全文获取类型
收费全文 | 1814篇 |
免费 | 107篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 72篇 |
妇产科学 | 106篇 |
基础医学 | 273篇 |
口腔科学 | 25篇 |
临床医学 | 147篇 |
内科学 | 340篇 |
皮肤病学 | 85篇 |
神经病学 | 225篇 |
特种医学 | 47篇 |
外科学 | 150篇 |
综合类 | 9篇 |
预防医学 | 170篇 |
眼科学 | 24篇 |
药学 | 87篇 |
中国医学 | 1篇 |
肿瘤学 | 156篇 |
出版年
2023年 | 22篇 |
2022年 | 28篇 |
2021年 | 75篇 |
2020年 | 43篇 |
2019年 | 70篇 |
2018年 | 66篇 |
2017年 | 42篇 |
2016年 | 53篇 |
2015年 | 59篇 |
2014年 | 92篇 |
2013年 | 100篇 |
2012年 | 147篇 |
2011年 | 134篇 |
2010年 | 72篇 |
2009年 | 62篇 |
2008年 | 104篇 |
2007年 | 114篇 |
2006年 | 95篇 |
2005年 | 104篇 |
2004年 | 91篇 |
2003年 | 81篇 |
2002年 | 68篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1971年 | 5篇 |
1969年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有1926条查询结果,搜索用时 15 毫秒
81.
Mammalian heparanase: involvement in cancer metastasis,angiogenesis and normal development 总被引:24,自引:0,他引:24
Vlodavsky I Goldshmidt O Zcharia E Atzmon R Rangini-Guatta Z Elkin M Peretz T Friedmann Y 《Seminars in cancer biology》2002,12(2):121-129
Cleavage of heparan sulphate proteoglycans (HSPGs) affects the integrity and functional state of tissues and thereby fundamental normal and pathological phenomena involving cell migration and response to changes in the extracellular microenvironment. Heparanase, degrading heparan sulphate (HS) at specific intrachain sites, is synthesized as a latent approximately 65 kDa protein that is processed at the N-terminus into a highly active approximately 50 kDa form. The heparanase enzyme is preferentially expressed in human tumours and its overexpression in low-metastatic tumour cells confers a highly invasive phenotype in experimental animals. Heparanase also releases angiogenic factors and accessory fragments of HS from the tumour microenvironment and induces an angiogenic response in vivo. Heparanase may thus facilitate tumour cell invasion, vascularization and survival in a given microenvironment, all critical events in cancer progression. These observations, the anticancerous effect of heparanase-inhibiting molecules, and the unexpected identification of a single predominant functional heparanase suggest that the enzyme is a promising target for drug development. 相似文献
82.
The authors discuss issues concerning the psychotherapeutic process in a psychiatric institution. They develop the concept of the institution as an internalized object in addition to its being an objective object. As such, it has an effect on the inner freedom and the internal structure of the patient, the therapist, and the supervisor. It is claimed that it is crucial for the development of an identity as a psychotherapist that the supervisor be aware of the institution as an inner and real object. The authors raise questions about what kind of "space" is possible in a psychiatric institution and what influence that may have on the therapeutic process. The impact on the therapist's professional identity is discussed. They point to the process of becoming a therapist via supervision and examine some relevant dilemmas. The authors conclude by discussing the duality of inner freedom and internal structure, and their specific manifestations within an institution. 相似文献
83.
BACKGROUND: Chromogranin A (CGA), Pro-gastrin-releasing peptide (ProGRP) and neuron-specific enolase (NSE) are known as immunohistochemical tissue markers closely associated with neuroendocrine differentiation in non-small-cell lung carcinoma (NSCLC). The aim of the present study was to assess the value of serum levels of these markers in predicting response to chemotherapy and survival of patients with unresectable NSCLC. METHODS: The study included 67 patients with advanced NSCLC treated with chemotherapy. Before treatment, serum levels of CGA, ProGRP and NSE were measured with commercial kits. RESULTS: No association was found between serum NSE and age, gender, histology, performance status or extent of the disease. Distribution of serum CGA differed significantly according to gender and histology, with higher levels being found in men (p = 0.01) and in squamous cell carcinoma (p = 0.01). Serum ProGRP levels correlated with disease extent, being higher in patients with metastatic disease (M1) than in those with locoregional disease (M0; p = 0.02). The association of NSE, CGA and ProGRP levels with response to chemotherapy was not significant. While NSE had no impact on survival, the median survival was shorter for patients with elevated serum CGA and longer for patients with high ProGRP levels. Association with survival was significant when the Classification and Regression Tree (CART)-derived or median cutoff points were explored. On inclusion in multivariate Cox models, both CGA and ProGRP retained significance with high levels showing an opposite effect on survival [CART-derived cutoff points: CGA, relative risk (RR) -4.0; p < 0.001, and ProGRP, RR -0.4; p = 0.006, and median cutoff points: CGA, RR -1.8; p = 0.04, and ProGRP, RR -0.5; p = 0.03]. The combined use of CGA, ProGRP and NSE allowed for definition of two sets of patients with significantly different median survival times (25.2 vs. 8.8 months, p = 0.0001). CONCLUSIONS: In the circulation, CGA and Pro-GRP appear to bear important information related to the prognosis for NSCLC patients before chemotherapy. While a high CGA before treatment was found as an unfavorable prognostic determinant, a high ProGRP conferred a survival advantage. The combined use of serum CGA, ProGRP and NSE may supply additional information to prognosis. 相似文献
84.
Amplitude spectra of natural images 总被引:2,自引:0,他引:2
Several studies have suggested that the amplitude spectra of photographs of natural scenes are remarkably similar and have the form: amplitude varies; is directly proportional to spatial frequency-1.0. This is, of course, a straight line with slope of -1.0 when plotted on double logarithmic coordinates. We have examined the amplitude spectra of 135 digitized photographs of natural scenes and have found that relatively few images conform exactly to the suggestion. About 25% of the images in our sample have spectra which show significant curvature when plotted on log-log coordinates. The best-fitting regression lines have slopes that range from -0.8 to -1.5; the average slope is -1.2, rather steeper than previously suggested. 相似文献
85.
Visualization of orbital soft tissue structures by computed tomography in direct coronal and axial studies is extremely useful in diagnosis. Direct enlargement viewing of scans has disclosed minute anatomical details. This study reviews some of our experiences in the investigation of a variety of lesions within the orbit and attempts, in particular, to illustrate the value of direct coronal studies. 相似文献
86.
The new 64-slice multi-detector computed tomographic scanners with improved temporal and special resolution are well suited to cardiac scanning allowing large area coverage and very short scan time. Current applications include plaque and stenosis assessment, evaluation of bypass graft patency and stenosis, coronary artery anomalies and recently, assessment of implanted coronary stents. Possible fields of utilization include emergency room triage of chest pain, and screening prior to invasive angiography in order to reduce the load of invasive studies. The future holds the prospect of automatic analysis of coronary plaque and luminal stenosis possibly opening up a new vista for non-invasive risk assessment. 相似文献
87.
88.
David?W?EvansEmail author Nadine?E?Foster Martin?Underwood Steven?Vogel Alan?C?Breen Tamar?Pincus 《BMC musculoskeletal disorders》2005,6(1):41
Background
Low back pain (LBP) is a common and costly problem. Initiatives designed to assist practitioner and patient decisions about appropriate healthcare for LBP include printed evidence-based clinical guidelines. The three professional groups of chiropractic, osteopathy and musculoskeletal physiotherapy in the UK share common ground with their approaches to managing LBP and are amongst those targeted by LBP guidelines. Even so, many seem unaware that such guidelines exist. Furthermore, the behaviour of at least some of these practitioners differs from that recommended in these guidelines. 相似文献89.
Forer B Vasilyev T Brosh T Kariv N Gil Z Fliss DM Katzir A 《Lasers in surgery and medicine》2005,37(4):286-292
BACKGROUND AND OBJECTIVES: The purpose of this study was to demonstrate that laser soldering might be successfully used for closing holes or cuts in the dura layer, which encapsulates the brain. STUDY DESIGN/MATERIALS AND METHODS: A temperature controlled fiberoptic CO(2) laser system and albumin solder were used for spot soldering of fascia patches to holes in the dura of farm pigs, in vitro and in vivo. RESULTS: The mean burst pressure of the soldered patches in the in vitro experiments was 190 +/- 88 mm Hg-significantly higher than typical maximum CSF pressure of 15 mm Hg. In the in vivo experiments the pigs showed no postoperative complications. Histopathological studies exhibited an accepted level of inflammatory reaction and showed no thermal damage to the underlying brain tissue. CONCLUSIONS: It has been clearly demonstrated that temperature controlled laser soldering is a very useful technique for the repair of the dura. It provides significant advantages over standard closure techniques: it is easy to apply, the bond is strong and watertight and the procedure is likely to be much faster than suturing. This research work will lead to clinical trials. 相似文献
90.
Computed tomography (CT) of the orbit is capable of demonstrating soft tissue structures not visualized yet by any other radiological modality. The possibility of obtaining direct coronal slices has added a new dimension to the study. Direct enlargement viewing on the display console reveals many anatomical details. For better evaluation of pathological findings, an accurate anatomical knowledge is required. The purpose of this study is to report on the normal anatomy of the orbital soft tissues made visible by CT, with emphasis on the coronal views. 相似文献