全文获取类型
收费全文 | 71913篇 |
免费 | 11493篇 |
国内免费 | 10132篇 |
专业分类
化学 | 50815篇 |
晶体学 | 1018篇 |
力学 | 4472篇 |
综合类 | 676篇 |
数学 | 8566篇 |
物理学 | 27991篇 |
出版年
2024年 | 62篇 |
2023年 | 1231篇 |
2022年 | 1482篇 |
2021年 | 2052篇 |
2020年 | 2642篇 |
2019年 | 2545篇 |
2018年 | 2179篇 |
2017年 | 2131篇 |
2016年 | 3125篇 |
2015年 | 3154篇 |
2014年 | 3832篇 |
2013年 | 4975篇 |
2012年 | 5959篇 |
2011年 | 7386篇 |
2010年 | 4947篇 |
2009年 | 4651篇 |
2008年 | 4643篇 |
2007年 | 4039篇 |
2006年 | 3891篇 |
2005年 | 3450篇 |
2004年 | 3612篇 |
2003年 | 2722篇 |
2002年 | 2468篇 |
2001年 | 1936篇 |
2000年 | 1559篇 |
1999年 | 1499篇 |
1998年 | 1299篇 |
1997年 | 1138篇 |
1996年 | 1127篇 |
1995年 | 1012篇 |
1994年 | 864篇 |
1993年 | 1058篇 |
1992年 | 1080篇 |
1991年 | 772篇 |
1990年 | 733篇 |
1989年 | 641篇 |
1988年 | 358篇 |
1987年 | 254篇 |
1986年 | 262篇 |
1985年 | 246篇 |
1984年 | 154篇 |
1983年 | 105篇 |
1982年 | 92篇 |
1981年 | 59篇 |
1980年 | 25篇 |
1979年 | 19篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1957年 | 12篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
以疏基丙酸(MPA)为修饰剂,制备了水溶性CdZnTe量子点,研究了pH值,回流时间对CdZnTe量子点荧光强度的影响.基于Ag离子对CdZnTe量子点的淬灭作用,建立了一种新的测定Ag离子的方法.在最优试验条件下,Ag离子浓度在2×10-7~2×10-6 mol/L时与CdZnTe量子点荧光强度呈线性关系,线性回归方程为△F =-7 ×10-5c+5×10-5,相关系数R=0.9787.该量子点荧光分析方法简便快速、灵敏度高、选择性好. 相似文献
72.
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
73.
Developing efficient glycosylation methods and strategies is always a top priority and endless pursuit for carbohydrate chemists to acquire complex glycosidic linkages.While most glycosylation reactions are step-wise,that is,installation of the leaving group at the anomeric position first followed by activation and coupling with acceptors(Scheme 1a),dehydrative glycosylation is obviously more straightforward.[1]In this strategy,C1-hemiacetals are directly activated to couple with acceptors,thus obviating additional C1 modification steps(Scheme 1b).Unfortunately,the intrinsic stability of C1-hemiacetals impedes their applications. 相似文献
74.
Zhang Hanshuai Sheng Xiaohui Wang Siwen Xu Tao 《Journal of Thermal Analysis and Calorimetry》2020,141(3):1183-1195
Journal of Thermal Analysis and Calorimetry - Nowadays, the stability and heat transfer properties of nanofluids have been extensively studied. However, for the practical application, the dynamic... 相似文献
75.
Journal of Statistical Physics - In this paper, averaging principle for the time-dependent stochastic evolution equations (TDSEEs) with infinite delay is investigated. In proper non-Lipschitz... 相似文献
76.
Numerical Algorithms - This paper is concerned with the construction of efficient preconditioners for systems arising from implicit Runge-Kutta time discretization methods for one-dimensional and... 相似文献
77.
78.
采用密度泛函理论的B3LYP, B3P86, B1B95, P3PW91和PBE1PBE方法结合SDD, LANL2DZ和CEP-121G基组计算了d~(10)组态二聚物MN(M=Ga, Ge, In, Sn和Sb; N=M和Al)的几何结构.采用B3P86/SDD进一步研究了MN@H_2O团簇的几何结构及吸附能.结果表明,水分子结合在二聚物M_2上时,对二聚物影响较大,对水分子自身影响较小.将M_2中Ga, Ge, In, Sn或Sb替换一个原子为Al时,水分子在GeAl和SnAl上的吸附能变化较大,而在GaAl, InAl和SbAl上吸附能变化较小.另外, H_2O吸附在Ga, Ge, In, Sn和Sb上时,与吸附在Al上时,吸附能的变化不大. 相似文献
79.
This paper develops a modified smoothed particle hydrodynamics (SPH) method to model the coalescence of colliding non-Newtonian liquid droplets. In the present SPH, a van der Waals (vdW) equation of state is particularly used to represent the gas-to-liquid phase transition similar to that of a real fluid. To remove the unphysical behavior of the particle clustering, also known as tensile instability, an optimized particle shifting technique is implemented in the simulations. To validate the numerical method, the formation of a Newtonian vdW droplet is first tested, and it clearly demonstrates that the tensile instability can be effectively removed. The method is then extended to simulate the head-on binary collision of vdW liquid droplets. Both Newtonian and non-Newtonian fluid flows are considered. The effect of Reynolds number on the coalescence process of droplets is analyzed. It is observed that the time up to the completion of the first oscillation period does not always increase as the Reynolds number increases. Results for the off-center binary collision of non-Newtonian vdW liquid droplets are lastly presented. All the results enrich the simulations of the droplet dynamics and deepen understandings of flow physics. Also, the present SPH is able to model the coalescence of colliding non-Newtonian liquid droplets without tensile instability. 相似文献
80.
Jin Chen Dr. Chun-Li Hu Xiao-Han Zhang Dr. Bing-Xuan Li Dr. Bing-Ping Yang Prof. Jiang-Gao Mao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5419-5422
The first alkali-metal vanadium iodate fluoride, CsVO2F(IO3), with a novel 3D anionic framework, has been rationally designed and hydrothermally synthesized. The 3D [VO2F(IO3)]− framework in CsVO2F(IO3) is built from 0D Λ-shaped cis-[VO3F(IO3)2]4− polyanions via corner-sharing of oxo anions and bridging of the iodate groups. CsVO2F(IO3) displays both a strong second-harmonic generation (SHG) 1.1 times as strong as KTiOPO4 (KTP) under 2.05 μm laser radiation and high laser-induced damage threshold (LIDT) of 107.9 MW cm−2. This work provides a new route to design SHG crystals with stable 3D anionic structures from low-dimensional structural building units. 相似文献