全文获取类型
收费全文 | 5866篇 |
免费 | 418篇 |
国内免费 | 1篇 |
专业分类
6285篇 |
出版年
2023年 | 28篇 |
2022年 | 74篇 |
2021年 | 150篇 |
2020年 | 60篇 |
2019年 | 81篇 |
2018年 | 120篇 |
2017年 | 106篇 |
2016年 | 181篇 |
2015年 | 303篇 |
2014年 | 295篇 |
2013年 | 411篇 |
2012年 | 493篇 |
2011年 | 466篇 |
2010年 | 285篇 |
2009年 | 224篇 |
2008年 | 350篇 |
2007年 | 337篇 |
2006年 | 315篇 |
2005年 | 289篇 |
2004年 | 282篇 |
2003年 | 248篇 |
2002年 | 251篇 |
2001年 | 59篇 |
2000年 | 56篇 |
1999年 | 68篇 |
1998年 | 57篇 |
1997年 | 55篇 |
1996年 | 26篇 |
1995年 | 37篇 |
1994年 | 41篇 |
1993年 | 41篇 |
1992年 | 41篇 |
1991年 | 28篇 |
1990年 | 33篇 |
1989年 | 39篇 |
1988年 | 31篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 24篇 |
1978年 | 12篇 |
1976年 | 22篇 |
1975年 | 8篇 |
1973年 | 14篇 |
1972年 | 18篇 |
排序方式: 共有6285条查询结果,搜索用时 8 毫秒
21.
Suppression of ouabain-insensitive K-ATPase activity in rabbit nephron segments during chronic hyperkalemia 总被引:1,自引:0,他引:1
Recently, we demonstrated that an ATPase stimulated by K (and not inhibited by ouabain, Na-K-ATPase inhibitor) is present in the connecting tubule (CNT) and collecting duct segments of the rabbit. In this study, we determined the effects of high- and low-K diet on K-ATPase activity in the CNT and collecting duct segments of rabbit. One group of animals was given a low-K diet (34 mEq/kg diet) and the other group was given a high-K diet (700 mEq/kg diet) for 1 week. K-ATPase activity was measured by a microfluorometric assay in which ATP hydrolysis is coupled to oxidation of NADH. Low-K animals had plasma K = 3.1 +/- 0.2 as compared with 5.5 +/- 0.5 mEq/l in high-K animals. Low-K animals had significant K-ATPase activity in CNT, CCD (cortical collecting duct) and MCD (medullary collecting duct). On the other hand, K-ATPase activity in all 3 segments from high-K animals was not significantly different from zero. These results support a hypothesis that chronic K loading suppresses the ouabain-insensitive K-ATPase in the distal nephron. 相似文献
22.
The molecular biology of plant acclimation to low temperature 总被引:51,自引:8,他引:43
23.
24.
25.
Cecilia Del Casino Yi-Qin Li Alessandra Moscatelli Monica Scali Antonio Tiezzi Mauro Cresti 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,79(2):125-132
Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes. 相似文献
26.
Forskolin, an adenylate cyclase activator and a cyclic AMP analogue, dibutyryl cyclic AMP have been used to examine the relationship
between intracellular levels of cyclic AMP and lipid synthesis inMycobacterium smegmatis. Total phospholipid content was found to be increased in forskolin grown cells as a result of increased cyclic AMP levels
caused by activation of adenylate cyclase. Increased phospholipid content was supported by increased [14C] acetate incorporation as well as increased activity of glycerol-3-phosphate acyltransferase. Pretreatment of cells with
dibutyryl cyclic AMP had similar effects on lipid synthesis. Taking all these observations together it is suggested that lipid
synthesis is being controlled by cyclic AMP in mycobacteria. 相似文献
27.
Dr Massimo Bruatto Marilena Gremmi Antonella Nardacchione Monica Amerio 《Mycopathologia》1993,123(2):105-110
By incubating starved and unstarved yeast cells in synthetic media with a pH of 4.5 or 6.7 at 37°C the effect of a 3 hours' glucose starvation on germ-tube production byCandida albicans was evaluated. In addition the endocellular content of total carbohydrates, glycogen, trehalose and proteins after and before the starvation were dosed. The most interesting result was the overcoming of the pH-regulated dimorphism, thanks to the starvation treatment. Infact the starved cultures produced germtubes indifferently in neutral or acid media, whereas the filamentation of the unstarved cultures was more copious in pH 6.7 medium. The endocellular content of trehalose and protein was unchanged, whereas total carbohydrates and glycogen showed a shortage after the 3 hours' glucose starvation. The possible involvements of these metabolic changes in the regulation of dimorphic transition are discussed. 相似文献
28.
29.
Bjørn-Yngvar Nordvåg Ida Ranløv Hilde Monica Frostad Riise Gunnar Husby M. Raafat El-Gewely 《Human genetics》1993,92(3):265-268
Severe familial amyloid cardiomyopathy (FAC) in a Danish kindred is associated with a specific mutation (Met for Leu 111) in the transthyretin (TTR) gene. The mutation causes the loss of a DdeI restriction site in the gene, allowing molecular diagnostic studies. We studied formalin-fixed, paraffin-embedded tissues, up to 39 years old, from 29 family members of this kindred. DNA was partially purified from deparaffinized tissue sections and a DNA sequence of the TTR gene flanking the mutation site was amplified by the polymerase chain reaction (PCR), followed by restriction enzyme analysis. Amplified DNA was obtained from tissues representing 23 of the 29 persons. Ten out of the 23 family members were found to carry the TTR Met 111 mutation, whereas 13 were not affected. The results were consistent with known clinical data and with corresponding serum TTR examinations. This retrospective study shows that archival tissues can be used to confirm the diagnosis and disease pattern in members of families affected by hereditary diseases. 相似文献
30.
N-nitro-l-arginine (NG-nitro-l-arginine) is a potent nitric oxide synthase inhibitor which crosses the blood brain barrier and does not undergo extensive metabolism in vivo. In this study, effect of chronic pretreatment of N-nitro-l-arginine (75 mg/kg, i.p., twice daily for 7 days) on the harmaline- (100 mg/kg, s.c.), picrotoxin- (4 mg/kg, s.c.), pentylenetetrazole- (50 mg/kg, i.p.), andl-glutamic acid- (400 g/10 l/mouse, i.c.v.) induced increase in cerebellar cGMP was assessed. All the four drugs produced significant increase in cerebellar cGMP in vehicle pretreated control animals. Cerebellar cGMP increase induced by harmaline, picrotoxin, andl-glutamic acid was attentuated in N-nitro-l-arginine pretreated animals. These results indicate that in vivo cerebellar cGMP levels are increased by the prototype excitatory amino acid receptor agonist,l-glutamic acid and also by the drugs which augment the excitatory amino acid transmission. Furthermore, parenteral chronic administration of N-nitro-l-arginine blocks NO synthase in the brain and hence cerebellar cGMP response in chronic N-nitro-l-arginine treated animals could be used as a tool to assess the physiological functions of nitric oxide in vivo.Part of this work was presented at the Experimental Biology 93 FASEB Meeting at New Orleans, March 1993. 相似文献