全文获取类型
收费全文 | 103933篇 |
免费 | 19143篇 |
国内免费 | 8792篇 |
专业分类
化学 | 85678篇 |
晶体学 | 1010篇 |
力学 | 5312篇 |
综合类 | 598篇 |
数学 | 10947篇 |
物理学 | 28323篇 |
出版年
2024年 | 145篇 |
2023年 | 1410篇 |
2022年 | 1567篇 |
2021年 | 2403篇 |
2020年 | 3637篇 |
2019年 | 4721篇 |
2018年 | 3134篇 |
2017年 | 2628篇 |
2016年 | 6064篇 |
2015年 | 6253篇 |
2014年 | 6802篇 |
2013年 | 8673篇 |
2012年 | 8729篇 |
2011年 | 8317篇 |
2010年 | 6905篇 |
2009年 | 6850篇 |
2008年 | 6628篇 |
2007年 | 5639篇 |
2006年 | 5159篇 |
2005年 | 4744篇 |
2004年 | 3938篇 |
2003年 | 3267篇 |
2002年 | 3835篇 |
2001年 | 3016篇 |
2000年 | 2740篇 |
1999年 | 2021篇 |
1998年 | 1467篇 |
1997年 | 1282篇 |
1996年 | 1302篇 |
1995年 | 1139篇 |
1994年 | 1079篇 |
1993年 | 922篇 |
1992年 | 828篇 |
1991年 | 713篇 |
1990年 | 608篇 |
1989年 | 520篇 |
1988年 | 393篇 |
1987年 | 380篇 |
1986年 | 326篇 |
1985年 | 322篇 |
1984年 | 216篇 |
1983年 | 189篇 |
1982年 | 161篇 |
1981年 | 121篇 |
1980年 | 93篇 |
1978年 | 59篇 |
1977年 | 56篇 |
1976年 | 58篇 |
1975年 | 60篇 |
1973年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
181.
182.
采用甚高频等离子体增强化学气相沉积技术制备了系列微晶硅薄膜太阳电池,指出了气体总流量和背反射电极的类型对电池性能参数的影响.电池的I-V测试结果表明:随反应气体总流量的增加,对应电池的短路电流密度、开路电压和填充因子都有很大程度的提高,结果使得电池的光电转换效率得以提高.另外,ZnO/Ag/Al背反射电极能明显提高电池的短路电流密度,进而也提高了电池的光电转换效率.对气体总流量和背反射电极类型影响电池效率的原因进行了分析.
关键词:
微晶硅薄膜太阳电池
气体流量
ZnO/Ag/Al背反射电极 相似文献
183.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
184.
Electrical impedance measurements of Na3H(SO4)2 were performed as a function of both temperature and frequency. The electrical conductivity and dielectric relaxation have been evaluated. The temperature dependence of electrical conductivity reveals that the sample crystals transformed to the fast ionic state in the high temperature phase. The dynamical disordering of hydrogen and sodium atoms and the orientation of SO4 tetrahedra results in fast ionic conductivity. In addition to the proton conduction, the possibility of a Na+ contribution to the conductivity in the high temperature phase is proposed. The frequency dependence of AC conductivity is proportional to ωs. The value of the exponent, s, lies between 0.85 and 0.46 in the room temperature phase, whereas it remains almost constant, 0.6, in the high-temperature phase. The dielectric dispersion is examined using the modulus formalism. An Arrhenius-type behavior is observed when the crystal undergoes the structural phase transition. 相似文献
185.
186.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
187.
1引言设A是n阶非负方阵.设矩阵方程(1)AXA=A,(2)XAX=X,(3)(AX)~T= AX,(4)(XA)~T=XA,(5)AX=XA.A具有非负广义逆是指存在非负方阵X满足方程(1)~(4),并记为A~(?).A具有非负群逆是指存在非负方阵X满足方程(1),(2),(5),并记为A~#.在A~(?)存在的前提下,两者相同的充分必要条件有(a)AA~(?)=A~(?)A;(b)A~(?)=p(A),其 相似文献
188.
The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer 总被引:4,自引:0,他引:4
X.Y. Chen K.H. Wong C.L. Mak J.M. Liu X.B. Yin M. Wang Z.G. Liu 《Applied Physics A: Materials Science & Processing》2002,75(4):545-549
Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO3 (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find
that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111)
and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions
of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were
of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented,
(100)-oriented and polycrystalline LNO, respectively.
Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002 相似文献
189.
We introduce a new scheme for the future application of Real-coded Lattice Gas (RLG) to the numerical simulation of suspended solid objects in a fluctuating fluid environment. The reproduction of Brownian motion for a single solid object is verified through the Gaussian distribution of its displacements. The effectiveness of the solid–solid interaction model is also confirmed in an N-body simulation. 相似文献
190.