全文获取类型
收费全文 | 235538篇 |
免费 | 18025篇 |
国内免费 | 5853篇 |
专业分类
耳鼻咽喉 | 2895篇 |
儿科学 | 4216篇 |
妇产科学 | 4334篇 |
基础医学 | 30586篇 |
口腔科学 | 4495篇 |
临床医学 | 24773篇 |
内科学 | 39838篇 |
皮肤病学 | 5150篇 |
神经病学 | 14878篇 |
特种医学 | 10805篇 |
外国民族医学 | 29篇 |
外科学 | 28704篇 |
综合类 | 18407篇 |
现状与发展 | 23篇 |
一般理论 | 90篇 |
预防医学 | 17080篇 |
眼科学 | 6062篇 |
药学 | 21884篇 |
112篇 | |
中国医学 | 7442篇 |
肿瘤学 | 17613篇 |
出版年
2024年 | 427篇 |
2023年 | 2087篇 |
2022年 | 5458篇 |
2021年 | 8319篇 |
2020年 | 5341篇 |
2019年 | 5762篇 |
2018年 | 6569篇 |
2017年 | 5709篇 |
2016年 | 6419篇 |
2015年 | 9004篇 |
2014年 | 11315篇 |
2013年 | 13076篇 |
2012年 | 19134篇 |
2011年 | 19218篇 |
2010年 | 12782篇 |
2009年 | 10666篇 |
2008年 | 14195篇 |
2007年 | 13940篇 |
2006年 | 12782篇 |
2005年 | 11718篇 |
2004年 | 9807篇 |
2003年 | 8735篇 |
2002年 | 7534篇 |
2001年 | 5981篇 |
2000年 | 5135篇 |
1999年 | 3956篇 |
1998年 | 1667篇 |
1997年 | 1369篇 |
1996年 | 1205篇 |
1995年 | 1064篇 |
1994年 | 915篇 |
1993年 | 764篇 |
1992年 | 1670篇 |
1991年 | 1659篇 |
1990年 | 1440篇 |
1989年 | 1321篇 |
1988年 | 1205篇 |
1987年 | 1080篇 |
1986年 | 1046篇 |
1985年 | 919篇 |
1984年 | 665篇 |
1983年 | 586篇 |
1982年 | 417篇 |
1981年 | 392篇 |
1980年 | 349篇 |
1979年 | 537篇 |
1978年 | 418篇 |
1977年 | 400篇 |
1976年 | 347篇 |
1974年 | 362篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
David W. Ingersoll George Bobotas Ching-Tse Lee Aaron Lukton 《Physiology & behavior》1982,29(5):789-793
The present study was designed to investigate the chemical properties of the aggression-promoting cues present in bladder urine of male mice. The results of the first experiment confirmed earlier work by demonstrating the presence of an aggression-promoting chemosignal in bladder urine. In Experiment 2, behavioral assays were separately performed on the organic and aqueous layers of bladder urine obtained by repeated dichloromethane extractions. Only the combined organic layers of the initial three extractions demonstrated behavioral activity. A fourth extraction showed no behavioral activity for both organic and aqueous layers. However, the findings of Experiment 3 showed that incubation of the aqueous layer from the third CH2Cl2 extraction in β-glucuronidase can free additional aggression-promoting cues into a subsequent CH2Cl2 extraction. It is concluded that two forms of the aggression-promoting chemosignal are present in bladder urine. One is lipophilic and behaviorally active, whereas the other is conjugated, possessing latent chemosignal properties. 相似文献
992.
Diabetes mellitus was produced in 9 lambs by giving alloxan monohydrate, 150 mg/kg, 24 h prior to study, and these were compared with 12 control animals. Responses to insulin, 20 U/kg, were studied in each. Measurements of LV dP/dtmax, coronary sinus flow (CF) and myocardial extraction and uptake of O2, glucose and fatty acids (NEFA) were made using a hemodynamically controlled preparation described previously (Am. J. Physiol. 244: 1381, 1973). Initial arterial glucose (G) averaged 328 mg/dl in the diabetics compared with 110 mg/dl in controls. G fell to 160 mg/dl 90 min after insulin in the diabetics, and to 25 mg/dl in the controls. Initial LV dP/dtmax values were identical in both groups and showed similar increases of about 800 mmHg/s 30 min after insulin (P less than 0.001). However, initial CF was lower and resistance higher in diabetics than controls. After insulin, CF increased 50% in controls but only 10% in diabetics. Because inotropic responsiveness and O2 metabolism were the same in both groups, altered coronary vascular smooth muscle reactivity in the diabetics may explain these findings. 相似文献
993.
Observer variability in the histopathological reporting of abnormal rectal biopsy specimens.
下载免费PDF全文
![点击此处可从《Journal of clinical pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A M Lessells J S Beck R A Burnett S R Howatson F D Lee K M McLaren S M Moss A J Robertson J G Simpson G D Smith et al. 《Journal of clinical pathology》1994,47(1):48-52
AIMS--To study the consistency of reporting of abnormal rectal biopsy specimens, especially in the differentiation of inflammatory bowel disease from other causes of abnormality. METHODS--Sixty rectal biopsy specimens were identified from patients presenting with bloody diarrhoea. These were then circulated to the 11 consultant pathologists in the study who filled in a proforma with a list of 12 diagnostic categories and 22 features. RESULTS--Forty one of the 60 cases were examples of inflammatory bowel disease. In 33 of these cases nine or more pathologists had made the diagnosis. Further categorisation into ulcerative colitis and Crohn''s disease showed better recognition of ulcerative colitis. In the 19 cases of non-inflammatory bowel disease recognition of pseudomembranous colitis and solitary rectal ulcer syndrome was good, but the results were poorer in the case of infective colitis. CONCLUSION--The findings suggest that a group of consultant pathologists can differentiate between inflammatory bowel disease and other causes of an abnormal rectal biopsy specimen and can also recognise pseudomembranous colitis and solitary rectal ulcer syndrome satisfactorily. 相似文献
994.
995.
Xanthii Fructus (XF) is an herb widely used in medicine for the treatment of a variety of inflammatory pathologies. In this study, using mouse peritoneal macrophages, we have examined whether XF affects nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin (IL)-12p40 production induced by interferon (IFN)-γ and lipopolysaccharide (LPS). XF inhibits IFN-γ and LPS-induced NO production in a dose dependent manner. The decrease in NO synthesis was reflected as a decreased amount of inducible NO synthase protein. Furthermore, we also found that XF inhibits pro-inflammatory cytokine TNF-α production. However, treatment of XF in peritoneal macrophages had no effect on IL-12p40 production. These findings suggest that XF may be used in controlling macrophages-mediated inflammatory diseases. 相似文献
996.
Despite a gradual decrease in prevalence, clonorchiasis is still prevalent in East Asia. A large and compelling body of evidence links clonorchiasis and cholangiocarcinoma, although the mechanisms involved are not completely understood. Clonorchiasis induces biliary epithelial hyperplasia and metaplasia, and this could facilitate at least one stage of the carcinogenesis, which is promoting effect. In areas of endemic infection, more clonorchiasis cases are now diagnosed incidentally during radiological examinations such as cholangiography, ultrasonography, and computed tomography. Radiological findings are regarded as pathognomonic for clonorchiasis since they reflect the unique pathological changes of this disorder. These radiological examinations currently play important roles in the diagnosis, staging, and decision-making process involved in the treatment of cholangiocarcinoma. The morphological features and radiological findings of clonorchiasis-associated cholangiocarcinoma are essentially combinations of the findings for the two diseases. The morphological features of clonorchiasis- associated cholangiocarcinoma, observed in radiological examinations, do not differ from those of the usual cholangiocarcinoma. In patients diagnosed with or suspected to have clonorchiasis, radiological findings should be carefully scrutinized for occult cholangiocarcinoma. 相似文献
997.
Localized in vivo proton magnetic resonance spectroscopy ((1)H-MRS) has been used to measure the metabolic status of the human brain in a non-invasive manner; thus, it is often called "a non-invasive biochemical assay". MRS is more sensitive than magnetic resonance imaging (MRI) in detecting ischemic damage by measuring the metabolic changes that occur prior to the anatomic changes. We report a patient who presented with innominate artery occlusion and symptoms of posterior circulation insufficiency and showed favorable metabolic changes by (1)H-MRS after revascularization. He showed no visible lesion in brain MRI, but in (1)H-MRS, decreased N-acetylaspartate (NAA) signal was noted in a resting state.After revascularization, both symptomatic improvement and recovery of NAA signal were observed. (1)H-MRS may provide valuable clinical information in diagnosis and management of cerebral hypoperfusion at a much earlier stage prior to the anatomic changes. 相似文献
998.
Conversion of leukotriene D4 to leukotriene E4 by a dipeptidase released from the specific granule of human polymorphonuclear leucocytes 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Leukotriene D4 (LTD4), the most active spasmogenic leukotriene constituent of the slow reacting substance of anaphylaxis was converted by suspended human polymorphonuclear leucocytes (PMNs) to a single, less polar metabolite which was not further catabolized. This product was identified as leukotriene E4 (LTE4) by its retention time during reverse phase-high performance liquid chromatography (RP-HPLC) and subsequent bioassay on the guinea-pig ileum. LTD4 with a retention time of 21 +/- 1.6 min (mean +/- SD) and a contractile activity of 5.0 +/- 0.4 u./pmol (mean +/- SD) was quantitatively converted extracellularly by PMNs to LTE4 with a retention time of 26 +/- 1.8 min and a contractile activity of 1.2 +/- 0.3 u./pmol. Subcellular fractionations of PMNs revealed the recovered LTD4-to-LTE4 converting activity, termed LTD4 dipeptidase, to be localized only in he granule fraction. There was a time- and calcium-dependent extracellular release of LTD4 dipeptidase in association with lysozyme (r = 0.97, n = 16, P less than 0.001), a constituent of both specific and azurophilic granules, in the absence of release of cytoplasmic lactate dehydrogenase (LDH) and of beta-glucuronidase from the azurophilic granule. Phorbol myristate acetate (PMA), which selectively induces secretion of specific granules, released lysozyme and the LTD4 dipeptidase in a constant dose-dependent manner from PMNs (r = 0.96, n = 8, P less than 0.001). Calcium ionophore A23187 at concentrations less than 10(-7) M stimulated the parallel secretion of LTD4 dipeptidase and lysozyme (r = 0.91, n = 9, P less than 0.005), dipeptidase and lysozyme (r = 0.91, n = 9, P less than 0.005), whereas higher concentrations resulted in secretion of beta-glucuronidase and additional lysozyme without further release of dipeptidase. Thus, human PMNs can convert LTD4 to LTE4, a less vasoactive and spasmogenic leukotriene, via the secretion of a dipeptidase associated with the specific granules. 相似文献
999.
Adult rats were exposed to 10 ppm or 500 ppm halothane 8 hr/day and 5 days/wk for 8 wk or 4 wk, respectively. In the liver from animals which were exposed to 10 ppm of halothane, the rough endoplasmic reticulum in some hepatocytes accumulated a floccular, electron-dense material which gave the hepatocytes a dense and dark appearance. Increase in the matrical density and C-shaped transformation were observed in the mitochondria of some hepatocytes. In addition to these findings, areas of focal cytoplasmic degradation, dilatation of the bile canaliculi, peribiliary accumulation of lysosomes, and extensive dilatation of the smooth endoplasmic reticulum to form large cytoplasmic vacuoles were also observed in the hepatocytes of animals which had been exposed to 500 ppm halothane. Toxic potential of halothane upon chronic exposure is suggested. 相似文献
1000.
Kim MS Lee J So HS Lee KM Jung BH Chung SY Moon SR Kim NS Ko CB Kim HJ Kim YK Park R 《Immunopharmacology and immunotoxicology》2001,23(1):55-66
Mistletoe lectin-II, a major composition of Korean mistletoe (Viscum album coloratum), is known as a potent apoptosis inducer. The previous research has demonstrated that Korean mistletoe lectin-II induces apoptosis via c-Jun N terminal kinase (JNK) activation in human myeloid U937 cells. The purpose of this research is to prove the synergistic action of mistletoe lectin-II and interferon-γ (IFN-γ) in the apoptotic cytotoxicity of U937. When U937 cells were treated with mistletoe lectin-II after being differentiated by IFN-γ, the proteolytic activity of caspase-3 and 9 was markedly elevated and that of caspase-8 was prolonged for 18 hr. The activation of caspase-3-like protease requires the earlier cleavage of poly(ADP-ribose) polymerase(PARP). Caspase-1 was, however, not activated during the resting phase and nor in IFN-γ-differentiated U937 cells. Western blot analysis revealed that, in IFN-γ-differentiated U937 cells, the expression of Fas (CD95/APO-1) & Fas ligand(FasL) increases the apoptotic sensitivity against Mistletoe lectin-II. Fas (CD95/APO-1) & FasL were not significantly induced solely by mistletoe lectin-II. Furthermore the activity of JNK1 in U937 cells was also markedly increased with IFN-γ-differentiation, compared to that of the control. These results suggest that the IFN-γ-differentiation of U937 cells increases the susceptibility to mistletoe lectin-II-induced apoptosis. 相似文献