首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   126520篇
  免费   1569篇
  国内免费   455篇
化学   69489篇
晶体学   2045篇
力学   4981篇
综合类   5篇
数学   12247篇
物理学   39777篇
  2016年   1306篇
  2015年   1003篇
  2014年   1350篇
  2013年   4858篇
  2012年   3451篇
  2011年   4444篇
  2010年   2779篇
  2009年   2556篇
  2008年   4002篇
  2007年   4034篇
  2006年   4102篇
  2005年   4020篇
  2004年   3502篇
  2003年   3195篇
  2002年   3088篇
  2001年   3610篇
  2000年   2707篇
  1999年   2217篇
  1998年   1906篇
  1997年   1897篇
  1996年   1841篇
  1995年   1796篇
  1994年   1583篇
  1993年   1584篇
  1992年   1796篇
  1991年   1764篇
  1990年   1707篇
  1989年   1705篇
  1988年   1701篇
  1987年   1709篇
  1986年   1611篇
  1985年   2159篇
  1984年   2294篇
  1983年   1904篇
  1982年   2222篇
  1981年   2040篇
  1980年   2093篇
  1979年   2069篇
  1978年   2203篇
  1977年   2115篇
  1976年   2137篇
  1975年   2067篇
  1974年   1910篇
  1973年   2125篇
  1972年   1286篇
  1971年   982篇
  1970年   922篇
  1969年   927篇
  1968年   1055篇
  1967年   1107篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Ohne Zusammenfassung übersetzt von H. Kauffmann (Leipzig).  相似文献   
105.
106.
We compute neutral Higgs and Z0-boson couplings to quarks in a model with three quark-lepton families and one mirror family. Mixing between ordinary and mirrorquarks leads to flavour-changing couplings which are negligible for the known quarks. However, t-quark couplings are sizeable and the branching ratio for the decay can be as large as 10−4.  相似文献   
107.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported.  相似文献   
108.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
109.
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting.  相似文献   
110.
The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei 9Be or 10Be, respectively. Molecular rotational bands up to high excitation energies are observed with 9Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with 10Be as the core. For 11Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2+, 5/2?, and 3/2?, respectively. Furthermore, we have studied particle-hole states of 16C using the 13C(12C, 9C)16C reaction and found 14 previously unknown states. Using the 12C(12C, 9C)15C reaction, five new states were observed for 15C.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号