全文获取类型
收费全文 | 23618篇 |
免费 | 4711篇 |
国内免费 | 7540篇 |
专业分类
化学 | 16872篇 |
晶体学 | 838篇 |
力学 | 1870篇 |
综合类 | 955篇 |
数学 | 3461篇 |
物理学 | 11873篇 |
出版年
2024年 | 65篇 |
2023年 | 278篇 |
2022年 | 823篇 |
2021年 | 743篇 |
2020年 | 840篇 |
2019年 | 798篇 |
2018年 | 765篇 |
2017年 | 1113篇 |
2016年 | 941篇 |
2015年 | 1198篇 |
2014年 | 1456篇 |
2013年 | 1865篇 |
2012年 | 1861篇 |
2011年 | 2020篇 |
2010年 | 1962篇 |
2009年 | 1932篇 |
2008年 | 2228篇 |
2007年 | 1949篇 |
2006年 | 2042篇 |
2005年 | 1798篇 |
2004年 | 1356篇 |
2003年 | 1018篇 |
2002年 | 993篇 |
2001年 | 1048篇 |
2000年 | 984篇 |
1999年 | 615篇 |
1998年 | 368篇 |
1997年 | 294篇 |
1996年 | 317篇 |
1995年 | 227篇 |
1994年 | 241篇 |
1993年 | 200篇 |
1992年 | 223篇 |
1991年 | 153篇 |
1990年 | 159篇 |
1989年 | 138篇 |
1988年 | 124篇 |
1987年 | 142篇 |
1986年 | 101篇 |
1985年 | 78篇 |
1984年 | 80篇 |
1983年 | 70篇 |
1982年 | 55篇 |
1981年 | 48篇 |
1980年 | 33篇 |
1979年 | 37篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1965年 | 13篇 |
1964年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Positive periodic solution for a two-species ratio-dependent predator-prey system with time delay and impulse 总被引:1,自引:0,他引:1
A two-species ratio-dependent predator-prey model with time delay and impulse is investigated. By using the continuation theorem of coincidence degree theory, the existence of a positive periodic solution for this system is established. 相似文献
72.
����������ƽ������Ӣ�����ȼ�������̺� 《核聚变与等离子体物理》2006,39(3):243-248
As the ITER first wall Be/CuCrZr hot isostatic pressing (HIP) bonding intermediate transition layer, Ti/Cu layer can form a multi-layer intermediate metal phase, and defects such as cracks occur between the Ti/Cu metal phases. CuCrZr was used instead of Be, and a number of CuCrZr/Ti/Cu/CuCrZr joints were fabricated by the same HIP process as Be/CuCrZr to analyze the Ti/Cu joints. The effects of stress relief annealing on joint strength and defect distribution of the joints unannealed, annealed at 400°C and 500°C respectively were studied. The results show that three layers of Ti/Cu diffusion layers are formed on both sides of the intermediate titanium layer, namely Cu4Ti, CuTi and CuTi2. The thickness of Cu4Ti on the pure copper side is thicker than that on the CuCrZr side, so that the crack is almost entirely distributed at the junction of Cu4Ti and CuTi on the pure copper side where brittle fracture is easy to occur in the tensile samples. As the annealing temperature increases, the generation and propagation of cracks decreases. 相似文献
73.
本文观察到了KNbO_3:Fe晶体的时间微分效应,并用这个微分效应进行了图像追踪的演示,为KNbO_3:Fe晶体在光折变器件领域的应用进行了有益的探索。 相似文献
74.
75.
76.
WU Jiada WU Changzheng ZHONG Xiaoxia SONG Zhoumo LI Fuming 《Chinese Journal of Lasers》1997,6(2):161-168
l.IntroductionowingtotheirpromisingproPertiesandPOtentialapplications,transitionmetalni-trideshavedrawngreatattentionandthepreparationandinvestigationofthesecom-poundshavebeenasubjectbothofscientificandoftechnologicalinterest.Transitionmetalnitridescombineadvantagesofexce1lenthardness,highmeltingPOint,goodchemi-calstabilityandhigheIectricalconductivity[11,henceoverlaySofthesecompoundshavefoundwideappIicationsinvariousfie1ds.Molybdenumnitrides,inparticular,havealsoemergedasverypromisingcandi… 相似文献
77.
GPS/SINS组合导航系统在运载火箭中的应用 总被引:1,自引:1,他引:0
针对运载火箭特点,着重研究在发射惯性坐标系下,位置、速度组合模式的GPS/SINS组合导航算法,推导了该坐标系下的惯导一阶误差传播方程,建立了该坐标系下GPS/SINS组合导航系统的状态方程和观测方程,并进行了相关数学仿真验证。仿真结果表明,在该坐标系中,GPS/SINS组合导航算法能较准确地给出运载火箭的位置、速度和姿态信息,提高运载火箭制导精度。 相似文献
78.
研究全稳定广义生灭最小Q过程的可配称性,获得广义生灭最小Q过程是可配称的充分必要条件,以及最小Q过程是唯一的可配称Q过程的充分必要条件. 相似文献
79.
80.
Prisoner's Dilemma Game with Heterogeneous Influential Effect on Regular Small-World Networks 下载免费PDF全文
The effect of heterogeneous influence of different individuals on the maintenance of co-operative behaviour is studied in an evolutionary Prisoner's Dilemma game with players located on the sites of regular small-world networks. The players interacting with their neighbours can either co-operate or defect and update their states by choosing one of the neighbours and adopting its strategy with a probability depending on the pay off difference. The selection of the neighbour obeys a preferential rule: the more influential a neighbour, the larger the probability it is picked. It is found that this simple preferential selection rule can promote continuously the co-operation of the whole population with the strengthening of the disorder of the underlying network. 相似文献