全文获取类型
收费全文 | 1598篇 |
免费 | 108篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 18篇 |
妇产科学 | 7篇 |
基础医学 | 192篇 |
口腔科学 | 21篇 |
临床医学 | 147篇 |
内科学 | 434篇 |
皮肤病学 | 345篇 |
神经病学 | 75篇 |
特种医学 | 43篇 |
外科学 | 161篇 |
综合类 | 4篇 |
预防医学 | 47篇 |
眼科学 | 13篇 |
药学 | 74篇 |
中国医学 | 1篇 |
肿瘤学 | 125篇 |
出版年
2023年 | 22篇 |
2022年 | 23篇 |
2021年 | 73篇 |
2020年 | 33篇 |
2019年 | 36篇 |
2018年 | 44篇 |
2017年 | 38篇 |
2016年 | 43篇 |
2015年 | 55篇 |
2014年 | 61篇 |
2013年 | 56篇 |
2012年 | 114篇 |
2011年 | 106篇 |
2010年 | 45篇 |
2009年 | 51篇 |
2008年 | 65篇 |
2007年 | 78篇 |
2006年 | 40篇 |
2005年 | 45篇 |
2004年 | 63篇 |
2003年 | 53篇 |
2002年 | 56篇 |
2001年 | 36篇 |
2000年 | 39篇 |
1999年 | 39篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 27篇 |
1989年 | 18篇 |
1988年 | 23篇 |
1987年 | 28篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有1708条查询结果,搜索用时 15 毫秒
1.
2.
Tissue distribution of epidermal growth-factor (EGF) in rat was investigated using a human EGF (hEGF) radioimmunoassay system. Antisera generated against hEGF reacted with hEGF and [21Leu] hEGF but not with mouse EGF, fibroblast growth factor (FGF), nerve growth factor (NGF), platelet derived growth factor (PDGF), and endothelial cell growth supplement (ECGS). Similar amounts of EGF immunoreactivity (EGF-IR) were found in the rat submandibular gland (32.8 +/- 4.59 ng/g tissue, n = 5) and duodenum (39.9 +/- 18.7 ng/g tissue, n = 9), whereas little EGF was detected in other tissues. No sex difference was observed in submandibular and duodenal EGF-IR, being different from the case of mouse in which ten times higher concentration of EGF-IR was found in male submandibular gland. Sephadex G-50 gel chromatography of submandibular and duodenal extracts revealed that each consisted of at least three different immunoreactive forms. The predominant EGF-IR was coeluted with 125I-EGF, significant amounts of EGF-IR was observed in the void volume fractions, and only small peaks of EGF-IR were present near Vt. These data clarified the presence of EGF-IR in rat submandibular and duodenal tissues and the molecular heterogeneity of EGF-IR and suggest some important role of EGF in the gastrointestinal function. 相似文献
3.
Decreased oxygen radical generation by neutrophils from patients with measles presumably owing to activation of suppressor T lymphocytes. 下载免费PDF全文
The capacity for the generation of oxygen radicals by polymorphonuclear leukocytes (PMNs) was assessed in 29 patients with measles and in control groups. Patients with secondary bacterial infections showed a significantly decreased generation of oxygen radicals; this abnormality did not persist for more than 2 months after disease onset. Normal PMNs incubated with T lymphocytes from these measles patients generated significantly fewer oxygen radicals than those incubated with T cells from either control group. However, normal PMNs incubated with non-T lymphocytes from these measles patients produced normal oxygen radical levels. In addition, irradiation above 1,500 rads of T lymphocytes abrogated the suppressive effect of T cells on PMNs. On the other hand, these abnormal findings were not observed in patients with measles but without secondary bacterial infections. The secondary bacterial infections sometimes seen in measles patients may result from a decrease in oxygen radical generation, presumably induced by the suppressive activity of the T lymphocytes of the patients. 相似文献
4.
The effect of coincident stimulation of convergent corticostriatal inputs was analyzed by the induction of immediate early genes in striatal neurons. Cortical motor areas were stimulated through implanted electrodes in awake, behaving rats, and the induction of the mRNAs encoding the immediate early genes (IEGs) c-fos and arc was analyzed in the striatum with in situ hybridization histochemistry. In the first experiment, unilateral stimulation of the medial agranular cortex, orofacial region of the lateral agranular cortex or the forelimb region of the lateral agranular cortex resulted in IEG induction in the striatum, which was restricted to the topographically related area receiving input from the stimulated cortical area. In a second experiment, stimulation parameters were altered, including frequency, number of pulses/train, and number of trains/s. These parameters did not have a significant effect on IEG induction. Notably, in some cases, in which there was IEG induction not only in the stimulated cortical region, but also in the homologous area in the contralateral hemisphere, very robust IEG induction was observed in the striatum. In a third experiment, the orofacial regions of the lateral agranular cortex of both hemispheres were stimulated coincidently. All of these animals showed robust striatal IEG induction. This IEG induction was attenuated by pretreatment with an NMDA antagonist MK-801. In a fourth experiment, we tested whether the coincidence of bilateral cortical stimulation contributed to the efficacy of striatal IEG induction. Either alternating stimulation or coincident stimulation of non-homologous cortical regions produced significantly lower striatal IEG induction than obtained with coincident stimulation of homologous cortical areas. Enhanced striatal IEG induction occurred in indirect striatal neurons, labeled with enkephalin, but was also present in a large number of enkephalin-negative neurons, most of which are likely direct pathway neurons. These results suggest that regional and temporal convergence of cortical inputs enhances striatal IEG induction. 相似文献
5.
6.
Blood supply to the retina and the lens in the gerbil (<Emphasis Type="Italic">Meriones unguiculatus</Emphasis>) 总被引:1,自引:0,他引:1
Imada H Isomura G Miyachi E 《Anatomical science international / Japanese Association of Anatomists》2003,78(1):36-41
The blood supply to the retina and the lens in 32 gerbils (Meriones unguiculatus) of both sexes from infancy to maturity was studied under light and stereoscopic microscopes, and a scanning electron microscope.
Mercox (CL-2R; Dai Nippon Ink, Tokyo, Japan) was injected into the left ventricle of 30 animals in order to visualize the
blood supply to the retina and the lens from the ophthalmic artery. The central retinal artery arises from the ophthalmic
artery, passes through the papilla of the optic nerve together with the central retinal vein and penetrates the vitreous space
(cavity of the eye) between the lens and the internal limiting membrane of the retina, where it divides into the central branches
covering the lens and the parietal branches to supply the retina. The former passes through the hyaloid space after branching
several arterioles and then covers the lens like a network from its medial and marginal sides. Different from small experimental
animals, the parietal branches, just after separating from the central one, divides into the nasal, dorsal and temporal branches
in the vitreous space, each of which then subdivides to distribute across the retina on the inner limiting membrane, then
delineates the membrana vasculosa retinae. This basal pattern of vasculization 1 day after birth continues to death. Both
the central and parietal branches of the central retinal artery correspond to the branches of the hyaloid artery in embryo
and the latter is preserved in adult gerbils. 相似文献
7.
Kazuo Nagashima Hisako Endo Koko Sakakibara Yumiko Konishi Ko Miyachi Jau Jinn Wey Yoshiyuki Suzuki Jinichi Onisawa 《Pathology international》1976,26(1):115-132
An autopsy case of a 19-year-old boy who had shown typical gargoyle features, strictly consistent with mucopolysaccharidosis type II (Hunter's syndrome) was reported. Histologically, cytoplasmic vacuolar change was found In hepatocytes, sinusoidal epithelium of spleen, follicular cells of thyroid, Sertoli cells of testis, chromophobe cell of pituitary and generalized fibroblast-like cells including meninges, cardiac valve and periosteum. The vacuoles consisting of membrane-bound structures with flocculus protein-like material and occasional electron dense bodies on electron microscopy, were considered to be the site of mucopolysaccharide deposition by histochemical analysis. Deposition of lipid material consistent with so-called membranous cytoplasmic body was observed in the neurons of central, peripheral and autonomic nervous system. Hepatosplenomegaly could be explained by cytoplasmic deposition, but the cause of cardiomegaly remained further to be studied. Biochemically hepatic mucopolysaccharide was identified as heparan sulfate, while in the kidney dermatan sulfate and heparan sulfate were detected. The correlation between morphology and biochemistry, and between deposition and degeneration was discussed. 相似文献
8.
We analyzed the RNA in platelets by fluorescence flow cytometry after staining with thiazole orange(TO) in whole blood samples from hematologically normal subjects and patients with thrombocytopenia. The percentage of TO-positive platelets and their mean fluorescence channel number in 32 control subjects were 6.2 +/- 2.5% (mean +/- SD) and 6.9 +/- 0.7, respectively. In 11 patients with idiopathic thrombocytopenic purpura, the percentage of fluorescently labeled platelets was significantly elevated (p less than 0.05) to 21.5 +/- 14.3%. By contrast, the proportion of positively stained platelets in 14 patients with thrombocytopenia due to impaired platelet production did not significantly differ from that of the controls, whereas the absolute counts of TO-positive platelets were significantly lowered (p less than 0.05). In both patient groups, the mean fluorescence channel numbers of TO-positive platelets were significantly elevated to 16.1 +/- 16.8 and 6.9 +/- 0.7, respectively (p less than 0.05, 0.005). We conclude that flow cytometric analysis of platelets after staining with TO provides information on the thrombopoietic activity in thrombocytopenic disorders. The main advantages of this method for clinical use are its simplicity and the rapidity. 相似文献
9.
Poly(vinyl alcohol) (PVA) was coated onto polyethylene (PE) films by a repetitive adsorption and drying process, and then the PVA-coated PE films were alternately immersed into aqueous solutions of Ca2+ and CO3(2-) ions (alternate soaking cycles), to deposit calcium carbonate (CaCO3) onto the films. The PVA coating was essential for the CaCO3 deposition. The amount of CaCO3 deposited increased with an increasing number of cycles. Scanning electron microscopic observations and attenuated total reflection spectra revealed the presence of both calcite and aragonite as the crystal structures of CaCO3 on the film. L929 fibroblast cells adhered and proliferated on these CaCO3-deposited PE films, as well as the hydroxyapatite-coated PE films previously prepared. It was found that the PVA coating and the subsequent deposition of calcium salts on certain films facilitated cell compatibility. 相似文献
10.
Rat peritoneal mast cells purified on a Percoll gradient were loaded with the fluorescent Ca2+ indicator fura-2 and were challenged with different concentrations of substance P (SP), and intracellular calcium concentrations ([Ca2+ ]i ) were measured by a spectrofluorometric assay. SP at 5 × 10−6 mol/1 and 10−5 mol/1 caused a significant histamine release with a significant increase in [Ca2+ ]i in a dose-dependent manner. However, SP at 10−8 -10−6 mol/1 did not induce either histamine release or increase in [Ca2+ ]i . Extracellular calcium at 0.9 mM inhibited the histamine release with a significant reduction of [Ca2+ ]i compared with that of the cells in a nominally calcium-free condition. These results indicate that the action of SP on rat mast cells relies upon [Ca2+ ]i to induce histamine release. 相似文献