全文获取类型
收费全文 | 9406篇 |
免费 | 892篇 |
国内免费 | 1篇 |
出版年
2023年 | 28篇 |
2022年 | 64篇 |
2021年 | 190篇 |
2020年 | 89篇 |
2019年 | 123篇 |
2018年 | 139篇 |
2017年 | 126篇 |
2016年 | 265篇 |
2015年 | 406篇 |
2014年 | 488篇 |
2013年 | 587篇 |
2012年 | 727篇 |
2011年 | 704篇 |
2010年 | 490篇 |
2009年 | 476篇 |
2008年 | 584篇 |
2007年 | 591篇 |
2006年 | 523篇 |
2005年 | 501篇 |
2004年 | 489篇 |
2003年 | 466篇 |
2002年 | 405篇 |
2001年 | 112篇 |
2000年 | 91篇 |
1999年 | 107篇 |
1998年 | 103篇 |
1997年 | 75篇 |
1996年 | 72篇 |
1995年 | 58篇 |
1994年 | 62篇 |
1993年 | 78篇 |
1992年 | 84篇 |
1991年 | 73篇 |
1990年 | 70篇 |
1989年 | 74篇 |
1988年 | 54篇 |
1987年 | 52篇 |
1986年 | 49篇 |
1985年 | 51篇 |
1984年 | 28篇 |
1983年 | 41篇 |
1982年 | 40篇 |
1981年 | 29篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 41篇 |
1974年 | 32篇 |
1973年 | 32篇 |
1972年 | 27篇 |
1970年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Ovsyannikova IG Jacobson RM Ryan JE Vierkant RA Pankratz VS Jacobsen SJ Poland GA 《Immunogenetics》2005,56(11):798-807
Measles virus-specific T cells and the production of cytokines play a critical role in the immune response following measles immunization. To understand the genetic factors that influence variation in IFN- and IL-4 responses following measles immunization and to provide insight into the factors influencing both cellular and humoral immunity to measles, we assessed associations between human leukocyte antigen (HLA) class II genes and measles-specific Th1 and Th2-type cytokine responses in peripheral blood lymphocytes from 339 children previously vaccinated with two doses of measles-mumps-rubella vaccine (MMR-II). Median values for measles-specific IFN- and IL-4 secretion levels were 40.73 and 9.71 pg/ml, respectively. The global tests suggested associations between measles-specific IFN- response and alleles of the DRB1 and DQB1 loci (P=0.07 and P=0.02, respectively). Specifically, DRB1*0301, *0901, and *1501 alleles were significantly associated with IFN- secretion. The alleles that suggested evidence of an HLA association with IL-4 secretion were DRB1*0103, *0701, and *1101. Th1 cytokine responses and DQB1 allele associations revealed that the alleles with the strongest association with IFN- secretion were DQB1*0201, *0303, *0402, and *0602. Specific alleles with a suggestive association with low measles-specific Th2 cytokine responses were DQB1*0202 and *0503. In addition, DPB1*0101, *0201, and *0601 alleles provided suggestive evidence of an HLA association with measles-induced IFN- response, while DPB1*0501 was associated with an IL-4 response. These data suggest that IFN- and IL-4 cytokine responses to measles may be genetically restricted in part by HLA class II genes, which in turn can restrict the cellular immune response to measles vaccine. 相似文献
992.
Immunologic significance of HLA class I genes in measles virus-specific IFN-γ and IL-4 cytokine immune responses 总被引:2,自引:0,他引:2
Ovsyannikova IG Ryan JE Vierkant RA Pankratz VS Jacobson RM Poland GA 《Immunogenetics》2005,57(11):828-836
The variability of immune responses modulated by human leukocyte antigen (HLA) genes and secreted cytokines is a significant
factor in the development of a protective effect of measles vaccine. We studied the association between type 1 helper T cells
(Th1)- and Th2-like cytokine immune responses and HLA class I alleles among 339 schoolchildren who previously received two
doses of the measles vaccine. Median values for measles-specific interferon gamma (IFN-γ) and interleukin-4 (IL-4) cytokines
were 40.7 pg/ml [interquartile range (IQR) 8.1–176.7] and 9.7 pg/ml (IQR 2.8–24.3), respectively. Class I HLA-A (*0101 and
*3101) and HLA-Cw (*0303 and *0501) alleles were significantly associated with measles-virus-induced IFN-γ secretion. HLA-A*3101
and Cw*0303 were associated with a higher median IFN-γ response, while A*0101 and Cw*0501 were associated with lower measles-specific
IFN-γ response. We found limited associations between HLA class I gene polymorphisms and Th2-like (IL-4) immune responses
after measles vaccination, indicating that HLA class I molecules may have a limited effect on measles-vaccine-induced IL-4
secretion. Understanding the genetic factors that influence variations in cytokine secretion following measles vaccination
will provide insight into the factors that influence both cell-mediated and humoral immunity to measles. 相似文献
993.
Development of Temporal Temperature Gradient Electrophoresis for Characterising Methanogen Diversity 总被引:2,自引:0,他引:2
Temporal temperature gradient electrophoretic (TTGE) analysis of 16S rDNA sequences was optimized to monitor the methanogen
population present in water and sediments of a small eutrophic lake, Priest Pot, in the English Lake district. The production
of nonrepresentative TTGE profiles due to the generation of polymerase chain reaction (PCR) artifacts initially proved problematical.
The use of a proofreading polymerase in the PCR was found to be essential and fully optimized protocols were established and
tested to ensure confidence that the TTGE profiles truly reflected sequence diversity. TTGE analysis revealed the methanogen
population to be less diverse in water than in sediment. The most genetic diversity was observed in TTGE profiles of sediment
DNA isolated in winter and the least was in sediment DNA isolated in summer. DNA sequencing analysis of bands recovered from
TTGE gels revealed the presence of two methanogen communities. One clustered with Methanosaeta species and the other with the Methanomicrobiales. Many sequences showed low DNA sequence similarity to known methanogens, suggesting that Priest Pot harbors previously undescribed
methanogen species. 相似文献
994.
Calcium (Ca2+) entry in cells is crucial for development and physiology of virtually all cell types. It acts as an intracellular (second) messenger to regulate a diverse array of cellular functions, from cell division and differentiation to cell death. Among candidates for Ca2+ entry in cells are-voltage-dependant Ca2+ channels (VDCCs), transient receptor potential (TRP)-related Ca2+ channels and store-operated Ca2+ (SOC) channels. Plasma membrane Ca2+-ATPases (PMCA) and Na+/Ca2+ exchanger (NCX) are mainly responsible for Ca2+ extrusion. These different Ca2+channels/transporters and exchangers exhibit specific distribution and physiological properties. During pregnancy, the syncytiotrophoblast layer of the human placenta transfers as much as 30 g of Ca2+ from the mother to the fetus, especially in late gestation where Ca2+ transport through different channels must increase in response to the demands of accelerating bone mineralization of the fetus. The identification and characterization of the different Ca2+ channels/transporters and exchangers on the brush-border membrane (BBM) facing the maternal circulation, and the basal plasma membrane (BPM) facing the fetal circulation; placental membrane of the syncytiotrophoblasts have been the focus of numerous studies. This review discusses current views in this field regarding localization and functions during transcellular Ca2+ entry and extrusion from cells particularly in the placenta. 相似文献
995.
Coupling between cell adhesion and the actin cytoskeleton is thought to require a stable link between the cadherin-catenin complex and actin that is mediated by alpha-catenin. In this issue of Cell, the Weis and Nelson groups call this static model into question, showing that alpha-catenin can directly regulate actin dynamics (Drees et al., 2005 and Yamada et al., 2005). 相似文献
996.
Brd2/RING3 interacts with a chromatin-binding domain in the Kaposi's Sarcoma-associated herpesvirus latency-associated nuclear antigen 1 (LANA-1) that is required for multiple functions of LANA-1
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Viejo-Borbolla A Ottinger M Brüning E Bürger A König R Kati E Sheldon JA Schulz TF 《Journal of virology》2005,79(21):13618-13629
997.
998.
Evidence for frequent reinfection with human immunodeficiency virus type 1 of a different subtype
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A major premise underlying current human immunodeficiency virus type 1 (HIV-1) vaccine approaches is that preexisting HIV-1-specific immunity will block or reduce infection. However, the recent identification of several cases of HIV-1 reinfection suggests that the specific immune response generated for chronic HIV-1 infection may not be adequate to protect against infection by a second HIV-1 strain. It has been unclear, though, whether these individuals are representative of the global epidemic or are rare cases. Here we show that in a population of high-risk women, HIV-1 reinfection occurs almost as commonly as first infections. The study was designed to detect cases of reinfection by HIV-1 of a different subtype and thus captured cases where there was considerable diversity between the first and second strain. In each case, the second virus emerged approximately 1 year after the first infection, and in two cases, it emerged when viral levels were high, suggesting that a well-established HIV-1 infection may provide little benefit in terms of immunizing against reinfection, at least by more-divergent HIV-1 variants. Our findings indicate an urgent need for studies of larger cohorts to determine the incidence and timing of both intersubtype and intrasubtype reinfection. 相似文献
999.
1000.
Jacobson GA Featherstone AM Townsend AT Lord R Peterson GM 《Biological trace element research》2005,107(3):213-220
Several recent analytical methods for determination of Se and selenoprotein P have involved high-performance liquid chromatography (HPLC) using heparin-affinity columns coupled to inductively coupled plasma-mass spectrometry (ICP-MS) for Se detection. HPLC-ICP-MS chromatography using tandem HPLC columns with ICP-MS detection was used to detect the major selenium-containing proteins in plasma (glutathione peroxidase, albumin, and selenoprotein P). The efficiency of HPLC separation of plasma selenoprotein P was investigated by analyzing HPLC fractions using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with immunoblot analysis. The HPLC fraction corresponding to selenoprotein P contained 25.1% of total selenoprotein P as measured by immunoblot analysis. The majority (74.9%) of total selenoprotein P found by immunoblot analysis was contained in the early HPLC fractions, consistent with either poor heparin affinity, which was not evident based on the HPLC-ICP-MS technique alone or nonspecific binding of the antibody. Immunoblot analysis of selenoprotein relies on antibodies binding to a selenoprotein P epitope, which might be preserved when selenoprotein P is broken down to release selenocysteine residues. Immunoblot methods overestimate selenoprotein P and are not suitable for determinations of intact selenoprotein P. 相似文献