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991.
水稻淀粉胚乳程序性细胞死亡中的去核化 总被引:6,自引:0,他引:6
对水稻品种中籼8836淀粉胚乳细胞的去核化发育阶段的细胞超微结构变化和同期籽粒灌浆速率及相关酶活性的动态进行了观察和分析。开花受精后约在第3天胚乳完成细胞化,花后第5天少数淀粉胚乳细胞启动去核发育过程。核消亡是淀粉胚乳细胞程序性细胞死亡(PCD)的第一步。同一籽粒淀粉胚乳细胞的去核进程是不同步的。花后第13天所有淀粉胚乳细胞都已完成去核过程。在去核过程中,胚乳核的形态变化特征既有动植物PCD的共性又有其特殊性。伴随核降解过程,一部分线粒体解体,表明去核化与线粒体解体有一定联系。在去核化发育阶段,与PCD有关的酶类,如超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性非常高;与淀粉合成有关的酶类,如ADPG焦磷酸化酶、可溶性淀粉合成酶(SSS酶)、淀粉分支酶(或Q酶)也表现出很高的活性。去核化发育阶段籽粒灌浆速率最高,籽粒增重亦最快。淀粉胚乳细胞去核之后,细胞并未立即死亡,这些无核的细胞仍维持正常有序的代谢活动,继续进行淀粉和贮藏蛋白的合成与积累,但上述酶类的活性明显降低,灌浆速率也明显趋缓。淀粉胚乳细胞最终被贮藏物质充满时成为死细胞,完成其程序性死亡过程。Evan‘s blue染色鉴定表明淀粉胚乳细胞死亡不同步,细胞死亡在淀粉胚乳组织中是随机发生的。 相似文献
992.
Guang-Jin Zhou Yue Zhang Jian Wang Jin-Hu Guo Jun Ni Zhao-Ming Zhong Li-Qun Wang Yong-Jun Dang Jian-Feng Dai Long Yu 《DNA sequence》2004,15(3):219-224
Present work reported the cloning and characterization of a human novel RNA binding gene Partner of NOB1 (PNO1), with a length of 1637bp and a putative open reading frame of 759 bp, isolated from human kidney. It is composed of seven exons and is localized on chromosome 2p14. Western blot showed that the molecular weight of PNO1 is about 35kDa. RT-PCR results in 16 human tissues indicated that PNO1 is expressed mainly in liver, lung, spleen and kidney, slightly in thymus, testis, ovary, respectively, but not in heart, brain, skeletal muscle, placenta, pancreas, prostate, small intestine, colon and peripheral blood leukocytes. GFP fusion expression in mammalian cells exhibited its localization in the nucleus, especially in nucleoli. Subcellular localization of thirteen GFP fusion PNO1 deletion proteins showed that the region of 92-230 aa is solely responsible for its nucleolar retention, and KH domain alone is not sufficient for nucleolar retention. The PNO1 family shows significant conservation in both eukaryotes and prokaryotes. 相似文献
993.
根据GenBank中公布的粟酒裂殖酵母(Schizosaccharomyces pombe)N-糖酰胺酶(Png1p)cDNA序列, 设计并合成一对特异性引物, 利用RT-PCR技术从粟酒裂殖酵母中克隆出糖酰胺酶cDNA。将得到的基因克隆到表达载体pET-15b中。重组质粒转入大肠杆菌BL21(DE3)中, 经诱导表达和纯化提取后, 进行酶活测定。实验结果表明, 该酶的分子量约为39 kD, 纯化后的重组N-糖酰胺酶可以对变性处理的糖蛋白进行糖链的切除, 且这种作用需要还原剂DTT的辅助作用; N-糖酰胺酶只对错误折叠的糖蛋白有作用, 对天然的糖蛋白没有作用。等量粟酒裂殖酵母Png1p在不同温度、pH、DTT浓度和底物变性温度下对等量核糖核酸酶B(RNase B)的脱糖基化检测发现, 重组酶的最适反应温度30°C, 最适反应pH为7.0, 需要的最适DTT浓度为10 mmol/L, 底物在100°C处理10 min时酶的脱糖基化率最高。 相似文献
994.
从用于堆肥的水稻秸秆中初筛出一株高效纤维素降解菌L-06, 根据18S rRNA基因序列和菌株形态分析, 初步鉴定该菌为斜卧青霉(Penicillium decumbens)。研究了液体发酵培养基中氮源、碳源、表面活性剂、培养温度、起始pH以及接种量对该菌株各纤维素酶活力的影响。在最适条件下, 该菌的b-葡萄糖苷酶(BGL)、外切纤维素酶(CBH)于培养第3天酶活力分别达到1662 u/mL和2770 u/mL; 内切纤维素酶(EG)、滤纸糖化力(FPase)于培养第4天酶活力分别达到18064 u/mL和4035 u/mL。在产酶优化实验中, 该菌的EG和CBH在pH10的培养条件下分别保持了70%和43%的酶活性; 在50oC培养条件下EG和CBH分别保持了68%和59%的酶活性。表现出了耐热, 耐碱的特性。 相似文献
995.
氢酶是生物制氢的关键酶, 大多数氢酶因对氧极敏感而易失活, 因此提高氢酶的氧耐受性对生物制氢有重要意义。本研究利用1%甲基磺酸乙酯对Klebsiella oxytoca HP1进行了两轮诱变, 经40 mmol/L 甲硝唑和21%氧联合处理1 h(第一轮诱变)或2 h(第二轮诱变)进行筛选。所得突变菌株经产氢测试, 结果在15%氧浓度条件下, 第一代突变菌株HP1-A15产氢活性为出发菌株Klebsiella oxytoca HP1的3.70倍, 在21%氧浓度条件下第二代突变菌株 HPA15-37产氢活性为HP1-A15菌株的2.75倍, 是出发菌株的11倍。突变菌株HP1-A15和 HPA15-37具有较好的遗传稳定性。本试验结果说明利用MNZ和外加氧的方法适用于兼性厌氧菌耐氧产氢突变菌株的筛选。 相似文献
996.
Isaza CE Zhong X Rosas LE White JD Chen RP Liang GF Chan SI Satoskar AR Chan MK 《Biochemical and biophysical research communications》2008,373(1):25-29
Leishmaniasis is a tropical disease caused by Leishmania, eukaryotic parasites transmitted to humans by sand flies. Towards the development of new chemotherapeutic targets for this disease, biochemical and in vivo expression studies were performed on one of two M32 carboxypeptidases present within the Leishmania major (LmaCP1) genome. Enzymatic studies reveal that like previously studied M32 carboxypeptidases, LmaCP1 cleaves substrates with a variety of C-terminal amino acids—the primary exception being those having C-terminal acidic residues. Cleavage assays with a series of FRET-based peptides suggest that LmaCP1 exhibits a substrate length restriction, preferring peptides shorter than 9-12 amino acids. The in vivo expression of LmaCP1 was analyzed for each major stage of the L. major life cycle. These studies reveal that LmaCP1 expression occurs only in procyclic promastigotes—the stage of life where the organism resides in the abdominal midgut of the insect. The implications of these results are discussed. 相似文献
997.
Wang XJ Dong Z Zhong XH Shi RZ Huang SH Lou Y Li QP 《Biochemical and biophysical research communications》2008,365(3):548-554
Angiogenesis is essential for transplantation of mesenchymal stem cells (MSCs). Vascular endothelial growth factor (VEGF) is one of the most potent angiogenic factors identified to date. Elevated VEGF levels in MSCs correlate with the potential of MSCs transplantation. As an indirect angiogenic agent, transforming growth factor-β1 (TGF-β1) plays a pivotal role in the regulation of vasculogenesis and angiogenesis. However, the effect of TGF-β1 on VEGF synthesis in MSCs is still unknown. Besides, the intracellular signaling mechanism by which TGF-β1 stimulates this process remains poorly understood. In this article, we demonstrated that exposure of MSCs to TGF-β1 stimulated the synthesis of VEGF. Meanwhile, TGF-β1 stimulated the phosphorylation of Akt and extracellular signal-regulated kinase 1/2 (ERK1/2). Moreover, Ly 294002, a specific inhibitor of phosphatidylinositol-3-kinase (PI3K)/Akt significantly attenuated the VEGF synthesis stimulated by TGF-β1. Additionally, U0126, a specific inhibitor of ERK1/2, also significantly attenuated the TGF-β1-stimulated VEGF synthesis. These results indicated that TGF-β1 enhanced VEGF synthesis in MSCs, and the Akt and ERK1/2 activation were involved in this process. 相似文献
998.
999.
Lin N Tang Z Deng M Zhong Y Lin J Yang X Xiang P Xu R 《Biochemical and biophysical research communications》2008,372(1):260-265
During liver injury, bone marrow-derived mesenchymal stem cells (MSCs) can migrate and differentiate into hepatocytes. Hepatic stellate cell (SC) activation is a pivotal event in the development of liver fibrosis. Therefore, we hypothesized that SCs may play an important role in regulating MSC proliferation and differentiation through the paracrine signaling pathway. We demonstrate that MSCs and SCs both express hedgehog (Hh) pathway components, including its ligands, receptors, and target genes. Transwell co-cultures of SCs and MSCs showed that the SCs produced sonic hedgehog (Shh), which enhanced the proliferation and differentiation of MSCs. These findings demonstrate that SCs indirectly modulate the activity of MSCs in vitro via the Hh pathway, and provide a plausible explanation for the mechanisms of transplanted MSCs in the treatment of liver fibrosis. 相似文献
1000.
Oztürk N Kao YT Selby CP Kavakli IH Partch CL Zhong D Sancar A 《Biochemistry》2008,47(39):10255-10261
The photolyase/cryptochrome family is a large family of flavoproteins that encompasses DNA repair proteins, photolyases, and cryptochromes that regulate blue-light-dependent growth and development in plants, and light-dependent and light-independent circadian clock setting in animals. Phylogenetic analysis has revealed a new class of the family, named type III photolyase, which cosegregates with plant cryptochromes. Here we describe the isolation and characterization of a type III photolyase from Caulobacter crescentus. Spectroscopic analysis shows that the enzyme contains both the methenyl tetrahydrofolate photoantenna and the FAD catalytic cofactor. Biochemical analysis shows that it is a bona fide photolyase that repairs cyclobutane pyrimidine dimers. Mutation of an active site Trp to Arg disrupts FAD binding with no measurable effect on MTHF binding. Using enzyme preparations that contain either both chromophores or only folate, we were able to determine the efficiency and rate of transfer of energy from MTHF to FAD. 相似文献