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   117341篇
  免费   176篇
  国内免费   78篇
化学   40580篇
晶体学   1827篇
力学   8198篇
综合类   1篇
数学   26665篇
物理学   40324篇
  2022年   98篇
  2021年   101篇
  2020年   79篇
  2019年   107篇
  2018年   9821篇
  2017年   10769篇
  2016年   4619篇
  2015年   1094篇
  2014年   357篇
  2013年   531篇
  2012年   5285篇
  2011年   14370篇
  2010年   8392篇
  2009年   8510篇
  2008年   12224篇
  2007年   16086篇
  2006年   720篇
  2005年   7938篇
  2004年   4171篇
  2003年   4054篇
  2002年   1802篇
  2001年   621篇
  2000年   704篇
  1999年   283篇
  1998年   233篇
  1997年   181篇
  1996年   358篇
  1995年   238篇
  1994年   213篇
  1993年   168篇
  1992年   167篇
  1991年   180篇
  1990年   167篇
  1989年   159篇
  1988年   150篇
  1987年   129篇
  1986年   117篇
  1985年   138篇
  1984年   149篇
  1983年   122篇
  1982年   128篇
  1981年   128篇
  1980年   122篇
  1979年   136篇
  1978年   149篇
  1976年   89篇
  1975年   75篇
  1973年   109篇
  1969年   81篇
  1968年   108篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Atopic dermatitis is characterized by leukocyte migration into the skin dermis and typically driven by excessive chemokine production at the site of inflammation. Conventional topical formulations such as gels, creams, and ointments are insufficient for this treatment because of low penetration of drug molecules into the targeted skin tissues. Herein, using a simple, green, sustainable strategy, we have developed novel primary zein nanoparticles embedded in curcumin (Cur) and coated with silk sericin (ZHSCs) for the topical delivery of Cur to penetrate into the dermis and exercise anti-dermatitis effects on the lesion with minimal side-effects. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that ZHSCs facilitate the penetration of Cur across the epidermis layer of skin to reach deep-seated sites. Notably, ZHSCs = 1:0.25 (zein-to-silk sericin mass ratios of 1:0.25) markedly elevated the skin permeability and cumulative turnover of Cur transferred, which were provided a greater than a 3.8-fold increase relative to free Cur. The special nanoparticles of ZHS = 1:0.25 possessed the deepest localization depth and experience a transition of the particle structure and core-shell separation after penetrating into the dermis of skin. In a cell model of dermatitis induced by tumor necrosis factor α/interferon γ co-stimulation, compared with free Cur, Cur-loaded ZHS nanoparticles down-regulated the generation of inflammatory cytokines and chemokines in keratinocytes through suppression of the nuclear translocation of NF-κBp65 and hence exerted an anti-dermatitis effect. This strategy may provide new avenues and direction for the demanding issues of valid topical delivery systems.  相似文献   
3.
4.
5.
6.
7.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
8.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
9.
10.
Su  X. F.  Zhang  Y. L.  Maximov  A. L.  Zhang  K.  Xin  Q.  Feng  C. Q.  Bai  X. F.  Wu  W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,...  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