全文获取类型
收费全文 | 20944篇 |
免费 | 1537篇 |
国内免费 | 11篇 |
出版年
2023年 | 54篇 |
2022年 | 50篇 |
2021年 | 329篇 |
2020年 | 247篇 |
2019年 | 310篇 |
2018年 | 531篇 |
2017年 | 393篇 |
2016年 | 680篇 |
2015年 | 1126篇 |
2014年 | 1223篇 |
2013年 | 1393篇 |
2012年 | 1825篇 |
2011年 | 1706篇 |
2010年 | 1098篇 |
2009年 | 912篇 |
2008年 | 1344篇 |
2007年 | 1184篇 |
2006年 | 1052篇 |
2005年 | 971篇 |
2004年 | 958篇 |
2003年 | 777篇 |
2002年 | 783篇 |
2001年 | 625篇 |
2000年 | 629篇 |
1999年 | 418篇 |
1998年 | 155篇 |
1997年 | 121篇 |
1996年 | 113篇 |
1995年 | 87篇 |
1994年 | 82篇 |
1993年 | 69篇 |
1992年 | 157篇 |
1991年 | 125篇 |
1990年 | 88篇 |
1989年 | 103篇 |
1988年 | 70篇 |
1987年 | 65篇 |
1986年 | 69篇 |
1985年 | 53篇 |
1984年 | 47篇 |
1983年 | 37篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1978年 | 28篇 |
1977年 | 23篇 |
1976年 | 32篇 |
1975年 | 29篇 |
1973年 | 33篇 |
1971年 | 23篇 |
1969年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Hong Jun Jeon Young Rong Bang Hye Youn Park Seul A. Kim 《Chronobiology international》2017,34(6):677-686
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
102.
Barakaeli Abdieli Ndosi Hansol Park Dongmin Lee Seongjun Choe Yeseul Kang Tilak Chandra Nath Mohammed Mebarek Bia Chatanun Eamudomkarn Hyeong-Kyu Jeon Keeseon S. Eom 《The Korean journal of parasitology》2020,58(6):653
Spirometra tapeworms (Cestoda: Diphyllobothriidae) collected from carnivorous mammals in Tanzania were identified by the DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and internal transcribed spacer 1 (ITS1), and by morphological characteristics. A total of 15 adult worms were collected from stool samples and carcasses of Panthera leo, Panthera pardus, and Crocuta crocuta in the Serengeti and Selous ecosystems of Tanzania. Three Spirometra species: S. theileri, S. ranarum and S. erinaceieuropaei were identified based on morphological features. Partial cox1 sequences (400 bp) of 10 specimens were revealed. Eight specimens showed 99.5% similarity with Spirometra theileri (), 1 specimen showed 99.5% similarity with the Korean S. erinaceieuropaei and 1 specimen had 99.5% similarity with Myanmar S. ranarum. Sequence homology estimates for the ITS1 region of S. theileri were 89.8% with S. erinaceieuropaei, 82.5% with S. decipiens, and 78.3% with S. ranarum; and 94.4% homology was observed between S. decipiens and S. ranarum. Phylogenetic analyses were performed with 4 species of Spirometra and 2 species of Dibothriocephalus (=Diphyllobothrium). By both ML and BI methods, cox1 and ITS1 gave well supported, congruent trees topology of S. erinaceieuropaei and S. theileri with S. decipiens and S. ranarum forming a clade. The Dibothriocephalus species were sisters of each other and collectively forming successive outgroups. Our findings confirmed that 3 Spirometra species (S. theileri, S. ranarum, and S. erinaceieuropaei) are distributed in the Serengeti and Selous ecosystems of Tanzania. MK955901相似文献
103.
Whole body energy balance is achieved through the coordinated regulation of energy intake and energy expenditure in various tissues including liver, muscle and adipose tissues. A positive energy imbalance by excessive energy intake or insufficient energy expenditure results in obesity and related metabolic diseases. Although there have been many obesity treatment trials aimed at the reduction of energy intake, these strategies have achieved only limited success because of their associated adverse effects. An ancient neurotransmitter, serotonin is among those traditional pharmacological targets for anti-obesity treatment because it exhibits strong anorectic effect in the brain. However, recent studies suggest the new functions of peripheral serotonin in energy homeostasis ranging from the endocrine regulation by gut-derived serotonin to the autocrine/paracrine regulation by adipocyte-derived serotonin. Here, we discuss the role of serotonin in the regulation of energy homeostasis and introduce peripheral serotonin as a possible target for anti-obesity treatment. 相似文献
104.
Min Soo Byun Song E. Kim Jinsick Park Dahyun Yi Young Min Choe Bo Kyung Sohn Hyo Jung Choi Hyewon Baek Ji Young Han Jong Inn Woo Dong Young Lee Alzheimer’s Disease Neuroimaging Initiative 《PloS one》2015,10(11)
We aimed to identify and characterize subtypes of Alzheimer’s disease (AD) exhibiting different patterns of regional brain atrophy on MRI using age- and gender-specific norms of regional brain volumes. AD subjects included in the Alzheimer''s Disease Neuroimaging Initiative study were classified into subtypes based on standardized values (Z-scores) of hippocampal and regional cortical volumes on MRI with reference to age- and gender-specific norms obtained from 222 cognitively normal (CN) subjects. Baseline and longitudinal changes of clinical characteristics over 2 years were compared across subtypes. Whole-brain-level gray matter (GM) atrophy pattern using voxel-based morphometry (VBM) and cerebrospinal fluid (CSF) biomarkers of the subtypes were also investigated. Of 163 AD subjects, 58.9% were classified as the “both impaired” subtype with the typical hippocampal and cortical atrophy pattern, whereas 41.1% were classified as the subtypes with atypical atrophy patterns: “hippocampal atrophy only” (19.0%), “cortical atrophy only” (11.7%), and “both spared” (10.4%). Voxel-based morphometric analysis demonstrated whole-brain-level differences in overall GM atrophy across the subtypes. These subtypes showed different progression rates over 2 years; and all subtypes had significantly lower CSF amyloid-β1–42 levels compared to CN. In conclusion, we identified four AD subtypes exhibiting heterogeneous atrophy patterns on MRI with different progression rates after controlling the effects of aging and gender on atrophy with normative information. CSF biomarker analysis suggests the presence of Aβ neuropathology irrespective of subtypes. Such heterogeneity of MRI-based neuronal injury biomarker and related heterogeneous progression patterns should be considered in clinical trials and practice with AD patients. 相似文献
105.
Sang-Young Park Myung-Geun Shin Hye-Ran Kim Ji-Yeon Oh Soo-Hyun Kim Jong-Hee Shin Yong-Bum Cho Soon-Pal Suh Dong-Wook Ryang 《Mitochondrion》2009,9(5):318-325
This study was designed to investigate the possibility that mtDNA mutations might arise in inflammatory or chronically damaged nasal polyp tissue from 23 patients. Thirteen patients (57%) displayed nasal polyp tissue-specific mtDNA mutations in the hypervariable segment of the control region and cytochrome b gene, which were not found in the corresponding blood cells and/or adjacent normal tissue. Nasal polyp tissue-specific length heteroplasmic mutations were also detected in nucleotide position (np) 303–315 homopolymeric poly C track (39%), np 514–523 CA repeats (17%) and np 16184–16193 poly C track (30%). The average mtDNA copy number was about three times higher in nasal polyp tissue than in the corresponding peripheral blood cells and adjacent non-polyp tissues. The level of reactive oxygen species (ROS) was significantly higher in the nasal polyp tissues compared to those from the corresponding samples. High level of ROS in nasal polyp tissue may contribute to development of mtDNA mutations, which may play a crucial role in the vicious cycle of pathophysiology of nasal polyps. 相似文献
106.
107.
108.
109.
Qm mutant phage 5 is deficient in the synthesis of the proteins involved in cell lysis and 5 DNA packaging. As a result, the replicated Qm 5 DNA containing a cloned gene is not easily coated by a phage head and remains naked for the ample expression of the cloned gene, and also the host cells do not lyse easily and larger amounts of cloned gene products are produced. In a two-phase operation, the first phase is operated at a low temperature to keep the phage in the lysogenic state for cell growth and cloned gene stability, while the second phase is operated at a high temperature to induce the lytic state for the amplification of the cloned gene and overproduction of its product. This two-phase operation was optimized by determining both the optimal temperatures for the growth and production phases and the optimal switching time between the growth to the production phase. The optimal temperatures for growth and production phases were 33 and 40 °C, respectively. The optimal switching time was 3 h. The recombinant #-galactosidase production using this optimal process was about 20 times higher than in the single-copy lysogenic state. 相似文献
110.
Murine Cytomegalovirus m02 Gene Family Protects against Natural Killer Cell-Mediated Immune Surveillance 下载免费PDF全文
Sofia A. Oliveira Se-Ho Park Peter Lee Albert Bendelac Thomas E. Shenk 《Journal of virology》2002,76(2):885-894
The murine cytomegalovirus m02 gene family encodes putative type I membrane glycoproteins named m02 through m16. A subset of these genes were fused to an epitope tag and cloned into an expression vector. In transfected and murine cytomegalovirus-infected cells, m02, m04, m05, m06, m07, m09, m10, and m12 localized to cytoplasmic structures near the nucleus, whereas m08 and m13 localized to a filamentous structure surrounding the nucleus. Substitution mutants lacking the m02 gene (SMsubm02) or the entire m02 gene family (SMsubm02-16) grew like their wild-type parent in cultured cells. However, whereas SMsubm02 was as pathogenic as the wild-type virus, SMsubm02-16 was markedly less virulent. SMsubm02-16 produced less infectious virus in most organs compared to wild-type virus in BALB/c and C57BL/6J mice, but it replicated to wild-type levels in the organs of immunodeficient gamma(c)/Rag2 mice, lacking multiple cell types including natural killer cells, and in C57BL/6J mice depleted of natural killer cells. These results argue that one or more members of the m02 gene family antagonize natural killer cell-mediated immune surveillance. 相似文献