首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   14957篇
  免费   1141篇
  国内免费   268篇
耳鼻咽喉   233篇
儿科学   271篇
妇产科学   262篇
基础医学   2128篇
口腔科学   284篇
临床医学   1394篇
内科学   3231篇
皮肤病学   446篇
神经病学   982篇
特种医学   969篇
外科学   1949篇
综合类   321篇
现状与发展   1篇
一般理论   8篇
预防医学   732篇
眼科学   289篇
药学   1373篇
  1篇
中国医学   302篇
肿瘤学   1190篇
  2024年   30篇
  2023年   111篇
  2022年   342篇
  2021年   524篇
  2020年   289篇
  2019年   388篇
  2018年   489篇
  2017年   347篇
  2016年   577篇
  2015年   658篇
  2014年   852篇
  2013年   936篇
  2012年   1254篇
  2011年   1266篇
  2010年   766篇
  2009年   671篇
  2008年   858篇
  2007年   848篇
  2006年   748篇
  2005年   760篇
  2004年   627篇
  2003年   568篇
  2002年   500篇
  2001年   302篇
  2000年   261篇
  1999年   202篇
  1998年   77篇
  1997年   76篇
  1996年   78篇
  1995年   60篇
  1994年   50篇
  1993年   42篇
  1992年   87篇
  1991年   100篇
  1990年   79篇
  1989年   58篇
  1988年   56篇
  1987年   40篇
  1986年   56篇
  1985年   45篇
  1984年   35篇
  1983年   33篇
  1982年   19篇
  1980年   16篇
  1979年   32篇
  1978年   25篇
  1977年   19篇
  1976年   15篇
  1974年   19篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.

Purpose

To retrospectively determine the frequency, natural progression, radiographic characteristics, and primary cancer cell type of focal ground-glass opacities (GGOs) identified on serial radiographic examinations in patients with prior non-small cell lung carcinoma (NSCLC) resection.

Methods

One thousand three hundred and seventy-nine CT examinations in 154 patients with NSCLC resection between 1997 and 2008 were reviewed by two radiologists to determine the frequency of postoperative focal GGOs. Percentages, imaging characteristics and primary cancer cell types of GGOs that persisted, resolved, or resected were recorded. For persistent GGOs, growth rate was determined.

Results

Of 154 patients, 67 (44%) developed 174 GGO during a mean follow-up of 2.7 years (standard deviation 2.23 years, range 1 month to 10 years). Of these 174 opacities, 110 (63%) spontaneously resolved within 6 months. Of the remaining 64 lesions, 5 (3%) were resected and 59 (34%) persisted and demonstrated indolent growth with a median annual growth rate of 2.02 mm. Of the 59 persistent GGOs, 41 (69%) were nodularly shaped, 58 (95%) indistinctly marginated, 17 (29%) with pseudocavitation and 25 (42%) contained solid elements. Adenocarcinoma was the original resected cancer in more than half of these lesions (37 of 59, 63%).

Conclusions

In individuals who have undergone NSCLC resection, approximately 44% will develop focal GGO on follow-up CT examination. A majority of these GGOs will spontaneously resolve by 6 months after initial identification. As most persistent GGOs are indolent, we propose an initial 6-month interval reimaging once postoperative GGOs are detected followed by subsequent annual surveillance.  相似文献   
72.
Intratumor heterogeneity is a major clinical problem because tumor cell subtypes display variable sensitivity to therapeutics and may play different roles in progression. We previously characterized 2 cell populations in human breast tumors with distinct properties: CD44+CD24- cells that have stem cell-like characteristics, and CD44-CD24+ cells that resemble more differentiated breast cancer cells. Here we identified 15 genes required for cell growth or proliferation in CD44+CD24- human breast cancer cells in a large-scale loss-of-function screen and found that inhibition of several of these (IL6, PTGIS, HAS1, CXCL3, and PFKFB3) reduced Stat3 activation. We found that the IL-6/JAK2/Stat3 pathway was preferentially active in CD44+CD24- breast cancer cells compared with other tumor cell types, and inhibition of JAK2 decreased their number and blocked growth of xenografts. Our results highlight the differences between distinct breast cancer cell types and identify targets such as JAK2 and Stat3 that may lead to more specific and effective breast cancer therapies.  相似文献   
73.
74.
This article highlights the technical challenges and general imaging strategies for coronary MRI. This is followed by a review of the clinical results for the assessment of anomalous CAD, coronary artery aneurysms, native vessel integrity, and coronary artery bypass graft disease using the more commonly applied MRI methods. It concludes with a brief discussion of the advantages/disadvantages and clinical results comparing coronary MRI with multidetector CT (MDCT) coronary angiography.  相似文献   
75.
Cho YM  Park KS  Jung HS  Jeon HJ  Ahn C  Ha J  Kim SJ  Rhee BD  Kim SY  Lee HK 《Diabetes care》2003,26(4):1123-1128
OBJECTIVE: The incidence of posttransplantation diabetes mellitus (PTDM) has been reported to vary according to different study populations or different definitions. In this study, using American Diabetes Association criteria, the incidence and clinical characteristics of PTDM in Korean renal allograft recipients undergoing tacrolimus-based immunosuppression were examined. RESEARCH DESIGN AND METHODS: A total of 21 patients taking tacrolimus as primary immunosuppressant were recruited and tested with a serial 75-g oral glucose tolerance test at 0, 1, 3, and 6 months after renal transplantation. RESULTS: The cumulative incidence of PTDM was 52.4% at 1 month and 57.1% at 3 and 6 months. The baseline characteristics of the PTDM group were old age (especially >40 years), a high BMI, a high fasting glucose level, a high plasma insulin level, and increased insulin resistance. Among these parameters, old age was the only independent risk factor. The insulin secretory capacity in the PTDM group was maximally suppressed 3 months after transplantation. Thereafter, it was gradually restored along with dose reduction of tacrolimus. CONCLUSIONS: Routine screening for PTDM is necessary in patients over 40 years of age who are undergoing a relatively higher dose tacrolimus therapy during the early course of postrenal transplantation.  相似文献   
76.
Although the mechanisms of action (MoA) of nonstructural protein 3 inhibitors (NS3i) and NS5B inhibitors (NS5Bi) are well understood, the MoA of cyclophilin inhibitors (CypI) and NS5A inhibitors (NS5Ai) are not fully defined. In this study, we examined whether CypI and NS5Ai interfere with hepatitis C virus (HCV) RNA synthesis of replication complexes (RCs) or with an earlier step of HCV RNA replication, the creation of double-membrane vesicles (DMVs) essential for HCV RNA replication. In contrast to NS5Bi, both CypI and NS5Ai do not block HCV RNA synthesis by way of RCs, suggesting that they exert their antiviral activity prior to the establishment of enzymatically active RCs. We found that viral replication is not a precondition for DMV formation, since the NS3-NS5B polyprotein or NS5A suffices to create DMVs. Importantly, only CypI and NS5Ai, but not NS5Bi, mir-122, or phosphatidylinositol-4 kinase IIIα (PI4KIIIα) inhibitors, prevent NS3-NS5B-mediated DMV formation. NS3-NS5B was unable to create DMVs in cyclophilin A (CypA) knockdown (KD) cells. We also found that the isomerase activity of CypA is absolutely required for DMV formation. This not only suggests that NS5A and CypA act in concert to build membranous viral factories but that CypI and NS5Ai mediate their early anti-HCV effects by preventing the formation of organelles, where HCV replication is normally initiated. This is the first investigation to examine the effect of a large panel of anti-HCV agents on DMV formation, and the results reveal that CypI and NS5Ai act at the same membranous web biogenesis step of HCV RNA replication, thus indicating a new therapeutic target of chronic hepatitis C.  相似文献   
77.
78.
ObjectiveTo assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings.ResultsThe MD, LD, and RD cut-off values were 1.079 × 10-3, 1.719 × 10-3, and 0.749 × 10-3 mm2/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (p = 0.003), FA and LD∩FA (p < 0.001), FA and RD∩FA (p < 0.001), MD and LD∩FA (p = 0.024) and MD and RD∩FA (p = 0.024).ConclusionFractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.  相似文献   
79.
ObjectiveWe described the technique of ultrasound (US)-guided percutaneous removal of the foreign bodies (FB) with hydro-dissection in the radiologic department and presented video files of several cases.ResultsThe mean time required for the entire procedure was approximately 20 minutes. There were no significant complications during the US-guided removal or long-term complications after the procedure. All 4 FBs were successfully removed from the soft tissue under US guidance.ConclusionUltrasound-guided percutaneous removal of the FBs with hydro-dissection in the radiology department is a less invasive and safe method over surgical removal in the operating room. Additionally, the use of a guide wire and serial dilator may help minimize soft tissue injury and facilitate the introduction of forceps.  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号