全文获取类型
收费全文 | 985篇 |
免费 | 10篇 |
国内免费 | 28篇 |
专业分类
系统科学 | 20篇 |
丛书文集 | 2篇 |
教育与普及 | 3篇 |
理论与方法论 | 12篇 |
现状及发展 | 205篇 |
研究方法 | 131篇 |
综合类 | 624篇 |
自然研究 | 26篇 |
出版年
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 67篇 |
2011年 | 95篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 52篇 |
2007年 | 66篇 |
2006年 | 52篇 |
2005年 | 63篇 |
2004年 | 39篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 40篇 |
2000年 | 42篇 |
1999年 | 20篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 9篇 |
1970年 | 9篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 5篇 |
1965年 | 7篇 |
排序方式: 共有1023条查询结果,搜索用时 46 毫秒
101.
Lee Imshik Li Qing Yang Linjing Wang Xinwen Deng Wenli Wang Chen Bai Chunli 《科学通报(英文版)》1997,42(18):1581-1581
Conclusion A py-pu-py triplex DNA containing the polarity modification by replacing the atom H5 of cytosine with Br was examined, mainly
for the stability of the formation of the triplex DNA. Our computational results show that the conformation of the strand
that contained a replaced H5 by cytosine to Br was destabilized, but the Hoogsteen base pairs were stabilized. Although this
approach of modifying the polarity of DNA base has not been tried before, it shows the possibility to improve the stability
by the polarity modification. 相似文献
102.
Becker-Heck A Zohn IE Okabe N Pollock A Lenhart KB Sullivan-Brown J McSheene J Loges NT Olbrich H Haeffner K Fliegauf M Horvath J Reinhardt R Nielsen KG Marthin JK Baktai G Anderson KV Geisler R Niswander L Omran H Burdine RD 《Nature genetics》2011,43(1):79-84
Primary ciliary dyskinesia (PCD) is a genetically heterogeneous autosomal recessive disorder characterized by recurrent infections of the respiratory tract associated with the abnormal function of motile cilia. Approximately half of individuals with PCD also have alterations in the left-right organization of their internal organ positioning, including situs inversus and situs ambiguous (Kartagener's syndrome). Here, we identify an uncharacterized coiled-coil domain containing a protein, CCDC40, essential for correct left-right patterning in mouse, zebrafish and human. In mouse and zebrafish, Ccdc40 is expressed in tissues that contain motile cilia, and mutations in Ccdc40 result in cilia with reduced ranges of motility. We further show that CCDC40 mutations in humans result in a variant of PCD characterized by misplacement of the central pair of microtubules and defective assembly of inner dynein arms and dynein regulatory complexes. CCDC40 localizes to motile cilia and the apical cytoplasm and is required for axonemal recruitment of CCDC39, disruption of which underlies a similar variant of PCD. 相似文献
103.
104.
Hahn CN Chong CE Carmichael CL Wilkins EJ Brautigan PJ Li XC Babic M Lin M Carmagnac A Lee YK Kok CH Gagliardi L Friend KL Ekert PG Butcher CM Brown AL Lewis ID To LB Timms AE Storek J Moore S Altree M Escher R Bardy PG Suthers GK D'Andrea RJ Horwitz MS Scott HS 《Nature genetics》2011,43(10):1012-1017
105.
Eliane Namie Miyaji Maria Leonor Sarno Oliveira Eneas Carvalho Paulo Lee Ho 《Cellular and molecular life sciences : CMLS》2013,70(18):3303-3326
Streptococcus pneumoniae remains an important cause of disease with high mortality and morbidity, especially in children and in the elderly. The widespread use of the polysaccharide conjugate vaccines in some countries has led to a significant decrease in invasive disease caused by vaccine serotypes, but an increase in disease caused by non-vaccine serotypes has impacted on the overall efficacy of these vaccines on pneumococcal disease. The obvious solution to overcome such shortcomings would be the development of new formulations that provide serotype-independent immunity. This review focuses on the most promising approaches, including protein antigens, whole cell pneumococcal vaccines, and recombinant bacteria expressing pneumococcal antigens. The protective capacity of these vaccine candidates against the different stages of pneumococcal infection, including colonization, mucosal disease, and invasive disease in animal models is reviewed. Some of the human trials that have already been performed or that are currently ongoing are presented. Finally, the feasibility and the possible shortcomings of these candidates in relation to an ideal vaccine against pneumococcal infections are discussed. 相似文献
106.
Lee T. Macdonald 《Annals of science》2013,70(3):201-233
As one of his first acts upon becoming Astronomer Royal in 1835, George Airy made moves to set up a new observatory at Greenwich to study the Earth’s magnetic field. This paper uses Airy’s correspondence to argue that, while members of the reform movement in British science were putting pressure on the Royal Observatory to branch out into geomagnetism and meteorology, Airy established the magnetic observatory on his own initiative, ahead of Alexander von Humboldt’s request for British participation in the worldwide magnetic charting project that later became known as the ‘Magnetic Crusade’. That the Greenwich magnetic observatory did not become operational until 1839 was due to a series of incidental factors that provide a case study in the technical and political obstacles to be overcome in building a new government observatory. Airy attached less importance to meteorology than he did to geomagnetism. In 1840, he set up a full programme of meteorological observations at Greenwich – and thus turned his magnetic observatory into the ‘Magnetic and Meteorological department’ – only as the price of foiling an attempt by Edward Sabine and others in the London scientific elite to found a rival magnetic and meteorological observatory. Studying the origins of Airy’s Magnetic and Meteorological department highlights how important the context of other institutions and trends in science is to understanding the development of Britain’s national observatory. 相似文献
107.
Quay crane and yard truck scheduling are two important subproblems in container terminal operations which have been studied separately in previous research. This paper proposes a new problem for the integrated quay crane and yard truck scheduling for inbound containers. The problem is formulated as a mixed integer programming (MIP) model. Due to the intractability, a genetic algorithm (GA) and a modified Johnson's Rule-based heuristic algorithm (MJRHA) are used for the problem solution. In addition, two closed form lower bounds are given to evaluate the solution accuracy. Computational experiments show that the solution algorithm can efficiently handle the scheduling problem and that the integrated methods are very useful. 相似文献
108.
109.
Purdue MP Johansson M Zelenika D Toro JR Scelo G Moore LE Prokhortchouk E Wu X Kiemeney LA Gaborieau V Jacobs KB Chow WH Zaridze D Matveev V Lubinski J Trubicka J Szeszenia-Dabrowska N Lissowska J Rudnai P Fabianova E Bucur A Bencko V Foretova L Janout V Boffetta P Colt JS Davis FG Schwartz KL Banks RE Selby PJ Harnden P Berg CD Hsing AW Grubb RL Boeing H Vineis P Clavel-Chapelon F Palli D Tumino R Krogh V Panico S Duell EJ Quirós JR Sanchez MJ Navarro C Ardanaz E Dorronsoro M Khaw KT Allen NE 《Nature genetics》2011,43(1):60-65
110.
Wright FA Strug LJ Doshi VK Commander CW Blackman SM Sun L Berthiaume Y Cutler D Cojocaru A Collaco JM Corey M Dorfman R Goddard K Green D Kent JW Lange EM Lee S Li W Luo J Mayhew GM Naughton KM Pace RG Paré P Rommens JM Sandford A Stonebraker JR Sun W Taylor C Vanscoy LL Zou F Blangero J Zielenski J O'Neal WK Drumm ML Durie PR Knowles MR Cutting GR 《Nature genetics》2011,43(6):539-546
A combined genome-wide association and linkage study was used to identify loci causing variation in cystic fibrosis lung disease severity. We identified a significant association (P = 3.34 × 10(-8)) near EHF and APIP (chr11p13) in p.Phe508del homozygotes (n = 1,978). The association replicated in p.Phe508del homozygotes (P = 0.006) from a separate family based study (n = 557), with P = 1.49 × 10(-9) for the three-study joint meta-analysis. Linkage analysis of 486 sibling pairs from the family based study identified a significant quantitative trait locus on chromosome 20q13.2 (log(10) odds = 5.03). Our findings provide insight into the causes of variation in lung disease severity in cystic fibrosis and suggest new therapeutic targets for this life-limiting disorder. 相似文献