全文获取类型
收费全文 | 242篇 |
免费 | 12篇 |
专业分类
254篇 |
出版年
2019年 | 6篇 |
2018年 | 3篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 5篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1994年 | 4篇 |
1990年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 13篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 7篇 |
1969年 | 5篇 |
1968年 | 8篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1961年 | 2篇 |
1960年 | 2篇 |
1956年 | 2篇 |
1949年 | 3篇 |
1946年 | 2篇 |
1943年 | 2篇 |
1942年 | 2篇 |
1940年 | 2篇 |
1937年 | 2篇 |
1929年 | 2篇 |
1926年 | 2篇 |
1920年 | 2篇 |
1902年 | 2篇 |
排序方式: 共有254条查询结果,搜索用时 0 毫秒
71.
The use of genetic markers in the context of conservation is largely being outcompeted by whole-genome data. Comparative studies between the two are sparse, and the knowledge about potential effects of this methodology shift is limited. Here, we used whole-genome sequencing data to assess the genetic status of peripheral populations of the wels catfish (Silurus glanis), and discuss the results in light of a recent microsatellite study of the same populations. The Swedish populations of the wels catfish have suffered from severe declines during the last centuries and persists in only a few isolated water systems. Fragmented populations generally are at greater risk of extinction, for example due to loss of genetic diversity, and may thus require conservation actions. We sequenced individuals from the three remaining native populations (Båven, Emån, and Möckeln) and one reintroduced population of admixed origin (Helge å), and found that genetic diversity was highest in Emån but low overall, with strong differentiation among the populations. No signature of recent inbreeding was found, but a considerable number of short runs of homozygosity were present in all populations, likely linked to historically small population sizes and bottleneck events. Genetic substructure within any of the native populations was at best weak. Individuals from the admixed population Helge å shared most genetic ancestry with the Båven population (72%). Our results are largely in agreement with the microsatellite study, and stresses the need to protect these isolated populations at the northern edge of the distribution of the species.Subject terms: Ecology, Genetics 相似文献
72.
R. D. Lillie 《Biotechnic & histochemistry》1940,15(4):159-165
Certain acid fuchsias stain connective tissue deep red after phosphomolybdotungstic mordanting in a modified Masson procedure, others are entirely unsatisfactory for mis purpose. Spectrophotometric examination gives no reliable criteria for separation of acid fuchsins satisfactory for this purpose from unsatisfactory ones. Sulphonation of basic fuchsin with 3.5 to 4 parts of 25-30% fuming H2SO4 to 1 part of dye gives a satisfactory product at temperatures as low as 65 to 70°C. in 30 minutes, while use of 5 to 7.5 parts of acid at this and at higher and lower temperatures gives unsatisfactory products. Satisfactory products may be produced with 15% fuming H2SO4 in similar quantities, and even with concentrated H2SO4, but some unconverted basic fuchsin remains with both and, with the latter, lower quantities give unsatisfactory products. Brief chemical studies indicate that oversulphonation may occur in the manufacture of acid fuchsin and that this is just as deleterious as undersulphonation. 相似文献
73.
R. D. Lillie 《Biotechnic & histochemistry》1941,16(1):1-6
Solutions at 0.3 g. per 100 cc. of equal parts of glycerin and methyl alcohol of various Wright, Giemsa, Leishman and Balch stains and similar eosinates of thiazene dyes give satisfactory wholesale staining of sections without differentiation when buffered with citric-acid and sodium-phosphate. Prestaining with alum hematoxylin adds to depth, density and permanence of nuclear staining, but decreases clarity. A satisfactory modification of Mayer's acid hemalum is described. The reaction should be pH 4.2 for neutral formalin or Orth fixation, pH 4.6 for acid formalin, pH 5.0 for Zenker formalin and pH 6.5 for ethyl or methyl alcohol or Carney fixation. Toluidine blue phloxhiate is found to be a quite desirable stain and its preparation is described. Clarite and clarite are definitely superior to neutral Canada balsam, and somewhat inferior in regard to fading compared with liquid petrolatum as mounting media for these Romanowsky stains. 相似文献
74.
Background and aims
Legume species in the fynbos vegetation of the Cape Floristic Region, that fix N2 in soils with low P, may have evolved for enhanced acquisition and efficient use of P. It was hypothesized that N2-fixing and combined-N supplied (N-supplied) A. linearis, P. calyptrata and C. genistoides are adapted to low P and would be relatively unresponsive to increased P of 100 μM.Methods
18 legume species were evaluated for their nodulation response to low P availability. The N X P interaction was then examined in A. linearis, P. calyptrata and C. genistoides reliant on either N2-fixation or 300 μM N (NH4NO3), and receiving 0.1, 1.0, 10 and 100 μM P (NaH2PO4).Results
In the species selection experiment, A. linearis, P. calyptrata and C. genistoides, with the greatest nodule fresh weight (FW) and nodule FW to root FW ratio, were the most prolific nodulating species. In the N X P experiment, with low P supply, the biomass of N2-fixing P. calyptrata and C. genistoides was consistently greater than that of N-supplied plants. In contrast, with high P supply of 100 μM P, all N-supplied plants accumulated more biomass than the corresponding N2-fixing plants. High P-use efficiency, poor down-regulation of P uptake and P storage was evident in A. linearis and P. calyptrata.Conclusion
The growth response to P and the significant N X P interactions indicate that N2-fixing and N-supplied plants were not adapted to low P, but rather colimited by both N and P. 相似文献75.
76.
Duncan CJ Sheehy SH Ewer KJ Douglas AD Collins KA Halstead FD Elias SC Lillie PJ Rausch K Aebig J Miura K Edwards NJ Poulton ID Hunt-Cooke A Porter DW Thompson FM Rowland R Draper SJ Gilbert SC Fay MP Long CA Zhu D Wu Y Martin LB Anderson CF Lawrie AM Hill AV Ellis RD 《PloS one》2011,6(7):e22271
Background
Inhibition of parasite growth is a major objective of blood-stage malaria vaccines. The in vitro assay of parasite growth inhibitory activity (GIA) is widely used as a surrogate marker for malaria vaccine efficacy in the down-selection of candidate blood-stage vaccines. Here we report the first study to examine the relationship between in vivo Plasmodium falciparum growth rates and in vitro GIA in humans experimentally infected with blood-stage malaria.Methods
In this phase I/IIa open-label clinical trial five healthy malaria-naive volunteers were immunised with AMA1/C1-Alhydrogel+CPG 7909, and together with three unvaccinated controls were challenged by intravenous inoculation of P. falciparum infected erythrocytes.Results
A significant correlation was observed between parasite multiplication rate in 48 hours (PMR) and both vaccine-induced growth-inhibitory activity (Pearson r = −0.93 [95% CI: −1.0, −0.27] P = 0.02) and AMA1 antibody titres in the vaccine group (Pearson r = −0.93 [95% CI: −0.99, −0.25] P = 0.02). However immunisation failed to reduce overall mean PMR in the vaccine group in comparison to the controls (vaccinee 16 fold [95% CI: 12, 22], control 17 fold [CI: 0, 65] P = 0.70). Therefore no impact on pre-patent period was observed (vaccine group median 8.5 days [range 7.5–9], control group median 9 days [range 7–9]).Conclusions
Despite the first observation in human experimental malaria infection of a significant association between vaccine-induced in vitro growth inhibitory activity and in vivo parasite multiplication rate, this did not translate into any observable clinically relevant vaccine effect in this small group of volunteers.Trial Registration
ClinicalTrials.gov [] NCT00984763相似文献77.
78.
79.
Iron gallein in Van Gieson technics, replacing iron hematoxylin 总被引:1,自引:0,他引:1
80.
In the search for hematoxylin substitutes 26 dyes were more or less extensively tested for performance as nuclear stains, usually in combination with aluminum, chronic, ferrous and ferric salts. Reports from the literature on hematoxylin substitutes were also considered, and efforts were made to obtain samples of favorably reported dyes and test them. The reports on anthocyanins include isolated reports on several berry juices and a considerable number of studies on Sambucus niger and Vaccinium myrtillus. None of these have so far been tested by us. Otherwise favorable reports have appeared on eleven synthetic dyes and on carmine, brazilin, and hematin. Except for one of the synthetics, naphthazarin, which is no longer fractured, we had samples of all of these. In addition, more or less unsuccessful trials were made on twelve dyestuffs, some of which were new syntheses designed to combine chelating capacity with nucleophilia. Following Fyg's report of blue nuclear staining with chrome alum carmine, trial was made to change the red nuclear stain of kernechtrot by altering the metal mordant. The most successful dyes were phenocyanin TC, gallein, fluorone black, alizarin cyanin BB and alizarin blue S. Celestin blue B with an iron mordant is quite successful if properly handled to prevent gelling of solutions. 相似文献