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   176812篇
  免费   2823篇
  国内免费   676篇
化学   96434篇
晶体学   1991篇
力学   7682篇
综合类   5篇
数学   18996篇
物理学   55203篇
  2021年   941篇
  2020年   1284篇
  2019年   1307篇
  2018年   1263篇
  2017年   1273篇
  2016年   2704篇
  2015年   2272篇
  2014年   2892篇
  2013年   8468篇
  2012年   7105篇
  2011年   8663篇
  2010年   5333篇
  2009年   5267篇
  2008年   7883篇
  2007年   7790篇
  2006年   7595篇
  2005年   7060篇
  2004年   6270篇
  2003年   5373篇
  2002年   4877篇
  2001年   5924篇
  2000年   4354篇
  1999年   3221篇
  1998年   2374篇
  1997年   2428篇
  1996年   2386篇
  1995年   2261篇
  1994年   2159篇
  1993年   2032篇
  1992年   2339篇
  1991年   2296篇
  1990年   2009篇
  1989年   1978篇
  1988年   2022篇
  1987年   1950篇
  1986年   1882篇
  1985年   2828篇
  1984年   2786篇
  1983年   2207篇
  1982年   2410篇
  1981年   2299篇
  1980年   2258篇
  1979年   2199篇
  1978年   2277篇
  1977年   2224篇
  1976年   2165篇
  1975年   2132篇
  1974年   2043篇
  1973年   2119篇
  1972年   1197篇
排序方式: 共有10000条查询结果,搜索用时 228 毫秒
1.
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   
2.
Journal of Analytical Chemistry - The review considers the historical aspects of the formation and development of bioelectrochemistry and some issues of the analytical application of...  相似文献   
3.
4.

A model with 16 moments is here presented in the framework of RET of polyatomic gases. It furnishes as principal subsystem the relativistic counterpart of a work by Arima T., Ruggeri T., Sugiyama M.; this is present in literature and treats the non relativistic case which incorporates relaxation processes of molecular rotation and vibration. Another principal subsystem is the natural extension of the 14 moments model by Pennisi S. and Ruggeri T.; this is also present in literature in the relativistic framework but where the trace of the third balance equation is neglected. Its extension is found here for the case when this trace isn’t neglected.

  相似文献   
5.
6.
7.
Experimental Techniques - In the last years, the wind industry has increased in a large scale. A wind turbine out of service leeds to high costs due to both maintenance and repair costs and the...  相似文献   
8.
Journal of Solid State Electrochemistry - Highly efficient, abundant, and low-cost materials are highly demanded for energy conversion applications to address the rising consumption of energy. In...  相似文献   
9.
We consider kinetic models for a multi component gas mixture without chemical reactions. In the literature, one can find two types of BGK models in order to describe gas mixtures. One type has a sum of BGK type interaction terms in the relaxation operator, for example the model described by Klingenberg, Pirner and Puppo [20] which contains well-known models of physicists and engineers for example Hamel [16] and Gross and Krook [15] as special cases. The other type contains only one collision term on the right-hand side, for example the well-known model of Andries, Aoki and Perthame [1]. For each of these two models [20] and [1], we prove existence, uniqueness and positivity of solutions in the first part of the paper. In the second part, we use the first model [20] in order to determine an unknown function in the energy exchange of the macroscopic equations for gas mixtures described by Dellacherie [11].  相似文献   
10.
A CE instrument that can be assembled from commercially available components with minimal construction effort is described. Except for the electronic control circuitry no specially made parts are required. It is based on a flexible design of microfluidic, electropneumatic, and electronic sections and different configurations can easily be implemented. Automated injection into the capillary is performed hydrodynamically by the application of a pressure for a controlled length of time. The performance of the device was tested with a contactless conductivity detector by separating different metal ions. In addition, nine metal cations related to the quality of honey were separated in 2.3 min and four honey samples were analysed quantitatively to demonstrate the applicability of the method.  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