全文获取类型
收费全文 | 18358篇 |
免费 | 1626篇 |
国内免费 | 7篇 |
出版年
2022年 | 105篇 |
2021年 | 267篇 |
2020年 | 172篇 |
2019年 | 243篇 |
2018年 | 244篇 |
2017年 | 259篇 |
2016年 | 430篇 |
2015年 | 621篇 |
2014年 | 788篇 |
2013年 | 941篇 |
2012年 | 1165篇 |
2011年 | 1183篇 |
2010年 | 733篇 |
2009年 | 713篇 |
2008年 | 946篇 |
2007年 | 948篇 |
2006年 | 910篇 |
2005年 | 860篇 |
2004年 | 804篇 |
2003年 | 793篇 |
2002年 | 791篇 |
2001年 | 362篇 |
2000年 | 281篇 |
1999年 | 313篇 |
1998年 | 230篇 |
1997年 | 190篇 |
1996年 | 168篇 |
1995年 | 188篇 |
1994年 | 138篇 |
1993年 | 182篇 |
1992年 | 222篇 |
1991年 | 173篇 |
1990年 | 175篇 |
1989年 | 177篇 |
1988年 | 158篇 |
1987年 | 155篇 |
1986年 | 150篇 |
1985年 | 157篇 |
1984年 | 151篇 |
1983年 | 139篇 |
1982年 | 159篇 |
1981年 | 132篇 |
1980年 | 130篇 |
1979年 | 110篇 |
1978年 | 100篇 |
1977年 | 92篇 |
1975年 | 100篇 |
1974年 | 130篇 |
1973年 | 99篇 |
1972年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Ian H. Frasher Timothy Coolbear Sailen Mookerjea 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,799(2):102-105
Induction of inflammation by turpentine injection caused 1.5–2-fold increase of both sialy- and galactosyltransferase activity in liver homogenates. The effect was apparent after 12 h turpentine treatment. Serum sialytransferase activity started to increase in the inflamed rats after 18 h, reaching a maximum of 4-fold at 48 h. In contrast, galactosyltransferase activity in serum showed no significant increase. The coordinated and temporal increase of sialytransferase activity in liver and serum suggest involvement of a specific mechanism for the preferential release of this enzyme into serum. 相似文献
12.
13.
14.
E F Hill 《Journal of wildlife diseases》1988,24(1):51-61
Organophosphorus and carbamate pesticides are potent anticholinesterase substances that have killed large numbers of wild birds of various species. Cause of death is diagnosed by demonstration of depressed brain cholinesterase (ChE) activity in combination with chemical detection of anticholinesterase residue in the affected specimen. ChE depression is determined by comparison of the affected specimen to normal ChE activity for a sample of control specimens of the same species, but timely procurement of controls is not always possible. Therefore, a reference file of normal whole brain ChE activity is provided for 48 species of wild birds from North America representing 11 orders and 23 families for use as emergency substitutes in diagnosis of anticholinesterase poisoning. The ChE values, based on 83 sets of wild control specimens from across the United States, are reproducible provided the described procedures are duplicated. Overall, whole brain ChE activity varied nearly three-fold among the 48 species represented, but it was usually similar for closely related species. However, some species were statistically separable in most families and some species of the same genus differed as much as 50%. 相似文献
15.
16.
17.
18.
The Multiskan spectrophotometric system and Coomassie brilliant blue G-250 protein-dye binding method have been used together to measure NaOH-solubilized protein in subcellular membrane fractions prepared from isolated rat adipose cells. Forty-eight samples can be read in duplicate within 1 min. Sucrose in concentrations up to 0.7 m interfere only moderately with the assay. A rapid and convenient method is, therefore, now available for multiple protein determinations following sucellular fractionation on sucrose gradients. 相似文献
19.
Ian Hodder 《The journal of the Royal Anthropological Institute》2020,26(2):389-411
Over recent decades, many archaeologists have eschewed evolutionary theories, and in doing so they have turned away from the identification of long-term trends that are of great relevance to present-day matters of concern. In particular, there is clear evidence for an overall long-term increase in the amount of human-made material and associated human-thing entanglements, an increase tied up with environmental impact and global inequalities. The directionality of these long-term changes is clear and yet evolutionary theory largely shuns notions of overall directional change. This paradox and its implications are the subject of this article, with the suggestion made that, for human evolution at least, notions of directionality and path dependence need to be embraced, with concomitant changes in human evolutionary theory, and with implications for responses to environmental change. Adding to earlier accounts of entanglement, emphases are placed on the self-amplifying processes that lead to change and on irreversibility in the place of teleology. 相似文献
20.