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   11808篇
  免费   1713篇
  国内免费   1402篇
化学   7972篇
晶体学   143篇
力学   877篇
综合类   100篇
数学   1429篇
物理学   4402篇
  2023年   174篇
  2022年   181篇
  2021年   274篇
  2020年   394篇
  2019年   348篇
  2018年   315篇
  2017年   300篇
  2016年   457篇
  2015年   434篇
  2014年   571篇
  2013年   814篇
  2012年   893篇
  2011年   974篇
  2010年   657篇
  2009年   716篇
  2008年   755篇
  2007年   728篇
  2006年   683篇
  2005年   629篇
  2004年   493篇
  2003年   384篇
  2002年   324篇
  2001年   312篇
  2000年   274篇
  1999年   309篇
  1998年   316篇
  1997年   255篇
  1996年   257篇
  1995年   224篇
  1994年   240篇
  1993年   159篇
  1992年   149篇
  1991年   131篇
  1990年   140篇
  1989年   85篇
  1988年   78篇
  1987年   86篇
  1986年   82篇
  1985年   71篇
  1984年   48篇
  1983年   33篇
  1982年   35篇
  1981年   26篇
  1980年   20篇
  1979年   15篇
  1978年   14篇
  1977年   8篇
  1976年   8篇
  1973年   10篇
  1970年   7篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Zhang  Jia-Rui  Zhang  Jia-Qi  Zheng  Zhao-Lin  Lin  Da  Shen  Yu-Jia 《Nonlinear dynamics》2022,108(2):1005-1026
Nonlinear Dynamics - Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or...  相似文献   
2.
Han  Xiaoyang  Shen  Han-Wei  Li  Guan  Lu  Xuyi  Shan  Guihua  Wang  Yangang 《显形杂志》2021,24(3):615-629
Journal of Visualization - Convolutional neural networks (CNNs) have achieved breakthrough performance in image recognition and classification. However, it is still a challenge for CNNs to classify...  相似文献   
3.
Publications mathématiques de l'IHÉS - It is well known that a real analytic symplectic diffeomorphism of the $2d$ -dimensional disk ( $d\geq 1$ ) admitting the origin as a...  相似文献   
4.
5.
The first-principles DFT calculations together with microkinetic analysis reveal the complex catalytic mechanism of low-content NO oxidation on CrO2(110) at room temperature. It quantitatively makes clear that CrO2(110) can exhibit considerable activity with the Mars-van-Krevelen mechanism preferred, and the nitrate species serves as the key poisoning species.  相似文献   
6.
Many experimental results have revealed that the re‐entanglement kinetics of disentangled polymers is much slower than that predicted by tube theory. This retarded recovery of fully entangled state is of practical significance that shear‐induced modification may offer a way to improve processability for a polymer by reducing viscosity. This work tried to figure out the shear‐rate dependence variation of viscosity in the view of evolution of entanglement state through disentanglement and re‐entanglement, aiming to provide fundamental insights into application prospect of shear‐induced modification in preparing “in‐pellet” disentangled polymers prior to final processing. High‐density polyethylene was sheared on a parallel‐plate rotational rheometer with a linearly increased shear rate. Results showed that higher shear rate could induce further disentanglement, resulting in a lower viscosity with a reduction rate up to 93.7%, larger molecular weight between entanglements Me , and longer re‐entanglement time. Additionally, less entanglement would give a larger lamellar thickness of sheared samples after nonisothermal crystallization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 598–606  相似文献   
7.
International Journal of Theoretical Physics - Quantum coherence, coming from quantum superposition, occupies a significant position in the field of physics. We put forward a lower bound of the...  相似文献   
8.
A series of semi-aromatic polyesters named as Poly(PO-CHO-PA) were facilely synthesized via ring-opening terpolymerization of biobased cyclohexane oxide(CHO)/propylene oxide(PO)/phthalic anhydride(PA) using economical U1/PPNCl as dual catalyst. The proportion of CHO-PA and PO-PA segments in polymer can be readily altered by changing the feed ratio of CHO/PO because the reactivity ratios of CHO and PO with PA calculated by Fineman-Ross method are comparable. All synthesized amorphous polyesters with various compositions show one Tg ranging from 62 ℃ to 133 ℃. Significantly, the mechanical, thermal and barrier properties of these amorphous semi-aromatic polyesters are also adjustable and investigated for the first time. The results indicate the semi-polyesters exhibit superior thermostability(T5% ranging from 306 ℃ to323 ℃) and high tensile strength(40.21-55.7 MPa) that is comparable with polystyrene(PS). Furthermore, Poly(PO-CHO-PA) films possess a promising prospect as packaging materials because of its colorless and highly transparent nature, along with low oxygen and water vapor transmission rate. All above performances may guarantee its potential alternative to commercial PS.  相似文献   
9.
Shen  Honglong  Yang  Xiaoqiang  Song  Juanjuan  Gao  Haiwen  Wu  Zongdeng  Yu  Jia  Lei  Wu  Yang  Jiazhi  He  Guangyu  Hao  Qingli 《Journal of Solid State Electrochemistry》2022,26(2):353-363
Journal of Solid State Electrochemistry - Long-cycle stability and high-energy density are big challenges for developing high-performance hybrid supercapacitor (HSC) electrode materials. In this...  相似文献   
10.
Herein, a catalytic chemosensing assay (CCA), based on a bimetallic complex, [RuII(bpy)2(CN)2]2(CuII)2 (bpy=2,2′-bipyridine), is described. This complex integrates a task-specific catalyst (CuI-catalyst) and a signaling unit ([RuII(bpy)2(CN)2]) to specifically hydrolyze methyl parathion, a highly toxic organophosphate (OP) pesticide. The bimetallic complex catalyzed the hydrolysis of the phosphate ester to generate o,o-dimethyl thiophosphate (DTP) anion and 4-nitrophenolate. Intrinsically, 4-nitrophenolate absorbed UV/Vis light at λmax=400 nm, creating the first level of the chemosensing signal. DTP interacted with the original complex to displace the chromophore, [RuII(bpy)2(CN)2], which was monitored by spectrofluorometry; this was classified as the second level of chemosensing signal. By integrating both spectroscopic and spectrofluorometric signals with a simple AND logic gate, only methyl parathion was able to provide a positive response. Other aromatic and aliphatic OP pesticides (diazinon, fenthion, meviphos, terbufos, and phosalone) and 4-nitrophenyl acetate provided negative responses. Furthermore, owing to the metal-catalyzed hydrolysis of methyl parathion, the CCA system led to the detoxification of the pesticide. The CCA system also demonstrated its catalytic chemosensing properties in the detection of methyl parathion in real samples, including tap water, river water, and underground water.  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