全文获取类型
收费全文 | 1476篇 |
免费 | 99篇 |
国内免费 | 1篇 |
专业分类
林业 | 94篇 |
农学 | 42篇 |
基础科学 | 4篇 |
284篇 | |
综合类 | 146篇 |
农作物 | 65篇 |
水产渔业 | 115篇 |
畜牧兽医 | 682篇 |
园艺 | 31篇 |
植物保护 | 113篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 28篇 |
2020年 | 52篇 |
2019年 | 69篇 |
2018年 | 43篇 |
2017年 | 32篇 |
2016年 | 44篇 |
2015年 | 36篇 |
2014年 | 53篇 |
2013年 | 81篇 |
2012年 | 86篇 |
2011年 | 126篇 |
2010年 | 62篇 |
2009年 | 41篇 |
2008年 | 96篇 |
2007年 | 106篇 |
2006年 | 105篇 |
2005年 | 93篇 |
2004年 | 89篇 |
2003年 | 84篇 |
2002年 | 70篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有1576条查询结果,搜索用时 125 毫秒
991.
The effects of ions on bulk properties of liquid water, such as viscosity, have suggested that ions alter water's hydrogen-bonding network. We measured the orientational correlation time of water molecules in Mg(ClO4)2, NaClO4, and Na2SO4 solutions by means of femtosecond pump-probe spectroscopy. The addition of ions had no influence on the rotational dynamics of water molecules outside the first solvation shells of the ions. This result shows that the presence of ions does not lead to an enhancement or a breakdown of the hydrogen-bond network in liquid water. 相似文献
992.
Budowle B Schutzer SE Einseln A Kelley LC Walsh AC Smith JA Marrone BL Robertson J Campos J 《Science (New York, N.Y.)》2003,301(5641):1852-1853
Combating bioterrorism is a challenge to all of us. To be proactive, the U.S. Government has formalized the discipline of "microbial forensics" to deter and attribute perpetrators of such acts. This Policy Forum describes the foundations of the microbial forensics program: the creation of a national bioforensics laboratory, a partnership laboratory network, and a peer-consensus scientific working group and the promulgation of quality assurance guidelines. 相似文献
993.
994.
Many biological processes are regulated through the selective dephosphorylation of proteins. Protein serine-threonine phosphatases are assembled from catalytic subunits bound to diverse regulatory subunits that provide substrate specificity and subcellular localization. We describe a small molecule, guanabenz, that bound to a regulatory subunit of protein phosphatase 1, PPP1R15A/GADD34, selectively disrupting the stress-induced dephosphorylation of the α subunit of translation initiation factor 2 (eIF2α). Without affecting the related PPP1R15B-phosphatase complex and constitutive protein synthesis, guanabenz prolonged eIF2α phosphorylation in human stressed cells, adjusting the protein production rates to levels manageable by available chaperones. This favored protein folding and thereby rescued cells from protein misfolding stress. Thus, regulatory subunits of phosphatases are drug targets, a property used here to restore proteostasis in stressed cells. 相似文献
995.
Zhang SY Jouanguy E Ugolini S Smahi A Elain G Romero P Segal D Sancho-Shimizu V Lorenzo L Puel A Picard C Chapgier A Plancoulaine S Titeux M Cognet C von Bernuth H Ku CL Casrouge A Zhang XX Barreiro L Leonard J Hamilton C Lebon P Héron B Vallée L Quintana-Murci L Hovnanian A Rozenberg F Vivier E Geissmann F Tardieu M Abel L Casanova JL 《Science (New York, N.Y.)》2007,317(5844):1522-1527
Some Toll and Toll-like receptors (TLRs) provide immunity to experimental infections in animal models, but their contribution to host defense in natural ecosystems is unknown. We report a dominant-negative TLR3 allele in otherwise healthy children with herpes simplex virus 1 (HSV-1) encephalitis. TLR3 is expressed in the central nervous system (CNS), where it is required to control HSV-1, which spreads from the epithelium to the CNS via cranial nerves. TLR3 is also expressed in epithelial and dendritic cells, which apparently use TLR3-independent pathways to prevent further dissemination of HSV-1 and to provide resistance to other pathogens in TLR3-deficient patients. Human TLR3 appears to be redundant in host defense to most microbes but is vital for natural immunity to HSV-1 in the CNS, which suggests that neurotropic viruses have contributed to the evolutionary maintenance of TLR3. 相似文献
996.
Rich TH Hopson JA Musser AM Flannery TF Vickers-Rich P 《Science (New York, N.Y.)》2005,307(5711):910-914
A dentary of the oldest known monotreme, the Early Cretaceous Teinolophos trusleri, has an internal mandibular trough, which in outgroups to mammals houses accessory jaw bones, and probable contact facets for angular, coronoid, and splenial bones. Certain of these accessory bones were detached from the mandible to become middle ear bones in mammals. Evidence that the angular (homologous with the mammalian ectotympanic) and the articular and prearticular (homologous with the mammalian malleus) bones retained attachment to the lower jaw in a basal monotreme indicates that the definitive mammalian middle ear evolved independently in living monotremes and therians (marsupials and placentals). 相似文献
997.
Bleharski JR Li H Meinken C Graeber TG Ochoa MT Yamamura M Burdick A Sarno EN Wagner M Röllinghoff M Rea TH Colonna M Stenger S Bloom BR Eisenberg D Modlin RL 《Science (New York, N.Y.)》2003,301(5639):1527-1530
Leprosy presents as a clinical and immunological spectrum of disease. With the use of gene expression profiling, we observed that a distinction in gene expression correlates with and accurately classifies the clinical form of the disease. Genes belonging to the leukocyte immunoglobulin-like receptor (LIR) family were significantly up-regulated in lesions of lepromatous patients suffering from the disseminated form of the infection. In functional studies, LIR-7 suppressed innate host defense mechanisms by shifting monocyte production from interleukin-12 toward interleukin-10 and by blocking antimicrobial activity triggered by Toll-like receptors. Gene expression profiles may be useful in defining clinical forms of disease and providing insights into the regulation of immune responses to pathogens. 相似文献
998.
999.
1000.
Nodulation signaling in legumes requires NSP2, a member of the GRAS family of transcriptional regulators 总被引:1,自引:0,他引:1
Kaló P Gleason C Edwards A Marsh J Mitra RM Hirsch S Jakab J Sims S Long SR Rogers J Kiss GB Downie JA Oldroyd GE 《Science (New York, N.Y.)》2005,308(5729):1786-1789
Rhizobial bacteria enter a symbiotic interaction with legumes, activating diverse responses in roots through the lipochito oligosaccharide signaling molecule Nod factor. Here, we show that NSP2 from Medicago truncatula encodes a GRAS protein essential for Nod-factor signaling. NSP2 functions downstream of Nod-factor-induced calcium spiking and a calcium/calmodulin-dependent protein kinase. We show that NSP2-GFP expressed from a constitutive promoter is localized to the endoplasmic reticulum/nuclear envelope and relocalizes to the nucleus after Nod-factor elicitation. This work provides evidence that a GRAS protein transduces calcium signals in plants and provides a possible regulator of Nod-factor-inducible gene expression. 相似文献