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   12919篇
  免费   920篇
  国内免费   82篇
耳鼻咽喉   160篇
儿科学   370篇
妇产科学   383篇
基础医学   1451篇
口腔科学   600篇
临床医学   1051篇
内科学   2855篇
皮肤病学   297篇
神经病学   735篇
特种医学   393篇
外国民族医学   6篇
外科学   2022篇
综合类   363篇
一般理论   8篇
预防医学   917篇
眼科学   458篇
药学   1039篇
中国医学   66篇
肿瘤学   747篇
  2023年   168篇
  2022年   423篇
  2021年   719篇
  2020年   407篇
  2019年   535篇
  2018年   730篇
  2017年   394篇
  2016年   421篇
  2015年   452篇
  2014年   588篇
  2013年   711篇
  2012年   1042篇
  2011年   1005篇
  2010年   569篇
  2009年   460篇
  2008年   705篇
  2007年   600篇
  2006年   586篇
  2005年   576篇
  2004年   486篇
  2003年   413篇
  2002年   365篇
  2001年   133篇
  2000年   138篇
  1999年   125篇
  1998年   65篇
  1997年   61篇
  1996年   56篇
  1995年   52篇
  1994年   38篇
  1993年   33篇
  1992年   76篇
  1991年   88篇
  1990年   60篇
  1989年   68篇
  1988年   62篇
  1987年   52篇
  1986年   39篇
  1985年   35篇
  1984年   36篇
  1983年   20篇
  1982年   26篇
  1981年   19篇
  1980年   24篇
  1979年   32篇
  1978年   29篇
  1977年   19篇
  1975年   18篇
  1974年   28篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
42.
The effect of some electrolytes, nonelectrolytes, surfactants, and hydrotropic salts on the solubility of water in 1-butanol and 1-hexanol was investigated. While sodium chloride and sodium acetate decrease the solubility of water in 1-butanol, urea has no significant effect. The ionic surfactants, sodium lauryl sulfate and cetrimide, cause an initial decrease in the solubility of water in 1-butanol followed by an increase at high surfactant concentrations. The nonionic surfactant, polysorbate 20, does not show the initial decrease in water solubility. On the other hand, the hydrotropic salts, sodium benzoate, sodium salicylate, and sodium gentisate, are shown to be the best water solubilizers in 1-butanol. Sodium salicylate showed the maximum solubilizing power. The effect of sodium benzoate, sodium salicylate, and sodium lauryl sulfate on the solubility of water in 1-hexanol was also investigated. Similar results were obtained.  相似文献   
43.
Twenty-four hour urinary free cortisol and mean and integrated 13h00-16h00 plasma cortisol levels were measured in 9 patients with proven Cushing's syndrome (5 with Cushing's disease, 2 with ectopic adrenocorticotrophic hormone production due to bronchial carcinoma and 2 with adrenal adenomas) and in 21 patients without Cushing's syndrome. The 24-hour urinary free cortisol levels and mean and integrated 13h00-16h00 plasma cortisol estimations clearly distinguished patients with Cushing's syndrome from those without. However, adequate suppression on dexamethasone suppression tests (false negatives) were obtained in 3 of the 9 patients with Cushing's syndrome. Since the integrated 13h00-16h00 plasma cortisol estimation is cheaper and simpler than the mean 13h00-16h00 plasma cortisol estimation, we recommend it as an adjunct in the diagnosis of Cushing's syndrome.  相似文献   
44.
45.
Urolithiasis in Jordanian children. A report of 52 cases   总被引:3,自引:0,他引:3  
Fifty-two children with urinary calculi seen between 1975 and 1986 were reviewed. Males dominated the series. The age distribution ranged from 10 months to 14 years (mean 7.2 years); 71% presented after school age. Most patients had upper tract stones. The main presenting symptoms were abdominal pain, infection and haematuria. The causative factors or co-factors were infection, malformations and urodynamic abnormalities. Metabolic disorders were rare. Calcium oxalate and uric acid stones were found most often. Surgical management was required in 88% of patients and only 3.8% had a recurrence. Presenting symptoms are variable and so a high index of suspicion is required for diagnosis.  相似文献   
46.
Excitation functions of the reactions (nat)Sb((3)He,xn)(124,123,121)I were measured from their respective thresholds up to 35 MeV, with particular emphasis on data for the production of the medically important radionuclide (124)I. The conventional stacked-foil technique was used. From the experimental data the theoretical yields of the three investigated radionuclides were calculated. The yield of (124)I over the energy range E9(30He) = 35 --> 13 MeV amounts to 0.95 MBq/microA h. The radionuclidic impurities are discussed. A comparison of (3)He- and alpha-particle-induced reactions on antimony for production of (124)I is given. The alpha-particle-induced reaction on enriched (121)Sb and the (3)He-particle-induced reaction on enriched (123)Sb would lead to comparable (124)I yields, but the level of impurities in the latter case would be somewhat higher.  相似文献   
47.
Wilson's disease (WD) is an inherited disorder of copper metabolism yielding marked motor deficits, including a severely disabling tremor. As a structural correlate of the disease, a variety of cerebral abnormalities has been revealed. However, the relationship between motor deficits and cerebral lesions has remained largely unknown. Here, we investigated correlation between WD tremor and cerebral magnetic resonance imaging (MRI) findings. Cerebral MRI abnormalities in 6 symptomatic WD patients were compared to findings in 6 asymptomatic WD patients and 10 healthy controls. All patients were treated with long-term copper chelating therapy. Motor symptoms including tremor were determined by Unified Parkinson's Disease Rating Scale Part III (UPDRS-III). MRI findings in symptomatic WD patients revealed significant symmetric T2*-weighted hypointense signal alterations of globus pallidus, head of the caudate nucleus, and substantia nigra. In contrast, MRI of asymptomatic WD patients did not differ from healthy controls. Correlation analysis revealed a significant positive correlation between MRI basal ganglia lesions and UPDRS action tremor score. Our results demonstrate for the first time that Wilson's disease tremor is associated with lesions of the globus pallidus, the head of the caudate nucleus, and the substantia nigra.  相似文献   
48.
Background: Surgical intervention in patients with malignant hematological disorders is a major undertaking due to the expected risks of bleeding, infection and poor wound healing. Methods and materials: A retrospective study of patients treated at the Riyadh Armed Forces Hospital, Saudi Arabia between January 1991 and December 2002 was conducted. The results of patients with acute leukemia and lymphoma who underwent surgical procedures (study group) were compared with those of a control group composed of patients with the same spectrum of disorders treated over the same period of time and given the same treatment protocols but never required any surgery. Results: No single death occurred intraoperatively or in the immediate postoperative period due to surgical therapy per se. However, follow up of both groups of patients revealed a shorter long‐term survival and higher rates of relapse and severe invasive infections in the surgical group compared to the control group of patients. The mean survival for the study group was 1871 ± 307 days versus 3094 ± 279 days for the control group of patients (P = 0.0027). Thirty (75%) study patients suffered relapses of their malignant hematological disorders versus 23 (37.1%) control patients. Forty‐five relapses were encountered in the study group of patients (1.5 relapses per relapsed patient) versus 26 relapses in the control group (1.13 relapses per relapsed patient). Various infections occurred in 37 (92.5%) study patients and 32 (51.6%) control patients. Recurrent infections developed in 30 (75%) study patients and 22 (35.5%) control patients (P = 0.00008). Infections causing tissue invasion were encountered in 29 (72.5%) study patients and 22 (35.5%) control patients. Conclusion: Even major surgical procedures can be performed in patients with leukemia or lymphoma provided enough preparatory measures are made to minimize bleeding and infectious complications. Surgery may, however, be associated with long‐term complications such as a high incidence of relapse of the primary malignant hematological disorder and an increased rate of severe and invasive infections.  相似文献   
49.
50.
BACKGROUND: Knowledge about Cystic Fibrosis (CF) in Egypt is very limited. The objective of this study was to screen for CF in Egyptian children with suggestive clinical features and to identify causative genetic mutations. METHODS: Sixty-one patients from the Chest Unit, Cairo University Children's Hospital, Egypt, were included. Subjects presented with persistent or recurrent respiratory symptoms, failure to thrive, diarrhea and/or steatorrhea and unexplained persistent jaundice. Patients were screened using the CF Indicatortrade mark sweat test system (PolyChrome Medical, Inc., Brooklyn Center, MN). A quantitative sweat testing was conducted on 10 of the 12 positive patients. Seven probands and one sibling underwent molecular analysis by direct DNA sequencing of the coding region and of the intronic sequences adjacent to the 27 exons of the CFTR gene. RESULTS: Of 61 patients, 12 (20%) had positive sweat chloride screening. Ten of the 12 patients underwent quantitative sweat testing and were positive. Eight CFTR sequence changes were identified in seven affected probands and two were confirmed in one sibling by direct DNA sequencing. CONCLUSION: The study results suggest that CF is more common in Egypt than previously anticipated. Larger studies are warranted to identify the incidence, molecular basis and clinical pattern of CF in the Egyptian population.  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