全文获取类型
收费全文 | 5549篇 |
免费 | 478篇 |
国内免费 | 4篇 |
出版年
2023年 | 26篇 |
2022年 | 75篇 |
2021年 | 132篇 |
2020年 | 58篇 |
2019年 | 72篇 |
2018年 | 94篇 |
2017年 | 78篇 |
2016年 | 140篇 |
2015年 | 221篇 |
2014年 | 231篇 |
2013年 | 287篇 |
2012年 | 405篇 |
2011年 | 321篇 |
2010年 | 220篇 |
2009年 | 181篇 |
2008年 | 293篇 |
2007年 | 293篇 |
2006年 | 254篇 |
2005年 | 227篇 |
2004年 | 226篇 |
2003年 | 183篇 |
2002年 | 169篇 |
2001年 | 184篇 |
2000年 | 162篇 |
1999年 | 129篇 |
1998年 | 52篇 |
1997年 | 44篇 |
1996年 | 28篇 |
1995年 | 38篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 92篇 |
1991年 | 77篇 |
1990年 | 80篇 |
1989年 | 84篇 |
1988年 | 61篇 |
1987年 | 62篇 |
1986年 | 68篇 |
1985年 | 68篇 |
1984年 | 54篇 |
1983年 | 49篇 |
1982年 | 40篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 42篇 |
1978年 | 31篇 |
1976年 | 27篇 |
1975年 | 27篇 |
1974年 | 34篇 |
1973年 | 36篇 |
排序方式: 共有6031条查询结果,搜索用时 296 毫秒
81.
82.
83.
The predictability of leucocyte typing in kidney transplantation was assessed by an analysis of 37 kidney transplants from sibling donors. Recipients who were identical for the HL-A antigens with their donors gave highly predictable results. In comparison with those siblings who were incompatible or compatible but not identical their grafts functioned earlier, they required less immunosuppression, and had never had any rejections. They also appeared to have less postoperative morbidity. These results indicate that less immunosuppression than is current in many transplant centres could well be used with benefit in HL-A identical sibling transplants. This could reduce the risk of infection and possibly minimize the adverse effects of steroids on wound healing in these patients. 相似文献
84.
Coleoptile and root tips ofTriticum aestivum cv. Arnej 624 and those ofAvena sativa cv. Victory (Svalöf) as well as dry excised embryos ofTriticum aestivum cv. Rival (Svalöf) and those ofArachis hypogaea cv. 34 3A. H. were cultivated in media containing various concentrations of sucrose and growth regulators, like ascorbic acid, indole-3-acetic acid and gibberellin. Growth, differentiation and water uptake of the various explants were determined at regular time intervals. Further, the concentration of the endogenous ascorbic acid in mg./g. fresh weight, as well as the amount of this growth regulator utilized as per cent of the total were determined. Although all the three growth regulators promote growth in the explants, their effect is best felt when sucrose of a higher concentration (1.0 per cent) is added to the medium. In fact, the response to 1.0 per cent sucrose is sometimes as good as a combination of a growth regulator with sucrose, especially in the case of root explants. The results clearly indicate that the biosynthesis of ascorbic acid in the explants is catalyzed by the addition of indole-3-acetic acid as well as gibberellin. Simultaneously, the utilization of ascorbic acid is also appreciably increased by the presence of these growth regulators. Addition of 1.0 per cent sucrose to the medium containing the above mentioned growth regulators augments to a considerable extent not only the concentration of ascorbic acid, but also steps up its utilization. Enhancement of ascorbic acid as well as its increased utilization are correlated with rapid imbibition of water, growth and differentiation. The role of ascorbic acid in growth is discussed; and on the basis of the data presented here it is postulated that: (1) auxin and gibberellin function in the growth process by catalyzing the biosynthesis of ascorbic acid; and (2) that ascorbic acid not only participates in activation of various enzyme systems, but also stimulates the production of adenosine triphosphate by acting as an electron donor in photosynthetic phosphorylation as well as oxidative phosphorylation; (3) that the above action of ascorbic acid creates a favourable redox balance for synthesis of nucleic acids, proteins, enzymeproteins, and cell-wall constituents, thus enabling the processes of cell division and enlargement to proceed at a fast rate; and (4) that the relative rates of cell division and cell enlargement as well as “ageing” will determine the pattern of plant development. 相似文献
85.
86.
87.
88.
Csillag A. Bourne R. C. Patel Sanjay N. Stewart Michael G. Tömböl Teréz 《Brain Cell Biology》1989,18(3):369-379
Brain Cell Biology - The distribution of GABA-like immunoreactivity (GABA-LI) in the ectostriatal core (Ec) of domestic chicks (one to two days old) was investigated using (1) preembedding GABA... 相似文献
89.
Z Yu P S Williams H J Smith R D Sewell A Patel J P Gonzalez 《Journal of enzyme inhibition》1989,3(2):103-117
Some 2-substituted-(2'-aminophenyl)-4-thioxohydantoic acids (o-amino PTC-amino acids) have antinociceptive activity when administered (icv) alone (IC50 = 0.04-0.87 microM/animal) and show a striking prolongation of the antinociceptive action of (D-Ala-2 D-Leu5)-enkephalin (DADL) in combination. The effects are thought to be mediated via opioid receptors since they are naloxone-reversible. Although inhibitors of the enkephalin degrading puromycin-insensitive, bestatin-sensitive aminopeptidase (possibly aminopeptidase M) their action is weak (IC50 = 32 microM leucine, 536 microM, glycine) and they might be considered to have a direct antinociceptive effect on opioid receptors. The titled compounds constitute novel 'lead' compounds for the development of potent aminopeptidase M inhibitors. 相似文献
90.
4-Carboxymethylamino-4-oxo-3-(4'-aminophenylamino) butanoic acid (25), its ethyl ester (26) and the corresponding unsubstituted-aryl analogues (17) and (16) are fairly potent inhibitors of enkephalinase (neutral endopeptidase; EC 3.4.24.11), Ki = 0.14-0.39 microM, with weak inhibitory potency, Ki = 15-75 microM, towards aminopeptidase MII. In the mouse abdominal constriction test, the esters (26) and (16) showed systemic inhibitory (antinociceptive) activity with ED50 values 62 +/- 3.05 and 81 +/- 1.74 mg/kg respectively. In the mouse tail immersion test, both (26) and (16) exhibited antinociceptive activity when administered intracerebroventricularly and (26) also exhibited a systemic effect which was only partially reversed by naltrexone. The antinociceptive effect seen with (26) reflects its ranking in vitro as an inhibitor of enkephalinase (Ki = 0.14 microM) but it is possible that this effect is not totally opioid-mediated. Compounds (26) and (16) represent the first combined inhibitors of enkephalinase and aminopeptidase MII. 相似文献