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   601787篇
  免费   44335篇
  国内免费   16729篇
耳鼻咽喉   6424篇
儿科学   12391篇
妇产科学   13431篇
基础医学   77936篇
口腔科学   12157篇
临床医学   64486篇
内科学   112618篇
皮肤病学   8452篇
神经病学   45086篇
特种医学   20655篇
外国民族医学   110篇
外科学   80299篇
综合类   41980篇
现状与发展   48篇
一般理论   395篇
预防医学   44649篇
眼科学   15798篇
药学   50458篇
  170篇
中国医学   11963篇
肿瘤学   43345篇
  2023年   5049篇
  2022年   11442篇
  2021年   17552篇
  2020年   12046篇
  2019年   13678篇
  2018年   15214篇
  2017年   12366篇
  2016年   12582篇
  2015年   17017篇
  2014年   22721篇
  2013年   25647篇
  2012年   38353篇
  2011年   41114篇
  2010年   24190篇
  2009年   20488篇
  2008年   32112篇
  2007年   33280篇
  2006年   32646篇
  2005年   32394篇
  2004年   27325篇
  2003年   25049篇
  2002年   22953篇
  2001年   14347篇
  2000年   14188篇
  1999年   14024篇
  1998年   8349篇
  1997年   7448篇
  1996年   5828篇
  1995年   5484篇
  1994年   4710篇
  1993年   3803篇
  1992年   7076篇
  1991年   6778篇
  1990年   6075篇
  1989年   5799篇
  1988年   5496篇
  1987年   5215篇
  1986年   4838篇
  1985年   4542篇
  1984年   3660篇
  1983年   3225篇
  1982年   2527篇
  1981年   2297篇
  1980年   2086篇
  1979年   2826篇
  1978年   2066篇
  1975年   1742篇
  1974年   1942篇
  1973年   1904篇
  1972年   1772篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Seronegative hepatitis is a common cause of acute liver failure (ALF) requiring liver transplantation. The primary aim of this study was to examine outcomes following transplantation in this group and to identify factors associated with early (<2 months) mortality. Patients studied were 110 consecutive cases of seronegative ALF transplanted at the Queen Elizabeth Hospital, Birmingham, between January 1992 and January 2004. Univariate analysis of 44 pretransplantation recipient, donor, and operative variables was performed initially to identify factors associated with early posttransplantation mortality. Variables identified as significant or approaching significance were analyzed using stepwise multiple logistic regression analysis. Survival following transplantation for seronegative hepatitis was 83%, 81%, and 73% at 2, 12, and 60 months, respectively. The majority (71%) of deaths occurred within the 1st 2 months and sepsis / multiorgan dysfunction was the most common cause of early death. Univariate analysis revealed 9 variables predicting early death. Subsequent multivariate analysis identified high donor body mass index (BMI; a possible surrogate marker for hepatic steatosis) as the most important predictor of early death (P = .009; odds ratio, 1.2; 95% confidence interval, 1.0-1.3). Recipient age >50 (P = .015; odds ratio, 4.2; 95% confidence interval, 1.3-14.1) and non-Caucasian recipient ethnicity (P = .015; odds ratio, 4.9; 95% confidence interval, 1.2-19.2) were other variables associated with early death on multivariate analysis. This study specifically examined factors that determine the early outcome of transplanted seronegative ALF patients. In conclusion, we found that donor and recipient factors identify patients who have a high chance of early death after transplantation.  相似文献   
993.
BACKGROUND AND PURPOSE: Uterine cramping pain is related to prostaglandins, which are mediated by cyclooxygenase. However, it is unknown whether the analgesic effects of the non-selective cyclooxygenase inhibitor tenoxicam are different between primiparous and multiparous women. This placebo-controlled, double-blind study compared the analgesic effect of tenoxicam on post-cesarean uterine cramping pain in primiparous and multiparous women. METHODS: Forty primiparous women and 40 multiparous women who were scheduled for elective cesarean delivery were allocated into the following 4 groups: saline-primipara (SP) group, tenoxicam-primipara (TP) group, saline-multipara (SM) group, and tenoxicam-multipara (TM) group. Saline or 20 mg tenoxicam was intravenously injected immediately after clamping of the umbilical cord. All patients received patient-controlled analgesia for postoperative pain control. Resting wound pain, uterine cramping pain, morphine consumption, and morphine-related side effects were evaluated at 4 and 24 hours after surgery. RESULTS: At 24 hours after surgery, tenoxicam-related relief of uterine cramping pain was 2.1 in primiparous women (visual analog scale: SP 5.6 (4.4-6.8) minus TP 3.5 (2.2-4.9); p < 0.01). The tenoxicam-related morphine-sparing effect was 14 mg (45%) in primiparous women (SP 31.4 mg (23.9-38.8) minus TP 17.4 mg (11.6-23.2); p < 0.01). The tenoxicam-related relief of uterine cramping pain and tenoxicam-related morphine-sparing effect were not significant in multiparous women. CONCLUSIONS: This study revealed that the analgesic effect of tenoxicam on post-cesarean uterine cramping pain is greater in primiparous women than in multiparous women. Further studies are required to determine whether a higher dosage of tenoxicam is beneficial to reduce uterine cramping pain in multiparous women.  相似文献   
994.
995.
PURPOSE: Postoperative nausea and vomiting (PONV) is the most common postoperative complication after surgery and general anesthesia. PONV occurs primarily within the first 24 hours and can lead to significant morbidity, delayed hospital discharge, increased hospital costs and perhaps most importantly, poor patient satisfaction. We sought, in this study, to determine the prevalence of PONV and to identify risk factors in patients who underwent orthognathic surgery. PATIENTS AND METHODS: We conducted a retrospective cross-sectional analytic survey of 553 consecutive patients over 14 years of age, who underwent maxillary and/or mandibular osteotomies at Kaiser Permanente Hospital (Oakland, CA), between January 2003 and March 2004. Patient-, anesthesia- and surgery-related factors that were considered to have a possible effect on the prevalence of PONV events were evaluated. RESULTS: A total of 514 patients met the inclusion criteria. Among these patients, 40.08% experienced PONV during the first 24 hours after surgery. The most important predictive factors associated with an increased risk of PONV were female gender, young patients (15 to 25 years old), nonsmoking status, presence of predisposing factors (ie, prior history of motion sickness and/or PONV, vertigo or migraine headaches), use of volatile general anesthetics, maxillary surgery, postoperative pain level (PACU) and the use of postoperative analgesic opioid drugs. We found a directly proportional relationship between the number of risk factors and the prevalence of PONV. CONCLUSION: We found PONV had a high prevalence among patients undergoing orthognathic surgery. Further studies are needed to develop effective protocols for preventing this common and unpleasant problem.  相似文献   
996.
目的分析胸部X线及CT影像征象在支气管结核临床诊断中的价值和意义。方法收集本院经病理及电子支气管镜证实为支气管结核105例,对照其胸部X线与CT表现进行回顾性分析。结果105例患者中,胸部X线显示伴有肺内结核灶77例,气管狭窄、肺叶不张分别为51例和49例,未见异常表现17例。胸部CT扫描对气管狭窄及肺叶不张检出率明显提高,分别为72例和61例,且能观察到气管内壁情况及狭窄或阻塞后肺野情况,伴肺内结核灶79例,无异常改变只有8例。结论提高对支气管结核的影像学认识,能有效地提高临床诊断准确率。  相似文献   
997.
998.
999.
Whereas water loss in land living animals occurs continuously, water intake takes place discontinuously. At the normal operating set point of plasma osmolality, urine is more concentrated than plasma due to secretion of vasopressin. Thus animals operate around a state of mild dehydration. As water loss occurs, the severity of dehydration and thirst increase in intensity and at some point water intake occurs. Sufficient water is consumed to return plasma osmolality to the normal operating set point. Food intake and water balance are interdependent as food provides the osmoles which determine obligatory renal solute excretion. When dry food with the same osmotic content was substituted for canned food (water content 74%), dogs increased water intake from 24.2 +/- 4.3 to 62.2 +/- 8.8 ml/kg. Urine output and urine osmolality were unchanged, as under conditions of normal hydration, near maximal urine concentration is achieved. Changing water intake is the only available variable to maintain water balance. During water deprivation, the major renal mechanism appears to be natriuresis. In rehydration, satiety mechanisms ensure appropriate water intake and renal sodium conservation restores sodium balance.  相似文献   
1000.
PURPOSE: Titanium plates and monocortical screws are commonly used to stabilize the mandible following sagittal split ramus osteotomies. Despite widespread use of this type of fixation, there is a paucity of large studies evaluating the infection rate and need for hardware removal. MATERIALS AND METHODS: This study is a retrospective cohort evaluation of 1,066 consecutive mandibular sagittal ramus osteotomies in 533 patients, performed between January 2002 and December 2003. All osteotomies were stabilized with 4-hole miniplates and 2.0 mm x 5.0 mm monocortical screws. Study variables included disturbances of wound healing, age, gender, plate and screw position, direction of mandibular movement, adjunctive procedures performed, and the patient's medical history. Data were collected by chart and radiographic review. The above variables were analyzed using Fisher's exact test, Chi-square, Cochran-Armitage Trend Test, and multiple logistic regression. RESULTS: Of 533 patients 26% (138) demonstrated wound healing problems. This occurred in 15% of all 1,066 osteotomy sites. 6.5% of plates required removal in 10% of patients. In no case did disturbance of wound healing or plate removal result in non-union or relapse of the osteotomy. Wound healing problems were fewer when mandibular osteotomies were done in conjunction with maxillary surgery (18.9% versus 29.1%). Disturbances of wound healing were not related to the direction of movement of the mandible and were lower when hardware was placed closer to the inferior border. CONCLUSION: An overall low incidence (6.5%) of hardware infection requiring plate removal was found in this study. Screw proximity to the osteotomy site did not correlate with higher rates of healing problems, but there was a statistically significant trend of fewer disturbances of healing when the hardware was placed closer to the inferior border of the mandible.  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