全文获取类型
收费全文 | 463篇 |
免费 | 48篇 |
出版年
2021年 | 2篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 17篇 |
2014年 | 15篇 |
2013年 | 50篇 |
2012年 | 26篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 33篇 |
2006年 | 21篇 |
2005年 | 26篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 19篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有511条查询结果,搜索用时 31 毫秒
91.
The effects of suboptimal root zone temperatures (RZTs) on net translocation rates from the roots to the shoots and the concentrations
of Fe, Mn, Zn, and Cu were examined in maize grown in nutrient solution or soil. Plants were grown at 12 °C, 18 °C and 24
°C RZT. At each RZT, the growth-related shoot demand for nutrients was varied by independently modifying the temperature of
the shoot base (SBT) including the apical shoot meristem.
The net translocation rates of Mn and Zn from the roots to the shoots were reduced at low RZTs, irrespective of the SBT and
of the substrate (soil or nutrient solution). Obviously, the net translocation rates of Mn and Zn at low RZT were mainly regulated
by temperature effects on the roots and not by the chemical nutrient availability in the rhizosphere or by shoot growth rate
as controlled by SBTs. When both RZT and SBT were reduced, the decrease in net translocation rates of Mn and Zn was similar
to the decline in the shoot growth rate and concentrations of Mn and Zn in the shoot fresh matter were not greatly affected
or were even increased by low RZT. However, at high SBT and low RZT in nutrient solution, the depressed net translocation
rates of Mn and Zn combined with the increased shoot growth resulted in significantly decreased concentrations of Mn and Zn
in the shoot, indicating that Mn and Zn may become deficient even at high chemical availability.
By contrast to Mn and Zn, the net translocation rates of Fe and Cu at all RZTs were markedly enhanced by increased SBTs. Accordingly,
the concentrations of Fe and Cu in the shoot fresh matter were not greatly affected by RZTs, irrespective of the SBTs. These
results indicate that the ability of roots to supply Fe and Cu to the shoot was internally regulated by the growth related
shoot demand per unit of roots.
Deceased 21 September 1996
Deceased 21 September 1996 相似文献
92.
Test plantings with varieties ofLolium multiflorum andL perenne were harvested 4 to 7 times a year in 1991 and 1992. Samples were checked for the presence ofFusaria, the mycotoxins zearalenone, T-2 toxin, and diacetoxyscirpenol (DAS). Spectrum of species and the incidence ofFusaria and fusariotoxins are discussed in relation to the influencing factors site, variety ofLolium, harvesting time and year. Depending on these factors, 41 % to 100 % of the samples wereFusarium positive. Differences in infestation with Fusarium among varieties ofLolium perenne were dependent on location and did not correlate with yield. The six species ofFusarium pathogenic toLolium spp. (F. graminearum, F. culmorum, F. avenaceum, F. oxysporum, F. solani, and F. acuminatum) totaled 35.7 % of all the isolated strains. 14 species could be isolated fromLolium samples (descending frequency):F. culmorum, F. sambucinum, F. equiseti, F. acuminatum, F. semitectum, F. oxysporum, F. subglutinans, F. avenaceum, F. sporotrichioides, F. proliferatum, F. tricinctum, F. anthophilum, F. dimerum and F. graminearum. For the detection ofFusaria a promising new immunological method is presented. It is based on the genus specific production of exopolysaccharides byFusarium species. Mycotoxin contents in grass ranged from 0.01 to 4.75 ppm for zearalenone with 67 % positive samples and 0.3 % samples above 1 ppm, 0.04 to 2.78 ppm for T-2 toxin with 25 % positive samples and 2.8 % samples above 1 ppm, and 0.003 to 0.06 for DAS with 21.6 % positive samples. In silages, no T-2 toxin was detectable. IsolatedFusarium strains were checked for the ability to produce the mycotoxins zearalenone, T-2 toxin and DAS in culture. Most of the strains were positive for at least one of the toxins. 相似文献
93.
94.
Axel H. Meyer Karin Schmuck Corinne Morel William Wishart Hermann Lübbert Peter Engels 《Genomics》1996,38(3):435
Phospholipases A2 (PLA2) form an extended class of enzymes that play an important role in signal transduction. Phospholipase A2-like (PLA2L) belongs to the secreted forms of phospholipases A2, but constitutes a new subgroup. We have assigned the gene for this enzyme to human chromosome 8q24–qter using fluorescencein situhybridization and radiation hybrid mapping techniques. 相似文献
95.
Matthias Mag Jochen Muth Kerstin Jahn Anusch Peyman Gerhard Kretzschmar Joachim W. Engels Eugen Uhlmann 《Bioorganic & medicinal chemistry》1997,5(12):2213-2220
A method for the synthesis of chimeric oligodeoxynucleotides comprised of phosphodiester and phenylphosphonate [3′-O-P(=O)(C6H5)-O-5′] or phenylphosphono-thioate [3′-O-P(=S)(C6H5)-O-5′] linkages has been developed. Synthesis was performed using suitably protected nucleoside phenylphosphonamidites as building blocks following an adjusted solid-phase phosphoramidite synthesis protocol. The new oligodeoxy-nucleotide analogues were characterized by electrospray ionization- and matrix-assisted laser desorption mass spectrometry, as well as by 31P NMR spectroscopy. Additionally, their binding properties to complementary oligodeoxynucleotides has been studied. 相似文献
96.
Marie-Josee MF Lemoy Angela Colagross Schouten Don R Canfield 《Comparative medicine》2016,66(1):59-62
Bioabsorbable hemostatic agents such as oxidized regenerated cellulose are widely used to control intraoperative diffuse capillary bleeding. Compared with electrocautery or ligation, oxidized regenerated cellulose has the advantage of controlling bleeding without occluding the vessel lumen or causing thermal injuries to adjacent tissue. Although the manufacturer recommends removal of the material once hemostasis is achieved, oxidized regenerated cellulose is a bioabsorbable hemostatic agent and is often left in the surgical bed to prevent subsequent bleeding after surgical closure. However, noninvasive imaging techniques have revealed granulomatous foreign-body reactions that mimic infection or tumor recurrence. We present a case report of sterile peritonitis and granuloma formation secondary to the presence of oxidized regenerated cellulose after intestinal resection to excise a colonic adenocarcinoma in an aged rhesus macaque.Bioabsorbable hemostatic agents such as oxidized regenerated cellulose (for example, Surgicel) are widely used to control intraoperative diffuse capillary bleeding. Compared with electrocautery or ligation, oxidized regenerated cellulose has the advantage of controlling bleeding without occluding the vessel lumen or causing thermal injuries to adjacent tissue.16Oxidized regenerated cellulose is formed by dissolving the α-cellulose of decomposed wood pulp in an alkaline solution and subsequently regenerating it as a continuous fiber. This fiber is then woven into a gauze and oxidized.17,22 Oxidized regenerated cellulose is supplied as a substrate that is flexible, malleable, and trimable.16The mechanism of hemostasis of oxidized regenerated cellulose is reportedly associated with its caustic activity.2 The oxidation of cellulose produces a low-pH organic acid that reacts with blood, thus forming an artificial clot and causing platelet aggregation.18Although the manufacturer recommends the removal of oxidized regenerated cellulose once hemostasis is achieved,8 the product, a bioabsorbable hemostatic agent, is often left in situ within the surgical bed to prevent bleeding after surgical procedures. The biodegradation and elimination of oxidized regenerated cellulose from the tissue occurs in 2 phases.14 Polyanhydroglucuronic acid, the major functional unit of oxidized regenerated cellulose, is readily soluble. This acid is degraded extracellulary and systematically cleared from the system approximately 18 h after implantation.13,14 The remaining fibrous residue, however, requires macrophage phagocytosis for clearance and can be observed within macrophages for at least 48 h after implantation.13 Unfortunately, these fibrous residues have a prolonged degradation, and their persistence for as long as 7 mo after surgery has been confirmed histologically.7Despite the biocompatibility of oxidized regenerated cellulose, granulomatous foreign-body reactions that imitate infection or tumor recurrence have been revealed by using noninvasive imaging techniques.1,11,12,15,17,18,22 Here we describe a case of peritonitis and granuloma formation secondary to the presence of oxidized regenerated cellulose after an intestinal resection to excise a colonic adenocarcinoma in an aged rhesus macaque. 相似文献
97.
98.
99.
100.
Synthesis and selective cleavage of oligodeoxyribonucleotides containing non-chiral internucleotide phosphoramidate linkages. 总被引:3,自引:3,他引:0
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Oligodeoxynucleotides containing phosphoramidate internucleotide links 3'-OP(O)NH-5' have been prepared using standard solid phase phosphoramidite techniques. For the incorporation of the phosphoramidate linkages we have used monomer as well as dimer building blocks. With the monomer 3'-phosphoramidite building blocks, which are derived from 5'-amino-2',5'-dideoxynucleosides, it is possible to incorporate phosphoramidate links into specific positions within an oligodeoxynucleotide. Furthermore the synthesis of several dinucleoside phosphate derivatives which are linked by phosphoramidate bonds are described. The internucleotide phosphoramidate linkage was performed using the Staudinger reaction followed by a Michaelis-Arbuzov type transformation. After 3'-phosphitylation these dinucleosides are compatible with the current phosphoramidite methodology of oligodeoxynucleotide synthesis. 相似文献