全文获取类型
收费全文 | 4573篇 |
免费 | 224篇 |
国内免费 | 149篇 |
出版年
2024年 | 3篇 |
2023年 | 46篇 |
2022年 | 46篇 |
2021年 | 94篇 |
2020年 | 137篇 |
2019年 | 80篇 |
2018年 | 90篇 |
2017年 | 87篇 |
2016年 | 104篇 |
2015年 | 156篇 |
2014年 | 247篇 |
2013年 | 270篇 |
2012年 | 199篇 |
2011年 | 274篇 |
2010年 | 220篇 |
2009年 | 231篇 |
2008年 | 266篇 |
2007年 | 233篇 |
2006年 | 237篇 |
2005年 | 204篇 |
2004年 | 194篇 |
2003年 | 145篇 |
2002年 | 126篇 |
2001年 | 114篇 |
2000年 | 102篇 |
1999年 | 94篇 |
1998年 | 127篇 |
1997年 | 75篇 |
1996年 | 77篇 |
1995年 | 83篇 |
1994年 | 73篇 |
1993年 | 92篇 |
1992年 | 62篇 |
1991年 | 64篇 |
1990年 | 56篇 |
1989年 | 37篇 |
1988年 | 28篇 |
1987年 | 33篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有4946条查询结果,搜索用时 140 毫秒
1.
Abstract The amounts of mRNA and protein of plasma membrane proton-ATPase were measured in the salt-tolerant yeast Zygosaccharomyces rouxii by Northern and Western blot analyses. Although their amounts were independent of growth phase, their synthesis were induced when yeast cells were grown in the presence of NaCl or were subjected to NaCl shock. This finding was consistent with our previous result that plasma membrane proton-ATPase activity was elevated in Z. rouxii cells grown in medium containing high concentrations of NaCl. 相似文献
2.
3.
《Cryobiology》2020
Cryopreserved canine adipose-derived mesenchymal stromal cells (Ad-MSCs) can be used instantly in dogs for clinical uses. However, cryopreservation results in a reduction of the cellular viability, proliferation, and anti-oxidation of post-thawed Ad-MSCs. Therefore, there is a need for in-vitro procedure to improve post-thawed Ad-MSCs’ viability, proliferation, anti-oxidation, and differentiation capacity. In this study, fresh-Ad-MSCs were activated with heat shock, hypoxia (5% O2), or hypoxia (5% O2) + heat shock treatments. The results showed that compared to the other treatments, heat shock significantly improved the proliferation rate, anti-oxidation, heat shock proteins and growth factors expressions of canine-fresh-Ad-MSCs. Consequently, fresh-Ad-MSCs were heat-shocked and then cryopreserved with different combinations of dimethyl sulfoxide (Me2SO) and fetal bovine serum (FBS) to determine the combination that could effectively preserve the cellular viability, proliferation, anti-oxidation and differentiation capacity of Ad-MSCs after cryopreservation. We found that C-HST-Ad-MSCs cryopreserved with 10% Me2SO + 40% FBS presented significantly (p < 0.05) improved cellular viability, proliferation rate, anti-oxidant capacity, and differentiation potential as compared to C-HST-Ad-MSCs cryopreserved with 1% Me2SO + 10% FBS or 1% Me2SO alone or control. We concluded, heat shock treatment is much better to enhance the characteristics of fresh-Ad-MSCs than other treatments, moreover, C-HST-Ad-MSCs in 10% Me2SO + 40% FBS showed better results compared to other cryopreserved groups. However, future work is required to optimize the expression of heat shock proteins, which would further improve the characteristics of fresh- and cryopreserved-HST-Ad-MSCs and reduce the dependency on Me2SO and FBS. 相似文献
4.
5.
6.
The mitochondrial small heat-shock protein protects NADH:ubiquinone oxidoreductase of the electron transport chain during heat stress in plants 总被引:1,自引:0,他引:1
Functional inactivation of the mitochondrial small heat-shock protein (lmw Hsp) in submitochondrial vesicles using protein-specific antibodies indicated that this protein protects NADH:ubiquinone oxidoreductase (complex I), and consequently electron transport from complex I to cytochrome c:O2 oxidoreductase (complex IV). Lmw Hsp function completely accounted for heat acclimation of complex I electron transport in pre-heat-stressed plants. Addition of purified lmw Hsp to submitochondrial vesicles lacking this Hsp increased complex I electron transport rates 100% in submitochondrial vesicles assayed at high temperatures. These results indicate that production of the mitochondrial lmw Hsp is an important adaptation to heat stress in plants. 相似文献
7.
Heat stress reduces maize yield and several lines of evidence suggest that the heat lability of maize endosperm ADP-glucose pyrophosphorylase (AGPase) contributes to this yield loss. AGPase catalyzes a rate-limiting step in starch synthesis. Herein, we present a novel maize endosperm AGPase small subunit variant, termed BT2-TI that harbors a single amino acid change of residue 462 from threonine to isoleucine. The mutant was isolated by random mutagenesis and heterologous expression in a bacterial system. BT2-TI exhibits enhanced heat stability compared to wildtype maize endosperm AGPase.The TI mutation was placed into another heat-stable small subunit variant, MP. MP is composed of sequences from the maize endosperm and the potato tuber small subunit. The MP-TI small subunit variant exhibited greater heat stability than did MP. Characterization of heat stability as well as kinetic and allosteric properties suggests that MP-TI may lead to increased starch yield when expressed in monocot endosperms. 相似文献
8.
Ribonuclease (EC 2.7.7.17) activity in the obligate halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. was studied in relation to salinity (increasing concentrations of NaCl) of incubation and growth media. In vitro, the addition of 50 to 400 m M NaCl did not affect ribonuclease activity. This result, which was also found for Phaseolus vulgaris , indicates that the hydrolase is insensitive to high saline concentrations. The subcellular distribution of RNase activity did not change significantly with the salinity of the medium or with the age of the plant. The microsomal ribonuclease activity expressed on a fresh weight basis represented in every case less than 6% of the total activity. After 23 days of culture, the absence of salt stimulated the activity of soluble ribonuclease in aerial parts of Suaeda ; inversely, the capacity of the enzyme was lower under optimal saline conditions (130 m M NaCl). This was also evidenced by transfer of whole plants from a non-saline to a saline medium. Such a saline shock caused a decrease followed by a stabilization of the capacity of ribonuclease from Suaeda . The influx of NaCl in the tissues lowered the activity of the hydrolase. 相似文献
9.
10.
目的:观察不同酸中毒条件下正常大鼠和脓毒性休克大鼠胸主动脉对多巴胺反应性的变化。方法:采用离体血管灌流方法,观察对照组和脓毒性休克组大鼠胸主动脉在不同pH条件下的反应性变化。结果:pH值依次降低,对照组及脓毒性休克组离体胸主动脉对多巴胺反应性均下降,在相同pH值条件下脓毒性休克组比对照组离体血管对多巴胺反应性下降更为明显。结论:①环境pH值的下降会导致正常大鼠和脓毒性休克大鼠离体动脉对多巴胺反应性的下降。②在相同的酸性环境中脓毒性休克大鼠的血管对多巴胺刺激的反应性更差,更易失去活性。 相似文献