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   1234篇
  免费   64篇
  国内免费   59篇
儿科学   45篇
妇产科学   64篇
基础医学   94篇
口腔科学   56篇
临床医学   158篇
内科学   345篇
皮肤病学   22篇
神经病学   25篇
特种医学   229篇
外科学   168篇
综合类   29篇
预防医学   40篇
眼科学   8篇
药学   38篇
中国医学   2篇
肿瘤学   34篇
  2022年   3篇
  2021年   12篇
  2020年   6篇
  2019年   4篇
  2018年   20篇
  2017年   5篇
  2016年   5篇
  2015年   21篇
  2014年   27篇
  2013年   28篇
  2012年   38篇
  2011年   50篇
  2010年   36篇
  2009年   39篇
  2008年   48篇
  2007年   73篇
  2006年   26篇
  2005年   30篇
  2004年   29篇
  2003年   24篇
  2002年   27篇
  2001年   24篇
  2000年   26篇
  1999年   22篇
  1998年   54篇
  1997年   44篇
  1996年   68篇
  1995年   50篇
  1994年   50篇
  1993年   65篇
  1992年   25篇
  1991年   19篇
  1990年   31篇
  1989年   32篇
  1988年   47篇
  1987年   38篇
  1986年   31篇
  1985年   34篇
  1984年   19篇
  1983年   12篇
  1982年   18篇
  1981年   22篇
  1980年   20篇
  1979年   9篇
  1978年   11篇
  1977年   15篇
  1976年   7篇
  1975年   9篇
  1970年   2篇
  1963年   1篇
排序方式: 共有1357条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
The influence of a low-dose combined oral contraceptive (ethinyl estradiol 30 micrograms + desogestrel 0.15 mg) on menstrual blood loss (MBL) was evaluated in 20 healthy, young women. MBL prior to commencing oral contraception was 60.2 +/- 5.6 ml (range 22-116 ml), and decreased (p < 0.001) to 36.5 +/- 5.2 ml (range 7-80 ml) and 33.7 +/- 4.1 ml (range 5-70 ml) after 3 and 6 months' oral contraceptive medication, respectively. The reduction in MBL during oral contraception was most apparent during the first two days of menstruation. Five women had an MBL > 80 ml prior to commencing oral contraceptive medication. In all of these women, MBL during the 6th menstrual period after commencing oral contraception was < 80 ml. All the women included in this study had a normal blood hemoglobin concentration, hematocrit and erythrocyte indices and there were no significant changes in these variables during the course of the study. Serum ferritin concentration prior to commencing oral contraception was 44.2 +/- 9.0 micrograms/l and was largely unchanged after 6 months' oral contraception (39.7 +/- 6.3 micrograms/l). On admission to the study, two women had a serum ferritin < 10 micrograms/l, indicative of low iron stores. Both these women had an MBL > 80 ml at the baseline assessment. Serum ferritin concentration increased during oral contraceptive medication in both women (from 8.5 micrograms/l to 12.0 micrograms/l and from 5.4 micrograms/l to 6.8 micrograms/l, respectively). The duration of menstruation (p < 0.01) and the number of women suffering from dysmenorrhea (p < 0.05) was reduced during oral contraception.  相似文献   
6.
Colonoscopy has been advocated by some investigators as the most appropriate means of screening asymptomatic patients with a positive family history of colorectal cancer. However, results of such screening have been widely disparate. The purpose of this study was to evaluate the yield of colonoscopy in a cohort of completely asymptomatic individuals with one or two first-degree relatives with a history of colorectal cancer and to compare this yield with that of colonoscopy in a group of patients with apparent anal bleeding. Patients with possible genetic disorders, such as familial polyposis, were excluded. A total of 160 asymptomatic patients and a comparison group of 137 patients with nonacute anorectal bleeding underwent colonoscopy. Colonoscopy was completed in 143 of the 160 study patients (89 percent) and in all of the comparison patients and did not result in any complications. Twenty-two adenomas were found in 17 study patients (10.6 percent); 16 of the 22 adenomas were less than 1 cm in size. In the comparison group, eight adenomas were identified (5.8 percent of patients). No cancers were identified. The difference in polyp frequency between groups was not significant. The relatively low yield of colorectal neoplasms discovered at colonoscopy in this study may in part be due to the small sample size or to the strict criteria used to define these asymptomatic patients but does not lend strong support to the notion that colonoscopy is an appropriate first step in screening the asymptomatic patient with one or two first-degree relatives with colon cancer.  相似文献   
7.
Treatment with flurbiprofen (100 mg twice a day for 5 days), tranexamic acid (1.5 gm three times a day for 3 days and 1 gm twice a day for another 2 days), and an intrauterine contraceptive device releasing 20 micrograms levonorgestrel per day was compared in women with idiopathic menorrhagia. The menstrual blood loss during two control periods in 15 women subsequently treated with flurbiprofen and tranexamic acid was 295 +/- 52 ml and 203 +/- 25.2 ml in the 16 women later fitted with a levonorgestrel-releasing intrauterine contraceptive device. Menstrual blood loss was reduced by all three forms of treatment. The reduction in menstrual blood loss expressed as a percentage of the mean of two control cycles for each form of treatment was as follows: flurbiprofen, 20.7% +/- 9.9%; tranexamic acid, 44.4% +/- 8.3%; levonorgestrel-releasing intrauterine contraceptive device after 3 months, 81.6% +/- 4.5%; levonorgestrel-releasing intrauterine contraceptive device after 6 months, 88.0% +/- 3.1%; levonorgestrel-releasing intrauterine contraceptive device after 12 months, 95.8% +/- 1.2%. The reduction in menstrual blood loss achieved by the levonorgestrel-releasing intrauterine contraceptive device was greater than that recorded with flurbiprofen (p less than 0.001) and tranexamic acid (p less than 0.01), and was greater for tranexamic acid when compared with flurbiprofen (p less than 0.05). The levonorgestrel-releasing intrauterine contraceptive device was the only form of treatment to reduce mean menstrual blood loss below 80 ml per menstruation, the upper limit of normal menstrual blood loss.  相似文献   
8.
Colorectal anastomotic stenosis results of a survey of the ASCRS membership   总被引:12,自引:5,他引:7  
Anastomotic stenosis is a poorly understood and underexamined complication of gastrointestinal surgery, reportedly most frequent in the coloproctostomy. In order to better define this problem, a questionnaire was sent to members of the American Society of Colon and Rectal Surgeons regarding patients with gastrointestinal anastomotic stenosis. A total of 123 patients with intestinal anastomotic stenosis were analyzed. Eighty-two anastomoses were stapled and 41 were handsewn. Nearly all stenoses occurred in the distal bowel (70 rectal, 23 sigmoid colon). Preoperative risk factors identified were obesity (28 patients) and abscess (12 patients). Incomplete “doughnuts” were noted in 12 patients. Postoperative anastomotic leaks (15 patients), pelvic infection (13 patients), and postoperative radiation (7 patients) were believed to be contributing factors. Dilatation, using a variety of techniques, was the sole treatment for 65 patients, however, intra-abdominal surgery was necessary in 34 patients. Large intestinal anastomotic stenosis probably occurs most commonly following coloproctostomy (both with handsewn and stapled anastomoses). Dilatation alone resulted in adequate treatment in most patients in the study. Major surgery was required to correct this problem in a significant number of patients (28 percent) in this series. The true incidence of anastomotic stenosis in colorectal surgery is unknown and warrants further study. Poster presentation at the meeting of the American Society of Colon and Rectal Surgeons, Anaheim, California, June 12 to 17, 1988.  相似文献   
9.
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.  相似文献   
10.
Goei  R; Baeten  C; Arends  JW 《Radiology》1988,168(2):303-306
Sixteen cases of histopathologically proved solitary rectal ulcer syndrome were encountered. Fifteen patients underwent barium enema study; in nine cases the findings--including rectal stricture, granularity of the mucosa, and thickened rectal folds-were nonspecific. In six cases the study was normal. All patients had a long history of defecation disorders, and defecography was performed in all. In seven cases, intussusception of the rectal wall was seen; in another case the intussusception was accompanied by a rectocele. One case showed rectal prolapse. In four cases, failed relaxation of the puborectalis occurred and prevented the passage of the bolus; in another case there was abnormal perineal descent. In two patients studies were normal. In patients with defecation disorders, the possibility of this syndrome should be considered. Defecography is the method of choice for establishing the diagnosis.  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