全文获取类型
收费全文 | 1015篇 |
免费 | 81篇 |
专业分类
1096篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 32篇 |
2015年 | 55篇 |
2014年 | 52篇 |
2013年 | 84篇 |
2012年 | 69篇 |
2011年 | 90篇 |
2010年 | 48篇 |
2009年 | 36篇 |
2008年 | 68篇 |
2007年 | 60篇 |
2006年 | 51篇 |
2005年 | 52篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 39篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1096条查询结果,搜索用时 15 毫秒
1.
Twenty-eight strains of pectolytic clostridia were isolated from sugar beet pulp silages. Seventeen non-pigmented strains were presumed to be Clostridium acetobutylicum ; the remaining 11 pigmented strains were similar to Cl. felsineum. The addition of molasses to sugar beet pulps favoured the growth of other bacteria, particularly lactic acid organisms, whereas pectolytic clostridia were only occasionally found. The pectolytic clostridia promoted the structure loss of simulated silages. The use of molasses in sugar beet pulp ensiling was suggested to prevent texture loss of the ensiled mass. 相似文献
2.
D Russo R Fanin E Zuffa C Gallizia M Grazia Michieli D Damiani N Testoni V Pecile G Visani R Colombini 《Blut》1989,59(1):15-20
The clinical, hematologic and cytogenetic effects of human recombinant gamma interferon (IFN) were investigated in 14 patients with Ph+ chronic myeloid leukemia (CML). Gamma-IFN was given at a daily dosage of 0.50 mg (= 10 x 10(6) U)/m2 from the 3rd week of treatment on, but the dosage had to be reduced to 0.25 mg/m2 in 10 cases and to 0.35 mg/m2 in 2 cases, because of the severity and persistence of side effects (mainly fever, fatigue, headache and pain). Only 2 patients tolerated the full dosage. The overall response rate was 64% (1 complete and 8 partial hematologic responses). Only patients in stable chronic phase responded. Two out of two patients in unstable chronic phase and two out of two patients in accelerated phase failed to respond. Eight out of nine responding patients remained in remission throughout the duration of treatment (30 to 35 weeks). No karyotypic conversion was detected. These data show that gamma IFN alone is effective in Ph+ CML, but that side effects can limit substantially the dosage and duration of treatment. 相似文献
3.
Summary The caudal musculature of the free-swimming tadpole of the ascidian, B. schlosseri consists of cylindrical mononucleated cells connected in longitudinal rows flanking the axial notochord. During resorption of the larval tail, which is apparently induced by the contraction of the epidermis, muscle cells are dissociated and pushed into the body cavity where most of them are rapidly engulfed by phagocytes. In the initial stages of tail withdrawal muscle cells display surface alterations due to the disruption of intercellular junctions and disarrangement of myofibrils. Extensive degenerative changes, with shrinkage of mitochondria and disintegration of the contractile material are subsequently observed. Lysosomes and autophagic vacuoles are rarely seen and appear to play a secondary role in the degradation of the muscle cells, which occurs predominantly within the phagocytes. Myofilaments and myofibrils have never been observed within autophagic vacuoles. Clumps of muscle fragments and degenerated phagocytes undergo eventual dissolution in the blood lacunae, concomitantly with the differentiation of the young oozooid.This investigation was supported in part by a grant from the Muscular Dystrophy Associations of America and by CNR contract No. 7100396/04115542 from the Istituto di Biologia del Mare, Venice. We gratefully acknowledge the skillful assistance of Mr. G. Gallian, Mr. M. Fabbri and Mr. G. Tognon. We also thank the staff of the Stazione Idrobiologica at Chioggia for collecting the colonies. 相似文献
4.
Summary Two plasmids isolated from Lactobacillus helveticus strain ILC 54 were analysed by restriction digestion. A restriction map of the 14.3 and 5.6 kb plasmids is presented. Plasmid-curing studies suggest that these plasmids are involved in lactose metabolism and peptidase activity. 相似文献
5.
Maura Turriani Rossana Pesi Antonella Nardone Gino Turchi Francesco Sgarrella Pier Luigi Ipata Maria Grazia Tozzi 《Journal of biochemical and molecular toxicology》1994,9(1):51-57
Nucleoside phosphotransferase acting on inosine and deoxyinosine has been partially purified from cultured Chinese hamster lung fibroblasts (V79). The activity is associated with a cytosolic 5′-nucleotidase acting on IMP and deoxyIMP. The transfer of the phosphate group from IMP to inosine catalyzed by this enzyme was activated by ATP and 2,3-bisphosphoglycerate. Inosine, deoxyinosine, guanosine, deoxyguanosine, and the nucleoside analogs 2′,3′-dideoxyinosine and 8-azaguanosine are substrates, while adenosine and deoxyadenosine are not. IMP, deoxyIMP, GMP, and deoxyGMP are the best phosphate donors. The cytosolic 5′-nucleotidase/phosphotransferase substrate, 8-azaguanosine, was found to be very toxic for cultured fibroblasts (LD50 = 0.32 μM). Mutants resistant to either 8-azaguanosine and the correspondent base 8-azaguanine were isolated and characterized. Our results indicated that the 8-azaguanosine-resistant cells were lacking both cytosolic 5′-nucleotidase and hypoxanthine-guanine phosphoribosyltransferase, while 8-azaguanine resistant cells were lacking only the latter enzyme. Despite this observation, both mutants displayed 8-azaguanosine resistance, thus indicating that cytosolic 5′-nucleotidase is not essential for the activation of this nucleoside analog. 相似文献
6.
7.
Rino Cella Roberta Colombo Maria Grazia Galli Erik Nielsen Franco Rollo Francesco Sala 《Physiologia plantarum》1982,55(3):279-284
Rice ( Oryza sativa L.) cells returning to in vitro culture after preservation at superlow temperature in liquid nitrogen are characterized by a number of physiological alterations. These include: reduction in respiration and glucose uptake, loss of intracellular potassium, decrease in the cellular level of key metabolites (ATP, glucose-6-phosphate and pyruvate) and fragility of protoplasts following the action of cell wall-degrading enzymes.
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time. 相似文献
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time. 相似文献
8.
Aminophylline, an inhibitor of cyclic nucleotide phosphodiesterase (EC 3.1.4.17), inhibits elongation and correlated H+ and K+ transport in embryos of Haplopappus gracilis and in pea internode segments. Moreover, the drug strongly inhibits the stimulation of these processes by fusicoccin and indole-3-acetic acid and reduces passive permeability of the membrane. The possible mechanisms of action of aminophylline are discussed.Abbreviations cAMP
adenosine 3:5-cyclic monophosphate
- FC
fusicoccin
- IAA
indole-3-acetic acid
- MES
2-N-morpholinoethanesulfonic acid
- PDE
cyclic nucleotide phosphodiesterase 相似文献
9.
M Grazia Tozzi U D'Arcangelo A Del Corso G W Ordal 《Biochimica et biophysica acta》1991,1080(2):160-164
A Ca(2+)-binding protein was identified in Bacillus subtilis in the log phase of growth. The molecular mass of this protein is about 38 kDa as estimated by polyacrylamide gel electrophoresis in the presence of SDS and by gel filtration. The protein was found to be resistant 10 min at 65 degrees C and was purified about 400 times, starting from heated crude extract, by conventional procedures. This novel protein is able to bind Ca2+ in the presence of an excess of MgCl2 and KCl both in solution and after SDS gel electrophoresis and electrotransfer. Since an impairment of the Ca2+ intake, in Bacillus subtilis, results in an impairment of chemotactic behavior (Matsushita, T. et al (1988) FEBS lett. 236, 437-440), 38 kDa protein may be involved in the regulation of chemotaxis. 相似文献
10.
F. Rubio F. de Grazia B.J. Miwa W.A. Garland 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,233(1):149-155
A method is described for measuring (-)-threo-chlorocitric acid in human plasma. Plasma is acidified to pH 1 to minimize lactonization and a13C analogue of (-)-threo-chlorocitric acid is added as internal standard. The acidified plasma is then extracted with ethyl acetate containing 10% methanol. The ethyl acetate—methanol extract is back-extracted with acetate buffer (pH 5). This extract, following adjustment to pH 1, is reextracted with ethyl acetate. The residue after removal of the ethyl acetate is treated with ethereal diazomethane. The wet residue is reconstituted in ethyl acetate and a portion of this solution is analyzed by gas chromatography—chemical ionization mass spectrometry. The mass spectrometer is set to monitorm/z269 [MH+ of trimethylated (-)-threo-chlorocitric acid] andm/z270 [MH+ of trimethylated (-)-threo-[13C]chlorocitric acid] in the gas chromatographic effluent. Them/z/269 tom/z270 ion ratio in a sample containing an unknown amount of (-)-threo-chlorocitric acid is converted to an amount of compound using a calibration curve. The calibration curve is generated by analyzing control plasma spiked with various known amounts of (-)-threo-chlorocitric acid and a fixed amount of (-)-threo-[13C]chlorocitric acid. The limit of quantitation is 0.1–0.6 μg ml−1, depending on the characteristics of the calibration curve generated with each set of samples. The precision (relative standard deviation) at a concentration of 2 μg ml−1 is 3.3%. 相似文献