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   2153167篇
  免费   162421篇
  国内免费   4341篇
耳鼻咽喉   29244篇
儿科学   65908篇
妇产科学   59068篇
基础医学   305330篇
口腔科学   61471篇
临床医学   191044篇
内科学   426050篇
皮肤病学   48537篇
神经病学   173694篇
特种医学   82734篇
外国民族医学   536篇
外科学   332554篇
综合类   46756篇
现状与发展   4篇
一般理论   678篇
预防医学   159846篇
眼科学   49226篇
药学   157452篇
  4篇
中国医学   4843篇
肿瘤学   124950篇
  2019年   15967篇
  2018年   23025篇
  2017年   17726篇
  2016年   19886篇
  2015年   22411篇
  2014年   31263篇
  2013年   46574篇
  2012年   63181篇
  2011年   66637篇
  2010年   39313篇
  2009年   37758篇
  2008年   62999篇
  2007年   66446篇
  2006年   67537篇
  2005年   65356篇
  2004年   62661篇
  2003年   60040篇
  2002年   58342篇
  2001年   114299篇
  2000年   117244篇
  1999年   97363篇
  1998年   25481篇
  1997年   22792篇
  1996年   22930篇
  1995年   21676篇
  1994年   19787篇
  1993年   18467篇
  1992年   73954篇
  1991年   70758篇
  1990年   68063篇
  1989年   65609篇
  1988年   60086篇
  1987年   58644篇
  1986年   54602篇
  1985年   52317篇
  1984年   38689篇
  1983年   32635篇
  1982年   18625篇
  1981年   16401篇
  1979年   34128篇
  1978年   23513篇
  1977年   19818篇
  1976年   18041篇
  1975年   19018篇
  1974年   23071篇
  1973年   22068篇
  1972年   20772篇
  1971年   19214篇
  1970年   18313篇
  1969年   17078篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
962.
963.
964.
965.
The authors present a case of amyloid infiltration involving the trigeminal nerve that mimicked a malignant cavernous sinus tumor with perineural tumor infiltration. A 64-year-old man presented with trigeminal nerve numbness. Imaging revealed a plaque-like enhancing lesion along the right lateral cavernous sinus extending anteriorly into Meckel's cave and involving the proximal V2 and V3 branches of the trigeminal nerve. The patient underwent an extradural frontotemporal craniotomy with middle fossa exposure of the cavernous sinus to diagnose and treat the presumed malignant cavernous sinus tumor. A reddish mass involving the lateral dural wall of the cavernous sinus was resected. The gasserian ganglion, V2, and V3, the latter of which was biopsied, were enlarged. Permanent histopathological studies showed microscopic eosinophilic, amorphous material, which stained positive for Congo red, and an absence of neoplastic cells. The final diagnosis was amyloidoma. Thus, amyloidomas can involve the trigeminal nerve or ganglia and should be considered in the differential diagnosis of a cavernous sinus lesion mimicking a tumor. Patients may have symptomatic improvement of trigeminal neuropathy with resection of the amyloidoma outside the nerve capsule that is compressing the nerve, while resection of the lesion from within the capsule may result in permanent trigeminal nerve dysfunction.  相似文献   
966.
967.
Apoptosis is a central physiological mechanism for maintaining cellular stability in tissue. Synovial fibroblasts, which play a central role in the pathogenesis of rheumatoid arthritis (RA), show a resistance to apoptosis. Several molecular mechanisms are involved in such resistance. Thus, soluble Fas can bind Fas ligands (Fas-L) and hinder Fas-L induced apoptosis in fibroblasts. SUMO-1 (a small ubiquitin-like modifier) attaches to proteins post-translationally. This appears to be significantly involved in apoptosis resistance in RA fibroblasts. SUMO-1 levels are substantially increased in synovial fibroblasts from RA patients. A change in the post-translational SUMOlation pattern could represent a new target for changing the stable activation of synovial fibroblasts in RA.  相似文献   
968.
BACKGROUND: Although many histopathologic factors in squamous cell carcinoma of the tongue predict the prognosis, the major predictive factors have not been identified clearly. This study analyzed the prognostic value of the histologic grade at the deep invasive front of tongue squamous cell carcinoma. METHODS: The clinicopathologic features of 124 consecutive patients seen between January 1985 and December 1999 with previously untreated squamous cell carcinoma of the tongue were reviewed. Their mean age was 58.5 years (range: 23-90) and the male-female ratio was 1.8: 1 (79 men and 45 women). There were 41, 40, 30, and 13 cases at stage I to stage IV, respectively. The clinicopathologic factors, especially the histologic grade at the deep invasive front (invasive front grade, IFG), were analyzed to determine factors predicting prognosis. RESULTS: The 5-year disease-free survival rate of the patients treated with curative aim only was 66.7%. Clinicopathologic factors significantly associated with the prognosis were T classification, tumor size, stage classification, tumor depth, macroscopic appearance, cervical lymph node metastasis (nodal metastasis), microvascular invasion, and IFG. In a multivariate analysis, patients with tumor depth >/=4 mm, IFG >/=8 points, and nodal metastasis had a reduced disease-free survival and IFG >/=11 points had a predictive value for nodal metastasis (odds ratio: 7.34; P = 0.0019). CONCLUSION: This study found that a high IFG malignancy score had a high prognostic value for squamous cell carcinoma of the tongue.  相似文献   
969.
The reaction route (RR) graph approach recently developed by us for complex, non-linear kinetic mechanisms is applied to the hydrogen oxidation and evolution reactions. A corresponding RR graph is constructed and translated into an equivalent electrical circuit network by associating each elementary step with a characteristic resistance for the steady-state case and considering the overall reaction as a power source. It is further shown that the steady-state kinetics of the reaction can be investigated employing the conventional methods of the electrical network theory. Using a set of rate constants for the hydrogen evolution reaction (her) in alkaline solutions from the literature, the dominant RRs are identified and simplified mechanisms and kinetics derived.  相似文献   
970.
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   
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