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   4970篇
  免费   665篇
  国内免费   162篇
耳鼻咽喉   46篇
儿科学   33篇
妇产科学   179篇
基础医学   2173篇
口腔科学   60篇
临床医学   285篇
内科学   274篇
皮肤病学   23篇
神经病学   78篇
特种医学   49篇
外国民族医学   4篇
外科学   330篇
综合类   680篇
预防医学   193篇
眼科学   167篇
药学   132篇
中国医学   34篇
肿瘤学   1057篇
  2024年   13篇
  2023年   50篇
  2022年   79篇
  2021年   146篇
  2020年   179篇
  2019年   207篇
  2018年   152篇
  2017年   220篇
  2016年   237篇
  2015年   226篇
  2014年   318篇
  2013年   319篇
  2012年   289篇
  2011年   304篇
  2010年   276篇
  2009年   284篇
  2008年   245篇
  2007年   242篇
  2006年   230篇
  2005年   191篇
  2004年   197篇
  2003年   167篇
  2002年   164篇
  2001年   118篇
  2000年   43篇
  1999年   56篇
  1998年   143篇
  1997年   113篇
  1996年   89篇
  1995年   52篇
  1994年   40篇
  1993年   46篇
  1992年   34篇
  1991年   40篇
  1990年   34篇
  1989年   30篇
  1988年   36篇
  1987年   37篇
  1986年   35篇
  1985年   32篇
  1984年   12篇
  1983年   12篇
  1982年   11篇
  1981年   9篇
  1980年   4篇
  1979年   6篇
  1978年   14篇
  1977年   3篇
  1976年   7篇
  1975年   4篇
排序方式: 共有5797条查询结果,搜索用时 15 毫秒
1.
【目的】观察不同浓度花生四烯酸 (AA)和 (或 )二十二碳六烯酸 (DHA)对体外培养海马神经细胞生长发育的影响。【方法】无血清培养液中分别加入不同剂量的AA和 (或 )DHA ,采用噻唑蓝比色试验 (MTT法 )反映各组海马神经细胞存活状况 ,神经元特异性烯醇化酶 (NSE)染色鉴定神经细胞 ,图像分析技术测量神经细胞的胞体大小和突起长度。【结果】培养液中分别添加AA为 4~ 8μmol/L、DHA为 2~ 8μmol/L时 ,神经细胞活力高于对照组 ;当培养液中AA和DHA总浓度为 4μmol/L、比例为 2∶1或 4∶1时 ,神经细胞的活力、胞体面积、最大长径、最大短径和平均突起长度均显著高于单一添加 4μmol/LAA、4μmol/LDHA和对照组。【结论】AA、DHA均具有促进体外培养海马神经细胞生长发育的作用 ;与单独添加AA、DHA相比 ,AA和DHA共同作用的促海马神经细胞生长发育作用更好。  相似文献   
2.
Granular cell tumors (GCT) are rare neoplasms, and only 173 cases of benign GCT of the breast have been documented. We report herein the cases of two patients with this tumor and discuss the methods of diagnosis and treatment. The first patient was a 60-year-old woman who presented with a firm ill-defined mass in her left breast. Mammography showed a dense shadow with spicula and skin thickness, and ultrasonography revealed a hypoechoic mass with an irregular border. Radical mastectomy was performed under the wrong preoperative diagnosis of breast cancer. The second patient was a 31-year-old woman who presented with an elastic-hard mass in her left breast. Mammography showed a well-demarcated dense mass, and ultrasonography revealed a well-defined hypoechoic mass with a large depth-width ratio. Fine-needle aspiration cytology (FNAC) showed a large number of histiocytic cells with abundant granular cytoplasm. An excisional biopsy was performed, and histological examination confirmed a diagnosis of GCT. GCT is benign, but often misdiagnosed as breast cancer both clinically and radiologically. Therefore, histological examination is essential for making a correct diagnosis, while FNAC is also useful. Local resection is still the treatment of choice, and surgeons should do their utmost to avoid performing needless radical mastectomy.  相似文献   
3.
兔关节软骨细胞的分离、培养和形态学特征   总被引:9,自引:2,他引:7  
[目的]探讨兔关节软骨细胞的分离、培养方法,观察单层高浓度培养时细胞表型表达情况.[方法]无菌条件下,从 2周龄新西兰白兔的颞颌关节及四肢关节髁突面削取软骨片,采用机械-酶消化法分离软骨细胞,经台盼蓝拒染计数,将细胞按 1× 106个 /孔接种于 6孔培养板,传代培养,描绘生长曲线.利用相差显微镜及透射电镜观察细胞形态.应用甲苯胺蓝及Ⅱ型胶原免疫组化对细胞进行鉴定.[结果]每克软骨能获取 1 5× 106个软骨细胞,活性率为 95%.培养 2~ 3 d,细胞贴壁、变形,呈多角形; 8 d左右,细胞融合成层.透射电镜观察显示细胞核圆形,有丰富的粗面内质网、高尔基体及分泌的基质成分.甲苯胺蓝及Ⅱ型胶原染色阳性.细胞传至 5代后,出现"成纤维细胞样".[结论]本研究建立了简单易行的软骨细胞分离、培养方法;初代、第 2代细胞生长良好,适合于实验研究;软骨细胞 5代培养后,细胞表型发生改变.  相似文献   
4.
The diagnostic yield of cytology in histologically proven transitional-cell carcinoma (TCC) of the urinary bladder has been studied in 100 cases. Cytohistologic correlation rates were 20 percent, 61.7 percent, and 92.8 percent, respectively, for grade 1, 2, and 3 tumors. When further evaluated, G2 cases were segregated into 2 subcategories, G2a and G2b, based on histologic preservation of nuclear polarity, pleomorphism, and other cellular irregularities. Correlation rates were rather low for G2a cases (6/18, 33%) and high for G2b cases, (23/29; 79%). The prevalence of atypical cells was 2 (11.1%) cases in G2a and 16 (55.2%) cases in G2b. The results of this study confirm that cytology has an extremely varying diagnostic yield in urinary bladder TCC. Greater cell exfoliation, increased atypia, and a tendency to infiltration of G2b and G3 cases probably account for the higher diagnostic yield detected in these groups.  相似文献   
5.
Endoscopic ultrasound (EUS) is sensitive for staging gastrointestinal malignancies and pancreatic lesions. EUS‐fine‐needle aspiration (EUS‐FNA) offers a diagnostic accuracy of about 60–90% for pancreatic tumors and > 90% for lymph nodes. There are several limitations of EUS‐FNA including the need for on‐site cytopathology review. In addition, accuracy of cytologic review is hampered by the presence of blood, benign epithelial cells, desmoplasia, and well‐differentiated tumors. Furthermore, the small biopsy sample and destruction of tissue architecture limits the diagnostic sensitivity for GISTs and lymphomas. Many of these problems can be overcome with use of EUS trucut biopsy (TCB) needles. These large caliber, cutting needles acquire larger tissue samples allowing preservation of tissue architecture and histologic examination. Our recently described experience with EUS‐TCB initially in swine and later humans demonstrated the safety for acquiring histologic tissue representative of the target organs sampled enabling accurate diagnosis. These studies suggested greater diagnostic accuracy of EUS‐TCB for submucosal mass lesions and lymphoma and potentially the need for fewer needle passes for solid pancreatic neoplasms. In this paper we will review the current TCB literature, device design and technique, help troubleshoot potential problems, and offer opinion as to the utility and role of this new device.  相似文献   
6.
K Alderson 《Muscle & nerve》1992,15(11):1284-1289
The presence, morphology, distribution, and abundance of axonal swellings in intramuscular nerves were evaluated. Axonal swellings were present in intramuscular nerves in 42% of 127 muscle biopsies from patients with a variety of conditions. The incidence was highest in muscle from patients with peripheral neuropathy, but swellings were present in muscle from patients with motor neuron disease, primary muscle diseases, and some individuals without clinical or histological evidence of neuromuscular disease. The greatest number of swellings in intramuscular nerves was in muscle from patients with chronic inflammatory demyelinating neuropathy. Swellings were spherical or elliptical, 4-20 microns in diameter, 5-30 microns in length, and composed of neurofilaments. Swellings were present only in myelinated axons of intramuscular nerves, proximal to nodes of Ranvier or in internodal regions. Swellings were not associated with axonal degeneration. They were probably not transported. The formation or accumulation of swellings may reflect altered axonal dynamics common to a number of disease processes.  相似文献   
7.
Granulocytic sarcoma (GS) is a localized tumour of immature granulocytes that is usually associated with myelogenous leukaemia. We report an unusual case of mastoid GS with meningeal extension but no bone marrow involvement on presentation. Histological examination of the surgical specimen and the characteristic cerebrospinal fluid (CSF) cytology showing cytoplasmic granulations and Auer bodies led to the diagnosis of GS. Positive cytochemical staining of the immature CSF cells for naphtol-ASD chloroacetate esterase and myeloperoxidase confirmed their myeloid origin. Immunophenotyping did not reveal common acute lymphoblastic leukaemia antigen, cytokeratin, T or B-cell antigens. The patient underwent surgical resection of the localized tumour, followed by radiation therapy, intrathecal and systemic chemotherapy, as if he had acute myelogenous leukaemia (AML). He did not develop AML in the 21 months after the tumour resection. This case emphasizes the value of CSF cytological examination of tumour cells and the use of an immumocytochemical marker for differentiating GS from malignant lymphoma.  相似文献   
8.
Clear-cell lesions of the parotid gland are uncommon but when studied by fine-needle aspiration may result in a clinically important but cytologically difficult differential diagnosis. Clear-cell lesions involving the parotid include acinic cell neoplasm, clear cell oncocytoma, mucoepidermoid carcinoma, primary clear-cell carcinoma, epithelial-myoepithelial carcinoma, and metastatic renal cell carcinoma. Accurate diagnosis is achieved by assessment of nuclear features, other cell populations present, and clinical data including radiographic studies.  相似文献   
9.
A 4(1/2)-yr-old female presented with right-sided pleural effusion and a retroperitoneal mass. Cytologic analysis of the pleural fluid yielded malignant small round blue cells, which were noncohesive, 3-4 times the size of lymphocytes. The malignant cells had hyperchromatic, pleomorphic nuclei with moderate amounts of vacuolated cytoplasm. A few fiber-shaped cells were also seen. Immunostains for desmin, muscle-specific actin were positive; ultrastructural findings of thick and thin actin-myosin filaments confirmed the diagnosis of embryonal rhabdomyosarcoma. This case illustrates the importance of performing appropriate immunohistochemical stains and ultrastructural studies on cytological material to arrive at a definitive diagnosis.  相似文献   
10.
Objective: To compare the cytological findings of hypoechoic thyroid nodules with intranodular vascular pattern (pattern II) obtained by two different needles (Neolus 25 gauge, Chemil, Wenzhou, China vs Yale Spinal 25 gauge, Becton Dickinson, Madrid, Spain) in euthyroid patients and to evaluate their cost-effectiveness. Methods: From January 2001 to December 2003, 480 euthyroid patients with a hypoechoic thyroid nodule pattern II were referred for US-FNAC. The nodules were alternatively evaluated by Neolus or by Yale Spinal with the stylet (YS+) or without the stylet (YS−), in order to evaluate if the cytological results could be due to the presence of the stylet or to the different length of the two needles. For each nodule two passes were performed and the material was obtained by capillary action. Material was smeared on slides, fixed, and stained by Papanicolaou techniques. Cytological specimens were evaluated in blind by the same experienced cytopathologist. Results: Inadequate cytological specimens because of blood contamination were present in 30 (18.7%) samples by Neolus needle and in 22 (13.8%) by YS− compared to only 5 (3.1%) by YS+. In 6 (20%) cases of the 30 repeated US-FNAC by Neolus and in 4 (18%) of the 22 US-FNAC by YS−, material remained inadequate for diagnosis because of blood contamination. All the five repeated samples obtained by YS+ became adequate for diagnosis and resulted benign nodules. Direct costs of US-FNAC procedure are currently Э 72.30 including cytological examination. The cost of Neolus and Yale needles is Э 0.19 and Э 3.0, respectively. The estimated total cost to obtain a cytological diagnosis by a Neolus needle (160 + 30 repeated US-FNAC) was Э 13809.2 vs Э 12919.5 by Yale Spinal needle (160 + 5 repeated US-FNAC). Conclusion: This study demonstrates that the use of Yale Spinal needles greatly reduces inadequate cytological specimens, and therefore limits both direct and indirect costs.  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