全文获取类型
收费全文 | 3025篇 |
免费 | 207篇 |
国内免费 | 4篇 |
专业分类
3236篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 27篇 |
2021年 | 41篇 |
2020年 | 36篇 |
2019年 | 69篇 |
2018年 | 76篇 |
2017年 | 81篇 |
2016年 | 115篇 |
2015年 | 203篇 |
2014年 | 186篇 |
2013年 | 230篇 |
2012年 | 294篇 |
2011年 | 290篇 |
2010年 | 181篇 |
2009年 | 126篇 |
2008年 | 195篇 |
2007年 | 173篇 |
2006年 | 150篇 |
2005年 | 117篇 |
2004年 | 160篇 |
2003年 | 140篇 |
2002年 | 110篇 |
2001年 | 36篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有3236条查询结果,搜索用时 0 毫秒
61.
Summary Additon of pyruvate or leucine was found to be efficient for increasing the intracellular ratios of NADH/NAD and NADPH/NADP while reducing the coenzyme A concentration during the cultivation of Alcaligenes eutrophus. Poly--hydroxybutyrate (PHB) accumulation was enhanced more than 2-fold since metabolic flux of acetyl-CoA into PHB synthetic pathway could be facilitated by the changes of the cofactor concentrations. 相似文献
62.
The ultrastructural aspects ofCyperus iria leaves showing the C4 syndrome and the typical C3 species,Carex siderosticta, in the Cyperaceae family were examined.C. iria exhibited the chlorocyperoid type, showing an unusual Kranz structure with vascular bundles completely surrounded by two
bundle sheaths. The cellular components of the inner Kranz bundle sheath cells were similar to those found in the NADP-ME
C4 subtype, having centrifugally arranged chloroplasts with greatly reduced grana and numerous starch grains. Their chloroplasts
contained convoluted thyla-koids and a weakly-developed peripheral reticulum, although it was extensive mostly in mesophyll
cell chloroplasts. The outer mestome bundle sheath layer was sclerenchymatous and generally devoid of organelles, but had
unevenly thickened walls. Suberized lamellae were present on its cell walls, and they became polylamellate when traversed
by plasmodesmata. Mesophyll cell chloroplasts showed well-stacked grana with small starch grains. InC. siderosticta, vascular bundles were surrounded by the inner mestome sheath and the outer parenchymatous bundle sheath with intercellular
spaces. The mestome sheath cells degraded in their early development and remained in a collapsed state, although the suberized
lamellae retained polylamellate features. Plastids with a crystalline structure, sometimes membrane-bounded, were found in
the epidermal cells. The close interveinal distance was 35–50 μm inC. iria, whereas it was 157–218 μm inC. siderosticta. These ultrastructural characteristics were discussed in relation to their photosynthetic functions. 相似文献
63.
Hye Suck An Jae Kwon Cho Kyong Min Kim Maeng Hyun Son Jeong In Myeong Chul Min An 《Genes & genomics.》2014,36(5):661-669
The seven-band grouper (Epinephelus septemfasciatus) is an important fishery resource of a target for prospective aquaculture diversification and maintenance of stock quality is thus important. To explore the sustainability of fry production, genetic variations in 83 seven-band groupers from two broodstock and offspring populations of a hatchery strain were analyzed using 13 polymorphic nuclear microsatellite DNA loci; 133 alleles were identified. Allelic variability ranged from 4 to 18 in the broodstock and from 3 to 11 in the offspring. The average observed and expected heterozygosities were 0.669 and 0.734 in broodstock and 0.674 and 0.649 in offspring, respectively. Although no statistically significant reductions in heterozygosity or allelic diversity were evident in offspring, considerable loss of rare alleles was apparent. The broodstock and offspring populations exhibited significant genetic differences (F ST = 0.033, P < 0.001) indicating that genetic drift has likely promoted differentiation between the two populations, which may have negative effects on sustainable fry production. Therefore, genetic variations between broodstock and offspring should be monitored, and inbreeding should be controlled, to ensure the success of commercial breeding programs. Our data provide a useful genetic basis for future planning of sustainable culture and management of E. septemfasciatus in fisheries. 相似文献
64.
H.S. Jun In K. Kim H.J. Lee H.J. Lee Jae H. Kang J.R. Kim Hyoung D. Shin J. Song 《Obesity (Silver Spring, Md.)》2009,17(2):355-362
To investigate the associations of uncoupling protein (UCP)2 and UCP3 gene variants with overweight and related traits, we genotyped UCP2−866G>A, UCP2Ala55Val, and UCP3−55C>T in 737 Korean children and 732 adults and collected data regarding anthropometric status and blood biochemistry. Information concerning the children's lifestyles and dietary habits was collected. The UCP2−866G>A and UCP3−55C>T gene variants showed significant associations with BMI level, waist circumference, and body weight in the children but not in the adults. Compared with −866GG carriers, the −866GA and AA carriers showed a strong decreasing trend in the risk for overweight (odds ratio (OR), 0.67; 95% confidence interval (CI), 0.45–1.01; P = 0.053). In comparison with UCP3−55CC carriers, children carrying −55CT and TT showed a significant reduction in the risk of overweight (OR, 0.67; 95% CI, 0.46–0.98; P = 0.039). There was also evidence of interactions between the effects of the combined UCP2−UCP3 genotype and obesity‐related metabolic traits. The greatest protective effect against overweight was seen in those with the combined genotype non‐UCP2−866GG and non‐UCP3−55CC, as compared with those carrying both UCP2−866GG and UCP3−55CC (OR, 0.60; 95% CI, 0.38–0.95; P = 0.030). In the subgroup with a low level of physical activity, UCP3−55CC carriers had higher BMI values than UCP3−55T carriers (16.6 ± 2.3 kg/m2 vs. 16.1 ± 1.9 kg/m2, P = 0.016). Low physical activity may aggravate the susceptibility to overweight in UCP2−866GG and UCP3−55CC carriers. 相似文献
65.
Kang‐Young Choi Hyun‐Jung Kim Byung‐Chae Cho In‐San Kim Hyun‐Jung Kim Hyun‐Mo Ryoo 《Journal of cellular biochemistry》2009,107(4):818-825
TGF‐β3, TβR‐I, and TGF‐β‐activated Smad2 has been suggested to be a series of signaling molecules for secondary palate fusion. In this article, we show that a gene induced by TGF‐β, βig‐h3, is coincidentally expressed with TGF‐β3 in medial edge epithelial (MEE) cells undergoing apoptosis during normal palatal fusion. βig‐h3 was also highly expressed in the areas of post‐weaning mammary gland cells and developing phalangeal joints in which TGF‐β3 or BMP‐4‐induced apoptosis occurs, respectively. Blocking of βig‐h3 expression in E12.5 embryos with antisense oligodeoxynucleotides (ODN) resulted in cleft of the secondary palate in 84% of the treated mice that were born. Moreover, the antisense ODN treatment resulted in a failure of apoptosis in the MEE between palatal shelves in physical contact in organ culture. We conclude that βig‐h3 expression in the MEE is stimulated by TGF‐β3, causes cell death, and consequently results in complete fusion of the apposed palatal shelves. J. Cell. Biochem. 107: 818–825, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
66.
Rosas M Liddiard K Kimberg M Faro-Trindade I McDonald JU Williams DL Brown GD Taylor PR 《Journal of immunology (Baltimore, Md. : 1950)》2008,181(5):3549-3557
Dectin-1 is the archetypal signaling, non-Toll-like pattern recognition receptor that plays a protective role in immune defense to Candida albicans as the major leukocyte receptor for beta-glucans. Dectin-1-deficiency is associated with impaired recruitment of inflammatory leukocytes and inflammatory mediator production at the site of infection. In this study, we have used mice to define the mechanisms that regulate the dectin-1-mediated inflammatory responses. Myeloid cell activation by dectin-1 is controlled by inherent cellular programming, with distinct macrophage and dendritic cell populations responding differentially to the engagement of this receptor. The inflammatory response is further modulated by the progression of the phagocytosis, with "frustrated phagocytosis" resulting in dramatically augmented inflammatory responses. These studies demonstrate that dectin-1 in isolation is sufficient to drive a potent inflammatory response in a context-dependent manner. This has implications for the mechanism by which myeloid cells are activated during fungal infections and the processes involved in the therapeutic manipulation of the immune system via exogenous dectin-1 stimulation or blockade. 相似文献
67.
Kyoungjune Pak Yun Hak Kim Sunghwan Suh Tae Sik Goh Dae Cheon Jeong Seong Jang Kim In Joo Kim Myoung‐Eun Han Sae‐Ock Oh 《Journal of cellular and molecular medicine》2019,23(4):3010-3015
As the importance of personalized therapeutics in aggressive papillary thyroid cancer (PTC) increases, accurate risk stratification is required. To develop a novel prognostic scoring system for patients with PTC (n = 455), we used mRNA expression and clinical data from The Cancer Genome Atlas. We performed variable selection using Network‐Regularized high‐dimensional Cox‐regression with gene network from pathway databases. The risk score was calculated using a linear combination of regression coefficients and mRNA expressions. The risk score and clinical variables were assessed by several survival analyses. The risk score showed high discriminatory power for the prediction of event‐free survival as well as the presence of metastasis. In multivariate analysis, the risk score and presence of metastasis were significant risk factors among the clinical variables that were examined together. In the current study, we developed a risk scoring system that will help to identify suitable therapeutic options for PTC. 相似文献
68.
69.
Faro-Trindade I Willment JA Kerrigan AM Redelinghuys P Hadebe S Reid DM Srinivasan N Wainwright H Lang DM Steele C Brown GD 《PloS one》2012,7(4):e35675
The innate recognition of fungi by leukocytes is mediated by pattern recognition receptors (PRR), such as Dectin-1, and is thought to occur at the cell surface triggering intracellular signalling cascades which lead to the induction of protective host responses. In the lung, this recognition is aided by surfactant which also serves to maintain the balance between inflammation and pulmonary function, although the underlying mechanisms are unknown. Here we have explored pulmonary innate recognition of a variety of fungal particles, including zymosan, Candida albicans and Aspergillus fumigatus, and demonstrate that opsonisation with surfactant components can limit inflammation by reducing host-cell fungal interactions. However, we found that this opsonisation does not contribute directly to innate fungal recognition and that this process is mediated through non-opsonic PRRs, including Dectin-1. Moreover, we found that pulmonary inflammatory responses to resting Aspergillus conidia were initiated by these PRRs in acidified phagolysosomes, following the uptake of fungal particles by leukocytes. Our data therefore provides crucial new insights into the mechanisms by which surfactant can maintain pulmonary function in the face of microbial challenge, and defines the phagolysosome as a novel intracellular compartment involved in the innate sensing of extracellular pathogens in the lung. 相似文献
70.
Seung Hyun Lee Young-Sun Lee In Yong Lee Jae Won Lim Hee-Kwan Shin Jae-Ran Yu Seobo Sim 《The Korean journal of parasitology》2012,50(4):327-331
Monthly surveys were conducted to investigate the occurrence of chigger mites and seroprevalence of scrub typhus among small mammals in Jeollanam-do, the southwestern part of Korea, from November 2006 through October 2007. Fifty-eight small mammals, including 57 Apodemus agrarius (98.3%) and 1 Crocidura lasiura (1.7%), were captured, and a total of 4,675 chigger mites representing 4 genera and 8 species were collected from them. The chigger infestation rate among small mammals was 69.0%. The most predominant species in A. agrarius was Leptotrombidium scutellare (54.0%), followed by Leptotrombidium pallidum (39.4%), Leptotrombidium orientale (4.4%), Leptotrombidium palpale (1.1%), Neotrombicula tamiyai (0.6%), Eushoengastia koreaensis (0.3%), Neotrombicula gardellai (0.3%), and Cheladonta ikaoensis (<0.1%). The chigger index of A. agrarius was the highest in October (740.0), followed by November (242.0), September (134.6), March (98.3), February (38.2), January (35.3), December (34.5), April (30.8), and May (1.7). The average antibody positive rate of scrub typhus in wild rodents was 50.0%. The seropositive rates were high in October (100.0%) and November (83.3%), whereas those in other months were relatively low (28.6-57.1%). The chigger index of L. scutellare rapidly increased in September to form an acuminate peak in October, followed by a gradual decline. These results suggest that the outbreak of scrub typhus in the southwestern part of Korean peninsula is mostly due to L. scutellare. 相似文献