全文获取类型
收费全文 | 1017篇 |
免费 | 99篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 14篇 |
2019年 | 19篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 32篇 |
2015年 | 64篇 |
2014年 | 68篇 |
2013年 | 79篇 |
2012年 | 89篇 |
2011年 | 61篇 |
2010年 | 35篇 |
2009年 | 47篇 |
2008年 | 55篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 54篇 |
2004年 | 45篇 |
2003年 | 38篇 |
2002年 | 53篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 4篇 |
1967年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1116条查询结果,搜索用时 93 毫秒
11.
12.
Isolation and Characterization of a Cytosolic Phospholipase A2 from Bovine Adrenal Medulla 总被引:1,自引:1,他引:0
Abstract: We have recently demonstrated that bovine adrenal medulla contains a soluble phospholipase A2 (PLA2 ), which is localized in the cytosol. In the present study, this PLA2 was purified 1,097-fold using sequential concanavalin A, hydrophobic interaction, anion exchange, gel filtration, and an additional anion exchange chromatography. The enzyme is activated over the range of 20–1,000 µ M Ca2+ and has a pH optimum near 8.0. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protein has a molecular mass of 26 kDa and an isoelectric point of 4.6 as revealed by isoelectric focusing. The cytosolic PLA2 is not inhibited by NaCl, and the enzymatic activity is stimulated at low concentrations of Triton X-100 (0.01%) and deoxycholate (1 m M ) but inhibited at higher concentrations (0.1% and 3 m M , respectively) of these detergents. Furthermore, heat treatment (57°C, 5 min) reduced the enzymatic activity by 80%, whereas glycerol (30%) increased the activity. p -Bromophenacylbromide, a frequently used irreversible inhibitor of type II PLA2 , has little effect until 100 µ M , and 2–10 m M dithiothreitol totally inactivated the enzyme. The purified PLA2 displays a preference for phosphatidylcholine as a substrate but hydrolyzes phospholipid substrates with arachidonic acid or linoleic acid esterified at the sn -2 position to the same extent. It is concluded that the chromaffin cell cytosolic PLA2 , which was isolated and characterized in this study, represents a type of PLA2 that has not been formerly reported in chromaffin cells. Additional research on the chromaffin cell cytosolic PLA2 will help to reveal whether the enzyme is important for exocytosis. 相似文献
13.
A Van Aerschot J Rozenski D Loakes N Pillet G Schepers P Herdewijn 《Nucleic acids research》1995,23(21):4363-4370
Acyclic nucleoside analogues with carboxamido- or nitro-substituted heterocyclic bases have been evaluated for their possible use as universal bases in oligodeoxynucleotides. The acyclic moiety endows the constructs with enough flexibility to allow good base stacking. The 5-nitroindazole analogue afforded the most stable duplexes among the acyclic derivatives with the least spread in Tm versus the four natural bases. In spite of the acyclic moiety, stabilities are comparable with those of duplexes incorporating the recently described 5-nitroindole nucleoside analogue, but considerably exceed those for the 3-nitropyrrole analogue. 相似文献
14.
Marianne Borloo Koen Augustyns Alexander Belyaev Ingrid de Meester Anne-Marie Lambeir Filip Goossens Willy Bollaert Padinchare Rajan Simon Scharpé Achiel Haemers 《Letters in Peptide Science》1995,2(3-4):198-202
Summary A series of azaproline dipeptides with various N-substituents were synthesized as possible active-site-directed inhibitors of two proline-specific serine proteases, dipeptidyl peptidase IV and prolyl oligopeptidase. Compounds with semicarbazide, carbazate, acylhydrazine and sulphonylhydrazine structures were tested. Some compounds show moderate activity, i.e., in the millimolar range. 相似文献
15.
Mesoplodon peruvianus , a new species of beaked whale, is described on the basis of ten specimens which have either stranded or been captured between 11°12'S and 15°19'S latitude along the coasts of the provinces of Lima and Ica, south central Peru. This is the thirteenth living species of Mesoplodon recognized in the world's oceans. The animals that were examined were uniformly gray above, shading to lighter gray below. This whale is the smallest species of Mesoplodon (maximum body length 3.72 m) and is characterized by its teeth, which are small (31 to 65 mm long), ovate in cross section, and positioned 2.5% to 8.4% of the mandibular length from the anterior extremity, and posterior to the mandibular symphysis. 相似文献
16.
17.
18.
Daniele Novarina Georges E. Janssens Koen Bokern Tim Schut Noor C. van Oerle Hinke G. Kazemier Liesbeth M. Veenhoff Michael Chang 《Aging cell》2020,19(2)
To ensure proper transmission of genetic information, cells need to preserve and faithfully replicate their genome, and failure to do so leads to genome instability, a hallmark of both cancer and aging. Defects in genes involved in guarding genome stability cause several human progeroid syndromes, and an age‐dependent accumulation of mutations has been observed in different organisms, from yeast to mammals. However, it is unclear whether the spontaneous mutation rate changes during aging and whether specific pathways are important for genome maintenance in old cells. We developed a high‐throughput replica‐pinning approach to screen for genes important to suppress the accumulation of spontaneous mutations during yeast replicative aging. We found 13 known mutation suppression genes, and 31 genes that had no previous link to spontaneous mutagenesis, and all acted independently of age. Importantly, we identified PEX19, encoding an evolutionarily conserved peroxisome biogenesis factor, as an age‐specific mutation suppression gene. While wild‐type and pex19Δ young cells have similar spontaneous mutation rates, aged cells lacking PEX19 display an elevated mutation rate. This finding suggests that functional peroxisomes may be important to preserve genome integrity specifically in old cells. 相似文献
19.
Ilse Van Gucht Josephina A.N. Meester Jotte Rodrigues Bento Maaike Bastiaansen Jarl Bastianen Ilse Luyckx Lotte Van Den Heuvel Cédric H.G. Neutel Pieter-Jan Guns Mandy Vermont Erik Fransen Melanie H.A.M. Perik Joe Davis Velchev Maaike Alaerts Dorien Schepers Silke Peeters Isabel Pintelon Abdulrahman Almesned Aline Verstraeten 《American journal of human genetics》2021,108(6):1115-1125
20.
Ecosystems - Intertidal ecosystems are important because of their function as coastal protection and ecological value. Sea level rise may lead to submergence of salt marshes worldwide. Salt marshes... 相似文献