全文获取类型
收费全文 | 332篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 189篇 |
力学 | 11篇 |
数学 | 52篇 |
物理学 | 90篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 2篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 16篇 |
2011年 | 16篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 21篇 |
1995年 | 17篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1939年 | 2篇 |
1937年 | 1篇 |
1914年 | 1篇 |
1913年 | 1篇 |
1912年 | 1篇 |
1911年 | 2篇 |
1910年 | 1篇 |
1909年 | 1篇 |
1908年 | 2篇 |
1893年 | 1篇 |
1891年 | 1篇 |
1889年 | 1篇 |
排序方式: 共有342条查询结果,搜索用时 78 毫秒
61.
Asthma is a heterogeneous disorder and one of the most common chronic childhood diseases. An improved characterization of asthma phenotypes would be invaluable for the understanding of the pathogenic mechanisms and the correct treatment of this disease. The aim of this pilot study was to explore the potential of metabolomics applied to urine samples in characterizing asthma, and to identify the most representative metabolites. Urine samples of 41 atopic asthmatic children (further subdivided in sub-groups according to the symptoms) and 12 age-matched controls were analyzed. Untargeted metabolic profiles were collected by LC-MS, and studied by multivariate analysis. The group of the asthmatics was differentiated by a model that proved to be uncorrelated with the chronic assumption of controller drugs on the part of the patients. The distinct sub-groups were also appropriately modeled. Further investigations revealed a reduced excretion of urocanic acid, methyl-imidazoleacetic acid and a metabolite resembling the structure of an Ile-Pro fragment in the asthmatics. The meaning of these findings was discussed and mainly correlated with the modulation of immunity in asthma. Metabolic profiles from urines have revealed the potential to characterize asthma and enabled the identification of metabolites that may have a role in the underlying inflammation. 相似文献
62.
Laura Pisani Stefano Superchi Alessandra D’Elia Patrizia Scafato Carlo Rosini 《Tetrahedron》2012,68(29):5779-5784
A versatile and straightforward approach to optically active cis-4,5-disubstituted γ- and δ-lactones by catalytic enantioselective addition of dialkyzincs to cinnamic aldehydes and RCM ring closure has been reported. The synthetic importance of the enantioselective dialkylzinc alkylation of aldehydes has been thus widened. Such an approach has then been employed for the enantioselective synthesis of naturally occurring γ-lactone flavors like (S)-5-ethyl-butanolide (6a) and (4S,5S)-cis-whisky lactone (6b) and extended to the preparation of δ-lactones like (5S,6S)-5-methyl-6-ethylpentanolide (9a), precursor of the pheromone serricornin. 相似文献
63.
Summary Solid phase microextraction was coupled with gas chromatography-mass spectrometry (SPME-GC-MS) to screen for sixteen nitrogen-containing
compounds, including herbicides, in water samples. The effects of stirring, extraction time, pH, salt concentration and the
choice of fiber coating material were evaluated. The repeatability was in the range of 0.72–18.2 (CV % at 200 ng·L−1) and the reproducibility, in the range of 5.4–34 (at 500 ng·L−1). 相似文献
64.
65.
Ioannis Giannikos Elia El-Darzi Patrick Lees 《The Journal of the Operational Research Society》1995,46(6):713-720
This paper investigates the problem of allocating office space to members of staff in an academic institution. We identify several conflicting objectives and formulate an integer pre-emptive goal programming model to address them. Using data from a pilot site of the University of Westminster, UK, we then experiment with alternative rankings of the objectives. Finally, given the plans to consolidate the activities of this university into fewer sites and the resulting need to relocate some staff members, we discuss how this model can be used to ensure that this process is carried out with the least possible inconvenience. 相似文献
66.
67.
68.
Bartelt J Csorna SE Jain V Marka S Freyberger A Gibaut D Kinoshita K Pomianowski P Schrenk S Cinabro D Barish B Chadha M Chan S Eigen G Miller JS O'Grady C Schmidtler M Urheim J Weinstein AJ Würthwein F Asner DM Athanas M Bliss DW Brower WS Masek G Paar HP Gronberg J Korte CM Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Qiao C Richman JD Roberts D Ryd A Tajima H Witherell MS Balest R Cho K Ford WT Lohner M Park H Rankin P Roy J Smith JG Alexander JP Bebek C Berger BE 《Physical review letters》1996,76(22):4119-4123
69.
Abe K Abt I Ahn CJ Akagi T Allen NJ Ash WW Aston D Baird KG Baltay C Band HR Barakat MB Baranko G Bardon O Barklow T Bazarko AO Ben-David R Benvenuti AC Bienz T Bilei GM Bisello D Blaylock G Bogart JR Bolton T Bower GR Brau JE Breidenbach M Bugg WM Burke D Burnett TH Burrows PN Busza W Calcaterra A Caldwell DO Calloway D Camanzi B Carpinelli M Cassell R Castaldi R Castro A Cavalli-Sforza M Church E Cohn HO Coller JA Cook V Cotton R Cowan RF Coyne DG D'Oliveira A Damerell CJ Daoudi M 《Physical review D: Particles and fields》1996,53(3):1023-1038
70.
Gibaut D Kinoshita K Pomianowski P Barish B Chadha M Chan S Cowen DF Eigen G Miller JS O'Grady C Urheim J Weinstein AJ Würthwein F Asner DM Athanas M Bliss DW Brower WS Masek G Paar HP Gronberg J Korte CM Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Qiao C Richman JD Roberts D Ryd A Tajima H Witherell MS Balest R Cho K Ford WT Lohner M Park H Rankin P Smith JG Alexander JP Bebek C Berger BE Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Crowcroft DS Dickson M 《Physical review D: Particles and fields》1996,53(9):4734-4746