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   8155篇
  免费   708篇
  国内免费   19篇
耳鼻咽喉   58篇
儿科学   388篇
妇产科学   228篇
基础医学   933篇
口腔科学   145篇
临床医学   1030篇
内科学   1404篇
皮肤病学   57篇
神经病学   726篇
特种医学   472篇
外科学   1282篇
综合类   178篇
一般理论   2篇
预防医学   749篇
眼科学   172篇
药学   555篇
中国医学   9篇
肿瘤学   494篇
  2021年   104篇
  2020年   68篇
  2019年   101篇
  2018年   138篇
  2017年   96篇
  2016年   108篇
  2015年   122篇
  2014年   153篇
  2013年   261篇
  2012年   301篇
  2011年   345篇
  2010年   190篇
  2009年   185篇
  2008年   320篇
  2007年   325篇
  2006年   345篇
  2005年   288篇
  2004年   290篇
  2003年   276篇
  2002年   267篇
  2001年   293篇
  2000年   293篇
  1999年   273篇
  1998年   171篇
  1997年   134篇
  1996年   148篇
  1995年   128篇
  1994年   117篇
  1993年   108篇
  1992年   204篇
  1991年   185篇
  1990年   192篇
  1989年   178篇
  1988年   187篇
  1987年   157篇
  1986年   175篇
  1985年   156篇
  1984年   146篇
  1983年   113篇
  1982年   85篇
  1981年   73篇
  1980年   54篇
  1979年   109篇
  1978年   73篇
  1977年   74篇
  1976年   56篇
  1975年   83篇
  1974年   74篇
  1973年   77篇
  1972年   62篇
排序方式: 共有8882条查询结果,搜索用时 0 毫秒
31.
HP 818 (1-benzoyl-6-fluoro-3-(1-methyl-4-piperidinyl)-1H-indazole) exhibits the profile of a potent nonnarcotic analgesic with neuroleptic properties. HP 818 blocks the effects of chemical (phenylquinone), pressure (tail clip), and radiant heat (tail flick) painful stimuli in mice (ED50 values of 0.3, 1.2, and 4.1 mg/kg s.c., respectively). This compound displays antinociceptive activity by the subcutaneous, oral, and intravenous routes of administration. It is also effective in the shock titration assay in squirrel monkeys and in a model of surgically induced pain. The rank order of potency of HP 818 and several other standard compounds in these tests for analgesia was Innovar > fentanyl > HP 818 > codeine > droperidol. In addition to its antinociceptive effects, HP 818 possesses neuroleptic properties. It is active in the climbing mouse, pole climb avoidance, and intracranial self-stimulation assays (ED50 values of 1.8, 1.7, and 2.5 mg/kg i.p., respectively). Moreover, HP 818 inhibits amphetamine- and apomorphine-induced stereotypy, indicative of D2-dopaminergic blocking properties. HP 818, unlike typical neuroleptic agents, does not induce supersensitivity to the effects of apomorphine when administered chronically in mice. In contrast to the clinical standard neuroleptanalgesic Innovar, HP 818 (1.0–3.0 mg/kg i.v.) produces no significant cardiovascular or respiratory changes in the anesthetized dog. Thus, HP 818 is potentially an effective presurgical medication due to its nonnarcotic analgesic activity and sedative neuroleptic effects, along with its lack of limiting cardiorespiratory side effects.  相似文献   
32.
Children who work in agriculture suffer more than 23,000 injuries and 300 fatalities on American farms every year. Using survey data collected from a random sample of working teens (ages 14 to 17) in North Carolina, the authors analyze the farm-based hazard exposure and injury experiences of teens who work on farms. The group of farmworking teens (N = 141) is 72 percent male, has a mean age of 16.6 years, and is, on average, in the 10th grade. The data show that teens working on farms in North Carolina are exposed to significant safety hazards throughout their farmworking careers. A majority of the respondents in this group of farmworkers reported exposure to tractors, large animals, all-terrain vehicles, farm trucks, and rotary mowers, and more than one-third reported exposure to pesticides and tobacco harvesters. Common reported injuries include insect stings, cuts, burns, and falls. The researchers find that gender, age, and farmwork experiences are related to variations in types of hazards to which teens are exposed and in the types of injuries they suffer. These variables also are related to the overall complexity of the teens' farmwork experiences and the burden of injury endured by teens.  相似文献   
33.
A community hospital experience of 238 instances of carcinoma of the pancreas during a 23 year period has been reviewed to see if there has been any change in survival, hospital stay, morbidity and operative strategy during the two decades included in this study as a result of improved diagnostic modalities and perioperative management. The results of this review indicate an increasing incidence of carcinoma of the pancreas in the second half of the study but also document a large number of patients whose diagnosis has been unsuspected until autopsy. The mortality for palliative bypass procedures dropped significantly in the second half of the study and provided a mean survival time of 7.6 months for this group of patients, approximately twice that of patients explored without palliation. Resectional procedures showed a very significant drop in mortality rate in the second half of the study and were used more extensively. Mean survival time of patients undergoing resectional procedures was 18.3 months with two prolonged survivors out of 22 patients. Significant operative morbidity remains a major problem and the chief cause of protracted postoperative stay and did not diminish in the second half of this study. Complications were primarily technical in nature. With this in mind, consideration should be given to concentrating the experience in pancreatic resectional operations in the hands of a limited number of surgeons within any given community.  相似文献   
34.
Obstruction of a Bjork-Shiley mitral valve prosthesis occurred in a 41 year old woman due to pannus tissue growing over the valve and impairing disc opening. The unusual intermittent nature of the obstruction was clearly demonstrated by Doppler ultrasound. The pannus was excised and the valve prosthesis replaced successfully with a Carpentier-Edwards xenograft.  相似文献   
35.
Recent advances have been made in the treatment of pancreas cancer. Specialized pancreas centres have reported an increasing rate of resections with reduced postoperative mortality. On account of the highly aggressive nature of pancreas cancer, there is a great challenge in identifying effective therapy concepts for advanced stages of the cancer as well as for the development of resection-associated measures. As large-scale, randomised, controlled studies are lacking, the additive therapy concepts after resection do not have a sufficiently scientific basis. The ESPAC-1 study, which included 600 patients, surpassed all previous studies on adjuvant therapy for pancreas cancer. This study has shown,for example, that the most promising adjuvant chemotherapy with 5-fluorouracil and folic acid leads to an equal if not better result than the multimodal regimen. This regimen can be superseded with the use of Gemcitabine, which will be evaluated in the ESPAC-3 study that includes 990 patients from various European countries including Germany, as well as from Canada and Australia. Participation in the large, phase-3 study therefore plays a key role in the continued development of the management of pancreas cancer.  相似文献   
36.
The impact of multiple donor and recipient variables on functional survival of 307 cadaveric pancreas allografts transplanted in 253 recipients at the authors' institution between July 25, 1978 and September 4, 1990 was determined using the Cox proportional hazards regression model. Relative risk of graft loss was calculated for all cases as well as for technically successful (TS) ones. Factors with an impact in descending order of significance for TS cases were immunosuppression (RR = 3.9 for double-drug versus triple-drug maintenance, p less than 0.0001); recipient category (RR = 2.4 for pancreas alone versus simultaneous pancreas/kidney, p = 0.009); retransplantation (RR = 1.8 for retransplants versus primary grafts, p = 0.007); donor hyperglycemia (RR = 1.7 for blood glucose greater than or equal to 200 versus less than 200 mg/dL, p = 0.02); human leukocyte antigen (HLA) matching (RR = 2.1 for poor versus a good match, p = 0.04). A logistic regression analysis also was performed to determine which factors predisposed to technical failure; none were identified. To make the model as relevant as possible to their current program, the authors analyzed only the bladder-drained cases (n = 221; 1984 to 1990). All patients received triple therapy. Recipient category, retransplantation, donor hyperglycemia, and degree of HLA matching remained as significant risk factors. Construction of estimated survival curves showed that the results of retransplantation were significantly improved, and the penalty incurred by using hyperglycemic donors was partially ameliorated by using well-matched donors. Because preservation times up to 30 hours did not exert an adverse effect on outcome, an argument is made to share pancreata between centers to achieve good matches.  相似文献   
37.
Does altered biomechanics cause marrow edema?   总被引:21,自引:0,他引:21  
Schweitzer  ME; White  LM 《Radiology》1996,198(3):851
  相似文献   
38.
Kupffer cells are exposed directly to a number of factors in the portal circulation that can modify or regulate their responses to septic stimuli. The gut represents a potential source of a number of these factors including endotoxin, lymphokines, and prostaglandins. We examined Kupffer cells from germfree rats and germfree rats exposed to endotoxin or bacteria via their GI tracts to determine the importance of the intestinal flora in maintaining or modulating Kupffer cell responses. Kupffer cells from germfree animals were reduced in numbers and failed to respond to LPS in Kupffer cell: hepatocyte coculture. When germfree rats were exposed to bacterial endotoxin or bacteria via the gastrointestinal tract their Kupffer cells increased in numbers to normal and the cells responded to LPS in culture. Intestinal overgrowth with Escherichia coli for 2 days activated the Kupffer cells and significantly increased Kupffer cell sensitivity to LPS. These data suggest that the environment of the gastrointestinal tract is important for normal Kupffer cell responses and that intestinal bacterial overgrowth can modify Kupffer cell responses to septic stimuli.  相似文献   
39.
40.
A number of 7-benzoylbenzofuran-5-ylacetic acids and 7-benzoylbenzothiophene-5-ylacetic acids were synthesized. The compounds were generally only 1/2 to 3 times as potent as phenylbutazone in the rat paw edema antiinflammatory assay. However, they show greater activity as analgetic agents. The most active compound is 7-[4-(methylthio)-benzoyl]benzofuran-5-ylacetic acid (5g) having 57 times the potency of aspirin in the mouse writhing analgetic assay. This compound caused virtually no gastric ulceration in rats at doses of up to 90 mg/kg.  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