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   6145篇
  免费   785篇
  国内免费   505篇
化学   3261篇
晶体学   54篇
力学   237篇
综合类   23篇
数学   527篇
物理学   1487篇
无线电   1846篇
  2024年   14篇
  2023年   164篇
  2022年   189篇
  2021年   235篇
  2020年   207篇
  2019年   199篇
  2018年   177篇
  2017年   146篇
  2016年   242篇
  2015年   264篇
  2014年   319篇
  2013年   352篇
  2012年   425篇
  2011年   482篇
  2010年   306篇
  2009年   346篇
  2008年   396篇
  2007年   364篇
  2006年   345篇
  2005年   294篇
  2004年   226篇
  2003年   205篇
  2002年   167篇
  2001年   145篇
  2000年   126篇
  1999年   165篇
  1998年   140篇
  1997年   121篇
  1996年   122篇
  1995年   100篇
  1994年   72篇
  1993年   64篇
  1992年   57篇
  1991年   49篇
  1990年   35篇
  1989年   26篇
  1988年   21篇
  1987年   22篇
  1986年   16篇
  1985年   10篇
  1984年   19篇
  1983年   7篇
  1982年   7篇
  1981年   4篇
  1980年   9篇
  1979年   3篇
  1976年   9篇
  1975年   5篇
  1974年   4篇
  1970年   2篇
排序方式: 共有7435条查询结果,搜索用时 0 毫秒
81.
82.
A coefficient inverse problem of the one-dimensional parabolic equation is solved by a high-order compact finite difference method in this paper. The problem of recovering a time-dependent coefficient in a parabolic partial differential equation has attracted considerable attention recently. While many theoretical results regarding the existence and uniqueness of the solution are obtained, the development of efficient and accurate numerical methods is still far from satisfactory. In this paper a fourth-order efficient numerical method is proposed to calculate the function u(x,t) and the unknown coefficient a(t) in a parabolic partial differential equation. Several numerical examples are presented to demonstrate the efficiency and accuracy of the numerical method.  相似文献   
83.
The issue of impulsive control theory for the synchronization of the nuclear spin generator (NSG) chaotic systems is developed. We propose an impulsive control scheme for the complete synchronization of the NSG system including chaotic systems. A sufficient condition for the impulsive control is derived, with an easily calculated maximum impulsive interval. The proposed impulsive control scheme is applied to the NSG system and the simulation result demonstrates the effectiveness of the method.  相似文献   
84.
Journal of Signal Processing Systems - New programming models have been developed to embrace contemporary heterogeneous machines, each of which may contain several types of processors, e.g., CPUs,...  相似文献   
85.

In order to select a chelator with excellent stability, easier radiolabeling process and low cost, GRPr antagonist RM26 with the amino acid based chelator was radiolabeled with technetium-99m. The stability of the radiolabeled peptides in PBS, serum as well as in the presence of excess cysteine was compared.

  相似文献   
86.
邱锦辉  廖廷俤 《中国激光》1991,18(8):620-625
本文采用抛物型等效法研究指数型梯度折射率纤维的成像特性。这种方法计算比严格解析法方便,精度比锥形等效法高,且适用范围大。  相似文献   
87.
Watermarking with both oblivious detection and high robustness capabilities is still a challenging problem. In this paper, we tackle the aforementioned problem. One easy way to achieve blind detection is to use denoising for filtering out the hidden watermark, which can be utilized to create either a false positive (copy attack) or false negative (denoising and remodulation attack). Our basic design methodology is to exploit prior knowledge available at the detector side and then use it to design a "nonblind" embedder. We prove that the proposed scheme can resist two famous watermark estimation-based attacks, which have successfully cracked many existing watermarking schemes. False negative and false positive analyses are conducted to verify the performance of our scheme. The experimental results show that the new method is indeed powerful.  相似文献   
88.
对东乡野生稻的越冬性能进行了连续2年的观察,结果表明:东乡野生稻的稻蔸能在武汉地区安全越冬,翌年春季再生苗从地表以下的茎节长出.越冬再生植株与种子实生植株相比并无差异.  相似文献   
89.
The siglec family of sialic acid binding proteins participates in diverse cell surface biology that includes regulation of immune cell signaling and the interaction of neuronal cells with glial cells. The weak intrinsic affinity of the natural sialoside ligands has hampered the development of synthetic ligand based probes needed to elucidate their roles in siglec function. In this report, we describe a glycan microarray comprising a library of 9-acyl-substituted sialic acids incorporated into sialosides containing the Neu5Acalpha2-3Gal and Neu5Acalpha-6Gal linkages commonly recognized by the siglecs. The array is demonstrated to exhibit utility for detecting 9-acyl substituents that increase the affinity of siglecs for their ligands. Substituents that increase affinity are anticipated to be useful for the design of high affinity ligand based probes of siglec function.  相似文献   
90.
Glycans arrayed on the exterior of virus particles were used as substrates for glycosyltransferase reactions to build di- and trisaccharides from the virus surface. The resulting particles exhibited tight and specific associations with cognate receptors on beads and cells, in one example defeating in cis cell-surface interactions in a manner characteristic of polyvalent binding. Combined with the ability of viruses to provide structurally well-defined attachment points, the methodology provides a convenient and powerful way to prepare complex carbohydrate ligands for clustered receptors.  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