全文获取类型
收费全文 | 7321篇 |
免费 | 577篇 |
国内免费 | 1篇 |
专业分类
7899篇 |
出版年
2023年 | 57篇 |
2022年 | 107篇 |
2021年 | 222篇 |
2020年 | 141篇 |
2019年 | 153篇 |
2018年 | 172篇 |
2017年 | 152篇 |
2016年 | 253篇 |
2015年 | 421篇 |
2014年 | 447篇 |
2013年 | 527篇 |
2012年 | 676篇 |
2011年 | 635篇 |
2010年 | 392篇 |
2009年 | 361篇 |
2008年 | 499篇 |
2007年 | 426篇 |
2006年 | 416篇 |
2005年 | 352篇 |
2004年 | 310篇 |
2003年 | 245篇 |
2002年 | 260篇 |
2001年 | 51篇 |
2000年 | 42篇 |
1999年 | 52篇 |
1998年 | 44篇 |
1997年 | 36篇 |
1996年 | 32篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 17篇 |
1992年 | 39篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 27篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1973年 | 9篇 |
排序方式: 共有7899条查询结果,搜索用时 15 毫秒
11.
The effect of short chain fatty acids on the cellular permeability of embryonic axis inGcer arietinum seeds was studied. Octanoic (OCT) and nonanoic (NON) adds, which reduce both germination and growth of the embryonic axis and raise the inhibitor effects of the supraoptimal temperatures (30?C), induce a greater ionic efflux into the medium (conductivity). NON reduces glucose (3-0-MG) and K+ (86Rb) uptake during the germinative process, this action being counteracted by fusicoccin (FC) at optimal (25?C) and supraoptimal temperatures (30 ?C). Tonoplast and plasmalemma increase their permeability to the K+ efflux when NON is present. Addition of NON+FC gives rise to higher values in the efflux rate, the vacuolar compartment being the most affected. Temperatures around zero (2 ?C) notably reduce the isotope efflux from cytosol and vacuole. NON acid does not significantly affect the efflux of3H-ABA, suggesting that it does not cause any important changes in the phytohormone compartmentation. 相似文献
12.
Fos-Jun and the primary genomic response in the nervous system 总被引:3,自引:0,他引:3
13.
J Mouecoucou C Villaume H M Bau J P Nicolas L Mejean 《Reproduction, nutrition, development》1990,30(4):541-547
Male 21 d-old Wistar rats, were fed for 4 wk with diets containing casein or soybean proteins (10%) with 0.5, 1, 2 or 3% sodium alginate or sodium carrageenan or without any alginate or carrageenan. Daily protein intake and weight gain of casein-fed rats were not significantly different (P less than 0.05) from those of rats fed soybean meal with alginate, whatever the dose received. Rats fed 3% carrageenan in soybean meal had significantly higher feed intake than that of rats fed casein. At the levels studied, alginate had no effect on the Protein Efficiency Ratio (PER), but carrageenan did. The addition of increased quantities of carrageenan to soybean meal followed by heating the mixture led to a progressive and significant decrease in PER at all levels of carrageenan compared to casein feeding. The addition of 3% carrageenan to heated soybean meal, corresponding to 0.62% of meal diet, led to a significant decrease in PER. These results confirm the precipitating role of carrageenans on proteins. 相似文献
14.
Dale L. Birkle Pawels Kurian Pierre Braquet Nicolas G. Bazan 《Journal of neurochemistry》1988,51(6):1900-1905
We have investigated the effects of the specific platelet-activating factor (PAF; 1-alkyl-2-acetyl-glycerophosphocholine) antagonist BN52021 on free fatty acid (FFA) and diacylglycerol (DG) accumulation and on the loss of fatty acids from phosphatidylinositol-4,5-bisphosphate (PIP2) in mouse brain. Mice were pretreated with BN52021 (10 mg/kg, i.p.) 30 min before electroconvulsive shock (ECS) or postdecapitation ischemia. These procedures cause rapid breakdown of PIP2 and accumulation of FFA and DG. Lipid extracts were prepared from microwave-fixed cerebrum and fractionated by TLC, and the fatty acid methyl esters were prepared by methanolysis and quantified by capillary GLC. In saline or vehicle (dimethyl sulfoxide)-treated mice, ECS caused marked accumulation of FFA and DG and loss of mainly stearic (18:0) and arachidonic (20:4) acids from PIP2. BN52021 pretreatment of ECS-treated mice decreased the accumulation of free palmitic (16:0), 18:0, 20:4, and docosahexaenoic (22:6) acids with no effect on the fatty acids in DG or the loss of PIP2. BN52021 had no effect on basal levels of FFA, DG, or PIP2. One minute of postdecapitation ischemia induced PIP2 loss and accumulation of FFA and DG. BN52021 attenuated the accumulation of free 20:4 and 22:6 acids, decreased the content of oleic (18:1), 20:4, and 22:6 acids in DG, but had no effect on PIP2 loss. These data indicate that BN52021 reduces the injury-induced activation of phospholipase A2 and lysophospholipase, which mediate the accumulation of FFA in brain, while having a negligible effect on phospholipase C-mediated degradation of PIP2. 相似文献
15.
The serum unsaturated vitamin B12-binding capacity (UBBC), unsaturated transcobalamin (UTC) I, UTC II, UTC III levels, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase activities and bilirubin concentration were estimated in 61 patients with liver diseases (31 with hepatoma, 30 with viral hepatitis). The levels of serum cobalamin, UTC I, UTC III, UBBC, alanine and aspartate aminotransferases, and bilirubin were raised in both hepatoma and viral hepatitis patients. Serum UTC II was reduced in both conditions. Alkaline phosphatase activity was significantly increased in hepatoma. Four significant correlations were observed among these parameters in the hepatoma patients while only one significant correlation was observed in viral hepatitis. 相似文献
16.
17.
18.
Elena B. Rodriguez de Turco Susana Morelli de Liberti Nicolas G. Bazan 《Journal of neurochemistry》1983,40(1):252-259
The pool size and composition of free fatty acids (FFA) and diglycerides (DG) from the cerebrum and cerebellum of rats undergoing bicuculline-induced seizures were studied. A fourfold increase in cerebral FFA occurred 3-4 min after bicuculline injection; arachidonic and stearic acids were the principal fatty acids accumulated. Cerebellar FFA also increased, but to a lesser extent. An increased production of arachidonic acid took place in the cerebrum as a function of time after bicuculline injection. Other fatty acids produced were oleic, palmitic, and docosahexaenoic acids. A twofold increase in cerebral arachidonic acid was seen at the time of the first generalized tonic-clonic convulsion. However, a 13- to 17-fold increase in arachidonic acid was seen approximately 5-6 min after bicuculline injection. The rise in other FFA was much smaller. Stearoyl- and arachidonoyl-DG were also accumulated. The drug alpha-methyl-p-tyrosine was found to (a) potentiate the bicuculline-stimulated release of cerebellar FFA, and (b) inhibit by 70% the production of stearoyl- and arachidonoyl-DG in the cerebrum and cerebellum. Basal production of FFA was stimulated by p-chlorophenylalanine, but the drug had no effect on the bicuculline-induced changes. Hydrolysis of phospholipids enriched in stearoyl-arachidonoyl groups, such as phosphatidylinositol of excitable membranes, may be stimulated during seizures. 相似文献
19.
20.