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   3773篇
  免费   167篇
  国内免费   16篇
化学   2569篇
晶体学   34篇
力学   93篇
数学   331篇
物理学   929篇
  2023年   16篇
  2022年   13篇
  2021年   67篇
  2020年   79篇
  2019年   69篇
  2018年   59篇
  2017年   45篇
  2016年   119篇
  2015年   114篇
  2014年   141篇
  2013年   228篇
  2012年   317篇
  2011年   348篇
  2010年   180篇
  2009年   171篇
  2008年   264篇
  2007年   242篇
  2006年   220篇
  2005年   213篇
  2004年   161篇
  2003年   147篇
  2002年   110篇
  2001年   79篇
  2000年   69篇
  1999年   56篇
  1998年   36篇
  1997年   22篇
  1996年   44篇
  1995年   41篇
  1994年   45篇
  1993年   42篇
  1992年   29篇
  1991年   19篇
  1990年   28篇
  1989年   18篇
  1988年   6篇
  1987年   9篇
  1986年   11篇
  1985年   12篇
  1984年   5篇
  1983年   6篇
  1982年   8篇
  1980年   7篇
  1979年   5篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1975年   4篇
  1974年   7篇
  1973年   4篇
排序方式: 共有3956条查询结果,搜索用时 109 毫秒
1.
2.
International Journal of Theoretical Physics - In this study, the momentum-kick model is used to understand the ridge behaviour in dihadron Δη–Δφ correlations recently...  相似文献   
3.
Oxygen vacancies (OV) are native defects in transition metal (TM) oxides and their presence has a critical effect on the physicochemical properties of the oxide. Metal oxides are commonly used in lithium‐ion battery (LIB) cathodes and there is still a lack of understanding of the role of OVs in LIB research field. Here, we report on the behavior of OVs in a single‐crystal LIB cathode during the non‐equilibrium states of charge and discharge. We found that microcrack evolution in a single crystal occurs due to OV condensation in specific crystallographic orientations generated by the continuous migration of OVs and TM ions. Moreover, understanding the effects of the presence and diffusion of OVs in metal oxides enables the elucidation of most of the conventional mechanisms of capacity fading in LIBs and provides new insights for new electrochemical applications.  相似文献   
4.
Nonlinear Dynamics - This paper develops new continuous sliding mode controllers for multi-input multi-output mechanical systems in the presence of unknown, but bounded uncertainties in the given...  相似文献   
5.
Diketopyrrolopyrrole (DPP)‐based terpolymers—P(DPP‐TPyT) and P(DPP‐T3MTT)—bearing bithiophene donating groups and weak accepting units such as pyridine (Py) or methyl thiophene‐3‐carboxylate (3MT), in the polymer backbone, were successfully synthesized. Although the two polymers had similar physical and electrochemical properties, grazing incidence X‐ray diffraction patterns of P(DPP‐TPyT) and P(DPP‐T3MTT) showed mixed and edge‐on orientations, respectively, in thermally annealed films. Accordingly, the P(DPP‐T3MTT) showed twice the hole mobility of P(DPP‐TPyT) in a thin‐film transistor, and a blended film of P(DPP‐T3MTT) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) showed better power conversion efficiency in a polymer solar cell. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1339‐1347  相似文献   
6.
7.
In this work, the reaction scheme for the esterification of palm fatty acid distillate performed under the noncatalytic and high‐temperature condition (230–290°C) was investigated with a rigorous mathematical modeling. The esterification reaction was assumed to be the pseudo–homogeneous second‐order reversible reaction, and the mass transfer effectiveness factor (η) was introduced in the modeling framework to systematically and collectively consider both evaporation and reaction, which are simultaneously and competitively occurred in the liquid phase. The nonlinear programming problem was constructed with the objective function consisting of the errors between experimental data and the estimated values from the reaction model. The problem was solved by using the Nelder–Mead simplex algorithm to identify kinetic parameters, reaction rate constants, and mass transfer coefficients. The values of mass transfer coefficients were found to follow the Hertz–Knudsen relation and expressed as a function of reaction temperature. From the reaction rate constants obtained from the proposed kinetic models, the apparent activation energy was estimated to be 43.98 kJ/mol, which is lower than the value obtained from the reaction using heterogeneous catalysts. This low value indicates that reactants and products behave as an acid catalyst at relatively high operating temperature and constant pressure.  相似文献   
8.
New isoindigo and di(thienyl)ethylene‐containing π‐extended conjugated polymers with different branched side chains were synthesized to investigate their physical properties and device performance in thin‐film transistors and photovoltaic cells. 11‐Butyltricosane (S3) and 11‐heptyltricosane (S6) groups were used as side‐chain moieties tethered to isoindigo units. The linking groups between the polymer backbone and bifurcation point in the branched side chain differ in the two polymers (i.e., PIDTE‐S3 and PIDTE‐S6 ). The polymers bearing S6 side chains showed much better charge transport behavior than those with S3 side chains. Thermally annealed PIDTE‐S6 film exhibited an outstanding hole mobility of 4.07 cm2 V?1 s?1 under ambient conditions. Furthermore, bulk heterojunction organic photovoltaic cells made from a blend film of PIDTE‐S3 and (6,6)‐phenyl C61‐butyric acid methyl ester demonstrated promising device performance with a power conversion efficiency in the range of 4.9–5.0%. © 2015 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 2015 , 53, 1226–1234  相似文献   
9.
Herein we report 22 acedan‐derived, two‐photon fluorophores with synthetic feasibility and full coverage of visible wavelength emission. The emission wavelengths were predicted by computational analysis, which enabled us to visualize multicolor images by two‐photon excitation with single wavelength, and to design a turn‐on, two‐photon fluorescence sensor for endogenous H2O2 in Raw 264.7 macrophage and rat brain hippocampus ex vivo.  相似文献   
10.
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