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   3817篇
  免费   279篇
  国内免费   17篇
耳鼻咽喉   21篇
儿科学   147篇
妇产科学   105篇
基础医学   432篇
口腔科学   99篇
临床医学   381篇
内科学   918篇
皮肤病学   99篇
神经病学   204篇
特种医学   201篇
外科学   434篇
综合类   155篇
一般理论   5篇
预防医学   247篇
眼科学   85篇
药学   314篇
  1篇
中国医学   14篇
肿瘤学   251篇
  2023年   41篇
  2022年   111篇
  2021年   164篇
  2020年   88篇
  2019年   139篇
  2018年   186篇
  2017年   91篇
  2016年   115篇
  2015年   109篇
  2014年   156篇
  2013年   219篇
  2012年   282篇
  2011年   218篇
  2010年   161篇
  2009年   144篇
  2008年   182篇
  2007年   205篇
  2006年   214篇
  2005年   156篇
  2004年   143篇
  2003年   118篇
  2002年   89篇
  2001年   41篇
  2000年   38篇
  1999年   32篇
  1998年   44篇
  1997年   65篇
  1996年   57篇
  1995年   37篇
  1994年   41篇
  1993年   44篇
  1992年   38篇
  1991年   23篇
  1990年   28篇
  1989年   21篇
  1988年   30篇
  1987年   22篇
  1986年   21篇
  1985年   23篇
  1984年   15篇
  1983年   18篇
  1982年   18篇
  1981年   24篇
  1980年   15篇
  1979年   11篇
  1978年   8篇
  1977年   8篇
  1976年   18篇
  1975年   9篇
  1973年   9篇
排序方式: 共有4113条查询结果,搜索用时 15 毫秒
121.
In the present report, an environmentally benign magnetically recoverable nickel(ii)-based nanoreactor as a heterogeneous catalyst has been developed via a template free approach. The catalytic performance of the synthesized catalyst is assessed in the confined oxidative coupling of arenethiols with arylhydrazines to form unsymmetrical diaryl sulfides under aerobic conditions. The salient features of our protocol include oxidant- and ligand-free conditions, use of water as a green solvent, room temperature and formation of nitrogen and water as the only by-products. Moreover, a broad range of functional groups are tolerated well and provide the corresponding diaryl sulfides in moderate to good yields. Moreover, the heterogeneous nature of the catalyst permits facile magnetic recovery and reusability for up to seven runs, making the present protocol highly desirable from industrial and environmental standpoints.

An environmentally benign nickel(ii)-based magnetic nanoreactor has been developed for oxidative coupling of arenethiols with arylhydrazines to form unsymmetrical diaryl sulfides in water at room temperature.  相似文献   
122.
123.
124.
125.
Background The diagnosis of prosthetic infection remains a challenge, as no test is 100% sensitive and 100% specific Recent advances in molecular biology have enabled the detection of infection in culture negative cases.

Patients and methods We evaluated the effectiveness of polymerase chain reaction (PCR) in detecting infection in failed joint replacements prospectively in 91 consecutive patients (92 prosthetic joints) undergoing revision total hip or knee arthroplasty. Synovial fluid was collected intraoperatively and examined by broad-range PCR assay for detection of bacterial DNA. The clinical diagnosis of infection was based on the results of blood tests, preoperative joint aspiration, culture and histology of multiple intraoperative tissue samples, as well as the surgeon's assessment.

12 joints (13%) were infected, but the PCR was positive in 32 cases. The sensitivity of the technique was 92%, the specificity 74%, the accuracy 76%, the positive predictive value 34%, and the negative predictive value was 98%.

Interpretation The PCR technique cannot be recommended for the routine detection of prosthetic infection. The large number of false positive results may represent sample contamination, or bacterial presence related to low-virulence organisms, low bacterial load, or a strong host immune response.  相似文献   
126.
Choroid plexus papillomas are rare neoplasms that arise from choroid plexus epithelium. The World Health Organization classification describes three histological grades. Grade I is choroid plexus papilloma, grade II is atypical choroid plexus papilloma and grade III is choroid plexus carcinoma. Progression between grades is rare but documented. We present two adult cases, a 53-year-old female and a 70-year-old male, who demonstrated clear interval histological progression from grade I choroid plexus papilloma to higher grades.  相似文献   
127.
Soluble epoxide hydrolase (sEH) inhibitors are effective in reducing blood pressure, inflammation, and pain in a number of mammalian disease models. As most classical urea-based sEH inhibitors suffer from poor solubility and pharmacokinetic properties, the development of novel sEH inhibitors with an improved pharmacokinetic specification has received a great deal of attention. In this study, a series of amide-based sEH inhibitors bearing a phthalimide ring as the novel secondary pharmacophore (P2) was designed, synthesized, and evaluated. Docking results illustrated that the amide group as the primary pharmacophore (P1) was placed at a suitable distance from the three key amino acids (Tyr383, Tyr466, and Asp335) for an effective hydrogen bonding. In agreement with these findings, most of the newly synthesized compounds demonstrated moderate to high sEH inhibitory activities, relative to 12-(3-adamantan-1-yl-ureido)dodecanoic acid as the reference standard. Compound 12e with a 4-methoxybenzoyl substituent exhibited the highest sEH inhibitory activity, with an IC50 value of 1.06 nM. Moreover, the ADME properties of the compounds were evaluated in silico, and the results revealed appropriate predictions.  相似文献   
128.
The purposes of this study were to analyze the effects of an ERS on time to transplantation and to describe our center's experience with OLT for HB. Patients who received OLT for HB between 2000 and 2013 were included. Patient and allograft characteristics, chemotherapy regimens, and prior surgical therapies were examined. The interval between diagnosis and OLT prior to and following the institution of an ERS for transplant was compared. Survival and tumor recurrence were analyzed. Nineteen patients received OLT for HB (mean age 33 months). All children received grafts from deceased donors. Two patients underwent prior resections. Tumor recurred in four patients (21.1%). Both patients who received salvage transplants experienced post‐OLT recurrence. Three of the four recurrences occurred in spite of adjuvant chemotherapy. There were three deaths: two from metastatic disease. One‐ and five‐yr survivals were 86.1% and 73.8%. After the institution of the ERS, the mean interval between tissue diagnosis and OLT was significantly reduced. Our series of 19 patients demonstrates a 21% recurrence of HB following OLT despite chemotherapy. Five‐yr survival reached 73.8%. A system of early referral can effectively reduce times between diagnosis and transplant.  相似文献   
129.
Prostate cancer is a key health concern for men with its etiology still under investigation. Recently, the role of dietary supplements has been noted to have a major inhibitory effect on prostate cancer and numerous studies have been conducted in this regard. This review provides a summary on numerous recent studies conducted in this field. Some of the studies reviewed revealed a protective role for supplements, and others showed no correlation while some even had an adverse effect. The mechanism of how these supplements act on the prostate is still not clear. Further studies are warranted especially for supplements that have been shown to have a potential inhibitory role in prostate cancer.  相似文献   
130.
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