全文获取类型
收费全文 | 454531篇 |
免费 | 2781篇 |
国内免费 | 918篇 |
专业分类
化学 | 224474篇 |
晶体学 | 6674篇 |
力学 | 23369篇 |
综合类 | 9篇 |
数学 | 61686篇 |
物理学 | 142018篇 |
出版年
2020年 | 4531篇 |
2019年 | 5395篇 |
2018年 | 7674篇 |
2017年 | 7806篇 |
2016年 | 10236篇 |
2015年 | 5126篇 |
2014年 | 9146篇 |
2013年 | 18852篇 |
2012年 | 14832篇 |
2011年 | 17558篇 |
2010年 | 13740篇 |
2009年 | 13859篇 |
2008年 | 17049篇 |
2007年 | 16829篇 |
2006年 | 15444篇 |
2005年 | 13691篇 |
2004年 | 12752篇 |
2003年 | 11743篇 |
2002年 | 11898篇 |
2001年 | 11971篇 |
2000年 | 9577篇 |
1999年 | 7143篇 |
1998年 | 6481篇 |
1997年 | 6401篇 |
1996年 | 5917篇 |
1995年 | 5108篇 |
1994年 | 5240篇 |
1993年 | 5236篇 |
1992年 | 5427篇 |
1991年 | 5814篇 |
1990年 | 5682篇 |
1989年 | 5705篇 |
1988年 | 5410篇 |
1987年 | 5430篇 |
1986年 | 5146篇 |
1985年 | 6291篇 |
1984年 | 6637篇 |
1983年 | 5529篇 |
1982年 | 5928篇 |
1981年 | 5511篇 |
1980年 | 5158篇 |
1979年 | 5764篇 |
1978年 | 6005篇 |
1977年 | 6138篇 |
1976年 | 6185篇 |
1975年 | 5811篇 |
1974年 | 5679篇 |
1973年 | 5961篇 |
1972年 | 4619篇 |
1971年 | 4151篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Differential cross sections of nucleons excited in photonuclear reactions in medium and heavy nuclei are studied by considering all relevant reaction mechanisms leading to the excitation of protons or neutrons. We take advantage of previous microscopic studies for the absorption and scattering of photons and photoproduced pions, and implement a simulation code in order to take into account the propagation of the nucleons as well as their collisions with other nucleons in the nuclear medium, which generate secondary excited nucleons. Comparison with experimental data is done. Cross sections for nucleon emission in coincidence with one pion are also calculated, and some coincidence observables are discussed. 相似文献
992.
993.
994.
995.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. E. Stronach M. Davis S. Uchida H. Takagi Y. Tokura Y. Hidaka T. Murakami E. A. Early J. T. Markert M. B. Maple C. L. Seaman 《Hyperfine Interactions》1991,63(1-4):311-317
We report muon spin relaxation/rotation measurements on sintered powder samples of Nd2−x
Ce
x
CuO4−y
and a large single crystal of Nd2CuO4−y
. We find an electronic phase diagram which is quite similar to that of hole-doped superconductors such as La2−x
Sr
x
CuO4−y
, although the doping of electrons into the system is less efficient in destroying the static moments on the copper spins.
Static magnetic order in Nd2CuO4−y
appears below about 250 K, and two spin reorientations are seen atT=75 K andT=35 K. Measurements of the magnetic field penetration depth have been unsuccessful due to the rare-earth paramagnetism of
these materials. 相似文献
996.
E. I. Kats 《JETP Letters》1997,65(9):725-728
The properties of a nematic liquid crystal in a porous matrix are discussed. On scales exceeding a certain characteristic
scale the liquid crystal behaves as a nematic glass. Application of a weak magnetic field restores long-range orientational
order.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 695–698 (10 May 1997) 相似文献
997.
998.
Keka Chakraborty S K Paranjpe V Siruguri O D Jayakumar S K Kulshreshtha 《Pramana》1997,48(6):1115-1122
Neutron diffraction and M?ssbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic
moment on the transition metal atom is found to be low, 0.2μ
B, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies
from 2.5μ
B at 296 K to 7.27μ
B at 10 K. M?ssbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine
field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic
interactions between the transition metal atoms. 相似文献
999.
S. Withington J. A. Murphy A. Egan R. E. Hills 《International Journal of Infrared and Millimeter Waves》1992,13(10):1515-1537
In this paper, we summarize the issues that should be considered when designing broadband quasioptical systems for submillimetre-wave radioastronomy receivers. We cover topics such as bandwidth, cross-talk, truncation, and aberrations, and we argue that it should be possible to manufacture high-efficiency systems that have several octaves of bandwidth. A key feature of the paper is that we use the language of multimode Gaussian optics throughout, and in this way, we emphasize that a receiver is a diffraction-limited imaging system rather than just a collection of components for guiding Gaussian beams. The whole discussion is conducted in terms of a particular system we are constructing for the James Clerk Maxwell Telescope in Hawaii. 相似文献
1000.
Carl E. Gordon 《Geometriae Dedicata》1992,42(2):187-203
The symmetric group on k symbols is made to operate on a certain set of matrices in such a way that its orbits are in one-to-one correspondence with the orbits of the k-arcs of an N-dimensional projective space under the group of projectivities. This leads to a formula for the number of such orbits. 相似文献