全文获取类型
收费全文 | 1986342篇 |
免费 | 135590篇 |
国内免费 | 4653篇 |
专业分类
耳鼻咽喉 | 28276篇 |
儿科学 | 62453篇 |
妇产科学 | 54949篇 |
基础医学 | 282478篇 |
口腔科学 | 54395篇 |
临床医学 | 172586篇 |
内科学 | 386158篇 |
皮肤病学 | 44777篇 |
神经病学 | 153756篇 |
特种医学 | 80581篇 |
外国民族医学 | 535篇 |
外科学 | 303388篇 |
综合类 | 40012篇 |
现状与发展 | 6篇 |
一般理论 | 570篇 |
预防医学 | 140253篇 |
眼科学 | 46024篇 |
药学 | 152767篇 |
7篇 | |
中国医学 | 5756篇 |
肿瘤学 | 116858篇 |
出版年
2021年 | 17007篇 |
2019年 | 16449篇 |
2018年 | 22811篇 |
2017年 | 17785篇 |
2016年 | 20323篇 |
2015年 | 23664篇 |
2014年 | 32067篇 |
2013年 | 46390篇 |
2012年 | 63761篇 |
2011年 | 66645篇 |
2010年 | 39902篇 |
2009年 | 36921篇 |
2008年 | 60770篇 |
2007年 | 64094篇 |
2006年 | 64138篇 |
2005年 | 61761篇 |
2004年 | 58670篇 |
2003年 | 55997篇 |
2002年 | 53961篇 |
2001年 | 95982篇 |
2000年 | 98460篇 |
1999年 | 82900篇 |
1998年 | 22105篇 |
1997年 | 19674篇 |
1996年 | 19625篇 |
1995年 | 18250篇 |
1994年 | 16949篇 |
1993年 | 15967篇 |
1992年 | 62610篇 |
1991年 | 60068篇 |
1990年 | 58872篇 |
1989年 | 56645篇 |
1988年 | 51764篇 |
1987年 | 50588篇 |
1986年 | 47987篇 |
1985年 | 45463篇 |
1984年 | 33333篇 |
1983年 | 28203篇 |
1982年 | 16231篇 |
1979年 | 30241篇 |
1978年 | 20657篇 |
1977年 | 18174篇 |
1976年 | 16332篇 |
1975年 | 18265篇 |
1974年 | 21538篇 |
1973年 | 20680篇 |
1972年 | 19707篇 |
1971年 | 18309篇 |
1970年 | 17218篇 |
1969年 | 16433篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Michael K. Gardner Elaine Clark Mary Ann C. Bowman Patrick J. Miller 《Alcoholism, clinical and experimental research》1989,13(4):508-511
This study investigated analogical reasoning abilities of alcoholics who had been abstinent from alcohol for at least 1 year. Their performance was compared to that of nonalcoholic controls matched as a group for education, age, and gender. Solution times and error rates were modeled using a regression model. Results showed a nonsignificant trend for alcoholics to be faster, but more error prone, than controls. The same componential model applied to both groups, and fit them equally well. Although differences have been found in analogical reasoning ability between controls and alcoholics immediately following detoxification, we find no evidence of differences after extended periods of sobriety. 相似文献
992.
The in vitro ability of bacterial purified antigenic fractions to interfere with the immune system has been investigated on human mononuclear cells from peripheral blood. Exposure of purified monocytes to the drug at concentrations from 1 to 1000 micrograms/ml, for different periods from 0 to 18 h, significantly increased cell-mediated cytotoxicity against TU5 target cells. Moreover, monocytes exposed for 1 to 18 h to drug concentrations from 0.1 to 1000 micrograms/ml released significant amounts of tumor necrosis factor alpha in a dose-dependent manner in the culture supernatants. The drug was also tested on natural killer (NK) cell activity; mononuclear cells exposed to antigenic fractions for different periods showed a significant increase of NK cytotoxic activity against K562 target cells after 3 and 6, but not 0 and 18 h. Active concentrations were from 1 to 100 micrograms/ml, higher and lower doses being ineffective. Bacterial purified antigenic fractions thus have some ability to interfere in vitro with mechanisms of cytolysis mediated by cells and soluble factors. 相似文献
993.
Addison's disease is rarely caused by metastatic cancer. We report a unique case of hypoadrenalism owing to metastatic transitional cell carcinoma of the bladder. The relevant literature is reviewed. 相似文献
994.
995.
K Takeuchi O Furukawa H Tanaka H Nishiwaki S Okabe 《Japanese journal of pharmacology》1987,44(2):163-170
The effects of hemorrhagic shock (HE) on duodenal pH, acid-neutralizing capacity and mucosal tolerance to acid were investigated in anesthetized rats, and they were compared with those of indomethacin. HE was performed by bleeding from the carotid artery to reduce arterial blood pressure to about 55 mmHg (3 ml of bleeding per 200 g of body weight), and indomethacin was given s.c. in a dose of 5 mg/kg. Duodenal pH was determined in the outflow from the proximal duodenum (1.7 cm) which was perfused with 10(-4) M HCl, and acid-neutralizing capacity was measured by back-titration of the perfusate to pH 4.0 with 10 mM HCl. Under these conditions, duodenal pH was kept at around 6.0 as the result of neutralization in the loop (approximately 8 microEq/hr). Both HE and indomethacin significantly decreased the pH and acid-neutralizing capacity. Administration of 16,16-dimethyl prostaglandin E2 (16-dmPGE2: 30 micrograms/kg, s.c.) significantly increased both pH and acid-neutralizing capacity in normal and indomethacin-treated rats, but failed to affect these parameters in rats under HE conditions. When the duodenal loop was perfused with 50 mM HCl for 1.5 hr, both HE and indomethacin induced extensive damage in the mucosa. Pretreatment with 16-dmPGE2 significantly reduced the formation of duodenal lesions induced by indomethacin but not by HE. These results suggest that HE as well as indomethacin impaired duodenal acid-neutralizing capacity to reduce the tolerance to acid of the mucosa. The deleterious effects of HE on the mucosa may be mainly due to a decreased mucosal blood flow, but not due to a deficiency of endogenous prostaglandins. 相似文献
996.
In a previous study, we described a new method [3] to measure Na reabsorption by each segment of the human nephron independently. Reabsorption was expressed as equivalent volumes of solute-free water (CH2O) generated by the loop of Henle (CH2O-HL) and by the distal tubule (CH2O-DT), and dissipated by back diffusion (BD) across collecting ducts (CH2O-BD). These data were obtained during maximal water diuresis (MWD). The present study was undertaken to calculate CH2O-HL by experiments performed during maximal antidiuresis (MA). For this purpose, a new theoretical approach was devised, described by algebraic equations which allowed calculations of segmental transport during MA alone, where only CH2O-HL could be calculated independently. The study was performed on 14 normal volunteers who were studied twice by clearance measurements, firstly during MWD and again during MA. In each experiment, clearance periods were performed during baseline conditions and during the administration of furosemide (0.7 mg/kg bolus injection followed by 0.06 mg/kg/min maintenance infusion). From the values measured during either condition, segmental reabsorption was calculated. During MWD, CH2O-HL averaged 19.4 + 10.4, during MA 20.4 + 8.0 ml/min/GFR X 100; p greater than 0.05. The paired measurements were significantly correlated (r = 0.80; p less than 0.01). These data demonstrate that CH2O-HL obtained with the original theory is a reproducible result that can be confirmed with independent measurements obtained during different experimental conditions. Thus, measurements of segmental Na transport in the human nephron are feasible and can contribute important informations on disease states. 相似文献
997.
Uptake of iodine-123 MIBG by pheochromocytomas, paragangliomas, and neuroblastomas: a histopathological comparison 总被引:2,自引:0,他引:2
J Bomanji D A Levison W D Flatman T Horne P M Bouloux G Ross K E Britton G M Besser 《Journal of nuclear medicine》1987,28(6):973-978
The percentage uptake of [123I]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. Iodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001% and 0.14% of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of I-III. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements. 相似文献
998.
F Brown 《British medical journal》1987,295(6594):347-348
999.
(E)-5-(2-Bromovinyl)-2'-deoxyuridine (1; BrVUdR) inhibits the replication of herpes simplex virus type 1 (HSV-1) and of varicella-zoster virus (VZV) in vitro at concentrations of 0.01 to 0.23 mumol/l, whereas herpes simplex virus type 2 (HSV-2) is influenced only at 5.5 to 27 mumol/l. In comparison to some classical and newly developed antiherpetics, i. e. 5-iodo-2'-desoxyuridine (2; idoxuridine, IDU), 9-beta-D-arabinofuranosyladenine (4; vidarabine Ara-A), 9-(2-hydroxyethoxymethyl) guanine (5; acyclovir, ACV) and 2'-fluoro-5-iodo-1-beta-D-aracytosine (6;FIAC) the following order of decreasing activity was found:1 greater than 6 greater than 5 greater than 2 greater than 4 (against HSV-1) and 6 greater than 2 greater than 5 greater than 1 greater than 4 (against HSV-2). The high selectivity of the antiviral effect of BrVUdR towards HSV-1 and TZV is based on the fact, that proliferation of different mammalian cell lines is inhibited by 50% only at concentrations as high as 90 to 170 mumol/l, resulting in a therapeutical index of 1000 to 10,000. Successful treatment of an HSV-1 encephalitis in mice as well as an HSV-1 keratitis of rabbits confirmed the efficiency of 1 in experimental animal infections. No toxic side effects in both local and systemic applications were observed. Promising data from cell culture and animal experiments recommend 1 as a potential candidate for the local and systemic treatment of HSV-1 and VZV infections in man. 相似文献
1000.
K I Rusin 《Neirofiziologiia》1987,19(3):418-420
Isolated spinal cord neurons of 6-11 day old chick embryos were investigated under conditions of intracellular perfusion and voltage clamp. Glycine-activated chloride conductivity characteristics of neuronal membranes did not change at the investigated stages. Concentrations evoking half-effect (7.5 X 10(-5) mol/l) and Hill's coefficients (1.65-1.95) were also constant at these stages. 相似文献