全文获取类型
收费全文 | 11520篇 |
免费 | 1091篇 |
国内免费 | 1730篇 |
专业分类
14341篇 |
出版年
2024年 | 41篇 |
2023年 | 195篇 |
2022年 | 371篇 |
2021年 | 577篇 |
2020年 | 441篇 |
2019年 | 533篇 |
2018年 | 529篇 |
2017年 | 413篇 |
2016年 | 521篇 |
2015年 | 738篇 |
2014年 | 948篇 |
2013年 | 957篇 |
2012年 | 1145篇 |
2011年 | 1029篇 |
2010年 | 647篇 |
2009年 | 599篇 |
2008年 | 689篇 |
2007年 | 586篇 |
2006年 | 587篇 |
2005年 | 421篇 |
2004年 | 367篇 |
2003年 | 319篇 |
2002年 | 240篇 |
2001年 | 121篇 |
2000年 | 123篇 |
1999年 | 91篇 |
1998年 | 102篇 |
1997年 | 68篇 |
1996年 | 66篇 |
1995年 | 56篇 |
1994年 | 55篇 |
1993年 | 40篇 |
1992年 | 62篇 |
1991年 | 45篇 |
1990年 | 55篇 |
1989年 | 44篇 |
1988年 | 34篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 33篇 |
1984年 | 46篇 |
1983年 | 30篇 |
1982年 | 34篇 |
1981年 | 42篇 |
1980年 | 24篇 |
1979年 | 24篇 |
1978年 | 20篇 |
1977年 | 23篇 |
1975年 | 23篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
本研究目的在于探讨丝裂素活化蛋白激酶(MAPK)是否在AngⅡ(10-8mol/L)诱导的培养新生大鼠心肌成纤维细胞(FB)的增殖反应中起重要作用。实验以FB数目和DNA合成速率(3H-胸腺嘧啶掺入率)为增殖指标,[γ-32P]ATP掺入法和免疫印迹法分别测定FBMAPK的活性和含量,结果发现(1)AngⅡ处理FB24h后,DNA合成速率和细胞数比对照组分别增加60%和39%;(2)AngⅡ处理FB5min后,MAPK活性比对照组增高203%;(3)培养新生大鼠FB含有两个MAPK同型体-p44mapk和p42mapk,其中p44mapk含量高于p42mapk,分别为总量的58%和42%。AngⅡ处理5min后,MAPK蛋白含量(p44+p42〕增高429%,其中p44mapk的增加明显大于p42mapk的增加,分别比相应对照增高486%和349%。以上结果表明,AngⅡ诱导的MAPK活性和含量的增加,参与了FB的增殖反应,其中p44mapk的作用较为显著 相似文献
992.
乙肝病毒表面抗原preS1与人肿瘤坏死因子α融合基因的表达 总被引:6,自引:0,他引:6
用PCR法获得了HBsAgpreS1(1-65)肽段基因,将该基因融合在肿瘤坏死因子(hTNFα)之后,插入表达载体PSB-92中,使融合基因的5′端直接置于大肠肝菌PL启动子下游,采用30℃培养,42℃诱导,获得了TNF与preS1(1-65)融合蛋白的表达产物。SDS-PAGE电泳显示表达产物为25kD,约占细菌总蛋白的35%。表达产物经Westernblot验证,能分别特异地与hTNFα抗体与preS1抗体结合,稀释复性后,该融合蛋白还具有TNF的生理功能(对L929细胞的细胞毒活性)。经DNA序列测定,preS1(1-65)肽基因正确地融合在hTNFα基因之后。该结果提供了一种制备preS1的新方法,为进一步开展治疗肝癌和乙肝的导向药物打下基础。 相似文献
993.
Chine tomato yellow leaf curl virus (TYLCV-CHI) and other geminiviruses were analysed with 20 monoclonaI antibodies. It was shown that TYLCV-CHI is serclogicaIly close to Chinese tabacco Ieaf curl virus (TbLCV-CHI). The fragment of TYLCV-CHI DNA including the common region (CR), N-terminal of coat protein gene and AV1 gene was amplified by PCR and cloned, and its DNA sequence was determined. These raults showed that TYLCV-CHI is different from other known geminiviruses in the world, and is a new whitefly-transmitted gerninivirus. 相似文献
994.
It was show11 that nuclear reassembly was induced by small pieces of DNA fragments in cell-free extracts ofXenopus. In an attempt to learn the relationship between the nuclear reassembly and nucleosome/chromatin assembly, limited amounts of CM-Cellulose are used to eliminate the capacity of the egg extract S-150 to assemble chromatin. while the forming of nucleosomes is checked with DNA supercoiling by plasmid DNA pBR322 incubated in the extract, and further analysed by micrococcal nuclease digestion. This depleted extract is then used to induce nuclear reassembly around demembraned sperms with membrane vesicles. It is found that CM-Cellulose depletes histones H2A and H2B efficiently and blocks the assembly of nucleosomes, the demembraned sperms are yet reconstituted into nuclei in the treated S-150, although the chromatin in reassembled nuclei does not produce protected DNA fragments when digested with micrococcal nuclease. It suggests that in the cell-free system ofXenopus, DNA can be formed into nuclei without assembly of nucleosomes or chromatin. 相似文献
995.
Joanna Olsson Bo Karlberg Krister Kristensson Fredrik berg 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,707(1-2)
A method for determination of malondialdehyde with capillary electrophoresis using UV detection at 267 nm has been developed. The buffer system consisted of 10 mM borax and 0.5 mM CTAB at pH 9.3. Malondialdehyde migrated as the first peak in the electropherogram at 2.6 min. Limit of detection was 1.2 μM corresponding to 7.8 pg. Malondialdehyde was determined before and after stimulating lipid peroxidation with the addition of ferrous ammonium sulphate to homogenates of rat brain tissue. Proteins were precipitated by boiling and removed from the brain homogenates with centrifugation. No further pretreatment was made before injecting the homogenates on the CE system. Non-precipitated homogenates could also be analyzed, but this required washing of the capillary with 0.1 M NaOH before introduction of the next sample. 相似文献
996.
997.
A mechanism for the establishment of polar cell morphology is presented, based on the internal forces that the cytoskeletal
structures exert on the cell boundary. Cell shapes are determined by postulating that they correspond to the minimum of the
total energy of the system, which is the sum of the bending energy of the cell boundary and the potential energies of the
involved forces. Axisymmetrical cell shapes are considered, and it is assumed that the cytoskeletal structures exert an extensional
axial force and are involved in controlling the area of the cell boundary. The dependence of cell shapes on the axial force
is presented for different values of this area. The results show that, at increasing axial force, the cell undergoes a discontinuous
transition from an oval shape, exhibiting an equatorial mirror symmetry into a polar shape. The proposed mechanism is related
to previously documented specific effects of microtubule- and actin-modifying drugs on polar shapes of developing isolated
retinal photoreceptor cells.
Received: 28 January 1998 / Revised version: 25 July 1998 / Accepted: 29 July 1998 相似文献
998.
Liver mitochondrial and microsomal DT-diaphorase have been purified from 3-methylcholanthrene-treated rats. A 1150-fold and 3500-fold purification of mitochondrial and microsomal DT-diaphorase, respectively, is achieved after solubilization of the membranes with deoxycholate followed by affinity chromatography on azodicoumarol Sepharose 6B and subsequent gel filtration on Sephadex G-100. From this purification procedure, 65–70% of mitochondrial DT-diaphorase is recovered and the purified enzyme has a specific activity comparable to that of cytosolic DT-diaphorase; i.e., 50.4 kat/kg protein. Microsomal DT-diaphorase is obtained with a yield of 45% and a specific activity of 15.5 kat/kg protein.Purified mitochondrial DT-diaphorase exhibits an absorption spectrum characteristic of a flavoprotein and very similar to that of the cytosolic enzyme. Purification of both mitochondrial and microsomal DT-diaphorase results in fractions enriched in a polypeptide with a molecular weight of 28,000 which comigrates with purified cytosolic DT-diaphorase on SDS-polyacrylamide gel electrophoresis. Employing antiserum raised against cytosolic DT-diaphorase, immunological identity between DT-diaphorase isolated from the three cell fractions is observed with both the Ouchterlony immunodiffusion technique and fused rocket immunoelectrophoresis. The latter method also reveals that DT-diaphorase isolated from mitochondria and microsomes contains several antigenic forms identical to those observed in purified cytosolic DT-diaphorase. Furthermore, this antiserum inhibits DT-diaphorase to about the same extent whether the enzyme is isolated from mitochondria, microsomes, or cytosol. In addition, this antiserum efficiently inhibits membrane-bound microsomal DT-diaphorase. 相似文献
999.
目的:探讨血浆取代血清检测乙肝标志物的检测结果以及临床意义。方法:选取我科检测乙肝标志物的血样30份,分别放在抗凝剂管和普通干燥试管,采用全自动酶免疫分析仪检测HBsAg,将检测结果进行OD及S/CO值统计处理,并进行比较分析。结果:血清与二种血浆检测结果相关系数均0.99,二种血浆与血清结果相关关系良好(P〉0.0 5),无显著性差异。结论:血浆代替血清完全可以用于全自动酶标分析仪进行检测,既可以节省预处理时间,又可以减少标本在分离吸移血清过程中出现差错,值得临床推广和应用。 相似文献
1000.
Protein kinase FgSch9 serves as a mediator of the target of rapamycin and high osmolarity glycerol pathways and regulates multiple stress responses and secondary metabolism in Fusarium graminearum 下载免费PDF全文
Qin Gu Chengqi Zhang Fangwei Yu Yanni Yin Won‐Bo Shim Zhonghua Ma 《Environmental microbiology》2015,17(8):2661-2676
Saccharomyces cerevisiae protein kinase Sch9 is one of the downstream effectors of the target of rapamycin (TOR) complex 1 and plays multiple roles in stress resistance, longevity and nutrient sensing. However, the functions of Sch9 orthologs in filamentous fungi, particularly in pathogenic species, have not been characterized to date. Here, we investigated biological and genetic functions of FgSch9 in Fusarium graminearum. The FgSCH9 deletion mutant (ΔFgSch9) was defective in aerial hyphal growth, hyphal branching and conidial germination. The mutant exhibited increased sensitivity to osmotic and oxidative stresses, cell wall‐damaging agents, and to rapamycin, while showing increased thermal tolerance. We identified FgMaf1 as one of the FgSch9‐interacting proteins that plays an important role in regulating mycotoxin biosynthesis and virulence of F. graminearum. Co‐immunoprecipitation and affinity capture‐mass spectrometry assays showed that FgSch9 also interacts with FgTor and FgHog1. More importantly, both ΔFgSch9 and FgHog1 null mutant (ΔFgHog1) exhibited increased sensitivity to osmotic and oxidative stresses. This defect was more severe in the FgSch9/FgHog1 double mutant. Taken together, we propose that FgSch9 serves as a mediator of the TOR and high osmolarity glycerol pathways, and regulates vegetative differentiation, multiple stress responses and secondary metabolism in F. graminearum. 相似文献