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   2116篇
  免费   151篇
  国内免费   24篇
耳鼻咽喉   14篇
儿科学   46篇
妇产科学   166篇
基础医学   230篇
口腔科学   59篇
临床医学   248篇
内科学   319篇
皮肤病学   57篇
神经病学   96篇
特种医学   112篇
外科学   201篇
综合类   53篇
一般理论   3篇
预防医学   248篇
眼科学   63篇
药学   160篇
中国医学   1篇
肿瘤学   215篇
  2021年   29篇
  2020年   18篇
  2019年   34篇
  2018年   31篇
  2017年   27篇
  2016年   28篇
  2015年   22篇
  2014年   54篇
  2013年   60篇
  2012年   88篇
  2011年   116篇
  2010年   44篇
  2009年   59篇
  2008年   77篇
  2007年   112篇
  2006年   99篇
  2005年   96篇
  2004年   99篇
  2003年   89篇
  2002年   69篇
  2001年   39篇
  2000年   37篇
  1999年   46篇
  1998年   35篇
  1997年   24篇
  1996年   23篇
  1995年   27篇
  1994年   26篇
  1993年   24篇
  1992年   29篇
  1991年   36篇
  1990年   32篇
  1989年   39篇
  1988年   26篇
  1987年   45篇
  1986年   34篇
  1985年   19篇
  1984年   26篇
  1983年   33篇
  1982年   23篇
  1981年   31篇
  1980年   19篇
  1979年   26篇
  1978年   19篇
  1977年   23篇
  1976年   34篇
  1975年   27篇
  1974年   23篇
  1973年   19篇
  1970年   20篇
排序方式: 共有2291条查询结果,搜索用时 15 毫秒
1.
2.
Intratemporal vascular tumors: detection with CT and MR imaging   总被引:1,自引:0,他引:1  
The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.  相似文献   
3.
4.
LY354740 is a potent mGlu2/3 agonist with a limited oral bioavailability. Its alanyl prodrug, LY544344, showed high affinity to the intestinal peptide transporter PEPT1, and improved the oral bioavailability of LY354740 in various animal models. The aim of the present study was to investigate the mechanism of in vivo absorption of the dipeptidic prodrug LY544344. The permeabilities of LY544344 and LY354740 were examined in the rat in situ single‐pass intestinal perfusion model. The intestinal absorptive flux of LY354740 was shown to be very low in comparison with LY544344. The absorptive flux of LY544344 could best be described by a Michaelis–Menten process in parallel with a linear process. The estimated parameters were: Jmax = 26.7 × 10?5 µmol/(cm2‐s), Km = 2.6 mM. The absorptive permeability of LY544344 was reduced to approximately 5% of control in the presence of excess Gly‐Sar, a known PEPT1 substrate. Intracellular accumulation of LY354740 and LY544344, estimated postperfusion, showed high levels of LY354740 over LY544344 at all perfusate concentrations studied. However, there was a decline in the intracellular ratio of LY354740 to LY544344 at higher concentrations, suggesting that the metabolic activation to release LY354740 is saturable. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1574–1581, 2010  相似文献   
5.
Over a period of years the ventilation system of a community hospital progressively deteriorated until it no longer met regulatory guidelines. The hospital, a publicly funded military facility, requested funding to repair the ventilation system, but funds were not forthcoming because of budget austerity. When an increase in infections was documented, high-risk operations were curtailed and funding was expedited. With the new improved ventilation system the operating rooms once again met regulatory guidelines and infections returned to baseline rates. Throughout the period infections remained below recognized national levels.  相似文献   
6.
7.
8.
9.
Skin cancer is the most common malignancy in the United States accounting for more than 840,000 cases and 9,400 deaths annually. It is estimated that 90% of non-melanoma skin cancers and much of melanoma incidence can be attributed to sun exposure. The evidence suggests that regular use of sunscreen (Sun Protective Factor (SPF) of 15 or higher), wearing protective, tightly woven clothing and wide brimmed hats, and avoiding sun exposure when the ultraviolet rays are strongest (between 11:00 a.m. and 3:00 p.m.) can dramatically reduce the risk of skin cancer. Interventions to promote sun-protection behaviors that target children and adults are necessary to reduce the growing incidence rate of skin cancer in the United States.MA during the time of this research  相似文献   
10.
Blood donation behavior of Hispanics in the lower Rio Grande Valley   总被引:2,自引:0,他引:2  
WW Thompson 《Transfusion》1993,33(4):333-335
This study was designed to determine the blood donation behavior and attitudes of Hispanic residents of the Lower Rio Grande Valley for the purpose of developing promotional and educational approaches to enhance levels of donor participation. Personal interviews of 545 respondents were conducted in English and Spanish using quota sampling and standard intercept techniques at lower- and middle-income supermarkets in five cities during a payday weekend. A number of research hypotheses were established to test for demographic, behavioral, and attitudinal differences that were observed in donors and nondonors using chi-square analysis and multiple discriminant analysis. After analyzing the difference between Hispanics and non-Hispanics for blood donation rates, all non-Hispanics were eliminated from analysis, and the remaining 419 Hispanics were evaluated on the basis of their donor behavior. Donation among Hispanics was most likely to be by better- educated, English-speaking, higher-job-status individuals who had participated in a blood donation drive. Donors tend to have parent(s) who were donors, and they were also more likely to carry an organ donor card. Donors were found to vary in their behaviors as well as their attitudes and beliefs. Perceptions of a lack of safety in donating, the risk of contracting acquired immune deficiency syndrome, and the financial motivation of donors were most pronounced among Hispanics, which indicated a need for improved education on these issues.  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