首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10772篇
  免费   1177篇
  国内免费   33篇
耳鼻咽喉   173篇
儿科学   417篇
妇产科学   225篇
基础医学   1315篇
口腔科学   166篇
临床医学   1178篇
内科学   1972篇
皮肤病学   384篇
神经病学   1072篇
特种医学   543篇
外科学   1378篇
综合类   243篇
一般理论   5篇
预防医学   1512篇
眼科学   141篇
药学   695篇
中国医学   4篇
肿瘤学   559篇
  2023年   75篇
  2021年   110篇
  2020年   106篇
  2019年   128篇
  2018年   180篇
  2017年   156篇
  2016年   137篇
  2015年   165篇
  2014年   280篇
  2013年   402篇
  2012年   356篇
  2011年   408篇
  2010年   268篇
  2009年   275篇
  2008年   435篇
  2007年   547篇
  2006年   460篇
  2005年   399篇
  2004年   404篇
  2003年   372篇
  2002年   360篇
  2001年   360篇
  2000年   424篇
  1999年   343篇
  1998年   208篇
  1997年   179篇
  1996年   182篇
  1995年   159篇
  1994年   157篇
  1993年   143篇
  1992年   286篇
  1991年   230篇
  1990年   284篇
  1989年   247篇
  1988年   237篇
  1987年   223篇
  1986年   207篇
  1985年   233篇
  1984年   141篇
  1983年   102篇
  1982年   122篇
  1981年   99篇
  1980年   87篇
  1979年   122篇
  1978年   105篇
  1977年   91篇
  1976年   103篇
  1975年   89篇
  1974年   93篇
  1973年   93篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Recent evidence suggests that mast cell derived mediators other than histamine are likely to be involved in the pathogenesis of physical urticarias. Much of the work has been performed in idiopathic cold contact urticaria where the presence of neutrophil and eosinophil chemotactic factors, and platelet activating factor-like lipid substances have been previously demonstrated. Now, an increase in prostaglandin D2 measured by GC-MS has been demonstrated in venous blood draining the cold challenged area. This appeared a few minutes later than histamine, but then both substances paralleled the onset, development and subsidence of the urticarial reaction. There appeared to be no quantitative relationship between histamine and PGD2 release. A similar rise in histamine and PGD2 occurred on heat challenge of a subject with the rare localized form of heat urticaria. This rise of both substances was considerably reduced after combined treatment with induction of tolerance and oral indomethacin. The concentrations of PGD2 measured suggested that it plays an indirect role.  相似文献   
52.
A hyperechoic mass in the right upper quadrant of the abdomen was demonstrated in a fetus by antenatal ultrasonography (US) at 20 and 33 weeks' gestation. Postnatal US, myelography and computed tomography were performed preoperatively; the findings were judged consistent with neuroblastoma. Surgical excision and pathological examination revealed bronchopulmonary sequestration.  相似文献   
53.
The authors have previously reported that intracarotid infusion of 5 micrograms leukotriene C4 (LTC4) selectively increases blood-tumor barrier permeability in rat RG-2 tumors. In this study, rats harboring RG-2 tumors were given 15-minute intracarotid infusions of LTC4 at concentrations ranging from 0.5 microgram to 50.0 micrograms (seven rats in each dose group). Blood-tumor and blood-brain barrier permeability were determined by quantitative autoradiography using 14C aminoisobutyric acid. The transfer constant for permeability (Ki) within the tumors was increased twofold by LTC4 doses of 2.5, 5.0, and 50.0 micrograms compared to vehicle alone (90.00 +/- 21.14, 92.68 +/- 15.04, and 80.17 +/- 16.15 vs. 39.37 +/- 6.45 microliters/gm/min, respectively; mean +/- standard deviation; p less than 0.01). No significant change in Ki within the tumors was observed at the 0.5-microgram LTC4 dose. Blood-brain barrier permeability was selectively increased within the tumors. At no dose in this study did leukotrienes increase permeability within normal brain. To determine the duration of increased opening of the blood-tumor barrier by LTC4 administration, Ki was measured at 15, 30, and 60 minutes after termination of a 15-minute LTC4 infusion (seven rats at each time point). The mean Ki value was still high at 15 minutes (92.68 +/- 15.04 microliters/gm/min), but declined at 30 minutes (56.58 +/- 12.50 microliters/gm/min) and 60 minutes (55.40 +/- 8.10 microliters/gm/min) after the end of LTC4 infusion. Sulfidopeptide leukotrienes LTC4, LTD4, LTE4 and LTF4 were infused to compare their potency in opening the blood-tumor barrier. The mean leukotriene E4 was the most potent, increasing the permeability value 3 1/2-fold compared with vehicle alone (139.86 +/- 23.95 vs. 39.37 +/- 6.45 microliters/gm/min).  相似文献   
54.
N A Black  E Thompson    C F Sanderson 《Gut》1994,35(9):1301-1305
The impact of open cholecystectomy on patients' symptoms and health status and their level of satisfaction has been examined to provide a basis for comparison with newer rival treatments. A prospective cohort study using patient and surgeon completed questionnaires before and six weeks after surgery was carried out in 14 general hospitals in eight European countries. Five hundred and eighty three patients were recruited consecutively in 1990 to 1991. Information on their symptoms, general health status, activities of daily living, and satisfaction with their care were collected. After surgery 42.8% of patients reported that they were free of symptoms. Symptoms varied in their responsiveness to surgery--six weeks after surgery 89% of those who had complained of vomiting had improved, 81% of nausea, 69% of loss of appetite, 65% of abdominal pain, and 51% of flatulence. In contrast 28.1% of patients still suffered from flatulence and 23.5% continued to complain of abdominal pain. Most patients' (62.7%) general health improved, 28% were unchanged, and 9.3% were worse. After surgery most patients reported no restrictions in their normal social activities (75-90% depending on the activity) and most (89.5%) felt the results of their operation had been as expected or better than expected. Most patients undergoing open cholecystectomy reported an improvement in their symptoms, health status, and social functioning. This was reflected in their high level of satisfaction. Some patients, however, gained no benefit and a small proportion were worse than before surgery.  相似文献   
55.
The expression of sodium channel α-subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immunocytochemical methods with antibodies generated against conserved and subtype-specific sequences of the sodium channel. In adult rat spinal cord, astrocytes within the dorsal and ventral funiculi were immunolabelled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within these spinal cord white matter tracts were immunostained with antibody SP11-II, which recognizes sodium channel type II. Antibodies SP11-I and SP32-III, which are directed against subtype-specific sequences in sodium channel types I and III, respectively, did not label astrocytes in the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detectable labelling of cells within the optic nerve was observed with antibodies SP11-I, SP11-II, and SP32-III. These observations demonstrate that sodium channel II is expressed by astrocytes in spinal cord white matter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes.  相似文献   
56.
57.
58.
59.
Because of concern about psoralen-induced phototoxicity and photocarcinogenesis, we investigated the effects of dietary lipids in a mouse model in which 8-methoxypsoralen (8-MOP) and UVA (PUVA) therapy has been shown to be carcinogenic. SKH-Hr-1 hairless albino mice were fed diets containing either omega-3 or omega-6 fatty-acid sources (menhaden oil and corn oil, respectively). After 2 weeks on the diets, the mice were treated topically with 8-MOP and then exposed to UVA (5 J/cm2). Mice receiving the omega-3 fatty-acid source exhibited a marked decrease in inflammatory response and a more rapid repair, as expressed both grossly and microscopically. In support of the latter response, i.e. repair, ornithine decarboxylase activity was about 20% greater in animals receiving the omega-3 fatty-acid source. The effects of the dietary fatty acid sources on PUVA tumorigenesis were examined in long-term studies in which animals were treated topically with 0.01% 8-MOP thrice weekly after which they were exposed to UVA (1 J/cm2). These studies indicated that a dietary lipid rich in omega-3 fatty acid and known to exhibit anti-inflammatory properties can markedly ameliorate the course of PUVA toxicity but does not impede the course of PUVA tumorigenesis  相似文献   
60.
Autoimmune progesterone dermatitis is a rare condition, characterized by recurrent premenstrual exacerbations of a dermatosis, in which sensitivity to progesterone can be demonstrated. The sensitizing mechanism is unknown. The aim of this study was to test the hypothesis that cross-sensitivity between steroid groups could induce allergy to endogenous progesterone in these patients. 5 patients with autoimmune progesterone dermatitis and 1 with oestrogen-sensitive dermatitis have been patch tested with a corticosteroid series, conjugated oestrogen 1% in petrolatum (pet.), and 17-α-OH-progesterone 2% pet. There were no immediate or delayed reactions at 2 and 4 days to any steroid group. We have therefore been unable to demonstrate steroid cross-sensitivity, or a use for 17-α-OH-progesterone in the investigation of oestrogen - and progesterone-sensitive dermatoses.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号