全文获取类型
收费全文 | 2735篇 |
免费 | 14篇 |
国内免费 | 41篇 |
专业分类
系统科学 | 65篇 |
丛书文集 | 15篇 |
教育与普及 | 4篇 |
理论与方法论 | 53篇 |
现状及发展 | 953篇 |
研究方法 | 310篇 |
综合类 | 1302篇 |
自然研究 | 88篇 |
出版年
2019年 | 15篇 |
2018年 | 31篇 |
2017年 | 31篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 31篇 |
2013年 | 48篇 |
2012年 | 161篇 |
2011年 | 232篇 |
2010年 | 59篇 |
2009年 | 18篇 |
2008年 | 129篇 |
2007年 | 128篇 |
2006年 | 122篇 |
2005年 | 112篇 |
2004年 | 106篇 |
2003年 | 130篇 |
2002年 | 171篇 |
2001年 | 144篇 |
2000年 | 99篇 |
1999年 | 67篇 |
1997年 | 11篇 |
1992年 | 25篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 26篇 |
1979年 | 41篇 |
1978年 | 37篇 |
1977年 | 35篇 |
1976年 | 30篇 |
1975年 | 37篇 |
1974年 | 32篇 |
1973年 | 34篇 |
1972年 | 45篇 |
1971年 | 43篇 |
1970年 | 36篇 |
1969年 | 32篇 |
1968年 | 24篇 |
1967年 | 31篇 |
1966年 | 34篇 |
1965年 | 21篇 |
1958年 | 9篇 |
排序方式: 共有2790条查询结果,搜索用时 15 毫秒
81.
Ludovic?Le Guen Stéphane?Marchal Sandrine?Faure Pascal?de Santa BarbaraEmail author 《Cellular and molecular life sciences : CMLS》2015,72(20):3883-3896
The gastrointestinal tract develops from a simple and uniform tube into a complex organ with specific differentiation patterns along the anterior–posterior and dorso-ventral axes of asymmetry. It is derived from all three germ layers and their cross-talk is important for the regulated development of fetal and adult gastrointestinal structures and organs. Signals from the adjacent mesoderm are essential for the morphogenesis of the overlying epithelium. These mesenchymal–epithelial interactions govern the development and regionalization of the different gastrointestinal epithelia and involve most of the key morphogens and signaling pathways, such as the Hedgehog, BMPs, Notch, WNT, HOX, SOX and FOXF cascades. Moreover, the mechanisms underlying mesenchyme differentiation into smooth muscle cells influence the regionalization of the gastrointestinal epithelium through interactions with the enteric nervous system. In the neonatal and adult gastrointestinal tract, mesenchymal–epithelial interactions are essential for the maintenance of the epithelial regionalization and digestive epithelial homeostasis. Disruption of these interactions is also associated with bowel dysfunction potentially leading to epithelial tumor development. In this review, we will discuss various aspects of the mesenchymal–epithelial interactions observed during digestive epithelium development and differentiation and also during epithelial stem cell regeneration. 相似文献
82.
Daniel Tarrant Tobias von der Haar 《Cellular and molecular life sciences : CMLS》2014,71(21):4195-4206
Quantitative control of gene expression occurs at multiple levels, including the level of translation. Within the overall process of translation, most identified regulatory processes impinge on the initiation phase. However, recent studies have revealed that the elongation phase can also regulate translation if elongation and initiation occur with specific, not mutually compatible rate parameters. Translation elongation then limits the overall amount of protein that can be made from an mRNA. Several recently discovered control mechanisms of biological pathways are based on such elongation control. Here, we review the molecular mechanisms that determine ribosome speed in eukaryotic organisms, and discuss under which conditions ribosome speed can become the controlling parameter of gene expression levels. 相似文献
83.
Extremely low-coverage sequencing and imputation increases power for genome-wide association studies 总被引:1,自引:0,他引:1
Pasaniuc B Rohland N McLaren PJ Garimella K Zaitlen N Li H Gupta N Neale BM Daly MJ Sklar P Sullivan PF Bergen S Moran JL Hultman CM Lichtenstein P Magnusson P Purcell SM Haas DW Liang L Sunyaev S Patterson N de Bakker PI Reich D Price AL 《Nature genetics》2012,44(6):631-635
Genome-wide association studies (GWAS) have proven to be a powerful method to identify common genetic variants contributing to susceptibility to common diseases. Here, we show that extremely low-coverage sequencing (0.1-0.5×) captures almost as much of the common (>5%) and low-frequency (1-5%) variation across the genome as SNP arrays. As an empirical demonstration, we show that genome-wide SNP genotypes can be inferred at a mean r(2) of 0.71 using off-target data (0.24× average coverage) in a whole-exome study of 909 samples. Using both simulated and real exome-sequencing data sets, we show that association statistics obtained using extremely low-coverage sequencing data attain similar P values at known associated variants as data from genotyping arrays, without an excess of false positives. Within the context of reductions in sample preparation and sequencing costs, funds invested in extremely low-coverage sequencing can yield several times the effective sample size of GWAS based on SNP array data and a commensurate increase in statistical power. 相似文献
84.
Roscioli T Kamsteeg EJ Buysse K Maystadt I van Reeuwijk J van den Elzen C van Beusekom E Riemersma M Pfundt R Vissers LE Schraders M Altunoglu U Buckley MF Brunner HG Grisart B Zhou H Veltman JA Gilissen C Mancini GM Delrée P Willemsen MA Ramadža DP Chitayat D Bennett C Sheridan E Peeters EA Tan-Sindhunata GM de Die-Smulders CE Devriendt K Kayserili H El-Hashash OA Stemple DL Lefeber DJ Lin YY van Bokhoven H 《Nature genetics》2012,44(5):581-585
Walker-Warburg syndrome (WWS) is an autosomal recessive multisystem disorder characterized by complex eye and brain abnormalities with congenital muscular dystrophy (CMD) and aberrant a-dystroglycan glycosylation. Here we report mutations in the ISPD gene (encoding isoprenoid synthase domain containing) as the second most common cause of WWS. Bacterial IspD is a nucleotidyl transferase belonging to a large glycosyltransferase family, but the role of the orthologous protein in chordates is obscure to date, as this phylum does not have the corresponding non-mevalonate isoprenoid biosynthesis pathway. Knockdown of ispd in zebrafish recapitulates the human WWS phenotype with hydrocephalus, reduced eye size, muscle degeneration and hypoglycosylated a-dystroglycan. These results implicate ISPD in a-dystroglycan glycosylation in maintaining sarcolemma integrity in vertebrates. 相似文献
85.
Bis JC DeCarli C Smith AV van der Lijn F Crivello F Fornage M Debette S Shulman JM Schmidt H Srikanth V Schuur M Yu L Choi SH Sigurdsson S Verhaaren BF DeStefano AL Lambert JC Jack CR Struchalin M Stankovich J Ibrahim-Verbaas CA Fleischman D Zijdenbos A den Heijer T Mazoyer B Coker LH Enzinger C Danoy P Amin N Arfanakis K van Buchem MA de Bruijn RF Beiser A Dufouil C Huang J Cavalieri M Thomson R Niessen WJ Chibnik LB Gislason GK Hofman A Pikula A Amouyel P Freeman KB Phan TG Oostra BA Stein JL 《Nature genetics》2012,44(5):545-551
Aging is associated with reductions in hippocampal volume that are accelerated by Alzheimer's disease and vascular risk factors. Our genome-wide association study (GWAS) of dementia-free persons (n = 9,232) identified 46 SNPs at four loci with P values of <4.0 × 10(-7). In two additional samples (n = 2,318), associations were replicated at 12q14 within MSRB3-WIF1 (discovery and replication; rs17178006; P = 5.3 × 10(-11)) and at 12q24 near HRK-FBXW8 (rs7294919; P = 2.9 × 10(-11)). Remaining associations included one SNP at 2q24 within DPP4 (rs6741949; P = 2.9 × 10(-7)) and nine SNPs at 9p33 within ASTN2 (rs7852872; P = 1.0 × 10(-7)); along with the chromosome 12 associations, these loci were also associated with hippocampal volume (P < 0.05) in a third younger, more heterogeneous sample (n = 7,794). The SNP in ASTN2 also showed suggestive association with decline in cognition in a largely independent sample (n = 1,563). These associations implicate genes related to apoptosis (HRK), development (WIF1), oxidative stress (MSR3B), ubiquitination (FBXW8) and neuronal migration (ASTN2), as well as enzymes targeted by new diabetes medications (DPP4), indicating new genetic influences on hippocampal size and possibly the risk of cognitive decline and dementia. 相似文献
86.
87.
88.
This paper first shows that survey‐based expectations (SBE) outperform standard time series models in US quarterly inflation out‐of‐sample prediction and that the term structure of survey‐based inflation forecasts has predictive power over the path of future inflation changes. It then proposes some empirical explanations for the forecasting success of survey‐based inflation expectations. We show that SBE pool a large amount of heterogeneous information on inflation expectations and react more flexibly and accurately to macro conditions both contemporaneously and dynamically. We illustrate the flexibility of SBE forecasts in the context of the 2008 financial crisis. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
89.
Oswaldo Hernández-Gallegos Felipe de Jesús Rodríguez-Romero Petra Sánchez-Nava Fausto R. Méndez 《西北部美国博物学家》2011,69(1)
Multiple surveys carried out by herpetologists in México, D.F., during the 1980s failed to find specimens of Aspidoscelis septemvitatta (Squamata: Teiidae). However, 10 specimens were recently collected to the east of México, D.F., inside a protected area, Sierra de Santa Catarina. The Sierra de Santa Catarina has been heavily modified by human activity and habitation. Morphological and natural history information about the specimens are presented, as well as notes on locality. 相似文献
90.
Kalay E Yigit G Aslan Y Brown KE Pohl E Bicknell LS Kayserili H Li Y Tüysüz B Nürnberg G Kiess W Koegl M Baessmann I Buruk K Toraman B Kayipmaz S Kul S Ikbal M Turner DJ Taylor MS Aerts J Scott C Milstein K Dollfus H Wieczorek D Brunner HG Hurles M Jackson AP Rauch A Nürnberg P Karagüzel A Wollnik B 《Nature genetics》2011,43(1):23-26
Functional impairment of DNA damage response pathways leads to increased genomic instability. Here we describe the centrosomal protein CEP152 as a new regulator of genomic integrity and cellular response to DNA damage. Using homozygosity mapping and exome sequencing, we identified CEP152 mutations in Seckel syndrome and showed that impaired CEP152 function leads to accumulation of genomic defects resulting from replicative stress through enhanced activation of ATM signaling and increased H2AX phosphorylation. 相似文献