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   15818篇
  免费   1292篇
  国内免费   51篇
耳鼻咽喉   287篇
儿科学   527篇
妇产科学   399篇
基础医学   2325篇
口腔科学   346篇
临床医学   1247篇
内科学   3352篇
皮肤病学   220篇
神经病学   1708篇
特种医学   495篇
外科学   2256篇
综合类   304篇
一般理论   12篇
预防医学   1330篇
眼科学   375篇
药学   1147篇
中国医学   11篇
肿瘤学   820篇
  2022年   160篇
  2021年   292篇
  2020年   134篇
  2019年   242篇
  2018年   252篇
  2017年   196篇
  2016年   197篇
  2015年   247篇
  2014年   381篇
  2013年   612篇
  2012年   819篇
  2011年   870篇
  2010年   509篇
  2009年   420篇
  2008年   842篇
  2007年   894篇
  2006年   902篇
  2005年   921篇
  2004年   913篇
  2003年   917篇
  2002年   848篇
  2001年   219篇
  2000年   183篇
  1999年   214篇
  1998年   191篇
  1997年   164篇
  1996年   159篇
  1995年   161篇
  1994年   163篇
  1993年   139篇
  1992年   213篇
  1991年   183篇
  1990年   174篇
  1989年   187篇
  1988年   184篇
  1987年   136篇
  1986年   188篇
  1985年   195篇
  1984年   191篇
  1983年   178篇
  1982年   171篇
  1981年   190篇
  1980年   169篇
  1979年   115篇
  1978年   152篇
  1977年   102篇
  1976年   124篇
  1975年   128篇
  1974年   102篇
  1973年   108篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
This paper describes the results of the application of linear solvation energy relationships (LSERs) to quantitatively characterize the properties of adhesives and to evaluate the degree of drug-adhesive interaction in transdermal drug delivery formulations. Probe solutions were prepared in acetonitrile (ACN) for a set of probe compounds with different physicochemical properties, and were used to swell the adhesives for subsequent probe molecule-adhesive interactions. The degree of the interactions was measured by the 'sorbed' amount of probe molecules. Based on LSERs, the 'sorbed' amounts were linearly correlated with their properties. The corresponding coefficients reflect the differential interactions of these molecules with the adhesive and ACN, and are quantitative indications of the adhesive properties. Two different transdermal acrylate adhesives (isooctyl acrylate/acrylamide/vinyl acetate in the weight ratios of 75/5/20 and isooctyl acrylate/2-hydroxyethyl acrylate/vinyl acetate in the weight ratios of 58/20/18) were selected for the evaluation of the methodology. It is concluded that the first adhesive is more basic and hydrophobic, which is consistent with the use of acrylamide monomer and significant amount of isooctyl acrylate. The second adhesive is more acidic and polarizable due to a relatively high amount of the 2-hydroxyethyl acrylate. Additionally, the 'sorbed' amount can be regarded as an interaction parameter or index between a drug molecule and the adhesive. Finally, this parameter is expected to correlate with the thermodynamic properties of transdermal formulations such as drug solubility, diffusion coefficient, release rate, and maybe skin permeation rate.  相似文献   
62.
Cocaine abuse is often associated with behavior that takes into account short-term, but not long-term consequences. However, there has been no empirical research concerning the effects of cocaine on self-control (choice of a larger, more delayed reinforcer over a smaller, less delayed reinforcer). In the present research, when food-deprived rats repeatedly chose between a larger, more delayed food reinforcer and a smaller, less delayed food reinforcer, chronic intraperitoneal injections of 15 mg/kg cocaine (but not 10 mg/kg fluoxetine) decreased the rats' choices of the larger, more delayed reinforcer. Cocaine can decrease rats' self-control.  相似文献   
63.
We evaluated the possible genetic contribution to hyperinsulinism in a series of patients seen during the past 15 years. Of 26 families, 5 (19%) had more than one child affected (multiplex family). There were no apparent differences between patients in the 5 multiplex and 21 simplex families, clinically, biochemically, or on histologic examination of the pancreatic specimens. The families studied had a total of 63 offspring; the 26 index patients had 37 siblings, 6 of whom were affected. After four patients with hyperinsulinism caused by adenoma were excluded from the study, segregation analysis was carried out to test the data for agreement with results expected if familial and isolated hyperinsulinism represented a single disease with recessive mode of inheritance and a segregation ratio of 0.25. Excellent agreement was found between the observed number of affected siblings (20) and the expected number (19.65), with a segregation ratio of 0.254. The results were consistent with the hypothesis that in most or all cases, hyperinsulinism is inherited as an autosomal recessive disease. There was no evidence of distinct familial and sporadic types.  相似文献   
64.
The rare teratoma of the placenta has been compared to the fetus amorphus, two distinguishing characteristics being the teratoma's lack of structural organization and lack of large vessels entering the tumor. A case of placental teratoma and theories of origin are discussed.  相似文献   
65.
Alternative treatments such as troleandomycin methotrexate, gold, and intravenous gamma globulin are sometimes considered for severe asthmatics to minimize the need for systemic corticosteroids and reduce adverse effects. These alternative therapies may also be associated with significant toxicity and expense. The ability to reduce corticosteroid use and the need for alternative treatment interventions in 125 pediatric patients at our institution were reviewed. Because corticosteroid requirements were reduced significantly, only 23 of 125 children evaluated were considered for treatment alternatives with only 10 receiving such therapy. This study emphasizes the importance of a thorough and comprehensive review of corticosteroid requirements and usage prior to initiating alternative approaches to treatment in moderate to severe asthmatics as well as in patients thought to be “steroid-dependent.”  相似文献   
66.
We performed proton magnetic resonance spectroscopic imaging of the temporal lobes between, during, and soon after nonconvulsive seizures in 20 patients with documented temporal lobe epilepsy, 5 patients with primary generalized epilepsy, and 2 patients with secondary generalized epilepsy. Our objective was to determine whether there were metabolic changes observable by magnetic resonance spectroscopic imaging during seizures and whether these changes were specific for focal or generalized nonconvulsive seizures. We found a significant increase in lactate to creatine plus phosphocreatine (lactate/creatine) values, reflecting an imbalance in energy supply and demand or an adaptation in response to ictal neuronal discharges, during and soon after complex partial seizures, but not during or soon after absence seizures associated with generalized epilepsy. In patients with temporal lobe epilepsy, the N-acetylaspartate resonance relative to creatine plus phosphocreatine was low in one or both temporal lobes, indicating neuronal loss or damage. This was not observed in patients with primary generalized epilepsy. The regions with abnormal lactate/creatine and N-acetylaspartate/creatine values corresponded to the epileptogenic focus as defined by clinical-electroencephalographic investigation. There was no change in the N-acetylaspartate/creatine values in the temporal lobes between the interictal, ictal, or postictal states. We conclude that (1) partial seizures are associated with abnormally high lactate levels, but absence seizures are not, and (2) no short-term changes of N-acetylaspartate occur during or soon after complex partial seizures or absence seizures. These findings may be related to the lack of postictal confusion in patients with absence seizures, as well as with the more benign course of primary generalized epilepsy with nonconvulsive attacks.  相似文献   
67.
68.
A bstract Objectives and Background : The purpose of this study was to document our initial experience with patients 90 years of age and older and to determine whether cardiac surgery is justified in this age group. Cardiac surgery in octogenarians has proven to be a successful and worthwhile procedure. A small group of nonagenarians with severe coronary artery disease (CAD) and aortic valve disease refractory to medical therapy have been considered for surgery. Methods : Fourteen patients aged 90 or more underwent cardiac surgery for symptomatic CAD or aortic valvular disease refractory to medical therapy. Eight patients underwent isolated coronary artery bypass grafting (CABG) and six patients underwent aortic valve replacement (AVR). All patients were in NYHA Class IV preoperatively. Results : Hospital mortality occurred in one patient (7%). Hospital morbidity occurred in 10 patients (71%) and included 7 cardiac, 5 neurological, 1 gastrointestinal, 1 infectious, and 1 pulmonary event. All survivors left the hospital symptomatically improved. The mean length of stay was 26 days. Four CABG patients went on to die at a mean of 2 years and 2 months, and 3 remain alive at a mean of 2 years and 4 months. Three AVR patients expired at a mean of 3 years and 4 months, and 3 remain alive at 4 years and 1 month. Conclusions : Cardiac surgery in carefully selected nonagenarians is justified and can be performed with acceptable results.  相似文献   
69.
We examined 83 mothers from Szczecin (north-west part of Poland) and their 83 neonates. Concentrations of total and ionized magnesium in maternal and cord serum, as well as total magnesium in hair were determined. Higher levels of total magnesium were noted in neonates (cord serum, hair) than mothers. A positive correlation was ascertained between total magnesium in maternal and cord serum. Magnesium in maternal hair correlated negatively with ionized magnesium in cord serum. Male neonates demonstrated higher levels of magnesium in cord blood and hair than females. There was no effect of maternal age, education level, or number of past pregnancies on the concentration of magnesium in mothers or neonates.  相似文献   
70.
Nine normal bone marrow donors aged 7-166 months (median 69 months) received autologous red cells which had been removed from their marrow harvest after collection. The median volume of marrow removed from the donors was 18.6 ml/kg which was equivalent to a median blood volume loss of 23.3%. Three infant donors were transfused with autologous red blood cells intraoperatively. These cells had been salvaged from the initial marrow aliquot and were transfused while bone marrow harvesting continued. No donors required homologous blood transfusion. This technique is useful for marrow donors in the pediatric age group when preharvest autologous blood collection is not feasible or available.  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