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   852篇
  免费   41篇
  国内免费   10篇
耳鼻咽喉   4篇
儿科学   26篇
妇产科学   8篇
基础医学   74篇
口腔科学   9篇
临床医学   65篇
内科学   224篇
皮肤病学   29篇
神经病学   44篇
特种医学   59篇
外科学   118篇
综合类   63篇
一般理论   1篇
预防医学   46篇
眼科学   15篇
药学   66篇
中国医学   11篇
肿瘤学   41篇
  2023年   7篇
  2022年   28篇
  2021年   36篇
  2020年   16篇
  2019年   19篇
  2018年   21篇
  2017年   12篇
  2016年   18篇
  2015年   27篇
  2014年   37篇
  2013年   46篇
  2012年   60篇
  2011年   50篇
  2010年   37篇
  2009年   38篇
  2008年   34篇
  2007年   31篇
  2006年   19篇
  2005年   36篇
  2004年   34篇
  2003年   41篇
  2002年   40篇
  2001年   15篇
  2000年   14篇
  1999年   15篇
  1998年   18篇
  1997年   19篇
  1996年   10篇
  1995年   7篇
  1994年   4篇
  1993年   4篇
  1992年   4篇
  1991年   4篇
  1990年   3篇
  1989年   7篇
  1988年   10篇
  1987年   7篇
  1986年   7篇
  1985年   7篇
  1984年   6篇
  1983年   10篇
  1982年   9篇
  1981年   3篇
  1980年   2篇
  1977年   2篇
  1975年   2篇
  1958年   11篇
  1957年   4篇
  1952年   2篇
  1951年   1篇
排序方式: 共有903条查询结果,搜索用时 15 毫秒
91.
Thallium-201/technetium-99m pertechnetate subtraction scintigraphy of the parathyroid glands was performed in a prospective study of 33 patients who had undergone bilateral neck exploration for elevated serum calcium and serum parathyroid hormone levels. In 31 cases, the Tl-201/Tc-99m subtraction technique yielded an overall sensitivity of 81%, specificity of 99%, and accuracy of 94% for identifying solitary parathyroid adenomas. Tl-201/Tc-99m subtraction scintigraphy correctly identified 73% of parathyroid adenomas weighing less than 499 mg, 79% of those weighing 500-1,499 mg, and 100% of adenomas weighing more than 1,500 mg. In a subgroup of 24 patients with solitary parathyroid adenomas who underwent both scintigraphy and high-resolution sonography, the sensitivity, specificity, and accuracy of both procedures were similar.  相似文献   
92.
Pyrimidines are aromatic heterocyclic compounds that contain two nitrogen atoms at positions 1 and 3 of the six-membered ring. Numerous natural and synthetic pyrimidines are known to exist. They display a range of pharmacological effects including antioxidants, antibacterial, antiviral, antifungal, antituberculosis, and anti-inflammatory. This review sums up recent developments in the synthesis, anti-inflammatory effects, and structure–activity relationships (SARs) of pyrimidine derivatives. Numerous methods for the synthesis of pyrimidines are described. Anti-inflammatory effects of pyrimidines are attributed to their inhibitory response versus the expression and activities of certain vital inflammatory mediators namely prostaglandin E2, inducible nitric oxide synthase, tumor necrosis factor-α, nuclear factor κB, leukotrienes, and some interleukins. Literature studies reveal that a large number of pyrimidines exhibit potent anti-inflammatory effects. SARs of numerous pyrimidines have been discussed in detail. Several possible research guidelines and suggestions for the development of new pyrimidines as anti-inflammatory agents are also given. Detailed SAR analysis and prospects together provide clues for the synthesis of novel pyrimidine analogs possessing enhanced anti-inflammatory activities with minimum toxicity.

This review sums up recent developments in the syntheses, anti-inflammatory activities, and structure–activity relationship (SAR) studies of pyrimidine derivatives.  相似文献   
93.

Exceptional precautionary measures have been adopted to stop the transmission and control of COVID-19 through the world and Pakistan is facing lockdown in this scenario. Public loyalty to precautionary measures is affected by their knowledge, attitude, risk factors and practices (KAP) towards COVID-19. The present study was conducted among the Pakistani residents to observe the knowledge, attitude, practices and risk factors towards COVID-19 outbreak in Pakistan. A questionnaire was designed, and a cross-sectional survey was conducted among participants of the study area. Participants were asked the questions regarding knowledge, attitude, practices and risk factors towards COVID-19. Data were analyzed by SPSS and t/F test and correlation was applied among the knowledge, attitude, risk factors and practices. A total of 1060 questionnaires were received. 1004 were included while 56 were excluded. The highest representation was from Punjab province (65.6%), female (63%) and age group of 21–30 years (62.1%). Most participants were single (85%), Muslim (99.4%), Urdu speaking (45.6%) and were graduates (51.5%). Most of the participants were students (52.9%) and were from economically middle-class families (40.8%). The knowledge was positively correlated with attitude and practices whereas negatively correlated with risk factors (P?<?0.05). The attitude was negatively correlated with risk factor and positively correlated with practices. The risk factors and practices were positively correlated with each other. Health education program to improve the COVID-19 knowledge, attitude, practices and risk factors should be initiated to combat current health challenge.

  相似文献   
94.
95.
BACKGROUND: Very low birthweight (VLBW) infants contribute substantially to the workload and expenditure of any neonatal unit. Earlier discharge might offer advantages to the infant, the family and the health service. AIM: To establish the outcome of preterm, VLBW infants discharged at a weight of > or = 1650 g compared with the unit's practise of discharging at a weight of > or = 1800 g. METHODS: A total of 120 infants (62 early discharges, 58 routine discharges) were followed up for 3 months after discharge from Chris Hani Baragwanath Hospital in Soweto, South Africa. The early-discharge group was discharged at > or = 1650 g and the routine-discharge group at > or = 1800 g. Growth, morbidity and mortality at 1 and 3 months after discharge were compared. RESULTS: At 3 months, the rate of weight gain (mean 30 vs 33 g/kg/day, p=0.06) and head circumference growth (38.9 vs 39.5 cm, p=0.10) were similar in both groups. There were no differences between the early- and routine-discharge groups in the number of outpatient visits (24 vs 16, p=0.18), frequency of re-admission (9 vs 4, p=0.17) or mortality [1 (1.6%) vs 3 (5.2%), p=0.27] following discharge. CONCLUSION: If home circumstances are adequate, it is as safe to discharge well, singleton VLBW infants from hospital at a weight of > or = 1650 g as at > or = 1800 g.  相似文献   
96.
PURPOSE: To establish a general methodology for quantifying streamline-based diffusion fiber tracking methods in terms of probability of connection between points and/or regions. MATERIALS AND METHODS: The commonly used streamline approach is adapted to exploit the uncertainty in the orientation of the principal direction of diffusion defined for each image voxel. Running the streamline process repeatedly using Monte Carlo methods to exploit this inherent uncertainty generates maps of connection probability. Uncertainty is defined by interpreting the shape of the diffusion orientation profile provided by the diffusion tensor in terms of the underlying microstructure. RESULTS: Two candidates for describing the uncertainty in the diffusion tensor are proposed and maps of probability of connection to chosen start points or regions are generated in a number of major tracts. CONCLUSION: The methods presented provide a generic framework for utilizing streamline methods to generate probabilistic maps of connectivity.  相似文献   
97.
98.
99.
In 22 hemodialysis patients, during a dialysis session, the solute removal index (SRI) for urea obtained from the use of a partial spent dialysate collection method was compared with that derived from the use of a total spent dialysate collection technique. The partial spent dialysate collection method was used to harvest a small representative sample of the total spent dialysate. The volumes of spent dialysate collected by the partial and the total spent dialysate collection methods were 1.7 +/- 0.4 L and 129.6 +/- 15.3 L, respectively. The total amount of urea nitrogen removed by dialysis as estimated by the partial spent dialysate collection method was similar to that determined by the total spent dialysate collection approach. As a result, the SRI value for urea obtained by the partial spent dialysate collection method (namely, 63% +/- 8%) correlated very well (r = 0.95, P < 0.001) with that derived by the total spent dialysate collection technique (namely, 62% +/- 8%). Our data suggest that it is feasible to use a simple partial spent dialysate collection method to obtain SRI results in patients treated with hemodialysis.  相似文献   
100.
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