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   91389篇
  免费   2942篇
  国内免费   2391篇
化学   35220篇
晶体学   930篇
力学   7401篇
综合类   163篇
数学   33394篇
物理学   19614篇
  2023年   306篇
  2022年   349篇
  2021年   468篇
  2020年   665篇
  2019年   735篇
  2018年   10851篇
  2017年   10570篇
  2016年   6754篇
  2015年   1601篇
  2014年   1142篇
  2013年   1342篇
  2012年   5023篇
  2011年   11671篇
  2010年   6501篇
  2009年   6852篇
  2008年   7495篇
  2007年   9537篇
  2006年   930篇
  2005年   1957篇
  2004年   2091篇
  2003年   2527篇
  2002年   1685篇
  2001年   860篇
  2000年   668篇
  1999年   481篇
  1998年   384篇
  1997年   312篇
  1996年   334篇
  1995年   243篇
  1994年   158篇
  1993年   165篇
  1992年   136篇
  1991年   151篇
  1990年   125篇
  1989年   99篇
  1988年   93篇
  1987年   78篇
  1986年   83篇
  1985年   69篇
  1984年   60篇
  1983年   44篇
  1982年   43篇
  1981年   40篇
  1980年   47篇
  1979年   46篇
  1914年   45篇
  1913年   40篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
22.
The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO2-based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO2 catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO2(R-MnO2) inner layer is decorated with Fe2O3 nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.  相似文献   
23.
24.
25.
26.
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form.  相似文献   
27.
Naphthalimide‐phthalimide derivatives (NDPDs) have been synthesized and combined with an iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine to produce reactive species (i.e., radicals and cations). These generated reactive species are capable of initiating the cationic polymerization of epoxides and/or the radical polymerization of acrylates upon exposure to very soft polychromatic visible lights or blue lights. Compared with the well‐known camphorquinone based systems used as references, the novel NDPD based combinations employed here demonstrate clearly higher efficiencies for the cationic polymerization of epoxides under air as well as the radical polymerization of acrylates. Remarkably, one of the NDPDs (i.e., NDPD2) based systems is characterized by an outstanding reactivity. The structure/reactivity/efficiency relationships of the investigated NDPDs were studied by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The key parameters for their reactivity are provided. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 665–674  相似文献   
28.
29.
A reversibly cross‐linked epoxy resin with efficient reprocessing and intrinsic self‐healing was prepared from a diamine Diels‐Alder (DA) adduct cross‐linker and a commercial epoxy oligomer. The newly synthesized diamine cross‐linker, comprising a DA adduct of furan and maleimide moieties, can cure epoxy monomer/oligomer with thermal reversibility. The reversible transition between cross‐linked state and linear architecture endows the cured epoxy with rapid recyclability and repeated healability. The reversibly cross‐linked epoxy fundamentally behaves as typical thermosets at ambient conditions yet can be fast reprocessed at elevated temperature like thermoplastics. As a potential reversible adhesive, the epoxy polymer with adhesive strength values about 3 MPa showed full recovery after repeated fracture‐thermal healing processes. The methodology explored in this contribution provides new insights in modification of conventional engineering plastics as functional materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2094–2103  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