全文获取类型
收费全文 | 3616篇 |
免费 | 145篇 |
国内免费 | 263篇 |
专业分类
系统科学 | 113篇 |
丛书文集 | 72篇 |
教育与普及 | 35篇 |
理论与方法论 | 4篇 |
现状及发展 | 449篇 |
综合类 | 3347篇 |
自然研究 | 4篇 |
出版年
2024年 | 10篇 |
2023年 | 17篇 |
2022年 | 35篇 |
2021年 | 36篇 |
2020年 | 48篇 |
2019年 | 50篇 |
2018年 | 48篇 |
2017年 | 64篇 |
2016年 | 66篇 |
2015年 | 63篇 |
2014年 | 147篇 |
2013年 | 107篇 |
2012年 | 172篇 |
2011年 | 168篇 |
2010年 | 121篇 |
2009年 | 204篇 |
2008年 | 197篇 |
2007年 | 228篇 |
2006年 | 272篇 |
2005年 | 250篇 |
2004年 | 229篇 |
2003年 | 200篇 |
2002年 | 189篇 |
2001年 | 139篇 |
2000年 | 146篇 |
1999年 | 136篇 |
1998年 | 89篇 |
1997年 | 90篇 |
1996年 | 82篇 |
1995年 | 61篇 |
1994年 | 66篇 |
1993年 | 52篇 |
1992年 | 52篇 |
1991年 | 53篇 |
1990年 | 35篇 |
1989年 | 28篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1955年 | 1篇 |
排序方式: 共有4024条查询结果,搜索用时 31 毫秒
981.
2种无银保鲜剂对切花菊的保鲜效应 总被引:3,自引:0,他引:3
研究保鲜剂(2%蔗糖+50mg/L柠檬酸+100mg/L8-羟基喹啉+1mg/L6-BA)和保鲜剂2号(2%蔗糖+50mg/L水杨酸+100mg/L8-羟基喹啉+1mg/L6-BA)对“黄秀凤”切花菊(Chrysanthemummorifoliumcv.“HuangXiufeng”)瓶插寿命和瓶插期间花枝的水分状况,叶绿素和可溶性蛋白质含量以及过氧化物酶(POD)活性等生理延长2d但与延长花冠寿命 相似文献
982.
J. Gómez-Ambrosi G. Frühbeck J. A. Martínez 《Cellular and molecular life sciences : CMLS》1999,55(6-7):992-997
The short-term effects of leptin and a β3-adrenoceptor agonist on thermogenesis and expression of uncoupling proteins (UCPs) in brown adipose tissue (BAT) and muscle
and their possible interactions were assessed. One hour after administration of the β3-adrenoceptor agonist Trecadrine, a statistically significant increase in UCP1 messenger RNA (mRNA) expression in BAT was
observed, whereas UCP2 and UCP3 in both BAT and gastrocnemius muscle were unaffected. Leptin induced an upregulation of UCP3
mRNA in muscle, with no changes in BAT UCP1 mRNA. A statistical interaction was found between leptin and Trecadrine in rectal
temperature. The present study provides evidence, for the first time, of the induction of UCP3 mRNA expression in skeletal
muscle by leptin in nongenetically obese animals.
Received 5 March 1999; received after revision 19 April 1999; accepted 21 April 1999 相似文献
983.
Oka T Nishimoto Y Sasagawa T Kanouchi H Kawasaki Y Natori Y 《Cellular and molecular life sciences : CMLS》1999,55(1):131-134
An efficient Escherichia coli expression system for the production of a perchloric acid-soluble protein (PSP) has been constructed. Complementary DNA encoding
PSP was inserted into an inducible bacterial expression vector pGEX-4T-1. After the plasmid introduced into E. coli was expressed by isopropyl 1-thio-β-D-galactopyranoside (IPTG), the recombinant product was purified by glutathione-Sepharose 4B affinity chromatography. The
purified product showed the expected NH2-terminal sequence, but the translation inhibitory activity of this product was 10 times lower compared with that of authentic
PSP isolated from rat liver.
Received 8 October 1998; received after revision 6 November 1998; accepted 6 November 1998 相似文献
984.
Sánchez-Margalet V González-Yanes C Santos-Alvarez J Najib S 《Cellular and molecular life sciences : CMLS》1999,55(1):142-147
Insulin action is initiated by binding to its cognate receptor, which then triggers multiple cellular responses by activating
different signaling pathways. There is evidence that insulin receptor signaling may involve G protein activation in different
target cells. We have studied the activation of G proteins in rat hepatoma (HTC) cells. We found that insulin stimulated binding
of guanosine 5′-O-(3-thiotriphosphate) (GTP-γ-35S) to plasma membrane proteins of HTC cells, in a dose-dependent manner. This effect was completely blocked by pertussis toxin
treatment of the membranes, suggesting the involvement of G proteins of the Gα
i/Gα
o family. The expression of these Gα proteins was checked by Western blotting. Next, we used blocking antibodies to sort out the specific Gα protein activated by insulin stimulation. Anti-Gα
il,2 antibodies completely prevented insulin-stimulated GTP binding, whereas anti-Gα
o,i3 did not modify this effect of insulin on GTP binding. Moreover, we found physical association of the insulin receptor with
Gα
i1,2 by copurification studies. These results further support the involvement of a pertussis toxin-sensitive G protein in insulin
receptor signaling and provides some evidence of specific association and activation of Gα
i1,2 protein by insulin. These findings suggest that Gα
i1,2 proteins might be involved in insulin action.
Received 23 September 1998; received after revision 23 November 1998; accepted 25 November 1998 相似文献
985.
罗辽复 《内蒙古大学学报(自然科学版)》1995,26(2):172-180
综述了蛋白质折送的基本实验特征,讨论了亘子构象动力学的有关理论结果,分析了格子模拟得到的启示,在此基础上对Anfinsen的热力学假设提出质疑,提出鲁棒极小值的概念,研究了序列决定构象问题,并对折迭途径中的一些问题进行了初步探讨。 相似文献
986.
不同活力花生种子蛋白质的研究 总被引:1,自引:0,他引:1
花生种子经人工加速老化处理后种子活力下降,其蛋白质总含量、胚轴和子叶中的蛋白质含量均随之下降,胚轴、子叶中可溶性蛋白质含量也随种子活力的下降而减少,低活力花生种子胚轴可溶性蛋白质和结合蛋白质的合成能力显著下降.低活力种子萌发时,贮藏蛋白质迅速降解,而新合成的蛋白质却较少,随着种子活力的下降,胚轴可溶性蛋白质和结合蛋白质的种类也随之减少. 相似文献
987.
将分形理论应用于血小板聚集试验。结果表明,分形几何是处理血小板聚集团块这类不规则图形的有力工具。 相似文献
988.
P. P. Halarnkar G. P. Jackson K. M. Straub D. A. Schooley 《Cellular and molecular life sciences : CMLS》1993,49(11):988-994
We studied time-dependent metabolism of (10R)-[3H] juvenile hormone (JH) III and (10R, 11S)-[3H]JH I injected intoManduca sexta larvae; the hormones are metabolized to polar metabolites, expecially the JH acid-diol, and an unknown. Products were analyzed using a reversed-phase liquid chromatography assay. (10R)-JH III is metabolized much more rapidly than (10R, 11S)-[3H]JH I, whether injected seperately or as a mixture of hormones. The unknown metabolites of JH I and JH III were identified as phosphate conjugates of JH I and JH III diol by tandem mass spectral analysis of isolated samples. The phosphate conjugate of JH I diol is the principle end product of JH I metabolism. 相似文献
989.
采用国产单克隆抗体酶标试剂盒(McAb—ELISA)对广东某地区无乙肝症状的298人作了血清前S_2蛋白及抗前S_2检测,同时检测各项乙型肝炎病毒血清学标志(HBVM)及肝功能。全部检测对象肝功能正常。前S_2阳性率7.72%。抗前S_2阳性率5.70%。前者与HBsAg及其它乙肝病毒复制标志(HBcAg、PHSA-R、HBcAg、抗-HBcIgM及HBVDNA)有平行关系,后者则与抗HBs有平行关系。结果提示前S_2可作为一项敏感的HBV复制及传染性的指标,抗前S_2是一项乙肝感染的恢复标志,二者有重要的流行病学与临床意义,检测证实人群中存在相当数量的HBV携带者和隐性感染者。 相似文献
990.
为建立文题所述模型,以微乳液的稳定性理论为基础,综合分析了表面活性剂分子在油-水界面上的缔合作用、界面膜弯曲时产生的附加能量、各种类型的混合熵以及表面活性剂分子和蛋白质分子的静电作用。所得模型正确地反映了含蛋白质的逆胶束系统稳定的原因,较好地描述了蛋白质转移后胶束大小的变化以及蛋白质转移率随电解质浓度变化的特殊的实验规律。 相似文献