全文获取类型
收费全文 | 1662篇 |
免费 | 101篇 |
国内免费 | 52篇 |
专业分类
1815篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 14篇 |
2020年 | 32篇 |
2019年 | 28篇 |
2018年 | 26篇 |
2017年 | 41篇 |
2016年 | 40篇 |
2015年 | 40篇 |
2014年 | 61篇 |
2013年 | 153篇 |
2012年 | 54篇 |
2011年 | 108篇 |
2010年 | 46篇 |
2009年 | 102篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 72篇 |
2005年 | 75篇 |
2004年 | 69篇 |
2003年 | 63篇 |
2002年 | 51篇 |
2001年 | 38篇 |
2000年 | 29篇 |
1999年 | 39篇 |
1998年 | 36篇 |
1997年 | 28篇 |
1996年 | 27篇 |
1995年 | 42篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 49篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 18篇 |
1984年 | 28篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 3篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
排序方式: 共有1815条查询结果,搜索用时 9 毫秒
71.
72.
邱全胜 《Acta Botanica Sinica》1999,41(9):962-966
以大豆( Glycine max L.) 下胚轴为材料, 采用二相法制得高纯度质膜微囊。实验发现,K+ 对质膜H+_ATPase水解活力和转运活力刺激差别显著,对转运活力刺激850% , 对水解活力仅刺激28 .2% 。动力学结果表明,有K+时ATP水解的Km 值为0.70 mmol/L,Vmax 为344 .8 nmol Pi·mg-1 protein·min-1 ; 无K+ 时ATP水解的Km 值为1 .14mmol/L, Vmax为285.7 nmol Pi·mg-1 protein·min-1 。K+ 对ATP水解的最适pH 值也有影响,有K+ 时为6 .5 ,无K+ 时降低到6.0 。进一步实验发现,K+ 对羟胺和钒酸钠的抑制作用影响较大,K+ 可以提高质膜H+_ATPase 对羟胺和钒酸钠的敏感性。结果表明,K+ 可以调节大豆下胚轴质膜H+_ATPase 水解与转运活力之间的偶联程度 相似文献
73.
以普洱茶和玫瑰花为主要原料,采用正交试验技术、酶解技术、常规浸提技术等方法,制备茶饮料。结果表明,浸提最佳工艺参数是玫瑰普洱原料的拼配比例为玫瑰干花32.5%,一年陈熟普洱茶67.5%;浸提时间40 min,茶水质量比1∶25,浸提温度90 ℃,浸提2次;浸提液加入0.08%单宁酶和0.04%风味蛋白酶进行酶解,玫瑰普洱提取液71.40 mL,白砂糖41.60 g,Vc 0.20 g,柠檬酸钠0.14 g,水893.19 mL。该饮料审评结果为汤色较红亮,澄清;玫瑰香气明显,茶香足陈香明显,滋味醇香爽口,温润滑舌,且在一年常温保质期内无沉淀生成。 相似文献
74.
Intracellular signal transduction pathways transmit signals from the cell surface to various intracellular destinations, such
as cytoskeleton and nucleus through a cascade of protein-protein interactions and activation events, leading to phenotypic
changes such as cell proliferation, differentiation, and death. Over the past two decades, numerous signaling proteins and
signal transduction pathways have been discovered and characterized. There are two major classes of signaling proteins: phosphoproteins
(e.g., mitogen-activated protein kinases) and guanosine triphosphatases (GTPases; e.g., Ras and G proteins). They both function
as molecular switches by addition and removal of one or more high-energy phosphate groups. This review discusses developments
that seek to quantify the signal transduction processes with kinetic analysis and mathematical modeling of the signaling phosphoproteins
and GTPases. These studies have provided insights into the sensitivity and specificity amplification of biological signals
in integrated systems. 相似文献
75.
双酶法制备玉米皮膳食纤维的研究 总被引:1,自引:0,他引:1
采用蛋白酶和淀粉酶结合水解制备玉米皮膳食纤维,通过正交试验确立了玉米皮膳食纤维的双酶法制备工艺。双酶法制备的玉米皮膳食纤维的产率为59.4%,膳食纤维的蛋白质量分数为0.82%,淀粉质量分数为1.42%,灰分为0.4%,水分质量分数为8.6%,持水力为5.9±0.4 g.g-1。 相似文献
76.
猕猴桃属(Actinidia)植物全世界有66种,约有118个种下分类单位(也有新的划分方法将其划分为54种21变种),其中大部分为中国特有。在猕猴桃杂交育种中,不同倍性之间选配不当会出现杂交失败、后代不育等现象,因此倍性鉴定是猕猴桃常规育种亲本选择的前提条件之一。但到目前为止,不少猕猴桃种或亚种的染色体倍性研究并不十分清楚,因而限制了这些资源的进一步开发利用。该研究针对广西植物研究所猕猴桃种质资源圃收集的目前倍性尚不明确的白萼、白花柱果、二色花、临桂、卵圆叶、桃花、宛田、长果、融水和五瓣猕猴桃等10个种类的猕猴桃,使用酸解法制备染色体标本,通过显微镜观察确定其倍性。这10个种类大多为广西特有,其中蕴藏着独特的优良园艺性状,具有很高的生产和开发价值。该研究结果表明这10个种类猕猴桃的染色体倍性均为二倍体(2n=2x=58)。该研究结果进一步丰富了猕猴桃种质资源多样性数据库,为这些猕猴桃资源的合理开发利用奠定了基础。 相似文献
77.
Fermentation and recovery of glutamic acid from palm waste hydrolysate by Ion-exchange resin column 总被引:1,自引:0,他引:1
Glutamic acid produced from palm waste hydrolysate by fermentation with Brevibacterium lactofermentum ATCC 13869 is produced with a remarkably high yield compared with that produced from pure glucose as a carbon source. The produce yield is 70 g/L with glucose, wherease, when palm waste hydrolysate is the fermentation medium in the same bioreactor under same conditions, it is 88 g/L. The higher yield may be attributed to the fact that this organism has the ability to convert sugars other than only glucose present in the hydrolysate. Bioreactor conditions most conducive for maximum production are pH 7.5, temperature of 30 degrees rmentation period of 48 h, inoculum size 6%, substrate concentration of 10 g per 100 mL, yeast extract 0.5 g per 100 mL as a suitable N source, and biotin at a concentration of 10 pg/L. Palm waste hydrolysate used in this study was prepared by enzymic saccharification of treated palm press fiber under conditions that yielded a maximum of 30 g/L total reducing sugars. Glutamic acid from fermentation broth was recovered by using a chromatographic column (5cm x 60 cm) packed with a strong ion-exchange resin. The filtered broth containing glutamic acid and other inorganic ions was fed to the fully charged column. The broth was continuously recycled at a flow rate of 50 mL/min (retention time of 55 min) until glutamic acid was fully adsorbed on the column leaving other ions in the effluent. Recovery was done by eluting with urea and sodium hydroxide for total displacement of glutamic acid from the resin. The eluent containing 88 g/L of glutamic acid was concentrated by evaporation to obtain solid crystals of the product. (c) 1995 John Wiley & Sons, Inc. 相似文献
78.
We have previously reported that treatment of CsA with aqueous HCl gives rise to the formation of a number of water-soluble compounds. Two of these were identified from their FAB-MS/MS spectra as open-chain nona- and decapeptides. We describe here the identification of two other main compounds deriving from the same treatment. Identification was rendered possible from the comparison of their FAB-MS/MS spectra with those of methyl and acetyl derivatives. The two compounds are water-soluble, open-chain undecapeptides corresponding to 1,11 seco-CsA and of 4,5 seco-isoCsA, respectively. 相似文献
79.
Satoru Masuda Shigefumi Kuwahara Toshio Suguro Kenji Mori 《Bioscience, biotechnology, and biochemistry》2013,77(11):2515-2520
The (S)-enantiomer of the sex pheromone of the yellow scale (Aonidiella citrina), (S,E)-6-isopropyl-3,9-dimethyl-5,8-decadienyl acetate, was stereoselectively synthesized from (R)-(+)-citronellic acid. 相似文献
80.
Norman J. Oppenheimer 《Molecular and cellular biochemistry》1994,138(1-2):245-251
The pyridine nucleotide have important non-redox activities as cellular effectors and metabolic regulators [1–3]. The enzyme-catalyzed cleavage of the nicotinamide-ribosyl bond of NAD+ and the attendant delivery of the ADPRibosyl moiety to acceptors is central to these many diverse biological activities. Included are the medically important NAD-dependent toxins associated with cholera, diphtheria, pertussis, and related disease [4]; the reversible ADPRibosylation-mediated biological regulatory systems [5,6]; the synthesis of poly (ADPRibose) in response to DNA damage or cellular, division [7]; and the synthesis of cyclic ADPRibose as part of an independent, calcium-mediated regulatory system[8]. As will be presented in this chapter, all evidence points to both the chemical and enzyme-catalyzed cleavage of the nicotinamide-ribosyl bond being dissociative in character via an oxocarbenium intermediate. 相似文献