全文获取类型
收费全文 | 9064篇 |
免费 | 703篇 |
国内免费 | 225篇 |
专业分类
系统科学 | 1183篇 |
丛书文集 | 106篇 |
教育与普及 | 167篇 |
理论与方法论 | 284篇 |
现状及发展 | 900篇 |
研究方法 | 24篇 |
综合类 | 7323篇 |
自然研究 | 5篇 |
出版年
2024年 | 31篇 |
2023年 | 44篇 |
2022年 | 69篇 |
2021年 | 85篇 |
2020年 | 48篇 |
2019年 | 19篇 |
2018年 | 754篇 |
2017年 | 763篇 |
2016年 | 459篇 |
2015年 | 112篇 |
2014年 | 126篇 |
2013年 | 121篇 |
2012年 | 401篇 |
2011年 | 1093篇 |
2010年 | 927篇 |
2009年 | 608篇 |
2008年 | 695篇 |
2007年 | 932篇 |
2006年 | 127篇 |
2005年 | 165篇 |
2004年 | 226篇 |
2003年 | 263篇 |
2002年 | 206篇 |
2001年 | 144篇 |
2000年 | 122篇 |
1999年 | 221篇 |
1998年 | 150篇 |
1997年 | 152篇 |
1996年 | 154篇 |
1995年 | 127篇 |
1994年 | 117篇 |
1993年 | 100篇 |
1992年 | 84篇 |
1991年 | 84篇 |
1990年 | 68篇 |
1989年 | 62篇 |
1988年 | 71篇 |
1987年 | 28篇 |
1986年 | 14篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1976年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有9992条查询结果,搜索用时 203 毫秒
21.
LUO HaiYing WANG YunFang KONG Wei PEI XueTao 《科学通报(英文版)》2007,52(18):2449-2456
Today, liver transplantation (LT) is the only established treatment for end-stage liver diseases. The de- velopment of LT, including OLT, cadaveric LT, split LT, living donor LT (LDLT), brings hopes to patients with these diseases. However, increasing donor shortage, rejection and life-long immunosuppression with its side effects are the major limitations of this therapy strategy. Bone marrow-derived stem cells (BMDSCs) are capable of differentiating into hepatocyte-like cells and contribute to liver injury repair. The microenvironment of liver injury caused by rejection, ischemia/reperfusion, loss of liver mass, recurrence of HCV and "small-for-size syndrome" after LT can attract a variety of bone marrow-derived stem cell population to the peripheral circulation and then migration to the injury liver to promote the hepatic function restoration. Additionally, BMDSCs can also take part in the functional regeneration of living donor liver after LDLT. This participation in liver regeneration may be associated to the interac- tion between SDF-1and its receptor CXCR4, involving HGF, IL-8, MMP9, and VEGF/VEGFR-2. BMDSC with its bio-characteristics could maintain the allograft tolerance from different angles and in different ways. In conclusion, BMDSCs transplantation, as a new assistant therapeutic method for LT, will ex- pand the space of LT, and provide more survival opportunities for the patients suffering liver diseases in the future. 相似文献
22.
关于线性NDDE振动性的代数判据(Ⅰ) 总被引:1,自引:0,他引:1
本文给一阶线性自治中立型方程一切解振动的充要条件,这些条件仅依赖于系统的参数,从而对自治系统彻底解决了[1]中提出的问题12 相似文献
23.
The exponential Radon transform, a generalization of the Radon transform, is defined and studied as a mapping of function
spaces. It is represented in terms of Fourier transform of its domain and range, and this leads to the harmonic decomposition
reconstruction. The results are similar results of Tretiak and Metz.
Foundation item: Supported by the National Natural Science Foundation of China (No. 19971064), Key Project of Science and
Technology of Hubei Province Education Committee.
Biography: Wang Jin-ping (1963-), male, Ph.D. candidate, research direction: numberical solution of singular integral equation
and integral transformation etc. 相似文献
24.
YU Jianqiao LIAO Jianwei 《武汉大学学报:自然科学英文版》2007,12(5):887-892
We propose a multiple-tree overlay structure for resource discovery in unstructured P2P systems. Peers that have similar interests or hold similar type of resources will be grouped into a tree-like cluster. We exploit the heterogeneity of peers in each cluster by connecting peers with more capacities closer to the root of the tree. The capacity of a peer can be defined in different ways (e.g. higher network bandwidth, larger disk space, more data items of a certain type etc.) according to different needs of users or applications. 相似文献
25.
In October 1924, The Physical Review, a relatively minor journal at the time, published a remarkable two-part paper by John H. Van Vleck, working in virtual isolation
at the University of Minnesota. Using Bohr’s correspondence principle and Einstein’s quantum theory of radiation along with
advanced techniques from classical mechanics, Van Vleck showed that quantum formulae for emission, absorption, and dispersion
of radiation merge with their classical counterparts in the limit of high quantum numbers. For modern readers Van Vleck’s
paper is much easier to follow than the famous paper by Kramers and Heisenberg on dispersion theory, which covers similar
terrain and is widely credited to have led directly to Heisenberg’s Umdeutung paper. This makes Van Vleck’s paper extremely valuable for the reconstruction of the genesis of matrix mechanics. It also
makes it tempting to ask why Van Vleck did not take the next step and develop matrix mechanics himself.
This paper was written as part of a joint project in the history of quantum physics of the Max Planck Institut für Wissenschaftsgeschichte and the Fritz-Haber-Institut in Berlin. 相似文献
26.
DING Mingtao WEI Fangqiang ZHANG Jinghong WANG Hongjuan 《武汉大学学报:自然科学英文版》2007,12(4):599-604
By analyzing the observation data from Dongchuan Debris Flow Observation and Research Station and historical data from year 1965 to 1990 gotten from National Astronomical Ob-servatories/Yunnan Observatory,the responding of debris flow in Jiangjia Ravine to Solar Proton Flare is studied. The following conclusion can be drawn. Solar Proton Flare,as one of most im-portant astronomical factors,affects the activity of debris flow in Yunnan. Generally,from 1965 to1990,the more active Solar Pro-ton Flare is,the greater the probability of high frequency and large runoff of debris flow is. On the contrary,the less active Solar Pro-ton Flare is,the greater the probability of low frequency,small runoff,and low sediment transport of debris flow is. 相似文献
27.
The unified chaotic system contains the Lorenz system and the Chen system as two dual systems at the two extremes of its parameter
spectrum. This paper presents the design of bang bang controller for unified system and multitude of numerical experiments
under various control parameters. Numerical experiments meet the theoretic proof perfectly and convincingly demonstrated the
controller can be effectively used for unified systems with uncertainty of the equilibrium points. The method enriches the
applications of chaotic control.
Foundation item: Supported by the National Natural Science Foundation of China(50209012)
Biography: Deng Xiao-ming (1980-), male, Master candidate, research direction: chaos control. 相似文献
28.
感应加热钢包炉是国外新发展的一种二次精炼及加热设备,具有高效、低能耗、无污染的特点,本文在感应加热钢包炉电磁与结构分析工作的基础上,用电磁场数值模拟方法对感应加热钢包炉的电磁设计和包壳结构进行优化。 相似文献
29.
本文研究了在不同pH值下吐温—80.Tritonx—100.SLS三种表面活性剂四—(对-三甲铵苯基)卟啉Soret带的影响。 相似文献
30.
希尔伯特变换器优化设计研究 总被引:2,自引:0,他引:2
提出了一种基于神经网络算法的希尔伯特变换器优化设计方法,证明了神经网络算法的收敛性,提出了希尔伯特变换器的优化设计实例。仿真结果表明了该网络模型是高效的神经网络模型。 相似文献