全文获取类型
收费全文 | 1912篇 |
免费 | 99篇 |
国内免费 | 2篇 |
专业分类
2013篇 |
出版年
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 3篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 33篇 |
2014年 | 57篇 |
2013年 | 79篇 |
2012年 | 81篇 |
2011年 | 78篇 |
2010年 | 73篇 |
2009年 | 68篇 |
2008年 | 123篇 |
2007年 | 117篇 |
2006年 | 120篇 |
2005年 | 118篇 |
2004年 | 120篇 |
2003年 | 101篇 |
2002年 | 125篇 |
2001年 | 23篇 |
2000年 | 14篇 |
1999年 | 31篇 |
1998年 | 39篇 |
1997年 | 29篇 |
1996年 | 34篇 |
1995年 | 26篇 |
1994年 | 29篇 |
1993年 | 32篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 36篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1975年 | 8篇 |
1974年 | 15篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有2013条查询结果,搜索用时 0 毫秒
1.
Chafik Maazouzi Gérard Masson Maria Soledad Izquierdo Jean-Claude Pihan 《Journal of thermal biology》2008
The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002. 相似文献
2.
Lens regeneration from cultured newt irises stimulated by retina-derived growth factors (EDGFs) 总被引:1,自引:0,他引:1
Robert Cuny Jean-Claude Jeanny Yves Courtois 《Differentiation; research in biological diversity》1986,32(3):221-229
It has been shown that lens regeneration from the iris of the newt Notophthalmus viridescens is dependent on the presence of neural retinal tissue in organ culture and in vivo. The recent discovery of various eye-derived growth factors (EDGFs) in the bovine retina [14] prompted us to investigate whether one of these factors may be involved in the stimulation of lens regeneration. Dorsal irises were cultured for 20 days in serum-supplemented diluted Eagle's medium. Growth factors from bovine retina of various degrees of purification were added. Lens regeneration was assessed on the basis of morphological lens-regeneration stages and by immunofluorescent detection of a lens-specific marker protein, alpha-crystallin. Crude isotonic retinal extract at 80-800 micrograms/ml significantly augmented lens regeneration. Very similar results were obtained when EDGF III, the nonretained retinal factor after heparin-affinity chromatography, was present at 2-20 micrograms/ml. Lens regeneration was also significantly increased when EDGF II, the retinal form of acidic fibroblast growth factor (aFGF) at 50-500 ng/ml was added to the cultures. On the other hand, EDGF I at 4-40 ng/ml and brain basic FGF at 5-50 ng/ml did not seem to significantly stimulate lens regeneration under the conditions used. Our results suggest that at least two retina-derived growth factors (EDGF II and III) can stimulate lens regeneration. These growth factors may be the putative signal that is naturally produced by the retina during lens regeneration in the newt. 相似文献
3.
Brigitte Aupetit Alexandre Ghazi Nicole Blanchouin Ren e Toury Emmanuel Shechter Jean-Claude Legrand 《BBA》1988,936(3):325-331
In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies). Inhibition of respiratory intensity by cyclosporine did not exceed 21.1% in vitro and 15.9% in vivo. Since there was no in vitro inhibition of succinate cytochrome-c reductase and cytochrome-c oxidase activities, the slowing of electron flow observed can be interpreted as a consequence of an effect produced by cyclosporine between cytochromes b and c1. Cyclosporine had no effect on respiratory control either in vitro or in vivo. Statistically significant inhibition of the oxidative phosphorylation was observed both in vitro (6.6%) and in vivo (12.1%). Moreover, cyclosporine did not induce any change of membrane potential either in vivo or in vitro. Our findings show that cyclosporine is neither a protonophore, nor a potassium ionophore. In cyclosporine-treated rats we noticed a decrease of protein in subcellular fraction, including the mitochondrial fraction. The role of the inhibition respiratory characteristics by cyclosporine in nephrotoxicity in vivo must take account of these two parameters: inhibition of the respiratory characteristics measured in vitro and diminution of mitochondrial protein in cyclosporine-treated rats. 相似文献
4.
5.
Effects of preformed proline and proline amino acid precursors (including glutamine) on collagen synthesis in human fibroblast cultures 总被引:1,自引:0,他引:1
A technique of derivatizing proline and 4-hydroxyproline with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole was used to measure the radioactivities, concentrations and specific activities of proline and hydroxyproline. The technique was used to study the conditions of procollagen synthesis in cultured human foreskin fibroblasts. Procollagen synthesis appeared to be independent of the proline concentration in the medium, in the presence of glutamine, when monitored by the assay of non-dialyzable hydroxyproline, but not when monitored by [14C]proline incorporation. In the absence of unlabelled proline added to labelled proline in the medium, the specific activity of the secreted procollagen did not reach a plateau over a 24-h period. When the medium was supplemented with glutamine, glutamic acid, or aspartic acid, both the radioactivity and concentration of intracellular free proline decreased. Pyrrolidone-2-carboxylic acid and ornithine both induced a slight increase in concentration of the intracellular free proline. Glutamine competed with [14C]proline for incorporation into prolyl-tRNA and procollagen, independently of free intracellular proline, and it stimulated the biosynthesis of procollagen (expressed as non-dialyzable hydroxyproline) by a factor of 2.3. 相似文献
6.
Gerard Strecker Jean-Michel Wieruszeski Jean-Claude Michalski Jean Montreuil 《Glycoconjugate journal》1988,5(4):385-396
The structure of a new nonasaccharide isolated from human milk has been investigated. By using methylation analysis, FAB-MS and1H-and13C-NMR spectroscopy as basic methods of structural investigation, this oligosaccharide was identified as VI2--Fuc,V4-Fuc,III3--Fuc-p-lacto-n-hexaose: Fuc1-2Gal1-3[Fuc1-4]GlcNAc1-3Gal1-4[Fuc1-3]GlcNAc1-3Gal1-4Glc.Abbreviations COSY
correlation spectroscope
- DP
degree of polymerisation
- FAB-MS
fast atom bombardment-mass spectrometry
- HPLC
high performance liquid chromatography
- NMR
nuclear magnetic resonance
- GLC
gas-liquid chromatography 相似文献
7.
Khalid M. Chraibi B Jean-Claude Castelle Alain Latche Jean-Paul Roustan Jean Fallot 《Plant cell reports》1992,10(12):617-620
We describe here a liquid culture system for the regeneration of shoots at high frequencies from mature cotyledon tissues of three genotypes of sunflower (Helianthus annuus L.) one of which had previously been found to be recalcitrant to regeneration when cotyledons were cultured on solid medium. Cotyledons were excised from 2-day-old seedlings and incubated in liquid Murashige and Skoog's modified medium supplemented with 5.4 M naphthaleneacetic acid (NAA) and 4.4 M benzylaminopurine (BAP). After two weeks in culture, the whole upper surface of regenerating explants was covered with green shootlets. The percentages of regenerating explants of three genotypes varied between 60 and 70%, and the number of shoots per regenerating explant was highly increased. The shootlets were transferred to solid Murashige and Skoog's medium allowing shoot development, then to rooting medium. Rooted plantlets were successfully acclimatized and gave fertile plants. The role of liquid medium culture in the induction of sunflower regeneration is discussed.Abbreviations BAP
6-benzylaminopurine
- NAA
1-naphthaleneacetic acid
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid 相似文献
8.
Parenteral supplementation with zinc in surgical patients corrects postoperative serum-zinc drop 总被引:2,自引:0,他引:2
Henri Faure Jean-Claude Peyrin Marie-Jeanne Richard Alain Favier 《Biological trace element research》1991,30(1):37-45
Zinc has been known for a long time to facilitate wound healing. But, so far, supplementation trials in patients treated by major severity surgery gave either partial or controversial results. In a double-blind, randomized study including 30 patients, we show that zinc supplements (30 mg/d for 3 d) administered by a drip correct postoperative drop of serum zinc, that this correction concerns the available part of serum zinc (i.e., zinc that is bound to compounds other than alpha-2 macroglobulin in serum), and that this supplementation can improve clinical wound healing. Possible influence of increased urinary output after the intervention is discussed, and we found that serum cortisol remains stable when zinc/albumin ratio is stable, and increases sharply when the same ratio drops. Cortisol, therefore, seems to play a major role in zinc redistribution after surgery. 相似文献
9.
Stability of Bradyrhizobium japonicum Inoculants after Introduction into Soil 总被引:4,自引:3,他引:1 下载免费PDF全文
Brigitte Brunel Jean-Claude Cleyet-Marel Philippe Normand Rene Bardin 《Applied microbiology》1988,54(11):2636-2642
Bradyrhizobium japonicum USDA 125-Sp, USDA 138, and USDA 138-Sm had been used as inoculants for soybean (Glycine max (L.) Merr.) in soils previously free of B. japonicum. At 8 to 13 years after their release, these strains were reisolated from soil samples. A total of 115 isolates were obtained through nodules, and seven colonies were obtained directly by a serological method. The stability of the inoculants was confirmed by comparing the reisolated cultures with their respective parental strains which had been preserved by being lyophilized or stored on a yeast extract-mannitol agar slant at 4°C. Comparisons were made on morphological and serological characters, carbon compound utilization (8 tested), intrinsic antibiotic resistance (9 tested), and enzymatic activity (19 tested). Mucous and nonmucous isolates of serogroup 125 were analyzed for symbiotic effectiveness and restriction fragment hybridization with a DNA probe. Our data suggest that the B. japonicum inoculants have survived for up to 13 years in the soils without significant mutation except for two reisolates with a slightly increased kanamycin resistance level. 相似文献
10.
Acetylene Metabolism and Stimulation of Denitrification in an Agricultural Soil 总被引:1,自引:1,他引:0 下载免费PDF全文
The effects of C2H2 metabolism on N2O production were examined in soil slurries. Enrichment of C2H2 consumption activity occurred only in aerobic incubations. Rapid disappearance of subsequent C2H2 additions, stimulation of CO2 production, and most-probable-number enumerations of C2H2 utilizers indicated enrichment of the population responsible. During C2H2 consumption in slurries incubated statically under air, maximal rates of N2O evolution were 19 times higher than those in anaerobic incubations. After 20 days of enrichment with C2H2, the production of N2O by slurries supplemented with C2H2 and nitrate was 10 times higher than that in the unenriched controls. A Nocardia- or Arthrobacter-like bacterium was isolated that grew on C2H2 but did not denitrify. The behavior of soil inoculated with this bacterium became similar to that of C2H2-enriched soil incubated aerobically. Ethanol, acetate, and acetaldehyde were identified in enrichment experiments, and denitrification in soil slurries was stimulated by addition of the supernatant from a pure culture grown on mineral medium with C2H2. These results indicate that denitrification can be stimulated by the actions of an aerobic, nondenitrifying C2H2-metabolizing population. Utilization of intermediate metabolites by denitrifiers and enhanced O2 consumption are two possible mechanisms for this stimulation. 相似文献