全文获取类型
收费全文 | 9803篇 |
免费 | 924篇 |
国内免费 | 97篇 |
专业分类
10824篇 |
出版年
2023年 | 47篇 |
2022年 | 159篇 |
2021年 | 213篇 |
2020年 | 127篇 |
2019年 | 158篇 |
2018年 | 172篇 |
2017年 | 156篇 |
2016年 | 281篇 |
2015年 | 524篇 |
2014年 | 495篇 |
2013年 | 605篇 |
2012年 | 770篇 |
2011年 | 703篇 |
2010年 | 451篇 |
2009年 | 390篇 |
2008年 | 522篇 |
2007年 | 463篇 |
2006年 | 475篇 |
2005年 | 434篇 |
2004年 | 371篇 |
2003年 | 347篇 |
2002年 | 284篇 |
2001年 | 249篇 |
2000年 | 246篇 |
1999年 | 198篇 |
1998年 | 88篇 |
1997年 | 67篇 |
1996年 | 75篇 |
1995年 | 65篇 |
1994年 | 48篇 |
1993年 | 62篇 |
1992年 | 125篇 |
1991年 | 97篇 |
1990年 | 105篇 |
1989年 | 110篇 |
1988年 | 79篇 |
1987年 | 87篇 |
1986年 | 89篇 |
1985年 | 96篇 |
1984年 | 63篇 |
1983年 | 66篇 |
1982年 | 52篇 |
1981年 | 53篇 |
1980年 | 46篇 |
1979年 | 78篇 |
1978年 | 63篇 |
1977年 | 46篇 |
1976年 | 50篇 |
1974年 | 43篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Recent data indicate an unexpected requirement for proteins that were hitherto considered to be dedicated to DNA repair to facilitate the faithful disjunction of sister chromatids in anaphase. These include the Bloom's syndrome gene product, BLM and its partners, as well as a number of proteins that are important for preventing Fanconi anemia (FA) in man. As part of an analysis of the roles of these proteins in mitosis, we identified a novel class of anaphase bridge structure, called an ultra-fine anaphase bridge (UFB). These UFBs are also defined by the presence of a SNF2 family protein called PICH. In this review, we will discuss the possible sources of UFBs, and how the BLM, PICH and FA proteins might serve to process these structures in order to maintain genome stability. 相似文献
972.
Kim D Kim SN Baik KS Park SC Lim CH Kim JO Shin TS Oh MJ Seong CN 《Journal of microbiology (Seoul, Korea)》2011,49(1):141-145
A metagenomic fosmid library was constructed using genomic DNA isolated from abalone intestine. Screening of a library of
3,840 clones revealed a 36 kb insert of a cellulase positive clone (pAMHElO). A shotgun clone library was constructed using
the positive clone (pAMHElO) and further screening of 3,840 shotgun clones with an approximately 5 kb insert size using a
Congo red overlay revealed only one cellulase positive clone (pAMHL9). The pAMHL9 consisted of a 5,293-bp DNA sequence and
three open reading frames (ORFs). Among the three ORFs, cellulase activity was only shown in the recombinant protein (CelAMll)
coded by ORF3, which showed 100% identity with outer membrane protein A from Vibrio alginolyticus 12G01, but no significant sequence homology to known cellulases. The expressed protein (CelAMll) has a molecular weight of
approximately 37 kDa and the highest CMC hydrolysis activity was observed at pH 7.0 and 37°C. The carboxymethyl cellulase
activity was determined by zymogram active staining and different degraded product profiles for CelAMll were obtained when
cellotetraose and cellopentaose were used as the substrates, while no substrate hydrolysis was observed on oligosaccharides
such as cellobiose and cellotriose. 相似文献
973.
MicroRNAs and cystic fibrosis--an epigenetic perspective 总被引:1,自引:0,他引:1
CF (cystic fibrosis) is a recessive genetic disease caused by mutations of the CFTR (cystic fibrosis transmembrane conductance regulator), a cAMP-activated anion channel, exhibiting a multitude of clinical manifestations including lung inflammation/infection, pancreatic insufficiency/diabetes, intestinal obstruction and infertility in both sexes. While mutation DF508 is found in 70% of CF patients, large variation in disease phenotypes and severity is observed among the patients. This review discusses current theories accounting for the disease variations and puts forth an epigenetic hypothesis involving microRNAs. 相似文献
974.
E-Hyun Shin Chan Park Hyun kyung Kim Dong-Kyu Lee Soon-Il Kim Hyesook Kang Kyu-Sik Chang 《Journal of Asia》2011,14(3):233-236
Field-collected populations of mayflies, Ephemera orientalis were tested for susceptibility to 10 different insecticides using a direct-contact mortality bioassay. Ephemera orientalis subimagoes were susceptible to the insecticides chlorpyrifos, fenitrothion and chlorfenapyr with LD50 values of 69.7, 78.8 and 81.9 μg/♀, and adults had LD50 values of 71.9, 78.8 and 85.4 μg/♀, respectively. Susceptibility ratios (SRs) of subimagoes and adults of E. orientalis to the 10 insecticides were 1.0 to1.2 folds. The mayflies showed higher susceptibility to organophosphates than to pyrethroids. The SRs of Anopheles sinensis to E. orientalis were 514 to 1438 folds higher for organophosphates (LD50 values of 0.05 to 0.23 μg/♀) and 62 to 1155 folds higher for pyrethroids (LD50 values of 0.13 to 2.41 μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3595 folds higher for organophosphates with LD50 values of 0.02–0.17 μg/♀ and 81 to 1365 folds higher for pyrethroids with LD50 values of 0.11–1.83 μg/♀. These results indicate that the use of ineffective insecticides will result in unsatisfactory control against field populations of the subimagoes and adults of E. orientalis. 相似文献
975.
976.
The discovery of pyrrolysine not only expanded the set of the known proteinogenic amino acids but also revealed unusual features of its encoding mechanism. The engagement of a canonical stop codon and a unique aminoacyl-tRNA synthetase-tRNA pair that can be used to accommodate a broad range of unnatural amino acids while maintaining strict orthogonality in a variety of prokaryotic and eukaryotic expression systems has proven an invaluable combination. Within a few years since its properties were elucidated, the pyrrolysine translational machinery has become a popular choice for the synthesis of recombinant proteins bearing a wide variety of otherwise hard-to-introduce functional groups. It is also central to the development of new synthetic strategies that rely on stop-codon suppression. 相似文献
977.
978.
979.
Dysfunction of hepatic insulin receptor tyrosine kinase (IRTK) causes the development of type 2 diabetes. However, the molecular mechanism regulating IRTK activity in the liver remains poorly understood. Here, we show that phosphoinositide 3-kinase enhancer A (PIKE-A) is a new insulin-dependent enhancer of hepatic IRTK. Liver-specific Pike-knockout (LPKO) mice display glucose intolerance with impaired hepatic insulin sensitivity. Specifically, insulin-provoked phosphoinositide 3-kinase/Akt signalling is diminished in the liver of LPKO mice, leading to the failure of insulin-suppressed gluconeogenesis and hyperglycaemia. Thus, hepatic PIKE-A has a key role in mediating insulin signal transduction and regulating glucose homeostasis in the liver. 相似文献
980.