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   18329篇
  免费   1422篇
  国内免费   38篇
耳鼻咽喉   194篇
儿科学   717篇
妇产科学   590篇
基础医学   2820篇
口腔科学   529篇
临床医学   2127篇
内科学   3583篇
皮肤病学   421篇
神经病学   1616篇
特种医学   584篇
外国民族医学   1篇
外科学   1778篇
综合类   179篇
一般理论   13篇
预防医学   1561篇
眼科学   286篇
药学   1207篇
中国医学   16篇
肿瘤学   1567篇
  2023年   118篇
  2022年   181篇
  2021年   392篇
  2020年   329篇
  2019年   410篇
  2018年   417篇
  2017年   358篇
  2016年   419篇
  2015年   534篇
  2014年   665篇
  2013年   892篇
  2012年   1333篇
  2011年   1289篇
  2010年   804篇
  2009年   682篇
  2008年   1084篇
  2007年   1128篇
  2006年   1103篇
  2005年   1055篇
  2004年   988篇
  2003年   927篇
  2002年   854篇
  2001年   289篇
  2000年   245篇
  1999年   274篇
  1998年   226篇
  1997年   186篇
  1996年   150篇
  1995年   144篇
  1994年   113篇
  1993年   109篇
  1992年   132篇
  1991年   125篇
  1990年   123篇
  1989年   127篇
  1988年   124篇
  1987年   112篇
  1986年   110篇
  1985年   122篇
  1984年   96篇
  1983年   97篇
  1981年   54篇
  1980年   50篇
  1979年   68篇
  1978年   58篇
  1977年   61篇
  1974年   75篇
  1973年   50篇
  1972年   47篇
  1967年   45篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Background: Electrical stimulation of the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting (PONV). Neuromuscular blockade during general anesthesia can be monitored with electrical peripheral nerve stimulation at the wrist. The authors tested the effect of neuromuscular monitoring over the P6 acupuncture point on the reduction of PONV.

Methods: In this prospective, double-blinded, randomized control trial, the authors investigated, with institutional review board approval and informed consent, 220 women undergoing elective laparoscopic surgery anesthetized with fentanyl, sevoflurane, and rocuronium. During anesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the ulnar nerve (n = 110, control group) or over the median nerve (n = 110, P6 group) stimulating at the P6 acupuncture point at the same time. The authors evaluated the incidence of nausea and vomiting during the first 24 h.

Results: No differences in demographic and morphometric data were found between both groups. The 24-h incidence of PONV was 45% in the P6 acupuncture group versus 61% in the control group (P = 0.022). Nausea decreased from 56% in the control group to 40% in the P6 group (P = 0.022), but emesis decreased only from 28% to 23% (P = 0.439). Nausea decreased substantially during the first 6 h of the observation period (P = 0.009). Fewer subjects in the acupuncture group required ondansetron as rescue therapy (27% vs. 39%; P = 0.086).  相似文献   

42.
43.
BACKGROUND: Little information is available nationally about critical care units and nurses. What is known about nurses in hospitals is generally not broken down among all the specialties. OBJECTIVES: To describe issues of workforce, compensation, and care specific to critical care units and nurses who work in them. METHODS: The American Association of Critical-Care Nurses conducted a survey of randomly selected facilities with critical care units in the United States. Facilities were solicited via e-mail to respond to a survey on the World Wide Web and provide information on operations, evaluations, nursing staff reimbursement and incentives, staffing, and quality indicators. Responding facilities also provided contact information for units in the facilities. Those units were surveyed about operations, acuity systems, staffing, policies on visitation and end-of-life care, administrative structure, documentation, certification, professional advancement, vacancy/floating, staff satisfaction, orientation, association membership, wages, advanced practice nursing, and quality indicators. RESULTS: The initial response rate (120 of 658 eligible facilities) was 18.2%, and 300 of 576 solicited units nominated by the facilities responded, yielding a 52.1% response rate for the second phase. CONCLUSIONS: These survey data define the scope and intensity of services offered and provide more specific figures about staffing issues and unit practices than has been accessible before. Healthcare providers may use this information for benchmarking purposes, especially for instances in which the tables provide data for each particular type of critical care unit.  相似文献   
44.
45.
Mediastinitis is a devastating complication following median sternotomy. Continuous povidone-iodine (PVP-I) irrigation has been advocated as therapy because of its broad antimicrobial spectrum and its apparent safety. However, several recent clinical reports have warned of suspected local and systemic iodine toxicity. The purpose of this study is to determine if significant amounts of iodine can be absorbed systemically via the mediastinum, and if so, what toxicity (local and/or systemic) may result. PVP-I (0.5%) was continuously irrigated into the pericardial sacs of three dogs via catheters for 48 hr. Serial serum and urine iodine levels were determined. The serum steady-state concentration (Css), the rate elimination constant (k), the urinary clearance (Cl), and the serum half-life (t 1/2) for iodine were assessed. Serum electrolytes, Bun, Cr, and arterial pH were measured to assess systemic iodine toxicity. Tissue samples of the heart, pericardium, liver, and kidney were examined histologically for evidence of local or end-organ iodine toxicity. This study demonstrated that the absorption of iodine during continuous mediastinal irrigation with PVP-I follows zero-order pharmacokinetics, just as if it were being given by continuous intravenous infusion. The baseline serum iodine concentration was 145.9 +/- 64.3 micrograms/dl, Css was 29,290 +/- 101.4 micrograms/dl, k was 0.0996 +/- 0.009/hr, Cl was 872.4 +/- 119.3 ml/hr, and t1/2 was 6.22 hr. Urinary excretion of iodine increased in proportion to the serum iodine. Measured serum chloride increased in a linear manner (r = 0.949), while serum Na, K, Bun, Cr, and pH were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
46.
Zusammenfassung In der Zeit vom 01. Juli 1990 bis zum 30. Juni 1994 wurden 65 113 Untersuchungen au?erhalb der Regeldienstzeit durchgeführt. Die vorliegende Analyse schlüsselt die Leistungen auf nach Alter und Geschlecht im Vergleich zum Gesamtkollektiv dieser Vierjahresperiode, nach dem Zeitpunkt der Untersuchung, nach den untersuchten Organen und nach der eingesetzten Technik. Ca. 1/3 der Leistungen fallen in den Zeitraum zwischen 16.00 und 20.00 Uhr und k?nnten durch einen versetzten Tagdienst aufgefangen werden. Ein weiteres Drittel entf?llt auf den Zeitraum zwischen 20.00 und 8.00 Uhr am Folgetag. Der Rest entf?llt auf Feiertage und Wochenenden. Die h?ufigste Anforderung betrifft Thoraxaufnahmen auf den Intensivstationen. Etwa die H?lfte dieser Untersuchungen werden au?erhalb der Dienstzeit angefertigt; 17,2 % der Untersuchungen im Nacht- und Bereitschaftsdienst betreffen Computer- und Magnetresonanztomographie. Das am 01. 01. 93 in Kraft getretene Gesundheitsstrukturgesetz führte zu keinen nennenswerten Verschiebungen hinsichtlich Art, Umfang und H?ufigkeit der Untersuchungen im Nacht- und Bereitschaftsdienst. Eingegangen am 17. Juni 1996 Nach überarbeitung angenommen am 24. Juli 1996  相似文献   
47.
We determined, in monkeys, whether halothane-induced cerebrovascular dilation is mediated by beta-adrenergic receptors and whether cerebrovascular tone progressively returns to baseline values during prolonged halothane anesthesia. Total cerebral blood flow (CBF), cerebral perfusion pressure, plasma halothane concentration, and arterial blood gas tensions and pH were measured in 14 rhesus monkeys mechanically ventilated with 0.5% (inspired) halothane, 33% O2 and balance N2O. Halothane was increased to 2.0% and the measurements repeated 30 and 60 min later. Then either 0.9% NaCl (controls n = 6) or propranolol (n = 8), 1.0 mg/kg was infused intravenously over 10 min, and the measurements repeated at 70, 90, 120, and 150 min. After 30 min at 2.0% halothane, CBF increased in the controls by 50% (P less than 0.05) from 92 +/- 8 (mean +/- SD) to 137 +/- 39 ml X 100 g-1 X min-1 and in the propranolol group by 30% (P less than 0.05) from 106 +/- 33 to 137 +/- 28 ml X 100 g-1 X min-1. After 2.5 hr of 2.0% halothane anesthesia, CBF remained elevated above baseline levels, but by only 28 and 23% in the control and propranolol groups, respectively. Cerebrovascular resistance was identical in both groups (0.55 +/- 0.33 vs 0.53 +/- 0.13 mm Hg X ml-1 X 100 g 1 X min 1). The results show that there is only a 10-20% return of CBF toward baseline levels after up to 2.5 hr of 2% halothane anesthesia. The results also indicate that halothane-induced cerebrovascular dilation is not mediated by beta-adrenergic receptors.  相似文献   
48.
BACKGROUND--It is possible that many deaths from pneumonia may involve the generation of inflammatory mediators and tissue damage by activated phagocytes. To test this hypothesis phagocyte function, plasma levels of interleukin 6 (IL-6), tumour necrosis factor alpha (TNF alpha), and soluble interleukin 2 receptor (IL-2R), disease severity, and outcome have been examined in 46 patients with community acquired pneumonia. METHODS--Polymorphonuclear leucocyte (PMNL) and monocyte function were measured daily by chemiluminescence in these patients during the first week of admission, and cytokine levels were subsequently determined by ELISA. A series of 61 healthy individuals were used as a control group for the chemiluminescence results. RESULTS--There was evidence of phagocyte, particularly PMNL, activation on admission in 76% of the patients. Most patients (86%) also had raised IL-2R levels on admission. IL-6 and unbound TNF alpha were present in 23% and 41% of patients at varying times during the course of the disease. There was little correlation between measurements of cytokine or phagocyte levels and outcome or indicators of disease severity, although this may be because of the small number of patients included in this preliminary study. CONCLUSIONS--These results are consistent with the hypothesis that activated phagocyte function and raised levels of circulating cytokines may contribute to the pathogenesis of community acquired pneumonia. There are striking similarities in this respect between pneumonia, adult respiratory distress syndrome, and sepsis.  相似文献   
49.
The stimulus effects of ibogaine were compared with those of yohimbine, an alpha 2-adrenoceptor antagonist, 2,5-dimethoxy-4-methylamphetamine (DOM), a 5-hydroxytryptamine2 (5-HT2) agonist, and lysergic acid diethylamide (LSD), a nonspecific 5-HT agonist. Rats were trained with either yohimbine (6 mg/kg), DOM (0.6 mg/kg), or LSD (0.1 mg/kg) vs. no treatment in a two-lever discrimination task. Tests of generalization were then conducted with ibogaine. In yohimbine-trained animals, 39.7% of responses following ibogaine (15 mg/kg) were on the drug-appropriate lever, but this response level was not significantly different from no treatment-appropriate responding. A response distribution that was significantly different from responding under both drug and no treatment training conditions was observed in DOM-trained rats after administration of 15 mg/kg ibogaine. Pizotyline (BC-105) blocked all DOM-appropriate responding produced by ibogaine. In LSD-trained animals, 20 mg/kg ibogaine mimicked LSD. Pizotyline blocked LSD-appropriate responding produced by ibogaine in five of six animals. The present data suggest the involvement of 5-HT2 receptor activity, and the possibility of a 5-HT1A contribution, in the stimulus properties of ibogaine.  相似文献   
50.
The dissolution rates of sparingly soluble, fine particulate, suspended drugs have been studied using a Coulter Counter Model TAII. For two sieve fractions of oxazepam the dissolution rates were monitored in media with varying viscosities brought about by the addition of glycerol, while for griseofulvin the change in the medium's viscosity was induced by changing the temperature. By calculating the dissolution rate, and compensating for differences in particle surface area and media solubility, it was shown that the dissolution rate was diffusion controlled. After additional normalization for the diffusion coefficient, it was suggested that the so-called apparent diffusional distance decreased substantially with particle size. The effect of particle size was more limited above approx. 15 μm.  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