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   74238篇
  免费   8235篇
  国内免费   5984篇
化学   42638篇
晶体学   901篇
力学   4341篇
综合类   389篇
数学   14539篇
物理学   25649篇
  2024年   98篇
  2023年   892篇
  2022年   1051篇
  2021年   1468篇
  2020年   1795篇
  2019年   1762篇
  2018年   2701篇
  2017年   2833篇
  2016年   2857篇
  2015年   2739篇
  2014年   3060篇
  2013年   3918篇
  2012年   7067篇
  2011年   6459篇
  2010年   4754篇
  2009年   4416篇
  2008年   3657篇
  2007年   3342篇
  2006年   3190篇
  2005年   6457篇
  2004年   5568篇
  2003年   3726篇
  2002年   1978篇
  2001年   1519篇
  2000年   1207篇
  1999年   1203篇
  1998年   1015篇
  1997年   870篇
  1996年   842篇
  1995年   757篇
  1994年   660篇
  1993年   509篇
  1992年   643篇
  1991年   525篇
  1990年   468篇
  1989年   368篇
  1988年   322篇
  1987年   242篇
  1986年   204篇
  1985年   196篇
  1984年   143篇
  1983年   104篇
  1982年   82篇
  1981年   64篇
  1979年   45篇
  1976年   82篇
  1975年   39篇
  1974年   45篇
  1973年   50篇
  1972年   40篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Research on Chemical Intermediates - Owing to the simultaneous utilization of photogenerated electrons and holes, coupling light-driven hydrogen (H2) evolution reaction (HER) and biomass-derived...  相似文献   
2.
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly.  相似文献   
3.
Xu  Feixiang  Luo  Jiangchen  Jiang  Liqun  Zhao  Zengli 《Cellulose (London, England)》2022,29(3):1463-1472
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis...  相似文献   
4.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results.  相似文献   
5.
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs.  相似文献   
6.
Wang  Rong  Li  Xu  Zhou  Youshi  Cao  Shuxuan  Xu  Honghao  Han  Wenjuan  Zhang  Yuxia  Liu  Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The...  相似文献   
7.
8.
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution...  相似文献   
9.
International Journal of Theoretical Physics - This paper mainly studied the observer design of Lipschitz stochastic discrete system. For the first time, generalized Lipschitz conditions are...  相似文献   
10.
Wang  Xuebin  Xu  Can  Zheng  Zhigang 《Nonlinear dynamics》2021,103(3):2721-2732
Nonlinear Dynamics - The classical Kuramoto model serves as a useful tool for studying synchronization transitions in coupled oscillators that is limited to the sinusoidal and pairwise...  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