全文获取类型
收费全文 | 5588篇 |
免费 | 364篇 |
专业分类
5952篇 |
出版年
2023年 | 37篇 |
2022年 | 83篇 |
2021年 | 149篇 |
2020年 | 93篇 |
2019年 | 105篇 |
2018年 | 150篇 |
2017年 | 135篇 |
2016年 | 205篇 |
2015年 | 278篇 |
2014年 | 322篇 |
2013年 | 407篇 |
2012年 | 471篇 |
2011年 | 453篇 |
2010年 | 274篇 |
2009年 | 250篇 |
2008年 | 338篇 |
2007年 | 322篇 |
2006年 | 284篇 |
2005年 | 258篇 |
2004年 | 232篇 |
2003年 | 212篇 |
2002年 | 207篇 |
2001年 | 55篇 |
2000年 | 59篇 |
1999年 | 69篇 |
1998年 | 38篇 |
1997年 | 49篇 |
1996年 | 43篇 |
1995年 | 28篇 |
1994年 | 36篇 |
1993年 | 30篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 11篇 |
1946年 | 5篇 |
排序方式: 共有5952条查询结果,搜索用时 0 毫秒
1.
Lucia Di Giambattista P. Grimaldi S. Gaudenzi D. Pozzi M. Grandi S. Morrone I. Silvestri A. Congiu Castellano 《European biophysics journal : EBJ》2010,39(6):929-934
We have made a preliminary analysis of the results about the effects on tumoral cell line (lymphoid T cell line Jurkat) induced
by UVB radiation (dose of 310 mJ/cm2) with and without a vegetable mixture. In the present study, we have used two techniques: Fourier transform infrared spectroscopy
(FTIR) and flow cytometry. FTIR spectroscopy has the potential to provide the identification of the vibrational modes of some
of the major compounds (lipid, proteins and nucleic acids) without being invasive in the biomaterials. The second technique
has allowed us to perform measurements of cytotoxicity and to assess the percentage of apoptosis. We already studied the induction
of apoptotic process in the same cell line by UVB radiation; in particular, we looked for correspondences and correlations
between FTIR spetroscopy and flow cytometry data finding three highly probable spectroscopic markers of apoptosis (Pozzi et
al. in Radiat Res 168:698–705, 2007). In the present work, the results have shown significant changes in the absorbance and
spectral pattern in the wavenumber protein and nucleic acids regions after the treatments. 相似文献
2.
Vikas Yadav Patade Sujata Bhargava Penna Suprasanna 《Plant Cell, Tissue and Organ Culture》2012,108(2):279-286
In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic
pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt
stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in
callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS
and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage
was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while
catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences
in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance
response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level. 相似文献
3.
Francesca Passaretta Domenico Bosco Lucia Centurione Maria Antonietta Centurione Fabio Marongiu Roberta Di Pietro 《Journal of cellular and molecular medicine》2020,24(7):4350-4355
Human Amniotic Epithelial Cells (hAEC) isolated from term placenta are a promising source for regenerative medicine. However, it has long been debated whether the hAEC population consists of heterogeneous or homogeneous cells. In a previous study, we investigated the characteristics of hAEC isolated from four different regions of the amniotic membrane finding significant heterogeneity. The aim of this study was to evaluate the hepatic differentiation capability of hAEC isolated from these four regions. Human term placentae were collected after caesarean section and hAEC were isolated from four regions of the amniotic membrane (R1-R4, according to their relative distance from the umbilical cord) and treated in hepatic differentiation conditions for 14 days. hAEC-derived hepatocyte-like cells showed marked differences in the expression of hepatic markers: R4 showed higher levels of Albumin and Hepatocyte Nuclear Factor (HNF) 4α whereas R1 expressed higher Cytochrome P450 enzymes, both at the gene and protein level. These preliminary results suggest that hAEC isolated from R1 and R4 of the amniotic membrane are more prone to hepatic differentiation. Therefore, the use of hAEC from a specific region of the amniotic membrane should be taken into consideration as it could have an impact on the outcome of therapeutic applications. 相似文献
4.
The assembly of a large physical map of genomes requires simultaneous analysis of many cosmid clones for overlapping regions. The search for overlapping regions may be achieved by various means. High-performance liquid chromatography (HPLC) provides an alternative to gel electrophoresis since microgram amounts of each DNA fragment may be collected into individual test tubes for further analysis. HPLC has been used to identify overlapping cosmid clones from a pool of cosmid DNA containing the terminal portion of the long arm of the human X chromosome (Xq24-qter). Among 400 cosmids analyzed, 3 were shown to overlap. 相似文献
5.
Lusinete Aciole De Queiroz 《Mycopathologia》1973,51(4):307-314
A new species of the genusEndomycopsis is proposed. It was isolated from waste water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.
Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Química de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfecciobamiento en el estudio de las levaduras. 相似文献
Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Química de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfecciobamiento en el estudio de las levaduras. 相似文献
6.
Cassandre Leverrier Giana Almeida Lucia Espinosa-Mu noz Gérard Cuvelier 《Food biophysics》2016,11(3):235-247
This work investigates the impact of structural parameters on the rheological behaviour of apple purees. Reconstructed apple purees from 0 g/100 g up to 2.32 g/100 g of insoluble solids content and varying in particle size were prepared. Three different particle size distributions were obtained by mechanical treatment only, to modify both size and morphology of the particles without modifying the intrinsic rigidity of the cell walls. Rheological measurements showed that the insoluble solids content have a first order effect on the rheological behaviour of the suspensions: three concentrations domains were observed in both dynamic and flow measurements. A model is proposed for each domain. The existence of a weak network between particles is clearly shown over a critical concentration of insoluble solids (cell walls) depending on particle size distribution (semi-diluted domain). In a concentrated domain, particles are on close packing conditions and their apparent volume begin to shrink. Particle size and shape also play an important role on the rheological behaviour of reconstructed apple puree. Due to their irregular shape, cell clusters clog the medium at lower concentration compared to individual cells. 相似文献
7.
I Martínez de Mara?ón N Chaudanson N Joly P Gervais 《Biotechnology and bioengineering》1999,65(2):176-181
Thermal resistance of Saccharomyces cerevisiae was found to be drastically dependent on the kinetics of heat perturbation. Yeasts were found to be more resistant to a plateau of 1 h at 50 degrees C after a slope of temperature increase (slow and linear temperature increments) than after a shock (sudden temperature change). Thermotolerance was mainly acquired between 40-50 degrees C during a heat slope, i.e., above the maximal temperature of growth. The death of the yeasts subjected to a heat shock might be related to the loss of membrane integrity: intracellular contents extrusion, i.e., membrane permeabilization, was found to precede cell death. However, the permeabilization did not precede cell death during a heat slope and, therefore, membrane permeabilization was a consequence rather than a cause of cell death. During a slow temperature increase, yeasts which remain viable may have time to adapt their plasma membrane and thus maintain membrane integrity. 相似文献
8.
A note on a modified membrane-Bovis agar for the enumeration of Streptococcus bovis by membrane filtration 总被引:1,自引:0,他引:1
The effect of dilution and temperature on the antibacterial properties of potassium sorbate was determined. The time taken to kill a standard inoculum of Escherichia coli was increased considerably after either dilution of the preservative or lowering of the temperature. The value for the concentration exponent, eta, was approximately 3 and that for the temperature coefficient, Q10, was 2.3. 相似文献
9.
10.