全文获取类型
收费全文 | 507篇 |
免费 | 11篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2013年 | 14篇 |
2012年 | 19篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1988年 | 5篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有518条查询结果,搜索用时 15 毫秒
371.
G. V. Khodachenko D. V. Mozgrin I. K. Fetisov T. V. Stepanova 《Plasma Physics Reports》2012,38(1):71-78
Experiments with quasi-steady high-current discharges in crossed E × B fields in various gases (Ar, N2, H2, and SF6) and gas mixtures (Ar/SF6 and Ar/O2) at pressures from 10−3 to 5 Torr in discharge systems with different configurations of electric and magnetic fields revealed a specific type of
stable low-voltage discharge that does not transform into an arc. This type of discharge came to be known as a high-current
diffuse discharge and, later, a nonsputtering impulse magnetron discharge. This paper presents results from experimental studies
of the plasma parameters (the electron temperature, the plasma density, and the temperature of ions and atoms of the plasma-forming
gas) of a high-current low-pressure diffuse discharge in crossed E × B fields. 相似文献
372.
Ethylene signalling and response pathway: a unique signalling cascade with a multitude of inputs and outputs 总被引:7,自引:0,他引:7
Plants as immobile organisms need to constantly monitor the changes in the environment to modify and adjust developmental and metabolic pathways accordingly. The responses to these environmental cues require an integrative mechanism where external and internal signals are detected and processed to trigger an appropriate 'reaction' in the plant. Hormones play a key role in mediating some of these integrative processes and in generating the response reactions. The identification and characterization of the basic hormone signalling components and their interactions represent the first step towards comprehensive understanding of plant responses to intrinsic and extrinsic cues. A relatively well-characterized ethylene signalling and response pathway, together with numerous evidences of its interactions with other signalling/response pathways, provide an excellent example to illustrate our current knowledge and perspective on how signal integration occurs in plants. 相似文献
373.
O. A. Stepanova 《Russian Journal of Marine Biology》2016,42(2):123-127
Monitoring of the Black Sea algal viruses in Sevastopol bays and Crimean water areas has been carried out since 2002. Based on the methods that were developed and patented by the author, more than 200 strains of algal viruses of five species of microalgae that are new to science were isolated: TvV (Tetraselmis viridis virus), DvV (Dunaliella viridis virus), PtV (Phaeodactylum tricornutum virus), PpV (Prorocentrum pusillum virus) and IgV (Isochrysis galbana virus). For the first time in the Black Sea, the Emiliania huxleyi virus (EhV) of microalgae was isolated. Using the method of electron microscopy, the Black Sea algal viruses were identified as icosahedral virions with respective sizes of 56–60, 45–48, 50–53, 88–92, and 128–132 nm, for the TvV, PtV, DvV, PpV and IgV viruses. The EhV size, as determined by the method of filtration, was within the range of 50–200 nm. In the IgV and EhV viruses we revealed a viral envelope. Based on their characters the isolated algal viruses were attributed to the Phycodnaeviridae. The maximum number of algal viruses was observed in the spring and autumn seasons, which is typical for their host phytoplankton species. The Black Sea algal viruses, TvV, PpV, IgV, and EhV, displayed no strict species specificity and have a wide range of available hosts. 相似文献
374.
Martin Novak Ivana Jackova Jan Curik Marketa Stepanova Frantisek Veselovsky Frantisek Buzek Melanie A. Vile Ivana Bufkova Ivana Valkova Marie Adamova Leona Bohdalkova Arnost Komarek 《Ecosystems》2016,19(6):1037-1050
Nitrogen (N) isotope systematics were investigated at two high-elevation ombrotrophic peat bogs polluted by farming and heavy industry. Our objective was to identify N sources and sinks for isotope mass balance considerations. For the first time, we present a time-series of δ15Ν values of atmospheric input at the same locations as δ15Ν values of living Sphagnum and peat. The mean δ15Ν values systematically increased in the order: input NH4 + (?10.0‰) < input NO3 ? (?7.9‰) < peat porewater (?5.6‰) < Sphagnum (?5.0‰) < shallow peat (?4.2‰) < deep peat (?2.2‰) < runoff (?1.4‰) < porewater N2O (1.4‰). Surprisingly, N of Sphagnum was isotopically heavier than N of the atmospheric input (P < 0.001). If partial incorporation of reactive N from the atmosphere into Sphagnum was isotopically selective, the residual N would have to be isotopically extremely light. Such N, however, was not identified anywhere in the ecosystem. Alternatively, Sphagnum may have contained an admixture of isotopically heavier N. Ambient air contains such N in the form of N2 (δ15ΝN2 = 0‰). Because high energy is required to break the triple bond, microbial N fixation is likely to proceed only under limited availability of pollutant N. Also for the first time, a δ15Ν comparison is presented between anoxic deeper peat and porewater N2O. Isotopically light N is removed from anoxic substrate by denitrification, whose final product, N2, escapes into the atmosphere. Porewater N2O is an isotopically heavy residuum following partial N2O reduction to N2. 相似文献
375.
Tania M Perehinec Saara NA Qazi Sanyasi R Gaddipati Vyvyan Salisbury Catherine ED Rees Philip J Hill 《BMC molecular biology》2007,8(1):80
Background
The Gateway recombinatorial cloning system allows easy and rapid joining of DNA fragments. Here we report the construction and evaluation of three different Gram-positive vectors that can be used with the Multisite Gateway cloning system to rapidly produce new gene arrangements in plasmid constructs for use in a variety of Gram-positive bacteria. 相似文献376.
377.
I A Krasil'nikov I M Iontova A A Sobolevskaia N I Fomina T M Stepanova A A Totolian 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1990,(1):33-37
The dynamics of scarlet fever morbidity in Leningrad for many years was studied and the absence of any effect produced by the existing system of preventive measures against this disease for the last 30 years was shown. On the basis of epidemiological and bacteriological data the authors came to the conclusion on the unity of the epidemic process of scarlet fever in the whole city and the relatively autonomous character of the process in individual districts. The necessity of the realization of epidemiological surveillance on streptococcal infection, with special emphasis on the multilevel social structure of the city and the wide use of the bacteriological diagnosis of streptococcal diseases, is substantiated. 相似文献
378.
E. V. Stepanova T. V. Fedorova O. N. Sorokina V. V. Volkov O. V. Koroleva A. T. Dembo 《Biochemistry. Biokhimii?a》2009,74(4):385-392
The effect of solvent phase transitions on catalytic activity and structure of the active site of laccase produced by the Basidiomycetes Coriolus hirsutus 072 was studied. As shown by small-angle X-ray scattering, laccase exists in solution as a mixture of monomeric and aggregated particles in the percent ratio 85: 15. This ratio did not change on phase transitions. A complex nature of laccase activity dynamics during thawing and further heating to 20°C was shown. Spontaneous oxidation of T1 copper center in the temperature range 12–20°C was not observed. According to spectral data, the structure of laccase active sites including all copper centers of types T1, T2, and T3 changes during the phase transition. 相似文献
379.
L. V. Stepanova G. L. Burygin L. Yu. Matora V. A. Bogatyrev M. K. Sokolova V. E. Nikitina 《Microbiology》2009,78(2):202-207
The complex of immunochemical methods was applied to study the ability of the lectin from the fungus Grifola frondosa (Fr.) S.F. Gray to interact with homologous and non-homologous rabbit and human polyclonal antibodies. The results of immunodot assay with the fragments of proteolytically cleaved antibodies demonstrated the binding of the lectin only with the Fab fragments (antigen-binding center) of homologous antibodies, which is evidence of specific “antigen-antibody” interaction. The revealed interaction of the lectin with non-homologous antibodies (rabbit antibodies to bacterial O-antigens and the commercial preparation of human g-globulin) is most likely accomplished due to the contact of the carbohydrate-binding region of the lectin with the carbohydrate moiety of the antibodies (“lectin-carbohydrate”). Immunofluorescence microscopy with homologous antibodies revealed that lectin was diffusely and unevenly distributed over the surface of the hyphae, forming agglomerates in the region of buckles and young shoots. 相似文献
380.
Yu. I. Dolgikh A. Yu. Stepanova E. S. Osipova A. Sh. Tashpulatov J. Hosp A. Ribarits E. Heberle-Bors A. M. Touraev 《Russian Journal of Plant Physiology》2010,57(1):118-123
The role of NtDCN1 gene in organogenesis in the culture of tobacco (Nicotiana tabacum L.) somatic tissues was studied. This gene is specifically expressed in tobacco microspores induced for somatic embryogenesis.
This gene knockout resulted in a disturbance of formation and development of embyoids from microspores. In leaf disks and
calli derived from tobacco lines with active and inactivated NtDCN1 gene, we studied induction of shoots and roots. A comparative analysis of tobacco line morphogenetic responses in vitro showed
that NtDCN1 gene inactivation enhanced shoot formation and suppressed rhizogenesis, whereas this gene reactivation returned organogenesis
processes to control level. Difference between lines was manifested only at a definite ratio between exogenous hormones supplied.
The involvement of NtDCN1 gene in line responses to exogenous auxin is discussed. The results obtained permit a supposition that the NtDCN1 gene is critical for regulation not only somatic embryogenesis but also organogenesis. 相似文献