全文获取类型
收费全文 | 9226篇 |
免费 | 826篇 |
国内免费 | 17篇 |
出版年
2023年 | 42篇 |
2022年 | 110篇 |
2021年 | 159篇 |
2020年 | 115篇 |
2019年 | 144篇 |
2018年 | 197篇 |
2017年 | 186篇 |
2016年 | 265篇 |
2015年 | 479篇 |
2014年 | 484篇 |
2013年 | 598篇 |
2012年 | 730篇 |
2011年 | 658篇 |
2010年 | 430篇 |
2009年 | 413篇 |
2008年 | 572篇 |
2007年 | 515篇 |
2006年 | 454篇 |
2005年 | 418篇 |
2004年 | 390篇 |
2003年 | 352篇 |
2002年 | 324篇 |
2001年 | 185篇 |
2000年 | 168篇 |
1999年 | 135篇 |
1998年 | 81篇 |
1997年 | 68篇 |
1996年 | 53篇 |
1995年 | 76篇 |
1994年 | 44篇 |
1993年 | 52篇 |
1992年 | 86篇 |
1991年 | 74篇 |
1990年 | 79篇 |
1989年 | 83篇 |
1988年 | 80篇 |
1987年 | 76篇 |
1986年 | 64篇 |
1985年 | 73篇 |
1984年 | 52篇 |
1983年 | 44篇 |
1982年 | 34篇 |
1980年 | 29篇 |
1979年 | 47篇 |
1978年 | 43篇 |
1977年 | 29篇 |
1976年 | 41篇 |
1975年 | 32篇 |
1974年 | 32篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Genomic segments cloning and analysis of Cotesia plutellae polydnavirus using plasmid capture system
Choi JY Roh JY Kang JN Shim HJ Woo SD Jin BR Li MS Je YH 《Biochemical and biophysical research communications》2005,332(2):487-493
Cotesia plutellae polydnaviruses (CpBV) has a segmented genome consisting of multiple circular double stranded DNAs. Recently, we have developed an easy, simple, and convenient system based on Tn7 transposition in order to clone genomic segments of CpBV in Escherichia coli cell and designated plasmid capture system (PCS). The PCS donor-S transferred a pUC19 origin of replication and an ampicillin resistance marker into CpBV genomic DNA by in vitro transposition. Through PCS system, we were able to clone 53 genomic clones ranging from 0.1 to 25.5 kb and further they were classified into 29 segments by their sizes and restriction endonuclease patterns. Among them, a complete nucleotide sequence of CpBV-S28 segment was determined and 10 putative genes were predicted from this segment. Interestingly, 9 of 10 putative ORFs had high level of similarities with catalytic domain of protein tyrosine phosphatase. Also, ORF2807 showed similarity with EP1-like proteins of C. congregata polydnavirus. 相似文献
972.
973.
The call for the meeting which took place in Heidelberg 13 January 2005, resulted in a high number of contributions covering a diversity of topics: embryonal stem cell research; molecular signaling pathways; assay systems for primitive, mesenchymal and epithelial stem cells; markers for transdifferentiation; and theoretical considerations including biomathematical modeling of stem cell development. The program was rounded off by pre-clinical and clinical applications of stem cell therapies, including new mobilization agents, treatment of myocardial infarction and chemoprotective gene transfer to stem cells. 相似文献
974.
Bcl-2 expression suppresses mismatch repair activity through inhibition of E2F transcriptional activity 总被引:7,自引:0,他引:7
Youn CK Cho HJ Kim SH Kim HB Kim MH Chang IY Lee JS Chung MH Hahm KS You HJ 《Nature cell biology》2005,7(2):137-147
Bcl-2 stimulates mutagenesis after the exposure of cells to DNA-damaging agents. However, the biological mechanisms of Bcl-2-mediated mutagenesis have remained largely obscure. Here we demonstrate that the Bcl-2-mediated suppression of hMSH2 expression results in a reduced cellular capacity to repair mismatches. The pathway linking Bcl-2 expression to the suppression of mismatch repair (MMR) activity involves the hypophosphorylation of pRb, and then the enhancement of the E2F-pRb complex. This is followed by a decrease in hMSH2 expression. MMR has a key role in protection against deleterious mutation accumulation and in maintaining genomic stability. Therefore, the decreased MMR activity by Bcl-2 may be an underlying mechanism for Bcl-2-promoted oncogenesis. 相似文献
975.
Sung?Ho?Yoon Cheol-Goo?Hur Ho-Young?Kang Yeoun?Hee?Kim Tae?Kwang?Oh Jihyun?F?KimEmail author 《BMC bioinformatics》2005,6(1):184
Background
Pathogenicity islands (PAIs), distinct genomic segments of pathogens encoding virulence factors, represent a subgroup of genomic islands (GIs) that have been acquired by horizontal gene transfer event. Up to now, computational approaches for identifying PAIs have been focused on the detection of genomic regions which only differ from the rest of the genome in their base composition and codon usage. These approaches often lead to the identification of genomic islands, rather than PAIs. 相似文献976.
In SJL mice, growth of RcsX lymphoma cells induces an inflammatory response by stimulating V(beta)16+ T cells. During inflammation, various serum protein levels can increase (e.g., acute phase reactants) or decrease (e.g., albumin), and most of these altered proteins are thus potential biomarkers. Although blood plasma is a valuable and promising sample for biomarker discovery for diseases or for novel drug targets, its proteome is complex. To address this, we have focused on a comprehensive comparison of the plasma proteomes from normal and RcsX-tumor-bearing SJL mice using the 1D-Gel-LC-MS/MS method after removing albumin and immunoglobulins. This analysis resulted in the identification of a total of 1079 nonredundant mouse plasma proteins; more than 480 in normal and 790 in RcsX-tumor-bearing SJL mouse plasma. Of these, only 191 proteins were found in common. The molecular weights ranged from 2 to 876 kDa, covering the pI values between 4.22 and 12.09, and included proteins with predicted transmembrane domains. By comparing the plasma proteomic profile of normal and RcsX-tumor-bearing SJL mice, we found significant changes in the levels of many proteins in RcsX-tumor-bearing mouse plasma. Most of the up-regulated proteins were identified as acute-phase proteins (APPs). Also, several unique proteins i.e., haptoglobin, proteosome subunits, fetuin-B, 14-3-3 zeta, MAGE-B4 antigen, etc, were found only in the tumor-bearing mouse plasma; either secreted, shed by membrane vesicles, or externalized due to cell death. These results affirm the effectiveness of this approach for protein identification from small samples, and for comparative proteomics in potential animal models of human disorders. 相似文献
977.
Identification of microRNAs of the herpesvirus family 总被引:1,自引:0,他引:1
Pfeffer S Sewer A Lagos-Quintana M Sheridan R Sander C Grässer FA van Dyk LF Ho CK Shuman S Chien M Russo JJ Ju J Randall G Lindenbach BD Rice CM Simon V Ho DD Zavolan M Tuschl T 《Nature methods》2005,2(4):269-276
Epstein-Barr virus (EBV or HHV4), a member of the human herpesvirus (HHV) family, has recently been shown to encode microRNAs (miRNAs). In contrast to most eukaryotic miRNAs, these viral miRNAs do not have close homologs in other viral genomes or in the genome of the human host. To identify other miRNA genes in pathogenic viruses, we combined a new miRNA gene prediction method with small-RNA cloning from several virus-infected cell types. We cloned ten miRNAs in the Kaposi sarcoma-associated virus (KSHV or HHV8), nine miRNAs in the mouse gammaherpesvirus 68 (MHV68) and nine miRNAs in the human cytomegalovirus (HCMV or HHV5). These miRNA genes are expressed individually or in clusters from either polymerase (pol) II or pol III promoters, and share no substantial sequence homology with one another or with the known human miRNAs. Generally, we predicted miRNAs in several large DNA viruses, and we could neither predict nor experimentally identify miRNAs in the genomes of small RNA viruses or retroviruses. 相似文献
978.
979.
Moaddel R Yamaguchi R Ho PC Patel S Hsu CP Subrahmanyam V Wainer IW 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2005,818(2):263-268
Membranes from a stably transfected cell line that expresses the human organic cation 1 transporter (hOCT1) have been immobilized on the immobilized artificial membrane (IAM) liquid chromatographic stationary phase to form the hOCT1(+)-IAM stationary phase. Membranes from the parent cell line that does not express the hOCT1 were also immobilized to create the hOCT1(-)-IAM stationary phase. Columns were created using both stationary phases, and frontal displacement chromatography experiments were conducted using [(3)H]-methyl phenyl pyridinium ([(3)H]-MPP(+)) as the marker ligand and MPP(+), verapamil, quinidine, quinine, nicotine, dopamine and vinblastin as the displacers. The K(d) values calculated from the chromatographic studies correlated with previously reported K(i) values (r(2)=0.9987; p<0.001). The data indicate that the hOCT1(+)-IAM column can be used for the on-line determination of binding affinities to the hOCT1 and that these affinities are comparable to those obtained using cellular uptake studies. In addition, the chromatographic method was able to identify a previously undetected high affinity binding site for MPP(+) and to determine that hOCT1 bound (R)-verapamil to a greater extent than (S)-verapamil. 相似文献
980.
Caspases are a family of cysteine proteases with roles in cytokine maturation or apoptosis. Caspase-2 was the first pro-apoptotic caspase identified, but its functions in apoptotic signal transduction are still being elucidated. This study examined the regulation of the activity of caspase-2 using recombinant proteins and a yeast-based system. Our data suggest that for human caspase-2 to be active its large and small subunits must be separated. For maximal activity its prodomain must also be removed. Consistent with its proposed identity as an upstream caspase, caspase-2 could provoke the activation of caspase-7. Caspase-2 was not subject to inhibition by members of the IAP family of apoptosis inhibitors. 相似文献