全文获取类型
收费全文 | 1816篇 |
免费 | 118篇 |
出版年
2023年 | 11篇 |
2022年 | 28篇 |
2021年 | 46篇 |
2020年 | 20篇 |
2019年 | 35篇 |
2018年 | 44篇 |
2017年 | 33篇 |
2016年 | 48篇 |
2015年 | 79篇 |
2014年 | 95篇 |
2013年 | 107篇 |
2012年 | 118篇 |
2011年 | 124篇 |
2010年 | 73篇 |
2009年 | 79篇 |
2008年 | 98篇 |
2007年 | 91篇 |
2006年 | 82篇 |
2005年 | 64篇 |
2004年 | 71篇 |
2003年 | 62篇 |
2002年 | 57篇 |
2001年 | 24篇 |
2000年 | 26篇 |
1999年 | 26篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 21篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1971年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有1934条查询结果,搜索用时 359 毫秒
31.
Summary After subcutaneous administration of N,N-dimethyl-para-phenylenediamine (DPPD) in rats, a myogenic myopathy was produced in the skeletal muscles. In this communication, the results of the application of various histochemical techniques for the localization of oxidoreductases, transferases, hydrolases and isomerases and biochemical techniques for the estimation of activities of oxidoreductases in the experimental skeletal muscles are presented. The most striking result was the activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase which increased dramatically during the early phase of the muscle disease. The increase in activity of the pentose phosphate shunt enzymes was the first pathological alteration and was present as early as 8 h after a single injection of DPPD. Histochemical techniques for demonstration of activity of both enzymes are therefore highly suited for the detection of minor diseases and the early onset of major diseases of the neuromuscular system. Some glycolytic enzymes as well as some enzymes of the aerobic part of the metabolism showed an early decrease or increase in activity indicating a metabolic imbalance in the muscle fibres. There were more fibres with an intermediate pattern of the energy yielding enzymes in the experimental muscle specimens then in specimens from the control groups. The activity of the catabolic hydrolytic enzymes was strongly increased in pathological muscles. The aerobic muscles were more vulnerable to DPPD than the anaerobic muscles. 相似文献
32.
Alpha-ketoglutarate supply for amino Acid synthesis in higher plant chloroplasts: intrachloroplastic localization of NADP-specific isocitrate dehydrogenase 总被引:1,自引:0,他引:1 下载免费PDF全文
Isocitrate dehydrogenase was found in Pisum sativum chloroplasts purified on sucrose density gradients. A chloroplast-enriched pellet obtained by differential centrifugation formed two chlorophyll-containing bands. The lower one containing intact chloroplasts had NADP-specific isocitrate dehydrogenase and triose-phosphate isomerase activities. Mitochondria and peroxisomes were observed to band well away from the intact chloroplast region, as indicated by peak activities of fumarase and catalase, respectively. The presence of isocitrate dehydrogenase in chloroplasts suggests that chloroplasts may generate at least some of the α-ketoglutarate required for glutamate synthesis. 相似文献
33.
A previously unreported complication of pseudomeningocele following monoblock frontofacial advancement is described. The defect was repaired by means of an extracranial approach with a satisfactory outcome. 相似文献
34.
Crustacea Malacostraca were hitherto unknown from fresh waters of the Canary Islands. A new species of Amphipoda, Rhipidogammarus rheophilus, has recently been discovered in springs and spring brooks in Tenerife.
Resumen Crustacea Malacostraca era hasta ahora desconocida de las aguas dulces de las Islas Canarias. Una nueva especie de anfípodo, Rhipidogammarus rheophilus, ha sido recientemente descubierto de fuentes y manantiales de Tenerife.相似文献
35.
Summary Four siblings with the autosomal recessive Roberts syndrome are reported, and we discuss the phenotypic overlap of this syndrome with other similar radial, aplasia syndromes. 相似文献
36.
During myogenesis in vitro the actin-binding protein filamin is present in myoblasts and early fused cells and is associated with α-actinin-containing filament bundles, as judged by double immunofluorescence using antibodies specific for these two proteins. Approximately one day after cell fusion, yet before the development of a-actinin-containing Z line striations, filamin disappears from the cells. Later in myogenesis, several days after the appearance of α-actinin-containing Z line striations, filamin reappears and accumulates in the cells. Double immunofluorescence with antibodies to filamin and vimentin (or desmin) reveals that the newly appearing filamin localizes now to the myofibril Z line and is visible there shortly before vimentin or desmin becomes associated with the Z line. Immunofluorescent localization of filamin in isolated chicken skeletal myofibrils and Z disc sheets indicates that filamin has the same distribution as desmin and vimentin; it surrounds each myofibril Z disc and forms honeycomb-like networks within each Z plane of the muscle fiber. Filamin may thus be involved in the transition of desmin and vimentin to the Z disc. Analysis of whole-cell extracts by SDS-polyacrylamide gel electrophoresis and by immunoautoradiography shows that filamin is present in myoblasts and in myotubes early after cell fusion. Concomitant with the absence of filamin fluorescence during the subsequent few days of myogenesis, the quantity of filamin is markedly reduced. During this time, metabolic pulse-labeling with 35S-methionine reveals that the synthetic rate of filamin is also markedly reduced. As filamin fluorescence appears at the Z line, the quantity of filamin and its synthetic rate both increase. The removal of filamin from the cells suggests that filamin either may not be required, or may actually interfere with a necessary process, during the early stages of sarcomere morphogenesis. These results also indicate that the periphery of the Z disc is assembled in at least two distinct steps during myogenesis. 相似文献
37.
Myasthenia gravis is an autoimmune disease of man characterized by remitting and relapsing muscle fatigability. Although the etiology and pathogenesis are incompletely understood, the presence of circulating antibodies directed against the nicotinic acetylcholine (ACh) receptor in 80--90% of patients with myasthenia gravis and the identification of immune complexes at their neuromuscular junction have helped explain the altered neuromuscular transmission. The ACh receptor antibodies do not block access of ACh to the receptor, but do decrease the number of receptors by accelerating their degradation both in rat myotube cultures and in vivo models. In vitro these antibodies play a major role in myasthenia gravis. However, correlations of antibody titers with the clinical state following thymectomy or in neonatal myasthenia suggest that host factors may be equally important in determining whether the ACh receptor antibodies will result in clinical myasthenia. 相似文献
38.
39.
Alice O. Martin L. Miller J. L. Simpson C. Thomas M. S. Rzeszotarski S. Elias Gloria E. Sarto V. A. Patel 《Human genetics》1979,48(2):211-219
Summary A variant chromosome no. 21 consisting of two stalks and two satellites in tandem was detected during a survey of a human isolate. The variant segregated in three generations of a large kindred. One male had the variant no. 21, a metacentric Y, and a 47, XXY complement; however, no other evidence of chromosomal nondisjunction was found. Computer-aided analysis of sequentially stained variant no. 21 chromosomes indicated that silver-stained material corresponded to the proximal stalk region (as defined defined by Giemsa). These data support the hypothesis that human nucleolar organizers are localized to the stalks of acrocentric chromosomes. 相似文献
40.
Nectar glands are described for the first time on the developing fruits ofCrescentia cujete L. and their presence noted on fruits in 15 other genera of the Bignoniaceae. The nectaries are tiny, nonvascularized, patelliform structures of epidermal origin. They attract ants which are postulated to function in an antiherbivore role. 相似文献