全文获取类型
收费全文 | 5313篇 |
免费 | 371篇 |
出版年
2023年 | 41篇 |
2022年 | 55篇 |
2021年 | 188篇 |
2020年 | 153篇 |
2019年 | 161篇 |
2018年 | 194篇 |
2017年 | 187篇 |
2016年 | 248篇 |
2015年 | 295篇 |
2014年 | 362篇 |
2013年 | 403篇 |
2012年 | 425篇 |
2011年 | 343篇 |
2010年 | 230篇 |
2009年 | 215篇 |
2008年 | 285篇 |
2007年 | 236篇 |
2006年 | 226篇 |
2005年 | 187篇 |
2004年 | 175篇 |
2003年 | 121篇 |
2002年 | 137篇 |
2001年 | 103篇 |
2000年 | 96篇 |
1999年 | 82篇 |
1998年 | 46篇 |
1997年 | 29篇 |
1996年 | 22篇 |
1995年 | 39篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 33篇 |
1991年 | 20篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 33篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1979年 | 9篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1968年 | 7篇 |
排序方式: 共有5684条查询结果,搜索用时 109 毫秒
21.
Intramitochondrial Sr2+, similar to Ca2+, inhibits oxidative phosphorylation in intact rat-liver mitochondria. Both Ca2+ and Sr2+ also inhibit the hydrolytic activity of the ATPase in submitochondrial particles. Half-maximal inhibition of ATPase activity was attained at a concentration of 2.5 mM Ca2+ or 5.0 mM Sr2+ when the concentration of Mg2+ in the medium was 1.0 mM. The inhibition of ATPase activity by both cations was strongly decreased by increasing the Mg2+ concentration in the reaction medium. In addition, kinetical data and the determination of the concentration of MgATP, the substrate of the ATPase, in the presence of different concentrations of Ca2+ or Sr2+ strongly indicate that these cations inhibit ATP hydrolysis by competing with Mg2+ for the formation of MgATP. On the basis of a good agreement between these results with submitochondrial particles and the results of titrations of oxidative phosphorylation with carboxyatractyloside or oligomycin in mitochondria loaded with Sr2+ it can be concluded that intramitochondrial Ca2+ or Sr2+ inhibits oxidative phosphorylation in intact mitochondria by decreasing the availability of adenine nucleotides to both the ADP/ATP carrier and the ATP synthase. 相似文献
22.
For a period of three years, gelatin was used as a vehicle for administration of food, vitamin complex and drugs to laboratory maintained Callithrix penicillata and Callithrix jacchus marmosets and a breeding colony of C. penicillata. In both circumstances, results were satisfactory. The animals survived for long periods of time, with adult, young and juvenile primates in the breeding colony showing good physical condition. 相似文献
23.
An evolutive study of the "case-control" type was carried out in an endemic area of Chagas' disease in Minas Gerais State, Brazil, using two cross-section evaluations with an interval of ten years between them (1974-1984). Patients were paired for sex and age. In the first cross-section study 264 pairs one with a positive serology and the other with a negative serology for T. cruzi antibodies were included. In the second evaluation, ten years later, 235 patients among those with previous positive serology and 216 with negative serology were located, but only 110 pairs could be recomposed and reexamined (clinical examination, ECG and Rx of the heart and esophagus). The incidence of chagasic cardiopathy in the cases with positive serology but previously assymptomatic was 38.3% during the ten year period. On the other hand there was a deterioration in 24% of the patients with chagasic cardiopathy since the first examination. Considering all clinical forms of the disease in 34.5% of the patients the clinical situation deteriorated, in 57.3% there was no change and in 8.2% the situation improved. The general mortality in the period was 23% in the chagasic group and 10.6% in the control group, but the lethality by cardiopathy was 17% in chagasic group and only 23.3% in the control group. The mortality was twice as high in males than in females, mainly in the age group from 30 to 59 years. 相似文献
24.
25.
Localization and synthesis of an antigenic determinant of herpes simplex virus glycoprotein D that stimulates the production of neutralizing antibody. 总被引:54,自引:46,他引:8 下载免费PDF全文
G H Cohen B Dietzschold M Ponce de Leon D Long E Golub A Varrichio L Pereira R J Eisenberg 《Journal of virology》1984,49(1):102-108
An antigenic determinant capable of inducing type-common herpes simplex virus (HSV)-neutralizing antibodies has been located on glycoprotein D (gD) of HSV type 1 (HSV-1). A peptide of 16 amino acids corresponding to residues 8 to 23 of the mature glycoprotein (residues 33 to 48 of the predicted gD-1 sequence) was synthesized. This peptide reacted with an anti-gD monoclonal antibody (group VII) previously shown to neutralize the infectivity of HSV-1 and HSV-2. The peptide was also recognized by polyclonal antibodies prepared against purified gD-1 but was less reactive with anti-gD-2 sera. Sera from animals immunized with the synthetic peptide reacted with native gD and neutralized both HSV-1 and HSV-2. 相似文献
26.
Lusinete Aciole de Queiroz 《Mycopathologia》1974,54(4):559-564
A new species of the genusEndomycopsis is proposed. It was isolated from wast water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Quimica de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfeccio bamiento en el estudo de las levaduras. 相似文献
27.
The effect of the plating medium on the recovery of nonsense suppressors in Saccharomyces cerevisiae 总被引:2,自引:0,他引:2
Clara Queiroz 《Biochemical genetics》1973,8(1):85-100
The recovery of nonsense suppressors in a strain of Saccharomyces cerevisiae carrying five ochre mutations, tr, hi, ly, ar, and ad, is affected by the plating medium. The highest frequency is observed on tryptophanless medium, while the lowest is observed on adenineless medium. Experiments showed that exogenous histidine inhibits suppressor expression and that exogenous adenine relieves this inhibition. In histidine-independent strains, mutation expression requires adenine. A model, based on the role of RNA in supersuppression and on the biosynthetic pathways of histidine and adenine, is proposed to account for the observed data. It cannot, however, account for the high frequency of suppressors on tryptophanless medium. The tentative conclusion is drawn either that mis-reading of the tryptophan nonsense codon by mutated tRNA is facilitated by the neighboring bases or that the type of acceptable amino acid is less rigorously limited in the mutated site of the tryptophan locus than in those of the other suppressible loci.This work was in part supported by the Calouste Gulbenkian Foundation and by the Medical Research Council (Grant No. G969/24/B). 相似文献
28.
29.
H. M. Canelas F. B. De Jorge W. C. Pereira J. Sallum 《Journal of neurochemistry》1968,15(12):1455-1461
Abstract— Twenty-nine autopsy specimens of intracerebral tumours (nine astrocytomata, ten medulloblastomata and ten glioblastomata multiforme), as well as samples of peritumoral and apparently normal brain tissue, have been studied for Na, K, P, Ca, Mg, Cu, and S contents.
The tumour tissue, irrespective of the histological characteristics, as compared to the 'normal' and perineoplastic tissues, showed higher concentration of Ca, Mg, Cu and S. The peritumoral tissue, regardless of the tumour type, showed a higher concentration of Cu than the 'normal' control brain.
The more malignant glioblatomata and medulloblastomata. The Cu levels did not show a significant diference. 相似文献
The tumour tissue, irrespective of the histological characteristics, as compared to the 'normal' and perineoplastic tissues, showed higher concentration of Ca, Mg, Cu and S. The peritumoral tissue, regardless of the tumour type, showed a higher concentration of Cu than the 'normal' control brain.
The more malignant glioblatomata and medulloblastomata. The Cu levels did not show a significant diference. 相似文献
30.
Isolation of an internal component from adenovirus type 5 总被引:11,自引:0,他引:11