全文获取类型
收费全文 | 772篇 |
免费 | 39篇 |
国内免费 | 2篇 |
专业分类
林业 | 57篇 |
农学 | 15篇 |
基础科学 | 6篇 |
182篇 | |
综合类 | 131篇 |
农作物 | 21篇 |
水产渔业 | 21篇 |
畜牧兽医 | 307篇 |
园艺 | 34篇 |
植物保护 | 39篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 32篇 |
2012年 | 45篇 |
2011年 | 44篇 |
2010年 | 20篇 |
2009年 | 17篇 |
2008年 | 32篇 |
2007年 | 37篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 30篇 |
2003年 | 20篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1992年 | 13篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1974年 | 5篇 |
1971年 | 10篇 |
1970年 | 4篇 |
1969年 | 6篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
61.
Aguado E Richelme S Nuñez-Cruz S Miazek A Mura AM Richelme M Guo XJ Sainty D He HT Malissen B Malissen M 《Science (New York, N.Y.)》2002,296(5575):2036-2040
The transmembrane protein LAT (linker for activation of T cells) couples the T cell receptor (TCR) to downstream signaling effectors. Mice homozygous for a mutation of a single LAT tyrosine residue showed impeded T cell development. However, later they accumulated polyclonal helper T (TH) cells that chronically produced type 2 cytokines in large amounts. This exaggerated TH2 differentiation caused tissue eosinophilia and massive maturation of plasma cells secreting to immunoglobulins of the E and G1 isotypes. This paradoxical phenotype establishes an unanticipated inhibitory function for LAT that is critical for the differentiation and homeostasis of TH cells. 相似文献
62.
Terracciano A Abdel-Khalek AM Adám N Adamovová L Ahn CK Ahn HN Alansari BM Alcalay L Allik J Angleitner A Avia MD Ayearst LE Barbaranelli C Beer A Borg-Cunen MA Bratko D Brunner-Sciarra M Budzinski L Camart N Dahourou D De Fruyt F de Lima MP del Pilar GE Diener E Falzon R Fernando K Ficková E Fischer R Flores-Mendoza C Ghayur MA Gülgöz S Hagberg B Halberstadt J Halim MS Hrebícková M Humrichouse J Jensen HH Jocic DD Jónsson FH Khoury B Klinkosz W Knezević G Lauri MA Leibovich N Martin TA 《Science (New York, N.Y.)》2005,310(5745):96-100
Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity. 相似文献
63.
Blood-brain neutral amino acid transport activity is increased after portacaval anastomosis 总被引:21,自引:0,他引:21
In rats after portacaval anastomosis (an animal model of chronic liver disease), transport of tryptophan and other members of the large neutral amino acid group from blood to brain was markedly enhanced. Increased transport activity was apparently restricted to the neutral amino acid transport system, since brain uptake of glucose, inulin, and tyramine was unaffected while blood-brain arginine transport was significantly reduced. These results strikingly confirm the hypothesis that carrier-mediated blood-brain transport is the limiting factor determining the availability of the neutral amino acids to the brain. The encephalopathy associated with cirrhosis may be the result of abnormal neurotransmitter metabolism and neurotransmission secondary to increased neutral amino acid transport activity and an increased brain content of members of the neutral amino acid group. 相似文献
64.
Effects of basal debris on glacier flow 总被引:1,自引:0,他引:1
Iverson NR Cohen D Hooyer TS Fischer UH Jackson M Moore PL Lappegard G Kohler J 《Science (New York, N.Y.)》2003,301(5629):81-84
Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance. 相似文献
65.
Zhu Q Zhou O Coustel N Vaughan GB McCauley JP Romanow WJ Fischer JE Smith AB 《Science (New York, N.Y.)》1991,254(5031):545-548
Powder x-ray diffraction at 300 K on equilibrated samples of several nominal compositions chi in Rb(chi)C(60) is reported. In addition to the face-centered cubic (fcc) (chi = 3, superconducting), body-centered tetragonal (chi = 4), and body-centered cubic (bcc) (chi = 6) stoichiometric phases, direct evidence for a dilute fcc doped phase, 0 x c = 1, and for a substoichiometric bcc phase, chi approximately 5, is presented. In contrast, chi = 3 and chi = 4 appear to be line phases with nearly zero solubility of Rb vacancies and interstitials at 300 K. These results are summarized in a provisional binary phase diagram. 相似文献
66.
Fischer EA 《Science (New York, N.Y.)》1985,227(4693):1464-1465
67.
68.
W H Fischer 《Science (New York, N.Y.)》1971,171(973):828-829
69.
70.