全文获取类型
收费全文 | 3726篇 |
免费 | 313篇 |
国内免费 | 1篇 |
专业分类
4040篇 |
出版年
2022年 | 18篇 |
2021年 | 37篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 43篇 |
2017年 | 30篇 |
2016年 | 44篇 |
2015年 | 78篇 |
2014年 | 80篇 |
2013年 | 201篇 |
2012年 | 153篇 |
2011年 | 179篇 |
2010年 | 123篇 |
2009年 | 130篇 |
2008年 | 213篇 |
2007年 | 200篇 |
2006年 | 203篇 |
2005年 | 198篇 |
2004年 | 214篇 |
2003年 | 214篇 |
2002年 | 174篇 |
2001年 | 92篇 |
2000年 | 139篇 |
1999年 | 104篇 |
1998年 | 57篇 |
1997年 | 49篇 |
1996年 | 36篇 |
1995年 | 41篇 |
1994年 | 50篇 |
1993年 | 53篇 |
1992年 | 99篇 |
1991年 | 82篇 |
1990年 | 80篇 |
1989年 | 70篇 |
1988年 | 74篇 |
1987年 | 43篇 |
1986年 | 47篇 |
1985年 | 60篇 |
1984年 | 41篇 |
1983年 | 39篇 |
1982年 | 15篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1973年 | 10篇 |
1971年 | 10篇 |
排序方式: 共有4040条查询结果,搜索用时 15 毫秒
21.
Miyajima A Seki M Onoda F Shiratori M Odagiri N Ohta K Kikuchi Y Ohno Y Enomoto T 《Molecular and cellular biology》2000,20(17):6399-6409
The SGS1 gene of Saccharomyces cerevisiae is a homologue for the Bloom's syndrome and Werner's syndrome genes. The disruption of the SGS1 gene resulted in very poor sporulation, and the majority of the cells were arrested at the mononucleated stage. The recombination frequency measured by a return-to-growth assay was reduced considerably in sgs1 disruptants. However, double-strand break formation, which is a key event in the initiation of meiotic DNA recombination, occurred; crossover and noncrossover products were observed in the disruptants, although the amounts of these products were slightly decreased compared with those in wild-type cells. The spores produced by sgs1 disruptants showed relatively high viability. The sgs1 spo13 double disruptants sporulated poorly, like the sgs1 disruptants, but spore viability was reduced much more than with either sgs1 or spo13 single disruptants. Disruption of the RED1 or RAD17 gene partially alleviated the poor-sporulation phenotype of sgs1 disruptants, indicating that portions of the population of sgs1 disruptants are blocked by the meiotic checkpoint. The poor sporulation of sgs1 disruptants was complemented with a mutated SGS1 gene encoding a protein lacking DNA helicase activity; however, the mutated gene could suppress neither the sensitivity of sgs1 disruptants to methyl methanesulfonate and hydroxyurea nor the mitotic hyperrecombination phenotype of sgs1 disruptants. 相似文献
22.
Xiao-Jing Wang Ying-Feng Liu Qing-Yu Wang Morito Tsuruoka Kazumasa Ohta Sheng-Xi Wu Masashi Yakushiji Takashi Inoue 《Cell and tissue research》2010,340(2):347-355
Tobacco smoking is the main risk factor associated with chronic periodontitis, but the mechanisms that underlie this relationship
are largely unknown. Recent reports proposed that nicotine plays an important role in tobacco-related morbidity by acting
through the nicotinic acetylcholine receptors (nAChRs) expressed by non-neuronal cells. The aim of this study was to investigate
whether α7 nAChR was expressed in periodontal tissues and whether it functions by regulating IL-1β in the process of periodontitis.
In vitro, human periodontal ligament (PDL) cells were cultured with 10−12 M of nicotine and/or 10−9 M of alpha-bungarotoxin (α-Btx), a α7 nAChR antagonist. The expression of α7 nAChR and IL-1β in PDL cells and the effects
of nicotine/α-Btx administration on their expression were explored. In vivo, an experimental periodontitis rat model was established,
and the effects of nicotine/α-Btx administration on expression of α7 nAChR and development of periodontitis were evaluated.
We found that α7 nAChR was present in human PDL cells and rat periodontal tissues. The expressions of α7 nAChR and IL-1β were
significantly increased by nicotine administration, whereas α-Btx treatment partially suppressed these effects. This study
was the first to demonstrate the functional expression of α7 nAChR in human PDL cells and rat periodontal tissues. Our results
may be pertinent to a better understanding of the relationships among smoking, nicotine, and periodontitis. 相似文献
23.
Shoei Furukawa Isao Kamo Yoshiko Furukawa Saeko Akazawa Eijiro Satoyoshi Koji Itoh Kyozo Hayashi 《Journal of neurochemistry》1983,40(3):734-744
Abstract: A sensitive two-site enzyme immunoassay system for mouse β nerve growth factor (NGF) was developed, based on the sandwiching of the antigen between anti-mouse β NGF antibody IgG coated to a polystyrene tube and anti-mouse β NGF antibody Fab'-linked β- d -galactosidase (β- d -galactoside hydrolase, EC 3.2.1.23). This method has the following advantages: (a) the procedures are simple and rapid compared to bioassay or two-site radioimmunoassay; (b) antibody Fab'-β- d -galactosidase complex is more stable than 125 I-labeled antibody; (c) purified β NGF is detectable at a concentration as low as 10 pg/ml. Our enzyme immunoassay was used to examine the levels of NGF in some tissues of mice. The submaxillary gland contained a high concentration of NGF. However, other tissues, such as the heart, brain, and skeletal muscle, and serum did not contain detectable NGF. These results support recent findings by other investigators that NGF was not found in the organs/tissues other than the submaxillary gland of mice. 相似文献
24.
Cameron SJ Itoh S Baines CP Zhang C Ohta S Che W Glassman M Lee JD Yan C Yang J Abe J 《FEBS letters》2004,566(1-3):255-260
Big MAP kinase 1 (BMK1/ERK5) plays a critical role in pre-natal development of the cardiovascular system and post-natal eccentric hypertrophy of the heart. Of the two isoforms upstream of MAPK-kinase 5 (MEK5) known to exist, only the longer MEK5alpha isoform potently activates BMK1. We generated cardiac-specific constitutively active form of the MEK5alpha (CA-MEK5alpha transgenic (Tg) mice), and observed a 3 to 4-fold increase in endogenous BMK1 activation and hyperphosphorylation of connexin 43 in the ventricles of the Tg compared to wild-type mice. The CA-MEK5alpha-Tg-mice demonstrated a profoundly accelerated recovery of left ventricular developed pressure after ischemia/reperfusion. We propose a novel role for BMK1 in protecting the heart from ischemia/reperfusion-induced cardiac injury. 相似文献
25.
Background
In the early stages of Pandemic (H1N1) 2009, border control measures were taken by quarantine stations to block the entry of infected individuals into Japan and community containment measures were implemented to prevent the spreading. The objectives of this study were to describe these measures and the characteristics of infected individuals, and to assess the measures'' effectiveness.Methodology/Principal Findings
Border control and community containment measures implemented from April to June (Period I: April 28–May 21, Period II: May 22–June 18) 2009 were described. Number of individuals identified and disease characteristics were analyzed. For entry screening, a health declaration form and an infrared thermoscanner were used to detect symptomatic passengers. Passengers indicated for the rapid influenza test underwent the test followed by RT-PCR. Patients positive for H1N1 were isolated, and close contacts were quarantined. Entry cards were handed out to all asymptomatic passengers informing them about how to contact a health center in case they developed symptoms. Nine individuals were identified by entry screening and 1 during quarantine to have Pandemic (H1N1) 2009. Health monitoring by health centers was performed in period I for passengers arriving from affected countries and in period II for those who had come into contact with the individuals identified by entry screening. Health monitoring identified 3 infected individuals among 129,546 in Period I and 5 among 746 in Period II. Enhanced surveillance, which included mandatory reporting of details of the infected individuals, identified 812 individuals, 141 (18%) of whom had a history of international travel. Twenty-four of these 141 passengers picked up by enhanced surveillance had been developing symptoms on entry and were missed at screening.Conclusion/Significance
Symptomatic passengers were detected by the various entry screening measures put in place. Enhanced surveillance provided data for the improvement of public health measures in future pandemics. 相似文献26.
27.
28.
High salinity is an environmental factor that inhibits plant growth and development, leading to large losses in crop yields.
We report here that mutations in SIZ1 or PHO2, which cause more accumulation of phosphate compared with the wild type, enhance tolerance to salt stress. The siz1 and pho2 mutations reduce the uptake and accumulation of Na+. These mutations are also able to suppress the Na+ hypersensitivity of the sos3-1 mutant, and genetic analyses suggest that SIZ1 and SOS3 or PHO2 and SOS3 have an additive effect on the response to salt stress. Furthermore, the siz1 mutation cannot suppress the Li+ hypersensitivity of the sos3-1 mutant. These results indicate that the phosphate-accumulating mutants siz1 and pho2 reduce the uptake and accumulation of Na+, leading to enhanced salt tolerance, and that, genetically, SIZ1 and PHO2 are likely independent of SOS3-dependent salt signaling. 相似文献
29.
Takashi Seino Shintaro Kawasaki Mariko Shimokawa Hiroki Tamagawa Kohta Toshimitsu Masayuki Fujii Yuki Ohta Mami Matano Kosaku Nanki Kenta Kawasaki Sirirat Takahashi Shinya Sugimoto Eisuke Iwasaki Junichi Takagi Takao Itoi Minoru Kitago Yuko Kitagawa Takanori Kanai Toshiro Sato 《Cell Stem Cell》2018,22(3):454-467.e6
30.
Effects of Aspergillus oryzae-proteolipid (PL) on the formation of high concentrations of alcohol, more than 20% as in sake brewing, have been studied. Electron microscopy revealed that there were no vacuoles but many lipid deposits in cytoplasm of the alcoholtolerant cells of Saccharomyces sake Kyokai No. 7, which were obtained by the anaerobic culture supplemented with PL. Sphaeroplasts from the alcohol-tolerant cells were stable in 20% alcohol, whereas those from the untolerant cells grown anaerobically in the PL-unsupplemented media were ruptured. The cell membrane became alcohol-endurable in the anaerobic cultures with PL. Synthetic phospholipid promoted yeast growth and the fermentative activity, whereas a small amount of sterol ester enhanced the alcohoi-endurability. The supplementation of both lipids anaerobically induced physiological properties characteristic of the alcohol-tolerant cells. 相似文献