全文获取类型
收费全文 | 58001篇 |
免费 | 4044篇 |
国内免费 | 167篇 |
专业分类
耳鼻咽喉 | 777篇 |
儿科学 | 1672篇 |
妇产科学 | 1003篇 |
基础医学 | 7050篇 |
口腔科学 | 939篇 |
临床医学 | 6036篇 |
内科学 | 12057篇 |
皮肤病学 | 950篇 |
神经病学 | 5451篇 |
特种医学 | 2181篇 |
外国民族医学 | 1篇 |
外科学 | 9837篇 |
综合类 | 737篇 |
一般理论 | 56篇 |
预防医学 | 4138篇 |
眼科学 | 972篇 |
药学 | 3738篇 |
中国医学 | 46篇 |
肿瘤学 | 4571篇 |
出版年
2023年 | 268篇 |
2022年 | 472篇 |
2021年 | 1179篇 |
2020年 | 691篇 |
2019年 | 1199篇 |
2018年 | 1416篇 |
2017年 | 1051篇 |
2016年 | 1080篇 |
2015年 | 1281篇 |
2014年 | 1965篇 |
2013年 | 2561篇 |
2012年 | 4086篇 |
2011年 | 4258篇 |
2010年 | 2393篇 |
2009年 | 2043篇 |
2008年 | 3701篇 |
2007年 | 3951篇 |
2006年 | 3907篇 |
2005年 | 3807篇 |
2004年 | 3652篇 |
2003年 | 3382篇 |
2002年 | 3147篇 |
2001年 | 625篇 |
2000年 | 547篇 |
1999年 | 608篇 |
1998年 | 661篇 |
1997年 | 525篇 |
1996年 | 430篇 |
1995年 | 418篇 |
1994年 | 390篇 |
1993年 | 327篇 |
1992年 | 426篇 |
1991年 | 423篇 |
1990年 | 401篇 |
1989年 | 379篇 |
1988年 | 385篇 |
1987年 | 352篇 |
1986年 | 325篇 |
1985年 | 286篇 |
1984年 | 316篇 |
1983年 | 290篇 |
1982年 | 285篇 |
1981年 | 266篇 |
1980年 | 201篇 |
1979年 | 202篇 |
1978年 | 177篇 |
1977年 | 156篇 |
1976年 | 127篇 |
1974年 | 166篇 |
1973年 | 134篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Elliot Carlisle MD Mario Luna MD Paul M. Tsou MD Jeffrey C. Wang MD 《The spine journal》2005,5(6):608-614
BACKGROUND CONTEXT: There is limited information describing the correlation between the initial quantitative measurements on magnetic resonance imaging (MRI) scans of disc herniation area, canal cross-section areas, percent canal compromise, and disc herniation location to the need for surgery. PURPOSE: Our aim is to determine if the size of disc herniation area, canal cross-section area, percent canal compromise, and disc herniation location taken from MRI images of patients with symptomatic single-level lumbar herniated intervertebral discs upon initial presentation to a spine surgeon, were predictive of the need for surgical treatment. STUDY DESIGN/SETTING: This is a retrospective case matched study of patient MRI images in the senior author's private practice. PATIENT SAMPLE: From a pool of 332 patients with sciatica caused by lumbar intervertebral disc herniations at our institution, 65 patients had surgery, of which MRI images were available and analyzed on 44 patients. Forty-four additional patients were randomly selected from the remaining 267 original group as nonoperative controls. METHODS: The axial MRI image showing the largest canal compromise by the herniated disc was selected for measurements. Using T1- and T2-weighted images, the areas of interest were digitally scanned at high resolution. The canal area and disc herniation area measurement were calculated from the total number of pixels per cross-sectional area, multiplied by a scan correction factor, mm(2) /pixel. Disc herniation locations were classified into either central or paracentral. The percent canal compromise was obtained by disc herniation area divided by canal cross-section area and multiplied by 100. RESULTS: The surgical group's overall mean herniated disc area was 219.6 square millimeter (mm(2)), 179.8 at L4-5, and 267.4 at L5-S1. The nonoperative group's overall mean herniated disc area was 178.4 mm(2), 135.1 at L2-3, 160.3 at L4-5, and 207.4 at L5-S1. The surgical group's overall mean canal cross-sectional area was 471.8 mm(2), 418.6 at L4-5, and 535.6 at L5-S1. The nonoperative group's overall mean canal cross-sectional area was 541.3 mm(2), 518.1 at L2-3, 446.8 at L4-5, and 669.9 at L5-S1. The overall percent canal compromise ratio in the surgery group was 46.7%, 44.1% at L4-5, and 49.8% at L5-S1. The overall percent canal compromise in the nonoperative group was 34.2%, 34.1% at L2-3, 36.1% at L4-5, and 31.8% at L5-S1. The percent canal compromise in central herniations at L4-5 level was 53.0% in the surgical group, and 32.8% in the nonoperative group; at the L5-S1 level surgical group percent canal compromise was 64.1% and in the nonoperative group canal compromise was 27%. L4-L5 level paracentral herniations canal compromise was 36.7% in the surgical group compared with 42.5% canal compromise in the nonoperative group. At the L5-S1 level the canal compromise was 45% in the surgical group and 34.8% in the nonoperative group. CONCLUSIONS: Our findings show a trend for patients treated with surgery to have larger disc herniation areas and smaller canal cross-section areas, corresponding to larger percent canal compromise than the nonoperative group. Centrally located herniations followed this trend closely at all levels studied. However, the paracentral herniation at the L4-5 level does not follow this trend, possibly because paracentral disc herniation clinical course is determined more by herniation location rather than the overall herniation size. 相似文献
62.
63.
64.
Tooth movement and cytokines in gingival crevicular fluid and whole blood in growing and adult subjects. 总被引:1,自引:0,他引:1
Laura R Iwasaki Larry D Crouch Albert Tutor Scott Gibson Navin Hukmani David B Marx Jeffrey C Nickel 《American journal of orthodontics and dentofacial orthopedics》2005,128(4):483-491
INTRODUCTION: Tooth movement has been studied largely with respect to the force required for tipping when pressure distribution varies along the length of the periodontal ligament. But important factors for effective canine translation include the nature and magnitude of applied stress and the patient's cell biology. The purpose of this research was to test 3 hypotheses: (1) the velocity of tooth translation (v(t)) is related to applied stress and growth status, (2) a threshold of stress accounts for the lag phase, and (3) v(t) is correlated with the ratio (AI) of 2 cytokines (IL-1beta, IL-1RA) measured in gingival crevicular fluid (GCF) and stimulated whole blood (SWB). METHODS: Continuous maxillary canine retraction stresses of 13 kPa and 4, 26, or 52 kPa were applied bilaterally in 6 growing and 4 adult subjects for 84 days. Dental models and GCF samples were collected at 1- to 14-day intervals. Cytokines were measured in GCF and SWB cell cultures. RESULTS: V(t) was positively related to stress and was higher in growing subjects (P = .001). It was also related to AI(GCF) in growers (R2= 0.56) and nongrowers (R2= 0.72). Canines moved with 52 kPa showed a lag phase, and postlag phase AI(GCF) was twice that of lag phase AI(GCF). Mean v(t) and associated AI(GCF) during the postlag phase were nearly double the values for canines moved with 13 and 26 kPa. SWB production of cytokines was dose-dependent. For growing subjects, SWB IL-1RA was correlated with v(t) (R = 0.70-0.72), and AI(SWB) and IL-1beta concentrations were correlated with AI(GCF) (R = 0.73-0.78). CONCLUSIONS: V(t) varied with growth status and stresses < or = 52 kPa; stresses of < 52 kPa showed no lag phase; and equivalent stresses yielded subject-dependent differences in v(t), which correlated with cytokines in GCF and SWB. 相似文献
65.
66.
Alexis A Gintowt Jeffrey J Germer P Shawn Mitchell Joseph D C Yao 《Journal of clinical virology》2005,34(2):155-157
BACKGROUND: The current manual sample processing method recommended for use with the TRUGENE HBV Genotyping Kit (TRUGENE HBV; Bayer HealthCare LLC, Tarrytown, NY) is labor-intensive and may be prone to specimen cross-contamination. Recent evaluations of the MagNA Pure LC (MP; Roche Applied Science, Indianapolis, IN) suggest that it is suitable for automated, contamination-free extraction and purification of viral nucleic acids from large-volume (1.0 mL) serum or plasma specimens. OBJECTIVES: We evaluated the MP Total Nucleic Acid Isolation Kit--Large Volume (Roche Applied Science) in conjunction with TRUGENE HBV to establish the analytical sensitivity (threshold titer) of the assay, in HBV DNA International Units (IU)/mL, for obtaining consistent, interpretable sequence data from TRUGENE HBV. STUDY DESIGN: HBV analytical standards, prepared as 10 replicates (1.0 mL each) at each of the following concentrations: 200, 1000, 5000, and 10,000 IU/mL, were processed by MP and analyzed by TRUGENE HBV according to manufacturer's instructions. Performance of TRUGENE HBV used in conjunction with MP sample processing was evaluated further using 22 clinical serum specimens containing low titers of HBV DNA. RESULTS: All replicates of HBV analytical standards at 1000, 5000, and 10,000 IU/mL yielded interpretable TRUGENE HBV sequences, whereas interpretable sequences were obtained in 90% (9 of 10) of the replicates at 200 IU/mL. TRUGENE HBV sequences were interpretable in 86% (19 of 22) of the clinical specimens studied. CONCLUSIONS: MP sample processing is efficient and suitable for use with TRUGENE HBV. When combined with MP sample processing, TRUGENE HBV yielded interpretable sequences from HBV analytical standards and clinical serum specimens with HBV DNA titers of > or =200 IU/mL. 相似文献
67.
We report 2 cases of diffuse intraperitoneal metastases from testicular carcinoma following transabdominal retroperitoneal lymphadenectomy. This is an unusual pattern of metastasis for nonseminomatous germ cell tumors and it is believed to be the result of direct seeding from lymphatic leakage secondary to surgery. The value of computerized tomography in diagnosing this entity is emphasized. 相似文献
68.
69.
70.