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   1505篇
  免费   15篇
  国内免费   11篇
化学   1098篇
晶体学   17篇
力学   19篇
数学   108篇
物理学   289篇
  2023年   8篇
  2021年   10篇
  2020年   8篇
  2019年   20篇
  2018年   12篇
  2017年   7篇
  2016年   18篇
  2015年   16篇
  2014年   22篇
  2013年   58篇
  2012年   59篇
  2011年   77篇
  2010年   35篇
  2009年   52篇
  2008年   83篇
  2007年   98篇
  2006年   112篇
  2005年   117篇
  2004年   75篇
  2003年   67篇
  2002年   67篇
  2001年   29篇
  2000年   31篇
  1999年   24篇
  1998年   17篇
  1997年   13篇
  1996年   28篇
  1995年   24篇
  1994年   14篇
  1993年   13篇
  1992年   27篇
  1991年   9篇
  1990年   19篇
  1989年   13篇
  1988年   15篇
  1987年   17篇
  1986年   11篇
  1985年   20篇
  1984年   22篇
  1982年   17篇
  1981年   11篇
  1979年   19篇
  1978年   24篇
  1977年   20篇
  1976年   6篇
  1975年   9篇
  1974年   10篇
  1973年   7篇
  1970年   5篇
  1967年   5篇
排序方式: 共有1531条查询结果,搜索用时 234 毫秒
1.
1,3-Dithiol-2-ylidene derivatives containing bis(ethynylpyridine) units were synthesized using a Pd-catalyzed reaction of the corresponding dibromide. X-Ray crystal analysis revealed unique crystal structures depending on the aromatic groups. The absorption spectra and redox properties indicated intramolecular charge-transfer interactions between the 1,3-dithiole unit and the pyridyl parts.  相似文献   
2.
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at one-loop level.   相似文献   
3.
Kaneko  Masanobu  Koike  Masao 《The Ramanujan Journal》2003,7(1-3):145-164
Modular and quasimodular solutions of a specific second order differential equation in the upper-half plane, which originates from a study of supersingular j-invariants in the first author's work with Don Zagier, are given explicitly. Positivity of Fourier coefficients of some of the solutions as well as a characterization of the differential equation are also discussed.  相似文献   
4.
A new configuration for an ASE reduction filter in EDFA repeaters for WDM optical transmission systems using optical fiber grating couplers (FGCs) was proposed and first demonstrated. The filtering characteristics of the proposed filter for amplified single wavelength signal and 2-channel WDM signals using EDFA were identified. It was found that the filter was effective to improve SNR in optical domain by reducing ASE noise. The required FGC characteristics for the filter were theoretically predicted under the condition that the total filter loss did not exceed 3 dB. More than 70% of drop efficiency was required in each FGC for the application of the proposed filter to an 8-channel WDM system using EDFA repeaters.  相似文献   
5.
6.
7.
8.
It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc.  相似文献   
9.
Let Λ be a left Artinian ring, D+(mod Λ) (resp., D(mod Λ), D(mod Λ)) the derived category of bounded below complexes (resp., bounded above complexes, unbounded complexes) of finitely generated left Λ-modules. We show that the Grothendieck groups K0(D+(mod Λ)), K0(D(mod Λ)) and K0(D(mod Λ)) are trivial. Received: 7 April 2005  相似文献   
10.
F1-Ay mice between RR (aabbCC) and C57BL/6J-Ay (AyaBBCC) have a much darker yellow coat color than do C57BL/6J-Ay. Quantitative trait locus (QTL) analysis was carried out to identify genes responsible for the darker modification of the yellow coat color (this has been traditionally termed “sable”). A significant sable QTL was identified on chromosome 1 (Dmyaq4, LOD score 15.5 for lightness, and 13.4 for color difference), in a chromosomal position similar to that of Dmyaq2, a sable QTL previously identified in C3H/HeJ. Another significant sable QTL was identified on chromosome 4 (Dmyaq5, LOD score 5.6 for lightness, and 4.3 for color difference) near the tyrosinase-related protein 1 (Tyrp1) locus. The effect of Dmyaq5 was significant only in the presence of the RR allele at Dmyaq4, suggesting that the Dmyaq4 (as well as Dmyaq2) is a novel coat color gene that may act up-stream of Tyrp1 signaling to increase eumelanin production.  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