全文获取类型
收费全文 | 368324篇 |
免费 | 3031篇 |
国内免费 | 742篇 |
专业分类
化学 | 190246篇 |
晶体学 | 5956篇 |
力学 | 17506篇 |
综合类 | 18篇 |
数学 | 41559篇 |
物理学 | 116812篇 |
出版年
2020年 | 3303篇 |
2019年 | 3895篇 |
2018年 | 5877篇 |
2017年 | 6149篇 |
2016年 | 7463篇 |
2015年 | 4018篇 |
2014年 | 6869篇 |
2013年 | 15492篇 |
2012年 | 12030篇 |
2011年 | 14068篇 |
2010年 | 10698篇 |
2009年 | 10860篇 |
2008年 | 12746篇 |
2007年 | 12593篇 |
2006年 | 11532篇 |
2005年 | 12873篇 |
2004年 | 12167篇 |
2003年 | 10182篇 |
2002年 | 8801篇 |
2001年 | 10373篇 |
2000年 | 7750篇 |
1999年 | 5986篇 |
1998年 | 5054篇 |
1997年 | 4877篇 |
1996年 | 4574篇 |
1995年 | 4246篇 |
1994年 | 4120篇 |
1993年 | 3954篇 |
1992年 | 4632篇 |
1991年 | 4839篇 |
1990年 | 4687篇 |
1989年 | 4757篇 |
1988年 | 4670篇 |
1987年 | 4709篇 |
1986年 | 4408篇 |
1985年 | 5621篇 |
1984年 | 5653篇 |
1983年 | 4631篇 |
1982年 | 4770篇 |
1981年 | 4743篇 |
1980年 | 4364篇 |
1979年 | 4964篇 |
1978年 | 5099篇 |
1977年 | 5245篇 |
1976年 | 5163篇 |
1975年 | 4779篇 |
1974年 | 4667篇 |
1973年 | 4787篇 |
1972年 | 3619篇 |
1968年 | 3185篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
992.
N. S. Maslova A. I. Oreshkin S. I. Oreshkin V. I. Panov I. V. Radchenko S. V. Savinov 《JETP Letters》2006,84(6):320-323
We report the results of STM investigation of the initial stage of Ag adsorption on an Si(110) surface. At 0.21 ML Ag coverage,
the size and orientation of the unit cell correspond to the parameters of a 16 × 2 unit cell of clean Si(110) surface. With
increasing of the Ag coverage up to 0.42 ML, the type of surface reconstruction changes to a 4 × 1-Si(110)-Ag structure.
The text was submitted by the authors in English. 相似文献
993.
A. I. Khachaturov 《Technical Physics》2006,51(2):226-230
The contribution of electrons moving at large angles to the barrier junction plane to the tunnel current is calculated. This contribution turns out to be small only if the Fermi energy of the electrons equals several electron volts. Otherwise, specifically, when the Fermi energy is no higher than 1–2 eV, this contribution dominates in high and thin potential barriers. It is found that the tunnel magnetic resistance in ferromagnet-insulator-ferromagnet contacts correlates with this contribution. It is this correlation that is responsible for a decrease in this contribution as the potential barriers get lower and thicker. 相似文献
994.
E. N. Popova V. E. Yudin N. V. Kukarkina T. A. Kostereva I. V. Gofman V. V. Kudryavtsev 《Russian Journal of Applied Chemistry》2006,79(3):439-444
A series of foamed organoplastics based on a combination of foamed fully aromatic polyimide binders and Arimid T polyimide felt were prepared. New composite foamed organoplastics reinforced with montmorillonite nanoparticles were prepared using commercially available aromatic monomers. 相似文献
995.
O. V. Bakbardina I. Yu. Pukhnyarskaya M. A. Gazalieva S. D. Fazylov E. M. Makarov 《Russian Journal of Applied Chemistry》2006,79(10):1726-1728
S-Amino derivatives of O-alkyldithiocarbonic acid were prepared by oxidative condensation of certain alkaloids with sodium xanthates. Some of the compounds synthesized exhibit fungicidal activity. 相似文献
996.
S.N. Abdulmadjid M.M. Suliyanti K.H. Kurniawan T.J. Lie M. Pardede R. Hedwig K. Kagawa M.O. Tjia 《Applied physics. B, Lasers and optics》2006,82(1):161-166
We report in this paper the results of an experimental study on hydrogen analysis of solid samples in high pressure helium
ambient gas employing the basic scheme of laser induced breakdown spectroscopy (LIBS). It is shown that the metastable excited
state of helium atom can be utilized to induce delayed excitation of the ablated hydrogen atoms, and thereby avoid the Stark
broadening effect as well as overcoming the undesirable mismatch effect, which are responsible for inefficient excitation
respectively. It is further demonstrated that for samples of high boiling-point materials such as zircaloy, successful hydrogen
analysis can be achieved by a newly introduced double excitation technique employing single laser realized in a modified configuration
of the conventional LIBS method.
PACS 51-52 相似文献
997.
998.
Dmitry I. Belov Ronald D. Armstrong 《Computational Optimization and Applications》2006,33(2-3):319-332
This paper introduces a novel approach for extracting the maximum number of non-overlapping test forms from a large collection
of overlapping test sections assembled from a given item bank. The approach involves solving maximum set packing problems
(MSPs). A branch-and-bound MSP algorithm is developed along with techniques adapted from constraint programming to estimate
lower and upper bounds on the optimal MSP solution. The algorithm is general and can be applied in other applications including
combinatorial auctions. The results of computer simulations and experiments with an operational item bank are presented.
An erratum to this article is available at . 相似文献
999.
M. Mayr K. -H. Speidel M. Knopp W. Karle T. Faestermann F. Hagelberg H. -J. Simonis P. N. Tandon J. Gerber 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(2):157-161
[Theg-factor ratio of the first excited 3? and 5? states in40Ca was measured to beg 3/g 5=1.01(10) employing the implantation perturbed angular correlation technique. The static hyperfine fields (SF) in Fe and Gd hosts were used. In addition the lifetime of the 5? state was measured to be τ=426(7)ps. The values of the SF in Gd and Fe hosts were deduced and compared with systematics in this element region. 相似文献
1000.