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   2766篇
  免费   234篇
  国内免费   5篇
耳鼻咽喉   21篇
儿科学   101篇
妇产科学   43篇
基础医学   272篇
口腔科学   30篇
临床医学   287篇
内科学   768篇
皮肤病学   51篇
神经病学   268篇
特种医学   145篇
外国民族医学   1篇
外科学   446篇
综合类   54篇
预防医学   197篇
眼科学   24篇
药学   173篇
中国医学   3篇
肿瘤学   121篇
  2023年   13篇
  2022年   31篇
  2021年   40篇
  2020年   31篇
  2019年   56篇
  2018年   58篇
  2017年   58篇
  2016年   44篇
  2015年   90篇
  2014年   95篇
  2013年   118篇
  2012年   149篇
  2011年   140篇
  2010年   117篇
  2009年   88篇
  2008年   121篇
  2007年   116篇
  2006年   137篇
  2005年   86篇
  2004年   74篇
  2003年   78篇
  2002年   80篇
  2001年   73篇
  2000年   70篇
  1999年   74篇
  1998年   55篇
  1997年   29篇
  1996年   43篇
  1995年   37篇
  1994年   35篇
  1993年   48篇
  1992年   70篇
  1991年   53篇
  1990年   53篇
  1989年   68篇
  1988年   63篇
  1987年   40篇
  1986年   43篇
  1985年   46篇
  1984年   25篇
  1983年   40篇
  1982年   14篇
  1981年   15篇
  1980年   17篇
  1979年   28篇
  1978年   11篇
  1977年   13篇
  1976年   9篇
  1974年   10篇
  1957年   10篇
排序方式: 共有3005条查询结果,搜索用时 46 毫秒
71.
In a prospective study abdominal paracentesis with ascitic fluid aspiration was performed in 54 consecutive patients with ascites of unknown cause. The ascitic fluid was examined cytologically and bacteriologically. The total cholesterol concentration was measured with an enzymatic colorimetric method. Malignant disease was diagnosed in 34 patients. Two of them had both malignant disease and liver cirrhosis and were excluded. Seventeen patients had liver cirrhosis, one had acute pancreatitis, and two had decompensated heart disease. The diagnostic value of an ascitic cholesterol concentration greater than 1.2 mmol/l in terms of predicting malignant disease was 87.5% (95% confidence limits, 71.0-96.5). The predictive value of an ascitic cholesterol concentration less than or equal to 1.2 mmol/l in terms of benign disease was 80.0% (95% confidence limits, 56.3-94.3). It is concluded that ascitic cholesterol measurement is a valuable supplement to cytologic examination in distinguishing between ascites of malignant and benign origin.  相似文献   
72.
The surgical management of perianal Crohn's disease is complex with a wide range of operations being described. The initial emergency treatment is to drain any source of underlying sepsis. A loose seton drainage or a defunctioning stoma can then be used as a 'bridge' to definitive treatment allowing both adequate assessment of the condition and preventing further sepsis. The likelihood of success of any surgical repair must be weighed against the risk of faecal incontinence. Improved results of a local surgical repair are seen with optimal surgical and medical management of perianal Crohn's disease.  相似文献   
73.
OBJECTIVE: This randomized, double-blind study tested the hypothesis that rofecoxib, a drug that specifically inhibits cyclooxygenase 2, would cause fewer gastroduodenal ulcers than ibuprofen (in a multicenter trial), and its side effects would be equivalent to those of placebo (in a prespecified analysis combining the results with another trial of identical design). METHODS: Seven hundred seventy-five patients with osteoarthritis were randomized to receive rofecoxib at a dosage of 25 mg or 50 mg once daily, ibuprofen 800 mg 3 times daily, or placebo. Gastroduodenal ulceration was assessed by endoscopy at 6, 12, and (for active treatment) 24 weeks. The primary and secondary end points were the incidence of gastroduodenal ulcers at 12 and 24 weeks, respectively. RESULTS: Ulcers were significantly less common (P < 0.001) following treatment with rofecoxib (25 mg or 50 mg) than with ibuprofen after 12 weeks (5.3% and 8.8% versus 29.2%, respectively) or 24 weeks (9.9% and 12.4% versus 46.8%, respectively). In the combined analysis, the 12-week ulcer incidence with 25 mg rofecoxib (4.7%) and with placebo (7.3%) satisfied prespecified criteria for equivalence. CONCLUSION: At 2-4 times the therapeutically effective dose, rofecoxib caused fewer endoscopically detected ulcers than did ibuprofen. Rofecoxib at a dose of 25 mg (the highest dose recommended for osteoarthritis) satisfied prespecified criteria for equivalence to placebo.  相似文献   
74.
T O'Kelly  A Brading    N Mortensen 《Gut》1993,34(5):689-693
The aim of this study was to determine if nitric oxide (NO) is the non-adrenergic, non-cholinergic neurotransmitter, released by enteric inhibitory nerves, which mediates relaxation of the human internal anal sphincter. Isolated muscle strips were mounted for isometric tension recording in superfusion organ baths. Sodium nitroprusside, an exogenous donor of NO, relaxed the strips in a concentration dependent manner. In the presence of atropine and guanethidine, transmural field stimulation produced tetrodotoxin sensitive relaxations, which were inhibited in a dose dependent and enantiomer specific manner by antagonists of NO synthase; completely by L-nitroarginine and partially by L-N-monomethyl arginine. The effect of these antagonists was reversed by L-arginine but not D-arginine. Oxyhaemoglobin, a scavenger of nitric oxide, also abolished the relaxations but methaemoglobin had no such effect. These results strongly suggest that NO is, or is very closely associated with, the non-adrenergic, non-cholinergic neurotransmitter mediating neurogenic relaxation of the human internal anal sphincter.  相似文献   
75.

Background

Patients with chronic heart failure have vulnerable myocardial function and are susceptible to electrolyte disturbances. In these patients, diuretic treatment is frequently prescribed, though it is known to cause electrolyte disturbances. Therefore, we investigated the association between altered calcium homeostasis and the risk of all-cause mortality in chronic heart failure patients.

Methods

From Danish national registries, we identified patients with chronic heart failure with a serum calcium measurement within a minimum 90 days after initiated treatment with both loop diuretics and angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Patients were divided into 3 groups according to serum calcium levels, and Cox regression was used to assess the mortality risk of <1.18 mmol/L (hypocalcemia) and >1.32 mmol/L (hypercalcemia) compared with 1.18 mmol/L–1.32 mmol/L (normocalcemia) as reference. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated.

Results

Of 2729 patients meeting the inclusion criteria, 32.6% had hypocalcemia, 63.1% normocalcemia, and 4.3% hypercalcemia. The highest mortality risk was present in early deaths (≤30 days), with a HR of 2.22 (95% CI; 1.74-2.82) in hypocalcemic patients and 1.67 (95% CI; 0.96-2.90) in hypercalcemic patients compared with normocalcemic patients. As for late deaths (>30 days), a HR of 1.52 (95% CI; 1.12-2.05) was found for hypocalcemic patients and a HR of 1.87 (95% CI; 1.03-3.41) for hypercalcemic patients compared with normocalcemic patients. In adjusted analyses, hypocalcemia and hypercalcemia remained associated with an increased mortality risk in both the short term (≤30 days) and longer term (>30 days).

Conclusion

Altered calcium homeostasis was associated with an increased short-term mortality risk. Almost one-third of all the heart failure patients suffered from hypocalcemia, having a poor prognosis.  相似文献   
76.
A facile single-step synthesis was performed to cross-link chitosan with thiocarbohydrazide to yield thiocarbohydrazide-chitosan (TC-Cht) which was for the first time evaluated as an inhibitor for corrosion of stainless steel in 3.5% NaCl solution. A comprehensive electrochemical analysis employing electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and cyclic voltammetry (CV) was undertaken and showed that the TC-Cht acts by adsorption on the steel surface and exhibits mixed type behavior with predominantly cathodic nature. The adsorption of TC-Cht molecules on the surface of stainless steel followed the Langmuir isotherm. The TC-Cht showed a high inhibition efficiency of >94% at 500 mg L?1 concentration. Surface investigation using SEM and EDX supported the inhibitor adsorption on the steel surface.  相似文献   
77.
Catheter-associated urinary tract infections are biofilm-mediated infections that cause a significant economic and health burden in nosocomial environments. Using a newly developed murine model of this type of infection, we investigated the role of fimbriae in implant-associated urinary tract infections by the Gram-negative bacterium Klebsiella pneumoniae, which is a proficient biofilm former and a commonly isolated nosocomial pathogen. Studies have shown that type 1 and type 3 fimbriae are involved in attachment and biofilm formation in vitro, and these fimbrial types are suspected to be important virulence factors during infection. To test this hypothesis, the virulence of fimbrial mutants was assessed in independent challenges in which mouse bladders were inoculated with the wild type or a fimbrial mutant and in coinfection studies in which the wild type and fimbrial mutants were inoculated together to assess the results of a direct competition in the urinary tract. Using these experiments, we were able to show that both fimbrial types serve to enhance colonization and persistence. Additionally, a double mutant had an additive colonization defect under some conditions, indicating that both fimbrial types have unique roles in the attachment and persistence in the bladder and on the implant itself. All of these mutants were outcompeted by the wild type in coinfection experiments. Using these methods, we are able to show that type 1 and type 3 fimbriae are important colonization factors in the murine urinary tract when an implanted silicone tube is present.  相似文献   
78.
79.
With a focus directed on the potential diagnostic yield of tissue biopsy in suspected myocardial disease, transvascular endomyocardial biopsies were carried out prospectively in 130 patients. In 149 out of 153 consecutive procedures, where the number of associated major complications was less than 1%, King's bioptome and a specially designed radiopaque long introducer catheter were used. The rather thickwalled sheath had a conical tip which facilitated percutaneous entry and a preshaped distal bending which was particularly useful in the right ventricle for obtaining a steady and safe position in the direction of the interventricular septum. With respect to the histopathological information from an average of 4.2 biopsies per patient, a high clinical yield was gained in 28% of the patients, in the form of specific diagnoses and/or findings influencing subsequent therapy, and useful diagnostic information was gleaned from a further 53%. Thus, the procedure appears safe as a part of routine cardiac catheterization, and biopsy may contribute to a more accurate and clinically relevant classification of a substantial number of patients with suspected myocardial disease.  相似文献   
80.
The inhibitory effect of intravenous infusion of secretin (0.05 CU kg-1h-1) and somatostatin (60 pmol kg-1h-1), given alone or in combination, on pentagastrin-stimulated (100 ng kg-1 h-1) acid secretion was studied in 10 healthy subjects. Secretin inhibited acid secretion by 54% (p less than 0.05), and somatostatin inhibited by 70% (p less than 0.05). The combined infusion of secretin and somatostatin decreased acid output by 64% (p less than 0.05). The differences between the three groups were not significant (p greater than 0.05). Median plasma concentrations of secretin and somatostatin were of the same magnitude as seen after duodenal acidification. The present study did not demonstrate any interaction between secretin and somatostatin in the inhibition of gastric acid secretion.  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