全文获取类型
收费全文 | 2780篇 |
免费 | 187篇 |
出版年
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 66篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 93篇 |
2017年 | 68篇 |
2016年 | 111篇 |
2015年 | 151篇 |
2014年 | 172篇 |
2013年 | 216篇 |
2012年 | 224篇 |
2011年 | 200篇 |
2010年 | 159篇 |
2009年 | 118篇 |
2008年 | 158篇 |
2007年 | 152篇 |
2006年 | 155篇 |
2005年 | 116篇 |
2004年 | 108篇 |
2003年 | 87篇 |
2002年 | 78篇 |
2001年 | 29篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1977年 | 7篇 |
1976年 | 15篇 |
1974年 | 7篇 |
1969年 | 6篇 |
1968年 | 8篇 |
1964年 | 6篇 |
排序方式: 共有2967条查询结果,搜索用时 109 毫秒
1.
Patterns of Sleeping Site and Sleeping Tree Selection by Black-and-Gold Howler Monkeys (Alouatta caraya) in Northern Argentina 总被引:1,自引:0,他引:1
Brividoro Melina V. Kowalewski Martin M. Scarry Clara J. Oklander Luciana I. 《International journal of primatology》2019,40(3):374-392
International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body... 相似文献
2.
In the frog intestine, both in vitro and in vivo, experiments were carried out in order to increase knowledge of the mechanism of sugar exit across the basolateral membrane of the enterocyte. The frog intestine was chosen because it lacks crypt cells and, consequently, any external fluid circuit mechanism during sugar transport can be avoided. Therefore, the sugar concentration in the absorbate collected on the serosal side is likely to be similar to that present underneath the basolateral membrane of the enterocyte. Under this condition, cell and absorbate sugar concentrations are similar; yet there is a concomitant net transintestinal sugar transport. Moreover, in in vivo experiments a net transintestinal sugar transport takes place even against a concentration difference. These results suggest that sugar exit across the basolateral membrane is not simply due to a chemically facilitated diffusion. 相似文献
3.
4.
Michelle de C. S. Azevedo Patricia S. Rosa Cleverson T. Soares Luciana R. V. Fachin Ida Maria F. D. Baptista William J. Woods Gustavo P. Garlet Ana Paula F. Trombone Andrea de F. F. Belone 《PloS one》2015,10(12)
Jorge Lobo’s disease (JLD) is a chronic infection that affects the skin and subcutaneous tissues. Its etiologic agent is the fungus Lacazia loboi. Lesions are classified as localized, multifocal, or disseminated, depending on their location. Early diagnosis and the surgical removal of lesions are the best therapeutic options currently available for JLD. The few studies that evaluate the immunological response of JLD patients show a predominance of Th2 response, as well as a high frequency of TGF-β and IL-10 positive cells in the lesions; however, the overall immunological status of the lesions in terms of their T cell phenotype has yet to be determined. Therefore, the objective of this study was to evaluate the pattern of Th1, Th2, Th17 and regulatory T cell (Treg) markers mRNA in JLD patients by means of real-time PCR. Biopsies of JLD lesions (N = 102) were classified according to their clinical and histopathological features and then analyzed using real-time PCR in order to determine the expression levels of TGF-β1, FoxP3, CTLA4, IKZF2, IL-10, T-bet, IFN-γ, GATA3, IL-4, IL-5, IL-13, IL-33, RORC, IL-17A, IL-17F, and IL-22 and to compare these levels to those of healthy control skin (N = 12). The results showed an increased expression of FoxP3, CTLA4, TGF-β1, IL-10, T-bet, IL-17F, and IL-17A in lesions, while GATA3 and IL-4 levels were found to be lower in diseased skin than in the control group. When the clinical forms were compared, TGF-β1 was found to be highly expressed in patients with a single localized lesion while IL-5 and IL-17A levels were higher in patients with multiple/disseminated lesions. These results demonstrate the occurrence of mixed T helper responses and suggest the dominance of regulatory T cell activity, which could inhibit Th-dependent protective responses to intracellular fungi such as L. loboi. Therefore, Tregs may play a key role in JLD pathogenesis. 相似文献
5.
A 1H NMR study of the peptide alamethicin, which forms voltage-gated ion channels in membranes, is described. The molecule was studied in methanol as a function of temperature and pH. A complete assignment of the spectra is given, including several stereospecific assignments. Alamethicin was found to have a structure substantially similar to the crystal although, in solution, the C-terminal dipeptide adopts a somewhat extended conformation. The overall conformation was insensitive to the ionization of the side chain of the only ionizable group, Glu-18. 相似文献
6.
Luciana Mastrantuono 《Aquatic Ecology》1988,22(2):195-198
The analysis of gut contents ofAmphichaeta leydigii, found for the first time in Italy in sandy shores of Lake Vico (Central Italy), proved grazing of the species on diatoms (Centrales and Pennales). Detritus and organic particles, abundant in the substratum, were observed only in small amounts. 相似文献
7.
8.
M Fekadu J H Shaddock J W Sumner D W Sanderlin J C Knight J J Esposito G M Baer 《Journal of wildlife diseases》1991,27(4):681-684
Twenty nine skunks (Mephitis mephitis) were vaccinated orally with raccoon poxvirus (RCN) recombinants: 10 with a recombinant expressing the rabies virus glycoprotein (RCNRG), 10 with RCNRG mixed with a recombinant expressing the rabies virus nucleoprotein (RCNRN) and nine with RCN alone. Rabies virus neutralizing antibodies were detected in six of the 20 skunks; five skunks (three given RCNRG, two given a mixture of recombinants) survived a rabies challenge that was lethal for nine skunks vaccinated with RCN alone. 相似文献
9.
10.
Substance P as a transglutaminase substrate: identification of the reaction products by fast atom bombardment mass spectrometry 总被引:1,自引:0,他引:1
R Porta C Esposito S Metafora P Pucci A Malorni G Marino 《Analytical biochemistry》1988,172(2):499-503
Substance P was found to be an effective acyl donor substrate of transglutaminase in vitro, the reaction products having been examined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fast atom bombardment mass spectrometry. Electrophoretic experiments showed that Substance P incorporated 14C-labeled polyamines when incubated with purified guinea pig liver transglutaminase and Ca2+. Extensive use of fast atom bombardment mass spectrometry allowed to establish that: i) a 1:1 adduct Substance P-spermine is formed; ii) only a single glutamine residue out of two, i.e. Gln-5, acts as acyl donor, iii) the single lysine residue of the neuropeptide is unable to act as acyl acceptor. A direct analytical methodology to detect transglutaminase reaction products is described. 相似文献