全文获取类型
收费全文 | 2314篇 |
免费 | 324篇 |
国内免费 | 40篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 110篇 |
妇产科学 | 30篇 |
基础医学 | 144篇 |
口腔科学 | 37篇 |
临床医学 | 321篇 |
内科学 | 676篇 |
皮肤病学 | 63篇 |
神经病学 | 216篇 |
特种医学 | 399篇 |
外科学 | 352篇 |
综合类 | 36篇 |
预防医学 | 77篇 |
眼科学 | 19篇 |
药学 | 64篇 |
中国医学 | 1篇 |
肿瘤学 | 119篇 |
出版年
2023年 | 52篇 |
2022年 | 22篇 |
2021年 | 43篇 |
2020年 | 97篇 |
2019年 | 22篇 |
2018年 | 103篇 |
2017年 | 78篇 |
2016年 | 78篇 |
2015年 | 73篇 |
2014年 | 121篇 |
2013年 | 135篇 |
2012年 | 75篇 |
2011年 | 68篇 |
2010年 | 101篇 |
2009年 | 126篇 |
2008年 | 66篇 |
2007年 | 66篇 |
2006年 | 66篇 |
2005年 | 53篇 |
2004年 | 36篇 |
2003年 | 24篇 |
2002年 | 38篇 |
2001年 | 39篇 |
2000年 | 21篇 |
1999年 | 35篇 |
1998年 | 88篇 |
1997年 | 98篇 |
1996年 | 82篇 |
1995年 | 71篇 |
1994年 | 53篇 |
1993年 | 53篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 30篇 |
1989年 | 62篇 |
1988年 | 52篇 |
1987年 | 45篇 |
1986年 | 33篇 |
1985年 | 37篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1971年 | 10篇 |
排序方式: 共有2678条查询结果,搜索用时 15 毫秒
21.
Understanding the genetic mechanisms that control brain patterning in vertebrates represents a major challenge for developmental neurobiology. The cloning of genes likely to be involved in the organization of the brain and an analysis of their roles have revealed insights into the molecular pathways leading to neural induction, tissue specification, and regionalization of the brain. Among these genes, both Otx1 and Otx2, two murine homologs of the Drosophila orthodenticle (otd) gene, contribute to several steps in brain morphogenesis. Recent findings have demonstrated that Otx2 plays a major role in gastrulation and in the early specification of the anterior neural plate while Otx1 is mainly involved in corticogenesis, and Otx1 and Otx2 genes cooperate in such a way that a minimal level of OTX proteins are required for proper regionalization and subsequent patterning of the developing brain. Finally, experiments have shown functional equivalence between Drosophila otd and vertebrate Otx genes, suggesting a surprising conservation of function required in brain development throughout evolution. 相似文献
22.
23.
GA Smith SD Strausbaugh C Harbeck-Weber DM Cohen BJ Shields JD Powers 《Pediatrics》1997,100(5):825-830
OBJECTIVE: To compare the effectiveness of three new topical anesthetics that do not contain cocaine (prilocaine-phenylephrine, tetracaine-phenylephrine [tetraphen], and tetracaine-lidocaine-phenylephrine) to that of tetracaine-adrenaline-cocaine (TAC) during laceration repair in children. DESIGN: Prospective, randomized, double-blind clinical trial. SETTING: The emergency department of an urban children's hospital. PARTICIPANTS: Children 1 year of age or older with a laceration = 5 cm in length that required suturing. Intervention. A total of 240 children were randomly assigned to one of four treatment groups. OUTCOME MEASURES: Pain felt during suturing was scored by suture technicians, research assistants, parents, and patients >/= 5 years of age using a visual analogue scale (VAS). Suture technicians, research assistants, and parents also scored pain using a seven-point Likert scale. In addition, suture technicians completed an anesthetic effectiveness scale. RESULTS: There was consistently no difference demonstrated between the effectiveness of tetraphen and that of TAC for each outcome measure of each observer group. A statistically significant difference was seen among anesthetics when comparing VAS and Likert scale scores of suture technicians and Likert scale scores of research assistants. Based on post hoc analyses, these statistically significant differences were between TAC and prilocaine-phenylephrine (suture technician VAS and Likert scale) and between TAC and tetracaine-lidocaine-phenyl-ephrine (suture technician Likert scale), but not between TAC and tetraphen. When power analyses were performed using alpha = 0.05 and beta = 0.20, it was possible to detect a difference of 1.2 VAS units for each of the observer groups. Based on anesthetic effectiveness scale scores, the three new topical preparations collectively performed significantly better on the face and scalp than on the extremities (relative risk = 1.83; 95% confidence interval 1.20 < relative risk < 2.79). CONCLUSION: This study demonstrated the effectiveness and safety of three new non-cocaine-containing topical anesthetics. Consistently, there was no statistical difference demonstrated between the effectiveness of tetraphen and that of TAC for each outcome measure of each observer group. Tetraphen offers an effective alternative to TAC during laceration repair in children. 相似文献
24.
Increased placental apoptosis in intrauterine growth restriction 总被引:2,自引:0,他引:2
Stephen C. Smith MB ChB Philip N. Baker DM E.Malcolm Symonds MD 《American journal of obstetrics and gynecology》1997,177(6):1395-1401
OBJECTIVES: Our purpose was to investigate a possible role for apoptosis in the pathophysiologic mechanisms of intrauterine growth restriction. STUDY DESIGN: Placental samples were obtained from 43 uncomplicated third-trimester pregnancies and from 26 pregnancies complicated by intrauterine growth restriction. The definition used to identify cases of intrauterine growth restriction depended on three criteria: clinical evidence of suboptimal growth, ultrasonographic evidence of deviation from an appropriate growth percentile, and individualized birth weight ratios <10th percentile. Light microscopy was used to quantify the incidence of apoptosis. Electron microscopy and TUNEL (terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling) staining were used to confirm the occurrence of apoptosis. RESULTS: Quantification of apoptosis (medians and interquartile ranges) resulted in the following values: normal third trimester (n = 43) 0.14% of cells (0.08% to 0.20%) and intrauterine growth restriction third trimester (n = 26) 0.24% of cells (0.16% to 0.29%). The incidence of apoptosis was significantly higher in placentas from pregnancies with intrauterine growth restriction compared with normal third-trimester placentas (p < 0.01, Mann Whitney U test). CONCLUSIONS: These results suggest that apoptosis may play a role in the pathophysiologic mechanisms of intrauterine growth restriction.(Am J Obstet Gynecol 1997;177:401) 相似文献
25.
26.
27.
Autoimmune pancreatitis: imaging features 总被引:24,自引:0,他引:24
Sahani DV Kalva SP Farrell J Maher MM Saini S Mueller PR Lauwers GY Fernandez CD Warshaw AL Simeone JF 《Radiology》2004,233(2):345-352
PURPOSE: To retrospectively determine imaging findings in patients with autoimmune pancreatitis. MATERIALS AND METHODS: Twenty-nine patients (25 male and four female; mean age, 56 years; range, 15-82 years) with histopathologic diagnosis of autoimmune pancreatitis were examined. Data were reviewed by two radiologists in consensus. Imaging findings for review included those from helical computed tomography (CT), 25 patients; magnetic resonance (MR) imaging with MR cholangiopancreatography (MRCP), four patients; endoscopic ultrasonography (US), 21 patients; endoscopic retrograde cholangiopancreatography (ERCP), 19 patients; and percutaneous transhepatic cholangiography, one patient. Images were analyzed for appearances of pancreas, biliary and pancreatic ducts, and other findings, such as peripancreatic inflammation, encasement of vessels, mass effect, pancreatic calcification, peripancreatic nodes, and peripancreatic fluid collection. Follow-up images were available in nine patients. Serologic markers such as serum immunoglobulin G (IgG) and antinuclear antibody levels were available in 12 patients. RESULTS: CT showed diffuse (n = 14) and focal (n = 7) enlargement of pancreas. Seven patients had minimal peripancreatic stranding, with lack of vascular encasement, calcification, or peripancreatic fluid collection. Nine patients had enlarged peripancreatic lymph nodes. MR imaging showed focal (n = 2) and diffuse (n = 2) enlargement with rimlike enhancement in one. MRCP revealed pancreatic duct strictures in two and sclerosing cholangitis-like appearance in one. Endoscopic US showed diffuse enlargement of pancreas with altered echotexture in 13 patients and focal mass in the head in six. ERCP showed stricture of distal common bile duct in 12 patients, irregular narrowing of intrahepatic ducts in six, diffuse irregular narrowing of pancreatic duct in nine, and focal stricture of proximal pancreatic duct in six. Serologic markers showed increased IgG and antinuclear antibody levels in seven of 12 patients. At follow-up, CT abnormalities and common bile duct strictures resolved after steroid therapy in three patients. CONCLUSION: Features that suggest autoimmune pancreatitis include focal or diffuse pancreatic enlargement, with minimal peripancreatic inflammation and absence of vascular encasement or calcification at CT and endoscopic US, and diffuse irregular narrowing of main pancreatic duct, with associated multiple biliary strictures at ERCP. 相似文献
28.
Hamady ZZ Malik HZ Finch R Adair R Al-Mukhtar A Prasad KR Toogood GJ Lodge JP 《Annals of surgical oncology》2006,13(11):1493-1499
Background Many colorectal liver metastasis patients are denied surgical resection on the basis of tumour size. The aim of this study was to explore the impact of metastasis size on modern liver resection.Methods Using a prospectively collected database, this was a retrospective analysis of 484 consecutive patients who underwent liver resection for colorectal liver metastases between 1993 and 2003. The cohort was divided into two groups: smaller metastases (<8 cm) and larger metastases (≥ 8 cm). Those with larger metastases were then further stratified into big metastases (8–12 cm) and giant metastases (>12 cm). Demographic, pathological, surgical technique and outcome data were compared between the groups.Results There were 88 (18%) patients with metastases measuring 8 cm or larger. There was an association between higher carcinoembryonic antigen (CEA) and cancer antigen (CA) 19-9 levels and larger metastases. The actuarial 5-year survival for patients with larger metastases was 38% compared with 42% for smaller metastases (not statistically significant). Patients with giant metastases had poorer overall and disease-free survival (both nonsignificant) compared with those with big metastases: 29% and 28% at 5 years, respectively.Conclusion Patients with colorectal liver metastasis greater than 8 cm and up to 12 cm in size should not be treated differently from those with smaller lesions. 相似文献
29.
30.