全文获取类型
收费全文 | 24065篇 |
免费 | 1517篇 |
国内免费 | 117篇 |
专业分类
耳鼻咽喉 | 329篇 |
儿科学 | 664篇 |
妇产科学 | 686篇 |
基础医学 | 3754篇 |
口腔科学 | 345篇 |
临床医学 | 2271篇 |
内科学 | 4729篇 |
皮肤病学 | 696篇 |
神经病学 | 2317篇 |
特种医学 | 1384篇 |
外国民族医学 | 8篇 |
外科学 | 3347篇 |
综合类 | 201篇 |
一般理论 | 11篇 |
预防医学 | 1593篇 |
眼科学 | 543篇 |
药学 | 1590篇 |
中国医学 | 61篇 |
肿瘤学 | 1170篇 |
出版年
2022年 | 168篇 |
2021年 | 332篇 |
2020年 | 231篇 |
2019年 | 314篇 |
2018年 | 394篇 |
2017年 | 327篇 |
2016年 | 443篇 |
2015年 | 452篇 |
2014年 | 552篇 |
2013年 | 706篇 |
2012年 | 1072篇 |
2011年 | 1119篇 |
2010年 | 637篇 |
2009年 | 622篇 |
2008年 | 913篇 |
2007年 | 1004篇 |
2006年 | 1011篇 |
2005年 | 996篇 |
2004年 | 904篇 |
2003年 | 847篇 |
2002年 | 839篇 |
2001年 | 810篇 |
2000年 | 722篇 |
1999年 | 682篇 |
1998年 | 351篇 |
1997年 | 294篇 |
1996年 | 267篇 |
1995年 | 240篇 |
1994年 | 220篇 |
1993年 | 218篇 |
1992年 | 404篇 |
1991年 | 387篇 |
1990年 | 429篇 |
1989年 | 410篇 |
1988年 | 383篇 |
1987年 | 415篇 |
1986年 | 370篇 |
1985年 | 361篇 |
1984年 | 278篇 |
1983年 | 218篇 |
1979年 | 268篇 |
1978年 | 214篇 |
1977年 | 193篇 |
1975年 | 175篇 |
1974年 | 191篇 |
1973年 | 195篇 |
1972年 | 220篇 |
1971年 | 195篇 |
1969年 | 173篇 |
1967年 | 171篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
Felix Eckstein Axel Weusten Corina Schmidt Ulrich Wehr Rüdiger Wanke Walter Rambeck Eckhard Wolf Subburaman Mohan 《Journal of bone and mineral research》2004,19(5):802-810
In this study we examined the effect of systemic overexpression of GH on bone in transgenic mice longitudinally in vivo over a period of 9 months. We observed substantially increased BMC in GH transgenic mice and a significant reduction in serum osteocalcin. GH effects on bone were strongly dependent on gender and developmental stage. INTRODUCTION: State-of-the-art bone marker and microimaging technology was applied in this longitudinal study to examine bone metabolism, BMC, bone density, and cortical bone structure over the life span of growth hormone (GH) transgenic (tg) mice. MATERIALS AND METHODS: Thirty-eight mice from four genetic groups (male, female, tg, and controls) were examined with DXA, and their femur and tibia were examined with peripheral QCT (pQCT). Osteocalcin (formation) and collagen cross-links (resorption) from serum and urine were also measured at postnatal weeks 3, 6, 9, 12, 18, 26, and 38. RESULTS: GH tg mice displayed a significant increase in body weight (up to 50%) and BMC (up to 90%), but serum osteocalcin was significantly reduced compared with controls. GH tg females (but not males) displayed increased trabecular density over controls up to week 12. In contrast, male (but not female) GH tg mice displayed a higher cortical cross-sectional area than controls. Cortical density was significantly lower in both male and female GH tg mice compared with control mice. CONCLUSIONS: The increase in BMC in GH tg mice is associated with reduced serum osteocalcin levels, indicating that bone turnover may be lower than in the control mice. On a structural level, bone responds to GH excess in a gender-specific manner, with alterations varying substantially between different developmental stages. 相似文献
74.
A framework for evaluating image segmentation algorithms. 总被引:4,自引:0,他引:4
Jayaram K Udupa Vicki R Leblanc Ying Zhuge Celina Imielinska Hilary Schmidt Leanne M Currie Bruce E Hirsch James Woodburn 《Computerized medical imaging and graphics》2006,30(2):75-87
The purpose of this paper is to describe a framework for evaluating image segmentation algorithms. Image segmentation consists of object recognition and delineation. For evaluating segmentation methods, three factors-precision (reliability), accuracy (validity), and efficiency (viability)-need to be considered for both recognition and delineation. To assess precision, we need to choose a figure of merit, repeat segmentation considering all sources of variation, and determine variations in figure of merit via statistical analysis. It is impossible usually to establish true segmentation. Hence, to assess accuracy, we need to choose a surrogate of true segmentation and proceed as for precision. In determining accuracy, it may be important to consider different 'landmark' areas of the structure to be segmented depending on the application. To assess efficiency, both the computational and the user time required for algorithm training and for algorithm execution should be measured and analyzed. Precision, accuracy, and efficiency factors have an influence on one another. It is difficult to improve one factor without affecting others. Segmentation methods must be compared based on all three factors, as illustrated in an example wherein two methods are compared in a particular application domain. The weight given to each factor depends on application. 相似文献
75.
76.
Two new lethal peptides (waglerins) were purified from the venom of Trimeresurus wagleri, and sequenced. We found them to be analogs of lethal peptides (waglerins) I and II reported previously (Weinstein et al., Toxicon 29, 227-236, 1991), with an additional Ser-Leu on the amino terminus. Three of the four waglerins were synthesized and the products were chemically and biologically equivalent to the naturally occurring counterparts in venom. Murine i.p. LD50 for synthetic waglerins I, SL-I and II were 0.33, 0.22, and 0.51 mg/kg, respectively. The single, intramolecular disulfide bond in each synthetic peptide formed rapidly in high yield. The reduced (cysteine-containing) forms of the peptides appeared to have significant toxicities, even without prior disulfide bond formation, but synthetic analogs with serine substituted for cysteine were not toxic. The synthetic dimer of waglerin I, formed by two intermolecular disulfide bonds, was not toxic, but rapidly rearranged to lethal, monomeric waglerin I at alkaline pH upon the addition of 5 mM beta-mercaptoethanol. Waglerin I was inactivated by cleavage at Tyr-15 with chymotrypsin. 相似文献
77.
Surgical Principles
Radical arthroscopic synovectomy of rheumatoid shoulder and elbow.
Revised Version from: Operat. Orthop. Traumatol. 4 (1992), 112–129 (German Edition). 相似文献
78.
At the lumbosacral spinal cord level in the rat, substance P-positive neurons are present in dense concentration in the dorsal horn and the sacral parasympathetic nucleus. We undertook the present study to investigate the effect of intrathecal substance P (10 micrograms at the L6-S1 level) on urinary bladder and urethral sphincteric activity and to compare these effects with those of intravenous and intra-arterial administration. Three different bladder pressure responses were triggered by intrathecal substance P: (A) an immediate, strong bladder contraction (n = 5); (B) augmentation of the micturition reflex, as indicated by strong detrusor contractions in response to intravesical saline perfusion (n = 4); and (C) a slow, gradual increase to a high, steady peak (n = 8). The sphincteric electromyographic (EMG) activity was consistently increased. When substance P was given intravenously (n = 10) and intra-arterially (n = 3), the form, duration, and maximal amplitude of bladder contractions (owing to a direct smooth-muscle action) were comparable with those of Group A. The effects in intrathecal Groups B and C suggest that substance P provides a tonic influence on motor horn cells and on the preganglionic neurons in the sacral parasympathetic nucleus at the lumbosacral spinal cord level, where neuronal circuits controlling bladder and sphincteric activity are located. 相似文献
79.
Five female patients and one male patient with solid and papillary epithelial neoplasms of the pancreas were examined with computed tomography (CT). The mean age of the patients was 27 years (range, 13-46 years). All cases showed well-encapsulated, round or lobulated masses consisting of both cystic and solid areas. Cystic portions showed CT numbers that suggested hemorrhagic necrosis. There were no internal septations within the masses. In three tumors located in the head of the pancreas, dilatation of the biliary tree was absent or minimal, although the masses were large. Two tumors contained calcifications. One tumor demonstrated metastatic deposits in liver and lymph nodes. Metastatic masses appeared similar to the primary pancreatic mass. Solid and papillary neoplasm of the pancreas should be the primary diagnostic consideration when characteristic CT findings are detected in a young female patient. 相似文献
80.
An eosinophilic granuloma has been investigated by means of histochemical proofs for enzymes and tissue elements and common staining methods. The best method was be found the proof for the enzyme phenol oxidase (EC 1.14.18.1). In this way it is possible to determine eosinophils rapidly and surely and to receive an overview on the frequency and distribution of these cells. The histiocytic-like cells was identified electron microscopical as Langerhans' cells. This cells are in narrow contact to many eosinophilic granulocytes. Their granula have manifold changes in their structure. The granula are possibly able to produce new structures of the cell. The eosinophilic granuloma correspond to a cell mediating immunological defence reaction approximate to the type of a delayed hypersensitivity. 相似文献