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   5488篇
  免费   291篇
  国内免费   23篇
耳鼻咽喉   26篇
儿科学   161篇
妇产科学   132篇
基础医学   625篇
口腔科学   177篇
临床医学   489篇
内科学   1541篇
皮肤病学   105篇
神经病学   297篇
特种医学   309篇
外科学   630篇
综合类   157篇
预防医学   269篇
眼科学   29篇
药学   403篇
  1篇
中国医学   81篇
肿瘤学   370篇
  2022年   40篇
  2021年   98篇
  2020年   56篇
  2019年   67篇
  2018年   90篇
  2017年   84篇
  2016年   72篇
  2015年   100篇
  2014年   123篇
  2013年   146篇
  2012年   240篇
  2011年   243篇
  2010年   188篇
  2009年   158篇
  2008年   230篇
  2007年   224篇
  2006年   205篇
  2005年   195篇
  2004年   201篇
  2003年   198篇
  2002年   172篇
  2001年   160篇
  2000年   139篇
  1999年   149篇
  1998年   107篇
  1997年   103篇
  1996年   96篇
  1995年   87篇
  1994年   91篇
  1993年   69篇
  1992年   107篇
  1991年   94篇
  1990年   95篇
  1989年   105篇
  1988年   90篇
  1987年   78篇
  1986年   102篇
  1985年   69篇
  1984年   57篇
  1983年   56篇
  1982年   38篇
  1981年   40篇
  1979年   48篇
  1978年   41篇
  1959年   35篇
  1958年   59篇
  1957年   87篇
  1956年   45篇
  1955年   75篇
  1954年   67篇
排序方式: 共有5802条查询结果,搜索用时 187 毫秒
151.
152.
The objective of this multicentric case-control study was to investigate if a history of autoimmune disease (AD) in first-degree relatives (FDR) is a risk factor for systemic lupus erythematosus (SLE) and to evaluate the risk of AD among FDR of SLE patients. Cases were Italian SLE patients consecutively enrolled. Controls were orthopaedic inpatients without any autoimmune diseases. The strength of the association between family history of AD and SLE was measured as an odds ratio (OR) calculated from the coefficient of an unconditional regression model. To calculate the risk of AD among FDR of SLE patients, the extended generalized estimating equation technique was used. In total, 154 SLE cases and 140 controls were enrolled. A family history of AD was reported by 22.7% of SLE patients and by 5.7% of the controls. The risk of SLE increased with the number of FDR with AD (one FDR affected, OR = 4.1; two or more, OR = 11.3). The probability of having AD was higher among FDR of SLE cases in comparison to FDR of controls (RR = 4.6; 95%CI 1.9-11.1). A female SLE patient conferred an increased risk of AD to her FDR; this risk is doubled in females (OR 10.3; 95% CI 3.1-34.4).  相似文献   
153.
Calcification of the mitral annulus is a common echocardiographic finding in the elderly, particularly in females. Calcium deposits are generally located in the posterior mitral ring, sometimes extending to the whole mitral annulus and involving the mitral valve apparatus. The present report refers to 2 patients with a very atypical mass-like calcification of the mitral annulus resembling a cardiac tumor. A detailed evaluation of the mass was obtained at transthoracic and transesophageal echocardiography; the differential diagnosis with other intracardiac masses was aided by the use of computed tomography and magnetic resonance imaging. To our knowledge there has been no prior report of such a lesion evaluated at cardiac magnetic resonance imaging.  相似文献   
154.
Postoperative acute renal failure (ARF) is not uncommon after cardiac surgery and after angiography. However, limited information exists regarding the influence of the interval between cardiac catheterization and subsequent cardiac surgery and amount of contrast agent used during this procedure on the occurrence of postoperative ARF. Data for 423 consecutive adult patients who underwent elective cardiac surgery after cardiac catheterization were examined retrospectively. The influence of interval between cardiac catheterization and cardiac surgery on postoperative ARF (defined as postoperative serum creatinine > or =2 times baseline and >2 mg/dl and/or need for renal replacement therapy) was evaluated using multivariable logistic regression. ARF occurred in 24 patients (5.7%). Median time to angiography was 2 days (interquartile range 1 to 4.5), and median dose of contrast used was 1.36 ml/kg (interquartile range 1.12 to 1.69). Surgery on the day of cardiac catheterization was independently associated with increased risk of ARF (adjusted odds ratio 3.1, 95% confidence interval 1.1 to 8.8). This risk of ARF was highest in patients who underwent surgery on the same day as angiography and with a dose of contrast higher than median (14.6%) and lowest when surgery was delayed beyond 1 day of angiography and contrast dose was median or less (2.4%; adjusted odds ratio for same-day surgery and dose higher than median 4.2, 95% confidence interval 1.2 to 14.2). Cardiac surgery performed on the day of cardiac catheterization and higher dose of contrast agent used were both independently associated with increased risk of postoperative ARF. In conclusion, these findings suggest that delaying cardiac surgery beyond 24 hours of exposure to contrast agents (when feasible) and minimizing the use of these agents have significant potential to decrease the incidence of postoperative ARF in patients undergoing elective cardiac surgery.  相似文献   
155.
Granulocyte colony-stimulating factor (G-CSF)-induced alteration of phosphoprotein during differentiation of HL-60 cells was studied. From the two-dimensional gel electrophoresis analysis of phosphoproteins, a 45 kD phosphoprotein in the cytosolic fraction of DMSO-pretreated HL-60 cells was rapidly dephosphorylated by the addition of G-CSF. This 45 kD phosphoprotein migrated into four or five spots between 4.5 and 5.5 pI. The dephosphorylation of 45 kD protein was observed within at least 10 min and reached a maximum at 60 min. Phosphoamino acid analysis showed that only serine residue of 45 kD phosphoprotein was phosphorylated, suggesting that G-CSF induced an activation of serine phosphatase. Furthermore, Staurosporine and calphostin C inhibited the phosphorylation of 45 kD protein, suggesting that protein kinase C or its downstream kinase(s) is involved in the phosphorylation of 45 kD protein. These results indicate that G-CSF causes dephosphorylation of a 45 kD cytosolic phosphoprotein which may play a role in signal transduction of G-CSF.  相似文献   
156.
The effects of dihydroergocriptine (DHECP), a dihydrogenated ergot alkaloid with dopaminergic agonistic and alpha-adrenergic antagonistic properties, were studied in 22 women with PRL-secreting microprolactinomas and compared with those recorded in 36 previously studied patients treated with bromocriptine (BRC). After acute administration of 5 mg DHECP, orally, serum PRL decreased by 61 +/- 18% (+/- SD); only 1 patient was unresponsive. The nadir was reached at 300 min. Long term treatment with increasing DHECP doses caused a progressive PRL fall from 125 +/- 142 (+/- SD) to 81 +/- 159 micrograms/L after 1 week of a 3 mg twice daily regimen, to 64 +/- 88 micrograms/L after 1 week of 5 mg twice daily, 46 +/- 57 micrograms/L after 1 week of 10 mg twice daily, and 28 +/- 34 to 33 +/- 45 micrograms/L throughout 9 months of treatment with 10 mg DHECP 3 times daily. Seventy-seven percent of patients had normal serum PRL levels during chronic treatment. All women, including those with supranormal serum PRL levels, resumed regular menses, and 16 had ovulatory cycles; 1 woman became pregnant. Galactorrhea disappeared in all. During treatment the PRL response to TRH, initially absent in all patients, became positive in 10. In 7 patients, after DHECP treatment for 9 months, high definition computed tomographic scan no longer showed the focal lesions initially seen. After drug withdrawal, serum PRL increased again in all except 1 patient. Two patients had regular menses for 6 months, and 3 still had no adenoma imaged by high definition computed tomography. In BRC-treated patients the serum PRL changes and clinical results were very similar to those in the DHECP-treated patients, except for the persistence of normal serum PRL levels in 4 patients after drug withdrawal. On the other hand, side-effects were negligible during DHECP treatment, but remarkable during BRC. Systolic and diastolic blood pressures decreased by only 5.4 and 3.0 mm Hg, respectively, after acute 5 mg DHECP administration, but decreased by 12.8 and 14 mm Hg after acute 2.5 mg BRC administration. Orthostatic hypotension and peripheral vasomotor phenomena occurred in the long term DHECP treated patients except one, but they occurred in 9 and 3 of those treated with BRC, respectively. Gastric discomfort or mild nausea occurred in 12 DHECP-treated patients, while mild or severe nausea or vomiting were observed in 18, 11, and 2 of those taking BRC, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
157.
158.
159.
BACKGROUND: Nitric oxide is an important regulator of various biological activities in human physiology, and it has been studied in the physiopathology of asthma, especially in exhaled air. OBJECTIVE: We studied the presence of NO in sera of patients with distinct degrees of asthma severity in order to determine a parameter of diagnosis and control of efficacious treatment. METHODS: We determined the presence of NO based upon the Griess reaction in the sera of 124 donors--34 controls and 90 asthmatic subjects. RESULTS: Asthmatic patients presented higher levels of nitric oxide in peripheral blood (56.54 +/- 33.37) compared to the control group (3.06 +/- 4.48). A statistically significant difference (p < 0.0001) between the nitric oxide sera levels from the two groups was demonstrated. CONCLUSION: This study demonstrates that nitric oxide sera levels can be used as an additional inflammatory marker in asthma, especially as an auxiliary diagnostic method in children where NO exhaled air analysis is difficult.  相似文献   
160.
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