全文获取类型
收费全文 | 3049篇 |
免费 | 61篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 73篇 |
儿科学 | 16篇 |
妇产科学 | 38篇 |
基础医学 | 1059篇 |
口腔科学 | 70篇 |
临床医学 | 102篇 |
内科学 | 327篇 |
皮肤病学 | 53篇 |
神经病学 | 417篇 |
特种医学 | 70篇 |
外科学 | 212篇 |
综合类 | 365篇 |
预防医学 | 78篇 |
眼科学 | 20篇 |
药学 | 111篇 |
中国医学 | 73篇 |
肿瘤学 | 72篇 |
出版年
2020年 | 12篇 |
2019年 | 14篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 23篇 |
2014年 | 46篇 |
2013年 | 112篇 |
2012年 | 48篇 |
2011年 | 80篇 |
2010年 | 76篇 |
2009年 | 59篇 |
2008年 | 100篇 |
2007年 | 92篇 |
2006年 | 105篇 |
2005年 | 99篇 |
2004年 | 92篇 |
2003年 | 127篇 |
2002年 | 87篇 |
2001年 | 123篇 |
2000年 | 94篇 |
1999年 | 97篇 |
1998年 | 78篇 |
1997年 | 98篇 |
1996年 | 107篇 |
1995年 | 104篇 |
1994年 | 96篇 |
1993年 | 83篇 |
1992年 | 94篇 |
1991年 | 79篇 |
1990年 | 77篇 |
1989年 | 68篇 |
1988年 | 74篇 |
1987年 | 77篇 |
1986年 | 48篇 |
1985年 | 70篇 |
1984年 | 46篇 |
1983年 | 14篇 |
1982年 | 50篇 |
1981年 | 62篇 |
1980年 | 62篇 |
1979年 | 49篇 |
1978年 | 40篇 |
1977年 | 38篇 |
1976年 | 26篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1973年 | 15篇 |
1972年 | 12篇 |
1971年 | 13篇 |
1970年 | 9篇 |
排序方式: 共有3156条查询结果,搜索用时 15 毫秒
1.
2.
P. Hyttel 《Anatomy and embryology》1987,176(1):41-44
Summary Cumulus-oocyte complexes were obtained from cows by aspiration of small (1–6 mm in diameter) antral follicles after slaughter. Complexes with a compact multilayered cumulus investment were cultured and processed for transmission electron microscopy after different periods of culture including a 0 h control group. In 0 h control oocytes the cumulus cells had numerous projections which penetrated the zona pellucida and established gap junctions with the oolemma. A partial loss of these junctions was noticed as an early event of oocyte maturation occurring within the first 3 h of culture. A low frequency of gap junctions was maintained until 12–18 h of culture where the junctional contact was completely disrupted. This decrease in intercellular communication was parallelled by resumption of oocyte meiosis. 相似文献
3.
作者用同位数前体参入法及透射与扫描电镜研究了平阳霉素(博莱霉素A_5)对HeLa细胞大分子生物合成及超微结构的影响。结果显示:平阳霉素能抑制HeLa细胞DNA,RNA和蛋白质的生物合成,对DNA的抑制作用强,ID_(50DNA)为42.77μg/ml。表现为:染色质减少,核内电子密度低,核仁分离及“核仁帽”形成,细胞表面微绒毛消失或变形,最终导致质膜破裂等。作者认为,细胞膜是否为此类药物作用的靶位值得进一步研究。 相似文献
4.
A case of ultrastructurally confirmed myoepithelioma of the breast studied by fine-needle aspiration biopsy is reported. Aspirated tumor cells were spindle-shaped with well-defined cytoplasm and oval nuclei showing no remarkable nuclear pleomorphism. They were seen mainly in irregular bundles with strong cellular cohesiveness. Their cytoplasm contained S-100 protein demonstrated by the peroxidase antiperoxidase staining technique. 相似文献
5.
采用模拟在人体中使用的实测超声剂量,对体外培养的L-929株细胞进行辐照,通过细胞回复能力试验,观察回复前后的细胞增殖与抑制。对体外培养的人胚肺纤维细胞经1次及5次辐照,观察了DNA及细胞核面积的影响。并通过电镜观察了细胞超微结构的变化。上述实验结果,均提示经辐照后细胞有增殖趋向 相似文献
6.
M. Villaplana A. García Ayala M. P. García Hernández B. Agulleiro 《Anatomy and embryology》1996,193(5):441-452
The cell organization of the pituitary gland and the relationship between neurohypophysis and adenohypophysis in the early developmental stages of the gilthead sea bream, Sparus aurata, were studied by electron microscopy. In newly hatched larvae, the pituitary gland was embedded in the ventral floor of the diencephalon and separated from the hypothalamus by a continuous basal lamina. Elongated mesenchymal cells next to the ventral surface were observed. At this stage, there was no neurohypophysis and the adenohypophysis consisted of undifferentiated endocrine cells with small scarce secretory granules and a few stellate cells, with no distinctive zonation. An incipient neurohypophysis was present in 1-day-old larvae. The first evagination of the neurohypophysis into the adenohypophysis were observed in 2-day-old larvae and developed progressively with age, being deeper in the caudal zone. Two regions in the adenohypophysis, one anterior — the presumptive pars distalis — and one posterior — the presumptive pars intermedia — were found in 2-day-old larvae. Three regions (rostral and proximal pars distalis and pars intermedia) were clearly distinguishable in 4-day-old larvae. The ultrastructural features of the pituitary endocrine cells varied during gland differentiation, with the secretory granules gradually increasing in number and size, accompanying organelle development. Nevertheless, even in the oldest larvae studied (65 days), undifferentiated cells similar to those in the earliest stages were observed. The first blood vessels appeared in the neurohypophysis around 16 days after hatching. During early development, the pituitary gland progressively emerged from the ventral floor of the brain. By 16 days, the principal pattern of the pituitary gland architecture appeared to be established. 相似文献
7.
8.
对离体不同时间血痕进行肉眼和扫描电镜观察,获得了血痕形态结构变化的初步认识.结果随时间延长,血痕逐渐干燥、龟裂,电镜下纤维蛋白网消失,其超微结构变化观察有助于血痕经过时间的推断. 相似文献
9.
Jos Meseguer Antonio Lpez-Ruiz Alfonsa Garcí-Ayala 《Anatomical record (Hoboken, N.J. : 2007)》1995,241(3):303-309
Background: Head-kidney, considered the major fish lympho-haemopoietic tissue, consists of cells of the different haemopoietic series supported by a network of stromal cells whose morphofunctional properties have not been established. We report the ultrastructure and cytochemical features of the reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.). Methods: Samples of head-kidney were processed for electron microscopic study. Some of the samples were incubated for acid and alkaline phosphatase, peroxidase, glucose-6-phosphatase, or ATPase. Results: The reticulo-endothelial stroma of gilthead seabream head-kidney consists of sinusoidal cells (endothelial and adventitial cells) and reticular cells (macrophage-type reticulum and fibroblast-like reticular cells). Transcytosis vesicles and rounded medium electron-dense granules were observed in the cytoplasm of the endothelial cells. The adventitial cells partially covered the outside surface of the endothelial cells and were joined by desmosomes. The macrophage-type reticulum cells were characterized by their cytoplasmic processes and acid phosphatase positive lysosomes. The fibroblast-like reticular cells were joined by desmosomes and formed an extensive network between the haemopoietic parenchyma. They were peroxidase negative and acid and alkaline phosphatase, glucose-6-phosphatase, β-glucuronidase, and ATPase positive. Conclusions: The ultrastructural and cytochemical features of the reticulo-endothelial stroma of the gilthead seabream head-kidney are similar to those of mammalian bone marrow, suggesting phylogenetic analogies between both tissues. © 1995 Wiley-Liss, Inc. 相似文献
10.