全文获取类型
收费全文 | 4239篇 |
免费 | 181篇 |
国内免费 | 332篇 |
专业分类
系统科学 | 866篇 |
丛书文集 | 60篇 |
教育与普及 | 137篇 |
理论与方法论 | 33篇 |
现状及发展 | 6篇 |
研究方法 | 29篇 |
综合类 | 3621篇 |
出版年
2023年 | 15篇 |
2022年 | 51篇 |
2021年 | 101篇 |
2020年 | 76篇 |
2019年 | 28篇 |
2018年 | 45篇 |
2017年 | 16篇 |
2016年 | 28篇 |
2015年 | 42篇 |
2014年 | 264篇 |
2013年 | 314篇 |
2012年 | 295篇 |
2011年 | 278篇 |
2010年 | 109篇 |
2009年 | 107篇 |
2008年 | 117篇 |
2007年 | 237篇 |
2006年 | 159篇 |
2005年 | 177篇 |
2004年 | 146篇 |
2003年 | 238篇 |
2002年 | 122篇 |
2001年 | 146篇 |
2000年 | 182篇 |
1999年 | 352篇 |
1998年 | 123篇 |
1997年 | 105篇 |
1996年 | 169篇 |
1995年 | 152篇 |
1994年 | 157篇 |
1993年 | 35篇 |
1992年 | 63篇 |
1991年 | 32篇 |
1990年 | 24篇 |
1989年 | 23篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有4752条查询结果,搜索用时 15 毫秒
11.
When using differential SAR interferometry (DInSAR) to monitor the surface deformation over a long time scale, it is often strongly affected by the spatial and temporal decorrelations and atmospheric dishomogeneities. The recently developed Permanent Scatterers (PS) technique proposed by Fertti et al. can overcome these difficulties by interpreting time-series of interferometric phase only at coherent point scatterers. In this study, we apply this PS technique using 25 ERS-1/2 scenes from 1992 to 2000 to monitor the subsidence in Suzhou. By using the linear deformation model, the deformation map in Suzhou urban area over the eight years is obtained. And the calculated results are in good agreement with the measurements of leveling. 相似文献
12.
Association scan of 14,500 nonsynonymous SNPs in four diseases identifies autoimmunity variants 总被引:2,自引:0,他引:2
Wellcome Trust Case Control Consortium;Australo-Anglo-American Spondylitis Consortium 《Nature genetics》2007,39(11):1329-1337
We have genotyped 14,436 nonsynonymous SNPs (nsSNPs) and 897 major histocompatibility complex (MHC) tag SNPs from 1,000 independent cases of ankylosing spondylitis (AS), autoimmune thyroid disease (AITD), multiple sclerosis (MS) and breast cancer (BC). Comparing these data against a common control dataset derived from 1,500 randomly selected healthy British individuals, we report initial association and independent replication in a North American sample of two new loci related to ankylosing spondylitis, ARTS1 and IL23R, and confirmation of the previously reported association of AITD with TSHR and FCRL3. These findings, enabled in part by increased statistical power resulting from the expansion of the control reference group to include individuals from the other disease groups, highlight notable new possibilities for autoimmune regulation and suggest that IL23R may be a common susceptibility factor for the major 'seronegative' diseases. 相似文献
13.
Prof. Zhu Zuoyan Vice President of NSFC met with the National Institute of Agricultural Research 《中国科学基金(英文版)》2007,15(1):33
Prof. Zhu Zuoyan, Vice President of NSFC, met with the National Institute of Agricultural Research (INRA) delegation led by its Deputy Director General, Prof. Guy Riba on Jan. 18, 2007. 相似文献
14.
Identification of the Angel -related elements in cyprinid fishes and their phylogenetic implications
Angel-related element belongs to the family of miniature inverted-repeat transposable elements (MITEs). In this paper we report the identification of an Angel- related element in the series Leuciscini of cyprinid fishes, which is located in the second intron of the growth hormone (GH) gene. We have also found that this element is absent in orthologous locus in the series Barbini of cyprinid fishes, that provides new evidence for the monophyly of the series Leuciscini. The insertion of Angel -related element into the GH gene might take place in the common ancestor of the series Leuciscini after its divergence from the series Barbini. The high sequence divergence and relatively broad species distribution of Angel-related elements implies that they might be ancient transposons which appeared about 26 million years ago. 相似文献
15.
Kerberos认证系统的分析和改进 总被引:4,自引:0,他引:4
首先介绍Kerberos的认证过程,特别是分析Kerberos认证协议的局性性,然后采用RSA加密算法的一种Yaksha改进算法,给出一种公钥认证协议,这种协议由用户验证自己产生的时间戳,这样就解决了时间同步的问题,并且克服了Kerberos的某些局限性。 相似文献
16.
The interleukin 1β (IL-1β) cDNA was cloned from the red seabream (Pagrus major) by homology cloning strategy. A cDNA fragment was amplified by PCR using two degenerated primers, which were designed according to the conserved regions of other known IL-1β sequences, and elongated by 3' ends and 5' ends RACE PCR to get the full length coding sequence of red seabream IL-1β (RS IL-1β). The sequence contained 1252 nucleotides that included a 5' untranslated region (UTR) of 84bp, a 3' UTR of 410 bp and an open reading frame (ORF) of 759 nucleotides which could be translated into a putative peptide of 253 amino acids with molecular weight of 28.6 kD and putative isoelectric point pI of 5.29. The deduced peptide contained two potential N-glycosylation sites and an identifiable IL1 family signature, but lacked the signal peptide and the clear ICE cut site, which were common in other nonmammalian IL-1β genes. The RS IL-1β had the highest homology with piscine IL-1β according to phylogenetic tree analysis. 相似文献
17.
Itknownthatsmallamountsoffluxonthesurfaceofstainlesssteelcanincreasethedepthofweldpene trationinTIGweldingbyafactorofthree[1] .Thisprocessisreferredtoas”ATIG”orTIGweldingacti vatedbyflux .Therehavebeenthreepublishedphys icalmechanismsthatarepossiblecontri… 相似文献
18.
The General Machining Process Simulator GMPSXiaoTianyuan,YangGang&LiXin(DepartmentofAutomation,TsinghuaUniversity,Beijing,Chi... 相似文献
19.
收集了上海郊区13个具有明显方言差异人群的头面部数据4项,和台湾高山族10个群体的参数进行聚类分析,发现上海郊区居民中的南方土著人群与台湾高山的遗传关系较近。 相似文献
20.
液-固色谱中流动相组成对保留值的影响——基本关系式的推导 总被引:11,自引:1,他引:10
改变流动相的组成来调节色谱柱的选择性,以适应广泛分析的特殊要求,是液相色谱本质上的优点。为此,必须研究流动相的组成在全浓度范围内改变时,保留值变化的系统数据以及能描述这种变化的关系式,但至今能描述全浓度范围内保留值变化的统一关系式尚未见报 相似文献