全文获取类型
收费全文 | 2103篇 |
免费 | 162篇 |
出版年
2022年 | 15篇 |
2021年 | 34篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 42篇 |
2017年 | 23篇 |
2016年 | 46篇 |
2015年 | 92篇 |
2014年 | 97篇 |
2013年 | 112篇 |
2012年 | 154篇 |
2011年 | 140篇 |
2010年 | 91篇 |
2009年 | 63篇 |
2008年 | 105篇 |
2007年 | 101篇 |
2006年 | 83篇 |
2005年 | 89篇 |
2004年 | 113篇 |
2003年 | 103篇 |
2002年 | 88篇 |
2001年 | 30篇 |
2000年 | 15篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 22篇 |
1992年 | 32篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 19篇 |
1974年 | 13篇 |
1973年 | 10篇 |
1972年 | 8篇 |
排序方式: 共有2265条查询结果,搜索用时 46 毫秒
231.
Chesworth R Wessel MD Heyden L Mangano FM Zawistoski M Gegnas L Galluzzo D Lefker B Cameron KO Tickner J Lu B Castleberry TA Petersen DN Brault A Perry P Ng O Owen TA Pan L Ke HZ Brown TA Thompson DD DaSilva-Jardine P 《Bioorganic & medicinal chemistry letters》2005,15(24):5562-5566
A series of ligands with varying heterocyclic cores and substituents that display a range of selectivity’s (up to >100x) for ER-β over ER- are reported. 相似文献
232.
Razafimahefa D Ralambomanana DA Hammouche L Pélinski L Lauvagie S Bebear C Brocard J Maugein J 《Bioorganic & medicinal chemistry letters》2005,15(9):2301-2303
A new series of ferrocenyl diamino alcohols and diamines were synthesized and their inhibitory potencies were probed with Mycobacterium tuberculosis. Interestingly, ferrocenyl diamines 6a and b display significant activities against M. tuberculosis H37Rv. 相似文献
233.
Five-atomic tri(hetero)halogenomethanes represent the simplest class of non-isotopic small chiral molecules suitable for the study of fundamental aspects of chirality. The analytical gas-chromatographic separation of the enantiomers of bromochlorofluoromethane 1 and of chlorofluoroiodomethane 2 on the immobilized chiral stationary phase octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-gamma-cyclodextrin 3, chemically linked to polydimethylsiloxane, is described. By temperature-dependent thermodynamic measurements very low isoenantioselective temperatures T(iso) are found and for optimum enantiomeric separations cryogenic temperatures are required. The ee values of enantiomerically enriched tri(hetero)halogenomethanes 1 and 2 are determined and relative configurations are correlated with the chromatographic elution order of 1 and 2 on 3. 相似文献
234.
Miguel Quintana Peter Lindell Samir K Saha Francesca del Furia Britta Lind Satish Govind Lars-Åke Brodin 《Cardiovascular ultrasound》2005,3(1):1-12
Background
Myocardial contrast echocardiography and coronary flow velocity pattern with a rapid diastolic deceleration time after percutaneous coronary intervention has been reported to be useful in assessing microvascular damage in patients with acute myocardial infarction.Aim
To evaluate myocardial contrast echocardiography with harmonic power Doppler imaging, coronary flow velocity reserve and coronary artery flow pattern in predicting functional recovery by using transthoracic echocardiography.Methods
Thirty patients with anterior acute myocardial infarction underwent myocardial contrast echocardiography at rest and during hyperemia and were quantitatively analyzed by the peak color pixel intensity ratio of the risk area to the control area (PIR). Coronary flow pattern was measured using transthoracic echocardiography in the distal portion of left anterior descending artery within 24 hours after recanalization and we assessed deceleration time of diastolic flow velocity. Coronary flow velocity reserve was calculated two weeks after acute myocardial infarction. Left ventricular end-diastolic volumes and ejection fraction by angiography were computed.Results
Pts were divided into 2 groups according to the deceleration time of coronary artery flow pattern (Group A; 20 pts with deceleration time ≧ 600 msec, Group B; 10 pts with deceleration time < 600 msec). In acute phase, there were no significant differences in left ventricular end-diastolic volume and ejection fraction (Left ventricular end-diastolic volume 112 ± 33 vs. 146 ± 38 ml, ejection fraction 50 ± 7 vs. 45 ± 9 %; group A vs. B). However, left ventricular end-diastolic volume in Group B was significantly larger than that in Group A (192 ± 39 vs. 114 ± 30 ml, p < 0.01), and ejection fraction in Group B was significantly lower than that in Group A (39 ± 9 vs. 52 ± 7%, p < 0.01) at 6 months. PIR and coronary flow velocity reserve of Group A were higher than Group B (PIR, at rest: 0.668 ± 0.178 vs. 0.248 ± 0.015, p < 0.0001: during hyperemia 0.725 ± 0.194 vs. 0.295 ± 0.107, p < 0.0001; coronary flow velocity reserve, 2.60 ± 0.80 vs. 1.31 ± 0.29, p = 0.0002, respectively).Conclusion
The preserved microvasculature detecting by myocardial contrast echocardiography and coronary flow velocity reserve is related to functional recovery after acute myocardial infarction. 相似文献235.
Young JE Christian KA Donnellan S Tracy CR Parry D 《Physiological and biochemical zoology : PBZ》2005,78(5):847-856
Most frog species show little resistance to evaporative water loss (EWL), but some arboreal species are known to have very high resistances. We measured EWL and cutaneous resistance to evaporation (Rc) in 25 species of frogs from northern Australia, including 17 species in the family Hylidae, six species in the Myobatrachidae, and one each in the Bufonidae and the Microhylidae. These species display a variety of ecological habits, including aquatic, terrestrial, and arboreal specialisations, with the complete range of habits displayed within just the one hylid genus, Litoria. The 25 species measured in this study have resistances that range from Rc=0 to 63.1. These include low values indistinguishable from a free water surface to high values typical of "waterproof" anuran species. There was a strong correlation between ecological habit and Rc, even taking phylogenetic relationships into account; arboreal species had the highest resistance, aquatic species tended to have little or no resistance, and terrestrial species tended to have resistance between those of arboreal and aquatic frogs. For one species, Litoria rubella, we found no significant changes in EWL along a 1,500-km aridity gradient. This study represents the strongest evidence to date of a link between ecological habits and cutaneous resistance to water loss among species of frogs. 相似文献
236.
237.
238.
daSilva LL de Molfetta-Machado JB Panunto-Castelo A Denecke J Goldman GH Roque-Barreira MC Goldman MH 《Biochimica et biophysica acta》2005,1726(3):251-260
KM+, a mannose-binding lectin present in the seeds of Artocarpus integrifolia, has interesting biological properties and potential pharmaceutical use [A. Panunto-Castelo, M.A. Souza, M.C. Roque-Barreira, J.S. Silva, KM(+), a lectin from Artocarpus integrifolia, induces IL-12 p40 production by macrophages and switches from type 2 to type 1 cell-mediated immunity against Leishmania major antigens, resulting in BALB/c mice resistance to infection, Glycobiology 11 (2001) 1035-1042. ; L.L.P. daSilva, A. Panunto-Castelo, M.H.S. Goldman, M.C. Roque-Barreira, R.S. Oliveira, M.D. Baruffi, J.B. Molfetta-Machado, Composition for preventing or treating appearance of epithelia wounds such as skin and corneal wounds or for immunomodulating, comprises lectin, Patent number WO20041008.]. Here, we have isolated clones encoding the full-length KM+ primary sequence from a cDNA library, through matrix PCR-based screening methodology. Analysis of KM+ nucleotide and deduced amino acid sequences provided strong evidence that it neither enters the secretory pathway nor undergoes post-translational modifications, which is in sharp contrast with jacalin, the more abundant lectin from A. integrifolia seeds. Current investigations into the KM+ properties are often impaired by the difficulty in obtaining sufficient quantities of jacalin-free KM+ through direct seed extraction. To obtain active recombinant protein (rKM+) in larger amounts, we tested three different expression systems. Expression vectors were constructed to produce: (a) rKM+ in E. coli in its native form, (b) rKM+ with GST as an N-terminal tag and (c) native rKM+ in Saccharomyces cerevisiae. The presence of the GST-tag significantly improved the overall rKM+ yield; however, most of the obtained rGST-KM+ was insoluble. Production of rKM+ in the yeast host yielded the highest quantities of soluble lectin that retained the typical high-mannose oligosaccharide-binding properties of the natural protein. The possible biotechnological applications of recombinant KM+ are discussed. 相似文献
239.
Witasp E Gustafsson AC Cotgreave I Lind M Fadeel B 《Biochemical and biophysical research communications》2005,330(3):891-897
Previous studies have suggested that 1,25(OH)2D3, the active form of vitamin D3, may increase the survival of bone-forming osteoblasts through an inhibition of apoptosis. On the other hand, vitamin D3 has also been shown to trigger apoptosis in human cancer cells, including osteosarcoma-derived cell lines. In the present study, we show that 1,25(OH)2D3 induces a time- and dose-dependent loss of cell viability in the rat osteosarcoma cell line, UMR-106, and the human osteosarcoma cell line, TE-85. We were unable, however, to detect nuclear condensation, phosphatidylserine externalization, or other typical signs of apoptosis in this model. Moreover, 1,25(OH)2D3 failed to protect against apoptosis induced by serum starvation or incubation with the protein kinase inhibitor, staurosporine. These in vitro findings are thus at variance with several previous reports in the literature and suggest that induction of or protection against apoptosis of bone-derived cells may not be a primary function of vitamin D3. 相似文献
240.
In a family of clonal lines derived from the Reuber H 35 rat hepatoma, four electrophoretically distinct molecular forms of uridine kinase (UK I, II, III, and IV) have been characterized. They are the same as those found in foetal rat liver. Different UK profiles occur in these cell lines, and no strict correlation could be established between the state of differentiation of the cells and the form of UK expressed. A clone of somatic hybrid cells between line p4 (form 1 only) and Fu5-5 (forms II, III, and IV) that does not express form I indicates that p4 cells may lack a factor controlling the polymerization of form I. This variety of clonal cell lines was used to study the uptake and phosphorylation of labeled uridine. The results suggest a relationship between the UK form present and the rate uridine phosphorylation by the intact cells. 相似文献