全文获取类型
收费全文 | 12131篇 |
免费 | 1721篇 |
国内免费 | 1406篇 |
专业分类
化学 | 8236篇 |
晶体学 | 145篇 |
力学 | 858篇 |
综合类 | 95篇 |
数学 | 1466篇 |
物理学 | 4458篇 |
出版年
2023年 | 174篇 |
2022年 | 185篇 |
2021年 | 277篇 |
2020年 | 410篇 |
2019年 | 364篇 |
2018年 | 318篇 |
2017年 | 300篇 |
2016年 | 472篇 |
2015年 | 443篇 |
2014年 | 570篇 |
2013年 | 819篇 |
2012年 | 908篇 |
2011年 | 996篇 |
2010年 | 663篇 |
2009年 | 728篇 |
2008年 | 768篇 |
2007年 | 737篇 |
2006年 | 697篇 |
2005年 | 642篇 |
2004年 | 505篇 |
2003年 | 395篇 |
2002年 | 328篇 |
2001年 | 314篇 |
2000年 | 276篇 |
1999年 | 311篇 |
1998年 | 322篇 |
1997年 | 258篇 |
1996年 | 266篇 |
1995年 | 229篇 |
1994年 | 246篇 |
1993年 | 167篇 |
1992年 | 152篇 |
1991年 | 133篇 |
1990年 | 141篇 |
1989年 | 89篇 |
1988年 | 83篇 |
1987年 | 89篇 |
1986年 | 89篇 |
1985年 | 76篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 38篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 13篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 125 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.
为明确裂缝间相互作用对各向异性的影响,本文以Hudson模型为例分析了裂缝密度、裂缝倾角对地震波波场、弹性常数和Thomsen系数的影响规律,然后采用“基质-骨架-流体”组合化的方法进行了裂缝储层微观尺度的建模,并与实际测井资料进行了对比。结果表明该模型适用条件为低裂缝密度储层,二阶模型适用的裂缝密度范围比一阶模型大,但在裂缝密度过大时,二阶模型会出现不收敛的现象,模型便不再适用。裂缝储层纵横波速度随裂缝倾角增大而增大,纵波速度对裂缝倾角更为敏感。另外,在与实际测井曲线对比时,在高裂缝密度地层二阶模型的应用效果明显优于一阶模型,说明了在高裂缝密度储层考虑裂缝间的相互作用的必要性。 相似文献
3.
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
4.
5.
6.
Jiaxin Fu Yingxiong Wang Kaizhi Shen Qiang Fu Jie Zhang 《Journal of Polymer Science.Polymer Physics》2019,57(10):598-606
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.
Liu Jun-Wei Shen Shu-Qian Li Ming Li Lei 《International Journal of Theoretical Physics》2021,60(5):1712-1719
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.
Li-Miao Lin Yong-Hang Xu Man Shen Jia-Xin Liang Shuan-Jin Wang Min Xiao Yue-Zhong Meng 《高分子科学》2021,39(3):337-343
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.
Anxun Zheng Chang Shen Prof. Qian Tang Dr. Cheng-Bin Gong Dr. Cheuk-Fai Chow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9643-9649
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