全文获取类型
收费全文 | 8887篇 |
免费 | 636篇 |
出版年
2023年 | 34篇 |
2022年 | 81篇 |
2021年 | 150篇 |
2020年 | 71篇 |
2019年 | 115篇 |
2018年 | 162篇 |
2017年 | 146篇 |
2016年 | 237篇 |
2015年 | 321篇 |
2014年 | 388篇 |
2013年 | 614篇 |
2012年 | 656篇 |
2011年 | 646篇 |
2010年 | 377篇 |
2009年 | 300篇 |
2008年 | 501篇 |
2007年 | 527篇 |
2006年 | 489篇 |
2005年 | 466篇 |
2004年 | 412篇 |
2003年 | 369篇 |
2002年 | 367篇 |
2001年 | 167篇 |
2000年 | 173篇 |
1999年 | 149篇 |
1998年 | 100篇 |
1997年 | 86篇 |
1996年 | 82篇 |
1995年 | 74篇 |
1994年 | 63篇 |
1993年 | 69篇 |
1992年 | 113篇 |
1991年 | 83篇 |
1990年 | 84篇 |
1989年 | 77篇 |
1988年 | 60篇 |
1987年 | 65篇 |
1986年 | 58篇 |
1985年 | 52篇 |
1984年 | 64篇 |
1983年 | 61篇 |
1982年 | 24篇 |
1981年 | 33篇 |
1979年 | 40篇 |
1978年 | 24篇 |
1975年 | 28篇 |
1974年 | 22篇 |
1973年 | 22篇 |
1970年 | 22篇 |
1967年 | 20篇 |
排序方式: 共有9523条查询结果,搜索用时 15 毫秒
101.
102.
The role played by glycogenolysis in the ischemic heart has been recently put into question because it is suspected that a slowing down of this process could be beneficial for the tolerance of the myocardium to ischemia. The role of the intracellular effectors that control the rate of glycogenolysis has therefore regained interest. We aimed to understand the role played by those intracellular effectors which are directly related to the energy balance of the heart. To this end, we review some of the previously published data on this subject and we present new data obtained from P-31 and C-13 NMR spectroscopic measurement on isolated rat heart. Two conditions of ischemia were studied: 15 min global no-flow and 25 min low-flow ischemia. The hearts were isolated either from control animals or from rats pre-treated with isoproterenol (5 mg.kg–1 b.w. i.p.) 1 h before the perfusion in order to C-13 label glycogen stores. Our main results are as follows: (1) the biochemically determined glycogenolysis rate during the early phase of ischemia (up to 10–15 min) was larger in no-flow ischemia than in low-flow conditions for both groups, (2) direct measurement of the glycogenolysis rate, as determined by C-13 NMR, after labelling of the glycogen pool in the hearts from isoproterenol-treated rats, confirms the estimations from the biochemical data, (3) glycogenolysis was slower in the hearts from pre-treated animals than in control hearts for both conditions of ischemia, (4) the total activity of glycogen phosphorylase (a + b) increased, by 50%, after 5 min no-flow ischemia, whereas it decreased by 42% after the same time of low-flow ischemia. However, the ratio phosphorylase a/a + b was not altered, whatever the conditions, (5) the concentration of inorganic phosphate (Pi) increased sharply during the first minutes of ischemia, to values above 8–10 mM, under all conditions studied. The rate of increase was larger during no-flow ischemia than during low-flow ischemia. The concentration of Pi was thereafter higher in controls than in the hearts from isoproterenol-treated animals.The calculated cytosolic concentration of free 5 AMP increased sharply at the onset of ischemia, reaching in a few minutes values above 30 M in controls and significantly lower values, around 15 M, in the hearts from isoproterenol-treated rats. (6) The hearts from isoproterenol-treated rats displayed a reduced intracellular acidosis, when compared to controls, under both conditions of ischemia.We conclude that the intracellular effectors, mainly free AMP, play an essential role in the control of glycogenolysis via allosteric control of phosphorylase b activity. The alteration in the concentration of free Pi, the substrate of both forms of phosphorylase, can also be considered as determinant in the control of the rate of glycogenolysis.The attenuation of ischemia-induced intracellular acidosis in the hearts from isoproterenol-treated rats could be a consequence of a reduced glycogenolytic rate and is likely to be related to a better resumption of the mechanical function on reperfusion. 相似文献
103.
104.
Selenium,zinc, and thyroid hormones in healthy subjects 总被引:3,自引:0,他引:3
Oliviero Olivieri Domenico Girelli Anna Maria Stanzial Luigi Rossi Antonella Bassi Roberto Corrocher 《Biological trace element research》1996,51(1):31-41
Iodothyronine 5′ deiodinase, which is mainly responsible for peripheral T3 production, has recently been demonstrated to be a selenium (Se)-containing enzyme. The structure of nuclear thyroid hormone
receptors contains Zinc (Zn) ions, crucial for the functional properties of the protein. In the elderly, reduced peripheral
conversion of T4 to T3 with a lower T3/T4 ratio and overt hypothyroidism are frequently observed. We measured serum Se and RBC GSH-Px (as indices of Se status), circulating
and RBC Zinc (as indices of Zn status), thyroid hormones and TSH in 109 healthy euthyroid subjects (52 women, 57 men), carefully
selected to avoid abnormally low thyroid hormone levels induced by acute or chronic diseases or calorie restriction. The subjects
were subdivided into three age groups. To avoid under- or malnutrition conditions, dietary records were obtained for a sample
of 24 subjects, randomly selected and representative of the whole population for age and sex. Low T3/T4 ratios and reduced Se and RBC GSH-Px activity were observed only in the older group. A highly significant linear correlation
between the T3/T4 ratio and indices of Se status was observed in the older group of subjects (r=0.54;p<0.002, for Se;r=0.50;p<0.002, for RBC GSH-Px). Indices of Zn status did not correlate with thyroid hormones, but RBC Zn was decreased in older as
compared with younger subjects. We concluded that reduced peripheral T4 conversion is related to impaired Se status in the elderly. 相似文献
105.
Lino Piccinini Paola Borella Annalisa Bargellini Cristina Incerti Medici Alessandra Zoboli 《Biological trace element research》1996,51(1):23-30
The purpose of our study was to investigate the relationship between plasma and hair levels of Se, Zn, and Cu, and cancer.
We selected a total of 66 patients affected by either breast (38) or lung (28) cancer. They entered into the study at the
onset of disease, and before any chemical or radiotherapy. Controls were randomly selected among healthy people and were matched
for sex, age, smoking habits, and residence. In the group of breast cancer, a significant decrease in hair Se was found compared
to controls (p<0.01), whereas plasma Se was only slightly decreased. No difference between cases and controls was detected in both hair
and plasma levels of Zn and Cu. Subjects who developed lung cancer were significantly lower in hair Zn (p<0.05) and Cu (p<0.01) than controls, whereas there was no difference with regard to Se. In addition, plasma Cu of these patients was increased
as compared to controls. 相似文献
106.
Jose Pontón Fernando L. Hernando Maria Dolores Moragues Pedro L. Barea Mara Gerloni Stefania Conti Paola Fisicaro Cristina Cantelli Luciano Polonelli 《Mycopathologia》1996,133(2):89-94
The presence of heat shock mannoproteins (HSMPs) reactive with sIgA was demonstrated in several C. albicans strains. The subculture of the C. albicans isolated from mucosal surfaces on Sabouraud's dextrose agar at 25 °C switched off the HSMP expression. A re-expression of the HSMPs was obtained in the same medium by shifting the temperature of incubation to 37 °C. However, expression of HSMPs in two strains isolated from deep infections was maintained during several subcultures on Sabouraud's dextrose agar at 25 °C. A glycoprotein of 200 kDa seemed to be the main HSMP reacting with vaginal sIgA. The data presented in this study suggest that factors other than temperature can influence the expression of C. albicans HSMPs and therefore these antigens should be referred as stress mannoproteins.Abbreviations HSMPs
heat shock mannoproteins
- MAb
monoclonal antibody
- sIgA
secretory IgA 相似文献
107.
David Bouchez Paola Vittorioso Béatrice Courtial Christine Camilleri 《Plant Molecular Biology Reporter》1996,14(2):115-123
We have designed a new method for the recovery of T-DNA flanking sequences from T-DNA-tagged lines ofArabidopsis thaliana. Since most transformation vectors in use contain a plant-selectable marker for kanamycin resistance, we can use the 3′ part
of thenptII coding region from the T-DNA to complement the bacterial 5′ region of thenptII gene from Tn5 to reconstruct a functional kanamycin-resistance gene inEscherichia coli. We have constructed a vector that contains the 5′ part of thenptII gene from Tn5 up to the uniquePst I site. By cloning total DNA from transformed lines in this vector, we were able to select directly for clones containing
a T-DNA fragment, which reconstitutes a functional kanamycin gene, and a fragment of arabidopsis genomic DNA adjacent to the
insertion. Flanking sequences up to 4 kb were rescued by this system. 相似文献
108.
109.
110.
BET3 encodes a novel hydrophilic protein that acts in conjunction with yeast SNAREs. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G Rossi K Kolstad S Stone F Palluault S Ferro-Novick 《Molecular biology of the cell》1995,6(12):1769-1780
Here we report the identification of BET3, a new member of a group of interacting genes whose products have been implicated in the targeting and fusion of endoplasmic reticulum (ER) to Golgi transport vesicles with their acceptor compartment. A temperature-sensitive mutant in bet3-1 was isolated in a synthetic lethal screen designed to identify new genes whose products may interact with BET1, a type II integral membrane protein that is required for ER to Golgi transport. At 37 degrees C, bet3-1 fails to transport invertase, alpha-factor, and carboxypeptidase Y from the ER to the Golgi complex. As a consequence, this mutant accumulates dilated ER and small vesicles. The SNARE complex, a docking/fusion complex, fails to form in this mutant. Furthermore, BET3 encodes an essential 22-kDa hydrophilic protein that is conserved in evolution, which is not a component of this complex. These findings support the hypothesis that Bet3p may act before the assembly of the SNARE complex. 相似文献