全文获取类型
收费全文 | 7857篇 |
免费 | 784篇 |
国内免费 | 4篇 |
出版年
2023年 | 53篇 |
2022年 | 43篇 |
2021年 | 242篇 |
2020年 | 149篇 |
2019年 | 178篇 |
2018年 | 203篇 |
2017年 | 163篇 |
2016年 | 342篇 |
2015年 | 526篇 |
2014年 | 540篇 |
2013年 | 554篇 |
2012年 | 776篇 |
2011年 | 671篇 |
2010年 | 389篇 |
2009年 | 383篇 |
2008年 | 512篇 |
2007年 | 441篇 |
2006年 | 396篇 |
2005年 | 304篇 |
2004年 | 306篇 |
2003年 | 273篇 |
2002年 | 254篇 |
2001年 | 69篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 63篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 25篇 |
1989年 | 38篇 |
1988年 | 60篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 28篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1975年 | 20篇 |
1974年 | 16篇 |
1970年 | 16篇 |
1967年 | 14篇 |
排序方式: 共有8645条查询结果,搜索用时 15 毫秒
61.
Yuejia Dang Yi Wei Yanyan Wang Shaoshuai Liu Chekanova Julia Shi-Hong Zhang 《Environmental microbiology》2021,23(9):4881-4895
ATP-dependent Lon proteases function in bacterial pathogenesis by regulating the expression of the Type III secretion system; however, little is known about how Lon proteases regulate fungal pathogenesis. We previously investigated Lon-binding proteins involved in fungal pathogenesis that interact with PrePL, the smallest Magnaporthe oryzae Lon-binding protein. Here, we show that Lon cleaves PrePL and produces Pc, an extracellular 11-kDa isoform with catalase and peroxidase activity. The ΔPrePL loss-of-function strain showed stronger sporulation and accelerated disease development, suggesting a temporally specific negative regulatory mechanism controlled by PrePL in disease progression. Neither the truncated Pc, nor the full-length PrePL missing the Lon cleavage site complemented the ΔPrePL phenotype, suggesting that full-length PrePL and Pc both function in fungal development. PrePL targeted to the mitochondria undergoes hydrolysis by Lon to produce Pc, which accumulates in the fungal apoplast. Importantly, recombinant Pc induced plant defence responses and cell death after being infiltrated into selected plant leaves, indicating that it functions as an avirulence factor. This work thus reveals a novel pathogenic factor in the fungal Lon-mediated pathway. Additionally, our results provide new insight into the functions of a full-length protein and its cleaved isoform in fungal pathogenesis. 相似文献
62.
Cyprian Wejnert Binh Le Charles E. Rose Alexandra M. Oster Amanda J. Smith Julia Zhu Gabriela Paz-Bailey for the NHBS Study Group 《PloS one》2013,8(10)
Over half of HIV infections in the United States occur among men who have sex with men (MSM). Awareness of infection is a necessary precursor to antiretroviral treatment and risk reduction among HIV-infected persons. We report data on prevalence and awareness of HIV infection among MSM in 2008 and 2011, using data from 20 cities participating in the 2008 and 2011 National HIV Behavioral Surveillance System (NHBS) among MSM. Venue-based, time-space sampling was used to recruit men for interview and HIV testing. We analyzed data for men who reported ≥1 male sex partner in the past 12 months. Participants who tested positive were considered to be aware of their infection if they reported a prior positive HIV test. We used multivariable analysis to examine differences between results from 2011 vs. 2008. HIV prevalence was 19% in 2008 and 18% in 2011 (p = 0.14). In both years, HIV prevalence was highest among older age groups, blacks, and men with lower education and income. In multivariable analysis, HIV prevalence did not change significantly from 2008 to 2011 overall (p = 0.51) or in any age or racial/ethnic category (p>0.15 in each category). Among those testing positive, a greater proportion was aware of their infection in 2011 (66%) than in 2008 (56%) (p<0.001). In both years, HIV awareness was higher for older age groups, whites, and men with higher education and income. In multivariable analysis, HIV awareness increased from 2008 to 2011 overall (p<0.001) and for all age and racial/ethnic categories (p<0.01 in each category). In both years, black MSM had the highest HIV prevalence and the lowest awareness among racial/ethnic groups. These findings suggest that HIV-positive MSM are increasingly aware of their infections. 相似文献
63.
Populations of large carnivores can persist in mountainous environments following extensive land use change and the conversion of suitable habitat for agriculture and human habitation in lower lying areas of their range. The significance of these populations is poorly understood, however, and little attention has focussed on why certain mountainous areas can hold high densities of large carnivores and what the conservation implications of such populations might be. Here we use the leopard (Panthera pardus) population in the western Soutpansberg Mountains, South Africa, as a model system and show that montane habitats can support high numbers of leopards. Spatially explicit capture-recapture (SECR) analysis recorded the highest density of leopards reported outside of state-protected areas in sub-Saharan Africa. This density represents a temporally high local abundance of leopards and we explore the explanations for this alongside some of the potential conservation implications. 相似文献
64.
Simon Trapp Ali A. Aghdassi Juliane Glaubitz Matthias Sendler Frank Ulrich Weiss Jens Peter Kühn Marie-Luise Kromrey Ujjwal M. Mahajan Petra Pallagi Zoltán Rakonczay Jr Viktória Venglovecz Markus M. Lerch Peter Hegyi Julia Mayerle 《Journal of cellular and molecular medicine》2021,25(10):4658-4670
Mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR) are an established risk factor for cystic fibrosis (CF) and chronic pancreatitis. Whereas patients with CF usually develop complete exocrine pancreatic insufficiency, pancreatitis patients with CFTR mutations have mostly preserved exocrine pancreatic function. We therefore used a strain of transgenic mice with significant residual CFTR function (CFTRtm1HGU) to induce pancreatitis experimentally by serial caerulein injections. Protease activation and necrosis were investigated in isolated acini, disease severity over 24h, pancreatic function by MRI, isolated duct stimulation and faecal chymotrypsin, and leucocyte function by ex vivo lipopolysaccharide (LPS) stimulation. Pancreatic and lung injury were more severe in CFTRtm1HGU but intrapancreatic trypsin and serum enzyme activities higher than in wild-type controls only at 8h, a time interval previously attributed to leucocyte infiltration. CCK-induced trypsin activation and necrosis in acini from CFTRtm1HGU did not differ from controls. Fluid and bicarbonate secretion were greatly impaired, whereas faecal chymotrypsin remained unchanged. LPS stimulation of splenocytes from CFTRtm1HGU resulted in increased INF-γ and IL-6, but decreased IL-10 secretion. CFTR mutations that preserve residual pancreatic function significantly increase the severity of experimental pancreatitis—mostly via impairing duct cell function and a shift towards a pro-inflammatory phenotype, not by rendering acinar cells more susceptible to pathological stimuli. 相似文献
65.
Micka?l Lecomte Latifa Hamama Linda Voisine Julia Gatto Jean-Jacques Hélesbeux Denis Séraphin Luis M. Pe?a-Rodriguez Pascal Richomme Cora Boedo Claire Yovanopoulos Melvina Gyomlai Mathilde Briard Philippe Simoneau Pascal Poupard Romain Berruyer 《PloS one》2014,9(7)
Although different mechanisms have been proposed in the recent years, plant pathogen partial resistance is still poorly understood. Components of the chemical warfare, including the production of plant defense compounds and plant resistance to pathogen-produced toxins, are likely to play a role. Toxins are indeed recognized as important determinants of pathogenicity in necrotrophic fungi. Partial resistance based on quantitative resistance loci and linked to a pathogen-produced toxin has never been fully described. We tested this hypothesis using the Alternaria dauci – carrot pathosystem. Alternaria dauci, causing carrot leaf blight, is a necrotrophic fungus known to produce zinniol, a compound described as a non-host selective toxin. Embryogenic cellular cultures from carrot genotypes varying in resistance against A. dauci were confronted with zinniol at different concentrations or to fungal exudates (raw, organic or aqueous extracts). The plant response was analyzed through the measurement of cytoplasmic esterase activity, as a marker of cell viability, and the differentiation of somatic embryos in cellular cultures. A differential response to toxicity was demonstrated between susceptible and partially resistant genotypes, with a good correlation noted between the resistance to the fungus at the whole plant level and resistance at the cellular level to fungal exudates from raw and organic extracts. No toxic reaction of embryogenic cultures was observed after treatment with the aqueous extract or zinniol used at physiological concentration. Moreover, we did not detect zinniol in toxic fungal extracts by UHPLC analysis. These results suggest that strong phytotoxic compounds are present in the organic extract and remain to be characterized. Our results clearly show that carrot tolerance to A. dauci toxins is one component of its partial resistance. 相似文献
66.
Human non-hairy (glabrous) skin of the fingers, palms and soles wrinkles after prolonged exposure to water. Wrinkling is a sympathetic nervous system-dependent process but little is known about the physiology and potential functions of water-induced skin wrinkling. Here we investigated the idea that wrinkling might improve handling of wet objects by measuring the performance of a large cohort of human subjects (n = 40) in a manual dexterity task. We also tested the idea that skin wrinkling has an impact on tactile acuity or vibrotactile sensation using two independent sensory tasks. We found that skin wrinkling did not improve dexterity in handling wet objects nor did it affect any aspect of touch sensitivity measured. Thus water-induced wrinkling appears to have no significant impact on tactile driven performance or dexterity in handling wet or dry objects. 相似文献
67.
The present study has examined the role of the serine/threonine kinase LKB1 in the survival and differentiation of CD4/8 double positive thymocytes. LKB1-null DPs can respond to signals from the mature α/β T-cell-antigen receptor and initiate positive selection. However, in the absence of LKB1, thymocytes fail to mature to conventional single positive cells causing severe lymphopenia in the peripheral lymphoid tissues. LKB1 thus appears to be dispensable for positive selection but important for the maturation of positively selected thymocytes. LKB1 also strikingly prevented the development of invariant Vα14 NKT cells and innate TCR αβ gut lymphocytes. Previous studies with gain of function mutants have suggested that the role of LKB1 in T cell development is mediated by its substrate the AMP-activated protein kinase (AMPK). The present study now analyses the impact of AMPK deletion in DP thymocytes and shows that the role of LKB1 during the development of both conventional and innate T cells is mediated by AMPK-independent pathways. 相似文献
68.
69.
70.