全文获取类型
收费全文 | 10154篇 |
免费 | 2179篇 |
国内免费 | 1435篇 |
专业分类
化学 | 7548篇 |
晶体学 | 177篇 |
力学 | 613篇 |
综合类 | 118篇 |
数学 | 1038篇 |
物理学 | 4274篇 |
出版年
2024年 | 53篇 |
2023年 | 307篇 |
2022年 | 495篇 |
2021年 | 601篇 |
2020年 | 600篇 |
2019年 | 564篇 |
2018年 | 472篇 |
2017年 | 425篇 |
2016年 | 559篇 |
2015年 | 685篇 |
2014年 | 744篇 |
2013年 | 856篇 |
2012年 | 1026篇 |
2011年 | 977篇 |
2010年 | 663篇 |
2009年 | 707篇 |
2008年 | 742篇 |
2007年 | 601篇 |
2006年 | 547篇 |
2005年 | 415篇 |
2004年 | 310篇 |
2003年 | 225篇 |
2002年 | 220篇 |
2001年 | 156篇 |
2000年 | 148篇 |
1999年 | 115篇 |
1998年 | 98篇 |
1997年 | 71篇 |
1996年 | 64篇 |
1995年 | 49篇 |
1994年 | 40篇 |
1993年 | 42篇 |
1992年 | 33篇 |
1991年 | 19篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1966年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Preparation of activated carbons and their adsorption properties for greenhouse gases: CH4 and CO2 总被引:1,自引:0,他引:1
Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ?C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases. 相似文献
992.
993.
Zhi‐Hao Cao 《Numerical Linear Algebra with Applications》2009,16(6):503-516
In this note, results concerning the eigenvalue distribution and form of the eigenvectors of the constraint preconditioned generalized saddle point matrix and its minimal polynomial are given. These results extend previous ones that appeared in the literature. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
994.
Liuhua ChenLihua Gan Mingxian LiuRong Fan Zijie XuZhixian Hao Longwu Chen 《Applied Surface Science》2011,257(11):5070-5076
The effect of tryptophan on the membrane stability was studied by using three artificial biological membranes including liposome, Langmuir monolayer and solid supported bilayer lipid membrane (s-BLM) as models. All the results indicate that the penetration of tryptophan can destabilize different artificial biological membranes. The diameter of liposome and the leakage of calcein from liposome increased with the increase of tryptophan concentration because the penetration of tryptophan was beneficial for dehydrating the polar head groups of lipids and the formation of fusion intermediates. π-A isotherms of lecithin on the subphase of tryptophan solution further confirm that tryptophan can penetrate into lipid monolayer and reduce the stability of lipid monolayer. When the concentration of tryptophan increased from 0 to 2 × 10−3 mol L−1, the limiting molecular area of lecithin increased from 110.5 to 138.5 Å2, but the collapse pressure of the monolayer decreased from 47.6 to 42.3 mN m−1, indicating the destabilization of lipid monolayer caused by the penetration of tryptophan. The resistance spectra of s-BLM demonstrate that the existence of tryptophan leads to the formation of some defects in s-BLM and the destabilization of s-BLM. The values of electron-transfer resistance and double layer capacitance respectively decreased from 5.765 × 106 Ω and 3.573 × 10−8 F to 1.391 × 106 Ω and 3.340 × 10−8 F when the concentration of tryptophan increased from 0 to 2 × 10−3 mol L−1. Correspondingly, the breakdown voltage of s-BLM decreased from 2.51 to 1.72 V. 相似文献
995.
Novel correction method for X-ray beam energy fluctuation of high energy DR system with a linear detector 总被引:1,自引:0,他引:1
A high energy digital radiography (DR) testing system has generated diverse scientific and technological interest in the field of industrial non-destructive testing. However, due to the limitations of manufacturing technology for accelerators, an energy fluctuation of the X-ray beam exists and leads to bright and dark streak artifacts in the DR image. Here we report the utilization of a new software-based method to correct the fluctuation artifacts. The correction method is performed using a high pass filtering operation to extract the high frequency information that reflects the X-ray beam energy fluctuation, and then subtracting it from the original image. Our experimental results show that this method is able to rule out the artifacts effectively and is readily implemented on a practical scanning system. 相似文献
996.
以鸡蛋的卵清蛋白作为蛋白质药物模板、生物可降解材料聚己内酯(PCL)为药物载体模板,采用同轴电喷法制备PCL-蛋清体系的复合微球.研究了电导率、黏度对于电喷微球成型的影响.核壳溶液推进速率比、电压、溶液质量分数和接收距离等对于所得微球表面形态和结构的影响.利用扫描电子显微镜(SEM)研究了微球的表面形态,用荧光显微镜表征了微球的包覆模式.结果表明:同轴电喷法可以制备PCL-蛋清体系的复合结构微胶囊,其中推进速率比对微球形貌、粒径及其分布的影响比较明显,当PCL与蛋清溶液推进速率比大于10时,将出现具有包覆结构的微球. 相似文献
997.
998.
999.
Aimin Hao Xiaocui Yang Chunxiao Gao Yonghao Han Yongjun Tian 《Journal of Physics and Chemistry of Solids》2009,70(2):433-438
A theoretical investigation on the structural stabilities and electronic properties of HgTe under high pressure was conducted using first principles based on density functional theory. Our results demonstrate that the sequence of the pressure-induced phase transitions of HgTe is from the zinc blende, to cinnabar, rocksalt, orthorhombic, and CsCl-type structures. The pressure effects on the optical properties were discussed and compared with previous calculations and experimental data whenever available. 相似文献
1000.