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   42871篇
  免费   7056篇
  国内免费   4862篇
化学   30015篇
晶体学   493篇
力学   2842篇
综合类   423篇
数学   4941篇
物理学   16075篇
  2024年   83篇
  2023年   837篇
  2022年   1043篇
  2021年   1381篇
  2020年   1724篇
  2019年   1622篇
  2018年   1354篇
  2017年   1235篇
  2016年   1967篇
  2015年   1900篇
  2014年   2290篇
  2013年   3020篇
  2012年   3704篇
  2011年   3933篇
  2010年   2616篇
  2009年   2505篇
  2008年   2687篇
  2007年   2480篇
  2006年   2410篇
  2005年   1967篇
  2004年   1666篇
  2003年   1308篇
  2002年   1173篇
  2001年   1007篇
  2000年   943篇
  1999年   1006篇
  1998年   851篇
  1997年   745篇
  1996年   761篇
  1995年   688篇
  1994年   641篇
  1993年   549篇
  1992年   510篇
  1991年   429篇
  1990年   404篇
  1989年   303篇
  1988年   208篇
  1987年   172篇
  1986年   170篇
  1985年   136篇
  1984年   77篇
  1983年   82篇
  1982年   73篇
  1981年   43篇
  1980年   23篇
  1979年   12篇
  1977年   5篇
  1975年   6篇
  1969年   4篇
  1957年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The design and exploration of efficient, stable and environmentally compatible organic emitters for an electrochemiluminescence (ECL) sensor is a promising topic. Herein, a novel environmentally-friendly luminophore, ZnBCBTP@MWCNTs, were fabricated via self-assembly of porphyrin molecules (ZnBCBTP) onto multi-walled carbon nanotubes (MWCNTs). The resulting luminophore ZnBCBTP@MWCNTs displayed not only the highly ECL property and but also the good accelerated electron mobility. Then, a label-free ECL biosensor based ZnBCBTP@MWCNTs was constructed for the ultrasensitive detection of uric acid. Excitingly, this proposed ECL biosensor performed a good linear relationship in the range of 0–300 μM with a low detection limit of 1.4 μM, thus offering another reliable and feasible sensing platform for clinical bioanalysis with good selectivity, stability, and repeatability.  相似文献   
22.
23.
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of...  相似文献   
24.
25.
26.
27.
28.
Zhu  Lina  Zheng  Yangong  Jian  Jiawen 《Ionics》2015,21(10):2919-2926
Ionics - This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solid-state potentiometric sensor on an yttria-stabilized zirconia (YSZ)...  相似文献   
29.
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice.  相似文献   
30.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160.  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