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   26780篇
  免费   1925篇
  国内免费   64篇
耳鼻咽喉   236篇
儿科学   750篇
妇产科学   551篇
基础医学   3177篇
口腔科学   363篇
临床医学   2631篇
内科学   5253篇
皮肤病学   703篇
神经病学   2325篇
特种医学   1031篇
外国民族医学   1篇
外科学   4158篇
综合类   422篇
一般理论   60篇
预防医学   2289篇
眼科学   850篇
药学   1781篇
中国医学   18篇
肿瘤学   2170篇
  2022年   173篇
  2021年   350篇
  2020年   228篇
  2019年   347篇
  2018年   433篇
  2017年   367篇
  2016年   399篇
  2015年   454篇
  2014年   703篇
  2013年   1028篇
  2012年   1534篇
  2011年   1587篇
  2010年   897篇
  2009年   813篇
  2008年   1539篇
  2007年   1597篇
  2006年   1570篇
  2005年   1647篇
  2004年   1605篇
  2003年   1518篇
  2002年   1496篇
  2001年   426篇
  2000年   345篇
  1999年   372篇
  1998年   353篇
  1997年   320篇
  1996年   299篇
  1995年   281篇
  1994年   248篇
  1993年   243篇
  1992年   308篇
  1991年   270篇
  1990年   253篇
  1989年   253篇
  1988年   229篇
  1987年   215篇
  1986年   226篇
  1985年   251篇
  1984年   233篇
  1983年   225篇
  1982年   260篇
  1981年   260篇
  1980年   224篇
  1979年   183篇
  1978年   196篇
  1977年   186篇
  1976年   126篇
  1975年   137篇
  1974年   149篇
  1973年   113篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
Abstract: For the women with early-stage breast cancer who are candidates for breast conservation therapy, re-excision of the primary tumor bed has commonly been used in patients for several indications. These indications include positive margin or uncertain margin status of the primary excision or residual microcalcifications on postbiopsy mammogram. If the pathology from the re-excision does not confirm negative margin status, mastectomy is generally recommended. This article examines patients who have undergone a second re-excision (i.e., a lumpectomy followed by two re-excisions) who have been treated with breast conservation therapy rather than a mastectomy.
From September 1977 to November 1995, 1,562 patients underwent breast conserving therapy at this institution. Seven hundred forty of these patients underwent a re-excisional biopsy because of positive or uncertain margin status or residual microcalcifications after the first excision. Four patients (0.5%) underwent a second re-excision because of positive or uncertain margin status or residual microcalcifications on mammogram after the first re-excision. The final margin status after the second re-excision of all four patients was negative. The radiation dose was 4,600–5,000 cGy to the whole breast followed by a conedown to bring the total dose to 6,400–6,800 cGy to the primary tumor bed.
Follow-up in the four patients was 13 years, 4 years, 14 months, and 8 months respectively. All four patients are clinically without disease and have not had a locoregional recurrence. Cosmesis was excellent in all four patients. One patient had an adriamycin-induced recall reaction causing a cellulitis, which resolved with antibiotics. There were no other complications.
Highly selected patients may undergo breast-conserving therapy after a second re-excision. Good outcome and cosmesis can be achieved for this small subset of patients with avoidance of a mastectomy.  相似文献   
53.
Magnetic resonance (MR) imaging may be a noninvasive method for assessing perfusion of vascularized bone grafts placed for treatment of avascular necrosis. One proximal femur of seven beagles was devascularized, with insertion of a vascularized fibular graft. MR imaging at 1 week (seven dogs) and 6 weeks (five dogs) after surgery included pre- and postcontrast spin-echo sequences, unenhanced twodimensional time-of-flight (TOF) vascular imaging, and dynamic gradient-echo imaging during infusion of gadolinium. Relative signal intensity values of selected regions obtained from the dynamic gradientecho images were plotted as percent enhancement versus time. In the operated hip, MR imaging did not show enhancement in six of seven femoral heads and greater trochanters at 1 week after surgery, with similar results after 6 weeks. MR imaging of fibular grafts 6 weeks after surgery showed an initial rapid increase in enhancement and a subsequent slower increase in five of five dogs, although no enhancement was seen in six of seven dogs at 1 week. These findings contrasted with a rapid initial increase in enhancement followed by slow decline in non-operated hips. Two-dimensional TOP imaging did not show the vascular pedicle of the graft in any dog. Findings of radionuclide bone scanning performed 1 week after surgery were consistent with devascularization of the operated femur and fibular graft. However, tetracycline distribution and histologic findings confirmed the viability of five of five grafts within the devascularized femurs 6 weeks after surgery. Thus, dynamic contrast-enhanced MR imaging at 6 weeks after surgery is valuable for assessing vascular bone graft perfusion, while similar imaging at 1 week may suggest otherwise.  相似文献   
54.
55.
A case of spontaneous rupture of the spleen as a complication and presenting factors of systemic amyloidosis is reported with a review of the pertinent literature. the sequelae of amyloid involvement of the spleen is discussed with emphasis on possible mechanisms involved in the causation of spontaneous rupture of this organ.  相似文献   
56.
During the past several years, there has been a resurgence of interest in preoperative or postoperative chemotherapy in patients with Stage III lung cancer. The staging system for lung cancer has recently been modified, and at the present time Stage III disease is now subdivided into Stage III-A (potentially surgically resectable for cure) and Stage III-B (unresectable). This article will review five recently completed studies utilizing neoadjuvant therapy in various types of Stage III lung cancer. The thoracic surgeon is faced with the dilemma of reviewing this literature and trying to make a conclusion as to what is appropriate therapy for Stage III disease. Unquestionably, neoadjuvant therapy appears to increase the resectability rate in Stage III-A disease and can make some Stage III-B patients anatomically resectable. It is hoped that future well-designed phase III studies can be accomplished in Stages III-A and III-B disease so that we can determine whether neoadjuvant chemotherapy is or is not beneficial for these patients.  相似文献   
57.
Prospective studies suggest that tea may protect against cardiovascular disease. A potential mechanism for such an effect involves inhibition of lipid peroxidation by polyphenolic antioxidants derived from tea. Our objective was to determine whether regular ingestion of tea could inhibit in vivo lipid peroxidation. Two controlled intervention studies assessed the effects of regular ingestion of tea on lipid peroxidation determined by measurement of urinary F(2)-isoprostane excretion. Study 1: The effects of 1000 mL/d of green tea and black tea were compared with hot water containing caffeine in 13 subjects with elevated blood pressure using a randomized 3-period (7 d each) crossover design. Study 2: The effects of 1250 mL/d of black tea were compared with hot water in 22 subjects with mildly raised serum total cholesterol concentrations using a randomized 2-period (4 wk each) crossover design. F(2)-isoprostane excretion was not altered after regular ingestion of green tea (273 +/- 48 pmol/mmol creatinine) or black tea (274 +/- 39 pmol/mmol creatinine) in comparison with hot water (263 +/- 47 pmol/mmol creatinine; Study 1), or by regular ingestion of black tea (334 +/- 71 pmol/mmol creatinine) in comparison with hot water (355 +/- 75 pmol/mmol creatinine; Study 2). These results do not support the suggestion that polyphenolic antioxidants derived from tea inhibit in vivo lipid peroxidation.  相似文献   
58.
59.
60.
Self-expanding endovascular graft: an experimental study in dogs   总被引:2,自引:0,他引:2  
An arterial endovascular graft was constructed by wrapping an expandable nylon mesh around a framework of Gianturco self-expanding metallic stents. The devices were passed through a 12-French Teflon catheter and positioned in the normal abdominal aorta of five dogs, two of which also had a device placed in an external iliac artery. At follow-up (1-6 months), all grafts remained patent, even though slight luminal narrowing due to neointimal encasement was noted. Histologically, all grafts were covered by neointimal proliferation at the time of removal. The graft material expanded with the stents, resulting in a tight fit between the graft and the vessel wall. Side branches narrowed but remained open because of the size of the nylon mesh. No migration of the grafts equipped with a barbed lead stent was noted. Expandable nylon mesh can be used as an endovascular graft material when wrapped around a framework of self-expanding stents. The resulting device can be easily delivered via transcatheter techniques, and once placed in a vessel, the nylon acts as a support for neointimal encasement, which forms a new vascular lumen.  相似文献   
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