全文获取类型
收费全文 | 43048篇 |
免费 | 7007篇 |
国内免费 | 4944篇 |
专业分类
化学 | 30313篇 |
晶体学 | 508篇 |
力学 | 2686篇 |
综合类 | 338篇 |
数学 | 4982篇 |
物理学 | 16172篇 |
出版年
2024年 | 32篇 |
2023年 | 837篇 |
2022年 | 904篇 |
2021年 | 1402篇 |
2020年 | 1754篇 |
2019年 | 1580篇 |
2018年 | 1404篇 |
2017年 | 1307篇 |
2016年 | 1955篇 |
2015年 | 1975篇 |
2014年 | 2473篇 |
2013年 | 3154篇 |
2012年 | 3861篇 |
2011年 | 3932篇 |
2010年 | 2764篇 |
2009年 | 2595篇 |
2008年 | 2824篇 |
2007年 | 2549篇 |
2006年 | 2367篇 |
2005年 | 1945篇 |
2004年 | 1616篇 |
2003年 | 1232篇 |
2002年 | 1131篇 |
2001年 | 936篇 |
2000年 | 791篇 |
1999年 | 891篇 |
1998年 | 741篇 |
1997年 | 685篇 |
1996年 | 749篇 |
1995年 | 642篇 |
1994年 | 578篇 |
1993年 | 505篇 |
1992年 | 463篇 |
1991年 | 383篇 |
1990年 | 343篇 |
1989年 | 247篇 |
1988年 | 225篇 |
1987年 | 209篇 |
1986年 | 145篇 |
1985年 | 165篇 |
1984年 | 137篇 |
1983年 | 119篇 |
1982年 | 82篇 |
1981年 | 59篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 26篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
Tyrosine nitration of human ERK1 introduces an intra-hydrogen bond by molecular dynamics simulations
Xu Wu Zhang Yuanya Achi Oliver Y. Knierim Kathleen D. Hanks Justin G. Wang Yingchun 《Structural chemistry》2019,30(4):1459-1470
Structural Chemistry - ERK1 is an important kinase in Ras–Raf–MEK signaling. We have recently demonstrated by mass spectrometry that Tyr210 of ERK1 can be nitrated, and the nitration... 相似文献
42.
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
43.
Yong-Li Li Qiang Zhang Jian-Jun Wu Li-Jun Xue Li-Ming Chen Jun-Mian Tian Zhuo-Ni Xu Ying Chen Xian-Wen Yang Xiao-Jiang Hao Jie Li 《Tetrahedron letters》2019,60(10):751-753
From Abies nukiangensis, two novel 13,14-seco-abietane diterpenes, nukiangendines A (1) and B (2) were isolated. Their relative structures were determined by extensive NMR and HRMS spectroscopic analysis. The absolute configuration of 1 was established by ECD calculations. Compound 1 showed significant anti-hepatitis C virus (HCV) effects. 相似文献
44.
Guojiao Wu Jennifer Brger Axel Jacobi von Wangelin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17401-17405
Atom‐transfer radical addition (ATRA) reactions have gained a strong foothold in organic synthesis by virtue of their operational simplicity, synthetic versatility, and perfect atom economy. A rich chemical space can be accessed through clever combinations of the simple starting materials. Many variations of this general motif have been reported. However, the vast majority involve the addition of an organic halide across a C=C double bond, resulting in the formation of 1,2‐bifunctional products. This report introduces a significant expansion of this general reactivity concept to give 1,3‐bifunctional adducts through the combination of 1,1‐ATRA to a carbenoid and 1,2‐ATRA to an alkyne. Both processes operate under mild conditions (RT, 5 h) with the same commercial catalyst (CoBr2, dppbz). 相似文献
45.
Nonlinear Dynamics - In this paper, the Riemann–Hilbert approach is systematically established for the Newell-type long-wave–short-wave equation. Firstly, we start spectral analysis... 相似文献
46.
Han Jing Sun Youhong Guo Wei Deng Sunhua Hou Chuanbin Qu Lili Li Qiang 《Journal of Thermal Analysis and Calorimetry》2019,135(4):2287-2296
Journal of Thermal Analysis and Calorimetry - In this study, the non-isothermal pyrolysis method was used to investigate the pyrolysis characteristics of oil shale from four areas: namely Nongan,... 相似文献
47.
Laihao Ding Guan-Huei Duh Guanghui Wang Tsai-Lien Wong Jianliang Wu Xiaowei Yu Xuding Zhu 《Discrete Mathematics》2019,342(1):279-284
A graph is -choosable if the following holds: For any list assignment which assigns to each vertex a set of real numbers, and assigns to each edge a set of real numbers, there is a total weighting such that for , and for every edge . This paper proves that if is a connected graph of maximum degree , then is -choosable. 相似文献
48.
49.
Tenghao Yin Lei Wu Tonghao Wu Guoyong Mao Guodong Nian Zhe Chen Xiaocheng Hu Peng Wang Yuhai Xiang Honghui Yu Shaoxing Qu Wei Yang 《Journal of Polymer Science.Polymer Physics》2019,57(5):272-280
Conductive hydrogels with ionic compounds possess great potential for the development of soft smart devices. A dielectric scarfskin is typically required for these devices to prevent short circuiting, leading to devices with lower stretchability than the hydrogel. Henceforth, commonly used dielectric materials, such as PDMS and Ecoflex, cannot be largely stretched. Hydrogel devices with ultrastretchability are required to accommodate hostile application environments. Herein, we propose a hydrogel fiber coated with a dielectric layer that can be stretched to over 2000% of its initial length. The fiber remains conductive when stretched to ~1300%. In addition, the core/sheath hydrogel fiber can be endowed with a variety of functional properties, such as electroluminescence (EL), photoluminescence (PL), and magnetic‐responsiveness, demonstrating scalability of the resultant fiber. The present work can pave the way for numerous next‐generation soft devices, such as smart textiles and wearable electronics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 272–280 相似文献
50.
构建了由一个占主导地位的电商平台和一个处于跟随地位的制造商组成的Stackelberg主从博弈模型,研究了电商平台有无利他偏好时电商供应链的最优决策和契约协调问题,并通过数值算例验证了本文的主要结论.研究表明:电商平台的利他偏好行为能够促使自身服务水平提高、正向影响制造商的最优销售价格并削弱自身利润.但电商平台的让利行为能够提高制造商的利润水平、缓和供应链冲突并改善供应链整体绩效."销售佣金比例+服务成本共担"契约能够完美的协调电商供应链,使双方最优利润获得帕累托改进,从而保证电商平台有足够的激励执行利他偏好行为.另外,进一步分析发现电商平台的利他偏好正向影响制造商支付给电商平台的固定技术服务费、制造商占有的电商供应链利润份额和服务成本分担比例,负向影响自身的销售佣金比例. 相似文献