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   15616篇
  免费   655篇
  国内免费   41篇
化学   10517篇
晶体学   202篇
力学   506篇
综合类   1篇
数学   1198篇
物理学   3888篇
  2023年   173篇
  2022年   291篇
  2021年   409篇
  2020年   483篇
  2019年   564篇
  2018年   511篇
  2017年   485篇
  2016年   699篇
  2015年   502篇
  2014年   798篇
  2013年   1368篇
  2012年   1185篇
  2011年   1246篇
  2010年   822篇
  2009年   636篇
  2008年   787篇
  2007年   796篇
  2006年   609篇
  2005年   550篇
  2004年   418篇
  2003年   357篇
  2002年   290篇
  2001年   153篇
  2000年   125篇
  1999年   93篇
  1998年   76篇
  1997年   96篇
  1996年   86篇
  1995年   77篇
  1994年   86篇
  1993年   95篇
  1992年   102篇
  1991年   76篇
  1990年   73篇
  1989年   80篇
  1988年   55篇
  1987年   51篇
  1986年   51篇
  1985年   85篇
  1984年   76篇
  1983年   60篇
  1982年   58篇
  1981年   55篇
  1980年   59篇
  1979年   72篇
  1978年   61篇
  1977年   61篇
  1976年   46篇
  1975年   42篇
  1973年   38篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,...  相似文献   
22.
Russian Journal of Organic Chemistry - A mild and efficient procedure has been developed for the synthesis of 3-amino-1-benzofurans by intramolecular cyclization of the corresponding...  相似文献   
23.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor.  相似文献   
24.
Journal of Thermal Analysis and Calorimetry - This article studies the pattern of heat lines in free convection non-Newtonian flow from a semi-infinite vertical cylinder via Bejan’s heat...  相似文献   
25.
This review article covers the growth and characterization of two-dimensional (2D) crystals of transition metal chalcogenides, h-BN, graphene, etc. The chemical vapor transport method for bulk single crystal growth is discussed in detail. Top-down methods like mechanical and liquid exfoliation and bottom-up methods like chemical vapor deposition and molecular beam epitaxy for mono/few-layer growth are described. The optimal characterization techniques such as optical, atomic force, scanning electron, and Raman spectroscopy for identification of mono/few-layer(s) of the 2D crystals are discussed. In addition, a survey was done for the application of 2D crystals for both creation and deterministic transfer of single-photon sources and photovoltaic systems. Finally, the application of plasmonic nanoantenna was proposed for enhanced solar-to-electrical energy conversion and faster/brighter quantum communication devices.  相似文献   
26.
Detailed investigations of laser–ion interactions require well-defined ion targets and detection techniques for high-sensitivity measurements of reaction educts and products. To this end, we have designed and built the High-Intensity Laser-Ion Trap Experiment Penning trap setup, which features various ion-target preparation techniques including selection, cooling, compression, and positioning as well as destructive and non-destructive measurement techniques to determine the number of stored ions for all charge states individually and simultaneously. We have recently performed first commissioning experiments of ion deceleration and dynamic ion capture with highly charged ion bunches from an electron beam ion source. We have characterized our single-pass non-destructive ion counter in detail and were able to determine the ion velocity as well as the number of ions from the signals acquired.  相似文献   
27.
Molecular Diversity - The antifungals that are in current clinical practice have a high occurrence of a side effect and multidrug resistance (MDR). Researchers across the globe are trying to...  相似文献   
28.
Molecular Diversity - A series of new spirooxindolocarbamates 4a–l and 6a–d were synthesized by using the Betti reaction. All the target compounds were well characterized by IR, NMR and...  相似文献   
29.
In this paper, we study certain interesting and useful properties of incomplete -functions. The incomplete -function is an extension of the -function. We find several useful classical integral transforms of these functions. Further, we examine the fractional calculus with the incomplete -functions and point out several special cases. Finally, we give the applications of incomplete -functions in detecting glucose supply in human blood.  相似文献   
30.
Magnetically retrieval CuFe2O4@MIL-101(Cr) metal–organic framework was successfully prepared from easily available starting materials and characterized using various spectroscopic and analytical techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, elemental mapping, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, vibrating sample magnetometer, and inductively coupled plasma optical emission spectroscopy. The catalyst was then used in the synthesis of benzodiazepines containing a triazole moiety in water. The advantages of this protocol include high yields, reusability of the catalyst, and gram-scale synthesis.  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