全文获取类型
收费全文 | 15945篇 |
免费 | 1399篇 |
国内免费 | 1619篇 |
出版年
2024年 | 45篇 |
2023年 | 243篇 |
2022年 | 604篇 |
2021年 | 895篇 |
2020年 | 679篇 |
2019年 | 756篇 |
2018年 | 720篇 |
2017年 | 527篇 |
2016年 | 680篇 |
2015年 | 1009篇 |
2014年 | 1166篇 |
2013年 | 1284篇 |
2012年 | 1536篇 |
2011年 | 1293篇 |
2010年 | 797篇 |
2009年 | 759篇 |
2008年 | 823篇 |
2007年 | 694篇 |
2006年 | 609篇 |
2005年 | 554篇 |
2004年 | 397篇 |
2003年 | 397篇 |
2002年 | 357篇 |
2001年 | 245篇 |
2000年 | 211篇 |
1999年 | 239篇 |
1998年 | 134篇 |
1997年 | 144篇 |
1996年 | 138篇 |
1995年 | 123篇 |
1994年 | 118篇 |
1993年 | 90篇 |
1992年 | 96篇 |
1991年 | 74篇 |
1990年 | 82篇 |
1989年 | 61篇 |
1988年 | 58篇 |
1987年 | 43篇 |
1986年 | 50篇 |
1985年 | 50篇 |
1984年 | 33篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
A functional update of the Escherichia coli K-12 genome 总被引:1,自引:0,他引:1
Serres MH Gopal S Nahum LA Liang P Gaasterland T Riley M 《Genome biology》2001,2(9):research0035.1-research00357
Background
Since the genome of Escherichia coli K-12 was initially annotated in 1997, additional functional information based on biological characterization and functions of sequence-similar proteins has become available. On the basis of this new information, an updated version of the annotated chromosome has been generated. 相似文献983.
984.
Multicolor fluorescent differential display 总被引:8,自引:0,他引:8
Differential display and DNA microarray have emerged as the two most popular methods for gene expression profiling. Here, we developed a multicolor fluorescent differential display (FDD) method that combines the virtues of both differential display in signal amplification and DNA microarray in signal analysis. As in DNA microarray, RNA samples being compared can be labeled with either a red or green fluorescent dye and displayed in a single lane, allowing convenient scoring and quantification of the differentially expressed messages. In addition, the multicolor FDD has a built-in signal proofreading capability that is achieved by labeling each RNA sample from a comparative study with both red and green fluorescent dyes followed by their reciprocal mixings in color. Thus, the multicolor FDD provides a platform upon which a sensitive and accurate gene expression profiling by differential display can be automated and digitally analyzed. It is envisioned that cDNAs generated by the multicolor FDD may also be used directly as probes for DNA microarray, allowing an integration of the two most widely used technologies for comprehensive analysis of gene expression. 相似文献
985.
CD20, high-affinity IgE receptor beta chain (FcepsilonRIbeta), and HTm4 are structurally related cell-surface proteins expressed by hematopoietic cells. In the current study, 16 novel human and mouse genes that encode new members of this nascent protein family were identified. All family members had at least four potential membrane-spanning domains, with N- and C-terminal cytoplasmic domains. This family was therefore named the membrane-spanning 4A gene family, with at least 12 subgroups (MS4A1 through MS4A12) currently representing at least 21 distinct human and mouse proteins. Each family member had unique patterns of expression among hematopoietic cells and nonlymphoid tissues. Four of the 6 human MS4A genes identified in this study mapped to chromosome 11q12-q13.1 along with CD20, FcepsilonRIbeta, and HTm4. Thus, like CD20 and FcepsilonRIbeta, the other MS4A family members are likely to be components of oligomeric cell surface complexes that serve diverse signal transduction functions. 相似文献
986.
Hsu YM Chiu CT Wang CC Chien CS Luo SF Hsiao LD Liang KY Yang CM 《Cellular signalling》2001,13(9):633-643
Inhalation of tumour necrosis factor-alpha (TNF-alpha) induced a bronchial hyperreactivity to contractile agonists. However, the mechanisms of TNF-alpha involved in the pathogenesis of bronchial hyperreactivity were not completely understood. Therefore, we investigated the effect of TNF-alpha on bradykinin (BK)-induced inositol phosphate (IP) accumulation and Ca(2+) mobilization, and up-regulation of BK receptor density in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with TNF-alpha potentiated BK-induced IP accumulation and Ca(2+) mobilization. However, there was no effect on the IP response induced by endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT), and carbachol. Pretreatment with PDGF B-chain homodimer (PDGF-BB) also enhanced BK-induced IP response. These enhancements induced by TNF-alpha and PDGF-BB might be due to an increase in BK B(2) receptor density (B(max)), since [3H]BK binding to TSMCs was inhibited by the B(2) selective agonist and antagonist, BK and Hoe 140, but not by the B(1) selective reagents. The enhancing effects of TNF-alpha and PDGF-BB were attenuated by PD98059 (an inhibitor of activation of MAPK kinase, MEK) and cycloheximide (an inhibitor of protein synthesis), suggesting that TNF-alpha may share a common signalling pathway with PDGF-BB via protein(s) synthesis in TSMCs. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed p42/p44 mitogen-activated protein kinase (MAPK) activation induced by TNF-alpha and PDGF-BB and attenuated the effect of TNF-alpha on BK-induced IP response, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by TNF-alpha might be, at least in part, mediated through activation of Ras/Raf/MEK/MAPK pathway in TSMCs. 相似文献
987.
988.
Karimi-Busheri F Marcoux Y Tredget EE Li L Zheng J Ghoreishi M Weinfeld M Ghahary A 《Journal of cellular biochemistry》2002,86(4):737-747
Annexin II is a multifunctional calcium-dependent phospholipid binding protein whose presence in epidermis has previously been reported. However, like other members of annexin family, annexin II has been regarded as either an intracellular protein or associated with the cellular membrane. Here, we report the presence of a releasable annexin II and p11, two monomers of annexin II tetramer, in keratinocyte-conditioned medium (KCM). Proteins present in KCM were fractionated on a gel filtration column and following further evaluation, a releasable protein with apparent MW of 36 kDa was identified. Further characterization identified this protein as the p36 monomer of annexin II tetramer. The phospho-tyrosine antibody did not visualize this protein as the phosphorylated form of p36. Several experiments were conducted to examine whether this protein is soluble or associated with keratinocyte cell membranes in the conditioned medium. A centrifugation of conditioned medium was not able to bring this protein down into the pellet. Surprisingly, the results of Western analysis identified p36 and p11, two monomers of the annexin II tetramer, in conditioned medium derived from either keratinocytes cultured alone or keratinocytes co-cultured with fibroblasts. In contrast to the keratinocyte-conditioned medium in which annexin II was easily detectable, both monomers were barely detectable in conditioned medium collected from dermal fibroblasts. This finding was in contrast to the cell lysates in which p36 was detectable in both keratinocytes and fibroblasts. However, the amount of this protein was markedly higher in keratinocyte lysate relative to that of dermal fibroblasts. Conditioned medium derived from keratinocyte established from adult showed a higher level of annexin II compared to that of keratinocytes established from newborn babies. The expression of p11 seems to increase with differentiation of keratinocytes derived from either adult or newborn skin samples. When the site of annexin synthesis in human skin was examined by immunohistochemical staining, the antibody for p36 localized the annexin to the keratinocyte cell members in the basal and suprabasal keratinocytes. In conclusion, Western blot detection of both p36 and p11 in conditioned medium from skin cells revealed that human keratinocytes, but not fibroblasts, express a releasable monomer form of annexin II which is regulated by differentiation status of keratinocytes. This finding is consistent with the localization of annexin II detected by immunohistochemical staining. 相似文献
989.
A decade of differential display 总被引:23,自引:0,他引:23
Liang P 《BioTechniques》2002,33(2):338-44, 346
It has been 10 years since the invention of differential display (DD), a conceptually simple methodology that allows the detection and identification of differentially expressed genes. In the past decade, the number of publications describing successful applications of DD has outnumbered those using any other competing methodologies, including subtractive hybridization, representational difference analysis, serial analysis of gene expression, and DNA microarrays. This review will provide a glimpse of the current progress made in DD technological development, refinement, and automation. Excellent examples of DD applications in studying a variety of biological problems, in such diverse biological systems as bacteria, yeast, flies, plants, and higher mammals, are presented to provide a roadmap for those who would like to pursue a fruitful gene "fishing" expedition. Some of the fundamental differences between DD and DNA microarrays are also discussed. 相似文献
990.
In chromosomes of metazoa, the assembly of the genome into chromatin makes an important but poorly understood contribution to determining where DNA replication will initiate. We addressed this issue by studying the developmental progression of the location of the DNA replication origin (ORI) and alterations in chromatin structure in one of the best-mapped ORIs in metazoa, that found in DNA puff II/9A of the fly Sciara coprophila. We found that DNA synthesis for both normal chromosomal endoduplication and DNA amplification initiates within the same 5.5 kb EcoRI fragment. We showed that irrespective of the mode of ORI function--replication or amplification--chromatin over the 1 kb major ORI is never remodeled into a conventional DNase I hypersensitive site (DH site). Instead, we found that the major site of alterations to chromatin structure at this locus is a large (approximately 400 bp) DH site located 600 bp away from the major ORI, at a position where the frequency of replication initiation events falls dramatically. We describe a tight positive correlation between ORI activity, strength of this DH site, and the intranuclear titer of protein factor(s) that bind the DH site in a sequence-specific manner. We propose that the Sciara replicator in locus II/9A is composed of sequences that reside within the ORI per se as well as sequences encompassed by the DH site. 相似文献