全文获取类型
收费全文 | 44754篇 |
免费 | 714篇 |
国内免费 | 106篇 |
专业分类
系统科学 | 1241篇 |
丛书文集 | 779篇 |
教育与普及 | 99篇 |
理论与方法论 | 496篇 |
现状及发展 | 18314篇 |
研究方法 | 1588篇 |
综合类 | 22554篇 |
自然研究 | 503篇 |
出版年
2018年 | 781篇 |
2017年 | 796篇 |
2016年 | 548篇 |
2012年 | 804篇 |
2011年 | 2002篇 |
2010年 | 1053篇 |
2009年 | 628篇 |
2008年 | 1165篇 |
2007年 | 1565篇 |
2006年 | 734篇 |
2005年 | 782篇 |
2004年 | 774篇 |
2003年 | 896篇 |
2002年 | 774篇 |
2001年 | 1154篇 |
2000年 | 1072篇 |
1999年 | 740篇 |
1992年 | 704篇 |
1991年 | 563篇 |
1990年 | 603篇 |
1989年 | 598篇 |
1988年 | 602篇 |
1987年 | 614篇 |
1986年 | 582篇 |
1985年 | 745篇 |
1984年 | 589篇 |
1983年 | 496篇 |
1982年 | 446篇 |
1981年 | 437篇 |
1980年 | 573篇 |
1979年 | 1220篇 |
1978年 | 1038篇 |
1977年 | 1026篇 |
1976年 | 761篇 |
1975年 | 827篇 |
1974年 | 1132篇 |
1973年 | 1014篇 |
1972年 | 1077篇 |
1971年 | 1261篇 |
1970年 | 1636篇 |
1969年 | 1263篇 |
1968年 | 1214篇 |
1967年 | 1245篇 |
1966年 | 1061篇 |
1965年 | 756篇 |
1959年 | 446篇 |
1958年 | 682篇 |
1957年 | 542篇 |
1956年 | 458篇 |
1954年 | 424篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol. 相似文献
43.
44.
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
45.
46.
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
47.
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
48.
49.
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
50.
Kang J.Y. Xu F.C. 《中国科学基金(英文版)》2004,(2):57-58,64
1 Introduction
Nanoscale science and technology have attracted greatattention since the novel properties become dominant for well-known materials as their sizes reduced to some critical dimension. These properties frequently originate in lattice distortions, structure transformations etc[1]. The variations of size and structure ofnanocrystals lead to the change of their electronic structures. Very recently, nanoscale materials with different electronic structures were utilized in fabricating nanoscale junctions[2].
…… 相似文献