全文获取类型
收费全文 | 61篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
林业 | 2篇 |
农学 | 2篇 |
8篇 | |
综合类 | 21篇 |
农作物 | 6篇 |
水产渔业 | 9篇 |
畜牧兽医 | 23篇 |
园艺 | 1篇 |
植物保护 | 1篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 5篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2009年 | 1篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 1篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1986年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 5篇 |
1974年 | 1篇 |
排序方式: 共有73条查询结果,搜索用时 15 毫秒
11.
Densities for carbon dioxide measured by the upper atmospheric mass spectrometers on Viking 1 and Viking 2 are analyzed to yield height profiles for the temperature of the martian atmosphere between 120 and 200 kilometers. Densities for nitrogen and argon are used to derive vertical profiles for the eddy diffusion coefficient over the same height range. The upper atmosphere of Mars is surprisingly cold with average temperatures for both Viking 1 and Viking 2 of less than 200 degrees K, and there is significant vertical structure. Model calculations are presented and shown to be in good agreement with measured concentrations of carbon monoxide, oxygen, and nitric oxide. 相似文献
12.
Pang PT Teng HK Zaitsev E Woo NT Sakata K Zhen S Teng KK Yung WH Hempstead BL Lu B 《Science (New York, N.Y.)》2004,306(5695):487-491
Long-term memory is thought to be mediated by protein synthesis-dependent, late-phase long-term potentiation (L-LTP). Two secretory proteins, tissue plasminogen activator (tPA) and brain-derived neurotrophic factor (BDNF), have been implicated in this process, but their relationship is unclear. Here we report that tPA, by activating the extracellular protease plasmin, converts the precursor proBDNF to the mature BDNF (mBDNF), and that such conversion is critical for L-LTP expression in mouse hippocampus. Moreover, application of mBDNF is sufficient to rescue L-LTP when protein synthesis is inhibited, which suggests that mBDNF is a key protein synthesis product for L-LTP expression. 相似文献
13.
Sakurai Y Itou M Barbiellini B Mijnarends PE Markiewicz RS Kaprzyk S Gillet JM Wakimoto S Fujita M Basak S Wang YJ Al-Sawai W Lin H Bansil A Yamada K 《Science (New York, N.Y.)》2011,332(6030):698-702
The high-temperature superconducting cuprate La(2-x)Sr(x)CuO(4) (LSCO) shows several phases ranging from antiferromagnetic insulator to metal with increasing hole doping. To understand how the nature of the hole state evolves with doping, we have carried out high-resolution Compton scattering measurements at room temperature together with first-principles electronic structure computations on a series of LSCO single crystals in which the hole doping level varies from the underdoped (UD) to the overdoped (OD) regime. Holes in the UD system are found to primarily populate the O 2p(x)/p(y) orbitals. In contrast, the character of holes in the OD system is very different in that these holes mostly enter Cu d orbitals. High-resolution Compton scattering provides a bulk-sensitive method for imaging the orbital character of dopants in complex materials. 相似文献
14.
将伊氏锥虫克隆JGmc5用环磷酰胺处理的免疫抑制小鼠频繁地连续传代,并予以亚治疗剂量的苏拉明治疗,连续传代14次,历时88日,即获得对苏拉明具有高水平抗药性的伊氏锥虫群体。在用免疫活性正常的健康小鼠测定抗药性时,此抗苏拉明锥虫群体仍保持高水平的抗药性,CD100>400mg/kg。在以体外药敏试验测定时,其IC50为123.2μg/ml。实验结果表明,宿主免疫系统的损害,在实验条件下,可导致伊氏锥虫迅速产生抗药性。在野外条件下,机体免疫系统的损害对锥虫抗药性的产生可能也起一定作用。 相似文献
15.
Mun Sup Yoon Jeongran Lee Chang Yung Kim Jung Hoon Kang Eun Gi Cho Hyung Jin Baek 《Euphytica》2009,165(1):69-77
Approximately 7,000 accessions of Korean soybean (Glycine max (L.) Merrill) landraces, largely composed of three collections, the Korea Atomic Energy Research Institute’s soybean (KAS),
the Korean Crop Experiment Station’s soybean (KLS) and the Korean Agricultural Development and Technology Center’s soybean
(KADTC) collections, have been conserved at the Rural Development Administration (RDA) genebank in Korea. The accessions within
collections were classified based on their traditional uses such as sauce soybean (SA), sprouted soybean (SP), soybean for
cooking with rice (SCR), and OTHERS. A total of 2,758 accessions of Korean soybean landraces were used to profile and to evaluate
genetic structure using six SSR loci. A total of 110 alleles were revealed by at the six SSR loci. The number of alleles per
SSR locus ranged from 9 to 39 in Satt187 and Satt_074, respectively. The number of alleles ranged from 87 in the KADTC collection
to 96 in the KLS collection, and from 63 in the SCR group to 95 in the SP group. Nei’s average genetic diversity ranged from
0.68 to 0.70 across three collections, and 0.64 to 0.69 across the usage groups. The average between-group differentiation
(G
st) was 0.9 among collections, and 4.1 among the usage groups. The similar average diversity among three collections implies
that the genetic background of the three collections was quite similar or that there were a large number of duplicate accessions
in three collections. The selection from the four groups classified based upon usage may be a useful way to select accessions
for developing a Korean soybean landrace core collection at the RDA genebank. DNA profile information of accessions will provide
indications of redundancies or omissions and aid in managing the soybean collection held at the RDA genebank. The information
on diversity analysis could help to enlarge the genetic diversity of materials in breeding programs and could be used to develop
a core collection. 相似文献
16.
It is proposed that Saturn's satellite Titan is covered by an ocean one to several kilometers deep consisting mainly of ethane. If the ocean is in thermodynamic equilibrium with an atmosphere of 3 percent (mole fraction) methane, then its composition is roughly 70 percent ethane, 25 percent methane, and 5 percent nitrogen. Photochemical models predict that ethane is the dominant end product of methane photolysis so that the evolving ocean is both the source and sink for continuing photolysis. The coexisting atmosphere is compatible with Voyager data. 相似文献
17.
The DNA origami method, in which long, single-stranded DNA segments are folded into shapes by short staple segments, was used to create nucleic acid probe tiles that are molecular analogs of macroscopic DNA chips. One hundred trillion probe tiles were fabricated in one step and bear pairs of 20-nucleotide-long single-stranded DNA segments that act as probe sequences. These tiles can hybridize to their targets in solution and, after adsorption onto mica surfaces, can be examined by atomic force microscopy in order to quantify binding events, because the probe segments greatly increase in stiffness upon hybridization. The nucleic acid probe tiles have been used to study position-dependent hybridization on the nanoscale and have also been used for label-free detection of RNA. 相似文献
18.
Detailed cost-return of freshwater prawn farming in Hawaii is estimated for farms ranging in size from a minimum of 1 acre to a maximum of 100 acres. Major factors affecting cost and revenue are discussed. Freshwater prawn farming in Hawaii is profitable at the existing average annual production of 3 000 pounds/acre and at the existing average farm price of $3.00/pound for farms that are 10 acres or larger. Smaller farms are profitable only when operated as a family venture. 相似文献
19.
Genomic Sequence and Experimental Tractability of a New Decapod Shrimp Model,Neocaridina denticulata
Nathan J. Kenny Yung Wa Sin Xin Shen Qu Zhe Wei Wang Ting Fung Chan Stephen S. Tobe Sebastian M. Shimeld Ka Hou Chu Jerome H. L. Hui 《Marine drugs》2014,12(3):1419-1437
The speciose Crustacea is the largest subphylum of arthropods on the planet after the Insecta. To date, however, the only publically available sequenced crustacean genome is that of the water flea, Daphnia pulex, a member of the Branchiopoda. While Daphnia is a well-established ecotoxicological model, previous study showed that one-third of genes contained in its genome are lineage-specific and could not be identified in any other metazoan genomes. To better understand the genomic evolution of crustaceans and arthropods, we have sequenced the genome of a novel shrimp model, Neocaridina denticulata, and tested its experimental malleability. A library of 170-bp nominal fragment size was constructed from DNA of a starved single adult and sequenced using the Illumina HiSeq2000 platform. Core eukaryotic genes, the mitochondrial genome, developmental patterning genes (such as Hox) and microRNA processing pathway genes are all present in this animal, suggesting it has not undergone massive genomic loss. Comparison with the published genome of Daphnia pulex has allowed us to reveal 3750 genes that are indeed specific to the lineage containing malacostracans and branchiopods, rather than Daphnia-specific (E-value: 10−6). We also show the experimental tractability of N. denticulata, which, together with the genomic resources presented here, make it an ideal model for a wide range of further aquacultural, developmental, ecotoxicological, food safety, genetic, hormonal, physiological and reproductive research, allowing better understanding of the evolution of crustaceans and other arthropods. 相似文献
20.
Formaldehyde could have been produced by photochemical reactions in Earth's primitive atmosphere, at a time when it consisted mainly of molecular nitrogen, water vapor, carbon dioxide, and trace amounts of molecular hydrogen and carbon monoxide. Removal of formaldehyde from the atmosphere by precipitation can provide a source of organic carbon to the oceans at the rate of 10(11) moles per year. Subsequent reactions of formaldehyde in primeval aquatic environments would have implications for the abiotic synthesis of complex organic molecules and the origin of life. 相似文献