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   206422篇
  免费   24749篇
  国内免费   16684篇
化学   97842篇
晶体学   1629篇
力学   9674篇
综合类   988篇
数学   17339篇
物理学   53950篇
综合类   66433篇
  2024年   651篇
  2023年   3489篇
  2022年   4992篇
  2021年   6018篇
  2020年   6217篇
  2019年   5581篇
  2018年   5009篇
  2017年   4829篇
  2016年   7218篇
  2015年   7417篇
  2014年   9646篇
  2013年   11939篇
  2012年   14459篇
  2011年   15172篇
  2010年   10535篇
  2009年   10691篇
  2008年   11684篇
  2007年   10977篇
  2006年   9728篇
  2005年   8669篇
  2004年   6583篇
  2003年   5341篇
  2002年   5082篇
  2001年   4654篇
  2000年   4486篇
  1999年   6674篇
  1998年   6079篇
  1997年   6047篇
  1996年   5974篇
  1995年   5030篇
  1994年   4722篇
  1993年   4000篇
  1992年   3518篇
  1991年   3184篇
  1990年   2664篇
  1989年   2288篇
  1988年   1880篇
  1987年   1329篇
  1986年   959篇
  1985年   630篇
  1984年   387篇
  1983年   259篇
  1982年   223篇
  1981年   159篇
  1980年   99篇
  1979年   66篇
  1977年   53篇
  1976年   61篇
  1975年   62篇
  1974年   80篇
排序方式: 共有10000条查询结果,搜索用时 364 毫秒
121.
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   
122.
123.
124.
125.
Transition Metal Chemistry - Two cubane-like complexes, namely [Ni4L4(HOEt)4] (1), [Co4L4(HOEt)4] (2) (H2L?=?(E)-2-((3-hydroxypropylimino)methyl)-6-methoxyphenol), were prepared under...  相似文献   
126.
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium.  相似文献   
127.
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors.  相似文献   
128.
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   
129.
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length L=1,000μm and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (d1), the diameter of inner air holes (d4), the metal film thickness (t), as well as the liquid refractive index (n).  相似文献   
130.
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism.  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