全文获取类型
收费全文 | 780篇 |
免费 | 147篇 |
国内免费 | 4篇 |
专业分类
931篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 28篇 |
2020年 | 20篇 |
2019年 | 36篇 |
2018年 | 51篇 |
2017年 | 23篇 |
2016年 | 25篇 |
2015年 | 53篇 |
2014年 | 50篇 |
2013年 | 43篇 |
2012年 | 57篇 |
2011年 | 64篇 |
2010年 | 51篇 |
2009年 | 28篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 25篇 |
2005年 | 31篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 5篇 |
1970年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有931条查询结果,搜索用时 15 毫秒
51.
Manufacture of flame retardant foaming board from waste papers reinforced with phenol-formaldehyde resin 总被引:4,自引:0,他引:4
A new flame retardant and waterproof porous fiberboard was manufactured from waste newspapers by using a foaming agent and a reinforcing phenol-formaldehyde resin. To find the optimum conditions for forming fiberboard with high mechanical properties as well as flame retardant and waterproof characteristics, a series of experiments were performed with varying weight percentages of resin (w). The results indicate that the best quality of the fiberboard was obtained for w approximately 11%. 相似文献
52.
53.
Asymmetric localization is a prerequisite for inscuteable (insc) to function in coordinating and mediating asymmetric cell divisions in Drosophila. We show here that Partner of Inscuteable (Pins), a new component of asymmetric divisions, is required for Inscuteable to asymmetrically localize. In the absence of pins, Inscuteable becomes cytoplasmic and asymmetric divisions of neuroblasts and mitotic domain 9 cells show defects reminiscent of insc mutants. Pins colocalizes with Insc and interacts with the region necessary and sufficient for directing its asymmetric localization. Analyses of pins function in neuroblasts reveal two distinct steps for Insc apical cortical localization: A pins-independent, bazooka-dependent initiation step during delamination (interphase) and a later maintenance step during which Baz, Pins, and Insc localization are interdependent. 相似文献
54.
Chuan‐Mei Yeh Jyh‐Perng Wang Shih‐Ching Lo Wen‐Chia Chan Ming‐Yi Lin 《Biotechnology progress》2010,26(4):1001-1007
Poly‐γ‐glutamate (γ‐PGA) has applications in food, medical, cosmetic, animal feed, and wastewater industries. Bacillus subtilis DB430, which possesses the γ‐PGA synthesis ywsC‐ywtAB genes in its chromosome, cannot produce γ‐PGA. An efficient synthetic expression control sequence (SECS) was introduced into the upstream region of the ywtABC genes, and this resulted in γ‐PGA‐producing B. subtilis mutant strains. Mutant B. subtilis PGA6‐2 stably produces high levels of γ‐PGA in medium A without supplementation of extra glutamic acid or ammonium chloride. The mutant B. subtilis PGA 6‐2 is not only a γ‐PGA producer, but it is also a candidate for the genetic and metabolic engineering of γ‐PGA production. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 相似文献
55.
Ting Chia Weng Ta Chien Chan Hsien Tang Lin Chia Kun Jasper Chang Wen Wen Wang Zheng Rong Tiger Li Hao-Yuan Cheng Yu-Roo Chu Allen Wen-Hsiang Chiu Muh-Yong Yen Chwan-Chuen King 《PloS one》2015,10(4)
School children may transmit pathogens with cluster cases occurring on campuses and in families. In response to the 2009 influenza A (H1N1) pandemic, Taipei City Government officials developed a School-based Infectious Disease Syndromic Surveillance System (SID-SSS). Teachers and nurses from preschools to universities in all 12 districts within Taipei are required to daily report cases of symptomatic children or sick leave requests through the SID-SSS. The pre-diagnosis at schools is submitted firstly as common pediatric disease syndrome-groups and re-submitted after confirmation by physicians. We retrieved these data from January 2010 to August 2011 for spatio-temporal analysis and evaluated the temporal trends with cases obtained from both the Emergency Department-based Syndromic Surveillance System (ED-SSS) and the Longitudinal Health Insurance Database 2005 (LHID2005). Through the SID-SSS, enterovirus-like illness (EVI) and influenza-like illness (ILI) were the two most reported syndrome groups (77.6% and 15.8% among a total of 19,334 cases, respectively). The pre-diagnosis judgments made by school teachers and nurses showed high consistency with physicians’ clinical diagnoses for EVI (97.8%) and ILI (98.9%). Most importantly, the SID-SSS had better timeliness with earlier peaks of EVI and ILI than those in the ED-SSS. Furthermore, both of the syndrome groups in these two surveillance systems had the best correlation reaching 0.98 and 0.95, respectively (p<0.01). Spatio-temporal analysis observed the patterns of EVI and ILI both diffuse from the northern suburban districts to central Taipei, with ILI spreading faster. This novel system can identify early suspected cases of two important pediatric infections occurring at schools, and clusters from schools/families. It was also cost-effective (95.5% of the operation cost reduced and 59.7% processing time saved). The timely surveillance of mild EVI and ILI cases integrated with spatial analysis may help public health decision-makers with where to target for enhancing surveillance and prevention measures to minimize severe cases. 相似文献
56.
57.
Sitagliptin attenuates sympathetic innervation via modulating reactive oxygen species and interstitial adenosine in infarcted rat hearts 下载免费PDF全文
Tsung‐Ming Lee Wei‐Ting Chen Chen‐Chia Yang Shinn‐Zong Lin Nen‐Chung Chang 《Journal of cellular and molecular medicine》2015,19(2):418-429
We investigated whether sitagliptin, a dipeptidyl peptidase‐4 (DPP‐4) inhibitor, attenuates arrhythmias through inhibiting nerve growth factor (NGF) expression in post‐infarcted normoglycemic rats, focusing on adenosine and reactive oxygen species production. DPP‐4 bound adenosine deaminase has been shown to catalyse extracellular adenosine to inosine. DPP‐4 inhibitors increased adenosine levels by inhibiting the complex formation. Normoglycemic male Wistar rats were subjected to coronary ligation and then randomized to either saline or sitagliptin in in vivo and ex vivo studies. Post‐infarction was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle‐treated infarcted rats compared with sham. Compared with vehicle, infarcted rats treated with sitagliptin significantly increased interstitial adenosine levels and attenuated oxidative stress. Sympathetic hyperinnervation was blunted after administering sitagliptin, as assessed by immunofluorescent analysis and western blotting and real‐time quantitative RT‐PCR of NGF. Arrhythmic scores in the sitagliptin‐treated infarcted rats were significantly lower than those in vehicle. Ex vivo studies showed a similar effect of erythro‐9‐(2‐hydroxy‐3‐nonyl) adenine (an adenosine deaminase inhibitor) to sitagliptin on attenuated levels of superoxide and NGF. Furthermore, the beneficial effects of sitagliptin on superoxide anion production and NGF levels can be reversed by 8‐cyclopentyl‐1,3‐dipropulxanthine (adenosine A1 receptor antagonist) and exogenous hypoxanthine. Sitagliptin protects ventricular arrhythmias by attenuating sympathetic innervation via adenosine A1 receptor and xanthine oxidase‐dependent pathways, which converge through the attenuated formation of superoxide in the non‐diabetic infarcted rats. 相似文献
58.
59.
Thomas J. Hannan Indira U. Mysorekar Chia S. Hung Megan L. Isaacson-Schmid Scott J. Hultgren 《PLoS pathogens》2010,6(8)
Chronic infections are an increasing problem due to the aging population and the increase in antibiotic resistant organisms. Therefore, understanding the host-pathogen interactions that result in chronic infection is of great importance. Here, we investigate the molecular basis of chronic bacterial cystitis. We establish that introduction of uropathogenic E. coli (UPEC) into the bladders of C3H mice results in two distinct disease outcomes: resolution of acute infection or development of chronic cystitis lasting months. The incidence of chronic cystitis is both host strain and infectious dose-dependent. Further, development of chronic cystitis is preceded by biomarkers of local and systemic acute inflammation at 24 hours post-infection, including severe pyuria and bladder inflammation with mucosal injury, and a distinct serum cytokine signature consisting of elevated IL-5, IL-6, G-CSF, and the IL-8 analog KC. Mice deficient in TLR4 signaling or lymphocytes lack these innate responses and are resistant, to varying degrees, to developing chronic cystitis. Treatment of C3H mice with the glucocorticoid anti-inflammatory drug dexamethasone prior to UPEC infection also suppresses the development of chronic cystitis. Finally, individuals with a history of chronic cystitis, lasting at least 14 days, are significantly more susceptible to redeveloping severe, chronic cystitis upon bacterial challenge. Thus, we have discovered that the development of chronic cystitis in C3H mice by UPEC is facilitated by severe acute inflammatory responses early in infection, which subsequently are predisposing to recurrent cystitis, an insidious problem in women. Overall, these results have significant implications for our understanding of how early host-pathogen interactions at the mucosal surface determines the fate of disease. 相似文献
60.