全文获取类型
收费全文 | 851篇 |
免费 | 59篇 |
国内免费 | 1篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 44篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 34篇 |
2017年 | 42篇 |
2016年 | 56篇 |
2015年 | 53篇 |
2014年 | 54篇 |
2013年 | 80篇 |
2012年 | 84篇 |
2011年 | 70篇 |
2010年 | 39篇 |
2009年 | 36篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1973年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有911条查询结果,搜索用时 187 毫秒
1.
Replacement of ~100 mM of sodium chloride in the extracellular medium of quiescent hamster fibroblasts (Nil 8 and BHK cells) by potassium chloride causes an increase in the rate of uridine uptake. This increase is identical with that achieved by addition of 10% serum to the same cultures. The effects of serum and KCl are not additive. The dependence of the rate of uridine uptake on extracellular KCl concentration is of a sigmoid nature. The time course of the activation process is similar to that of serum activation of uridine uptake in the same cells. The high rate of uridine uptake persists for at least 30 min after return to an extracellular medium containing a high concentration of sodium. 相似文献
2.
3.
Zafar Iqbal Khan Kafeel Ahmad Muhammad Ashraf Rukhsana Parveen Zahara Bibi Irfan Mustafa 《人类与生态风险评估》2016,22(1):86-98
The present research was conducted in district Jhang, Pakistan, to evaluate the concentration of metals/metalloids in soil and pumpkin (Cucurbita maxima) irrigated with domestic wastewater. Data revealed that the levels of metals and metalloids in soil samples from two different sites were below the safe limits except Cd, whereas, in the vegetable, the concentrations of As, Se, Ni, Mo, Pb, Mn, and Cu were above the safe limits. The levels of 12 metals and metalloids in the soil were ranged between 0.14 to 22.76 mg/kg at site-I and 0.16 to 22.13 mg/kg at site-II. The levels of these metals in the vegetable were found 0.35 to 61.13 mg/kg at site-I and 0.31 to 53.63 mg/kg at site-II. The transfer factor at both sites was highest for As and Co. The pollution load index recorded for Se, Cu, Cd, Mo, Pb, and Co was greater than 1. The daily intake of As, Mn, and Mo was above the oral reference dose, which reflects that the intake of pumpkin is not safe for the inhabitants of the selected sites. The control measures should be taken to phytoextract heavy metals and metalloids from polluted sites so as to reduce the health risks. 相似文献
4.
Ravigadevi Sambanthamurthi Siti Hasnah Parman Mohd. Roslan Md. Noor 《Plant Cell, Tissue and Organ Culture》1996,46(1):35-41
Procedures are deseribed for the efficient isolation of protoplasts from a variety of oil palm (Elaeis guineensis Jacq.) tissues. Various factors including donor source, composition of enzyme mixture and culture medium affected the yield and viability of the protoplasts Polyembryogenic cultures of oil palm were the most suitable starting material in terms of yield, viability and metabolic competence. Pectolyase Y-23 in association with cellulase and hemicellulase was required for the efficient release of protoplasts from the oil palm tissues. Limited cell division to form microcallus was observed at very low frequency (<0.01%) when glutathione and catalase were incorporated in the culture medium.Abbreviations 2,4-d
dichlorophenoxyacetic acid
- DTT
dithiothreitol
- MES
2[N-morpholino] ethanesulphonic acid
- NAA
1-naphthalene acetic acid
- PVP
polyvinylpyrrolidone 相似文献
5.
Summary The occurrence of cells resembling mammalian Langerhans cells in the avian epidermis was studied by ATPase histochemistry, Ia immunoreactivity and electron microscopy. The existence of MHC class II antigen-(Ia) expressing, ATPase-positive dendritic cells, which are ultrastructurally similar to mammalian Langerhans cells except for the absence of Birbeck granules, was demonstrated. These cells may be a basic component of the immune system of birds. 相似文献
6.
Martine de Boer Maaike te Lintel Hekkert Jiang Chang Bibi S. van Thiel Leonie Martens Maxime M. Bos Marion G. J. de Kleijnen Yanto Ridwan Yanti Octavia Elza D. van Deel Lau A. Blonden Renata M. C. Brandt Sander Barnhoorn Paula K. Bautista-Niño Ilona Krabbendam-Peters Rianne Wolswinkel Banafsheh Arshi Mohsen Ghanbari Christian Kupatt Leon J. de Windt A. H. Jan Danser Ingrid van der Pluijm Carol Ann Remme Monika Stoll Joris Pothof Anton J. M. Roks Maryam Kavousi Jeroen Essers Jolanda van der Velden Jan H. J. Hoeijmakers Dirk J. Duncker 《Aging cell》2023,22(3):e13768
7.
M Anissimova L Yaouancq F Noor M-A Badet-Denisot B Badet 《The journal of peptide research》2003,62(2):88-95
A direct continuous UV-Vis spectrophotometric assay has been developed for VanX, a D-alanyl-D-alanine aminodipeptidase necessary for vancomycin resistance. This method is based on the hydrolysis of the alternative substrate D-alanyl-alpha-(R)-phenylthio-glycine D-Ala-D-Gly(S-Ph)-OH (H-DAla-DPsg-OH, 5a). Spontaneous decomposition of the released phenylthioglycine generates thiophenol, which is quantified using Ellman's reagent. The dipeptide behaved as an excellent substrate of VanX, exhibiting Michaelis-Menten kinetics with a kcat of 76 +/- 5/s and a KM of 0.83 +/- 0.08 mm (kcat = 46 +/- 3/s and KM = 0.11 +/- 0.01 mm for D-Ala-D-Ala). Determination of the kinetic parameters of the previously reported mechanism-based inhibitor D-Ala-D-Gly(SPhip-CHF2)-OH (H-D-Ala-DPfg-OH, 5c) [Araoz, R., Anhalt, E., René, L., Badet-Denisot, M.-A., Courvalin, P. & Badet, B. (2000) Biochemistry 39, 15971-15979] using the substrate reported in the present study yielded values of Kirr of 22 +/- 1 microM and kinact of 9.3 +/- 0.4/min in good agreement with values previously obtained in our laboratory (Kirr = 30 +/- 1 mm; kinact = 7.3 +/- 0.3/min). In addition, inhibition by the competing substrate D-Ala-D-Ala resulted in determination of a Ki = 70 +/- 6 microM close to the previously reported KM value. These results demonstrate that the present assay is a convenient, rapid and sensitive tool in the search for VanX inhibitors. 相似文献
8.
In model experiments with Bonus barley,where the growth of a fraction of the seedlings is retarded by a raised thiol content, obtained through treatment with 2-mercaptoethanol, stimulation of growth is reproducibly induced by low doses of γ-rays. As illustrated by a probit representation of seedling heights, and by the decrease of coefficients of variation, the radiostimulation is restricted to that fraction of seedlings which exhibits a suppressd growth. The validity of the model to natural situations was sustained in studies of the variety Impala, which was shown by Fendrik and Bors to respond regularly to stimulating doses of X-rays. In this variety the response was shown to be restricted to a sub-population of seedlings with retarded growth, i.e. the same pattern as observed in thiol-treated Bonus barley. 相似文献
9.
On a new charophyte from India 总被引:1,自引:1,他引:0
Chara indica is described as a new species on morphological and cytological grounds.Part of Ph. D. Thesis of Ranchi University. 相似文献
10.
Daniele Novarina Georges E. Janssens Koen Bokern Tim Schut Noor C. van Oerle Hinke G. Kazemier Liesbeth M. Veenhoff Michael Chang 《Aging cell》2020,19(2)
To ensure proper transmission of genetic information, cells need to preserve and faithfully replicate their genome, and failure to do so leads to genome instability, a hallmark of both cancer and aging. Defects in genes involved in guarding genome stability cause several human progeroid syndromes, and an age‐dependent accumulation of mutations has been observed in different organisms, from yeast to mammals. However, it is unclear whether the spontaneous mutation rate changes during aging and whether specific pathways are important for genome maintenance in old cells. We developed a high‐throughput replica‐pinning approach to screen for genes important to suppress the accumulation of spontaneous mutations during yeast replicative aging. We found 13 known mutation suppression genes, and 31 genes that had no previous link to spontaneous mutagenesis, and all acted independently of age. Importantly, we identified PEX19, encoding an evolutionarily conserved peroxisome biogenesis factor, as an age‐specific mutation suppression gene. While wild‐type and pex19Δ young cells have similar spontaneous mutation rates, aged cells lacking PEX19 display an elevated mutation rate. This finding suggests that functional peroxisomes may be important to preserve genome integrity specifically in old cells. 相似文献