全文获取类型
收费全文 | 3621篇 |
免费 | 219篇 |
国内免费 | 156篇 |
专业分类
耳鼻咽喉 | 38篇 |
儿科学 | 26篇 |
妇产科学 | 46篇 |
基础医学 | 810篇 |
口腔科学 | 161篇 |
临床医学 | 225篇 |
内科学 | 346篇 |
皮肤病学 | 71篇 |
神经病学 | 382篇 |
特种医学 | 71篇 |
外国民族医学 | 2篇 |
外科学 | 231篇 |
综合类 | 728篇 |
预防医学 | 114篇 |
眼科学 | 161篇 |
药学 | 235篇 |
1篇 | |
中国医学 | 84篇 |
肿瘤学 | 264篇 |
出版年
2024年 | 4篇 |
2023年 | 29篇 |
2022年 | 69篇 |
2021年 | 85篇 |
2020年 | 122篇 |
2019年 | 82篇 |
2018年 | 96篇 |
2017年 | 94篇 |
2016年 | 110篇 |
2015年 | 99篇 |
2014年 | 178篇 |
2013年 | 230篇 |
2012年 | 176篇 |
2011年 | 215篇 |
2010年 | 171篇 |
2009年 | 126篇 |
2008年 | 157篇 |
2007年 | 140篇 |
2006年 | 149篇 |
2005年 | 138篇 |
2004年 | 119篇 |
2003年 | 118篇 |
2002年 | 103篇 |
2001年 | 103篇 |
2000年 | 71篇 |
1999年 | 59篇 |
1998年 | 64篇 |
1997年 | 68篇 |
1996年 | 73篇 |
1995年 | 77篇 |
1994年 | 64篇 |
1993年 | 65篇 |
1992年 | 61篇 |
1991年 | 57篇 |
1990年 | 46篇 |
1989年 | 52篇 |
1988年 | 53篇 |
1987年 | 45篇 |
1986年 | 39篇 |
1985年 | 48篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 4篇 |
排序方式: 共有3996条查询结果,搜索用时 15 毫秒
1.
L Peichl 《The Journal of comparative neurology》1992,324(4):590-602
The morphological types of ganglion cells in the dog and wolf retina were studied by intracellular staining with Lucifer Yellow. These retinae contain a range of ganglion cell types that closely correspond to those found in cat retina: alpha cells with large somata and large, relatively densely branched dendritic trees; beta cells with medium-sized somata and small, densely branched dendritic trees; and a variety of other types with smaller somata and varying dendritic branching patterns and dendritic field sizes. The correspondence of canine and cat ganglion cell types strengthens the view that there is a common set of ganglion cell types in carnivores. Alpha and beta cell dendritic trees of dog and wolf are monostratified in either the inner or the outer part of the inner plexiform layer, suggesting an on/off dichotomy in the response to light. Dendritic field sizes of dog alpha and beta cells increase from the central area to peripheral retina: alpha cell fields from 160-200 microns to about 1,100 microns diameter, and beta cell fields from 25 microns to about 360 microns diameter. These sizes are quantitatively very similar to those found in cat retina. The close qualitative and quantitative morphological correspondence of cat and dog ganglion cells suggests that they are also functionally very similar. It is likely that dog alpha cells have brisk-transient (Y), and dog beta cells brisk-sustained (X) concentric receptive fields. From the smallest beta cell sizes it is concluded that the visual acuity of the dog may be as good as that of the cat. 相似文献
2.
3.
以健康Wistar大白鼠为材料,对微波快速内源性过氧化物酶染色与灌注法显示微血管的方法进行了对比研究。结果,过氧化物酶组织化学法具有不用灌注,操作简单,所用时间短,对血管无扩张、破裂等人为改变的特点,保持了微血管真实的自然形态和管径大小,可以定量或半定量地判定组织器官活体时的血液循环状况。可以用于人及动物的大脑、脊髓、皮肤、耳及食管等组织内微血管形态学研究和定量分析。并对过氧化物酶显示微血管的原理和微波辐射促进染色的原理及特点进行了分析、讨论。 相似文献
4.
研究了V235E、V235L、V411三个结肠肿瘤细胞株的细胞凋亡现象。DNA电泳分析和AO/EB荧光染色形态学检查表明,这三个肿瘤细胞株均存在自发性凋亡。提示肿瘤细胞,包括恶变的癌细胞仍可保留与增殖相对立的凋亡过程。肿瘤细胞存在自发性细胞凋亡的观察,有助于更好地认识肿瘤的发生和发展过程。此外,这些细胞株也为进一步研究细胞凋亡的诱导及其调控提供了有用的细胞模型。 相似文献
5.
H. Kanno T. Kuwabara M. Shinonaga C. C. Chang Y. Tanaka Y. Sugio H. Morita H. Yasumitsu M. Umeda Y. Nagashima 《Acta neuropathologica》1989,79(1):30-36
Summary A human glioma cell line (YKG1), which was positively identified for glial fibrillary acidic (GFA) and S-100 proteins, was established from a surgical specimen of a patient with glioblastoma. Chromosome analysis of the cells revealed a homogeneously staining region (HSR) on a marker chromosome. The assay for transforming growth factors (TGFs) in the conditioned medium of the cell line revealed that it contained high levels of - and -type TGFs, which might regulate the growth of glioblastoma and influence on the peritumoral tissues. 相似文献
6.
Enrique Hilario Emilia Rodeño Josu Simón Francisco J. Alvarez Salvador F. Aliño 《Virchows Archiv : an international journal of pathology》1992,421(6):485-490
Summary The growth and vascularization patterns of B16 melanoma colonies in the liver and lungs were measured and compared by histological techniques and dye diffusion patterns after injection of the fluorochrome Hoechst 33342. In the liver, the fluorescent pattern of dye diffusion revealed that uninodular tumours measuring up to 146 n in diameter were not functionally vascularized. However, when the nodules fused to give rise to multinodular tumours measuring between 256 and 366 n in diameter, a reticular dye diffusion pattern revealed functional tumour vascularization. In the lungs, subpleural, parenchymal and peritubular (i.e. surrounding blood vessels and airways) tumours were observed. The two former classes were vascularized down to thicknesses and diameters of 49 and 24 m respectively. In contrast, dye diffusion was never seen in peritubular tumour cuffs up to 609 m in thickness. The results indicate differences in vascularization patterns in B16 tumours in the liver and lungs, and differences between tumours growing in different sites within the lungs. If these results are applicable to metastases in these two organs, they indicate potential diffusion-mediated resistance to chemotherapy, and potential hypoxia-mediated resistance to radiotherapy of both metastases and micrometastases. 相似文献
7.
Enhanced polymer one-step staining (EPOS) is a novel, highly sensitive one-step immunostaining method. This simple and rapid technlque was applied to intra-operattve frozen diagnosis. The markers of choice were proliferating cell nuclear anmen (PCNA) and Ki-67 antigen. These cell prollferation markers were both identifiable in fresh frozen see tions of the human tonsil In approximately 7 min. The suitable staining sequences are as follows. Frozen sections prepared using 3-aminopropyitimethoxysilane-cpated glass slides are immediately fixed, without air drying, for 15s in a mixture of 50% formalin and 50% methanol for PCNA, and in 10% formalln for Ki-67 antigen. After a brief rinse in phosphate-buffered saline (PSS), sections are incubated with the EPOS antibody for 3 min, followed by PBS rinse for 1 min. The peroxidase activity is visualized in diaminobenzidine-H2 O2 solution containing 10mmol/L imidazole for 2 min. After a light rinse in tap water, the nuclei are briefly counterstained with 5% methyl green. When necessary, endogenous peroxi-dase blockage in 1% periodic acid solution for 1 min is added before the EPOS antibody incubation. This procedure is applicable to frozen sections of gastric cancers, malignant lymphomas, and brain, liver and peritoneal lesions in which differential diagnosis between benignancy and malignancy was required. 相似文献
8.
多种金属离子与单宁酸反应媒染微血管的对比研究 总被引:2,自引:0,他引:2
目的 镜下观察单宁酸与金属盐溶液中Ca2 + 、Au+ 、Ag+ 、Pb2 + 、Cu2 + 、Al3 + 、U6+ 、K+ 联用显示大脑微血管的效果。方法 用单宁酸媒染固定液灌流大鼠 ,取脑切片 ,入氯化钙、氯化金、硝酸银、硝酸铅、硫酸铜、硫酸铝钾、醋酸双氧铀、高锰酸钾和重铬酸钾等溶液中呈色。结果 单宁酸与Ca2 + 、Cu2 + 、Ag+ 、Al3 + 结合显示血管清晰 ,与Au+ 、U6+ 、Pb2 + 、K+ 联用媒染血管效果欠佳。结论 含Ca2 + 、Cu2 + 、Ag+ 、Al3 + 的金属盐类可替代氯化铁媒染微血管 ,氯化金、醋酸双氧铀、硝酸铅、重铬酸钾和高锰酸钾不宜与单宁酸联用来显示血管 相似文献
9.
It has been believed that the primary arterial trunk of the mammalian forelimb is derived from the 7th intersegmental artery.
Here we examined the early morphogenesis of the arteries and nerves in the forelimb region by adopting a method that combined
intravascular dye-injection with nerve staining to whole mounted rat embryos. The study was carried out on greater numbers
of specimens at smaller intervals of embryonic stages and from earlier stages than those in previous reports. We report that:
(1) The multiple primary arterial trunks in the forelimb region (primary subclavians) originate directly from the lateral
surface of the dorsal aorta independently of the intersegmental arteries, previous to the formation of limb buds. (2) The
tips of the 8th (and the 9th) primary subclavians that originate from the aorta near the origin of the 8th (or the 9th) intersegmental
artery bend cranially and/or caudally. With the formation of limb bud, they extend to form the longitudinal trunks in the
presumptive axillary region. The primary arteries in the free arm region branch off from this longitudinal trunk, and one
of them develops into the axial artery. (3) The origins of the primary subclavians shift their positions on the surface of
the dorsal aorta and approach the origins of the neighboring intersegmental arteries to join them, and then replace the latter.
Consequently, the primary subclavians appear to be ”the lateral branches of the in tersegmental arteries.” (4) The 8th primary
subclavian is dominant at first, but is replaced by the 7th primary subclavian, which develops into the definitive subclavian
artery. (5) With the brachial nerve plexus formation, the axillary arterial plexus derived from the longitudinal trunk develops
to form two stems of the axillary artery.
Accepted: 15 April 1999 相似文献
10.
Ernesto Falcidia Agata Grillo Piero Pavone Nunzio Cutuli Haruo Takabayashi Rosario R. Trifiletti Conrad T. Gilliam 《American journal of medical genetics. Part A》2001,101(3):262-267
The isolation and analysis of nucleated fetal cells (NFCs) from maternal blood may represent a new approach to noninvasive prenatal diagnosis. Although promising, these techniques require highly accurate separation of NFCs from nucleated cells of maternal origin; the two major problems limiting these techniques are the relative rarity of fetal cells in maternal blood and the need to establish their fetal origin. We now report a novel procedure that has allowed accurate separation of NFCs from maternal cells. The technique reported involves direct micromanipulator isolation of histochemically identified hemoglobin F‐positive nucleated cells to obtain fetal nucleated red blood cells (FNRBCs) of high yield and purity. Using this technique, followed by cell‐by‐cell multicolor fluorescence in situ hybridization (FISH) analysis of purified FNRBCs, we were able to detect some of the most common human aneuploidies (including Down syndrome, Klinefelter syndrome, and trisomy 13) in 33 pregnant women referred for amniocentesis. The procedure used, which can be completed in <72 hrs, produced complete concordance with the results of amniocentesis. We also confirm findings of prior studies suggesting that the number of FNRBCs in maternal circulation is remarkably higher in abnormal pregnancies than in normal pregnancies, especially in women carrying a fetus with trisomy 21. © 2001 Wiley‐Liss, Inc. 相似文献