全文获取类型
收费全文 | 3705篇 |
免费 | 284篇 |
国内免费 | 207篇 |
出版年
2023年 | 72篇 |
2022年 | 119篇 |
2021年 | 91篇 |
2020年 | 86篇 |
2019年 | 109篇 |
2018年 | 130篇 |
2017年 | 108篇 |
2016年 | 89篇 |
2015年 | 94篇 |
2014年 | 257篇 |
2013年 | 280篇 |
2012年 | 185篇 |
2011年 | 233篇 |
2010年 | 174篇 |
2009年 | 194篇 |
2008年 | 202篇 |
2007年 | 242篇 |
2006年 | 155篇 |
2005年 | 127篇 |
2004年 | 91篇 |
2003年 | 77篇 |
2002年 | 46篇 |
2001年 | 30篇 |
2000年 | 43篇 |
1999年 | 52篇 |
1998年 | 42篇 |
1997年 | 41篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 37篇 |
1993年 | 53篇 |
1992年 | 42篇 |
1991年 | 33篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 24篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 34篇 |
1984年 | 50篇 |
1983年 | 41篇 |
1982年 | 46篇 |
1981年 | 35篇 |
1980年 | 48篇 |
1979年 | 42篇 |
1978年 | 26篇 |
1977年 | 26篇 |
1976年 | 17篇 |
1974年 | 22篇 |
1973年 | 20篇 |
排序方式: 共有4196条查询结果,搜索用时 15 毫秒
131.
We have shown that tellurite and tellurate require the interaction with reduced glutathione (GSH) to hemolyze human erythrocytes.
The study of the nature of this interaction is the main object of this paper. The degree of hemolysis was determined by the
method of Angelone. The addition of extracellular 1 mM GSH or cysteine increased the rate of hemolysis. Concanavalin A (0.3
mg/mL) and/or 4 mg/mL adenosine did not affect the hemolysis by 0.1 mM tellurite. One tenth to 1 mM 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonate
(SITS) inhibited this hemolysis by 60–100%. Millimolar GSH released this inhibition. Incubation of 0.1 mM tellurite with 1
mM GSH for 90 min at 37°C, produced a hemolytic agent when prepared and tested under nitrogen, but one that was not active
when prepared in air. The hemolysis byp-hydroxymercuribenzoate orp-hydroxymercuriphenylsulfonate did not involve GSH. Scanning electron micrographs showed a sphero-echinocyte transformation,
in the pre-hemolytic stage, with all the agents tested. The rate of penetration of tellurite plays a role in determining the
rate of hemolysis, as shown by the effect of SITS. The release by GSH of the inhibition by SITS poses questions concerning
the site of action and cell membrane penetration of the hemolytic agent. Telluride or some intermediate in the interaction
of GSH with tellurite is the actual hemolytic agent. 相似文献
132.
Ebbe Thue Poulsen 《Journal of mathematical biology》1979,8(4):325-343
The life-cycle of a species with separate generations is divided into a reproduction phase and a growing-up phase. In the reproduction phase we assume random mating and selection due to genotype differences in fecundity of the parents and viability of the offspring. During the growing-up phase we assume a (deterministic) death process in continuous time with death rates for the genotypes which increase linearly with the genotype population sizes.In the absence of genotype differences the model gives logistic population regulation. With genotype differences the model generalizes the usual separate generations selection patterns. In addition to these we exhibit cases with three polymorphic equilibria or with a stable cycle. 相似文献
133.
Electrophoretic light scattering (laser Doppler electrophoresis) has been employed to study the effects of guinea pig IgG
immune complexes on the electrophoretic mobility distributions of guinea pig resident peritoneal cells. The resident population
of cells is composed of macrophages (approximately 75%) and eosinophils (approximately 25%). These cells were separated according
to the well-established method of Boyum. Populations of resident macrophages, eosinophils, and the unfractionated samples
were incubated with soluble immune complexes, antigen alone, or antibody alone. The mean mobility of the resident macrophages
decreased approximately 60% when incubated in the presence of immune complexes, although no effect could be discerned in the
presence of antigen or antibody alone. The width of the resulting macrophage mobility distribution was larger than that of
the control distributions, with a broad shoulder on the high-mobility side, indicating a heterogeneous response of the macrophages
to the immune complexes. Eosinophils react in two distinct fashions. One population of eosinophils is present near the control
experiments. The second population reacts in a manner very similar to that of macrophages. This suggest that at least two
populations of eosinophils are present in the unstimulated guinea pig peritoneal cavity. Results that are intermediate between
these two cases are found when unfractionated samples are studied. 相似文献
134.
Peter Adamietz Reinhard Bredehorst Helmuth Hilz 《Biochemical and biophysical research communications》1978,81(4):1377-1383
(3H)poly(ADP-ribose) synthesized from nuclei by incubation with (3H)NAD was released from protein by alkaline treatment and electrophoresed in dodecyl sulfate gels. Individual polymers up to at least 33 units were completely separated according to their chain length. Size distribution was visualized by fluorography of the gels, and quantified by radioactivity determination of sliced gels The method could be applied to crude nuclear extracts. It showed that nuclei of Ehrlich ascites tumor cells produced a poly(ADP-ribose) pattern distinctly different from that of rat liver nuclei. 相似文献
135.
Cercariae of Schistosoma mansoni were treated with undecenyl-pseudothiourea. After centrifugation, they agglutinated into a mass. Resuspended in water, they remained immobilized. When injected sub-cutaneously into mice, they produced bisexual infections. The immobilizing drug effect, together with a reduced worm recovery rate, are time and concentration dependent. The cercariae become avirulent (99.8%) only when the flame cell is affected. Immobilizing and “cercaricidal” effects are not necessarily related properties; the latter can be determined only by in vivo tests of infectivity. No protection against reinfection was noticed in mice injected with immobilized cercariae of reduced virulence. The immobilized cercariae produced infections with a 0.7% worm recovery rate by percutaneous exposure, compared to 2.2% by subcutaneous injection. Normal cercariae produced infections with average recovery rates of 11.1% subcutaneously and 45% percutaneously. 相似文献
136.
R. Cardinaud F. Guillain A. Bluzat 《Biochemical and biophysical research communications》1976,68(3):867-874
Heavy meromyosin subfragment 1 was resolved by chromatography on DEAE-cellulose into two fractions characterized by the nature of the alkali light chains present. It was shown that even in an HMM-S1 preparation with an extensive fragmentation of the heavy chain a polyacrylamide gel electrophoresis analysis differentiates alkali light chains among the light fragmentation components. A non-fragmented HMM-S1 was obtained from a papain digest of myofibrils and the chromatographic analysis supplied further evidence of the separation of the two species of HMM-S1 present in rabbit white muscle myosin. 相似文献
137.
Summary A study was made of the morphology of the adenohypophysis in immature harp seals and the fine structure of cellular components of the pars tuberalis, pars intermedia and pars distalis was described.The pars intermedia composed 8–15% of the hypophysis and contained colloid filled vesicles similar to those found in the other mammalian species.The pars distalis cells were grouped into more or less well defined regions, thus facilitating the correlation of cellular identification from both light and electron micrographs. Five chromophilic cell types were tentatively identified, one acidophil (putative somatotroph), four basophils (3 putative gonadotrophs and one cell type with the characteristics of both corticotrophs and thyrotrophs) and non-granulated stellate cells. The absence of a positive prolactin cell identification was thought to be due to the immaturity of the seals used in the study.The mercury exposure experiment was supported by a contract grant from the Halifax Laboratory of Fisheries and Marine Service. Drs. Uthe and Freeman of that laboratory also carried out the methyl mercury analyses. We recognize the support in maintaining the seals provided by Mrs. C. Rae, Mrs. H. Pedersen, Mr. S. Tessaro and Dr. J. M. Terhune. We also wish to thank Mrs. L. Lin for her technical assistance. Further financial support was provided through operating and development grants. The paper is number 134 in the physiology of migration series 相似文献
138.
139.
140.
《Neurochemistry international》1995,26(6):635-641
Acetylcholine synthesis from radiolabelled glucose was monitored in cerebral cortex cells isolated from brains of suckling and adult rats. Acetylcholine synthesis was found much higher in suckling animals, both in the absence and presence of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) inhibitor, paraoxon. Together with choline (20 μM), carnitine was found to stimulate acetylcholine synthesis in a synergistic way in cortex cells from adult rats (18%). Choline, however, was incapable of reversing an inhibitory effect exerted by carnitine on acetylcholine synthesis in cortex cells from suckling animals. Distribution of carnitine derivatives was found significantly different in the cells from young and old animals, the content of acetylcarnitine decreased with age with a corresponding increase of free carnitine. The observed differences in carnitine effect on acetylcholine synthesis suggested that high acetylcarnitine in cells capable of β-oxidation might be correlated with the lower level of acetylcholine synthesis. 相似文献