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   262582篇
  免费   23817篇
  国内免费   12185篇
耳鼻咽喉   3501篇
儿科学   5385篇
妇产科学   3348篇
基础医学   39841篇
口腔科学   6473篇
临床医学   21654篇
内科学   36558篇
皮肤病学   4948篇
神经病学   9864篇
特种医学   8064篇
外国民族医学   219篇
外科学   32332篇
综合类   43132篇
现状与发展   69篇
预防医学   7144篇
眼科学   3763篇
药学   19277篇
  58篇
中国医学   7345篇
肿瘤学   45609篇
  2024年   409篇
  2023年   3445篇
  2022年   6034篇
  2021年   9298篇
  2020年   8256篇
  2019年   7922篇
  2018年   8058篇
  2017年   8648篇
  2016年   9435篇
  2015年   10700篇
  2014年   15957篇
  2013年   17072篇
  2012年   14839篇
  2011年   16473篇
  2010年   13593篇
  2009年   13217篇
  2008年   13839篇
  2007年   14515篇
  2006年   13359篇
  2005年   12154篇
  2004年   10423篇
  2003年   9036篇
  2002年   7521篇
  2001年   6784篇
  2000年   5633篇
  1999年   4887篇
  1998年   4541篇
  1997年   4155篇
  1996年   3763篇
  1995年   3337篇
  1994年   2976篇
  1993年   2382篇
  1992年   2005篇
  1991年   1815篇
  1990年   1452篇
  1989年   1356篇
  1988年   1233篇
  1987年   1022篇
  1986年   886篇
  1985年   1163篇
  1984年   1003篇
  1983年   684篇
  1982年   729篇
  1981年   614篇
  1980年   522篇
  1979年   400篇
  1978年   311篇
  1977年   218篇
  1976年   190篇
  1975年   86篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Based upon detailed dissections of the lymphatic system in adult cadavers, the lymphatic drainage of the gallbladder was divided into three pathways: (1) The cholecystoretropancreatic pathway, which had two routes, one running spirally from the anterior surface of the common bile duct to the right rear, and the other running almost straight down from the posterior surface of the common bile duct. These routes converged at the principal retroportal node at the posterior surface of the head of the pancreas. (2) The cholecysto-celiac pathway; this was the route running to the left through the hepatoduodenal ligament to reach the celiac nodes. (3) The cholecysto-mesenteric pathway; this was the route running to the left in front of the portal vein to connect with the nodes at the superior mesenteric root. The cholecysto-retropancreatic pathway can be regarded as the main pathway, and the principal retroportal node appeared to be critical as the main terminal node in the visceral lymphatic system of the gallbladder. These three pathways converged with the abdomino-aortic lymph nodes near the left renal vein, and the nodes in the interaortico-caval space were considered to be of particular importance. Offprint requests to: M. Ito  相似文献   
992.
从1例膀胱癌患者的癌组织培养中,分离得到2个不同生长特性的悬浮生长型细胞系,定名为TSB-90和TSB-91。在培养过程中,对其生物学特性进行了细胞和亚细胞水平的探讨,并进行了核型分析。发现2个细胞系核型的演化趋势有明显差异,生物学特性也不尽相同。这可能与膀胱癌组织中细胞的遗传异质性和分化程度有关。对其机制和细节有待进一步深入研究。  相似文献   
993.
对136例急性肾功能衰竭患者的病因、透析率及死亡原因等进行分析。病因中以急性中毒占首位(20.59%),次为严重感染(19.12%),严重创伤(15.44%)。64例接受血液透析,29例接受腹膜透析,透析率达68.38%。本组死亡率为43.38%,透析组死亡率36.76%。,非透析组死亡率79.07%,两组有显著差异(P<0.01)。结合文献进行讨论,提出了防治建议。  相似文献   
994.
The records of 28 patients who underwent free jejunal graft reconstruction after resection for cancer involving the pharynx were analysed. Seven patients had a T3 carcinoma, 15 patients T4 and six patients recurrence after laryngectomy. Ten patients had received radiotherapy in the past. Post-operatively, 15 patients (54%) had complications and two patients (7%) died. No significant difference was observed in the complication rate between the group that received radiotherapy in the past and those who did not. Nineteen patients received post-operative radiotherapy. Nine patients had no radiotherapy on the basis of complete resection or because of serious complications. For the whole group the 2-year recurrence free period and survival were 42% and 51% respectively. The postoperative radiotherapy group had a significantly better survival (73%) and recurrence free period (63%) than the group without post-operative radiotherapy (0%). Thus, post-operative radiotherapy seems indicated irrespective of resection margins.  相似文献   
995.
应用非同位素标记PCR-SSCP技术对34例大肠癌组织p53基因第五外显子突变进行了检测。结果:50%(11/22)结肠癌,8.3%(1/12)直肠癌存在p53基因突变,低分化腺癌高于高、中分化腺癌(P<0.05),DukesB、C期高于DukesA期(P<0.05),p53基因第五外显子突变在已发生淋巴转移的大肠癌组织中呈现较强的趋势。提示:检测结肠癌原发灶p53基因第五外显子突变,对指导结肠癌的诊断、治疗及预后判断具有一定意义  相似文献   
996.
本文对三峡库区涪陵段1964~1993年肾综合征出血热(HFRS)的流行趋势作了某些分析,旨在兴建、开发三峡库区时为防治本病提供一定的依据。30年中发病乡(镇)的扩大与发现,以1964~1969年较为突出,占累计发病乡(镇)总数的27.59%,在嗣后的24年(1970~1993年)间仍以平均每年3.8个疫区的新发现渐进式扩大,可见三峡库区涪陵段HFRS疫区的发现与扩大仍未结束;发病率在80年代(6.58/10万)急剧上升,较60年代(3.53/10万)和70年代(2.51/10万)发病总数高1.83倍,90年代的发病率(1O.54/10万)较前26年上升57.49%;病例围绕高、中发疫区向心性集中,流行强度则离心性递减;在涪陵段的长江南岸、乌江北岸以集簇性暴发为主,长江北岸、乌江南岸为散在发病;呈5~7月(占27.03%)、10~12月(占45.79%)“双峰”型季节性发病高峰,1~4、8、9月份为非流行季节,其病例占总发病数的27.17%;每5~7年出现l次周期性发病高峰,高峰年的发病率与该地区整体发病率一致,似呈上升趋势;68.76%的病人集中在20~49岁人群,农民发病占83.35%,男女之比为2.5:1。疫区及疫源地以野鼠型为主,混合型次之,家鼠型也存在。  相似文献   
997.
The expression of sodium channel α-subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immunocytochemical methods with antibodies generated against conserved and subtype-specific sequences of the sodium channel. In adult rat spinal cord, astrocytes within the dorsal and ventral funiculi were immunolabelled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within these spinal cord white matter tracts were immunostained with antibody SP11-II, which recognizes sodium channel type II. Antibodies SP11-I and SP32-III, which are directed against subtype-specific sequences in sodium channel types I and III, respectively, did not label astrocytes in the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detectable labelling of cells within the optic nerve was observed with antibodies SP11-I, SP11-II, and SP32-III. These observations demonstrate that sodium channel II is expressed by astrocytes in spinal cord white matter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes.  相似文献   
998.
BACKGROUND: We hypothesise that the density of proliferating cells at the invasive tumour front (ITF) has a positive relationship with prognostic and risk factors in human oral squamous cell carcinoma (SCC). METHODS: Tissues from 47 human oral SCC specimens were collected and stained with a monoclonal antibody directed against the Ki-67 antigen using a horseradish peroxidase based two-step immunostaining method. Counting was performed on two parallel sections at the ITF using an image analyser. The Ki-67 labelling index (LI) was determined by measuring the number of nuclei/mm(2) of epithelium. RESULTS: Our results show that the density of proliferating cells is related to clinical staging, with advanced stage of disease having a significantly higher Ki-67 LI compared with early stage of disease (2111 +/- 905 vs. 1908 +/- 913; P = 0.03). Importantly, this study shows that tumours that have metastasised have a significantly higher Ki-67 LI than tumours where distant metastasis was not detected (3257 +/- 650 vs. 1966 +/- 881; P < 0.0001). CONCLUSIONS: Cell proliferation, as measured by the Ki-67 LI at the ITF, has a positive relationship with clinical staging, tumour thickness, smoking status of the patient and alcohol consumption. Further, we suggest that a multicenter study with a large cohort of patients is indicated to fully elucidate whether cell proliferation at the ITF is directly related to patient survival.  相似文献   
999.
1000.
Based on recent genetic studies, we propose a progression model for the development of oral squamous cell carcinoma. In the initial phase, a stem cell acquires a genetic alteration; subsequently a patch is formed, a clonal unit consisting of the stem cell with its daughter cells that all share the DNA alteration. The next critical step is the conversion of a patch into an expanding field as a result of additional genetic alterations. This mucosal field replaces the normal epithelium and in the oral cavity such fields have been detected with dimensions of over 7 cm in diameter. Sometimes these fields are visible as leukoplakia. Ultimately, clonal selection leads to the development of carcinoma within this contiguous field of pre-neoplastic cells. An important clinical implication of this model is that fields often remain after surgery of the primary tumor and may lead to new cancers, presently designated by clinicians as second primary tumors or local recurrences.  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