全文获取类型
收费全文 | 405篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 228篇 |
晶体学 | 5篇 |
力学 | 23篇 |
数学 | 71篇 |
物理学 | 88篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 22篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有415条查询结果,搜索用时 15 毫秒
61.
Kopcewicz M. Grabias A. Idzikowski B. Williamson D. L. 《Hyperfine Interactions》2002,139(1-4):525-534
The specialized rf-Mössbauer technique is used to elucidate the magnetic properties of NANOPERM-type nanocrystalline alloys. The influence of alloy composition on the soft magnetic properties is studied for the Fe80M7B12Cu1 (M: Ti, Ta, Nb, Mo, Zr) alloys. The rf-Mössbauer experiments allowed us to distinguish magnetically soft nanoclusters from magnetically harder microcrystalline phases. The measurements performed as a function of the rf field intensity allowed the determination of the distribution of anisotropy fields related to the size distribution of bcc nanoclusters. Smaller anisotropy fields in the nanocrystalline phase were found in Nb-, Zr-, and Mo-containing alloys as compared with the alloys which contain Ti and Ta. The Mössbauer measurements were supplemented by X-ray diffraction determination of the size of nanocrystalline grains. 相似文献
62.
We present a network of delay log2N, whose comparators have only log2N different lengths with maximum length N/2. This network is log-sequential in that it will sort N data items when they are passed through it log2Ntimes. The design, which is related to the Batcher odd-even merge, is distinctly different from the first known example of a log-delay log-sequential network, due to Dowd, Perl, Rudolf, and Saks. It is quite probably the best possible sorting network. 相似文献
63.
We compare the two most widely known planarity testing algorithms, the one due to Hoperoft and Tarjan, and the other to Lempel. Even, and Cederbaum. These two algorithms are generally viewed as very different approaches to the problems of planarity testing and graph embedding. In this paper, however, by utilizing previously unnoticed freedoms of choice in the order in which the operations of the Hoperoft-Tarjan algorithm can be performed, we create a variation of this algorithm which, in terms of the order in which vertices are processed, is indistinguishable on all planar graph inputs from the Lempel -Even-Cederbaum algorithm. This allows one to create hybridized algorithms which, when interpreted as embedding algorithms, combine all of the features of both procedures. 相似文献
64.
The ν2 band of H218O occurring in the region 5–7.5 μ was recorded with a high-resolution vacuum infrared spectrograph and an analysis was presented of the rotational structure observed; comparison of the ground state (000) energy levels determined from the ν2 band with those derived earlier by Fraley, Rao, and Jones from the ν1 and ν2 bands at 2.7 μ was of assistance in this analysis. Values for the energy levels of the first excited state (010) were evaluated. 相似文献
65.
66.
67.
68.
Motivated by heuristic embedding algorithms, this paper is concerned with the organization of potentially large lists of Kuratowski subgraphs of an arbitrary nonpianar graph. A graphical structure called a "nearly Hamiltonian" graph is defined. It is shown that lists of Kuralowski subgraphs can be lexicographically organized in such structures. It is shown that any nonpianar graph contains such structures and at least one such structure with a nonempty list of Kuratowski subgraphs can be located in linear time in ihe edges of the graph. 相似文献
69.
H. Harde H. Burggraf H. W. K. Tom R. K. Jain P. B. Corkum R. S. Taylor Th. Sizer II J. D. Kafka C. Gable G. Mourou D. H. Auston P. R. Smith S. Williamson R. Trebino A. E. Siegman J. Kuhl J. H. Harris S. Sugai A. V. Nurmikko M. G. Li Veerendra K. Mathur Chi H. Lee M. Hasselbach S. C. Hsu H. S. Kwok 《Applied physics. B, Lasers and optics》1982,28(2-3):246-254
70.
Sott R Granander J Williamson C Hilmersson G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(16):4785-4792
The mixed-metal complex formed from n-butylsodium, n-butyllithium, and a chiral amino ether has been studied by NMR spectroscopy. Three different mixed-metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium-amido ethers, lithium-amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are more reactive than the single sodium and lithium amides, whereas the stereoselectivities are higher when lithium amides are used. The alkali-metal/gamma-amido ethers exhibit both higher initial reaction rates and stereoselectivities than their beta-amido ether analogues. NMR spectroscopic studies of mixtures of n-butylsodium (nBuNa), n-butyllithium (nBuLi), and the gamma-amino ethers in diethyl ether show the exclusive formation of dimeric mixed-metal amides. In diethyl ether, the lithium atom of the mixed-metal amide is internally coordinated and the sodium atom is exposed to solvent; however, in tetrahydrofuran, both metals are internally coordinated. 相似文献