全文获取类型
收费全文 | 2275篇 |
免费 | 223篇 |
国内免费 | 1篇 |
专业分类
2499篇 |
出版年
2023年 | 14篇 |
2022年 | 27篇 |
2021年 | 51篇 |
2020年 | 30篇 |
2019年 | 39篇 |
2018年 | 41篇 |
2017年 | 39篇 |
2016年 | 79篇 |
2015年 | 125篇 |
2014年 | 130篇 |
2013年 | 157篇 |
2012年 | 159篇 |
2011年 | 194篇 |
2010年 | 132篇 |
2009年 | 106篇 |
2008年 | 114篇 |
2007年 | 156篇 |
2006年 | 98篇 |
2005年 | 117篇 |
2004年 | 124篇 |
2003年 | 126篇 |
2002年 | 103篇 |
2001年 | 31篇 |
2000年 | 11篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 9篇 |
1973年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有2499条查询结果,搜索用时 15 毫秒
1.
2.
Kirsten Skamstrup Hansen Stefan Vieths Helle Vestergaard Per Stahl Skov Carsten Bindslev-Jensen Lars K. Poulsen 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,756(1-2)
The aim of the study was to investigate the possibility of a seasonal variation in reactivity to apples in 27 birch pollen allergic patients. Before and during the birch pollen season 1998, the patients were subjected to double-blind, placebo-controlled food challenges (DBPCFCs) with grated fresh Golden Delicious apple followed by an open food challenge with whole fresh apple. The clinical reactions elicited during the challenges were evaluated both by the patients and the investigators. Moreover, the skin reactivity and the in vitro reactivity to apple were evaluated by skin prick test (SPT), leukocyte histamine release (HR), measurement of specific IgE, and immunoblotting experiments. The sensitivity of the DBPCFC, when compared with the result of the open challenge, was 0.74 (14/19) before the season and 0.80 (16/20) during the season. None of the patients reacted to the blinded challenge without a subsequent reaction to the open challenge. One placebo reaction was registered both before and in season, but not in the same patient. The patient scores of the first positive challenges, and the maximal scores of each combined blinded and open challenge session, were significantly increased during the pollen season (P<0.05). The scores of the open challenge were significantly higher than the scores of the DBPCFC both before the season and during the in-season challenges (P<0.05). Specific IgE against Golden Delicious increased during season (P<0.05), while neither SPT, HR, nor immunoblotting experiments could confirm an increase in reactivity. In conclusion, the results of the oral challenge tests indicated an increase in clinical reactivity to apples during the birch pollen season in birch pollen allergic individuals. 相似文献
3.
Cathrine Laustrup M?ller Rasmus Kj?bsted Pablo J. Enriori Thomas Elbenhardt Jensen Cecilia Garcia-Rudaz Sara A. Litwak Kirsten Raun J?rgen Wojtaszewski Birgitte Schjellerup Wulff Michael A. Cowley 《PloS one》2016,11(7)
The melanocortin system includes five G-protein coupled receptors (family A) defined as MC1R-MC5R, which are stimulated by endogenous agonists derived from proopiomelanocortin (POMC). The melanocortin system has been intensely studied for its central actions in body weight and energy expenditure regulation, which are mainly mediated by MC4R. The pituitary gland is the source of various POMC-derived hormones released to the circulation, which raises the possibility that there may be actions of the melanocortins on peripheral energy homeostasis. In this study, we examined the molecular signaling pathway involved in α-MSH-stimulated glucose uptake in differentiated L6 myotubes and mouse muscle explants. In order to examine the involvement of AMPK, we investigate α-MSH stimulation in both wild type and AMPK deficient mice. We found that α-MSH significantly induces phosphorylation of TBC1 domain (TBC1D) family member 1 (S237 and T596), which is independent of upstream PKA and AMPK. We find no evidence to support that α-MSH-stimulated glucose uptake involves TBC1D4 phosphorylation (T642 and S704) or GLUT4 translocation. 相似文献
4.
Bicarbonate/chloride antiport in Vero cells: I. Evidence for both sodium-linked and sodium-independent exchange 总被引:2,自引:0,他引:2
Tor Inge Tnnessen Jannikke Ludt Kirsten Sandvig Sjur Olsnes 《Journal of cellular physiology》1987,132(2):183-191
The effect of bicarbonate on the ability of cells to regulate the internal pH after acid and alkali loads was studied. In the presence of Na+, the normalization of the internal pH after acid loads occurred more rapidly in the presence than in the absence of bicarbonate. DIDS (4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid) strongly inhibited the pH increase, whereas amiloride inhibited it to a lesser extent. The Na+-linked, bicarbonate-dependent pHi increase after an acid load was strongly reduced in cells depleted of Cl-. When cells were transferred to gluconate or mannitol balanced buffers containing bicarbonate, there was a rapid alkalinization of the cytosol, apparently due to influx of bicarbonate induced by chloride efflux. When the internal pH was below 7.0, the pH increase was much more rapid in the presence than in the absence of Na+, whereas at higher internal pH, there was no measurable effect of Na+. The ability of the cells to reduce the internal pH after an alkali load was increased in the presence of bicarbonate. The data indicate that both Na+-linked and Na+-independent bicarbonate/chloride exchange occur in Vero cells. 相似文献
5.
Didymella bryoniae is very common in cucumber crops grown in Danish glasshouses and is able to attack all aerial parts of the plant. In October 1984 an attack of D. bryoniae on cucumber roots was observed for the first time. Some of the roots were dark because of pseudothecia containing asci. This fact may have importance for the spread and survival of the disease and for its control. 相似文献
6.
Wolfram Lokotsch Kirsten Fritsche Christoph Syldatk 《Applied microbiology and biotechnology》1989,31(5-6):467-472
Summary Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmol·l-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.Dedicated to Prof. Dr. Fritz Wagner on the occasion of his 60th birthday 相似文献
7.
A Sóoki-Tóth G Bánfalvi J Sz?ll?si E Kirsten M Staub F Antoni E Kun 《Experimental cell research》1989,184(1):44-52
Thymic cells were isolated at intervals of between 0 and 144 h from mice that received one intraperitoneal injection of emetine (33 mg/kg), and thymus weight, incorporation of [14C]leucine into proteins and [3H]thymidine into DNA in intact thymic cells, as well as initial rates of protein ADP-ribosylation in permeabilized cells [A. Sóoki-Tóth, F. Asghari, E. Kirsten, and E. Kun (1987) Exp. Cell Res. 170, 93] were simultaneously monitored. The effect of emetine as an inhibitor of protein synthesis [F. Antoni, N. G. Luat, I. Csuka, I. Oláh, A. Sóoki-Tóth, and G. Bánfalvi (1987) Int. J. Immunopharmacol. 9, 333] corresponds to the induction of sequential cellular events, such as cell exit and remigration, by other antimitotic agents [C. Penit and F. Vasseur (1988) J. Immunol. 140, 3315] and produces an activation of proliferation of cells reentering into this organ. Proliferation, as demonstrated by a large increase in DNA synthesis and entrance into S phase, was kinetically related to an apparent increase in poly(ADP-ribose) polymerase activity in thymic cells and a highly significant in vitro ADP-ribosylation of histone H3. Since no DNA fragmentation occurred in thymic cells, as tested by a fluorometric technique [C. Birnboim and J. J. Jevac (1981) Cancer Res. 41, 1889], it is probable that a selective activation of poly(ADP-ribose) polymerase may have been induced in cells that undergo differentiation and proliferation while repopulating the thymus. 相似文献
8.
Kirsten Brandt 《Plant Cell, Tissue and Organ Culture》1991,26(3):195-201
A method for estimating the oxygen availability in plant cell cultures grown in stationary liquid media (e.g. many protoplast cultures) was developed. The method is based on short-term measurements of respiration rate versus oxygen concentration on a sample of cells, suspended in liquid media. From such data it is possible to estimate the oxygen concentration at the bottom of a stagnant liquid culture, by calculating the amount of oxygen reaching the cells by diffusion. As an example, rape (Brassica napus L. cv. Omega) hypocotyl protoplasts were grown with different oxygen concentrations at the site of the cells, obtained by varying the cell density, the height of the liquid layer and the oxygen content of the gas phase. The number of surviving calli was positively correlated with the estimated oxygen availability in the range between 60 and 350 M O2, below 60 M all cells died. This indicates that oxygen availability can be a limiting factor in the range usually encountered in protoplast cultures, and that the method can be useful when designing optimal growth conditions for stationary cultures of plant cells.Abbreviations C1
bulk oxygen concentration in agitated medium
- Co
oxygen concentration in medium at the gas-liquid interface, in equilibrium with the gas
- Cx
oxygen concentration at cell level
- D
diffusion constant of oxygen in water
- KLa
oxygen transfer rate
- l
height of liquid above cells
- n
number of cells per ml
- Rx
respiration rate per cell 相似文献
9.
Steen Kølvraa Torben A. Kruse P. K. A. Jensen Kirsten H. Linde Søren R. Vestergaard Lars Bolund 《Human genetics》1986,74(3):284-287
Summary EDA (ectodermal dysplasia, anhidrotic) is an X-linked recessive disorder characterized by hypohidrosis, hypoor anodontia, and hypotrichosis. A possible linkage between the gene for EDA and a number of restriction fragment length polymorphisms (RFLPs) spread over the X chromosome was investigated in two Danish families segregating EDA. No recombination between the gene for EDA and our probe pTAK8, which detects a two allele polymorphism in the region Xp11-q12, was found in nine informative meiotic events (seven of which are phase known), giving a maximal lod score of 2.41 at a recombination fraction of 0.00. This juxtacentromeric location of the gene for EDA agrees well with the linkage data obtained with the other markers used in this study. 相似文献
10.