全文获取类型
收费全文 | 889篇 |
免费 | 85篇 |
出版年
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 26篇 |
2014年 | 24篇 |
2013年 | 24篇 |
2012年 | 24篇 |
2011年 | 39篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 41篇 |
2007年 | 41篇 |
2006年 | 19篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 24篇 |
2002年 | 31篇 |
2001年 | 29篇 |
2000年 | 33篇 |
1999年 | 24篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1992年 | 22篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1974年 | 18篇 |
1973年 | 20篇 |
1972年 | 14篇 |
1971年 | 5篇 |
1969年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有974条查询结果,搜索用时 493 毫秒
141.
The incidence of aspirin ingestion during the week preceding overt gastroduodenal bleeding was recorded in 582 patients. A positive aspirin history was found in 80% of patients with acute gastric lesions, in 63% of those in whom no lesion was found, in 52% of those with a chronic duodenal ulcer, and in 49% of patients with a chronic gastric ulcer. In a control series of 542 consecutive patients without overt bleeding admitted to the same wards during part of the time of this investigation the aspirin incidence was 32%.The difference in aspirin habits between these two series confirms that aspirin is a factor in precipitating overt haemorrhage in acute and chronic peptic ulcers, and that it is an important cause of bleeding from the stomach or duodenum, or both, in the absence of a chronic peptic ulcer. 相似文献
142.
143.
144.
145.
Ana E. Carmo-Silva Alfred J. Keys Jane L. Ward Nathaniel D. Hawkins Martin A.J. Parry 《Phytochemistry》2009,70(5):664-671
Plants produce various compounds in response to water deficit. Here, the presence and identification of a drought-inducible non-protein amino acid in the leaves of two C4 grasses is first reported. The soluble amino acids extracted from the leaves of three different species were measured by high-performance liquid chromatography of derivatives formed with o-phthaldialdehyde and β-mercaptoethanol. One amino acid that increased in amount with drought stress had a retention time not corresponding to any common amino acid. Its identity was determined by metabolite profiling, using 1H NMR and GC-MS. This unusual amino acid was present in the dehydrated leaves of Cynodon dactylon (L.) Pers. and Zoysia japonica Steudel, but was absent from Paspalum dilatatum Poir. Its identity as 2-amino-5-hydroxypentanoic acid (5-hydroxynorvaline, 5-HNV) was confirmed by synthesis and co-chromatography of synthetic and naturally occurring compounds. The amount of 5-HNV in leaves of the more drought tolerant C4 grasses, C. dactylon and Z. japonica, increased with increasing water deficit; therefore, any benefits from this unusual non-protein amino acid for drought resistance should be further explored. 相似文献
146.
Matthew W. Kemp Ben Edwards Matthew Burgess W. Thomas Clarke George Nicholson David A.D. Parry Kay E. Davies 《Journal of structural biology》2009,165(3):196-203
Syncoilin is a 64 kDa intermediate filament (IF) protein expressed in myocytes at the sarcolemma, perinucleus, myotendenous and neuromuscular junctions. Here we present a revised domain projection and structural analysis for the original isoform (sync-1) and introduce two novel syncoilin isoforms (sync-2 and sync-3) generated by exon splicing. On the basis of consensus identity we propose that syncoilin be reclassified as a type III IF protein. All three syncoilin isoforms lack a L1 domain, a significant departure from standard IF rod domain projections that is likely to impact significantly on their biological function. Our analyses indicate that syncoilin is unlikely to form classical intermediate filament structures by itself, and that the significant difference in C-terminal structure between the three isoforms indicates that they may play divergent roles in myocytes. We show that despite lacking an apparent structural role in striated muscle, syncoilin isoforms are differentially and strongly upregulated in response to cardiotoxin induced regeneration and denervation induced atrophy in the C57BL/6 mouse, possibly suggesting an atypical role for syncoilin in muscle. 相似文献
147.
Styers TJ Kekec A Rodriguez R Brown JD Cajica J Pan PS Parry E Carroll CL Medina I Corral R Lapera S Otrubova K Pan CM McGuire KL McAlpine SR 《Bioorganic & medicinal chemistry》2006,14(16):5625-5631
We report the synthesis of thirty-six Sansalvamide A derivatives, and their biological activity against colon cancer HT-29 cell line, a microsatellite stable (MSS) colon cancer cell-line. The thirty-six compounds can be divided into three subsets, where the first subset of compounds contains L-amino acids, the second subset contains D-amino acids, and the third subset contains both D- and L-amino acids. Five compounds exhibited excellent inhibitory activity (>75% inhibition). The structure-activity relationship (SAR) of the compounds established that a single D-amino acid in position 2 or 3 gave up to a 10-fold improved cytotoxicity over Sansalvamide A peptide. This work highlights the importance of residues 2 and 3 and the role of D-amino acids in the extraordinary SAR for this compound class. 相似文献
148.
M J Slater S Cockerill R Baxter R W Bonser K Gohil C Gowrie J E Robinson E Littler N Parry R Randall W Snowden 《Bioorganic & medicinal chemistry》1999,7(6):1067-1074
In our search for new, safer anti-HCMV agents, we discovered that the natural product Arcyriaflavin A (la) was a potent inhibitor of HCMV replication in cell culture. A series of analogues (symmetrical indolocarbazoles) was synthesised to investigate structure activity relationships in this series against a range of herpes viruses (HCMV, VZV, HSV1, and 2). This identified a number of novel, selective and potent inhibitors of HCMV, 12,13-dihydro-2,10-difluoro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazol e-5,7-(6H)-dione (1d) being the best example (IC50=40 nM, therapeutic index > 1450). Compounds described in this series were generally poor inhibitors of protein kinase C betaII, and no correlation was found between the ability to inhibit HCMV and the enzyme PKC. 相似文献
149.
Introduction Most crops were first domesticated about 13 000 to 11 000 years ago.Humans are dependent on crops for survival,and from the beginnings of agriculture have been energetically involved in developing crops that better serve their needs 相似文献
150.
Gregory D. Parry 《Biological invasions》2017,19(7):2185-2196
Asterias amurensis is a starfish native to the northern Pacific that was introduced into southern Australia in the 1980s. It is widely viewed as one of Australia’s most serious invasive marine pests, but there are few methods available to control new or established populations. The role of Coscinasterias muricata in controlling the distribution of Asterias in Port Phillip Bay, and its potential to eliminate new infestations of Asterias were investigated. Laboratory feeding trials, where alternative mussel prey were available, showed Coscinasterias consumed Asterias at the rate of ~45/year. Field surveys in Port Phillip Bay showed that most Coscinasterias occurred at depths shallower than 15 m, while most Asterias occurred at depths greater than 15 m, and the ratio of Asterias/Coscinasterias only exceeded 45 at depths greater than 15 m. Consequently, if laboratory and field feeding rates are similar, Coscinasterias would be expected to exert significant control over Asterias populations at depths shallower than 15 m, and augmenting Coscinasterias populations at sites of new Asterias infestations may help eliminate newly-established populations. 相似文献