全文获取类型
收费全文 | 1824篇 |
免费 | 66篇 |
国内免费 | 69篇 |
专业分类
化学 | 848篇 |
晶体学 | 5篇 |
力学 | 67篇 |
综合类 | 2篇 |
数学 | 464篇 |
物理学 | 573篇 |
出版年
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 48篇 |
2020年 | 51篇 |
2019年 | 52篇 |
2018年 | 51篇 |
2017年 | 55篇 |
2016年 | 76篇 |
2015年 | 43篇 |
2014年 | 59篇 |
2013年 | 95篇 |
2012年 | 69篇 |
2011年 | 100篇 |
2010年 | 74篇 |
2009年 | 69篇 |
2008年 | 60篇 |
2007年 | 54篇 |
2006年 | 74篇 |
2005年 | 78篇 |
2004年 | 142篇 |
2003年 | 129篇 |
2002年 | 83篇 |
2001年 | 77篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 25篇 |
1992年 | 23篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 21篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1911年 | 4篇 |
排序方式: 共有1959条查询结果,搜索用时 31 毫秒
1.
Anh Ha Lan Nhan Dang Duc Frew Russell Quynh Tran Minh 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3613-3621
Journal of Radioanalytical and Nuclear Chemistry - This research aimed to authenticate the geographical origin of imported fresh apples using isotopic techniques. The results show that the... 相似文献
2.
3.
4.
A novel microfluidic droplet generator is proposed, which can control the droplet size through turning an integrated micrometer head with ease, and the size of the produced micro-droplet can be automatically and real-time monitored by an open-sourced software and off-the-shelf hardware. 相似文献
5.
Pham The Anh Artur Babiarz Adam Czornik Michal Niezabitowski Stefan Siegmund 《Mathematical Methods in the Applied Sciences》2020,43(13):7815-7824
In this paper, we establish some criteria for boundedness, stability properties, and separation of solutions of autonomous nonlinear nabla Riemann-Liouville scalar fractional difference equations. To derive these results, we prove the variation of constants formula for nabla Riemann-Liouville fractional difference equations. 相似文献
6.
Leiqing Hu Sankhajit Pal Hien Nguyen Vinh Bui Haiqing Lin 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2467-2481
Over the last two decades, polymers with superior H2/CO2 separation properties at 100–300 °C have gathered significant interest for H2 purification and CO2 capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H2/CO2 separation and the advantages of high-temperature operation (such as improved solubility selectivity and absence of CO2 plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H2 and CO2, including functional polymers (such as polybenzimidazole) and engineered polymers by cross-linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size-sieving or H2-sorptive nanofillers with attractive H2/CO2 separation properties. 相似文献
7.
Numerical Algorithms - In this paper, we introduce a self-adaptive inertial gradient projection algorithm for solving monotone or strongly pseudomonotone variational inequalities in real Hilbert... 相似文献
8.
A dynamic mathematical model is developed for production of Cerenol polyether from 1,3‐propanediol in a batch reactor system. The model accounts for polycondensation reactions and side reactions in the liquid phase and for mass transfer of volatile species to the vapor. Parameters are estimated using measured liquid‐phase concentrations of monomer, oligomers, water, and end groups as well as the mass and composition of condensate collected from the overhead condenser system. The proposed model uses novel probability factors to keep the model equations relatively simple while accounting for the complex influence of superacid catalyst on reaction rates. The model is a significant advance over previous Cerenol models because it better accounts for mass‐transfer rates and for the dynamic behavior of the condenser. In addition, the proposed model accounts for the inhibitory influence of water on polycondensation kinetics due to hydration of hydroxyl ends. The model equations and parameter estimates provide a substantial improvement in fit to the data, especially for long reaction times and high catalyst levels, resulting in a 97% reduction in the value of the weighted least squared objective function compared to equations and parameters from a previous model. 相似文献
9.
Anh N. Hong Diana Luong Mohammed Alghamdi Wei-Cheng Liao Weiyi Zhang Emily Kusumoputro Yichong Chen Prof. P. Alex Greaney Prof. Yongtao Cui Prof. Jing Shi Prof. Xianhui Bu Prof. Boniface P. T. Fokwa Prof. Pingyun Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201576
Two new rod-packing metal–organic frameworks (RPMOF) are constructed by regulating the in situ formation of the capping agent. In CPM-s7, carboxylate linkers extend 1D manganese-oxide chains in four additional directions, forming 3D RPMOF. The substitution of Mn2+ with a stronger Lewis acidic Co2+, leads to an acceleration of the hydrolysis-prone sulfonate linker, resulting in presence of sulfate ions to reduce two out of the four carboxylate-extending directions, and thus forming a new 2D rod-packing CPM-s8. Density functional theory calculations and magnetization measurements reveal ferrimagnetic ordering of CPM-s8, signifying the potential of exploring 2D RPMOF for effective low-dimensional magnetic materials. 相似文献
10.
Differential Equations - We consider compact difference schemes of approximation order $$4+2 $$ on a three-point spatial stencil for the Klein–Gordon equations with constant and variable... 相似文献