全文获取类型
收费全文 | 24226篇 |
免费 | 4030篇 |
国内免费 | 5023篇 |
专业分类
化学 | 18756篇 |
晶体学 | 571篇 |
力学 | 1533篇 |
综合类 | 551篇 |
数学 | 2946篇 |
物理学 | 8922篇 |
出版年
2024年 | 41篇 |
2023年 | 320篇 |
2022年 | 680篇 |
2021年 | 684篇 |
2020年 | 822篇 |
2019年 | 875篇 |
2018年 | 799篇 |
2017年 | 907篇 |
2016年 | 1129篇 |
2015年 | 1256篇 |
2014年 | 1493篇 |
2013年 | 1886篇 |
2012年 | 2025篇 |
2011年 | 2113篇 |
2010年 | 1724篇 |
2009年 | 1776篇 |
2008年 | 1942篇 |
2007年 | 1747篇 |
2006年 | 1707篇 |
2005年 | 1385篇 |
2004年 | 1271篇 |
2003年 | 991篇 |
2002年 | 1244篇 |
2001年 | 1035篇 |
2000年 | 825篇 |
1999年 | 598篇 |
1998年 | 355篇 |
1997年 | 250篇 |
1996年 | 240篇 |
1995年 | 223篇 |
1994年 | 164篇 |
1993年 | 170篇 |
1992年 | 128篇 |
1991年 | 85篇 |
1990年 | 78篇 |
1989年 | 69篇 |
1988年 | 54篇 |
1987年 | 45篇 |
1986年 | 32篇 |
1985年 | 28篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1971年 | 3篇 |
1957年 | 2篇 |
1936年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Yah ZHAO Xiao Qing LIU Hong You ZHU Zi Ming YANG Rong HUANG 《中国化学快报》2006,17(12):1543-1546
Bridged bis(β-cyclodextrin)s (CDs), as a very important family of CD derivatives, have been known that they can significantly alter the molecular binding ability and selectivity toward a variety of guests in comparison with parent cyclodextrin. Their two… 相似文献
102.
By numerical simulations on frequency dependence of the spiking threshold, i.e. on the critical amplitude of periodic stimulus, for a neuron to fire, we find that bushy cells in the cochlear nuclear exhibit frequency selec- tivity behaviour. However, the selective frequency band of a bushy cell is far away from that of the preferred spectral range in human and mammal auditory perception. The mechanism underlying this neural activity is also discussed. Further studies show that the ion channel densities have little impact on the selective frequency band of bushy cells. These findings suggest that the neuronal behaviour of frequency selectivity in bushy cells at both the single cell and population levels may be not functionally relevant to frequency discrimination. Our results may reveal a neural hint to the reconsideration on the busily cell functional role in auditory information processing of sound frequency. 相似文献
103.
饲喂频率对鲈鱼生长及体生化成分的影响 总被引:2,自引:0,他引:2
选取同一种饵料设置1次·d-1、2次·d-1、3次·d-1、4次·d-14个饲喂频率,采用静水连续充气养殖系统,在盐度为26.0%~27.0%、温度为26~30℃条件下对鲈鱼(85.95±2.04)g进行为期40d的生长实验.结果表明:(1)饲喂频率影响鲈鱼的生长是由食物转化率和摄食率的提高共同引起的.(2)水分含量随饲喂频率的增高而保持不变;蛋白质含量随饲喂频率的增加,基本保持不变;脂肪含量随饲喂频率的增高而明显减少;灰分含量随饲喂频率的增多而明显增加.(3)鲈鱼的适宜饲喂频率为2次·d-1. 相似文献
104.
We propose a method to realize the teleportation of an unknown entangled state that consists of many qudits through a partially entangled-qudit quantum channel with the help of 2 log2 d-bit classical communication. The operations used in the teleportation process include a generalized Bell-state measurement and a series of singlequdit π-measurements performed by Alice, a series of generalized qudit-Pauli gates and two-level unitary gates, as well as a qubit measurement performed by Bob. For a maximally entangled quantum channel, the successful probability of the teleportation becomes unit. 相似文献
105.
106.
On Polynomial Functions over Finite Commutative Rings 总被引:1,自引:0,他引:1
Jian Jun JIANG Guo Hua PENG Qi SUN Qi Fan ZHANG 《数学学报(英文版)》2006,22(4):1047-1050
Let R be an arbitrary finite commutative local ring. In this paper, we obtain a necessary and sufficient condition for a function over R to be a polynomial function. Before this paper, necessary and sufficient conditions for a function to be a polynomial function over some special finite commutative local rings were obtained. 相似文献
107.
Jian Ming ZHAN Bijan DAVVAZ K. P. SHUM 《数学学报(英文版)》2007,23(8):1345-1356
We describe the relationship between the fuzzy sets and the algebraic hyperstructures. In fact, this paper is a continuation of the ideas presented by Davvaz in (Fuzzy Sets Syst., 117: 477- 484, 2001) and Bhakat and Das in (Fuzzy Sets Syst., 80: 359-368, 1996). The concept of the quasicoincidence of a fuzzy interval value with an interval-valued fuzzy set is introduced and this is a natural generalization of the quasi-coincidence of a fuzzy point in fuzzy sets. By using this new idea, the concept of interval-valued (α,β)-fuzzy sub-hypermodules of a hypermodule is defined. This newly defined interval-valued (α,β)-fuzzy sub-hypermodule is a We shall study such fuzzy sub-hypermodules and sub-hypermodules of a hypermodule. generalization of the usual fuzzy sub-hypermodule. consider the implication-based interval-valued fuzzy 相似文献
108.
超子中子星性质的温度效应 总被引:2,自引:0,他引:2
从相对论平均场理论出发,考虑核子、超子和介子的相互作用,研究了温度对中子星组成粒子、状态方程和中子星质量等的影响.发现温度越高,超子在中子星内部出现时的重子数密度越低.当密度较高时,中子星的核心区主要由超子组成,即中子星转变成以奇异粒子为主要成分的超子星,并且这种转变受到温度的影响,温度越高,转变密度越低.由于超子的出现,中子星核心高密度区域的状态方程,对于不同温度,差别不大,所以有限温度中子星的最大质量都在1.8M⊙附近.这与观测结果相符. 相似文献
109.
Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed. 相似文献
110.