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   359102篇
  免费   3747篇
  国内免费   1562篇
化学   172889篇
晶体学   4409篇
力学   18850篇
综合类   62篇
数学   53484篇
物理学   114717篇
  2020年   2362篇
  2019年   2584篇
  2018年   11327篇
  2017年   12114篇
  2016年   8619篇
  2015年   3805篇
  2014年   4908篇
  2013年   11348篇
  2012年   12756篇
  2011年   21920篇
  2010年   14053篇
  2009年   13897篇
  2008年   19338篇
  2007年   22595篇
  2006年   9451篇
  2005年   14280篇
  2004年   10753篇
  2003年   10100篇
  2002年   7744篇
  2001年   7405篇
  2000年   5773篇
  1999年   4239篇
  1998年   3728篇
  1997年   3695篇
  1996年   3588篇
  1995年   3449篇
  1994年   3563篇
  1993年   3213篇
  1992年   3681篇
  1991年   3694篇
  1990年   3641篇
  1989年   3503篇
  1988年   3573篇
  1987年   3496篇
  1986年   3294篇
  1985年   4381篇
  1984年   4686篇
  1983年   3902篇
  1982年   4026篇
  1981年   3946篇
  1980年   3911篇
  1979年   3907篇
  1978年   4241篇
  1977年   4094篇
  1976年   4185篇
  1975年   3846篇
  1974年   3908篇
  1973年   4083篇
  1972年   2854篇
  1971年   2371篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Romanov  V. G. 《Doklady Mathematics》2022,106(1):254-258
Doklady Mathematics - The ray statement of the inverse problem of determining three unknown variable coefficients in the linear acoustic equation is studied. These coefficients are assumed to...  相似文献   
22.
Statistical Inference for Stochastic Processes - The class of autoregressive (AR) processes is extensively used to model temporal dependence in observed time series. Such models are easily...  相似文献   
23.
Journal of Structural Chemistry - N-cyanomethylanabasine is prepared with an yield of 70% by the interaction of the alkaloid anabasine with glyconitrile. It is shown that the highest yield of the...  相似文献   
24.
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   
25.
Crystallography Reports - The review is devoted to the current state of affairs and prospects for development in the field of neutron reflectometry on the existing and future neutron sources in the...  相似文献   
26.
Crystallography Reports - A geometrical and topological analysis has been performed, and self-assembly of the crystal structures of intermetallic compounds CsnMk (М = Na, K, Rb, Pt, Au, Hg,...  相似文献   
27.
Crystallography Reports - The structure of a potassium compound with the chemical formula K0.90Ti5.16Cr2.94Fe2.54Mg0.87Al0.22Mn0.30O19 has been investigated by single-crystal X-ray diffraction...  相似文献   
28.
Journal of Optimization Theory and Applications - We consider a distributionally robust formulation of stochastic optimization problems arising in statistical learning, where robustness is with...  相似文献   
29.
Russian Journal of Applied Chemistry - In September 1975, the head of Russian electrochemists, Academician A.N. Frumkin (1895–1976), in his report at the XI Mendeleev Congress on General and...  相似文献   
30.
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