全文获取类型
收费全文 | 389篇 |
免费 | 35篇 |
专业分类
424篇 |
出版年
2023年 | 4篇 |
2021年 | 5篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 23篇 |
2012年 | 23篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 12篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 11篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 10篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1966年 | 5篇 |
1959年 | 3篇 |
1932年 | 3篇 |
排序方式: 共有424条查询结果,搜索用时 15 毫秒
1.
2.
Joachim Haupt 《Cell and tissue research》1969,101(3):401-407
Zusammenfassung Die Feinstruktur der Maxillarnephridien von Scutigerella immaculata Newport mit ihren drei Abschnitten Sacculus, Tubulus und Ausführgang wurde untersucht. Die Zellen des Sacculus sind typische Podocyten, an denen eine Ultrafiltration ablaufen kann. Möglicherweise wird die Filtration durch einen den Sacculus umgebenden Muskel unterstützt. Die Zellen des Tubulus zeigen basale Einfaltungen und im proximalen Teil auch Mikrovilli. Sowohl im Tubulus als auch im Ausführgang, dessen Zellen ebenfalls basale Einfaltungen aufweisen, werden Reabsorptionsprozesse vermutet.
The fine structure of the maxillary kidney of the garden centipede, Scutigerella immaculata Newport (Symphyla, Myriapoda)
Summary The fine structure of the maxillary kidney of Scutigerella immaculata Newport (Symphyla) has been investigated. It may be compared with segmental organs of other Arthropoda having an end-sac which forms a primary urine by ultrafiltration. The filtration may be supported by a muscle surrounding the end-sac. The tubular part of the nephridium and the efferent duct show structures which may be involved in reabsorption.相似文献
3.
Joachim Haupt 《Cell and tissue research》1970,110(4):588-599
Zusammenfassung Am Präanalsegment von Scutigerella befindet sich ein Paar Trichobothrien, das komplizierter gebaut ist als entsprechende Sinnesorgane anderer Arthropoden. Die distalen Fortsätze von sechzehn Sinneszellen stehen mit der Gelenkmembran des nach allen Seiten beweglichen Sinneshaares in Verbindung. Aus ihrer Anordnung kann geschlossen werden, daß Scutigerella mit Hilfe des Trichobothriums mindestens acht verschiedene Richtungen unterscheiden kann. Der adäquate Reiz für die Trichobothrien dürften Luftbewegungen sein.
Sense organs of symphyla (Myriapoda)I. Ultrastructure of the trichobothrium of Scutigerella immaculata newport
Summary One pair of trichobothria is situated on the lateral portions of the preanal segment of Scutigerella. They are rather complicated compared to similar organs of other Arthroods. The distal portions of 16 sense cells are connected to the elastic membrane of the sense hair which can be turned in every direction. From the arrangement of the distal parts of the sense cells it may be concluded that Scutigerella can distinguish at least eight different directions. Probably movements of the air are the adequate stimulus for the trichobothrium.
Für technische Mitarbeit danke ich Frl. M. Genehr und Fr. G. Schröer, für die Anfertigung der Zeichnung Fr. C. St. Friedemann. 相似文献
4.
5.
The human 5-HT1A receptor expressed in HeLa cells stimulates sodium-dependent phosphate uptake via protein kinase C 总被引:1,自引:0,他引:1
J R Raymond A Fargin J P Middleton J M Graff D M Haupt M G Caron R J Lefkowitz V W Dennis 《The Journal of biological chemistry》1989,264(36):21943-21950
Regulation of phosphate uptake was studied in HeLa cell lines after transfection with DNA encoding the human 5-HT1A receptor. Phosphate uptake was saturable and greater than 90% sodium-dependent, with Vmax approximately 30-35% without changing Km. Treatment with 5-HT or the 5-HT1A-specific agonist 8-OH-2-(di-n-propylamino)1,2,3,4-tetrahydronaphthalene increased Vmax approximately 40% without affecting Km. This effect was blocked by pretreatment with the 5-HT1 antagonists, methiothepine and spiperone, or pertussis toxin. Surprisingly, the stimulation was not secondary to an inhibition of adenylyl cyclase because 5-HT stimulated phosphate uptake approximately 20% in the presence of 1 mM 8-Br-cAMP. Rather, the primary pathway linked to the stimulation of phosphate uptake involved activation of protein kinase C because (i) 5-HT measurably activated protein kinase C in these cells, (ii) activators of protein kinase C (phorbol esters and diacylglycerol analogues) stimulated phosphate uptake in these cells (iii) the half-maximal doses for 5-HT-induced phosphatidylinositol hydrolysis and stimulation of phosphate uptake were virtually equivalent, and both effects were equally sensitive to pertussis toxin, and (iv) the stimulation was markedly attenuated in cells made deficient in protein kinase C. These results demonstrate that the stimulation of phosphatidylinositol hydrolysis by the 5-HT1A receptor can generate physiologically measurable effects on cellular transport and suggest that such accessory pathways may play a prominent role in signal transduction. 相似文献
6.
Maja Wiprächtiger Melanie Haupt Andreas Froemelt Magdalena Klotz Claudio Beretta Dominik Osterwalder Vanessa Burg Stefanie Hellweg 《Journal of Industrial Ecology》2023,27(1):254-271
Industrial ecology (IE) methodologies, such as input/output or material flow analysis and life cycle assessment (LCA), are often used for the environmental evaluation of circular economy strategies. Up to now, an approach that utilizes these methods in a systematic, integrated framework for a holistic assessment of a geographic region's sustainable circular economy potential has been lacking. The approach developed in this study (IE4CE approach) combines IE methodologies to determine the environmental impact mitigation potential of circular economy strategies for a defined geographic region. The approach foresees five steps. First, input/output analysis helps identify sectors with high environmental impacts. Second, a refined analysis is conducted using material flow and LCA. In step 3, circular strategies are used for scenario design and evaluated in step 4. In step 5, the assessment results are compiled and compared across sectors. The approach was applied to a case study of Switzerland, analyzing 8 sectors and more than 30 scenarios in depth. Carbon capture and storage (CCS) from waste incineration, biogas and cement production, food waste prevention in households, hospitality and production, and the increased recycling of plastics had the highest mitigation potential. Most of the scenarios do not influence each other. One exception is the CCS scenarios: waste avoidance scenarios decrease the reduction potential of CCS. A combination of scenarios from different sectors, including their impact on the CCS scenario potential, led to an environmental impact mitigation potential of 11.9 Mt CO2-eq for 2050, which equals 14% of Switzerland's current consumption-based impacts. 相似文献
7.
Proteinase Inhibitor II Gene Expression Induced by Electrical Stimulation and Control of Photosynthetic Activity in Tomato Plants 总被引:5,自引:0,他引:5
Herde Oliver; Fuss Heidemarie; Pena-Cortes Hugo; Fisahn Joachim 《Plant & cell physiology》1995,36(4):737-742
Mechanical damage and heat stimulation were used to activateproteinase inhibitor II (Pin2) gene expression in tomato plantsin both treated (local induction) and non-treated tissues (systemicinduction). Both stimuli have been shown to generate electricalsignals, leading to a systemic activation of gene expression.Treatment of tomato leaves with electrical current resultedin the accumulation of Pin2 mRNA in the local and systemic leaves.Additionally, all treatments inducing Pin2 gene activity gaverise to a significant alteration of stomatal aperture. However,heat stimulation provoked a different response in the stomatalparameters than mechanical wounding or electric treatment. Bothmechanical damage and electrical stimulation activated two characteristictime constants in the gas exchange relaxation kinetics. Conversely,heat stimulation resulted in only one major time constant. Theresults clearly show that direct current application to tomatoleaves initiates Pin2 mRNA accumulation locally and systemically.In addition, they suggest the participation of a second slowelectrical/hydraulic component in the wound response mechanismof tomato plants and a possible alternative pathway regulatingheat-induced Pin2 gene expression. (Received February 13, 1995; Accepted April 14, 1995) 相似文献
8.
Mycorrhizal and nonmycorrhizal roots of Allium schoenoprasum were tested for activities of α-mannosidase, β-glucosidase and arabinosidase. Mannosidase activity was higher by a factor
of two in mycorrhizal than in nonmycorrhizal root extracts. The apparent molecular weight of the enzyme was 152 kDa and its
KM was 1.25 mM in colonized roots and 1.85 mM in uncolonized roots. α-Mannosidase activity was further characterized by an acid
pH optimum and Zn2+ dependency. No significant differences could be found between mycorrhizal and nonmycorrhizal roots for β-glucosidase and
arabinosidase activities.
Accepted: 28 August 1995 相似文献
9.
A severe and a mild potato spindle tuber viroid isolate differ in three nucleotide exchanges only 总被引:5,自引:0,他引:5
Hans J. Gross Ursula Liebl Heidemarie Alberty Guido Krupp Horst Domdey Karla Ramm Heinz L. Sänger 《Bioscience reports》1981,1(3):235-241
Fingerprint analyses of two potato spindle tuber viroid (PSTV) isolates causing severe and mild symptoms~ respectively, in tomato exhibited defined differences in the RNase T1 and RNase A fingerprints. The complete sequencing of the mild isolate and the comparison of its primary structure with the previously established one of the pathogenic type strain revealed that oligonucleotides CAAAAAAG, CUUUUUCUCUAUCUUACUUG, and AAAAAAGGAC in the severe strain are replaced by CAAUAAG, CUUUUUCUCUAUCUUUCUUUG, AAU, and AAGGAC in the 'mild' strain. Thus, three nucleotide exchanges at different sites of the molecule may change a pathogenic viroid to a practically non-pathogenic isolate. The possible correlation between the secondary structure in a defined region of the PSTV molecule and its pathogenicity for tomato is discussed. 相似文献
10.
Under the protection of ascorbic acid a 2-hydroxyestrone bovine serum albumin conjugate was prepared containing intact 2-hydroxyestrone as determined by gas chromatographymass spectrometry. Using this antigen highly specific antibodies were raised in rabbits. Cross-reactivity for 2-hydroxyestradiol and 2-hydroxyestriol was 26 and 4.5%, respectively. An assay procedure of 2-hydroxyestrone in human plasma is described. Using special precautions the assay allows the determination of 2-hydroxyestrone in plasma samples of women (50–95 pg/ml), pregnant women (105–220 pg/ml), men (45–65 pg/ml) and children (20–40 pg/ml). 相似文献