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   1374篇
  免费   74篇
  国内免费   147篇
儿科学   70篇
妇产科学   85篇
基础医学   92篇
口腔科学   18篇
临床医学   188篇
内科学   375篇
皮肤病学   30篇
神经病学   78篇
特种医学   319篇
外科学   54篇
综合类   31篇
一般理论   2篇
预防医学   58篇
眼科学   14篇
药学   122篇
  1篇
肿瘤学   58篇
  2021年   4篇
  2020年   7篇
  2019年   13篇
  2018年   22篇
  2017年   13篇
  2016年   17篇
  2015年   20篇
  2014年   22篇
  2013年   35篇
  2012年   19篇
  2011年   26篇
  2010年   31篇
  2009年   44篇
  2008年   35篇
  2007年   122篇
  2006年   35篇
  2005年   36篇
  2004年   32篇
  2003年   24篇
  2002年   33篇
  2001年   29篇
  2000年   34篇
  1999年   33篇
  1998年   82篇
  1997年   78篇
  1996年   72篇
  1995年   65篇
  1994年   44篇
  1993年   52篇
  1992年   21篇
  1991年   32篇
  1990年   22篇
  1989年   59篇
  1988年   40篇
  1987年   41篇
  1986年   33篇
  1985年   32篇
  1984年   23篇
  1983年   16篇
  1982年   28篇
  1981年   19篇
  1980年   18篇
  1979年   14篇
  1978年   8篇
  1977年   22篇
  1976年   33篇
  1975年   23篇
  1974年   8篇
  1973年   7篇
  1970年   3篇
排序方式: 共有1595条查询结果,搜索用时 15 毫秒
101.
Whittle WL  Gibb W  Challis JR 《Placenta》2000,21(4):394-401
The amnion, a single layer of epithelial cells (EC) overlying layers of mesenchymal cells (MC) has been identified as a source of intrauterine prostaglandins (PG). The objectives of the present study were: (1) to establish a technique for the isolation and culture of pure amnion EC and MC preparations, (2) to characterize the cellular expression of PGHS-II and PGHS activity within these separated amnion cells and (3) to characterize the pattern of glucocorticoid stimulation of these separated amnion cells. Term gestation human amnion was collected after elective caesarean section or vaginal delivery. A trypsin digestion was used to isolate EC and a mechanical digestion and collagenase dispersion was used to isolate MC. Following 48 or 96 h in culture, cells were incubated for 24 h in the presence or absence of 1 microm arachidonic acid and treated with cortisol (F: 10-1000 nm) or 1 microm dexamethasone (DEX). Cell types were identified by immunohistochemistry (IHC). Immunoreactive PGHS-II (ir-PGHS-II) and glucocorticoid receptor (ir-GR) were localized by IHC. PGHS activity was measured as PGE(2)output determined by radioimmunoassay. Mean PGE(2)production by MC at 72 h was 22-fold greater (P<0.05) and at 120 h was 32-fold greater (P<0.03) than PGE(2)output by EC. Administration of arachidonic acid stimulated a 5.0-fold increase in PGE(2)output (P<0.0002) by EC after 72 h and a 3.6-fold increase (P<0.05) after 120 h but did not alter MC PGE(2)output. Despite exogenous substrate, EC PGE(2)output remained significantly less than PGE(2)output by MC. There was no difference in PG production by EC and MC with the onset of labour. Ir-GR expression was found in both EC and MC. F and/or DEX with and without arachidonic acid (AA) stimulated PGE(2)output by EC. Only DEX and not F increased PGE(2)output by MC. These data suggest that relatively pure EC and MC preparations can be established from amnion. PG output and its regulation appears to differ within these two amnion cell types, dependent upon (1) substrate availability and (2) the regulation of PGHS activity.  相似文献   
102.
Excel97在药物分析中的应用   总被引:1,自引:0,他引:1  
目的:在药物分析中,电子表格软件MicrosoftExce197for Windows。方法:利用Excel的数据处理功能,进行药物的图表绘制、数据计算和统计处理,回归分析,特别是计算分析,并可建立分析数据库。结果和结论:Excel操作简单,功能强大,数据分析工作直观。  相似文献   
103.
目的:比较国产辛伐他汀与进口辛伐他汀治疗原发性高胆固醇血症的疗效及安全性。方法:采用开放区组随机对照、多中心的临床设计。150例高胆 固醇血症病人分为验证组(50例)、对照组(48例)和开放组(52例),剂量均为每晚顿服10mg,服药8周。结果:验证组与对照组服药前后比较,血清总胆 固醇(TC)分别降低26.36%和28.3%,低密度脂蛋白胆固醇(LDL-C)分别降低33.17%和35.51%;验  相似文献   
104.
Diet and cancer prevention: the fiber first diet   总被引:3,自引:0,他引:3  
Diet can play a major role in cancer prevention. The international differences in cancer incidence are largely accounted for by lifestyle practices that include nutrition, exercise, and alcohol and tobacco use. About 50% of cancer incidence and 35% of cancer mortality in the U.S., represented by cancers of the breast, prostate, pancreas, ovary, endometrium, and colon, are associated with Western dietary habits. Cancer of the stomach, currently a major disease in the Far East, relates to distinct, specific nutritional elements such as excessive salt intake. For these cancers, information is available on possible initiating genotoxic factors, promoting elements, and prophylactic agents. In general, the typical diet in the United States contains low levels of the potent carcinogenic agents, heterocyclic amines, formed during the cooking of meats. It provides only about half the potent appropriate fiber intake and is high in calories. About twice as many calories as would be desirable come from fat, certain kinds of which enhance the development of cancers. Other foods with functional properties, such as soy products and tea, can be beneficial. To achieve reduction in risk of certain cancers, diet must be optimized, primarily to reduce caloric intake and the fat component. The latter should be 20% or less of total caloric intake and fiber should be increased to 25- 35 g per day for adults. One approach to achieving these goals is the Fiber First Diet, a diet designed around adequate fiber intake from grains, especially cereals, vegetables, legumes, and fruits, which thereby reduces both calorie and fat intake. Such dietary improvements will not only reduce cancer and other chronic disease risks, but will contribute to a healthy life to an advanced age. A corollary benefit is a lower cost of medical care.   相似文献   
105.
The short- and long-term effects of surgical procedures and chair restraint on total plasma cortisol were assessed in the chronic rhesus monkey preparation. Three nonpregnant and six pregnant animals were sampled daily, morning and evening. Fetal plasma specimens were obtained simultaneously from the pregnant animals. In the nonpregnant rhesus monkey, a circadian rhythm is present the day following venous catheterization and chair restraint, with individual values similar to those in trained, unanesthetized animals. In the pregnant animals, a postoperative rise in cortisol is followed by a gradual decline to a plateau and a return of circadian rhythm. No consistent daily fluctuations are seen in fetal cortisol, and although correlated with maternal cortisol, the exact relationship is uncertain. The data indicate that operation, as expected, is stressful but acclimation to the chair occurs.  相似文献   
106.
In a double-blind trial in 94 children attending outpatients the value of glucose or a sucrose addition to a basic electrolyte mixture for the management of acute gastroenteritis was compared. Of the children treated with added sucrose 10% failed to respond compared with 27% of those treated with added glucose. This difference was significant (P=0-05), but the time to recovery in those in the two groups who responded to treatment was not significantly different. Thus, despite theoretical advantages, there was no practical advantage in using glucose rather than sucrose. A 5% sucrose electrolyte solution with its relatively low osmolality, ready availability, and ease of preparation is recommended as the treatment of choice in the outpatient management of acute gastroenteritis in infancy.  相似文献   
107.
108.
109.
The levels of immunoreactive CRH are elevated in both maternal and fetal plasma in late gestation and labor, but fall precipitously after parturition. The major source of this peptide is thought to be the placenta. We determined if the placenta and also the amnion, chorion, and decidua produce CRH, whether this material has biological activity, and whether CRH output is modulated by glucocorticoids and progesterone. In an in vitro monolayer culture system CRH was produced by the fetal membranes and decidua. Media immunoreactive CRH concentrations averaged 625 +/- 45 (SE) pg/10(5) cells in amnion, 701 +/- 56 pg/10(5) cells in chorion, and 580 +/- 60 pg/10(5) cells in decidual tissue obtained at cesarean section. This output was similar to that by the placenta (906 +/- 121 pg/10(5) cells). These values increased in tissue obtained after spontaneous labor. A single peak of CRH immunoreactivity eluting at the same position as synthetic human CRH, and possessing biological activity, was found in all tissues. There was a dose-dependent increase in CRH output by all tissue types when cells were maintained in the presence of increasing concentrations of cortisol and dexamethasone. In contrast, increasing concentrations of progesterone decreased CRH output by all tissue types. We conclude that immuno- and biologically active CRH is produced not only in the human placenta, but also in the fetal membranes. CRH output by the placenta/fetal membranes is moderated by steroids, and changes with labor. These findings raise the possibility of a regulatory system similar to that of the hypothalamic pituitary axis, but residing within the placenta and fetal membranes.  相似文献   
110.
Park  JH; Choi  BI; Han  MC; Sung  KB; Choo  IW; Kim  CW 《Radiology》1987,163(3):619-623
In the Orient there is a high frequency of residual intrahepatic stones after biliary tract surgery. Percutaneous removal of residual intrahepatic stones was attempted in a group of 74 patients. Stones were exclusively intrahepatic in 57 patients, whereas 17 patients also had stones in the common bile duct. Biliary strictures were present in 60 cases (81%). A combination of techniques was used, including preshaped angulated catheters, irrigation-suction, balloon dilation of strictures, and crushing of large stones. In 36 cases all stones were removed and in 14 cases most stones were removed, for a success rate of 67.6%. Biliary stricture was the factor most often responsible for failure.  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