全文获取类型
收费全文 | 229795篇 |
免费 | 22040篇 |
国内免费 | 15044篇 |
专业分类
耳鼻咽喉 | 2086篇 |
儿科学 | 2308篇 |
妇产科学 | 2851篇 |
基础医学 | 26572篇 |
口腔科学 | 3986篇 |
临床医学 | 29857篇 |
内科学 | 33002篇 |
皮肤病学 | 2548篇 |
神经病学 | 11719篇 |
特种医学 | 8351篇 |
外国民族医学 | 113篇 |
外科学 | 23804篇 |
综合类 | 39294篇 |
现状与发展 | 45篇 |
一般理论 | 28篇 |
预防医学 | 15942篇 |
眼科学 | 6128篇 |
药学 | 24929篇 |
249篇 | |
中国医学 | 14344篇 |
肿瘤学 | 18723篇 |
出版年
2024年 | 971篇 |
2023年 | 3775篇 |
2022年 | 9783篇 |
2021年 | 12363篇 |
2020年 | 9424篇 |
2019年 | 7899篇 |
2018年 | 8286篇 |
2017年 | 7646篇 |
2016年 | 7239篇 |
2015年 | 11033篇 |
2014年 | 13447篇 |
2013年 | 12599篇 |
2012年 | 18505篇 |
2011年 | 19734篇 |
2010年 | 13024篇 |
2009年 | 10103篇 |
2008年 | 12823篇 |
2007年 | 12234篇 |
2006年 | 11656篇 |
2005年 | 11091篇 |
2004年 | 7117篇 |
2003年 | 6420篇 |
2002年 | 5285篇 |
2001年 | 4411篇 |
2000年 | 4496篇 |
1999年 | 4572篇 |
1998年 | 2702篇 |
1997年 | 2743篇 |
1996年 | 2111篇 |
1995年 | 1997篇 |
1994年 | 1756篇 |
1993年 | 1055篇 |
1992年 | 1440篇 |
1991年 | 1257篇 |
1990年 | 1031篇 |
1989年 | 947篇 |
1988年 | 861篇 |
1987年 | 710篇 |
1986年 | 534篇 |
1985年 | 458篇 |
1984年 | 236篇 |
1983年 | 194篇 |
1982年 | 108篇 |
1981年 | 136篇 |
1980年 | 91篇 |
1979年 | 121篇 |
1978年 | 68篇 |
1977年 | 56篇 |
1976年 | 45篇 |
1974年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
P J Hayden C J Welsh Y Yang W H Schaefer A J Ward J L Stevens 《Chemical research in toxicology》1992,5(2):232-237
Nephrotoxic cysteine conjugates derived from a variety of halogenated alkenes are enzymatically activated via the beta-lyase pathway to yield reactive sulfur-containing metabolites which bind covalently to cellular macromolecules. Mitochondria contain beta-lyase enzymes and are primary targets for binding and toxicity. Previously, mitochondrial protein and/or DNA have been considered as molecular targets for cysteine conjugate metabolite binding. We now report that metabolites of nephrotoxic cysteine conjugates form covalent adducts with rat kidney mitochondrial phospholipids. Rat kidney mitochondria were incubated with the 35S-labeled conjugates S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFEC), S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC), S-(1,2-dichlorovinyl)-L-cysteine, and S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine. Quantitation of metabolite binding to whole mitochondria and to mitochondrial protein and lipid fractions revealed that as much as 42% of the 35S-label associated with the mitochondria was found in the lipid fraction. Total lipids were also extracted from 35S-treated mitochondria and separated by thin-layer chromatography. 35S-Containing metabolites were found in the lipid fractions from mitochondria treated with each of the conjugates. Lipids from both [35S]CTFC- and [35S]-TFEC-treated mitochondria contained major 35S-labeled lipid adducts which had similar mobility by thin-layer chromatography. Fatty acid analysis, 19F and 31P NMR spectroscopy, and mass spectrometric analyses confirmed that the major TFEC and CTFC adducts are thioamides of phosphatidylethanolamine. 相似文献
14.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight. 相似文献
15.
16.
OBJECTIVE: To understand the role of nasal mucous epithelial cells to hypoxia in early stage of nasal polyps(NP) formation. METHODS: Epithelial cells of NP and inferior turbinate (IT) were cultured without serum under normal oxygen and hypoxia, and stimulus of inflammatory cytokines. Erythropoietin (EPO) was regarded as hypoxia mark, and expression of vascular endothelial growth factor(VEGF) mRNA and protein derived from epithelial cells were detected respectively by in situ hybridization and ELISA. RESULTS: 1. Under hypoxia, EPO mRNA was expressed intensely in epithelial cells from NP and IT, and there was no significant difference between both of them. This result suggested that EPO might be regarded as a hypoxic mark. 2. The ability of producing VEGF mRNA increased with cytokines stimulation, especially under hypoxia. Protein level of VEGF from epithelial cells of NP and IT increased with cytokines stimulation, especially in hypoxia and was time-dependent. CONCLUSION: Epithelial cells actively produce vast VEGF under hypoxia. The VEGF induced by hypoxia of the mucosa in middle meatus is of importance in the formation of nasal polyps(NP) in early stage, which may be the major cause of NP formation in middle meatus. 相似文献
17.
本文报道了气管切开术各种并发症的发病率,并对术中或术后并发症的病的病因、发病机理、治疗和预防进行了讨论。 相似文献
18.
Georgios K Glantzounis Henryk J Salacinski Wenxuan Yang Brian R Davidson Alexander M Seifalian 《Liver transplantation》2005,11(9):1031-1047
Oxidative stress is an important factor in many pathological conditions such as inflammation, cancer, ageing and organ response to ischemia-reperfusion. Humans have developed a complex antioxidant system to eliminate or attenuate oxidative stress. Liver ischemia-reperfusion injury occurs in a number of clinical settings, including liver surgery, transplantation, and hemorrhagic shock with subsequent fluid resuscitation, leading to significant morbidity and mortality. It is characterized by significant oxidative stress but accompanied with depletion of endogenous antioxidants. This review has 2 aims: firstly, to highlight the clinical significance of liver ischemia-reperfusion injury, the underlying mechanisms and the main pathways by which the antioxidants function, and secondly, to describe the new developments that are ongoing in antioxidant therapy and to present the experimental and clinical evidence about the role of antioxidants in modulating hepatic ischemia-reperfusion injury. 相似文献
19.
眼针治疗阵发性室上性心动过速120例的即时疗效观察 总被引:2,自引:0,他引:2
目的:观察眼针对阵发性室上性心动过速的即时疗效。方法:选择符合诊断标准的门诊患者120例,针其眼针穴区:心区和上焦区。针后30分钟描记心电图,计算心率,观察眼针对阵发性室上性心动过速的影响。结果:显效103例,占85.83%;有效9例,占7.5%;无效8例,占6.66%;总有效率93.33%.结论:眼针对阵发性室上性心动过速有较好的即时疗效。 相似文献
20.
OBJECTIVES: To explore the morphological and functional findings of transvaginal sonography (TVS) in the diagnosis and management of distal ureteral calculi. METHODS: We retrospectively reviewed the imaging studies in seven cases of distal ureteral calculi (study group) and 20 cases of female volunteers without urinary tract infection (control group). All 27 patients had undergone TVS for assessment of the lower urinary tract. The variables measured on ultrasound included the presence or absence of distal ureteral calculi, the size and location of a calculus if present, the presence or absence of the ureter jet phenomenon, morphological changes of the ureteral papilla and adjoining tissue, and the height of the ureteral papilla, as well as vascular changes seen on Doppler imaging. RESULTS: In the controls, 80% of the ureteral papillae were triangular and 20% trapezoidal. The average (+/-SD) height of the ureteral papillae was 3.5 +/- 0.7 mm on the right and 3.6 +/- 0.9 mm on the left. There was no statistically significant difference between the heights of the right and left papillae (P = 0.619). In the study group, echogenic stones were identified in all seven patients and a hypoechogenic tubular structure connected to the involved papilla was identified in 6/7 patients. The average height of the involved papilla was 6.7 +/- 1.6 mm. Ureteric jets were visible in all patients in both the study and control groups. CONCLUSION: In patients with distal ureteral calculi, TVS provides a rapid, non-invasive and repeatable means of assessing the morphology and function of the distal ureter. 相似文献