全文获取类型
收费全文 | 31610篇 |
免费 | 2243篇 |
国内免费 | 116篇 |
专业分类
耳鼻咽喉 | 238篇 |
儿科学 | 1043篇 |
妇产科学 | 631篇 |
基础医学 | 4240篇 |
口腔科学 | 906篇 |
临床医学 | 3218篇 |
内科学 | 6060篇 |
皮肤病学 | 412篇 |
神经病学 | 3331篇 |
特种医学 | 1146篇 |
外国民族医学 | 6篇 |
外科学 | 4476篇 |
综合类 | 373篇 |
一般理论 | 51篇 |
预防医学 | 2464篇 |
眼科学 | 1121篇 |
药学 | 2284篇 |
中国医学 | 51篇 |
肿瘤学 | 1918篇 |
出版年
2022年 | 191篇 |
2021年 | 419篇 |
2020年 | 267篇 |
2019年 | 435篇 |
2018年 | 530篇 |
2017年 | 433篇 |
2016年 | 476篇 |
2015年 | 529篇 |
2014年 | 746篇 |
2013年 | 1254篇 |
2012年 | 1912篇 |
2011年 | 2095篇 |
2010年 | 1133篇 |
2009年 | 1091篇 |
2008年 | 2006篇 |
2007年 | 2288篇 |
2006年 | 2195篇 |
2005年 | 2238篇 |
2004年 | 2121篇 |
2003年 | 2108篇 |
2002年 | 2004篇 |
2001年 | 268篇 |
2000年 | 213篇 |
1999年 | 280篇 |
1998年 | 458篇 |
1997年 | 407篇 |
1996年 | 311篇 |
1995年 | 327篇 |
1994年 | 315篇 |
1993年 | 308篇 |
1992年 | 225篇 |
1991年 | 202篇 |
1990年 | 182篇 |
1989年 | 151篇 |
1988年 | 159篇 |
1987年 | 150篇 |
1986年 | 185篇 |
1985年 | 184篇 |
1984年 | 300篇 |
1983年 | 271篇 |
1982年 | 338篇 |
1981年 | 305篇 |
1980年 | 318篇 |
1979年 | 160篇 |
1978年 | 192篇 |
1977年 | 204篇 |
1976年 | 127篇 |
1975年 | 134篇 |
1974年 | 116篇 |
1973年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Andrew S. Fix Jeffrey W. Horn Lewis L. Truex Ronald A. Smith Ernesto Gomez 《Acta neuropathologica》1994,88(6):511-519
Cytoplasmic vacuoles appear in neurons of the posterior cingulate/retrosplenial cortex (PC/RS) of rats after treatment with N-methyl-d-aspartate (NMDA) receptor antagonists. Prominent dilatation of mitochondria and endoplasmic reticulum has been described within 2 h; however, the ultrastructural features of vacuole formation are unknown. To investigate this, the present study examined the PC/RS cortex of male rats (age 60–70 days) at 15, 30, 45, 60, 90, and 120 min after subcutaneous treatment with 1 mg/kg of the noncompetitive NMDA antagonist MK-801 (dizocilpine maleate, 5-methyl-10, 11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine). Subtle mitochondrial dilatation was identified in a few neurons as early as 15 min postdose (MPD). By 30 MPD, dilatation was more pronounced in mitochondria and also involved the endoplasmic reticulum and perinuclear space. Ribosomal disaggregation and degranulation were also evident by 30 MPD. At all subsequent time points, dilatation of mitochondria and endoplasmic reticulum progressed in severity. Although the relative involvement of mitochondria and endoplasmic reticulum varied, glia were not involved. These ultrastructural data suggest that after treatment with MK-801, mitochondrial dilatation precedes involvement of endoplasmic reticulum in vacuolization of susceptible PC/RS cortical neurons. The early mitochondrial effects identified in this study suggest an initial metabolic insult that rapidly progresses to affect endoplasmic reticulum and ribosomes. This strengthens the relationship between the ability of certain NMDA antagonists to induce energy perturbations and neuronal vacuoles in the same region of the rat cerebral cortex. 相似文献
92.
Ronald Ley 《Journal of behavior therapy and experimental psychiatry》1994,25(4):269-273
In 1993 Klein proposed a “false suffocation alarm” theory of panic attacks, claiming that many spontaneous panic attacks are due to a “suffocation monitor” in the brain erroneously signaling a lack of useful air, and triggering an evolved “suffocation alarm system”. He proposed that carbon dioxide acts as a panic stimulus because rising arterial CO2 suggests suffocation may be imminent. The present paper provides a critical analysis of Klein's theory and concludes that there is neither empirical evidence nor compelling argument to support the assumptions or the proposed neurological mechanism of a “suffocation alarm”, true or false, or a CO2 “suffocation monitor”. Data relevant to the role of breathing in the phenomenon of panic can be parsimoniously subsumed within the domain of dyspnea. 相似文献
93.
A membrane-coated fiber (MCF) array approach was developed for quantitative assessment of skin absorption from chemical mixtures, which was based on the similarity in the absorption mechanisms of the MCF membrane and the stratum corneum of the skin. A set of probe compounds were used to detect the relative molecular interaction strengths of chemicals with the vehicle and the membranes, which provided a linkage between the skin permeability (log k) and MCF partition coefficients (log KF). A predictive model was established via multiple linear regression analysis of the data matrix of experimentally measured log k value and log KFm values; log k=a0+a1 log KF1+a2 log KF2+...+an log KFm, where m is the number of diverse MCFs. Twenty-five probe compounds and three MCFs (polydimethylsiloxane for lipophilic, polyacrylate for polarizable, and CarboWax for polar interactions) were used to demonstrate the model development processes in the MCF array approach. The skin permeability of the probe compounds was measured with conventional diffusion cell experiments using dermatomed porcine skin. Three predictive models were established for skin permeability prediction from chemical mixtures in water, 50% ethanol, and 1% sodium lauryl sulfate (SLS) with R2 values of 93, 91, and 83, respectively. The log k and log KF values were considerably altered by the addition of ethanol or SLS into the dose vehicle; however, their correlations to skin permeability remained strong under various conditions. These results suggested that the experimentally based MCF array approach can be used to predict skin absorption from chemical mixtures in different vehicles or formulations. 相似文献
94.
Patricia Iozzo Amalia Gastaldelli Mikko J J?rvisalo Jan Kiss Ronald Borra Emma Buzzigoli Antti Viljanen G Naum Tapio Viljanen Vesa Oikonen Juhani Knuuti Timo Savunen Piero A Salvadori Ele Ferrannini Pirjo Nuutila 《Journal of nuclear medicine》2006,47(6):1016-1022
The glucose analog (18)F-FDG is commonly used to quantify regional glucose uptake in vivo. The aim of this study was to test whether the analysis of plasma (18)F-FDG kinetics could be used to estimate endogenous glucose production (EGP) and the total rate of appearance (Ra), total rate of disappearance (Rd), and the metabolic clearance rate (MCR) of glucose. METHODS: Fourteen pigs were coinjected with (18)F-FDG and 6,6-(2)H-glucose ((2)H-G) during fasting (n = 6) and during physiologic (1.0 mU.kg(-1).min(-1), n = 4) and supraphysiologic (5.0 mU.kg(-1).min(-1), n = 4) euglycemic hyperinsulinemia. Arterial plasma was sampled for 180 min to quantify the parameters for the 2 tracers. RESULTS: Fasting Rd((2))(H-G) and Rd(FDG) were 12.3 +/- 2.1 and 13.3 +/- 1.3 micromol.kg(-1).min(-1) (difference not statistically significant [NS]). M values were more than doubled between the 2 clamp studies (P < 0.0001). Rd((2))(H-G) and Rd(FDG) were dose-dependently higher during the hyperinsulinemic state (19.8 +/- 3.7 vs. 18.9 +/- 1.1 and 31.4 +/- 4.1 vs. 31.9 +/- 2.3 in 1.0 and 5.0 mU.kg(-1).min(-1) studies, respectively; difference between tracers NS) than during the fasting state, with a parallel suppression of EGP((2))(H-G) and EGP(FDG). Parameters estimated by (18)F-FDG and (2)H-G were equivalent in all groups; their agreement was confirmed by Bland-Altman examination. Total Rd(FDG) correlated with Rd((2))(H-G) (r = 0.74; P = 0.003), M (r = 0.92; P = 0.001), MCR((2))(H-G) (r = 0.52; P = 0.037), and EGP((2))(H-G) (r = -0.71; P = 0.004). EGP(FDG) correlated with EGP((2))(H-G) (r = 0.62; P = 0.018), Rd((2))(H-G) (r = -0.78; P = 0.001), and MCR((2))(H-G) (r = -0.67; P = 0.008). The (18)F-FDG mean transit time correlated inversely with the M and Rd values and positively with EGP. CONCLUSION: The glucose analog (18)F-FDG can be used in the simultaneous estimation of whole-body glucose turnover and production and regional (18)F-FDG PET measurements under both fasting and insulin-stimulated conditions. 相似文献
95.
96.
In vivo MRI of cancer cell fate at the single-cell level in a mouse model of breast cancer metastasis to the brain. 总被引:7,自引:0,他引:7
Chris Heyn John A Ronald Soha S Ramadan Jonatan A Snir Andrea M Barry Lisa T MacKenzie David J Mikulis Diane Palmieri Julie L Bronder Patricia S Steeg Toshiyuki Yoneda Ian C MacDonald Ann F Chambers Brian K Rutt Paula J Foster 《Magnetic resonance in medicine》2006,56(5):1001-1010
Metastasis (the spread of cancer from a primary tumor to secondary organs) is responsible for most cancer deaths. The ability to follow the fate of a population of tumor cells over time in an experimental animal would provide a powerful new way to monitor the metastatic process. Here we describe a magnetic resonance imaging (MRI) technique that permits the tracking of breast cancer cells in a mouse model of brain metastasis at the single-cell level. Cancer cells that were injected into the left ventricle of the mouse heart and then delivered to the brain were detectable on MR images. This allowed the visualization of the initial delivery and distribution of cells, as well as the growth of tumors from a subset of these cells within the whole intact brain volume. The ability to follow the metastatic process from the single-cell stage through metastatic growth, and to quantify and monitor the presence of solitary undivided cells will facilitate progress in understanding the mechanisms of brain metastasis and tumor dormancy, and the development of therapeutics to treat this disease. 相似文献
97.
This paper is based on a prospective survey covering 275,600 sight tests by optometrists in England and Wales. It analyses the age and sex distribution of 1402 referrals for suspected glaucoma and 456 confirmed cases of the disease. The proportion of sight tests which led to a confirmed case increased with age, for both sexes, to a maximum at approximately 70 years, and then tended to decline. Cases of glaucoma in people aged 36-51 years accounted for about a tenth of the total, which is more than is generally recognized. Wider adoption of routine tonometry for middle aged people would help to ensure that these cases are detected at an early stage. Confirmed cases of glaucoma in which raised intraocular pressure had not been given as a reason for referral, i.e. probable low tension glaucomas, increased from 5% of patients < 51 years old to 13% of patients > 75 years old. Glaucoma was found to be much more common in men. 相似文献
98.
99.
100.