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   4544篇
  免费   544篇
  国内免费   490篇
化学   2298篇
晶体学   30篇
力学   226篇
综合类   45篇
数学   311篇
物理学   1156篇
综合类   1512篇
  2024年   15篇
  2023年   67篇
  2022年   133篇
  2021年   146篇
  2020年   150篇
  2019年   117篇
  2018年   124篇
  2017年   148篇
  2016年   166篇
  2015年   152篇
  2014年   233篇
  2013年   265篇
  2012年   264篇
  2011年   347篇
  2010年   252篇
  2009年   257篇
  2008年   294篇
  2007年   255篇
  2006年   213篇
  2005年   175篇
  2004年   145篇
  2003年   101篇
  2002年   112篇
  2001年   107篇
  2000年   92篇
  1999年   136篇
  1998年   112篇
  1997年   121篇
  1996年   119篇
  1995年   111篇
  1994年   91篇
  1993年   87篇
  1992年   83篇
  1991年   67篇
  1990年   67篇
  1989年   58篇
  1988年   44篇
  1987年   41篇
  1986年   29篇
  1985年   17篇
  1984年   9篇
  1983年   11篇
  1982年   12篇
  1981年   5篇
  1980年   7篇
  1979年   5篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1957年   4篇
排序方式: 共有5578条查询结果,搜索用时 15 毫秒
71.
采用机械力固相法以FeCl3和Fe(NO3)3分别作为铁源.在铁源与碱1∶5摩尔比的条件下,先球磨3h,再经过60℃水浴陈化得到纳米针铁矿(α-FeOOH).用X-射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、比表面和孔隙度分析仪(BET)、紫外-可见分光光度计以及电化学工作站对其物相、微观形貌、比表面、光催化和光电化学性能进行表征.结果 表明:不同铁源的阴离子会诱导合成形貌和性能差异的纳米针铁矿,以FeCl3为原料合成的纳米α-FeOOH粒径较小、比表面积及孔容较大、对有机染料罗丹明B的降解率较以Fe(NO3)3为原料的α-FeOOH提高了48.7;.  相似文献   
72.
This work focused on effects of an eco-friendly carrier JYK on thermal properties,dye uptake,color yield(K/S values)and color fastness of recycled polyester kni...  相似文献   
73.
In comparison with the numerous studies that have centered on developing molecular frameworks for the functionalization of fluorescent materials, less research has addressed the influence of the side chains, despite such appendages contributing significantly to the properties and applications of fluorescent materials. In this work, a new series of cationic fluorescent probes with AIE characteristics have been developed, which exhibit unique sensitivity for charge-diffusion anions, namely HSO3, via the interactions of ions and the cooperation of the controllable hydrophobicity. The impact of the alkyl chain length attached at the cationic probes suggested that the fluorescent intensity and sensitivity of the probes could be partially enhanced by adjusting their aggregation tendency through the action of the hydrophobic effect under aqueous conditions. DLS and SEM images indicated that different particle sizes and new morphologies of the probes were formed in the anion-recognition-triggered self-assembly process, which could be attributed to the composite effect of electrostatic actions, Van der Waals forces and π-π stacking.  相似文献   
74.
An electrically neutral cobalt complex, [Co(GA)2(phen)] (GA=glycollic acid, phen=1,10‐phenathroline), was synthesized and its interactions with double‐stranded DNA (dsDNA) were studied by using electrochemical methods on a glassy carbon electrode (GCE). We found that [Co(GA)2(phen)] could intercalate into the DNA duplex through the planar phen ligand with a high binding constant of 6.2(±0.2)×105 M ?1. Surface studies showed that the cobalt complex could electrochemically accumulate within the modified dsDNA layer, rather than within the single‐stranded DNA (ssDNA) layer. Based on this feature, the complex was applied as a redox‐active hybridization indicator to detect 18‐base oligonucleotides from the CaMV35S promoter gene. This biosensor presented a very low background signal during hybridization detection and could realize the detection over a wide kinetic range from 1.0×10?14 M to 1.0×10?8 M , with a low detection limit of 2.0 fM towards the target sequences. The hybridization selectivity experiments further revealed that the complementary sequence, the one‐base‐mismatched sequence, and the non‐complementary sequence could be well‐distinguished by the cobalt‐complex‐based biosensor.  相似文献   
75.
一种新二肟的合成及其电化学行为   总被引:1,自引:0,他引:1  
修饰电极;一种新二肟的合成及其电化学行为  相似文献   
76.
The schlieren interferograms used to be analyzed in a qualitative way. In this paper, by means of the powerful computational ability and the large memory of computer; the image processing method is investigated for the digitalization of an axisymmetric schlieren interferogram and the determination of the density field. This method includes the 2-D low-pass filtering, the thinning of interferometric fringes, the extraction of physical information and the numerical integration of the density field. The image processing results show that the accuracy of the quantitative analysis of the schlieren interferogram can be improved and a lot of time can be saved in dealing with optical experimental results. Therefore, the algorithm used here is useful and efficient.  相似文献   
77.
78.
All-solid-state sodium batteries with poly(ethylene oxide) (PEO)-based electrolytes have shown great promise for large-scale energy storage applications. However, the reported PEO-based electrolytes still suffer from a low Na+ transference number and poor ionic conductivity, which mainly result from the simultaneous migration of Na+ and anions, the high crystallinity of PEO, and the low concentration of free Na+. Here, we report a high-performance PEO-based all-solid-state electrolyte for sodium batteries by introducing Na3SbS4 to interact with the TFSI anion in the salt and decrease the crystallinity of PEO. The optimal PEO/NaTFSI/Na3SbS4 electrolyte exhibits a remarkably enhanced Na+ transference number (0.49) and a high ionic conductivity of 1.33 × 10−4 S cm−1 at 45 °C. Moreover, we found that the electrolyte can largely alleviate Na+ depletion near the electrode surface in symmetric cells and, thus, contributes to stable and dendrite-free Na plating/stripping for 500 h. Furthermore, all-solid-state Na batteries with a 3,4,9,10-perylenetetracarboxylic dianhydride cathode exhibit a high capacity retention of 84% after 200 cycles and superior rate performance (up to 10C). Our work develops an effective way to realize a high-performance all-solid-state electrolyte for sodium batteries.

A high-performance all-solid-state PEO/NaTFSI/Na3SbS4 electrolyte for sodium batteries is realized owing to the electrostatic interaction between TFSI in the salt and Na3SbS4, which immobilizes TFSI anions and promotes the dissociation of NaTFSI.  相似文献   
79.
Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular-dependent emission spectra of europium ions on top of different films. The results show the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces. The results of numerical calculations agree well with experimental data.  相似文献   
80.
Colon cancer (CC) is one of the most common intestinal malignancies and is difficult to detect in its early stage by magnetic resonance imaging (MRI) with currently used contrast agents (CAs). The development of targeted CAs contributes to the early diagnosis of CC and thereby enables early intervention and timely therapy. Considering the outstanding performance of upconversion nanoprobes (UCNPs) in high‐performance MR and fluorescence imaging, a new type of nanoprobes with considerably enhanced imaging performance is developed herein. Carcinoembryonic antigen (CEA) antibody is conjugated onto the surface of UCNPs to achieve the targeted imaging of early CC tumors, which overexpress CEA. Both toxicity tests and histological/hematological examinations demonstrate the excellent biocompatibility of these CC‐targeting nanoprobes, which possess great potential for clinical application in the early diagnosis of CC.  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