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   10551篇
  免费   604篇
  国内免费   41篇
耳鼻咽喉   197篇
儿科学   302篇
妇产科学   188篇
基础医学   1430篇
口腔科学   665篇
临床医学   1072篇
内科学   1862篇
皮肤病学   319篇
神经病学   961篇
特种医学   206篇
外科学   1000篇
综合类   70篇
一般理论   6篇
预防医学   1298篇
眼科学   144篇
药学   680篇
中国医学   67篇
肿瘤学   729篇
  2023年   73篇
  2022年   106篇
  2021年   240篇
  2020年   166篇
  2019年   231篇
  2018年   267篇
  2017年   190篇
  2016年   258篇
  2015年   308篇
  2014年   394篇
  2013年   549篇
  2012年   798篇
  2011年   960篇
  2010年   486篇
  2009年   431篇
  2008年   644篇
  2007年   745篇
  2006年   676篇
  2005年   618篇
  2004年   547篇
  2003年   471篇
  2002年   436篇
  2001年   123篇
  2000年   121篇
  1999年   110篇
  1998年   79篇
  1997年   76篇
  1996年   60篇
  1995年   54篇
  1994年   51篇
  1993年   47篇
  1992年   53篇
  1991年   79篇
  1990年   53篇
  1989年   44篇
  1988年   34篇
  1987年   51篇
  1986年   40篇
  1985年   32篇
  1984年   29篇
  1983年   30篇
  1982年   25篇
  1981年   22篇
  1979年   34篇
  1977年   22篇
  1973年   20篇
  1972年   28篇
  1971年   20篇
  1969年   18篇
  1966年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Zusammenfassung Anhand von 3 Fallbeispielen aus der Spina-bifida-Ambulanz der Klinik für Kinder und Jugendliche der Universit?t Erlangen wird über die Problematik von Frakturen bei Patienten mit Meningomyelozele sowie deren Therapiekonzept berichtet. In übereinstimmung mit Literaturberichten zeigen die Kasuistiken, da? schwere Allgemeinreaktionen, lokale und systemische Entzündungsparameter und variable radiologische Befunde mit h?ufig ausgedehnter reaktiver Kallusbildung die Diagnosestellung von Frakturen bei Patienten mit Meningomyelozele, die nicht selten schmerzlos und ohne erinnerliches Trauma verlaufen, erheblich erschweren k?nnen. Differentialdiagnostisch kommen Osteomyelitis, maligne Knochentumoren und aneurysmatische Knochenzysten in Frage. Diskussion: Statische Belastung durch Geh-/ Stehtraining sowie die Verkürzung von Immobilisationsphasen stellen wichtige Faktoren in der Prophylaxe von Frakturen bei Meningomyelozyelepatienten dar. Das Therapiekonzept von Frakturen bei unserer Patientengruppe weist wesentliche Unterschiede zu den allgemeinen unfallchirurgischen und orthop?dischen Richtlinien auf.   相似文献   
142.
Purpose: The activity of 5-fluorouracil (5-FU) against colon cancer is enhanced by leucovorin and the combination of 5-FU and levamisole has activity in the adjuvant treatment of colonic malignancies. The combination of 5-FU with both leucovorin and levamisole may provide additional benefit in the treatment of colon cancer. Methods: A phase I study to assess qualitative and quantitative toxicities of this three-drug combination and to determine a dose for further phase II testing was undertaken. The role of levamisole as an immunomodulator was also assessed. Results: A group of 38 patients with incurable etastatic malignancies received 119 cycles of treatment at eight dose levels. 5-FU (375 mg/m2 per day) and leucovorin (200 mg/m2 per day) were administered intravenously (days 1–5). Levamisole was administered orally (days 1–3 and 15–17) at doses from 30 to 470 mg/m2 per day. Patients received both 5FU/leucovorin and 5-FU/leucovorin/levamisole in random order for their initial two cycles. All subsequent treatments were with the three-drug combination. Toxicities included nausea, vomiting, stomatitis, thrombocytopenia and granulocytopenia. Diarrhea was the dose-limiting toxicity at 470 mg/m2 per day levamisole. The addition of levamisole resulted in more toxicity than 5-FU and leucovorin alone. No clinical responses were seen with this regimen. The addition of levamisole resulted in more immunomodulation than 5-FU and leucovorin alone as evidenced by release of neopterin from monocytes. Conclusion: With this schedule and dose of 5-FU and leucovorin, the maximum tolerated dose of levamisole was 354 mg/m2. However, given the lack of response and the absence of dose-dependent immunomodulation, this may not be the appropriate dose for further phase 11 studies. Received: 20 October 1995 / Accepted: 16 June 1996  相似文献   
143.
Three cases of intravenous leiomyomatosis (IVL) of the uterus, a rare benign smooth-muscle tumor, are described. A preoperative diagnosis of IVL was not made in any of the patients, all of which presented with a pelvic mass with the presumptive diagnosis of leiomyoma. Surgical exploration confirmed the presence of uterine mass and two of the three cases showed extra-uterine extension into the ovarian or uterine veins. Histological examination demonstrated a fascicular pattern of bland spindle-shaped smooth-muscle cells, which extended to veins inside the myometrium or to extrauterine veins. This was confirmed by immunohistochemical stain for desmin and factor VIII. Despite their histological benignity, these lesions have a tendency to metastasize and are closely related to the conditions called “benign metastasizing leiomyoma” and “intracaval mass and cardiac extension”. The primary treatment of IVL is hysterectomy and excision of any extrauterine tumor, when technically feasible. Anti-estrogenic therapy has been suggested as potentially useful in controlling of unresectable tumor. According to the literature, the follow-up must be long and periodic postoperative ultrasonic or magnetic nuclear resonance imaging studies may be useful in detecting growth of residual intravascular tumor.  相似文献   
144.
We studied the effect of acute tryptophan depletion (ATD), which transiently reduces brain serotonin, on negative symptoms and cigarette smoking topography in schizophrenic smokers. Nicotine-dependent schizophrenics (n=11) and nonpsychiatric controls (n=8) were examined after ingesting comparable mixtures that do and do not deplete plasma tryptophan. Tryptophan-depleting and placebo mixtures were administered double-blind and in counterbalanced order. Conditions were separated by a 1-week interval. Psychopathologic symptoms (negative symptoms, depression) and smoking topography (time to first puff, number of puffs per cigarette, puff duration, interpuff interval, cigarette duration, and percentage of cigarette smoked) were measured before ingestion and again beginning 5 h after each mixture, corresponding to the time of maximal tryptophan depletion. Analyses were conducted using repeated measures analyses of variance (psychopathologic symptoms) and analyses of covariance (smoking topography) controlling for cigarette length. We found that ATD influenced smoking topography in both schizophrenics and nonpsychiatric controls in a manner suggestive of increased desire to smoke. Schizophrenics exhibited increased puff duration and decreased cigarette duration. Controls displayed increased puff duration. ATD did not produce changes in negative symptoms or depression. Compromising brain serotonin via ATD appears to intensify smoking behavior in nicotine-dependent individuals directly, rather than indirectly through changes in either mood or psychopathologic symptoms.  相似文献   
145.
The mechanisms involved in the association between air pollution and increased cardiovascular morbidity are not fully understood. The objective of this study was to test the hypothesis that fine particulate matter (PM(2.5)) induces systemic inflammation and vasoconstriction of small arteries in the lung and heart of rats. Thirty-eight healthy Wistar rats were anesthetized, intubated, and submitted to the instillation of 1 ml of distilled water diluted in the following solution: blank filter, 100 microg and 500 microg of PM(2.5). PM(2.5) was collected in glass fiber filters with a high-volume sampler. The animals were sacrificed 24 h after instillation when blood, heart, and lung samples were collected for morphological and wet-to-dry weight ratio analysis. PM(2.5) consisted of the following elements: sulphur, arsenic, bromine, chlorine, cobalt, iron, lanthanum, manganese, antimony, scandium, and thorium. Total reticulocytes significantly increased at both PM(2.5) doses (p < 0.05) while hematocrit levels increased in the 500 microg group (p < 0.05). Quantification of segmented neutrophils and fibrinogen levels showed a significant decrease, while lymphocytes counting increased with 100 microg of PM(2.5) (p < 0.05). A significant dose-dependent decrease of intra-acinar pulmonary arteriole lumen/wall ratio (L/W) was observed in PM groups (p < 0.001). Peribronchiolar arterioles L/W showed a significant decrease in the 500 microg group (p < 0.001). A significant increase in heart wet-to-dry weight ratio was observed in the 500 microg group (p < 0.001). In conclusion, fine environment particles in the city of S?o Paulo promote pulmonary and cardiac histological alterations. Pulmonary vasculature was markedly affected by particle instillation, resulting in significant vasoconstriction in healthy rats.  相似文献   
146.
The use of a ketamine-propofol combination during monitored anesthesia care   总被引:13,自引:0,他引:13  
Supplemental analgesics are commonly used to enhance analgesia and improve patient comfort during procedures performed under local anesthesia and sedation. Because the use of ketamine as an analgesic adjunct to propofol sedation has not been well established, we evaluated its impact on analgesia, sedation, and recovery after ambulatory surgery. One hundred female outpatients undergoing breast biopsy procedures under local anesthesia participated in this randomized, double-blinded, placebo-controlled study. After premedication with midazolam, 2 mg IV, patients received an infusion of a solution containing propofol (9.4 mg/mL) in combination with either placebo (saline) (Group 1) or ketamine, 0.94 mg/mL (Group 2), 1.88 mg/mL (Group 3), or 2.83 mg/mL (Group 4). The sedative infusion rate was varied to maintain a deep level of sedation (Observer Assessment of Alertness/Sedation score 4) and normal respiratory and hemodynamic functions. Sufentanil, 2.5 microg IV, "rescue" boluses were used as needed to treat patients' responses (if any) to local anesthetic infiltration or surgical stimulation. Ketamine produced a dose-dependent reduction in the "rescue" opioid requirements. However, there was an increase in postoperative nausea and vomiting, psychomimetic side effects, and delay in discharge times with the largest ketamine dosage (Group 4). The adjunctive use of ketamine during propofol sedation provides significant analgesia and minimizes the need for supplemental opioids. The combination of propofol (9.4 mg/mL)/ketamine (0.94-1.88 mg/mL) provides effective sedation/analgesia during monitored anesthesia care. IMPLICATIONS: Ketamine, when used in subhypnotic dosages, may be an useful adjuvant to propofol sedation.  相似文献   
147.
OBJECTIVES: To study HIV-positive women and women at risk of becoming infected with HIV who attended HIV prevention education group sessions at a university hospital in Brazil and to compare the use of the female condom and the male condom by these two groups of women. METHODS: The study subjects were 165 women participating in HIV prevention education group sessions at the Medical School Hospital of Ribeir?o Preto of the University of S?o Paulo, in the city of Ribeir?o Preto, S?o Paulo, Brazil. Women could be enrolled in the study from August 2000 to June 2001, and the follow-up observation time period was from August 2000 to July 2001. Male condoms and female condoms were freely distributed to all the participants at the end of each educational session and also at the end of each follow-up visit that the participants made. Each woman took part in an initial interview and was asked to return monthly. At each follow-up visit an additional short interview was carried out in order to investigate use of the male condom and of the female condom. Variables that were examined for the study included age, education, ethnic group, marital or relationship status, number of children, the women's use of male condoms and female condoms, commercial sex (whether the women had ever had sex in exchange for money, gifts, or favors), and previous knowledge of the female condom. RESULTS: The 165 women studied fell into the following three categories: 132 of them (80.0%) were HIV-positive, 26 of them (15.8%) had a sexually transmitted disease (STD) other than HIV and did not have an HIV-positive partner, and 7 of them (4.2%) had an HIV-positive partner but did not have HIV or any other STD. The women ranged in age from 15 to 64 years, with a mean of 30.3 years. Of the women in the study, 69.7% of them were married or were cohabitating, and 90.9% of them had a sexual partner. Just over two-thirds of the women had seven years of formal schooling or less. Out of 163 women, a total of 31 of them (19.0%) had never used the male condom with a partner, and 49 of the 163 (30.1%) had not used a male condom at the time of the last sexual intercourse. Out of the 165 women, 74 of them (44.8%) returned for at least one follow-up visit. Of these 74 women, 58 of them (78.3%) reported using the female condom between the initial interview and the first follow-up visit. The majority of the 74 women who returned for a visit liked using the female condom, and the women reported that their partners also generally accepted the female condom. In comparison to women at risk of HIV, HIV-positive women were more likely to have used the male condom with a partner before the initial interview. Women who continued returning over a longer follow-up period were more likely to have used the female condom at the time of the last sexual intercourse. No association was found between female condom use at the time of last sexual intercourse and the woman's HIV infection status. CONCLUSIONS: In comparison to the women at risk of HIV, the HIV-positive women in our study were more likely to use male condoms with their partners, to return for follow-up visits, and to have a longer follow-up period. The acceptance of the female condom among the HIV-positive women in this study, as reported at their first follow-up visit, appears to be similar to the acceptance of the female condom among women in general in Brazil.  相似文献   
148.
PURPOSE: The purpose of this study was to evaluate whether infusion lines are able to leach plasticizers in substantial amounts and thus be a candidate substance for hepatotoxic effects during long-term total parenteral nutrition (TPN). METHODS: TPN solutions, blood products, and selected drugs typical for preterm infants concerning amount, content, and infusion time were perfused through common polyvinylchloride (PVC) infusion lines. Concentration of diethylhexyl-phthalate (DEHP) before and after perfusion was determined by gas chromatography/mass spectrometry. RESULTS: Daily quantities of DEHP by 24-hour infusions were Lipid emulsion 20%: 10185.6 microg; aminoacid/glucose-solution: 116.2 microg; midazolaminfusion for sedation: 26.4 microg; fentanyl for sedation: 132.5 microg; propofol for sedation: 6561.0 microg. The amount of DEHP by single doses of blood products (20 mL) were packed red blood cells: 144-608 microg; platelet rich plasma: 928 microg; and fresh frozen plasma: 552-8108 microg. The dose of DEHP for a typical preterm neonate requiring TPN and additional therapy like sedation or blood products is at minimum 10 mg and can easily reach 20 mg/d. CONCLUSION: This large amount of DEHP is especially disturbing, because it effects the most vulnerable patients (neonates). Whether there is a relation to TPN-induced hepatobiliary dysfunction remains to be elucidated and is under investigation. With respect to recent literature, a biological effect of these doses must be assumed.  相似文献   
149.
OBJECTIVE: To determine the relative contribution of maternal psychological distress, maternal restraint use, and sociodemographic characteristics to the likelihood that a child would not be restrained in a motor vehicle. METHODS: We examined data on 6251 children aged 0-17 years from the 1998 National Health Interview Survey. The level of children's motor vehicle restraint use (low vs high) was examined by maternal psychological distress and motor vehicle restraint use. Multivariate regression analyses were used to model the odds of children's low use of motor vehicle restraints, controlling for potential confounders. RESULTS: According to maternal reports, more than 10% of children and nearly 13% of mothers reported low use of motor vehicle restraints. Multivariate analyses revealed that maternal use of restraints and psychological distress were both independently related to children's use of restraints, with maternal low use as the stronger correlate. Older children were more likely than younger children to be low users of motor vehicle restraints if the mother reported that she was a low user of restraints. Families with male children, black and Hispanic mothers, and 4 or more members reported lower use of restraints for their children. CONCLUSIONS: Children's low use of motor vehicle restraints was associated with low levels of maternal motor vehicle restraint use and maternal psychological distress. Moreover, maternal motor vehicle restraint practices become increasingly important as children age. Health care providers should consider maternal motor vehicle restraint use, maternal psychological distress, and child age in addition to sociodemographics when assessing children's motor vehicle safety.  相似文献   
150.
Sleep analysis is based on polysomnography. Modern polysomnographic systems are computer based. Visual and automatic analysis of sleep and respiration is supported by most computer based systems. Four functions can be distinguished in computer based polysomnography: recording, documentation during the recording, automatic and visual analysis and report generation. This review compiles the minimal requirements for digital sleep recording, documentation, analysis and reporting. The basic principles of automatic sleep analysis are reported. The requirements and the basic principles for the analysis of non-electroencephalography (EEG) signals, such as respiration, snoring, oxygen saturation, electrocardiography (ECG) and options are reported. New developments in sleep EEG processing are discussed to enlighten how computer based sleep analysis can add quantative parameters to the rules for visual sleep staging established by Rechtschaffen and Kales 30 years ago. This helps to extend our understanding of sleep.  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