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   25822篇
  免费   2419篇
  国内免费   2147篇
耳鼻咽喉   210篇
儿科学   272篇
妇产科学   366篇
基础医学   3226篇
口腔科学   515篇
临床医学   3541篇
内科学   4007篇
皮肤病学   200篇
神经病学   1500篇
特种医学   997篇
外国民族医学   14篇
外科学   2706篇
综合类   4071篇
现状与发展   8篇
一般理论   4篇
预防医学   1612篇
眼科学   603篇
药学   2822篇
  15篇
中国医学   1491篇
肿瘤学   2208篇
  2024年   90篇
  2023年   411篇
  2022年   1076篇
  2021年   1355篇
  2020年   1006篇
  2019年   909篇
  2018年   873篇
  2017年   872篇
  2016年   763篇
  2015年   1167篇
  2014年   1541篇
  2013年   1269篇
  2012年   1875篇
  2011年   1952篇
  2010年   1284篇
  2009年   991篇
  2008年   1399篇
  2007年   1373篇
  2006年   1273篇
  2005年   1397篇
  2004年   933篇
  2003年   917篇
  2002年   728篇
  2001年   591篇
  2000年   641篇
  1999年   659篇
  1998年   438篇
  1997年   396篇
  1996年   338篇
  1995年   318篇
  1994年   283篇
  1993年   187篇
  1992年   205篇
  1991年   172篇
  1990年   142篇
  1989年   106篇
  1988年   106篇
  1987年   80篇
  1986年   81篇
  1985年   57篇
  1984年   37篇
  1983年   29篇
  1982年   13篇
  1981年   12篇
  1980年   11篇
  1979年   10篇
  1978年   5篇
  1977年   4篇
  1975年   4篇
  1929年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
对低温,低压,高活性的A301氨合成催化剂的本征动力学进行了研究,实验采用等温积分反应器,在320-480度,6.0MPa-10.0MPa,5000h^-1--30000h^-1的条件下测定了反应器出口氨浓度,建立了Temkin形式的动力学方程,获得了反应的活化能及指前因子。  相似文献   
172.
目的 :研究大鼠脑室脉络丛细胞内是否存在ANPmRNA的基因表达。方法 :原位杂交技术。结果 :脉络丛细胞及侧脑室和第三脑室室管膜上皮细胞内呈现ANP阳性反应产物。结论 :证明在脑室脉络丛细胞及室管膜上皮细胞内存在ANPmRNA的表达。本实验结果为脉络丛产生分泌ANP提供了形态学依据 ;为脉络丛产生的ANP可能发挥的生理作用提供了理论基础  相似文献   
173.
目的;研究DYS19基因座在中国北方汉族、维吾尔族、哈萨克族群体中的遗传多态性及其法医学应用。方法:应用聚合酶链反应后变性聚丙烯酰胺凝胶电泳分离扩增产物结合银染显带的方法,对101例北方汉族、56例维吾尔族、30例哈萨克族无关男性个体的DYS19基因座进行检测。结果:DYS19基因座在3个群体中共检出5种等位基因,基因频率分布范围分别为0.069-0.594,0.071-0.500,0.100-0.667;个人识别机率分别为0.600,0.675,0.491。χ^2检验表明等位基因分布具有明显的人群差异。家系调查符合单体父系遗传方式。结论:DYS19基因座个人识别机率高,属较高鉴别能力的遗传标记系统,且具有明显的人群分布差异,在法医学及人类遗传学研究中具有重要的应用价值。  相似文献   
174.
Yu  Jinbo  Chen  Xiaohong  Wang  Yaqiong  Liu  Zhonghua  Shen  Bo  Teng  Jie  Zou  Jianzhou  Ding  Xiaoqiang 《International urology and nephrology》2021,53(4):785-795
International Urology and Nephrology - It is unclear which time-points of intradialytic blood pressure (BP) best predict prognosis. Thus, it is important to assess the association between different...  相似文献   
175.
Ding  Wei  Huang  Zheng  Zhou  Gaofeng  Li  Lang  Zhang  Mingyu  Li  Zhenyan 《Neurosurgical review》2021,44(5):2933-2941

This study aimed to investigate the role of diffusion-weighted imaging (DWI) in predicting tumor consistency, extent of surgical resection, and recurrence in pituitary adenoma (PA). We reviewed a prospectively collected database of surgically treated PA between March 2016 and October 2017. Predictors for extent of resection and recurrence/progression were assessed with logistic and Cox regression analysis. Of the 183 patients, the tumor consistency was found soft in 107 (58.5%) patients, intermediate in 41 (22.4%) patients, and hard in 35 (19.1%) patients. The mean of ADC ratio was 0.92 ± 0.22 for hard tumor, 1.03 ± 0.22 for intermediate tumor, and 1.41 ± 0.62 for soft tumor (P < 0.001). The mean collagen content was 25.86% ± 15.00% for hard tumor, 16.05% ± 9.90% for intermediate tumor, and 5.00% ± 6.00% for soft tumor (P < 0.001). Spearman analysis showed a significant correlation between ADC ratio and collagen content (ρ = ? 0.367; P < 0.001). Gross-total resection (GTR) was obtained in 68.3% of patients, and multivariable logistic regression analysis showed that ADC ratio (OR, 12.135; 95% CI, 4.001–36.804; P < 0.001), giant PA (OR, 0.233; 95% CI, 0.105–0.520; P < 0.001), and invasion (OR, 0.459; 95% CI, 0.220–0.960; P = 0.039) were significantly predictive of GTR. Twenty-seven (14.8%) patients suffered recurrence/progression in the mean follow-up of 35.14 months. Invasion (HR, 2.728; 95% CI, 1.262–5.899; P = 0.011) was identified as independent predictors of recurrence/progression. ADC ratio of DWI could be used for preoperative assessment of tumor consistency, tumor collagen content, and extent of surgical resection, which might be useful in preoperative planning for patients with PA.

  相似文献   
176.
177.
BackgroundTo summarize our experience with the Boari flap-psoas hitch and compare the indications, perioperative data and outcomes between open and laparoscopic procedures.MethodsThis study retrospectively reviewed 35 patients with complex distal ureteral stricture between January 2015 and April 2019. All patients were treated with Boari flap-psoas hitch by either an open or a laparoscopic procedure. Selection criteria were based on the etiology, comorbidities, medical history, and patient preference.ResultsAll surgeries were performed successfully. The median operation time was 201 min (range, 120 to 300 min), and the median estimated blood loss was 50 mL (range, 20 to 400 mL). The median postoperative hospitalization was 9 days (range, 3 to 46 days). Nineteen patients were treated by the open procedure, and 16 were treated by the transperitoneal laparoscopic procedure. The surgical indication of open surgery was broader than that for laparoscopic surgery. For patients experiencing iatrogenic injury and ureterovesical reimplantation failure, no significant differences in sex, laterality, operative time, ASA score or postoperative hospitalization stay were observed between the two groups. The median estimated blood loss was lower in the laparoscopic group than in the open group (P=0.047). Patients in the open group had more surgical complications than patients in the laparoscopic group (P=0.049). The postoperative follow-up showed the radiological resolution of hydronephrosis in 33 patients.ConclusionsWith the appropriate surgical considerations, Boari flap-psoas hitch is a valid method to bridge distal ureteral defects. For select patients, laparoscopic surgery had advantages being a minimal invasive surgery with less estimated blood loss and fewer surgical complications.  相似文献   
178.
BackgroundRadical/cytoreductive nephrectomy or nephron-sparing surgery may be thought to be not safe or unfeasible in some renal cell carcinoma (RCC) patients in which tumor is locally advanced or highly complicated. Neoadjuvant therapy may reduce the volume of the tumor, thus facilitates surgery. The aim the study is to evaluate the efficacy and safety of neoadjuvant combination of pazopanib or axitinib and PD-1-activated dendritic cell-cytokine-induced killer (PD-1/DC-CIK) cell immunotherapy in those patients.MethodsData from 16 RCC patients who received neoadjuvant pazopanib (Group P, n=9) or axitinib (Group A, n=7) plus PD-1/DC-CIK cells immunotherapy were reviewed retrospectively. A total of 9 participants that were potential candidates for radical/cytoreductive nephrectomy (RN/CN) had locally advanced tumor and 5 participants with partial nephrectomy (PN) absolute indications had highly complicated tumors. The efficacy outcomes were based on volume changes of the primary tumor, lymph nodes, and tumor thrombus in 13 participants with complete computed tomography (CT) imaging. The treatment-related toxicities and surgical complications were also reported.ResultsWith a median of 2.1 months treatment, the overall volume of the tumors decreased by a median of 42.30% [interquartile range (IQR): 19.37–66.78%]. Specifically, the median reduction of tumor volume was 88.77 and 15.50 cm3 in group P and group A, respectively (P=0.014). However, participants in Group P were more likely to experience grade 3 or 4 treatment-related adverse events (AEs) than those in Group A (44.4% vs. 0). Finally, all participants were candidates for appropriate surgery after neoadjuvant therapy (as assessed by the surgeon), and 10 participants accepted surgery, including 5 PN, 4 RN/CN, and 1 lymph node dissection. A solitary participant had Clavien grade IV acute renal failure required dialysis and another had grade II lymphatic leakage.ConclusionsNeoadjuvant combination of pazopanib or axitinib and PD-1/DC-CIK cells immunotherapy was well-tolerated and could effectively reduce the volume of tumors in locally advanced or highly complicated RCC patients.  相似文献   
179.

Plastic pollution control has been on top of the political agenda in China. In January 2020, China announced a phased ban on the production and usage of various types of single-use plastics as a solution to environmental pollution problems. However, the outbreak of COVID-19 seems to be a new obstacle to the ban on single-use plastic products. To basically satisfied the daily necessities and contain the spread of SARS-CoV-2 under the background of the regular epidemic prevention and control in China, online ordering, contactless delivery and wearing mask have become an important and feasible way of daily life. However, the unrestrained use of disposable plastic bags, lunch boxes and masks within the nationwide quarantine leads to hundreds of millions of plastics wastes every day. The potential environmental pollution caused by the use of disposable plastic products during the pandemic should arouse social concern. The Chinese government should manage environmental protection in parallel with anti-pandemic endeavors as the situation of the pandemic evolves.

  相似文献   
180.
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