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   4950篇
  免费   578篇
  国内免费   20篇
耳鼻咽喉   72篇
儿科学   115篇
妇产科学   88篇
基础医学   625篇
口腔科学   99篇
临床医学   512篇
内科学   1002篇
皮肤病学   140篇
神经病学   443篇
特种医学   297篇
外科学   725篇
综合类   159篇
现状与发展   30篇
一般理论   1篇
预防医学   605篇
眼科学   48篇
药学   277篇
中国医学   3篇
肿瘤学   307篇
  2023年   190篇
  2022年   38篇
  2021年   53篇
  2020年   75篇
  2019年   68篇
  2018年   97篇
  2017年   85篇
  2016年   86篇
  2015年   103篇
  2014年   154篇
  2013年   149篇
  2012年   149篇
  2011年   162篇
  2010年   163篇
  2009年   151篇
  2008年   157篇
  2007年   200篇
  2006年   145篇
  2005年   164篇
  2004年   138篇
  2003年   150篇
  2002年   145篇
  2001年   109篇
  2000年   123篇
  1999年   137篇
  1998年   83篇
  1997年   86篇
  1996年   92篇
  1995年   84篇
  1994年   67篇
  1993年   72篇
  1992年   93篇
  1991年   106篇
  1990年   102篇
  1989年   109篇
  1988年   93篇
  1987年   97篇
  1986年   84篇
  1985年   82篇
  1984年   61篇
  1983年   66篇
  1982年   42篇
  1981年   46篇
  1980年   42篇
  1979年   69篇
  1978年   46篇
  1977年   42篇
  1976年   56篇
  1975年   47篇
  1973年   42篇
排序方式: 共有5548条查询结果,搜索用时 15 毫秒
1.
2.
3.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence.  相似文献   
4.
5.
6.
Efficient high-frequency body coil for high-field MRI.   总被引:1,自引:0,他引:1  
The use of body coils is favored for homogeneous excitation, and such coils are often paired with surface coils or arrays for sensitive reception in many MRI applications. While the body coil's physical size and resultant electrical length make this circuit difficult to design for any field strength, recent efforts to build efficient body coils for applications at 3T and above have been especially challenging. To meet this challenge, we developed an efficient new transverse electromagnetic (TEM) body coil and demonstrated its use in human studies at field strengths up to 4 T. Head, body, and breast images were acquired within peak power constraints of <8 kW. Bench studies indicate that these body coils are feasible to 8 T. RF shimming was used to remove a high-field-related cardiac imaging artifact in these preliminary studies. P41RR13230  相似文献   
7.
8.
Monitoring the performance of the health care delivery system is a public health function that becomes more important as organized delivery systems begin to take control over larger portions of the medical care market. The study reported here illustrates how standard medical care epidemiology can be applied to analysis of health care system performance to aid governmental efforts to monitor new developments in the medical care market. In order to evaluate the efficiency of hospital care delivered in Iowa, age- and sex-adjusted population admission rates for five common procedures were generated for all 99 counties. The five common procedures were defined as follows: hernia, tonsillectomy, cesarean section, hysterectomy, and cholecystectomy. In addition, variations in 11 ambulatory care-sensitive condition rates were analyzed. Residents of at least 15 counties were at significantly greater than average risk of receiving each of the common procedures (chi 2 test, P < 0.05). Counties that had a high rate for one procedure tended to have a high rate for at least one other procedure. Several counties had more than twice the mean rate. Even a 10% reduction, when added across all five common procedures. amounts to well over 2,000 hospitalizations avoided. It is assumed that reductions would be concentrated in high-rate counties. If a 50% reduction could be achieved in only part of the ambulatory care-sensitive procedures, more than 10,000 hospital admissions could be avoided.  相似文献   
9.
10.
Platelet activating factor (PAF) and thromboxane A2 (TxA2) are two vasoactive mediators which can decrease renal blood flow. Both are synthesized by various intrarenal cell types or by macrophages which may infiltrate the kidney during unilateral ureteral obstruction (UUO). In several experimental systems, PAF receptor activation is accompanied by TxA2 release; pharmacological modification of TxA2 synthesis or receptor activation modulates the response to PAF. The involvement of PAF in UUO has not been studied previously, and the role of TxA2 has not been clearly defined by previous investigations. The hemodynamic response to acute UUO is characterized by decreases in renal blood flow (RBF) and glomerular filtration rate and an acute increase in ureteral pressure. In the present experiments, the involvement of either PAF or TxA2 in the acute response to UUO was studied by determining if blockade of either the TxA2 or PAF receptor would affect the renal hemodynamic response to UUO. In addition, the effect of blockade of the TxA2 receptor on the renal response to PAF was determined. Our results indicate that only a small portion of the renal response to PAF is mediated by TxA2, and that neither PAF nor TxA2 can be implicated in the acute hemodynamic response to UUO. TxA2 or PAF involvement in the chronic response to UUO still remains to be determined.  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