全文获取类型
收费全文 | 9952篇 |
免费 | 802篇 |
国内免费 | 12篇 |
专业分类
10766篇 |
出版年
2023年 | 35篇 |
2022年 | 99篇 |
2021年 | 174篇 |
2020年 | 130篇 |
2019年 | 177篇 |
2018年 | 242篇 |
2017年 | 236篇 |
2016年 | 367篇 |
2015年 | 492篇 |
2014年 | 610篇 |
2013年 | 674篇 |
2012年 | 839篇 |
2011年 | 771篇 |
2010年 | 490篇 |
2009年 | 448篇 |
2008年 | 646篇 |
2007年 | 552篇 |
2006年 | 480篇 |
2005年 | 429篇 |
2004年 | 434篇 |
2003年 | 405篇 |
2002年 | 325篇 |
2001年 | 209篇 |
2000年 | 193篇 |
1999年 | 162篇 |
1998年 | 84篇 |
1997年 | 67篇 |
1996年 | 72篇 |
1995年 | 62篇 |
1994年 | 53篇 |
1993年 | 45篇 |
1992年 | 99篇 |
1991年 | 81篇 |
1990年 | 65篇 |
1989年 | 53篇 |
1988年 | 36篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1979年 | 20篇 |
1978年 | 20篇 |
1976年 | 17篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1973年 | 20篇 |
1972年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Wilfried W. de Jong Louis H. Cohen Jack A.M. Leunissen Anneke Zweers 《Biochemical and biophysical research communications》1980,96(2):648-655
αAIns, an elongated α-crystallin A chain previously observed in rat, was present beside the normal αA chain in mouse, gerbil and hamster, which places its origin at least 30 million years ago. Like in rat the sequences of golden hamster αAIns and αA were found to be identical, apart from the internal insertion of 22 residues in αAIns. The hamster chains only differed from the rat chains by a single substitution in the inserted sequence of αAIns. The origin of αAIns, by insertion of 22 residues in an otherwise unchanged αA chain, and its rigid evolutionary conservation are most easily explained by assuming the incomplete removal of a putative intervening sequence from the precursor mRNA of αA, leaving an intracistronic insert of 66 nucleotides in part of the eventually translated mRNA. 相似文献
62.
More than 300 reference strains representing 60 species and varieties ofFusarium cultures named according to different taxonomic systems are currently maintained at the American Type Culture Collection (ATCC). They have been preserved by freeze-drying and by freezing and subsequent storage in liquid nitrogen (–196°C) to insure their viability without contamination, variation, mutation, or deterioration. The materials and procedures used at the ATCC for the acquisition, accessioning, cataloguing, preservation and distribution are described. Longevity storage data for the strains available for distribution are presented and discussed. 相似文献
63.
Treatment of rats with thiamphenicol in a dose of 125 mg/kg per day for 60–64 h causes specific inhibition of mitochondrial protein synthesis, leading to a drastic decrease of the cytochrome c oxidase activity in intestinal epithelium. At the same time the mitochondrial ATPase activity becomes resistant to inhibition by oligomycin. Experiments with isolated intestinal mitochondria revealed that respiration in state 3 is diminished by 55% with succinate (5 mM) and by 40% with pyruvate (10 mM) plus L-malate (2 mM) as the substrates, both as compared to intestinal mitochondria isolated from control rats. P : O ratios as well as respiratory control indices are comparable in the two groups of animals. Uncoupled respiration is inhibited by 35% with succinate as the substrate, while the succinate cytochrome c reductase activity remains unaltered. No inhibition of uncoupled respiration with pyruvate plus L-malate as the substrates was observed. The ATP-Pi exchange activity in the mitochondria from the treated animals is diminished by about 75%. It is concluded that in the mitochondria of the treated animals the inhibition of the coupled respiration (state 3) is caused by the limitation of the ATP-generating capacity and that electron transport is rate limiting only with the rapidly oxidized substrates such as succinate, if respiration is uncoupled. 相似文献
64.
65.
Non-ideal miscibility in the liquid phase of mono- or diglycerides with triglycerides has been described in terms of thermodynamic excess functions. To this end the heat of mixing and the solubility temperatures of several ideal and non-ideal binary glyceride mixtures have been measured. The non-ideal phase behaviour of glyceride systems reported in the literature has been satisfactorily predicted, which indicates that the excess functions are generally applicable to mixtures of mono- or diglycerides with triglycerides. 相似文献
66.
Evaluation of Bottlenecks in the Late Stages of Protein Secretion in Bacillus subtilis 总被引:3,自引:0,他引:3 下载免费PDF全文
Albert Bolhuis Harold Tjalsma Hilde E. Smith Anne de Jong Rob Meima Gerard Venema Sierd Bron Jan Maarten van Dijl 《Applied microbiology》1999,65(7):2934-2941
Despite a high capacity for secretion of homologous proteins, the secretion of heterologous proteins by Bacillus subtilis is frequently inefficient. In the present studies, we have investigated and compared bottlenecks in the secretion of four heterologous proteins: Bacillus lichenifomis α-amylase (AmyL), Escherichia coli TEM β-lactamase (Bla), human pancreatic α-amylase (HPA), and a lysozyme-specific single-chain antibody. The same expression and secretion signals were used for all four of these proteins. Notably, all identified bottlenecks relate to late stages in secretion, following translocation of the preproteins across the cytoplasmic membrane. These bottlenecks include processing by signal peptidase, passage through the cell wall, and degradation in the wall and growth medium. Strikingly, all translocated HPA was misfolded, its stability depending on the formation of disulfide bonds. This suggests that the disulfide bond oxidoreductases of B. subtilis cannot form the disulfide bonds in HPA correctly. As the secretion bottlenecks differed for each heterologous protein tested, it is anticipated that the efficient secretion of particular groups of heterologous proteins with the same secretion bottlenecks will require the engineering of specifically optimized host strains. 相似文献
67.
Riboprinting was used to determine the relationships among strains belonging to 15 species of the genusKluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of theKluyveromyces strains included in this study.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
68.
Manganese Regulation of Veratryl Alcohol in White Rot Fungi and Its Indirect Effect on Lignin Peroxidase 总被引:6,自引:3,他引:6 下载免费PDF全文
Many white rot fungi are able to produce de novo veratryl alcohol, which is known to be a cofactor involved in the degradation of lignin, lignin model compounds, and xenobiotic pollutants by lignin peroxidase (LiP). In this study, Mn nutrition was shown to strongly influence the endogenous veratryl alcohol levels in the culture fluids of N-deregulated and N-regulated white rot fungi Bjerkandera sp. strain BOS55 and Phanerochaete chrysosporium BKM-F-1767, respectively. Endogenous veratryl alcohol levels as high as 0.75 mM in Bjerkandera sp. strain BOS55 and 2.5 mM in P. chrysosporium were observed under Mn-deficient conditions. In contrast, veratryl alcohol production was dramatically decreased in cultures supplemented with 33 or 264 (mu)M Mn. The LiP titers, which were highest in Mn-deficient media, were shown to parallel the endogenous veratryl alcohol levels, indicating that these two parameters are related. When exogenous veratryl alcohol was added to Mn-sufficient media, high LiP titers were obtained. Consequently, we concluded that Mn does not regulate LiP expression directly. Instead, LiP titers are enhanced by the increased production of veratryl alcohol. The well-known role of veratryl alcohol in protecting LiP from inactivation by physiological levels of H(inf2)O(inf2) is postulated to be the major reason why LiP is apparently regulated by Mn. Provided that Mn was absent, LiP titers in Bjerkandera sp. strain BOS55 increased with enhanced fungal growth obtained by increasing the nutrient N concentration while veratryl alcohol levels were similar in both N-limited and N-sufficient conditions. 相似文献
69.
So Eun Park Jong Cheol Kim Se Jin Lee Mi Rong Lee Sihyeon Kim Dongwei Li Sehyeon Baek Ji Hee Han Jeong Jun Kim Kyung Bon Koo Tae Young Shin Jae Su Kim 《Journal of Asia》2018,21(4):1102-1109
Entomopathogenic fungi have great potential to control agricultural and horticultural insect pests, however optimizing conidial production systems to demonstrate high productivity and stability still needs additional efforts for successful field application and industrialization. Although many virulent entomopathogenic fungal isolates have been viewed as potential candidates in a laboratory environment, very few of the isolates are being used in practice for application in agricultural fields as commercial products. I. javanicus is an entomopathogenic fungus that is parasitic to various diverse coleopteran and lepidopteran insects and thought good candidate as biopesticdes. In this work, the basic characteristics of two entomopathogenic fungi, I. javanica FG340 and Pf04, were investigated in morphological examinations, genetic identification, and virulence against Thrips palmi, and then the feasibility of various grains substrates for conidial production was assessed, particularly focusing on conidial productivity and thermotolerance. Isaria javanica FG340 and Pf04 conidia were solid-cultured on 12 grains for 14?days in a Petri dish. Of the tested Italian millet, perilla seed, millet and barley-based cultures showed high conidial production. The four-grain media yielded >1?×?109 conidia/g of I. javanica FG340 and Pf04. Pf04 strain had enhanced thermotolerance up to 45?°C when cultured on Italian millet. In application, it was easy to make a conidial suspension using the cultured grains, and several surfactants were tested to release the conidia. This work suggests several possible inexpensive grain substrates by which to promote conidial production combined with enhanced stability against exposure to high temperature. 相似文献
70.
Anne-Claire van Altvorst Herma Koehorst Jan de Jong Hans J. M. Dons 《Plant Cell, Tissue and Organ Culture》1996,45(2):169-173
Transgenic carnation plants were obtained after infection of petal explants with the supervirulent Agrobacterium tumefaciens strain AGLO. Southern blot techniques confirmed the transgenic nature of four transformed plants. The expression of the gus gene was verified in these plants by histochemical assays on selected shoots. It was very difficult to transfer the transgenic plants to the greenhouse due to vitrification and premature flowering.Abbreviations BA
6-benzyladenine
- GA3
gibberellic acid
-
gus-
glucuronidase gene
- MS
Murashige and Skoog (1962)
- NAA
naphthaleneacetic acid
-
nptII
neomycin phosphotransferase II gene
- PCR
polymerase chain reaction 相似文献