim Jung‐Eun Lee Jee‐Hyun Ryu Junoh Kim Ih‐Seop Chang Kyung‐Do Suh 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5627-5635
Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004 相似文献
176.
A. G. Mirochnik B. V. Bukvetskii E. V. Gukhman V. E. Karasev 《Journal of fluorescence》2003,13(2):157-162
The comparative study of the crystal structures of benzoylacetonato- (1), p-toluylacetonato- (2) and p-ethylbenzoylacetonatoboron (3) difluoride was carried out. Correlation of the luminescence properties of the complexes 1–3 and their crystal structures was revealed. The excimer formation in these compounds occurred the most efficiently for the complexes 1 characterized by the formation of stacks of molecules, unlike the complex 3, where individual dimers behaved as excimer-forming centers. The maximal fluorescence intensity was observed for the complex 2, which had the highest structural ordering. 相似文献
177.
Gunhild U. von Oertzen 《Journal of Physics and Chemistry of Solids》2007,68(3):324-330
Ab initio density functional calculations (plane wave GGA, CASTEP) were performed to determine the effect of O deficiency on the electronic structure of rutile, TiO2. O deficiency was introduced through either the removal of O or the insertion of interstitial Ti atoms. At physically realistic concentrations of O vacancies in the rutile lattice (i.e. 25% and less) O deficiency results in the population of the bottom of the conduction band, the location of the Ti 3d orbitals in the pure structure, increasingly with increasing vacancy concentration. We propose that this could be confused with the formation and population of gap states especially where O vacancies occur in isolated positions in the lattice. In contrast, Ti interstitials introduce a defect state into the energy gap, without an overall reduction in the size of the energy gap. O vacancies result in a spin polarized solution, whereas Ti interstitials do not. 相似文献
178.
The electronic states of the Cr overlayers on TiO2(0 0 1) surfaces have been investigated using angle-resolved and resonant photoemission spectroscopy with synchrotron radiation. At lower coverages, Cr deposition on TiO2(0 0 1) creates two well separated in-gap emissions due to the formation of surface Ti3+ (3d1) ions and Cr3+ (3d3) ions. At higher coverages, the in-gap emission is developed into the 2-peak-structure emission of Cr 3d character. The corresponding state is considered to be of metallic nature from the viewpoint of the high ability of oxygen adsorption, but has no Fermi edge, indicating a possibility of forming small Cr clusters on TiO2(0 0 1) at this stage. 相似文献
179.
Zhen‐Feng Chen Hong‐Li Zhou Hong Liang Yan Li Ren‐Gen Xiong Xiao‐Zeng You 《应用有机金属化学》2003,17(11):883-884
The centrosymmetric binuclear structure of [Pb2(H‐Norf)2(ONO2)4]shows the geometry around each lead(II) atom to be distorted trigonal bipyramidal with Pb–O distances ranging from 2.357(3) to 2.769(4) Å. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
180.
N. Nishi J. Nishijo K. Judai C. Okabe O. Oishi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):287-290
UV photoexcitation of (t-butylethynyl copper)24
cluster films induces segregation of the crystals into metallic and organic
phases and leads to evolve the metallic sheets sandwiched by organic
polymers. The growth of the metallic crystals in the plane of the
photo-electromagnetic field is attributed due to plasmon-plasmon interaction
among nanoparticles embedded in dielectric polymer matrices. The surface
enhanced photochemical reaction of residual cluster molecules on the photon
incident direction is expected to take an important role for joining the
metal particles to produce a metallic sheet. We can apply this phenomenon
for photolithographic copper pattern generation on a flexible base plate. 相似文献