全文获取类型
收费全文 | 95215篇 |
免费 | 6750篇 |
国内免费 | 12505篇 |
专业分类
化学 | 50968篇 |
晶体学 | 2207篇 |
力学 | 1504篇 |
综合类 | 533篇 |
数学 | 18699篇 |
物理学 | 18686篇 |
综合类 | 21873篇 |
出版年
2024年 | 232篇 |
2023年 | 1207篇 |
2022年 | 2301篇 |
2021年 | 2281篇 |
2020年 | 2390篇 |
2019年 | 2476篇 |
2018年 | 2224篇 |
2017年 | 2564篇 |
2016年 | 2674篇 |
2015年 | 2587篇 |
2014年 | 4026篇 |
2013年 | 6628篇 |
2012年 | 5085篇 |
2011年 | 6577篇 |
2010年 | 5503篇 |
2009年 | 6559篇 |
2008年 | 6597篇 |
2007年 | 6916篇 |
2006年 | 6117篇 |
2005年 | 5258篇 |
2004年 | 4864篇 |
2003年 | 4113篇 |
2002年 | 3536篇 |
2001年 | 2724篇 |
2000年 | 2551篇 |
1999年 | 2264篇 |
1998年 | 1781篇 |
1997年 | 1640篇 |
1996年 | 1493篇 |
1995年 | 1390篇 |
1994年 | 1313篇 |
1993年 | 1114篇 |
1992年 | 1028篇 |
1991年 | 773篇 |
1990年 | 593篇 |
1989年 | 526篇 |
1988年 | 409篇 |
1987年 | 317篇 |
1986年 | 265篇 |
1985年 | 289篇 |
1984年 | 204篇 |
1983年 | 114篇 |
1982年 | 170篇 |
1981年 | 176篇 |
1980年 | 134篇 |
1979年 | 100篇 |
1978年 | 95篇 |
1977年 | 96篇 |
1976年 | 73篇 |
1973年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
新生MnO2对酸性媒介黑T的吸附 总被引:4,自引:0,他引:4
以化学法合成的新生MnO2为吸附剂,对水中酸性媒介黑T(染料之一)进行了吸附脱色研究,并探讨了影响吸附的因素。结果表明,酸性媒介黑T的脱色率达95%。且PH是影响染料脱色的主要因素。 相似文献
94.
95.
Srinivasan G. 《物理学报》2006,55(5):2548-2552
讨论了Ni0.8Zn0.2Fe2O4 (NZFO)与锆钛酸铅(PZT)的双层膜结构样品的磁电(ME)效应.NZFO粉料由溶胶-凝胶法制成,再经900℃热压,并高温烧结.在该双层膜中测量到了很强的磁电相互作用.发现横向的磁电效应比纵向效应大一个数量级,并且随NZFO烧结温度的提高而增加.当烧结温度从950℃上升到1380℃时,横向ME电压系数(αE)的最大值变化范围为25.6 mV Am-2≤αE≤199.6 mV Am-2.理论分析显示NZFO-PZT双层膜样品中ME效应源于NZFO与PZT之间相对良好的磁电耦合.
关键词:
镍铁氧体
PZT
热压法
ME效应 相似文献
96.
Wu Hongyi 《高校应用数学学报(英文版)》2006,21(1):96-106
A family of Said-Bézier type generalized Ball (SBGB) bases and surfaces with a parameter H over triangular domain is introduced, which unifies Bézier surface and Said-Ball surface and includes several intermediate
surfaces. To convert different bases and surfaces, the dual functionals of bases are presented. As an application of dual
functionals, the subdivision formulas for surfaces are established. 相似文献
97.
为探讨穴位注射维生素B1佐治小儿腹泻的价值,对1995~2000年收治的178例小儿腹泻患者进行足三里穴位注射维生素B1治疗100例(观察组)与常规治疗78例进行对照,结果两组止泻天数间有显著差异(P<0.01). 相似文献
98.
The breakthrough and stoichiometric SO2 adsorption efficiencies of a biomass supported Na2CO3 system (80 wt %Na2CO3/straw) have reached 48.9% and 80.6% respectively at a desulfurization temperature of 80℃. 相似文献
99.
A construction for Segal operations for K-theory of categories with cofibrations, weak equivalences and a biexact pairing is given and coherence properties of the operations are studied. The model for K-theory, which is used, allows coherence to be studied by means of (symmetric) monoidal functors. In the case of Waldhausen A-theory it is shown how to recover the operations used in Waldhausen (Lecture Notes in Mathematics, Vol. 967, Springer, Berlin, 1982, pp. 390-409) for the A-theory Kahn-Priddy theorem. The total Segal operation for A-theory, which assembles exterior power operations, is shown to carry a natural infinite loop map structure. The basic input is the un-delooped model for K-theory, which has been developed from a construction by Grayson and Gillet for exact categories in Gunnarsson et al. (J. Pure Appl. Algebra 79 (1992) 255), and Grayson's setup for operations in Grayson (K-theory (1989) 247). The relevant material from these sources is recollected followed by observations on equivariant objects and pairings. Grayson's conditions are then translated to the context of categories with cofibrations and weak equivalences. The power operations are shown to be well behaved w.r.t. suspension and are extended to algebraic K-theory of spaces. Staying close with the philosophy of Waldhausen (1982) Waldhausen's maps are found. The Kahn-Priddy theorem follows from splitting the “free part” off the equivariant theory. The treatment of coherence of the total operation in A-theory involves results from Laplaza (Lecture Notes in Mathematics, Vol. 281, Springer, Berlin, 1972, pp. 29-65) and restriction to spherical objects in the source of the operation. 相似文献
100.
F.E. SalmanN. Shash H. Abou El-HadedM.K. El-Mansy 《Journal of Physics and Chemistry of Solids》2002,63(11):1957-1966
AC conductivity and dielectric studies on vanadium phosphate glasses doped with lithium have been carried out in the frequency range 0.2-100 kHz and temperature range 290-493 K. The frequency dependence of the conductivity at higher frequencies in glasses obeys a power relationship, σac=Aωs. The obtained values of the power s lie in the range 0.5≤s≤1 for both undoped and doped with low lithium content which confirms the electron hopping between V4+ and V5+ ions. For doped glasses with high lithium content, the values of s≤0.5 which confirm the domination of ionic conductivity. The study of frequency dependence of both dielectric constant and dielectric loss showed a decrease with increasing frequency while they increase with increasing temperature. The results have been explained on the basis of frequency assistance of electron hopping besides the ionic polarization of the glasses. The bulk conductivity increases with increasing temperature whereas decreases with increasing lithium content which means a reduction of the V5+. 相似文献