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   3522篇
  免费   509篇
  国内免费   369篇
化学   2627篇
晶体学   21篇
力学   175篇
综合类   35篇
数学   308篇
物理学   1234篇
  2024年   7篇
  2023年   83篇
  2022年   92篇
  2021年   85篇
  2020年   133篇
  2019年   135篇
  2018年   105篇
  2017年   101篇
  2016年   149篇
  2015年   143篇
  2014年   189篇
  2013年   259篇
  2012年   339篇
  2011年   357篇
  2010年   234篇
  2009年   198篇
  2008年   252篇
  2007年   215篇
  2006年   190篇
  2005年   150篇
  2004年   113篇
  2003年   87篇
  2002年   86篇
  2001年   82篇
  2000年   57篇
  1999年   63篇
  1998年   60篇
  1997年   59篇
  1996年   66篇
  1995年   74篇
  1994年   39篇
  1993年   25篇
  1992年   35篇
  1991年   30篇
  1990年   18篇
  1989年   16篇
  1988年   15篇
  1987年   7篇
  1986年   8篇
  1985年   11篇
  1984年   5篇
  1983年   3篇
  1982年   6篇
  1981年   7篇
  1979年   4篇
  1971年   1篇
  1968年   1篇
  1940年   1篇
  1902年   1篇
  1898年   1篇
排序方式: 共有4400条查询结果,搜索用时 15 毫秒
931.
932.
Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization has been demonstrated to be a valid method to prepare block copolymer nano‐objects. However, volatile solvents are generally involved in this preparation. Herein, the in situ synthesis of block copolymer nano‐objects of poly(ethylene glycol)‐block‐polystyrene (PEG‐b‐PS) in the ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIN][PF6]) through the macro‐RAFT agent mediated dispersion polymerization is investigated. It is found that the dispersion RAFT polymerization of styrene in the ionic liquid of [BMIN][PF6] runs faster than that in the alcoholic solvent, and the dispersion RAFT polymerization in the ionic liquid affords good control over the molecular weight and the molecular weight distribution of the PEG‐b‐PS diblock copolymer. The morphology of the in situ synthesized PEG‐b‐PS diblock copolymer nano‐objects, e.g., nanospheres and vesicles, in the ionic liquid is dependent on the polymerization degree of the solvophobic block and the concentration of the fed monomer, which is somewhat similar to those in alcoholic solvent. It is anticipated that the dispersion RAFT polymerization in ionic liquid broads a new way to prepare block copolymer nano‐objects. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1517–1525  相似文献   
933.
934.
Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications. Especially, their active center similarity and substrate selectivity promoted their superior biocatalytic activity. Here, modification of critical elements, such as size, morphology, nanocrystal facets, chiral surface and active sites, for controlling the catalytic efficiency of individual chiral nanoparticles (NPs) and chiral nanoassemblies has been demonstrated, which had a synergistic effect on overcoming the defects of pre-existing nanocatalysts. Noticeably, application of external forces (light or magnetism) has resulted in obvious enhancement in biocatalytic efficiency. Chiral nanomaterials served as preferable biomimetic nanocatalysts due to their special structural configuration and chemical constitution advantages. Furthermore, the current challenges and future research directions of the preparation of high-performance bioinspired chiral nanomaterials for biological applications are discussed.

Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications.  相似文献   
935.
With the aim of developing supports for uranyl cations immobilisation, new 1,3-alternate calix[4]arenes bearing both phosphonic acid functions as chelating sites and N-succinimide-4-oxabutyrate as the anchoring arm were synthesised in good yields. The coupling of such calixarenes to a gel was performed and a successful immobilisation of uranyl cations was obtained.  相似文献   
936.
937.
Microhaplotype markers are emerging forensic genetic markers, which may supplement existing markers. Consisting of two to four SNPs with an extent of <200 bp, microhaplotype can be genotyped through massively parallel sequencing technology. Articles that have been published suggested that microhaplotype markers have good application prospect in forensics. Multiallelic haplotype loci are potentially important in certain forensic works, as the stutter and high mutation rate of short tandem repeats and the low polymorphism of single nucleotide polymorphisms may limit the power of these two kind of regular markers. In this study, we explored the potential of 11 new microhaplotype loci in kinship analysis. The results suggested that these loci have relatively high polymorphic information in different populations worldwide and relatively high system effectiveness in the kinship analysis. Microhaplotypes have potential for forensic kinshipg analysis.  相似文献   
938.
A practical convenient conversion of oxindoles into the corresponding spirocyclopropyl oxindoles is achieved efficiently using bromoethylsulfonium salt, which is easily prepared on a large scale and is stable crystalline. This reaction of bromoethylsulfonium salt with different substituted unprotected oxindoles proceeded under mild condition and provided moderate yields.  相似文献   
939.
The application of solar energy is crucial for alleviating the energy crisis and achieving sustainable development. In recent years, photo-assisted rechargeable batteries have attracted researchers because they can directly convert and store solar energy in the batteries. And it also can be used like a normal battery without light illumination. Photo-assisted lithium-based batteries have received more attention than other energy storage systems due to their higher energy density and relatively mature development. This Review focuses on the design of various photo-assisted lithium-based batteries including Li-ion, Li-S, Li-O2, Li-CO2 and Li-I batteries, as well as the working mechanism of photoelectrodes in these battery systems. The basic understanding and challenge of photo-assisted lithium-based batteries are also discussed. At last, perspectives for the photoelectrode development are provided in the summary to advance photo-assisted energy storage systems.  相似文献   
940.
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