全文获取类型
收费全文 | 629篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
林业 | 82篇 |
农学 | 29篇 |
174篇 | |
综合类 | 49篇 |
农作物 | 31篇 |
水产渔业 | 54篇 |
畜牧兽医 | 178篇 |
园艺 | 5篇 |
植物保护 | 47篇 |
出版年
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 89篇 |
2012年 | 29篇 |
2011年 | 45篇 |
2010年 | 19篇 |
2009年 | 28篇 |
2008年 | 34篇 |
2007年 | 30篇 |
2006年 | 37篇 |
2005年 | 36篇 |
2004年 | 30篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 3篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1962年 | 1篇 |
排序方式: 共有649条查询结果,搜索用时 15 毫秒
41.
Stamatoyannopoulos G Yoshida A Bacopoulos C Motulksy AG 《Science (New York, N.Y.)》1967,157(3790):831-833
A variant of glucose-6-phosphate dehydrogenase (G6PD), characterized by slower than normal electrophoretic migration and associated with mild deficiency of G6PD in the red cells, was detected in two unrelated Greek males. Electrophoretic, chromatographic, and enzymologic study indicated that the new mutant is structurally different from normal G6PD (B+) and from the Mediterranean variant associated with red-cell enzyme deficiency (B-). Convincing electrophoretic separation of the new variant from the normal B+ and the Mediterranean B- enzymes was achieved only by detailed electrophoretic study in different buffer systems and conditions. 相似文献
42.
Hypoxic ventilation of isolated perfused cat lungs caused the frequent appearance in pulmonary perfusates of biologically active substances, which included prostaglandins or prostaglandin-like compounds. In anesthetized cats, inhibition of prostaglandin biosynthesis with infusions of aspirin (more than 50 milligrams per kilogram) reduced the pulmonary vasoconstrictor and bronchoconstrictor responses to hypoxic breathing. 相似文献
43.
Induction of inflammatory arthropathy resembling rheumatoid arthritis in mice transgenic for HTLV-I 总被引:28,自引:0,他引:28
Y Iwakura M Tosu E Yoshida M Takiguchi K Sato I Kitajima K Nishioka K Yamamoto T Takeda M Hatanaka 《Science (New York, N.Y.)》1991,253(5023):1026-1028
Human T cell leukemia virus type-I (HTLV-I) is the etiologic agent of adult T cell leukemia and has also been suggested to be involved in other diseases such as chronic arthritis or myelopathy. To elucidate pathological roles of the virus in disease, transgenic mice were produced that carry the HTLV-I genome. At 2 to 3 months of age, many of the mice developed chronic arthritis resembling rheumatoid arthritis. Synovial and periarticular inflammation with articular erosion caused by invasion of granulation tissues were marked. These observations suggest a possibility that HTLV-I is one of the etiologic agents of chronic arthritis in humans. 相似文献
44.
The cerebellar flocculus has been implicated in vestibulo-oculomotor control. One major central input to this structure originates from brainstem cells in the paramedian tract (PMT), whose function is unknown. Here it is reported that PMT cells in the pons carry vestibular and eye movement signals and their pharmacological inactivation produces a leaky integrator combined with vestibular imbalance. The results suggest that PMT cells provide the cerebellum with sensory and motor signals that are essential for velocity-to-position integration, a common premotor process that is required in all motor systems. 相似文献
45.
Piro L Garmire G Garcia M Stratta G Costa E Feroci M Mészáros P Vietri M Bradt H Frail D Frontera F Halpern J Heise J Hurley K Kawai N Kippen RM Marshall F Murakami T Sokolov VV Takeshima T Yoshida A 《Science (New York, N.Y.)》2000,290(5493):955-958
We report on the discovery of two emission features observed in the x-ray spectrum of the afterglow of the gamma-ray burst (GRB) of 16 December 1999 by the Chandra X-ray Observatory. These features are identified with the Ly(alpha) line and the narrow recombination continuum by hydrogenic ions of iron at a redshift z = 1.00 +/- 0.02, providing an unambiguous measurement of the distance of a GRB. Line width and intensity imply that the progenitor of the GRB was a massive star system that ejected, before the GRB event, a quantity of iron approximately 0.01 of the mass of the sun at a velocity approximately 0.1 of the speed of light, probably by a supernova explosion. 相似文献
46.
The mechanism of alkali resistance in hemoglobin Rainier, an adult human hemoglobin variant (beta 145 tyrosinie --> histidinie), has been investigated. Alkali denaturation kinetics, electrophoretic and hybridization study. and ultracentrifuge analysis provided evidence for a monomeric beta Rainiier chain resisting denaturation at alkaline pH. These data provide evidence for a previously unrecognized effect of a single amino acid substitution, that is, the change of the alkali denaturation properties of monomneric chains. 相似文献
47.
The first stars fundamentally transformed the early universe by emitting the first light and by producing the first heavy elements. These effects were predetermined by the mass distribution of the first stars, which is thought to have been fixed by a complex interplay of gas accretion and protostellar radiation. We performed radiation-hydrodynamics simulations that followed the growth of a primordial protostar through to the early stages as a star with thermonuclear burning. The circumstellar accretion disk was evaporated by ultraviolet radiation from the star when its mass was 43 times that of the Sun. Such massive primordial stars, in contrast to the often-postulated extremely massive stars, may help explain the fact that there are no signatures of the pair-instability supernovae in abundance patterns of metal-poor stars in our galaxy. 相似文献
48.
Einsle O Tezcan FA Andrade SL Schmid B Yoshida M Howard JB Rees DC 《Science (New York, N.Y.)》2002,297(5587):1696-1700
A high-resolution crystallographic analysis of the nitrogenase MoFe-protein reveals a previously unrecognized ligand coordinated to six iron atoms in the center of the catalytically essential FeMo-cofactor. The electron density for this ligand is masked in structures with resolutions lower than 1.55 angstroms, owing to Fourier series termination ripples from the surrounding iron and sulfur atoms in the cofactor. The central atom completes an approximate tetrahedral coordination for the six iron atoms, instead of the trigonal coordination proposed on the basis of lower resolution structures. The crystallographic refinement at 1.16 angstrom resolution is consistent with this newly detected component being a light element, most plausibly nitrogen. The presence of a nitrogen atom in the cofactor would have important implications for the mechanism of dinitrogen reduction by nitrogenase. 相似文献
49.
Jagan Mohan Rao L Yada H Ono H Yoshida M 《Journal of agricultural and food chemistry》2002,50(11):3143-3146
A methanol extract of nagkesar (buds of Mammea longifolia), which showed strong radical scavenging activity, yielded 13 compounds by separations using column chromatography and HPLC. Structure elucidation of these compounds was achieved by (1)H and (13)C NMR, including DQF-COSY, TOCSY, DEPT, HMQC, HSQC, and HMBC. They include two new compounds, quercetin 3-O-(2' ',4' 'di-E-p-coumaroyl)-alpha-L-rhamno-pyranoside and quercetin 3-O-(3' ',4' '-di-E-p-coumaroyl)-alpha-L-rhamnopyranoside, along with known compounds kaempferol, quercetin, the isopropylidenedioxy derivative of shikimic acid, kaempferol 3-O-(2' ',4' '-di-E-p-coumaroyl)-alpha-L-rhamnopyranoside, kaempferol 3-O-(3' ',4' '-di-E-p-coumaroyl)-alpha-L-rhamnopyranoside, kaempferol 3-O-alpha-L-rhamnopyranoside, quercetin 3-O-alpha-L-rhamnopyranoside, shikimic acid, kaempferol 3-O-beta-D-glucopyranoside, quercetin 3-O-beta-D-glucopyranoside, and beta-sitosterol 3-O-beta-D-glucopyranoside. 相似文献
50.
Reduced immunogenicity of beta-lactoglobulin by conjugation with carboxymethyl dextran differing in molecular weight 总被引:2,自引:0,他引:2
Kobayashi K Hirano A Ohta A Yoshida T Takahashi K Hattori M 《Journal of agricultural and food chemistry》2001,49(2):823-831
To reduce the immunogenicity of beta-lactoglobulin (beta-LG), two beta-LG-carboxymethyl dextran (CMD) conjugates (Conj. 40 and Conj. 162) were prepared by using water-soluble carbodiimide (EDC). The molar ratios of beta-LG to CMD in Conj. 40 and Conj. 162 were 8:1 and 7:1, respectively. Each conjugate maintained approximately 50% of the retinol binding activity of beta-LG. Structural analyses by intrinsic fluorescence, CD spectra, and ELISA with monoclonal antibodies indicated that the surface of beta-LG in each conjugate was covered by CMD without great disruption of native conformation. By conjugation with CMD, the antibody response to beta-LG was reduced in BALB/c, C3H/He, and C57BL/6 mice, which was eminent in Conj. 162. The results of B cell epitope scanning using overlapping synthesized peptides showed that the linear epitope profiles of the conjugates were similar to those of beta-LG, whereas the antibody response to each epitope was reduced, which was eminent in Conj. 162. It was concluded that conjugation with CMD of higher molecular weight is effective in reducing the immunogenicity of beta-LG and that masking of epitopes by CMD is responsible for the reduced immunogenicity. 相似文献