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191.
Summary There is now considerable evidence implicating several peptides in the control of gastrointestinal epithelial cell proliferation and cell renewal. While some of these may act directly, many may be involved in regulating the powerful trophic effects of the intake and digestion of foold on the gut epithelium.—Several peptides have been associated with the regulation of intestinal cell proliferation. There is little doubt that gastrin is trophic to the stomach, but, its role in the rest of the gastrointestinal tract is debatable. Enteroglucagon has often been associated with increased intestinal epithelial proliferation, but at the moment all the evidence for this is circumstantial. The effects of peptide YY and bombesin warrant further study. The availability of recombinant epidermal growth factor (EGF) has recently enabled us to demonstrate a powerful trophic response to infused EGF throughout the gastrointestinal tract. The increasing availability of peptides will eventually allow the rigorous in vivo evaluation of the trophic role of these potentially very important peptides. 相似文献
192.
Paneth cells (PCs) were described over a century ago as granulated cells located at the base of small intestinal crypts,
the 'crypts of Lieberkühn.' Various histochemical staining procedures were developed that identified PCs based on their distinctive
granule staining pattern. Early on, PCs were proposed to perform a specialized function other than absorption of digested
nutrients, the predominant task of the small intestinal epithelium. Since then, many constituents of the PC granules have
been biochemically characterized. The presence of various granule-associated antimicrobial substances and their release upon
microbial challenge suggest that PCs function as specialized defense cells in the small intestine. Altered resistance to microbial
infection in animal models with disrupted or augmented PC function provides further support for the host defense role of PCs.
Other PC components suggest that PCs may also participate in the regulation of lumenal ionic composition, crypt development,
digestion, and intestinal inflammation.
Received 6 June 2001; received after revision 26 July 2001; accepted 27 July 2001 相似文献
193.
CD23 (the low-affinity IgE receptor) as a C-type lectin: a multidomain and multifunctional molecule 总被引:5,自引:0,他引:5
Kijimoto-Ochiai S 《Cellular and molecular life sciences : CMLS》2002,59(4):648-664
This review, regards the low-affinity receptor CD23 as a C-type lectin and compares it with other C-type lectins and C-type
lectin-like receptors. C-type lectins such as the asialoglycoprotein receptor, as well as the dendritic cell immunoreceptor
and the dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin on dendritic cell lectin, possess amino
acid sequences which interact with Ca++ and sugar, and many of them possess an endocytosis signal sequence that includes tyrosine or serine in the cytoplasmic region.
In contrast, natural killer receptors lack the Ca++ and sugar-binding amino acids but conserve homologous cysteines in the form of C-type lectin, and possess an immunoreceptor
tyrosine-based inhibitory motif in the cytoplasmic region which inhibits killer activity when they recognize the self major
histocompatibility (MHC) class I molecule. Since human CD23a form has a similar amino acid sequence, the possibility that
this sequence is an endocytosis signal or an ITIM is discussed. The function of the reverse RGD and RGD-binding inhibitory
peptide in human CD23 from the point of view of the relation between a C-type lectin and MHC class II molecules is also considered.
Received 21 May 2001; received after revision 28 November 2001; accepted 29 November 2001 相似文献
194.
Mass spectrometry for protein and peptide characterisation 总被引:5,自引:0,他引:5
Jonsson AP 《Cellular and molecular life sciences : CMLS》2001,58(7):868-884
Mass spectrometry has become an important analytical tool in biological and biochemical research. Its speed, accuracy and
sensitivity are unmatched by conventional analytical techniques. Identification of proteins and characterisation of their
primary structure is a rapidly growing field in the post-genomic era, where matrix-assisted laser desorption/ionisation time-of-flight
peptide mass fingerprinting combined with electrospray tandem mass spectrometry can efficiently solve many questions. Many
recently determined genomic sequences have not been characterised at the protein level. Analysis of the amino acid sequence
and characterisation of post-translational modifications are therefore important steps towards correlation of protein structure
with function. This review concerns methods, instrumentation and applications of mass spectrometry in protein and peptide
analysis.
Received 17 April 2001; accepted 19 April 2001 相似文献
195.
Hetian Lei Chengchao Shou Xiaoyin Liu Luowen He Jian Wu Beihai Jiang Meisheng Liu Junshan Yang 《科学通报(英文版)》2002,47(8):682-686
Vascular endothelial growth factor (VEGF) binding to its tyrosine kinase receptors (KDR/FLK1, Flt-1) induces angiogenesis.
In search of the peptides blocking VEGF binding to its receptor KDR/FLK1 to inhibit tumorangiogenesis and growth, we screened
a phage display peptide library with KDR as target protein, and some candidate peptides were isolated. In this study, we cloned
the DNA fragment coding the peptide K237 from the library, into a vector pQE42 to express fusion protein DHFR-K237 in E. coli M15. The affection of fusion protein DHFR-K237 on endothelial cell proliferation and angiogenesis was investigated. In vitro, DHFR-K237 could completely block VEGF binding to KDR and significantly inhibit the VEGF-mediated proliferation of the human
vascular endothelial cells. In vivo, DHFR-K237 inhibited angiogenesis in chick embryo chorioallantoric membrane and tumor growth in nude mice. These results
suggest that K237 is an effective antagonist of VEGF binding to KDR, and could be a potential agent for cancer biotherapy. 相似文献
196.
Two cDNAs of plastid division gene NtFtsZ1-1 and NtFtsZ1-2 are isolated from Nicotiana tabacum by RT-PCR and rapid amplification cDNA ends (RACE) method. Analysis of the deduced amino acid sequences encoded by NtFtsZ1-1 and NtFtsZ1-2 indicate that these two proteins possess the typical conservative motifs and GTP binding sites existing in all FtsZ proteins. The existence of putative plastid transit peptide in their N-terminal suggests that there are at least two transit-peptide containing FtsZ proteins in higher plants. Phylogenetic analysis based on amino acid sequences of FtsZ proteins also supports this interference. These two NtFtsZ genes demonstrate a similar expression pattern during the plant development, detected by Northern blot. Expression of NtFtsZ1-1 and NtFtsZ1-2 in E.coli interrupts the normal division process of host cells. These results suggest the diverse functions of FtsZ proteins in higher plants. 相似文献
197.
多肽药物的研究及应用进展 总被引:1,自引:0,他引:1
姚焕英 《陕西师范大学学报(自然科学版)》2002,(Z1)
在查阅文献的基础上,综述了国内外对重组蛋白或基因工程多肽药物研究的概况和实例,重点介绍了几种运用基因工程技术生产多肽药物的方法,并对多肽药物的研究前景进行了展望. 相似文献
198.
根据由精氨酸-甘氨酸-天冬氨酸组成的肽能抑制血小板聚集的机制,设计并合成了[5-(4-甲脒-苄基)-2,4-二氧代-咪唑烷-3-基]-乙酰基-L-天冬氨酰-L-缬氨酸(9)。生物试验结果表明:(9)抑制血小板聚集作用最强,其活性以IC_(50)值相比,强于类似物。 相似文献
199.
200.
CHENHui XUJiaxi XINBin HEMeiyu 《科学通报(英文版)》2005,50(9):853-857
This paper describes experience with the sequencing of synthetic segment peptides of gp41 which are used in trimeric peptides as potential peptide-based vaccines and as inhibitors to mimic the fusion state of gp41 in HIV infection using ESI/CID-FT-ICR MS. All b and y““ series ions are found in the CID spectra and the mass difference between the calculated and observed results is very slight. FT-ICR MS again shows its power in peptide sequencing, successfully helping us obtain the sequence of an unknown peptide. 相似文献