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   18507篇
  免费   1247篇
  国内免费   31篇
耳鼻咽喉   229篇
儿科学   558篇
妇产科学   332篇
基础医学   2678篇
口腔科学   510篇
临床医学   1743篇
内科学   3438篇
皮肤病学   351篇
神经病学   1649篇
特种医学   1009篇
外国民族医学   25篇
外科学   2312篇
综合类   164篇
一般理论   6篇
预防医学   1990篇
眼科学   210篇
药学   1568篇
中国医学   57篇
肿瘤学   956篇
  2021年   258篇
  2020年   168篇
  2019年   235篇
  2018年   296篇
  2017年   235篇
  2016年   266篇
  2015年   322篇
  2014年   408篇
  2013年   585篇
  2012年   815篇
  2011年   849篇
  2010年   484篇
  2009年   488篇
  2008年   801篇
  2007年   775篇
  2006年   804篇
  2005年   776篇
  2004年   697篇
  2003年   690篇
  2002年   650篇
  2001年   568篇
  2000年   600篇
  1999年   498篇
  1998年   222篇
  1997年   194篇
  1996年   157篇
  1995年   174篇
  1994年   213篇
  1993年   278篇
  1992年   597篇
  1991年   547篇
  1990年   454篇
  1989年   326篇
  1988年   298篇
  1987年   288篇
  1986年   245篇
  1985年   289篇
  1984年   211篇
  1983年   150篇
  1982年   125篇
  1981年   126篇
  1979年   170篇
  1978年   139篇
  1977年   135篇
  1976年   140篇
  1975年   148篇
  1974年   182篇
  1973年   155篇
  1971年   135篇
  1970年   123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The feasibility of using in vivo autofluorescence for the diagnosis of skin cancer was evaluated. In vivo fluorescence measurements were performed on healthy human volunteers, and patients with different types of benign and malignant skin tumours. Fluorescence spectra as well as fluorescence images were acquired. The excitation-emission matrix of normal skin (n=3) showed a broad peak at the shortest excitation wavelength (365 nm) and at 440 nm fluorescence wavelength, smoothly decreasing towards longer excitation and fluorescence wavelengths. Non-melanoma skin tumours (n=31) and control skin excited with 375 nm showed a broad fluorescence band from 400 to 700 nm, peaking around 436 nm. No significant differences in measurements between tumours and the corresponding control sites were found. A large spatial variation in the fluorescence intensity was observed both in the tumours and in the control sites. Standard deviations found ranged from 0.15 to 1.5 times the mean fluorescence. Fluorescence images, excited with 375 nm and taken with an image intensified CCD camera, on eight malignant melanomas and eight benign pigmented lesions did not indicate any fluorescence intensity distribution specific to the malignancy of the lesion. Neither the shape of the fluorescence spectra, nor the spatial distribution of the fluorescence intensity showed any signature specific to the histopathological nature of the lesions investigated. Optical diagnostics of skin tumours using the autofluorescence does not seem to be feasible at the present time.  相似文献   
83.
Objective: Microvascular pericytes may contract in two different ways: In the first, a circumferential or radial mechanical force applied at right angles to the long axis of the vessel may constrict the underlying vessel affecting blood flow and transmural pressure. Retraction and elongation of pericyte processes may also occur tangentially and at right angles to the vessel axis and alter microvessel permeability by changing the amount of ablumenal surface covered or the openness of interendothelial junctions. In this study, cultured pericytes were utilized as a model experimental system to determine if vasoactive stimulation changes their shape in a manner consistent with this hypothesis. Methods: Pericytes cultured from isolated rate capillaries were subjected to angiotensin II and histamine. Their response was monitored by measuring the area of nonyielding substrate covered by the pericytes and the manner in which their shape changed. Shape changes were quantified by calculating the surface area: perimeter perimeter ratios. Results: Histamine significantly reduced surface area covered and the surface area: perimeter ratio. The pericyte processes retracted, resulting in elongated, spindle-shaped cells. These effects were nullified by the H1 blocker diphenhydramine suggesting a receptor-specific response. Angiotensin II also elicited contraction and reduced surface area, but the cells contracted laterally and longitudinally. The surface area: perimeter ratios also decreased. Conclusions: These results indicate that pericytes are capable of two types of contractile responses in culture, depending on the specific vasoactive stimulus.  相似文献   
84.
Despite the high incidence of leukaemic infiltration of the heart, only 8 cases of atrioventricular block due to leukaemia have been reported in the literature. Improvement in the heart block associated with disappearance of the leukaemic infiltrate has not been reported. A rest thallium-201 study was used in a 65-year-old man to demonstrate leukaemic infiltration of the heart which was associated with complete heart block. After chemotherapy, when the tumour burden was reduced and the leukaemia in remission, his heart block resolved, and a follow-up thallium scan was normal. Offprint requests to: A.C. Civelek  相似文献   
85.
Pelvic fractures are frequently complicated by concomitant vascular lacerations involving, particularly, branches originating from the internal iliac arteries. Massive hemorrhage may be difficult to be treated surgically. In such cases interventional radiology can be helpful and able to treat definitely extensive hemorrhage caused by pelvic trauma.  相似文献   
86.
87.
88.
Schock     
Shock is defined as a disproportion between oxygen supply and consumption based on a deficient perfusion of vital organs. Reduction of circulating blood volume (hypovolemic shock), cardiac failure with low output (cardiac shock) or the failure of peripheral vascular resistance (distributive shock) can result in shock. Preclinically the diagnosis of shock is determined by exploration, physical examination and – some – monitoring only. Therapy is directed towards the underlying cause whilst recovery and maintenance of adequate perfusion of vitals and tissue are of primary importance. This strategy includes the application of oxygen, fluids and catecholamines. Moreover, the choice of the hospital for further therapy is crucial in case of emergency.  相似文献   
89.
Microcystic adnexal carcinoma is a rare cutaneous neoplasm characterized by slow but locally aggressive growth, which normally does not lead to systemic metastasis. Frequent local recurrences are reported, which are most likely due to insufficient operative technique. We present the fourth case of cervical ipsilateral metastatic microcystic adnexal carcinoma in an otherwise healthy woman. The patient presented with a previously diagnosed but not completely resected microcystic adnexal carcinoma in the area of the right posterior scalp and two palpable ipsilateral lymph nodes. The tumor was resected using intraoperative snap frozen histological evaluation of the resection borders. In the same procedure two lymph nodes were resected from the right neck. The lymph nodes were histologically assessed and showed infiltration by small strains of tumor cells. After exclusion of a second primary tumor, e.g., mammary carcinoma, as the cause for cervical lymph node metastases, we performed a modified radical neck dissection with resection of the sternocleidomastoid muscle and the accessory nerve, which was histologically proven to be perineurally infiltrated by tumor cells. In this second procedure the histological evaluation of the specimen showed no sign of remaining tumor infiltration. After exclusion of distant metastasis the patient was irradiated with 60 Gy. The patient is well 1 year after the initial treatment without signs of recurrence.  相似文献   
90.
Zusammenfassung Bei normal ernährten und Vitamin A-frei ernährten Ratten wird bei Sesamölzugabe keine Erhöhung der Thrombocyten beobachtet. Auch bei Gesunden und Kranken mit einer relativen Thrombopenie gelang es nicht, durch Verabreichung von Sesamöl die Thrombocyten zur Norm zu steigern. Die Anwesenheit des Faktors T im Sesamöl wird abgelehnt.  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