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   11268篇
  免费   1800篇
  国内免费   1185篇
化学   6387篇
晶体学   76篇
力学   511篇
综合类   45篇
数学   1054篇
物理学   3092篇
无线电   3088篇
  2024年   48篇
  2023年   308篇
  2022年   443篇
  2021年   497篇
  2020年   593篇
  2019年   469篇
  2018年   444篇
  2017年   371篇
  2016年   495篇
  2015年   549篇
  2014年   665篇
  2013年   803篇
  2012年   939篇
  2011年   992篇
  2010年   701篇
  2009年   629篇
  2008年   663篇
  2007年   582篇
  2006年   594篇
  2005年   502篇
  2004年   348篇
  2003年   326篇
  2002年   361篇
  2001年   247篇
  2000年   229篇
  1999年   223篇
  1998年   167篇
  1997年   160篇
  1996年   177篇
  1995年   139篇
  1994年   122篇
  1993年   83篇
  1992年   83篇
  1991年   69篇
  1990年   48篇
  1989年   42篇
  1988年   40篇
  1987年   20篇
  1986年   27篇
  1985年   21篇
  1984年   12篇
  1983年   5篇
  1982年   1篇
  1981年   6篇
  1980年   1篇
  1957年   3篇
  1935年   1篇
  1931年   1篇
  1930年   3篇
  1922年   1篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
Mao  Jin-Jin  Tian  Shou-Fu  Zou  Li  Zhang  Tian-Tian  Yan  Xing-Jie 《Nonlinear dynamics》2019,95(4):3005-3017
Nonlinear Dynamics - We consider the simplified (3+1)-dimensional B-type Kadomtsev–Petviashvili equation. We use the binary Bell polynomial theory to construct a bilinear form of the...  相似文献   
92.
Zhang  Yingzhu  Chen  Jiehuan  Lian  Xiaomei  Yang  Weitao  Li  Jun  Tian  Shuoxun  Wu  Gang  Chen  Hongzheng 《中国科学:化学(英文版)》2019,62(7):859-865
Layered two-dimensional(2D)perovskite solar cells(PVSCs)with a chemical formula of C(NH_2)_3(CH_3NH_3)_3Pb_3I_(10)(n=3)have been fabricated through additive engineering,wherein stoichiometrically equivalent guanidinium(GA~+)and methylammonium(MA~+)serve as spacer cations.The crystallinity of the perovskite films is dramatically enhanced with proper amount of methylammonium thiocyanate(MASCN)added into the precursor solution.In addition,we substitute a small amount of MA~+with hydrophobic phenylethylammonium(PEA~+),which can passivate trap states of the perovskite films.As a result,the open circuit voltage increases to 1.1 V and the best power conversion efficiency(PCE)of 10.12%is yielded.Furthermore,superior thermal stability and balanced moisture stability of the PEA-substituted GA-based PVSCs are demonstrated,compared to the popular 3D MAPbI_3and 2D PEA-based PVSCs.They retain approximately 80%of the original PCE after 30 d at 20%relative humidity(RH),and 50%of the original PCE after 3200 min at 85°C without any encapsulation.This work suggests a new route to achieve both heat and humidity stable PVSCs by simply mixing different spacer cations.  相似文献   
93.
International Journal of Theoretical Physics - With the advent of new science and technology, teleconference, which allows multiple participants to communicate directly without being constrained by...  相似文献   
94.
A rapid and sensitive method was developed and validated for the quantitative determination of xanthopurpurin (XPP) in rat plasma using ultra-performance liquid chromatography-electrospray ionization-Orbitrap mass spectrometry. XPP inhibits IgE production and prevents peanut-induced anaphylaxis. The XPP and emodin (internal standard) were determined in negative ion mode with m/z 239.0350 → 211.0400 and 269.0455 → 241.0507, respectively. The separation process was achieved using an ACQUITY UPLC HSS T3 column with acetonitrile and 0.1% formic acid in water (85:15). The linear range was 0.5–100 ng/mL, and the correlation coefficient (r2) was > 0.993. The inter-day and intra-day precision was within an acceptable range of 15%. The extraction recovery and matrix effect were 78.9–87.2% and 94.3–98.5%, respectively. Under different conditions, the XPP was stable in the range of 5.6–10.6%. This method was successfully applied to study the pharmacokinetics of XPP with an oral dose of 10.0 mg/kg and intravenous dose of 2.0 mg/kg in rats. The absolute oral bioavailability of XPP was 4.6%.  相似文献   
95.
Feng  Tian  Guo  Lihong  Wu  Baowei  Chen  YangQuan 《Nonlinear dynamics》2020,102(4):2467-2478
Nonlinear Dynamics - In this paper, a class of switched fractional-order continuous-time systems with order $$0<alpha <1$$ is investigated. First, an interesting property of...  相似文献   
96.
Luo  Kai  Tian  Qiang  Hu  Haiyan 《Nonlinear dynamics》2020,102(3):1463-1483
Nonlinear Dynamics - A multilayer membrane element of absolute nodal coordinate formulation is proposed for dynamic modeling of multilayer dielectric elastomer actuators (DEAs). The coupled...  相似文献   
97.
We report the first example of 2D covalent organic framework nanosheets (Redox-COF1) for the selective reduction and in situ loading of valence-variable, redox-sensitive and long-lived radionuclides (abbreviated as VRL nuclides). Compared with sorbents based on chemical adsorption and physical adsorption, the redox adsorption mechanism of Redox-COF1 can effectively reduce the impact of functional group protonation under the usual high-acidity conditions in chemisorption, and raise the adsorption efficiency from the monotonous capture by pores in physisorption. The adsorption selectivity for UO22+ reaches up to unprecedented ca. 97 % at pH 3, more than for any analogous adsorbing material.  相似文献   
98.
Herein, we report that highly chemoselective and enantioselective reduction of 2-vinyl-substituted pyridines has been achieved for the first time. The reaction, which uses chiral spiro-bicyclic bisboranes as catalysts and HBpin and an acidic amide as reducing reagents, proceeds through a cascade process involving 1,4-hydroboration followed by transfer hydrogenation of a dihydropyridine intermediate. The retained double bond in the reduction products permits their conversion to natural products and other useful heterocyclic compounds by simple transformations.  相似文献   
99.
Research on Chemical Intermediates - The photocatalytic conversion of CO2 to fuels by light is of research interest owing to its relevance to environment and energy concerns. In this work, a hybrid...  相似文献   
100.
Zhao  Jun  Chen  Xiaoyu  Zhou  Yuhan  Tian  Hongjing  Guo  Qingjie  Hu  Xiude 《Research on Chemical Intermediates》2020,46(3):1805-1822
Research on Chemical Intermediates - Nano-TiO2 photocatalysts doped with La–N(La–N–TiO2) were prepared by solgel method. The La–N–TiO2 was loaded on the cellulose/SiO2...  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