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   5069篇
  免费   190篇
  国内免费   19篇
化学   3347篇
晶体学   46篇
力学   105篇
数学   665篇
物理学   1115篇
  2023年   41篇
  2022年   146篇
  2021年   135篇
  2020年   120篇
  2019年   134篇
  2018年   114篇
  2017年   114篇
  2016年   208篇
  2015年   154篇
  2014年   168篇
  2013年   313篇
  2012年   321篇
  2011年   407篇
  2010年   245篇
  2009年   261篇
  2008年   355篇
  2007年   323篇
  2006年   278篇
  2005年   239篇
  2004年   219篇
  2003年   163篇
  2002年   141篇
  2001年   76篇
  2000年   80篇
  1999年   53篇
  1998年   34篇
  1997年   36篇
  1996年   37篇
  1995年   35篇
  1994年   32篇
  1993年   38篇
  1992年   40篇
  1991年   16篇
  1990年   16篇
  1989年   17篇
  1988年   11篇
  1987年   13篇
  1986年   13篇
  1985年   10篇
  1984年   26篇
  1983年   14篇
  1982年   10篇
  1981年   10篇
  1980年   9篇
  1978年   4篇
  1977年   9篇
  1976年   5篇
  1975年   5篇
  1974年   6篇
  1972年   4篇
排序方式: 共有5278条查询结果,搜索用时 15 毫秒
1.
2.
3.
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with...  相似文献   
4.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
5.
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin.  相似文献   
6.
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples are presented. Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002  相似文献   
7.
The MPEG-1 Layer 3 compression schema of audio signal, commonly known as mp3, has caused a great impact in recent years as it has reached high compression rates while conserving a high sound quality. Music and speech samples compressed at high bitrates are perceptually indistinguishable from the original samples, but very little was known about how compression acoustically affects the voice signal. A previous work with normal voices showed a high fidelity at high-bitrate compressions both in voice parameters and the amplitude-frequency spectrum. In the present work, dysphonic voices were tested through two studies. In the first study, spectrograms, long-term average spectra (LTAS), and fast Fourier transform (FFT) spectra of compressed and original samples of running speech were compared. In the second study, intensities, formant frequencies, formant bandwidths, and a multidimensional set of voice parameters were tested in a set of sustained phonations. Results showed that compression at high bitrates (96 and 128 kbps) preserved the relevant acoustic properties of the pathological voices. With compressions at lower bitrates, fidelity decreases, introducing some important alterations. Results from both works, Gonzalez and Cervera and this paper, open up the possibility of using MPEG-compression at high bitrates to store or transmit high-quality speech recordings, without altering their acoustic properties.  相似文献   
8.
9.
Summary Studies performed by the Brazilian Nuclear Corporation (NUCLEBRAS), in collaboration with the Geological Survey Company of Brazil (CPRM), identified high levels of natural uranium in the districts of Pedra and Venturosa, in the rural region of the state of Pernambuco (PE) - Brazil, where the maximum value found in rocks was 22,000 mg.  相似文献   
10.
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