全文获取类型
收费全文 | 142672篇 |
免费 | 14242篇 |
国内免费 | 9186篇 |
专业分类
耳鼻咽喉 | 1308篇 |
儿科学 | 2256篇 |
妇产科学 | 1459篇 |
基础医学 | 13755篇 |
口腔科学 | 2502篇 |
临床医学 | 19664篇 |
内科学 | 17662篇 |
皮肤病学 | 1535篇 |
神经病学 | 5558篇 |
特种医学 | 4494篇 |
外国民族医学 | 54篇 |
外科学 | 11492篇 |
综合类 | 29692篇 |
现状与发展 | 40篇 |
一般理论 | 18篇 |
预防医学 | 13254篇 |
眼科学 | 3662篇 |
药学 | 16573篇 |
221篇 | |
中国医学 | 10708篇 |
肿瘤学 | 10193篇 |
出版年
2024年 | 614篇 |
2023年 | 2213篇 |
2022年 | 5533篇 |
2021年 | 7227篇 |
2020年 | 5703篇 |
2019年 | 4434篇 |
2018年 | 4530篇 |
2017年 | 4631篇 |
2016年 | 4132篇 |
2015年 | 6563篇 |
2014年 | 8154篇 |
2013年 | 8260篇 |
2012年 | 11720篇 |
2011年 | 12600篇 |
2010年 | 9417篇 |
2009年 | 7880篇 |
2008年 | 8949篇 |
2007年 | 8709篇 |
2006年 | 8119篇 |
2005年 | 7106篇 |
2004年 | 5093篇 |
2003年 | 4608篇 |
2002年 | 3715篇 |
2001年 | 2980篇 |
2000年 | 2537篇 |
1999年 | 2172篇 |
1998年 | 1321篇 |
1997年 | 1258篇 |
1996年 | 960篇 |
1995年 | 929篇 |
1994年 | 821篇 |
1993年 | 480篇 |
1992年 | 474篇 |
1991年 | 438篇 |
1990年 | 385篇 |
1989年 | 327篇 |
1988年 | 271篇 |
1987年 | 250篇 |
1986年 | 171篇 |
1985年 | 146篇 |
1984年 | 82篇 |
1983年 | 42篇 |
1982年 | 30篇 |
1981年 | 40篇 |
1980年 | 13篇 |
1979年 | 25篇 |
1977年 | 7篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
51.
肺血管扩张在肝肺综合征发病机制中作用的研究进展 总被引:3,自引:0,他引:3
肺血管扩张是肝肺综合征的主要发病机制,然而导致HPS肺血管扩张的机制相当复杂,至今仍不清楚.目前认为肺血管内巨噬细胞聚积和雌激素升高导致的血管活性因子增多和活性增强可能与此有关,近年来这方面的研究很多,本文对此作一综述. 相似文献
52.
53.
OBJECTIVE: To study the expression of neuron-specific enolase (NSE) and olfactory marker protein (OMP) in the developing olfactory mucosa of human fetuses. METHOD: The expression of NSE and OMP in the olfactory mucosa of 6 human fetuses (12, 16, 20, 24, 28 and 34 weeks) was studied using the technique of immunohistochemistry. RESULTS: NSE immunological positive reactions were seen in all 6 fetal mucosa from gestational 12 (G12) to G34, with plenty of positive-stained dual-pole neuron cells. At G12, the positive cells aligned tightly, the cell bodies were localized in the lower portion of olfactory epithelium and the positive-stained area occupied upper 2/3 of fetal nasal mucosa. With the development, the positive cells gradually became multilayer, but the density and the relative area of positive-cells reduced. At G34, the positive cells were located only in upper 1/3 of nasal mucosa. OMP-positive reactions were localized in a few dual-pole neurons at G12, the number was much less than NSE-positive cells in the same fetus. With the development, the OMP-positive cells gradually increased with most of the cell bodies located in the upper portion of epithelium, but number still relatively less than the NSE-positive cells at the same age. CONCLUSION: At G12, there were lots of olfactory neuron in the olfactory mucosa and only a few olfactory neurons had became mature. With the development, the olfactory epithelial area reduced but the number of mature olfactory neurons increased. At the last trimester, fetal olfactory sensor was almost matured. 相似文献
54.
OBJECTIVE: To evaluate the possibility and reliability of the hyoid-sternohyoid graft transfer in the correction of server subglottic laryngotracheal stenosis, and delineate the operation skills and clinical results. METHODS: Seven patients with severe subglottic stenosis underwent laryngotracheal reconstruction using the hyoid grafts with sternohyoid muscle flaps (HG-SHMF). Five of these patients had traumatic subglottic stenosis, one with scar tissue of unknown etiology arising in the subglottic region, another with tracheal narrowing caused by inhalation of hydrochloric acid. RESULTS: All seven patients were successfully decannulated with moderate good voice. The average time from reconstruction to decannulation was 15.4 months. The stent was endoscopically removed with a range of 3 to 22 months; the mean time required for stenting was 9.6 months. Two patients who received additional salvage reconstruction procedures because of graft or stent displacement were extubated with improved voices and satisfactory airway. CONCLUSIONS: The HG-SHMF transfer was a single-stage reconstruction, relatively simple procedure that can restore an adequate airway and a good voice. Patients undergoing laryngotracheal reconstruction with HG-SHMF must have regular, long-term follow-up since graft displacement and recurrent granulation tissue or scar reformation can cause restenosis after an initially successful surgery. This procedure should be used in a large number of patients to further test its reliability. 相似文献
55.
Progressive multifocal leukoencephalopathy (PML) is a fetal demyelinating disease in the central nervous system. PML was once a rare disease, but it is now relatively common among AIDS (acquired immunodeficiency syndrome) patients. The immunological state of patients mainly contributes to the pathogenesis of PML. Genetic changes of the etiological agent, however, may also be involved in the development and progression of the disease. The major genetic changes possibly associated with PML include the regulatory region rearrangement and the VP1 loop mutation. Both changes have been identified as genetic changes usually occurring in JCV (JCvirus) DNAs from the brain and cerebrospinal fluid of PML patients. Although it remained to be clarified how these changes are involved in the pathogenesis of PML, accumulating evidence suggests that the VP1 loop mutation is associated with the progression of PML. Here we overview studies (mainly those performed by ourselves) on these genetic changes. 相似文献
56.
采用辣根过氧化物酶(HRP)逆行示踪与谷氨酸免疫细胞化学结合法对大鼠额叶和枕叶皮质内胼胝体神经元的化学性质进行了研究.结果发现含谷氨酸的胼胝体神经元为大中型锥体细胞,主要分布于皮质Ⅱ/Ⅲ、Ⅴ和Ⅵ层,并有成群分布的倾向.含谷氨酸的胼胝体神经元的数目约占 HRP 标记的胼胝体神经元的17%(额叶)和29%(枕叶).这一结果从形态学上证实,大鼠大脑皮质内相当一部分胼胝体神经元使用谷氨酸作为兴奋性递质。 相似文献
57.
Platelet-derived growth factor activates mitogen-activated protein kinase in isolated caveolae 下载免费PDF全文
Pingsheng Liu Yun-shu Ying Richard G. W. Anderson 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(25):13666-13670
The ability of a peptide hormone to affect many different intracellular targets is thought to be possible because of the modular organization of signal transducing molecules in the cell. Evidence for the presence of signaling modules in metazoan cells, however, is incomplete. Herein we show, with morphology and cell fractionation, that all the components of a mitogen-activated protein kinase pathway are concentrated in caveolae of unstimulated human fibroblasts. Addition of platelet-derived growth factor to either the intact cell or caveolae isolated from these cells stimulates tyrosine phosphorylation and activates mitogen-activated protein kinases in caveolae. The molecular machinery for kinase activation, therefore, is preorganized at the cell surface of quiescent cells. 相似文献
58.
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
59.
60.
In the present paper we report the mitogenic effect of the sheep anti-porcine lymphocyte E-receptor antiserum IgG(APERIgG) on porcine peripheral T-lymphocytes in vitro. The effect was apparently dose-dependent and not seen in the B-lymphocyte cultures. Kinetic study showed that the maximal 3H-thymidine incorporation, similar to that induced by Con A, occurred on the third day of incubation. Neither F(ab')2 nor Fab fragment of APERIgG was able to induce cell proliferation, indicating that the integrity of IgG molecule was essential for cell response. It was very interesting to note that though there is cross antigenicity between porcine and human E-receptors, no similar effect could be produced by APERIgG in human peripheral lymphocyte cultures under the same experimental conditions, suggesting the existence of minor difference in structure between the porcine and human E-receptors. 相似文献