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   527693篇
  免费   7297篇
  国内免费   1565篇
化学   251987篇
晶体学   6666篇
力学   19504篇
综合类   18篇
数学   56119篇
物理学   141138篇
无线电   61123篇
  2021年   4423篇
  2020年   5066篇
  2019年   5336篇
  2018年   6854篇
  2017年   6640篇
  2016年   10439篇
  2015年   6597篇
  2014年   10105篇
  2013年   23170篇
  2012年   17939篇
  2011年   21812篇
  2010年   15673篇
  2009年   16073篇
  2008年   21359篇
  2007年   21691篇
  2006年   20269篇
  2005年   18482篇
  2004年   17169篇
  2003年   15275篇
  2002年   14848篇
  2001年   16347篇
  2000年   12926篇
  1999年   10420篇
  1998年   8982篇
  1997年   8665篇
  1996年   8426篇
  1995年   7633篇
  1994年   7549篇
  1993年   7204篇
  1992年   7863篇
  1991年   7818篇
  1990年   7437篇
  1989年   7123篇
  1988年   6947篇
  1987年   6317篇
  1986年   5969篇
  1985年   7656篇
  1984年   7708篇
  1983年   6185篇
  1982年   6187篇
  1981年   6169篇
  1980年   5725篇
  1979年   6017篇
  1978年   6129篇
  1977年   6027篇
  1976年   5917篇
  1975年   5457篇
  1974年   5427篇
  1973年   5401篇
  1972年   3799篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
151.
Crystallography Reports - The formation of Zn-based nanotubes by electrochemical synthesis in pores of template polymer matrices is considered. It is established that the number of defects in the...  相似文献   
152.
Russian Journal of Organic Chemistry - The reaction of selenium dichloride with methyl and ethyl propiolates leads to formation of anti-Markovnikov adducts. The regio- and stereoselective synthesis...  相似文献   
153.

A model with 16 moments is here presented in the framework of RET of polyatomic gases. It furnishes as principal subsystem the relativistic counterpart of a work by Arima T., Ruggeri T., Sugiyama M.; this is present in literature and treats the non relativistic case which incorporates relaxation processes of molecular rotation and vibration. Another principal subsystem is the natural extension of the 14 moments model by Pennisi S. and Ruggeri T.; this is also present in literature in the relativistic framework but where the trace of the third balance equation is neglected. Its extension is found here for the case when this trace isn’t neglected.

  相似文献   
154.
Glück  Jochen  Mironchenko  Andrii 《Positivity》2021,25(5):2029-2059
Positivity - We prove new characterisations of exponential stability for positive linear discrete-time systems in ordered Banach spaces, in terms of small-gain conditions. Such conditions have...  相似文献   
155.
Journal of Thermal Analysis and Calorimetry - Low thermal conductivity is a primary issue in the development of efficient heat transfer fluids and materials required for the thermal management of...  相似文献   
156.
Physics of Atomic Nuclei - The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with 6Li and 10B: charge integration method, pulse gradient analysis,...  相似文献   
157.
Anup Bhat B  Harish SV  Geetha M 《ETRI Journal》2021,43(6):1024-1037
Mining high utility itemsets (HUIs) from transaction databases considers such factors as the unit profit and quantity of purchased items. Two-phase tree-based algorithms transform a database into compressed tree structures and generate candidate patterns through a recursive pattern-growth procedure. This procedure requires a lot of memory and time to construct conditional pattern trees. To address this issue, this study employs two compressed tree structures, namely, Utility Count Tree and String Utility Tree, to enumerate valid patterns and thus promote fast utility computation. Furthermore, the study presents an algorithm called single-phase utility computation (SPUC) that leverages these two tree structures to mine HUIs in a single phase by incorporating novel pruning strategies. Experiments conducted on both real and synthetic datasets demonstrate the superior performance of SPUC compared with IHUP, UP-Growth, and UP-Growth+ algorithms.  相似文献   
158.
Physics of Atomic Nuclei - A two-stage method is proposed for controlling the regulators in the fuel burnup process during a single operating period. At the first stage, the coefficient of the heat...  相似文献   
159.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
160.

The problem of the minimax testing of the Poisson process intensity \({\mathbf{s}}\) is considered. For a given intensity \({\mathbf{p}}\) and a set \(\mathcal{Q}\), the minimax testing of the simple hypothesis \(H_{0}: {\mathbf{s}} = {\mathbf{p}}\) against the composite alternative \(H_{1}: {\mathbf{s}} = {\mathbf{q}},\,{\mathbf{q}} \in \mathcal{Q}\) is investigated. The case, when the 1-st kind error probability \(\alpha \) is fixed and we are interested in the minimal possible 2-nd kind error probability \(\beta ({\mathbf{p}},\mathcal{Q})\), is considered. What is the maximal set \(\mathcal{Q}\), which can be replaced by an intensity \({\mathbf{q}} \in \mathcal{Q}\) without any loss of testing performance? In the asymptotic case (\(T\rightarrow \infty \)) that maximal set \(\mathcal{Q}\) is described.

  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