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   2177篇
  免费   117篇
  国内免费   76篇
耳鼻咽喉   2篇
儿科学   174篇
妇产科学   28篇
基础医学   238篇
口腔科学   58篇
临床医学   257篇
内科学   535篇
皮肤病学   74篇
神经病学   68篇
特种医学   392篇
外科学   99篇
综合类   45篇
预防医学   99篇
眼科学   19篇
药学   85篇
  2篇
肿瘤学   195篇
  2023年   5篇
  2022年   8篇
  2021年   17篇
  2020年   15篇
  2019年   16篇
  2018年   35篇
  2017年   27篇
  2016年   23篇
  2015年   44篇
  2014年   52篇
  2013年   64篇
  2012年   44篇
  2011年   44篇
  2010年   90篇
  2009年   91篇
  2008年   54篇
  2007年   95篇
  2006年   59篇
  2005年   69篇
  2004年   34篇
  2003年   23篇
  2002年   34篇
  2001年   42篇
  2000年   36篇
  1999年   34篇
  1998年   133篇
  1997年   159篇
  1996年   136篇
  1995年   109篇
  1994年   116篇
  1993年   100篇
  1992年   36篇
  1991年   41篇
  1990年   39篇
  1989年   58篇
  1988年   48篇
  1987年   45篇
  1986年   52篇
  1985年   47篇
  1984年   28篇
  1983年   16篇
  1982年   24篇
  1981年   29篇
  1980年   25篇
  1979年   4篇
  1978年   8篇
  1977年   18篇
  1976年   25篇
  1975年   14篇
  1966年   2篇
排序方式: 共有2370条查询结果,搜索用时 0 毫秒
41.
OBJECTIVE: Because survival from admission to discharge does not provide parents and physicians information about future life expectancy in the premature neonate, we characterized the actuarial survival, defined as the future life expectancy from a given postnatal age, in a large inborn population of premature infants < 30 weeks' gestation. STUDY DESIGN: We determined daily actuarial survival of 1925 inborn infants (23 to 29 weeks' gestation) admitted to the Baylor Affiliated Nurseries from July 1986 through December 1994, stratified by 100-g birth weight and by 1-week gestational-age intervals. RESULTS: In the 501- to 600-g birth weight stratum, actuarial survival improved from 31% at birth, to 61% on day of life 7, and then to 75% on day of life 28; in the 901- to 1000-g birth weight stratum, actuarial survival improved from 88%, to 94%, and then to 98% throughout the same times, respectively. Similar trends were obtained when data were stratified by gestational age. CONCLUSIONS: Survival in the smallest infants improves dramatically during the first few days of life, but there is a significant risk for late death in the smallest of these infants.  相似文献   
42.
OBJECTIVE: The ketogenic diet is a high-fat, low-protein, low-carbohydrate diet developed in the 1920s for the treatment of children with difficult to control seizures. Despite advances in both the pharmacotherapy and the surgery of epilepsy, many children continue to have difficult-to-control seizures. This prospective study sought to determine the ketogenic diet's effectiveness and tolerability in children refractory to today's medications. METHODS: One hundred fifty consecutive children, ages 1 to 16 years, virtually all of whom continued to have more than two seizures per week despite adequate therapy with at least two anticonvulsant medications, were prospectively enrolled in this study, treated with the ketogenic diet, and followed for a minimum of 1 year. Seizure frequency was tabulated from patients' daily seizure calendars and seizure reduction calculated as percentage of baseline frequency. Adverse events and reasons for diet discontinuation were recorded. RESULTS: The children (mean age, 5.3 years), averaged 410 seizures per month before the diet, despite an exposure to a mean of 6.2 antiepileptic medications. Three months after diet initiation, 83% of those starting remained on the diet and 34% had >90% decrease in seizures. At 6 months, 71% still remained on the diet and 32% had a >90% decrease in seizures. At 1 year, 55% remained on the diet and 27% had a >90% decrease in seizure frequency. Most of those discontinuing the diet did so because it was either insufficiently effective or too restrictive. Seven percent stopped because of intercurrent illness. CONCLUSIONS: The ketogenic diet should be considered as alternative therapy for children with difficult-to-control seizures. It is more effective than many of the new anticonvulsant medications and is well tolerated by children and families when it is effective.  相似文献   
43.
44.
The present study investigated the effects of dietary oltipraz on cigarette smoke-related lipophilic DNA adduct formation. Female Sprague- Dawley rats were exposed daily to sidestream cigarette smoke in a whole- body exposure chamber 6 h/day for 4 consecutive weeks. One group of rats was maintained on control diet while another group received the same diet supplemented with either a low (167 p.p.m.) or high (500 p.p.m.) dose of oltipraz, starting 1 week prior to initiation of smoke exposure until the end of the experiment. Analysis of lipophilic DNA adducts by the nuclease P1-mediated 32P-post-labeling showed up to five smoke-related adducts. Adduct no. 5 predominated in both the lung and the heart while adduct nos 3 and 2 predominated in the trachea and bladder, respectively. Quantitative analysis revealed that the total adduct level was the highest in lungs (270+/-68 adducts/10(10) nucleotides), followed by trachea (196+/-48 adducts/10(10) nucleotides), heart (141+/-22 adducts/10(10) nucleotides) and bladder (85+/-16 adducts/10(10) nucleotides). High dose oltipraz treatment reduced the adduct levels in lungs and bladder by >60%, while the reduction in lungs in the low-dose group was approximately 35%. In trachea, the effect of low and high dietary oltipraz on smoke DNA adduction was equivocal, while smoke-related DNA adducts in the heart were minimally inhibited by high-dose oltipraz. In a repeat experiment that employed a 3-fold lower dose of cigarette smoke, oltipraz (500 p.p.m.) was found to inhibit the formation of DNA adducts in rat lungs and trachea by 80 and 65%, respectively. These data clearly demonstrate a high efficacy of oltipraz in inhibiting the formation of cigarette smoke-induced DNA adducts in the target tissues.   相似文献   
45.
The variation in colorectal cancer (CRC) incidence worldwide strongly suggests a role for dietary influences. Based on epidemiological data, protective effects of vegetables and fruit intake on CRC are widely claimed, while other data indicate a possible increased CRC risk from (higher) dietary fat intake. Therefore, we have investigated single and interactive effects of dietary fat and a vegetable-fruit mixture (VFM) in the ApcMin mouse, a mouse model for multiple intestinal neoplasia. In this study, four different diets (A-D) were compared, which were either low in fat (20% energy diets A/B) or high in fat (40% energy diets C/D). In addition, 19.5% (wt/wt) of the carbohydrates in diets B and D were replaced by a freeze-dried VFM. The diets were balanced so that they only differed among each other in fat/carbohydrate content and the presence of specific plant-constituents. Because the initiation of intestinal tumors in ApcMin mice occurs relatively early in life, exposure to the diets was started in utero. Without the addition of VFM, mice maintained at a high-fat diet did not develop significantly higher numbers of small or large intestinal adenomas than mice maintained at a low-fat diet. VFM added to a low-fat diet significantly lowered multiplicity of small intestinal polyps (from 16.2 to 10.2/mouse, 15 animals/group), but not of colon tumors in male ApcMin mice only. Strikingly, addition of VFM to female mice maintained on a low-fat diet and to both sexes maintained on a high-fat diet significantly enhanced intestinal polyp multiplicity (from 16.5 to 26.7 polyps/mouse). In conclusion, our results indicate that neither a lower fat intake nor consumption of VFM included in a high-fat diet decreases the development of polyps in mice genetically predisposed to intestinal tumor development.   相似文献   
46.
47.
48.
The aim of this paper was to review the clinical applications of four-dimensional ultrasonography in the assessment of fetal behavior. With the use of a computerized database, articles on three-dimensional ultrasonography were reviewed. Several applications of dynamic three-dimensional ultrasonography have been reported, including imaging of fetal movements, facial expression and fetal hand movements. The importance of the assessment of fetal behavior by four-dimensional sonography is stressed. Four-dimensional sonography seems to be a useful imaging tool for clinical problem solving in perinatology, especially in observing the development of the central nervous system in utero.  相似文献   
49.
Carcinoma of the upper aerodigestive tract (oral cavity, oropharynx, hypopharynx, nasopharynx, larynx) are frequent tumors for which surgery and/or radiotherapy are the main therapeutic agents. The main results of meta-analyses based on the collection of individual patients data are reported: 1) The meta-analysis on chemotherapy, regrouping data of nearly 11,000 patients issued from 63 randomized trials showed an absolute benefit of 4% at five years in overall survival, in favor of chemotherapy (P<0.0001). Most of the benefit was seen with concomitant radiochemotherapy, however with a relatively large heterogeneity in this subgroup of trials. An update of this meta-analysis was performed including 24 additional trials, which confirmed the magnitude of the benefit due to concomitant chemotherapy (8% at 5 years). 2) The meta-analysis on larynx preservation, using induction chemotherapy in larynx and hypopharynx carcinomas. No significant difference was seen between the control arm with total laryngectomy and the larynx preservation approach. 3) The meta-analysis on chemotherapy in nasopharynx carcinomas, from the data of 11 randomized trials including 2722 patients, and comparing the radiotherapy to radio-chemotherapy (1979-2001). The results showed an absolute benefit of 6% at five years in overall survival, in favor of chemotherapy (P<0.0001). Most of the benefit was seen with concomitant radiochemotherapy. 4) Finally, a meta-analysis on altered fractionated RT, compared to conventional RT in 15 randomized trials regrouping 6515 patients. The results showed a small but significant improvement in favor of altered fractionated RT for overall survival and local control with an absolute benefit at five years of 3 and 6%, respectively.  相似文献   
50.
Glucocorticoid suppressible hyperaldosteronism (GSH) is an uncommon form of dominantly inherited hypertension. Presentation with hypertension and complications such as stroke in early life are well recognised. The use of a simple genetic test carried out on blood or placenta facilitates the detection of infants and children with GSH before the development of hypertension, allowing prompt treatment of hypertension if it occurs, and an opportunity to study the effects of growth and environmental influences on the progression of the condition.  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