全文获取类型
收费全文 | 187916篇 |
免费 | 2046篇 |
国内免费 | 57篇 |
专业分类
耳鼻咽喉 | 1364篇 |
儿科学 | 7015篇 |
妇产科学 | 3187篇 |
基础医学 | 17927篇 |
口腔科学 | 1786篇 |
临床医学 | 13665篇 |
内科学 | 33186篇 |
皮肤病学 | 837篇 |
神经病学 | 17969篇 |
特种医学 | 9333篇 |
外科学 | 30539篇 |
综合类 | 2685篇 |
一般理论 | 3篇 |
预防医学 | 19218篇 |
眼科学 | 2997篇 |
药学 | 10379篇 |
中国医学 | 640篇 |
肿瘤学 | 17289篇 |
出版年
2021年 | 193篇 |
2020年 | 155篇 |
2019年 | 225篇 |
2018年 | 22128篇 |
2017年 | 17509篇 |
2016年 | 19667篇 |
2015年 | 1107篇 |
2014年 | 1057篇 |
2013年 | 1239篇 |
2012年 | 7564篇 |
2011年 | 21636篇 |
2010年 | 19157篇 |
2009年 | 11825篇 |
2008年 | 20031篇 |
2007年 | 22354篇 |
2006年 | 1130篇 |
2005年 | 2812篇 |
2004年 | 4004篇 |
2003年 | 4928篇 |
2002年 | 3005篇 |
2001年 | 584篇 |
2000年 | 714篇 |
1999年 | 443篇 |
1998年 | 382篇 |
1997年 | 354篇 |
1996年 | 241篇 |
1995年 | 233篇 |
1994年 | 209篇 |
1993年 | 172篇 |
1992年 | 289篇 |
1991年 | 312篇 |
1990年 | 324篇 |
1989年 | 266篇 |
1988年 | 228篇 |
1987年 | 222篇 |
1986年 | 193篇 |
1985年 | 210篇 |
1984年 | 213篇 |
1983年 | 185篇 |
1982年 | 183篇 |
1981年 | 151篇 |
1980年 | 163篇 |
1979年 | 131篇 |
1978年 | 155篇 |
1977年 | 108篇 |
1976年 | 122篇 |
1975年 | 118篇 |
1974年 | 115篇 |
1973年 | 80篇 |
1968年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Irwin L. Flink 《Brain structure & function》2002,205(3):235-244
33.
B A Sommerville C G Scanes R Swaminathan A D Care S Harvey A Chadwick 《General and comparative endocrinology》1989,76(2):261-266
An experiment was carried out to investigate the effect of a range of estradiol (E2) doses (0.1-6.5 micrograms/g body wt/day) on vitamin D metabolism and the plasma levels of growth hormone (GH) and prolactin (PRL) in the growing chick. Doses of 0.5-0.7 microgram/g E2, which are insufficient to raise the plasma calcium level, did induce an increase in growth rate, an increase in 25-hydroxyvitamin D 1 alpha-hydroxylase (1-hydroxylase) and 24-hydroxylase activities, and an increase in plasma GH level. These parameters leveled off or fell over the dose range 1-2 micrograms/g E2 but there was evidence of a second peak in 1-hydroxylase activity at 6 micrograms/g E2. At this high dose rate, the plasma Ca level rose to 8 mM, as it does in the laying hen; 24-hydroxylase activity, growth rate, and plasma GH and plasma PRL levels all decreased. It was concluded that the dose response to estrogen in the growing chick is not linear and, in the case of 1-hydroxylase activity, may even be biphasic. 相似文献
34.
Dr. Robert L. Geggel David R. Fulton Harvey L. Chernoff Richard Cleveland Thomas J. Hougen 《Pediatric cardiology》1987,8(4):279-283
Summary An infant girl is described who had cor triatriatum and partial anomalous pulmonary venous connection of the left pulmonary
veins to the coronary sinus, the first report of this combination of lesions. The infant also had a Dandy-Walker malformation
and multiple facial and intrathoracic hemangiomas. The cardiac diagnosis was made by two-dimensional echocardiography. Cardiac
catheterization and angiography confirmed the findings and also demonstrated a persistent left superior vena cava draining
to the coronary sinus. The infant underwent successful surgical repair. Partial anomalous pulmonary venous connection and
left superior vena cava not infrequently are associated with cor triatriatum. Although two-dimensional echocardiography is
sensitive for the detection of cor triatriatum, preoperative cardiac catheterization is necessary to identify unequivocally
systemic and pulmonary venous connections. 相似文献
35.
36.
37.
38.
Ann G Schwartz Geoffrey M Prysak Valerie Murphy Fulvio Lonardo Harvey Pass Jan Schwartz Sam Brooks 《Clinical cancer research》2005,11(20):7280-7287
PURPOSE: A role for estrogens in determining lung cancer risk and prognosis is suggested by reported sex differences in susceptibility and survival. Archival lung tissue was evaluated for the presence of nuclear estrogen receptor (ER)-alpha and ER-beta and the relationship between ER status, subject characteristics, and survival. EXPERIMENTAL DESIGN: Paraffin-embedded lung tumor samples were obtained from 214 women and 64 men from two population-based, case-control studies as were 10 normal lung autopsy samples from patients without cancer. Nuclear ER-alpha and ER-beta expression was determined by immunohistochemistry. Logistic regression was used to identify factors associated with ER positivity and Cox proportional hazards models were used to measure survival differences by ER status. RESULTS: Neither tumor (0 of 94) nor normal (0 of 10) lung tissue stained positive for ER-alpha. Nuclear ER-beta positivity was present in 61% of tumor tissue samples (170 of 278; 70.3% in men and 58.3% in women) and 20% of normal tissue samples (2 of 10; P = 0.01). In multivariate analyses, females were 46% less likely to have ER-beta-positive tumors than males (odds ratio, 0.54; 95% confidence interval, 0.27-1.08). This relationship was stronger and statistically significant in adenocarcinomas (odds ratio, 0.40; 95% confidence interval, 0.18-0.89). Women with ER-beta-positive tumors had a nonsignificant 73% (P = 0.1) increase in mortality, whereas men with ER-beta-positive tumors had a significant 55% (P = 0.04) reduction in mortality compared with those with ER-beta-negative tumors. CONCLUSIONS: This study suggests differential expression by sex and influence on survival in men of nuclear ER-beta in lung cancer, particularly in adenocarcinomas. 相似文献
39.
Paul Hochstein Ulrich Glatzel Thomas Schmickal Andreas Wentzensen 《Trauma und Berufskrankheit》2002,4(2):s110-s114
The treatment of deep cartilage defects in load-bearing joints is a problem that still has no satisfactory solution. Full-thickness defects of the articular cartilage rarely heal spontaneously, usually leaving damage that can lead to early arthrosis. Techniques currently available for the treatment of chondral defects include abrasion, drilling, micro-fracturing, transplantation of tissue autografts and allografts, and cell transplantation. Osteochondral autograft transplantation is currently the only surgical cartilage repair technique known to lead to the formation of genuine hyaline articular cartilage and its retention at least in the medium term. The Draenert method, in which a water-cooled diamond bone-cutting system is used, is an effective procedure for resurfacing the joints affected by localised cartilaginous defects, even when there is also severe bone loss. Donor-side morbidity can be kept to a minimum by filling the defect caused by harvesting with a press-fit cylinder of cancellous bone covered with periosteum for protection. 相似文献
40.
Annemieke Smit-van Oosten Winston W. Bakker Harry van Goor 《Transplant international》2002,15(12):602-609
Ischemic injury plays an important role in chronic renal transplant failure (CRTF). Down-regulation of ecto-adenosine triphosphatase (ATPase) in combination with up-regulation of ecto-5'-nucleotidase is a hallmark of ischemic injury. We studied the expression of renal ecto-5'-nucleotidase and ecto-ATPase in experimental renal transplantation. Fisher 344-to-Lewis allografted rats were either treated with an angiotensin-converting enzyme inhibitor (ACEi) or left untreated. Lewis-to-Lewis syngrafted rats served as controls. Untreated allografted rats developed proteinuria, glomerulosclerosis, and mild intimal hyperplasia. ACEi completely prevented focal and segmental glomerulosclerosis (FGS) and proteinuria, but significantly enhanced intimal hyperplasia. Untreated allografted rats revealed marked vascular ecto-5'-nucleotidase activity, which increased with ACEi. Vascular ecto-5'-nucleotidase activity was absent in syngrafted animals. Ecto-5'-nucleotidase activity correlated well with intimal hyperplasia. Glomerular ecto-ATPase expression was significantly reduced in untreated allografted rats compared to syngrafted rats and correlated well with the extent of FGS. ACEi prevented reduction in glomerular ecto-ATPase. We found de-novo expression of ecto-5'-nucleotidase at sites of renal intimal hyperplasia. Glomerular ecto-ATPase expression was markedly reduced in allografted rats and was prevented by ACEi. These enzyme expression patterns suggest local ischemic damage in experimental CRTF. 相似文献