全文获取类型
收费全文 | 86486篇 |
免费 | 2185篇 |
国内免费 | 50篇 |
出版年
2018年 | 1031篇 |
2017年 | 1180篇 |
2016年 | 2952篇 |
2015年 | 6383篇 |
2014年 | 5993篇 |
2013年 | 5740篇 |
2012年 | 4997篇 |
2011年 | 2206篇 |
2010年 | 2237篇 |
2009年 | 2163篇 |
2008年 | 723篇 |
2007年 | 649篇 |
2006年 | 664篇 |
2005年 | 6751篇 |
2004年 | 5412篇 |
2003年 | 3617篇 |
2002年 | 1167篇 |
2001年 | 1116篇 |
2000年 | 342篇 |
1999年 | 1484篇 |
1998年 | 336篇 |
1997年 | 176篇 |
1992年 | 1922篇 |
1991年 | 2019篇 |
1990年 | 2074篇 |
1989年 | 2000篇 |
1988年 | 1952篇 |
1987年 | 1814篇 |
1986年 | 1624篇 |
1985年 | 1657篇 |
1984年 | 1088篇 |
1983年 | 836篇 |
1982年 | 462篇 |
1981年 | 422篇 |
1980年 | 370篇 |
1979年 | 1074篇 |
1978年 | 761篇 |
1977年 | 609篇 |
1976年 | 631篇 |
1975年 | 873篇 |
1974年 | 995篇 |
1973年 | 1006篇 |
1972年 | 953篇 |
1971年 | 928篇 |
1970年 | 820篇 |
1969年 | 830篇 |
1968年 | 735篇 |
1967年 | 751篇 |
1966年 | 584篇 |
1965年 | 432篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
831.
The method of two-dimensional electrophoresis was used to study protein biosynthesis in cytoplasm, nuclei and nuclear matrix of mouse thymocytes 15-75 min after exposure to ionizing radiation and hydrocortisone. Irradiation was shown to inhibit some cytoplasm proteins and to induce synthesis of a few polypeptides within the total nuclear proteins and nuclear matrix. Hydrocortisone promotes synthesis of some new proteins in all the fractions leading to the formation of new polypeptides. At least one common peptide is found within the total nuclear proteins and nuclear matrix after the effect of both factors. 相似文献
832.
Endocytosis of the epidermal growth factor (EGF) was investigated in three cell lines--A431, 3T6 and Swiss 3T3--after their incubation with cytochalasin B (CB). CB was introduced into culture medium (10 mkg/ml) 1.5-2 hours before addition of 125I-EGF (20-40 ng/ml). The label uptake rate was measured after a 35-40 minutes incubation of cells with 125I-EGF. It appeared that disorganization of microfilamentous network caused by CB exerted no influence on the binding of EGF to the surface membrane receptors and its internalization. Nevertheless, the experiments performed on A431 cells using a fluorescent label--rhodamine--bound to EGF (EGF-R) indicate that CB, though not influencing the initial steps of endocytosis, inhibits the next step--the intracellular transport of EGF-receptor complexes from the trans-Golgi region to lysosomes. As was shown elsewhere (Barkan, Nikol'sky, 1986), CB inhibits the mitogenic effect of EGF on resting Swiss 3T3 cells. So, the process of EGF-receptor uptake and delivery to the trans-Golgi region is evidently not enough to stimulate the cell proliferation; next steps of transport and degradation of ligand-receptor complexes are presumably needed. 相似文献
833.
I E Gurski? Ts V Serbeniuk P Ia Romanovski? 《Zhurnal evoliutsionno? biokhimii i fiziologii》1988,24(4):545-550
It has been shown that thyroliberin and its synthetic analogue PR-546 injected into the lymphatic sacs (4.10(-7)-4.10(-9) g/kg) or applied to the medulla oblongata in the bulbar frogs (4.10(-10)-4.10(-12) g/kg) significantly increase the rate of motor respiratory volleys in the hypoglossal nerve. In preparations with the irregular level of the activity of the respiratory center, these drugs enhanced stabilization of the initial level of the rhythm of motor respiratory discharges. 相似文献
834.
V V Snitinski? 《Zhurnal evoliutsionno? biokhimii i fiziologii》1988,24(5):702-707
Studies have ben been made on the activity of hexokinase, glucokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, as well as NADP-dependent dehydrogenases (malate and citrate) in the liver of foetuses and newborn piglets in relation to their age, fasting and reaction to injection of adaptive hormones (insulin and cortisol). It was shown that postpartum adaptation of carbohydrate metabolism in porcine liver is associated with activation of the glycolysis and with the increase in the activity of NADPH-generating dehydrogenases. In fasting newborn piglets the rate of carbohydrate catabolism increases. The effects of the investigated factors are different in the liver of 1-day piglets (sensitive to fasting) and 5-day animals (less sensitive). In is suggested that low ability of newborn piglets to maintain physiological level of glucose in the blood is associated with active glycolysis in the liver and ineffectiveness of the hormone-substrate mechanisms which control tissue glycaemia. 相似文献
835.
V G Nare?ko 《Ontogenez》1988,19(6):601-605
Changes in the myosin isozyme spectrum were studied in the loach developing skeletal muscle. It was shown using disk-electrophoresis in polyacrylamide gel and peptide mapping that light and heavy myosin chains from the larval muscles, as well as from the red and white muscle of adult fish differ from each other. Forms of myosin light and heavy chains were found which were characteristic of the larval muscle only. 相似文献
836.
The cell cycle structure in the cells of loach embryos at the early blastula stage (5 h of development at 21 degrees) is markedly altered under the influence of injection of homologous low molecular weight nuclear RNA and, as a result, the number of cells in G2-phase. The DNA amount in the embryo increases by 20%. At the midblastula stage (7 h) no increase in the number of cells in G2-phase was found. 相似文献
837.
T I Buzhievskaia T L Cha?kovskaia G V Skiban T E Zerova-Liubimova T P Kochube? 《T?Sitologii?a i genetika》1988,22(3):25-29
Three unusual cases of Down's syndrome inheritance are presented which permit supposing that microstructural chromosome aberrations in parents may induce not only a structural imbalance of chromosomal material in progeny, but also a numerical imbalance. 相似文献
838.
A G Maksina B A Da?niak I V Rakhmanova 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1988,(11):61-64
The structural changes in cat brain membranes under the injections of intramuscular streptomycin which is ototoxic antibiotic have been studied. The increase of membrane microviscosity in brain areas which are the direct projection of the auditory way has been revealed using fat acidic spin probe on the basis of stearic acid. The changes in membranes of other brain areas have not been found that exhibits a specific streptomycin influence on the auditory analyzer. The EPR spectra of the hydrocarbon spin label C12H25 localizing in near membrane region don't change in brain membranes of experimental animals compared with the normal ones. 相似文献
839.
T Gomez R Rial A Bola?os M Molina 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1988,90(1):203-205
1. Lizards Gallotia galloti received daily 3 mg/kg body wt of diphenylhidantoin (DPH) over a period of 15 days and at the same time the animals were kindled. 2. The progression of the kindling effect was evaluated by counting the number of spontaneous epileptiform potentials, the duration of afterdischarges and the duration of electroencephalographic spontaneous seizures. 3. The diphenylhidantoin treated group, relative to controls presented: (a) significant reduction in the duration of afterdischarges and spontaneous electroencephalographic seizures; and (b) increased frequency of the spontaneous epileptiform potentials. 相似文献
840.