全文获取类型
收费全文 | 12675篇 |
免费 | 1024篇 |
国内免费 | 9篇 |
专业分类
13708篇 |
出版年
2023年 | 51篇 |
2022年 | 99篇 |
2021年 | 233篇 |
2020年 | 134篇 |
2019年 | 201篇 |
2018年 | 238篇 |
2017年 | 218篇 |
2016年 | 313篇 |
2015年 | 608篇 |
2014年 | 637篇 |
2013年 | 772篇 |
2012年 | 1054篇 |
2011年 | 1013篇 |
2010年 | 634篇 |
2009年 | 580篇 |
2008年 | 819篇 |
2007年 | 845篇 |
2006年 | 723篇 |
2005年 | 718篇 |
2004年 | 679篇 |
2003年 | 632篇 |
2002年 | 636篇 |
2001年 | 118篇 |
2000年 | 78篇 |
1999年 | 130篇 |
1998年 | 153篇 |
1997年 | 127篇 |
1996年 | 113篇 |
1995年 | 115篇 |
1994年 | 99篇 |
1993年 | 81篇 |
1992年 | 87篇 |
1991年 | 59篇 |
1990年 | 60篇 |
1989年 | 64篇 |
1988年 | 36篇 |
1987年 | 40篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 54篇 |
1983年 | 35篇 |
1982年 | 59篇 |
1981年 | 42篇 |
1980年 | 43篇 |
1979年 | 28篇 |
1978年 | 31篇 |
1977年 | 34篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Pierre Fellmann Jens Andersen Philippe F. Devaux Marc le Maire Alain Bienvenue 《Biochemical and biophysical research communications》1980,95(1):289-295
A spin labeled fatty acid (16-doxylstearic acid) was linked to a photochemical reacting group (azido derivative). When the molecule is introduced, at a low concentration, into rabbit sarcoplasmic reticulum membranes, the spectrum before illumination is identical to the spectrum obtained with the corresponding spin labeled fatty acid. After illumination, a large immobilized components is seen. It corresponds to about 70% of the ESR signal of the effectively bound label, at room temperature. The fraction of immobilized component varies with temperature, from 100% at 0°C to 50% at 35°C. Addition of a small amount of detergent (dodecyl octaethylene glycol monoether), under non solubilizing conditions, decreases the fraction of signal due to a strongly immobilized probe. A possible interpretation is that the immobilized signal reflects protein bound spin labels trapped in Ca2+ ATPase oligomers, which are partially dissociated by detergent addition or temperature increase. 相似文献
12.
Carbohydrate-induced hypertriglyceridemia: modifying factors and implications for cardiovascular risk. 总被引:4,自引:0,他引:4
Marc K Hellerstein 《Current opinion in lipidology》2002,13(1):33-40
High-carbohydrate/low-fat, isocaloric diets have repeatedly been shown to increase plasma triglyceride concentrations. The present review addresses recent developments relevant to several important unresolved issues. These include the type of dietary carbohydrate that is most likely to induce hypertriglyceridemia, predictors of individual susceptibility, modifiable physiologic factors that may mitigate the plasma triglyceride response, underlying metabolic mechanisms that are responsible for increased plasma triglycerides, and implications of altered serum lipid profiles for atherogenic risk. Although some progress has been made in this field, the central public health issue - the net effect on cardiovascular risk - remains unresolved. 相似文献
13.
14.
In spite of successful biological control efforts, vast areas of South Africa remain infested with the spiny prickly pear weed, Opuntia ficus-indica. These remnant populations, which vary from sparse to dense and which are more or less stable, are confined mainly to the eastern Cape. They provide a popular fruit and a limited source of income for certain sectors of the population in these areas. In terms of existing legislation, there are, however, restrictions on the large-scale utilization of these fruit. A novel method for mass-rearing the cochineal insect, Dactylopius coccus, for the commercial production of a red dye (carminic acid) has been developed. The cultivated spineless prickly pear has recently been enjoying renewed attention from researchers and growers alike. Whereas it has traditionally been cultivated mainly as a droughtresistant fodder crop, and is still popular as such, it is now increasingly recognised as a fruit, in its own right, with considerable promise as a commercial crop for local and export markets. There is also a need to encourage the use of very young cladodes (nopalitos) as a highly nutritious vegetable for human consumption in South Africa. 相似文献
15.
Dominique Dorin-Semblat Claudia Demarta-Gatsi Romain Hamelin Florence Armand Teresa Gil Carvalho Marc Moniatte Christian Doerig 《PloS one》2015,10(12)
Casein kinase 1 (CK1) is a pleiotropic protein kinase implicated in several fundamental processes of eukaryotic cell biology. Plasmodium falciparum encodes a single CK1 isoform, PfCK1, that is expressed at all stages of the parasite’s life cycle. We have previously shown that the pfck1 gene cannot be disrupted, but that the locus can be modified if no loss-of-function is incurred, suggesting an important role for this kinase in intra-erythrocytic asexual proliferation. Here, we report on the use of parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus to investigate (i) the dynamics of PfCK1 localisation during the asexual cycle in red blood cells, and (ii) potential interactors of PfCK1, so as to gain insight into the involvement of the enzyme in specific cellular processes. Immunofluorescence analysis reveals a dynamic localisation of PfCK1, with evidence for a pool of the enzyme being directed to the membrane of the host erythrocyte in the early stages of infection, followed by a predominantly intra-parasite localisation in trophozoites and schizonts and association with micronemes in merozoites. Furthermore, we present strong evidence that a pool of enzymatically active PfCK1 is secreted into the culture supernatant, demonstrating that PfCK1 is an ectokinase. Our interactome experiments and ensuing kinase assays using recombinant PfCK1 to phosphorylate putative interactors in vitro suggest an involvement of PfCK1 in many cellular processes such as mRNA splicing, protein trafficking, ribosomal, and host cell invasion. 相似文献
16.
Acetobacter acetii DSMZ3508 and related bacteria converted 2,2-dimethyl-1,3-propanediol into 3-hydroxypivalic acid (2,2-dimethyl-3-hydroxypropionic acid; 3HP) during submerged cultivation in mineral salt medium. The maximum yield of 3-hydroxypivalic acid was 24.4% of the fed substrate after 18 days. Cultivation parameters, as pH, cell density, optimal substrate concentration, and oxygen supply for the bioconversion process were determined. 相似文献
17.
18.
19.
Alterations in neostriatal dopamine metabolism, release, and biosynthesis were determined 3, 5, or 18 days following partial, unilateral destruction of the rat nigrostriatal dopamine projection. Concentrations of dopamine and each of its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 3-methoxytyramine (3-MT) were markedly decreased in the lesioned striata at 3, 5, or 18 days postoperation. The decline in striatal high-affinity [3H]dopamine uptake closely matched the depletion of dopamine at 3 and 18 days postoperation. However, neither DOPAC, HVA, nor 3-MT concentrations were decreased to as great an extent as dopamine at any time following lesions that depleted the dopamine innervation of the striatum by greater than 80%. In these more severely lesioned animals, dopamine metabolism, estimated from the ratio of DOPAC or HVA to dopamine, was increased two- to four-fold in the injured hemisphere compared with the intact hemisphere. Dopamine release, estimated by the ratio of 3-MT to dopamine, was more increased, by five- to sixfold. Importantly, the HVA/dopamine, DOPAC/dopamine, and 3-MT/dopamine ratios did not differ between 3 and 18 days postlesioning. The rate of in vivo dopamine biosynthesis, as estimated by striatal DOPA accumulation following 3,4-dihydroxyphenylalanine (DOPA) decarboxylase inhibition with NSD 1015, was increased by 2.6- to 2.7-fold in the surviving dopamine terminals but again equally at 3 and 18 days postoperation. Thus, maximal increases in dopamine metabolism, release, and biosynthesis occur rapidly within neostriatal terminals that survive a lesion. This mobilization of dopaminergic function could contribute to the recovery from the behavioral deficits of partial denervation by increasing the availability of dopamine to neostriatal dopamine receptors. However, these presynaptic compensations are not sufficient to account for the protracted (at least 3-week) time course of sensorimotor recovery that has been observed following partial nigrostriatal lesion. 相似文献
20.