全文获取类型
收费全文 | 135995篇 |
免费 | 4973篇 |
国内免费 | 894篇 |
专业分类
141862篇 |
出版年
2022年 | 339篇 |
2021年 | 576篇 |
2020年 | 378篇 |
2019年 | 466篇 |
2018年 | 12260篇 |
2017年 | 11081篇 |
2016年 | 8303篇 |
2015年 | 2340篇 |
2014年 | 1990篇 |
2013年 | 2539篇 |
2012年 | 6733篇 |
2011年 | 14990篇 |
2010年 | 13414篇 |
2009年 | 9560篇 |
2008年 | 11612篇 |
2007年 | 13113篇 |
2006年 | 2010篇 |
2005年 | 2198篇 |
2004年 | 2534篇 |
2003年 | 2425篇 |
2002年 | 2171篇 |
2001年 | 1545篇 |
2000年 | 1478篇 |
1999年 | 1225篇 |
1998年 | 663篇 |
1997年 | 631篇 |
1996年 | 613篇 |
1995年 | 591篇 |
1994年 | 549篇 |
1993年 | 595篇 |
1992年 | 1099篇 |
1991年 | 865篇 |
1990年 | 849篇 |
1989年 | 839篇 |
1988年 | 748篇 |
1987年 | 680篇 |
1986年 | 664篇 |
1985年 | 766篇 |
1984年 | 580篇 |
1983年 | 475篇 |
1982年 | 370篇 |
1981年 | 348篇 |
1980年 | 277篇 |
1979年 | 421篇 |
1978年 | 367篇 |
1977年 | 261篇 |
1974年 | 317篇 |
1973年 | 281篇 |
1972年 | 449篇 |
1971年 | 439篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
Background
Recent studies point to a great diversity of non-ribosomal peptide synthesis systems with major roles in amino acid and co-factor biosynthesis, secondary metabolism, and post-translational modifications of proteins by peptide tags. The least studied of these systems are those utilizing tRNAs or aminoacyl-tRNA synthetases (AAtRS) in non-ribosomal peptide ligation. 相似文献14.
Prediction of sequential antigenic regions in proteins 总被引:30,自引:0,他引:30
Prediction of antigenic regions in a protein will be helpful for a rational approach to the synthesis of peptides which may elicit antibodies reactive with the intact protein. Earlier methods are based on the assumption that antigenic regions are primarily hydrophilic regions at the surface of the protein molecule. The method presented here is based on the amino acid composition of known antigenic regions in 20 proteins which is compared with that of 314 proteins [(1978) Atlas of Protein Sequence and Structure, vol. 5, suppl. 3, 363-373]. Antigenicity values were derived from the differences between the two data sets. The method was applied to bovine ribonuclease, the B-subunit of cholera toxin and herpes simplex virus type 1 glycoprotein D. There was a good correlation between the predicted regions and previously determined antigenic regions. 相似文献
15.
16.
17.
18.
Background
Substituted catechols are important precursors for large-scale synthesis of pharmaceuticals and other industrial products. Most of the reported chemical synthesis methods are expensive and insufficient at industrial level. However, biological processes for production of substituted catechols could be highly selective and suitable for industrial purposes. 相似文献19.
Leucostasis, an underestimated cause of death in leukaemia 总被引:1,自引:0,他引:1
Massive sludging of leukaemic cells in blood vessels is a frequent and often lethal complication of leukaemia. In a retrospective clinicopathological study on the causes of death in 52 patients with acute myeloid leukaemia and myeloproliferative disease, pulmonary leucostasis was found in 40% of the patients. In many of these patients the vessels of the heart, brain and testes were also involved. In search for signs and symptoms specific for leucostasis, the clinical records of the 21 patients with leucostasis (the study group) were compared to those of 20 patients without leucostasis (the control group). Dysfunction of the organs most affected by leucostasis, namely lungs, heart and brain, was found more often in the study group than in the controls, but the combination of unexplained fever with cardiopulmonary and/or central nervous system failure occurred almost exclusively and in half of the patients with leucostasis. Leucostasis occurs predominantly, but not exclusively, in patients with high leucocyte counts, and especially, but again not exclusively, when the leucocyte counts rise sharply. 相似文献
20.