全文获取类型
收费全文 | 2683篇 |
免费 | 87篇 |
国内免费 | 13篇 |
专业分类
化学 | 2057篇 |
晶体学 | 35篇 |
力学 | 33篇 |
数学 | 173篇 |
物理学 | 485篇 |
出版年
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 27篇 |
2019年 | 46篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 54篇 |
2015年 | 44篇 |
2014年 | 60篇 |
2013年 | 155篇 |
2012年 | 132篇 |
2011年 | 150篇 |
2010年 | 103篇 |
2009年 | 84篇 |
2008年 | 143篇 |
2007年 | 127篇 |
2006年 | 122篇 |
2005年 | 133篇 |
2004年 | 111篇 |
2003年 | 108篇 |
2002年 | 96篇 |
2001年 | 38篇 |
2000年 | 35篇 |
1999年 | 42篇 |
1998年 | 32篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 25篇 |
1994年 | 39篇 |
1993年 | 33篇 |
1992年 | 43篇 |
1991年 | 34篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 45篇 |
1983年 | 26篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 29篇 |
1977年 | 22篇 |
1976年 | 31篇 |
1975年 | 29篇 |
1974年 | 26篇 |
1973年 | 25篇 |
1972年 | 19篇 |
排序方式: 共有2783条查询结果,搜索用时 46 毫秒
201.
202.
The growth, movement and nature of outside dislocation, which propagate from heavily phosphorus (>1015 ions/cm2) implanted (111), (100), and (110) silicon layers into unimplanted outside regions by a compressive strain induced during
1100° C wet O2 annealing, are investigated using transmission electron microscopy and x-ray diffraction topography. Outside dislocations
are formed, mainly on (111) planes., by the glide motion of dislocation networks formed in implanted layers during early annealing.
This results in dislocations extending into the unimplanted areas to different degrees, in the order of, from the largest
to smallest, (111), (110), and (100) wafers. In (110) wafers, the [001] oriented dislocations in the implanted regions rise
to the surface at the implant and unimplant boundary. On the other hand, the [110] dislocations penetrate into the unimplanted
region. Two sets of orthogonal 〈110〉 oriented dislocations generated in (100) implanted wafers behave in the same manner as
the [001] dislocations in (110) wafers. Some sources of the compressive strain related to the generation of these dislocations
are discussed. 相似文献
203.
Ikuma N Tsue H Tsue N Shimono S Uchida Y Masaki K Matsuoka N Tamura R 《Organic letters》2005,7(9):1797-1800
[reaction: see text] Enantiomerically enriched samples of chiral cyclic nitroxides with a 4-hydroxyphenyl group on the stereogenic center bearing the NO radical group undergo unprecedented spontaneous racemization and/or epimerization in aprotic solvents, which can be well accounted for by the multistep equilibrations involving planar quinoid intermediates. 相似文献
204.
Tamura R Takeuchi T Aoki C Takeuchi S Kiss T Yokoya T Shin S 《Physical review letters》2004,92(14):146402
Ca 2p-3d resonant photoemission spectroscopy of a Cd6Ca crystalline approximant unambiguously demonstrates that the low-lying unoccupied 3d levels of calcium are lowered below the Fermi energy by the formation of the approximant, as suggested from electronic structure calculations [Phys. Rev. Lett. 87, 206408 (2001)]]. Moreover, the Ca 3d partial density of states (DOS) obtained near the Fermi energy is in reasonable agreement with theoretical Ca 3d DOS. These results verify the unconventional picture that the origin of the pseudogap in the Cd-based quasicrystals is due to hybridization of the Ca 3d band with the Cd 5p band. 相似文献
205.
206.
cis-Decalin (2) and perylene (3) are co-enclathrated by a self-assembled M6L4-coordination cage (1) to give 1 superset(2.3) although each of them is not enclathrated. This phenomenon is termed as AND bimolecular recognition because enclathration occurs only if 2 and 3 coexist. Cage 1 also coenclathrates azulene (8) and 1,4-naphthoquinone (9) to give 1 superset(8.9). In this case, 1 superset(8)2 and 1 superset(9)2 are formed by treating 1 with 8 and 9 individually. This case is termed as OR bimolecular recognition because enclathration occurs if 8 or 9 exists. Accordingly, we have shown that the self-assembled cage 1 experiences both AND and OR bimolecular recognition. 相似文献
207.
Terao K Ohsawa A Mori Y Narita T Ichikawa K Dobashi T 《Colloids and surfaces. B, Biointerfaces》2004,37(3-4):129-132
Microcapsules having polyethyleneglycol-grafted poly(ureaurethane) (PUU) membrane and di-2ethylhexyl phthalate core have been prepared, and the structure when they were suspended in dispersing ethanol have been studied by means of single-particle light scattering method. The PUU membrane was synthesized from monomers with aromatic functional groups (microcapsule MC110) and hexamethylene functional groups (microcapsule MC160). Because the outer and inner solvent passed through the membrane easily, the outside and inside of the membrane were the same at the equilibrium state. The thickness of the wall membrane was significantly smaller than that calculated from the overall weight ratio of the wall-forming material and the core solvents. It was attributed to low affinity of PUU membranes and ethanol. 相似文献
208.
Shigendo Enomoto Ken-ichi Kumagai Taro Tamura Miki Hasegawa Kyoko Nakada Toshihiko Hoshi Michio Kobayashi 《Monatshefte für Chemie / Chemical Monthly》2004,29(1):471-481
Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The 1H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the 1H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of CS symmetry, in which the benzene molecule mainly interacts with the electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the 1H NMR spectral shifts mentioned above and the experimentally predicted CS structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure. 相似文献
209.
Takayuki?FurutaEmail author Jung?Il Bong Lambert?Alan 《Integral Equations and Operator Theory》2004,48(2):137-146
In this note we examine the relationships between p-hyponormal
operators and the operator inequality
. This leads to a method for
generating examples of p-hyponormal operators which are not q-hyponormal
for any
. Our methods are also shown to have implications for the class
of Furuta type inequalities. 相似文献
210.
Observation of reduced heat transport inside the magnetic island O point in the large helical device
Inagaki S Tamura N Ida K Nagayama Y Kawahata K Sudo S Morisaki T Tanaka K Tokuzawa T;LHD Experimental Group 《Physical review letters》2004,92(5):055002
Evidence for a reduction of heat transport inside the magnetic island O point is observed from the propagation of a cold pulse produced by a tracer encapsulated solid pellet in the Large Helical Device. A small peak and slow propagation of the cold pulse are observed inside the island. A significant result is that electron heat diffusivity inside the island is estimated to be 0.2 m(2)/s which is smaller than that outside the island by an order of magnitude. 相似文献