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   657篇
  免费   98篇
  国内免费   74篇
化学   492篇
晶体学   2篇
力学   41篇
综合类   11篇
数学   28篇
物理学   255篇
  2024年   1篇
  2023年   4篇
  2022年   16篇
  2021年   13篇
  2020年   21篇
  2019年   19篇
  2018年   16篇
  2017年   12篇
  2016年   33篇
  2015年   27篇
  2014年   32篇
  2013年   45篇
  2012年   51篇
  2011年   56篇
  2010年   49篇
  2009年   27篇
  2008年   36篇
  2007年   49篇
  2006年   37篇
  2005年   31篇
  2004年   35篇
  2003年   23篇
  2002年   26篇
  2001年   19篇
  2000年   14篇
  1999年   16篇
  1998年   8篇
  1997年   23篇
  1996年   12篇
  1995年   4篇
  1994年   13篇
  1993年   9篇
  1992年   9篇
  1991年   13篇
  1990年   6篇
  1989年   2篇
  1988年   8篇
  1987年   2篇
  1985年   2篇
  1984年   1篇
  1983年   3篇
  1978年   1篇
  1975年   1篇
  1973年   3篇
  1971年   1篇
排序方式: 共有829条查询结果,搜索用时 15 毫秒
51.
Two new acids 1 and 2, together with a known compound, purpactin A (3), were isolated from endophytic fungus No. ZZF13. Their structures were elucidated on the basis of 1D, 2D NMR, and HREIMS spectra. Published in Khimiya Prirodnykh Soedinenii, No. 4, pp.336-337, July-August, 2008. Original articlesubmitted April 24, 2007.  相似文献   
52.
光致异构全光逻辑门理论与实验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
李燕明  陈理想  佘卫龙 《物理学报》2007,56(10):5895-5902
基于双光抽运探测模型,利用偶氮苯聚合物光致异构和光致双折射效应,建立了全光逻辑门的理论分析模型,提出了一种新颖的全光逻辑门设计方案.该方案基于输入抽运光和信号光的强度或偏振态,设计了“与”门、“或”门、“异或”门和“异或非”门等基本功能的全光逻辑门.以掺杂分散红1(DR1)的聚甲基丙烯酸甲酯(PMMA)薄膜为样品进行实验,得到了比较好的逻辑门运算实验结果,与理论分析相符合.  相似文献   
53.
Zhang  Ancai  Lai  Xuzhi  Wu  Min  She  Jinhua 《Nonlinear dynamics》2017,88(3):2241-2254
Nonlinear Dynamics - This paper investigates the generation of some novel bursting patterns in active control oscillator with multiple time delays. We present the bursting patterns, including...  相似文献   
54.
An efficient magnesium bistrifluoromethanesulfonimide[Mg(NTf_2)_2]catalyzed hydroalkylation of aromatic olefins with 1,3- diketones under solvent-free conditions has been developed.The reactions proceed smoothly to give the desired products in good yields in short reaction times.  相似文献   
55.
Mammalian reovirus is an enteric virus that contains a double-stranded RNA genome. The genome consists of ten RNA segments that encode eight structural and three non-structural proteins. The structural proteins form a double-layered structure. The innermost layer, called the core, consists of five proteins (lambda1, lambda2, lambda3, micro 2, and sigma2). Protein lambda3 is the RNA-dependent RNA polymerase (RdRp) and micro 2 is thought to be an RdRp cofactor. Translation of most reovirus proteins is known to commence at the first start codon. However, the translation initiation site of the viral core protein micro 2, encoded by the M1 RNA segment, has been in dispute. Although the theoretical molecular weight of micro 2 is 83 267 Da the actual molecular weight is unknown because micro 2 runs aberrantly in SDS-PAGE and has resisted characterization by Edman degradation, indicating that the amino terminus is post-translationally modified. In this study, we used proteolysis coupled with MALDI-Qq-TOFMS to determine that translation of micro 2 initiates at the first AUG codon, that its actual molecular weight approximates the theoretical value of 83 kDa, that the amino terminal methionine residue is removed, and that the next amino acid (alanine) is post-translationally acetylated.  相似文献   
56.
Our velocity measurements on quasi-two-dimensional turbulent flow in a rapidly rotating annulus yield self-similar (scale-independent) probability distribution functions for longitudinal velocity differences, deltav(l) = v(x+l)-v(x). These distribution functions are strongly non-Gaussian, suggesting that the coherent vortices play a significant role. The structure functions <[deltav(l)](p)> approximately l(zeta)p exhibit anomalous scaling: zeta(p) = p / 2 rather than the expected zeta(p) = p / 3. Correspondingly, the energy spectrum is described by E(k) approximately k(-2) rather than the expected E(k) approximately k(-5/3).  相似文献   
57.
佘守宪 《大学物理》1999,18(7):31-33
通过电四极透镜与磁四极透镜两个实例阐明中心反对称二维非均匀静电场静磁场及其应用。  相似文献   
58.
Lu X  Zhang Y  Zhong L  Luo Y  She C 《Optics letters》2004,29(6):614-616
To simplify the reconstruction calculation of a large-aperture digital hologram we propose a novel Fourier-transformation reconstruction algorithm. When the reconstructed wave is the same as or similar to the reference wave, the higher-order phase term of reconstruction can be compensated for. For example, the variation between the higher-order phase term and the aperture angle with a different field of view in in-line phase-shifting digital holography is analyzed.  相似文献   
59.
In this paper, we obtain an Euler product with functional equation associated to a noncuspidal metaplectic form on the double cover of . Zagier's idea of Rankin-Selberg method is used to define the convolution of and the -function.

  相似文献   

60.
She WL  Lee KK  Lee WK 《Physical review letters》2000,85(12):2498-2501
We have created a one- (rather than two-) dimensional quasi-steady-state photorefractive spatial soliton induced by a laser beam instead of an applied electric field. The formation of this type of spatial soliton depends on the intensity of the self-trapped beam, which is different from quasi-steady-state spatial solitons reported in the literature. The optically induced spatial soliton can be exploited in all optical switching applications.  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