全文获取类型
收费全文 | 90309篇 |
免费 | 5401篇 |
国内免费 | 1564篇 |
专业分类
97274篇 |
出版年
2024年 | 707篇 |
2023年 | 778篇 |
2022年 | 1828篇 |
2021年 | 2881篇 |
2020年 | 2062篇 |
2019年 | 2481篇 |
2018年 | 2633篇 |
2017年 | 2086篇 |
2016年 | 3130篇 |
2015年 | 4870篇 |
2014年 | 5640篇 |
2013年 | 5984篇 |
2012年 | 7534篇 |
2011年 | 7000篇 |
2010年 | 4412篇 |
2009年 | 3931篇 |
2008年 | 5125篇 |
2007年 | 4831篇 |
2006年 | 4159篇 |
2005年 | 3753篇 |
2004年 | 3291篇 |
2003年 | 2899篇 |
2002年 | 2485篇 |
2001年 | 1981篇 |
2000年 | 1776篇 |
1999年 | 1564篇 |
1998年 | 754篇 |
1997年 | 677篇 |
1996年 | 546篇 |
1995年 | 470篇 |
1994年 | 467篇 |
1993年 | 349篇 |
1992年 | 576篇 |
1991年 | 504篇 |
1990年 | 423篇 |
1989年 | 349篇 |
1988年 | 264篇 |
1987年 | 281篇 |
1986年 | 228篇 |
1985年 | 183篇 |
1984年 | 137篇 |
1983年 | 125篇 |
1982年 | 103篇 |
1981年 | 81篇 |
1980年 | 77篇 |
1979年 | 98篇 |
1978年 | 70篇 |
1977年 | 68篇 |
1975年 | 68篇 |
1974年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Ho Jun Kim Seulggie Choi Kyuwoong Kim Hyungjun Park Kyae-Hyung Kim 《Chronobiology international》2020,37(2):272-280
ABSTRACTBackground: The disruption of circadian rhythm has been found to associate with obesity in vivo and in vitro. Sleep duration, eating habits, total feeding time, and nightshift work can also affect circadian rhythms. This study investigated the association between misalignment of circadian rhythm and obesity in Korean men, using a cross-sectional database.Methods: This study used data from the Korean National Health and Nutrition Examination Survey (KNHANES), whose study population was 3,658 men aged 18 to 60 years. General and abdominal obesity was defined as a body mass index (BMI) ≥ 25 kg/m2 and waist circumference ≥ 90 cm, respectively. Circadian rhythm factors were determined with a self-report questionnaire and included breakfast frequency, sleep duration, and work time. Frequency of breakfast was divided into regular breakfast (five to seven times a week) and irregular breakfast (less than five times a week). Sleep duration was divided into less than 7 hours, 7–9 hours, and over 9 hours. Working time was defined as day/evening, night shift, and other type. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for general and abdominal obesity were calculated using multivariable logistic regression according to the number of factors that disturb the circadian rhythm.Results: Participants with 1 (aOR 1.34, 95% Cl 1.10–1.61) and ≥2 (aOR 1.62, 95% Cl 1.29–2.05) factors disturbing circadian rhythms were associated with elevated risk for general obesity. Similarly, those with 1 (aOR 1.33, 95% Cl 1.09–1.63) and ≥2 (aOR 1.70, 95% Cl 1.32–2.20) factors had elevated risk for abdominal obesity.Conclusions: Factors disturbing the circadian rhythm were associated with general and abdominal obesity. Additional studies are needed, and associations with metabolic diseases should be investigated. 相似文献
2.
3.
本文用ABC—GDN免疫组织化学方法,研究了γ-氨基丁酸(Gamma—Aminobutyric Acid,GABA)在大鼠胰腺的定位和分布,并用相邻切片法,观察它与胰岛素的共存关系。结果发现GABA免疫反应阳性细胞主要分布于胰腺内分泌部(胰岛)。在外分泌部亦有少许分布。大部分胰岛细胞呈GABA免疫反应阳性,集中位于胰岛的中央部。相邻连续切片免疫染色证实GABA与胰岛素共存于胰岛B细胞中。外分泌部胰腺GABA免疫反应阳性细胞,呈零散分布于腺泡和导管上皮间。本文为进一步探讨GABA在胰腺的生理作用提供了形态学依据。 相似文献
4.
5.
The effects on the fecundity and fertility of redbanded leafroller, Argyrotaenia velutinana (Walker), and obliquebanded leafroller,Choristoneura rosaceana (Harris), exposed as adults to surfaces treated with the ecdysone agonists tebufenozide (RH-5992) and methoxyfenozide (RH-2485) were examined. The first part of the study consisted of recently emerged moths being exposed to treated surfaces continuously throughout their lives (including mating and oviposition). Continuous exposure to tebufenozide- or methoxyfenozide-treated surfaces significantly reduced the mean number of eggs laid and the percent of eggs that hatched in both species. The second part of the study involved exposure of recently emerged virgin moths (by sex) to treated surfaces for 24 h, after which, the exposed moths were paired with a nontreated partner to mate and oviposit on nontreated surfaces. In this experiment, for A. velutinana, significant reductions in fecundity occurred only when the female was exposed to methoxyfenozide-treated surfaces. Significant reductions in A. velutinana egg fertility occurred with both male and female exposure in the methoxyfenozide treatments and only female exposure in the tebufenozide treatments. For C. rosaceana, significant reductions in fecundity occurred with both male and female exposure in the tebufenozide and methoxyfenozide treatments. Significant reductions in C. rosaceana egg fertility occurred with both male and female exposure in the tebufenozide treatments and only with female exposure in the methoxyfenozide treatments. 相似文献
6.
Detection of gene mutations related with drug resistance in Mycobacterium leprae from leprosy patients using Touch-Down (TD) PCR 总被引:3,自引:0,他引:3
The lack of methods to identify Mycobacterium leprae with the resistance against multi-drugs quickly and specifically has hindered effective chemotherapy against M. leprae infection. To screen M. leprae with resistance against multi-drugs, the Touch-Down (TD)-PCR has been used in this study. Sequences of the folP, rpoA, B, and gyrA, B genes were analyzed for isolates of M. leprae from leprosy patients in Korea. We amplified designated region of several genes in M. leprae involved in drug resistance and could obtain the PCR products of each gene. The mutations in the particular region of folP, rpoB, and gyrB gene were certified by TD-PCR single-stranded conformational polymorphism and DNA sequencing, respectively. 相似文献
7.
8.
DNA-methyltransferase-3B (DNMT3b) plays an important role in the generation of aberrant methylation in carcinogenesis. DNMT3b SNP has been associated with susceptibility to lung, head, neck, and breast cancer, but its association with the development
of colon cancer has not been reported. We investigated the relationship between the 39179GT polymorphism in the DNMT3b gene, which is involved in de novo methylation and is associated with the risk of adenocarcinoma of the colon in Koreans.
The DNMT3b 39179GT genotypes were determined by a PCR-RFLP method in 248 adenocarcinomas of colon cancer patients and in 248 healthy
controls matched as to age and sex. When stratified by sex and age, a significantly reduced risk of the combined GT and GG
genotypes was observed in younger patients (<59, adjusted OR = 0.255, 95% CI = 0.133–0.489) and in male patients (adjusted
OR = 0.383, 95% CI = 0.225–0.652). The DNMT3b 39179GT polymorphism may be a genetic determinant of adenocarcinoma of the colon, especially in younger Korean men. 相似文献
9.
Aims: To investigate the species-specific prevalence of vhhP2 among Vibrio harveyi isolates and the applicability of vhhP2 in the specific detection of V. harveyi from crude samples of animal and environmental origins.
Methods and Results: A gene ( vhhP2 ) encoding an outer membrane protein of unknown function was identified from a pathogenic V. harveyi isolate. vhhP2 is present in 24 V. harveyi strains isolated from different geographical locations but is absent in 24 strains representing 17 different non- V. harveyi species, including V. parahaemolyticus and V. alginolyticus . A simple polymerase chain reaction method for the identification of V. harveyi was developed based on the conserved sequence of vhhP2 . This method was demonstrated to be applicable to the quick detection of V. harveyi from crude animal specimens and environmental samples. The specificity of this method was tested by applying it to the examination of two strains of V. campbellii , which is most closely related to V. harveyi . One of the V. campbellii strains was falsely identified as V. harveyi .
Conclusions: vhhP2 is ubiquitously present in the V. harveyi species and is absent in most of the non- V. harveyi species; this feature enables vhhP2 to serve as a genetic marker for the rapid identification of V. harveyi . However, this method can not distinguish some V. campbellii strains from V. harveyi .
Significance and Impact of the Study: the significance of our study is the identification of a novel gene of V. harveyi and the development of a simple method for the relatively accurate detection of V. harveyi from animal specimens and environmental samples. 相似文献
Methods and Results: A gene ( vhhP2 ) encoding an outer membrane protein of unknown function was identified from a pathogenic V. harveyi isolate. vhhP2 is present in 24 V. harveyi strains isolated from different geographical locations but is absent in 24 strains representing 17 different non- V. harveyi species, including V. parahaemolyticus and V. alginolyticus . A simple polymerase chain reaction method for the identification of V. harveyi was developed based on the conserved sequence of vhhP2 . This method was demonstrated to be applicable to the quick detection of V. harveyi from crude animal specimens and environmental samples. The specificity of this method was tested by applying it to the examination of two strains of V. campbellii , which is most closely related to V. harveyi . One of the V. campbellii strains was falsely identified as V. harveyi .
Conclusions: vhhP2 is ubiquitously present in the V. harveyi species and is absent in most of the non- V. harveyi species; this feature enables vhhP2 to serve as a genetic marker for the rapid identification of V. harveyi . However, this method can not distinguish some V. campbellii strains from V. harveyi .
Significance and Impact of the Study: the significance of our study is the identification of a novel gene of V. harveyi and the development of a simple method for the relatively accurate detection of V. harveyi from animal specimens and environmental samples. 相似文献
10.
Ahmed H.E. Hassan Min Chang Cho Hye In Kim Ji Seul Yang Kyung Tae Park Ji Young Hwang Choon-Gon Jang Ki Duk Park Yong Sup Lee 《Bioorganic & medicinal chemistry》2018,26(18):5069-5078
CRA13; a peripheral dual CB1R/CB2R agonist with clinically proven analgesic properties, infiltrates into CNS producing adverse effects due to central CB1R agonism. Such adverse effects might be circumvented by less lipophilic compounds with attenuated CB1R affinity. Metabolism produces less lipophilic metabolites that might be active metabolites. Some CRA13 oxidative metabolites and their analogues were synthesized as less lipophilic CRA13 analogues. Probing their CB1R and CB2R activity revealed the alcohol metabolite 8c as a more potent and more effective CB2R ligand with attenuated CB1R affinity relative to CRA13. Also, the alcohol analogue 8b and methyl ester 12a possessed enhanced CB2R affinity and reduced CB1R affinity. The CB2R binding affinity of alcohol analogue 8b was similar to CRA13 while that of methyl ester 12a was more potent. In silico study provided insights into the possible molecular interactions that might explain the difference in the elicited biological activity of these compounds. 相似文献