全文获取类型
收费全文 | 569篇 |
免费 | 24篇 |
出版年
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 30篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 25篇 |
2009年 | 16篇 |
2008年 | 37篇 |
2007年 | 24篇 |
2006年 | 9篇 |
2005年 | 23篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 13篇 |
2001年 | 18篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 11篇 |
1973年 | 5篇 |
1972年 | 11篇 |
1970年 | 6篇 |
1968年 | 7篇 |
1967年 | 5篇 |
1966年 | 5篇 |
1965年 | 4篇 |
1958年 | 5篇 |
1953年 | 4篇 |
1952年 | 4篇 |
排序方式: 共有593条查询结果,搜索用时 15 毫秒
141.
142.
E. S. Naumova G. I. Naumov T. N. Nikitina A. Zh. Sadykova V. I. Kondratieva 《Microbiology》2012,81(2):216-223
Molecular genetic identification of 52 Kluyveromyces strains from VKM, mainly of dairy origin, was carried out. Restriction analysis of 5.8S-ITS rDNA fragments was used to differentiate
between Kl. lactis var. lactis, Kl. lactis var. drosophilarum (European population of “krassilnikovii”), and Kl. marxianus. Kl. lactis was shown to differ from Kl. marxianus in its ability to assimilate α-glucosides: maltose, melezitose, and α-methyl-glucoside. 相似文献
143.
ANTHONY RAVEL LAURENT MARIVAUX RODOLPHE TABUCE MUSTAPHA BEN HAJ ALI EL MABROUK ESSID MONIQUE VIANEY‐LIAUD 《Palaeontology》2012,55(5):1035-1041
Abstract: Among the new dental remains from the late Early Eocene of Chambi (Kasserine area, Tunisia) is a large‐sized upper molar of a new bat species, Witwatia sigei nov. sp. (Chiroptera, Vespertilionoidea, Philisidae), described herein. The locality of Chambi has revealed evidence for an early appearance of two modern microchiropteran superfamilies in Africa: Dizzya exsultans, a Philisidae, which is considered to be an archaic Vespertilionoidea, and an indeterminate Rhinolophoidea. In addition to D. exsultans, the new species, W. sigei, is the second representative of the Philisidae in this locality. W. sigei extends back to the late Early Eocene the occurrence of the genus Witwatia, which was previously only reported from the early Late Eocene of the Fayum (BQ‐2, Egypt). By analogy with the largest extant microbats, the large size of Witwatia suggests a tendency to the opportunistic diet of this taxon, thereby contrasting with the strict insectivory characterizing primitive bats found in other continents in the same epoch. 相似文献
144.
This study assesses the efficacy of a fixed dose of Ropren(?) (a plant preparation isolated from the neutral fraction of an extract of spruce needles) on cognitive impairment in rats with β-amyloid peptide-(25-35)-induced amnesia. Ropren(?) was administered at a dose of 8.6mg/kg for 28 days, per os, to rats with β-amyloid peptide-(25-35)-induced amnesia. Cognitive performance was assessed using the passive avoidance paradigm and the Morris water maze and behavior was assessed using the open field test. After four weeks, Ropren(?) treatment significantly improved non-spatial and spatial learning in rats with β-amyloid peptide-(25-35)-induced amnesia. The results of the present study suggest that Ropren(?), a novel plant preparation, ameliorates cognitive deficiencies in an animal model relevant to Alzheimer's disease. 相似文献
145.
M. B. Yakovleva T. L. Khoang Z. K. Nikitina 《Applied Biochemistry and Microbiology》2006,42(4):431-434
The ability of deuteromycetes of the genera Penicillium, Aspergillus, and Botrytis to retain collagenolytic activity was studied after both 2 and 10 years of storage on a Czapek medium under a layer of mineral oil at 4°C, as well as in silica gel granules at 20 and ?60°C. The enzymatic activity of several species, including Botrytis terrestris, Penicillium janthinellum, Penicillium chrysogenum, and Penicillium citrinum, was retained under both conditions of storage. Aspergillus repens retained enzymatic activity only if stored under a layer of mineral oil. The viability of conidia and the collagenolytic activity of Botrytis terrestris, P. janthinellum, P. chrysogenum, and Penicillium citrinum, maintained on silica gel for 10 years, depended on the storage temperature. The viability of the test strains improved after storage on a silica gel at ?60°C. A strain of Aspergillus repens lost its ability to dissolve collagen at various storage tempeatures on the silica gel. The index of lysis for three strains of Penicillium deuteromycetes (Penicillium janthinellum, Penicillium chrysogenum, and Penicillium citrinum) increased after a 10-year storage on silica gel at ?60°C. 相似文献
146.
Macdonald RL Zhang ZD Takahashi M Nikitina E Young J Xie A Larkin L 《American journal of physiology. Heart and circulatory physiology》2006,290(6):H2329-H2336
Arteries that develop vasospasm after subarachnoid hemorrhage (SAH) may have altered contractility and compliance. Whether these changes are due to alterations in the smooth muscle cells or the arterial wall extracellular matrix is unknown. This study elucidated the location of such changes and determined the calcium sensitivity of vasospastic arteries. Dogs were placed under general anesthesia and underwent creation of SAH using the double-hemorrhage model. Vasospasm was assessed by angiography performed before and 4, 7, or 21 days after SAH. Basilar arteries were excised from SAH or control dogs (n = 8-52 arterial rings from 2-9 dogs per measurement) and studied under isometric tension in vitro before and after permeabilization of smooth muscle with alpha-toxin. Endothelium was removed from all arteries. Vasospastic arteries demonstrated significantly reduced contractility to KCl with a shift in the EC(50) toward reduced sensitivity to KCl 4 and 7 days after SAH (P < 0.05, ANOVA). There was reduced compliance that persisted after permeabilization (P < 0.05, ANOVA). Calcium sensitivity was decreased during vasospasm 4 and 7 days after SAH, as assessed in permeabilized arteries and in those contracted with BAY K 8644 in the presence of different concentrations of extracellular calcium (P < 0.05, ANOVA). Depolymerization of actin with cytochalasin D abolished contractions to KCl but failed to alter arterial compliance. In conclusion, it is shown for the first time that calcium sensitivity is decreased during vasospasm after SAH in dogs, suggesting that other mechanisms are involved in maintaining the contraction. Reduced compliance seems to be due to an alteration in the arterial wall extracellullar matrix rather than the smooth muscle cells themselves because it cannot be alleviated by depolymerization of smooth muscle actin. 相似文献
147.
Peter Guterstam Fatemeh Madani Hisaaki Hirose Toshihide Takeuchi Shiroh Futaki Samir EL Andaloussi Astrid Gräslund Ülo Langel 《生物化学与生物物理学报:生物膜》2009,1788(12):2509-2517
Cell-penetrating peptides (CPPs) are membrane permeable vectors recognized for their intrinsic ability to gain access to the cell interior. The hydrophobic counter-anion, pyrenebutyrate, enhances cellular uptake of oligoarginine CPPs. To elucidate CPP uptake mechanisms, the effect of pyrenebutyrate on well-recognized CPPs with varying hydrophobicity and arginine content is investigated. The cellular CPP uptake and CPP-mediated oligonucleotide delivery is analyzed by fluorescence activated cell sorting, confocal microscopy, and a cell-based splice-switching assay. The splice-switching oligonucleotide is a mixmer of 2′-O-methyl RNA and locked nucleic acids delivered as a non-covalent complex with 10-fold molar CPP excess. CPP-induced membrane perturbation on large unilamellar vesicles is investigated in calcein release experiments. We observed that pyrenebutyrate facilitates cellular uptake and translocation of oligonucleotide mediated by oligoarginine nonamer while limited effect of pyrenebutyrate on more hydrophobic CPPs was observed. By combining the different experimental results we conclude that the pathway for cellular uptake of oligoarginine is dominated by direct membrane translocation, whereas the pathway for oligoarginine-mediated oligonucleotide translocation is dominated by endocytosis. Both mechanisms are promoted by pyrenebutyrate and we suggest that pyrenebutyrate has different sites of action for the two uptake and translocation mechanisms. 相似文献
148.
The lamprey is the only basal vertebrate in which large-scale gene perturbation analyses are feasible at present. Studies on this unique animal model promise to contribute both to the understanding of the basic neural-crest gene regulatory network architecture, and evolution of the neural crest. In this review, we summarize the currently known regulatory relationships underlying formation of the vertebrate neural crest, and discuss new ways of addressing the many remaining questions using lamprey as an experimental model. 相似文献
149.
N. M. Timofeeva V. V. Egorova A. A. Nikitina Yu. V. Dmitrieva 《Journal of Evolutionary Biochemistry and Physiology》2009,45(3):356-364
Activities of digestive enzymes (maltase, alkaline phosphatase, aminopeptidase M, and glycyl-L-leucine dipeptidase) in small and large intestine, liver, and kidney were studied in rats of different ages kept at the period of lactation under conditions of the standard (8 individuals per litter) and low (3 individuals) number of pups per litter. The low-protein diet for 10 days at once after weaning was found to change the mass of organs and their digestive enzyme activities in all studied rat groups. The revealed changes were more prominent in rats kept under conditions of excessive breast feeding. In adult animals of this group, distribution of the alkaline phosphatase activity along the small intestine differed from that in control rats. The obtained results seem to confirm that any disturbance of the nutrition quality in early ontogenesis leads to disturbance of the «metabolic programming of enzyme systems» of digestive organs. 相似文献
150.
D. Jabborova R.Z. Sayyed A. Azimov Z. Jabbarov A. Matchanov Y. Enakiev Alaa Baazeem Ayman EL Sabagh Subhan Danish Rahul Datta 《Saudi Journal of Biological Sciences》2021,28(9):5268-5274
Ginger is used as one of the important ingredients in traditional as well as modern medicine besides as a spice. It boosts immunity and is a rich source of many biologically active substances and minerals. Although it is a medicinally important crop, its productivity is, however, affected due to poor nutrient management and therefore it requires an adequate supply of nutrients in the form of inorganic fertilizers or organic manuring, or a mixture of both. In this context, the present study was aimed to investigate the effect of mineral fertilizers on the content of mineral elements in the ginger rhizome, on soil enzyme activity, and soil properties. Lysimeter experiments were conducted at the Institute of Genetics and Plant Experimental Biology, Kibray, Tashkent region, Uzbekistan. The experiment comprised of four treatments T1 – Control, T2 - N75P50K50 kg/ha, T3 - and T4 - N100P75K75 + B3Zn6Fe6 kg/ha. The results showed that the application of N125P100K100 kg/ha increased rhizome K content by 49%, P content by 20%, and Na content by 58% as compared to control without fertilizer. While the application of N100P75K75 + B3Zn6Fe6 kg/ha showed a significant enhancement in rhizome K, Ca, P, Mg, Na, Fe, Mn, Zn, Cu, Cr, Mo, and Si contents over the control. This treatment also improved active P content by 29%, total P content by 80%, total K content 16%, and N content by 33% content, and the activities of urease, invertase, and catalase activities as compared to control of without mineral fertilizer and control respectively. Thus the application of NPK + BZnFe at the rate of 100:75:75:3:6:6 kg/ha helps in improving macroelements and microelements in the ginger rhizome and activities of soil enzymes that helps in mineral nutrition of the rhizome. 相似文献