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   77473篇
  免费   12311篇
  国内免费   6970篇
化学   52315篇
晶体学   752篇
力学   4998篇
综合类   311篇
数学   8356篇
物理学   30022篇
  2024年   797篇
  2023年   1804篇
  2022年   2947篇
  2021年   3409篇
  2020年   3796篇
  2019年   3507篇
  2018年   2572篇
  2017年   2346篇
  2016年   3660篇
  2015年   3481篇
  2014年   4159篇
  2013年   5311篇
  2012年   6732篇
  2011年   6726篇
  2010年   4471篇
  2009年   4253篇
  2008年   4596篇
  2007年   4111篇
  2006年   3757篇
  2005年   3139篇
  2004年   2460篇
  2003年   1924篇
  2002年   1752篇
  2001年   1472篇
  2000年   1355篇
  1999年   1535篇
  1998年   1312篇
  1997年   1296篇
  1996年   1292篇
  1995年   1052篇
  1994年   923篇
  1993年   765篇
  1992年   677篇
  1991年   580篇
  1990年   507篇
  1989年   389篇
  1988年   344篇
  1987年   286篇
  1986年   258篇
  1985年   211篇
  1984年   154篇
  1983年   108篇
  1982年   89篇
  1981年   75篇
  1980年   70篇
  1979年   34篇
  1978年   30篇
  1977年   40篇
  1976年   31篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
The spin polarization of carbon nanomaterials is crucial to design spintronic devices. In this paper, the first-principles is used to study the electronic properties of two defect asymmetric structures, Cap-(9, 0)-Def [6, 6] and Cap-(9, 0)-Def [5, 6]. We found that the ground state of Cap-(9, 0)-Def [6, 6] is sextet and the ground state of Cap-(9, 0)-Def [5, 6] is quartet, and the former has a lower energy. In addition, compared with Cap-(9, 0) CNTs, the C adatom on C30 causes spin polarization phenomenon and Cap-(9, 0)-Def [6, 6] has more spin electrons than Cap-(9, 0)-Def [5, 6] structure. Moreover, different adsorb defects reveal different electron accumulation. This finding shows that spin polarization of the asymmetric structure can be adjusted by introducing adatom defects.  相似文献   
42.
Constructing molecular switches based on supramolecular assembly strategy is a research hotspot. In this work, we constructed an all visible-light-regulated supramolecular photo-switch based on pyridinium-modified diarylethene derivative (DTE-Me) and cucurbit[8]uril (CB[8]). CB[8] not only accelerated the photochromic process under 365 nm ultraviolet light but also shifted the absorption of open formed DTE-Me to the visible region, which led to efficient photocyclization under 450 nm visible light irradiation, while DTE-Me and DTE-Me/CB[7] remained unchanged under the same irradiating condition. Moreover, the complexation with CB[8] could induce the strong thermally activated delayed fluorescence (TADF) of guest molecular at 550 nm, which further shifted to 670 nm through two-step sequential energy transfer with sulforhodamine B (SRB) and Cy5. This energy transfer process could also be regulated with visible light, and the application for information encryption was also demonstrated. This assembly provides a convenient approach to construct all visible light-regulated TADF photo-switch.  相似文献   
43.
Zhang  Wen  Liu  Yang  Song  Dengpeng  Guo  Heng  Hu  Jinbang  Wang  Yunli  Xu  Weilin 《Cellulose (London, England)》2021,28(9):5911-5922
Cellulose - Traditional cotton fiber dyeing requires an abundance of salt, which leads to environmental pollution. Consequently, decreasing or eliminating the use of salt has become the primary...  相似文献   
44.
Silk has been widely used in the clothing industry due to their soft and smooth features, good biocompatibility, good heat dissipation, warmth and ultraviolet resistance. The application of fragrance to silk can significantly improve the performance of silk. However, there are two key scientific problems that need to be solved: slowing down the release rate of fragrances and increasing the scent lasting time of silk. In this study, cationic and temperature-sensitive liposomes were designed and prepared to encapsulate eugenol. These fragrance-loaded liposomes significantly slowed down the release rate of the fragrance and controlled the release rate of the fragrance in a thermo-sensitive manner. The liposomes adhered to the silk through electrostatic adsorption interaction. The positive charge on the fragrance-loaded liposomes neutralized much negative charge on silk and thereby increasing the adhesion efficiency.  相似文献   
45.
Wang  Deqiang  Li  Zuoji  Zhao  Qian  Zhang  Jianguo  Yang  Guang  Liu  Hui 《Journal of Cluster Science》2021,32(5):1175-1183

Developing artificial enzyme mimetics for the detection of small biomolecules are a current research interest because natural enzymes bear some serious disadvantages, such as their catalytic activity can be easily inhibited and they can be digested by proteases. Herein, a heteropoly acids (HPA) encapsulating metal–organic framework (MOF) with metal-carbene structure, [Cu10(H3trz)4(Htrz)4][PMo12VO41] (PMA-MOF) as bifunctional enzyme-mimetic catalyst for colorimetric detection of hydrogen peroxide (H2O2) and ascorbic acid (AA) was designed and synthesized. Thanks to the good stability and the synergistic effect of PMA and MOF, PMA-MOF exhibits the lower limit of detection (0.222 μM towards H2O2 and 0.0046 μM to AA), and the smaller Km value (0.0138 mM for H2O2 and 0.136 mM for o-phenylenediamine) compared to most reported MOF- and HPA-based enzyme-mimetic catalyst, to the best our knowledge.

  相似文献   
46.
Qin  Shun-Shun  Liu  Jing-Long  Hu  Feng  Jia  Ai-Quan  Xu  Chao  Zhang  Qian-Feng 《Journal of Cluster Science》2021,32(6):1593-1599
Journal of Cluster Science - Interaction of [Pb(SiPr)2]n with 1.5 equiv. of AgNO3 in DMF under aerobic conditions at room temperature gave a cationic lead-centered thiolate cluster...  相似文献   
47.
Journal of Thermal Analysis and Calorimetry - Applying foamed warm-mix asphalt in pavement has attracted great attention, but its effects on asphalt mastic are not clear. This research investigated...  相似文献   
48.
Su  Ying  Li  Weili  Liu  Wenmao  Li  Yong  Li  Dong 《Journal of Thermal Analysis and Calorimetry》2021,146(5):2279-2289
Journal of Thermal Analysis and Calorimetry - The stator ventilation duct is the main path for fluid flowing to cool the stator bar and the core. Considering the complexity of the ventilation...  相似文献   
49.
A new organic hybrid holmium–germanate oxo-cluster [Ho8(phen)2Ge12(μ 3-O)24(CH2CH2COO)12(H2O)16]·2H2O (1, phen = 1,10-phenanthroline) was prepared under mild hydrothermal conditions and structurally characterized by elemental analysis, UV/Vis, IR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Compounds 1 contains cage clusters [Ho8(phen)2Ge12(μ 3-O)24(CH2CH2COO)12(H2O)16] and free H2O molecules. The cage cluster is constructed by the combination of two [Ho(phen)(H2O)2] units, two [Ge6O12(CH2CH2COO)6] rings and one circular [Ho6O36] fragment via sharing O atoms. 1 is the rare example of organic hybrid holmium–germanate oxo-cluster decorated by phen ligands.  相似文献   
50.
Novel diacetylene macrocycles 1 and 2 bearing dibenzylphosphine oxide were synthesised via Eglinton acetylenic intramolecular coupling. The X-ray analysis of crystals of macrocycles 1 and 2 demonstrated that the better-aligned tubular supramolecular structure was formed in macrocycle 1 than in macrocycle 2, which provided the possibility of diacetylene topochemical polymerisation in solid state of macrocycle 1. UV–vis, Raman spectroscopy and X-ray analysis indicated that the crystals of macrocycle 1 could undergo topochemical diacetylene polymerisation only on their surface by light irradiation; differential scanning calorimetry, solid-state 13C NMR spectroscopy and solubility test demonstrated that the crystals of macrocycle 1 could undergo diacetylene topochemical polymerisation inside solid by heat. As expected, based on the topological analysis of crystal structure, the crystals of macrocycle 2 could not undergo diacetylene topochemical polymerisation either by light irradiation or heat.  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