首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1054篇
  免费   77篇
  国内免费   23篇
  1154篇
  2023年   7篇
  2022年   18篇
  2021年   22篇
  2020年   11篇
  2019年   23篇
  2018年   31篇
  2017年   29篇
  2016年   31篇
  2015年   61篇
  2014年   66篇
  2013年   80篇
  2012年   115篇
  2011年   88篇
  2010年   53篇
  2009年   35篇
  2008年   56篇
  2007年   53篇
  2006年   53篇
  2005年   40篇
  2004年   28篇
  2003年   41篇
  2002年   37篇
  2001年   19篇
  2000年   26篇
  1999年   10篇
  1998年   6篇
  1997年   7篇
  1996年   7篇
  1994年   3篇
  1992年   8篇
  1991年   11篇
  1990年   7篇
  1989年   3篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1981年   3篇
  1980年   3篇
  1978年   7篇
  1976年   2篇
  1974年   2篇
  1973年   4篇
  1972年   2篇
  1971年   5篇
  1967年   2篇
  1966年   3篇
  1965年   3篇
  1961年   2篇
  1909年   2篇
  1907年   2篇
排序方式: 共有1154条查询结果,搜索用时 0 毫秒
1.
2.
This study was conducted to monitor the abundance and distribution of the ussur brown katydid, Paratlanticus ussuriensis in South Korea, and to gather basic information about potential outbreak areas of this species. P. ussuriensis samples were collected from April to July in 2009 and 2010 using the transect method at the city or gun level. P. ussuriensis were identified in 86 cities or guns, and eight guns were determined to be potential risk areas of P. ussuriensis outbreaks. The current distribution of P. ussuriensis is well matched with the distribution of broadleaf trees. Their distribution and population density are expected to increase due to the expanding distribution of Quercus spp., the major food source of P. ussuriensis.  相似文献   
3.
Chromosomal translocations are rare in myelodysplastic syndrome (MDS) and their impact on overall survival (OS) and response to hypomethylating agents (HMA) is unknown. The prognostic impact of the revised International Prognostic Scoring System (IPSS-R) and for chromosomal translocations was assessed in 751 patients from the Korea MDS Registry. IPSS-R effectively discriminated patients according to leukaemia evolution risk and OS. We identified 40 patients (5.3%) carrying translocations, 30 (75%) of whom also fulfilled complex karyotype criteria. Translocation presence was associated with a shorter OS (median, 12.0 versus 79.7 months, P < 0.01). Multivariate analysis demonstrated that translocations (hazard ratio [HR] 1.64 [1.06–2.63]; P = 0.03) as well as age, sex, IPSS-R, and CK were independent predictors of OS. In the IPSS-R high and very high risk subgroup (n = 260), translocations remained independently associated with OS (HR 1.68 [1.06–2.69], P = 0.03) whereas HMA treatment was not associated with improved survival (median OS, 20.9 versus 21.2 months, P = 0.43). However, translocation carriers exhibited enhanced survival following HMA treatment (median 2.1 versus 12.4 months, P = 0.03). Our data suggest that chromosomal translocation is an independent predictor of adverse outcome and has an additional prognostic value in discriminating patients with MDS having higher risk IPSS-R who could benefit from HMA treatment.  相似文献   
4.
Various physiological and psychological functions are influenced by circadian typology (CT), which was reported to be related to resilience. However, few studies have assessed the effects of CT in relation to resilience. The aim of the present study was to assess the influence of CT on sleep-related symptoms, physical fatigue and psychological well-being in relation to resilience. The present study included a total of 1794 healthy hospital employees, and they completed the Morningness–Eveningness Questionnaire, Connor–Davidson Resilience Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Fatigue Severity Scale, Hospital Anxiety and Depression Scale and World Health Organization Quality of Life Scale Abbreviated Version. Subjects with evening type showed lower sleep quality, more daytime sleepiness and physical fatigue than neither types and morning types. Additionally, evening types were more depressed and anxious and reported a poorer quality of life. CT was found to be a significant predictor of sleep quality, but CT was minimally associated with physical fatigue and psychological well-being in the regression analysis. Instead, resilience was substantially related to all of the variables measured. In conclusion, CT independently predicts sleep quality, but the effects of CT on physical fatigue and psychological well-being are negligible compared to those of resilience.  相似文献   
5.
A bacterium, designated M2-6, was isolated from Korean ginseng, Panax ginseng C. A. Meyer, roots after high-hydrostatic-pressure processing. On the basis of 16 rRNA gene phylogeny, the isolate was presumptively identified as a Bacillus sp. Here we report the draft genome sequence of Bacillus sp. strain M2-6 (= KACC 16563).  相似文献   
6.
Lipopolysaccharide is strongly associated with septic shock, leading to multiple organ failure. It can activate monocytes and macrophages to release proinflammatory mediators such as tumor necrosis factor- (TNF-), interleukin-1 (IL-1), and nitric oxide (NO). The present experiments were designed to induce endotoxin shock by an intravenous injection ofKlebsiella pneumoniae lipopolysaccharide (LPS, 10 mg/kg) in conscious rats. Arterial pressure and heart rate (HR) were continuously monitored for 48 h after LPS administration. N-Acetyl-cysteine was used to study its effects on organ damage. Biochemical substances were measured to reflect organ functions. Biochemical factors included blood urea nitrogen (BUN), creatinine (Cre), lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aspartate transferase (GOT), alanine transferase (GPT), TNF-, IL-1, methyl guanidine (MG), and nitrites/nitrates. LPS caused significant increases in blood BUN, Cre, LDH, CPK, GOT, GPT, TNF-, IL-1, MG levels, and HR, as well as a decrease in mean arterial pressure and an elevation of nitrites/nitrates. N-Acetylcysteine suppressed the release of TNF-, IL-1, and MG, but enhanced NO production. These actions ameliorate LPS-induced organ damage in conscious rats. The beneficial effects may suggest a potential chemopreventive effect of this compound in sepsis prevention and treatment.  相似文献   
7.
Genomic research in any organism encompasses understanding structure of the target genome and genes, their function, and evolution. Brassica rapa , which is phylogenetically related to Arabidopsis thaliana , is an important species with respect to its uses as vegetable, oil, and fodder. The availability of suitable genetic and genomic resources is a prerequisite to undertake genomic research in B. rapa . We have developed reference mapping populations of Chinese cabbage ( B. rapa ssp. pekinensis ) comprising 78 doubled haploid lines and over 250 recombinant inbred lines. Two Bacterial Artificial Chromosome (BAC) libraries, generated by restriction enzymes Hin dIII (KBrH) and Bam HI (KBrB), comprise 56 592 and 50 688 clones, respectively. We have also constructed 22 cDNA libraries from different plant tissues consisting of 104 914 clones with an average length of 575 bp. Initial BAC-end sequence analysis of 1473 clones of the KBrH library led us to understand the structure of B. rapa genome with respect to extent of genic sequences and their annotation, and relative abundance of different types of repetitive DNAs. Full-length sequence analysis of BAC clones revealed extensive triplication of B. rapa DNA segments coupled with variable gene losses within the segments. The formulation of the 'Multinational Brassica Genome Project' has laid the foundation to sequence the complete genome of B. rapa ssp. pekinensis by the international Brassica research community. It has been proposed to undertake BAC-to-BAC sequencing of genetically mapped seed BACs. In recent years, development of bioinformatics tools in Brassica has given a boost to structural genomics research in Brassica species. The research undertaken with the availability of various genomic resources in the public domain has added to our understanding of the structure of B. rapa .  相似文献   
8.
BACKGROUND/AIMS: TFF3, a member of the TFF (trefoil factor family) peptides, and epidermal growth factor (EGF) actively support the repair of mucosal barriers, particularly during restitution. The aim of this study was to compare the motogenic effects of TFF3 and EGF. METHODS: The influence of recombinant human TFF3 (dimeric form) and EGF on the migration of IEC-18 cells was characterized in an in vitro restitution model (scratch wound assay) with the help of time-lapse video microscopy, morphometry, and immunocytochemistry including confocal laser scanning microscopy. RESULTS: TFF3- and EGF-treated cells re-populated the wounded area via different migration patterns; TFF3 treatment resulted in the formation of continuous sheets of migrating cells with only a few gaps. In contrast, EGF-treated cells formed a network of migrating cells (often with a fibroblast-like morphology) with numerous gaps and only punctual contacts. TFF3 and EGF treatment also changed the localization of E-cadherin indicating endocytotic recycling and/or degradation of E-cadherin. CONCLUSION: TFF3, in contrast to EGF, enhanced a collective cell migration ensuring a precise coverage of the re-populated area avoiding gaps.  相似文献   
9.
Hemocytes of the last larva of the Japanese rhinoceros beetle A. dichotoma (Linnaeus) (Coleoptera: Scarabaeidae) were classified as granulocytes, plasmatocytes, oenocytoids, spherulocytes, prohemocytes, and adipohemocytes. Among these cell types, only the granulocytes became immunologically activated with obvious morphological changes, displaying large amoeba-like, lobopodia-like, and fan-like structures. In addition, their cytoplasmic granules became larger and greatly increased in number. To explore whether these granules could be immunologically generated as phagosomes, total hemocytes were stained with LysoTracker. Greater than 90% of the granulocytes retained the LysoTracker dye at 4 h post-bacterial infection. In flow cytometry analysis, the red fluorescent signal was highly increased at 4 h post-bacterial infection (60.36%) compared to controls (5.08%), as was confirmed by fluorescent microscopy. After 12 h post-infection, these signals returned to basal levels. The uptake of pathogens by granulocytes rapidly triggered the translocation of the microtubule-associated protein 1 light chain 3 alpha (LC3) to the phagosome, which may result in enhanced pathogen killing.  相似文献   
10.
实验探讨了建鲤和异育银鲫摄食低质和高质饲料时氮和能量的收支情况.低质饲料以豆粕为主要蛋白源,饲料蛋白含量为33.91%,高质饲料以鱼粉为主要蛋白源,饲料蛋白含量为45.59%.55d的生长结果显示,氮收支和能量收支受到饲料质量和鱼类种类的显著影响:摄食低质饲料时,建鲤的生长氮和生长能比例显著低于异育银鲫,排泄氮、排泄能和代谢能比例显著高于异育银鲫;摄食高质饲料时,两种鱼的氮收支和能量收支无显著差异;建鲤的氮收支和能量收支受饲料质量的显著影响,摄食低质饲料时,其生长氮和生长能比例均显著低于摄食高质饲料时,而排泄氮、粪能和代谢能比例均显著高于摄食高质饲料时;异育银鲫的氮收支、生长能和代谢能比例不受饲料质量的显著影响.结果表明,在低质饲料条件下,建鲤利用氮和能量的能力弱于异育银鲫,在高质饲料条件下,两种鱼没有显著差异.与异育银鲫相比,建鲤利用氮和能量的能力受饲料质量的影响更为显著.    相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号