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   822篇
  免费   23篇
  国内免费   12篇
耳鼻咽喉   11篇
儿科学   18篇
妇产科学   27篇
基础医学   138篇
口腔科学   4篇
临床医学   37篇
内科学   207篇
皮肤病学   12篇
神经病学   72篇
特种医学   9篇
外科学   107篇
综合类   4篇
预防医学   45篇
眼科学   3篇
药学   86篇
中国医学   1篇
肿瘤学   76篇
  2022年   24篇
  2021年   23篇
  2020年   16篇
  2019年   9篇
  2018年   14篇
  2017年   5篇
  2016年   5篇
  2015年   18篇
  2014年   19篇
  2013年   30篇
  2012年   31篇
  2011年   47篇
  2010年   21篇
  2009年   28篇
  2008年   32篇
  2007年   61篇
  2006年   49篇
  2005年   65篇
  2004年   57篇
  2003年   38篇
  2002年   50篇
  2001年   6篇
  2000年   6篇
  1999年   8篇
  1998年   9篇
  1997年   22篇
  1996年   13篇
  1995年   13篇
  1994年   9篇
  1993年   3篇
  1992年   10篇
  1991年   9篇
  1990年   7篇
  1989年   6篇
  1988年   5篇
  1987年   7篇
  1986年   12篇
  1985年   3篇
  1984年   3篇
  1983年   6篇
  1982年   3篇
  1980年   7篇
  1979年   3篇
  1976年   4篇
  1974年   5篇
  1973年   3篇
  1967年   5篇
  1965年   2篇
  1958年   2篇
  1928年   2篇
排序方式: 共有857条查询结果,搜索用时 15 毫秒
101.
An altered perception of pain has been described for several psychiatric disorders. To date the influence of adjustment disorders (AD) on pain perception has not been described. Here, we investigated perception of experimentally induced pain in 15 patients suffering from AD (subtype with depressive symptoms) and controls matched for age and sex. Thresholds and tolerances were assessed for thermal and electrical pain on both sides of the body. We found an overall increase of pain thresholds and tolerances in AD patients as compared to controls, predominately on the right side of the body. Analogue findings have been reported for pain perception in major depressive disorder (MDD). Of the data obtained, only thermal pain threshold on the right arm correlated with the severity of depressive symptoms. Although the underlying pathology is elusive it is likely that the mechanisms for reduced pain sensitivity are comparable in MDD and AD.  相似文献   
102.
A retrospective analysis of clinical and pathological prognostic factors was performed in 1 068 breast cancer patients treated with radical mastectomy alone in 1952-1980. Three endpoints were considered: 10-year survival, 10-year disease-free survival and 10-year loco-regional relapse-free survival. Both univariate and multivariate analyses confirmed the prognostic significance of tumour size, histological type and grade (Bloom classification) and involvement of axillary nodes for all three endpoints. Additionally, young age appeared to be a significant risk factor for loco-regional disease-free survival. Prognostic subgroups were defined by the use of 3 main indicators. In node negative patients with T1 tumours the prognosis seemed to be good regardless of histological grade (80-90% 10-year disease-free survival), in T2 tumours the survival was significantly dependent on histological type and grade. In node positive patients increasing number of involved nodes and higher histological grade had an independent adverse effect on all three endpoints. The study demonstrates that classical, commonly available prognostic factors clearly distinguish subgroups with different prognosis, which may be helpful when deciding on the use of adjuvant local and/or systemic therapies.  相似文献   
103.
104.
Lipid emulsions are an integral part of parenteral nutrition, and traditionally have been regarded as an energy-dense source of calories and essential fatty acids. For many years, lipids used in parenteral nutrition have been based on vegetable oils (eg, soybean-oil emulsions). However, soybean-oil emulsions may not have an optimal fatty-acid composition under some circumstances when used as the only lipid source, as soybean oil is particularly abundant in the ω-6 polyunsaturated fatty acid (PUFA), linoleic acid. Hence, a progressive series of more complex lipid emulsions have been introduced, typically combining soybean oil with 1 or more alternative oils, such as medium-chain triglycerides (MCTs) and/or olive oil and/or fish oil. The wide range of lipid emulsions now available for parenteral nutrition offers opportunities to alter the supply of different fatty acids, which potentially modifies functional properties, with effects on inflammatory processes, immune response, and hepatic metabolism. Fish oil has become an important component of modern, composite lipid emulsions, in part owing to a growing evidence base concerning its biological effects in a variety of preclinical models. These biological activities of fish oil are mainly attributed to its ω-3 PUFA content, particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA and EPA have known mechanisms of action, anti-inflammatory, immunomodulatory, and antioxidative properties. Specialized proresolving mediators, such as resolvins, protectins, and maresins, are synthesized directly from DHA and EPA, are key for the resolution of inflammation, and improve outcomes in many cell- and animal-based models and, recently, in some clinical settings.  相似文献   
105.
This study investigated the production of Cu2+-doped CoFe2O4 nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu2+ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for applications in electrical devices. The XRD analysis revealed the formation of spinel-phased crystalline structures of the specimens with no impurity phases. The average grain size, lattice constant, cell volume, and porosity were measured in the range of 4.55–7.07 nm, 8.1770–8.1097 Å, 546.7414–533.3525 Å3, and 8.77–6.93%, respectively. The SEM analysis revealed a change in morphology of the specimens with a rise in Cu2+ content. The particles started gaining a defined shape and size with a rise in Cu2+ doping. The Cu0.12Co0.88Fe2O4 NPs revealed clear grain boundaries with the least agglomeration. The energy band gap declined from 3.98 eV to 3.21 eV with a shift in Cu2+ concentration from 0.4 to 0.12. The electrical studies showed that doping a trace amount of Cu2+ improved the electrical properties of the CFO NPs without producing any structural distortions. The conductivity of the Cu2+-doped CFO NPs increased from 6.66 × 10−10 to 5.26 × 10−6 ℧ cm−1 with a rise in Cu2+ concentration. The improved structural and electrical characteristics of the prepared Cu2+-doped CFO NPs made them a suitable candidate for electrical devices, diodes, and sensor technology applications.  相似文献   
106.
This case report describes a child with severe constitutional hypoplastic anemia and Seckel's syndrome. Immunological analysis on mononuclear peripheral blood cells revealed an abnormally low ratio of T-helper to T-suppressor/cytotoxic cells and a highly increased number of HLA-DR-positive T suppressor/cyiotoxic cells. Interferon-y and interleukin-2 production by mitogen-stimulated peripheral blood mononuclear cells was slightly reduced, and no spontaneous production of these lymphokines was seen. The immunological abnormalities demonstrated in this case of constitutional aplastic anemia may indicate common features with acquired aplastic anemia.  相似文献   
107.
The proportion of the α- and β-ring opening in the addition of unsymmetrically substituted oxiranes to P? OH acids namely diethyl phosphoric acid, phosphorous acid, and phosphoric acid, was established. Ring opening of propylene oxide does not depend on the number of the P? OH groups in the acid and, for di- and trifunctional acids, does not depend on the degree of substitution. After this first reaction of addition the formed hydroxyl groups add the oxirane molecules and the phosphorus-containing polyethers are formed. All of the propylene oxide additions exhibit a ratio of α/β-ring openings of 1:1. For the higher substituted oxiranes the proportion of the attack on the least substituted carbon atom increases, reaching for 1,1-dimethyloxirane up to 90% of α-addition (almost exclusive formation of the tertiary alcohol).  相似文献   
108.
OBJECTIVE: Prospective evaluation of the effect of 6-month-long intradialytic amino acids (AA) supplementation on selected nutritional variables in malnourished hemodialysis (HD) patients. DESIGN: Multicenter, prospective, (nonrandomized, noncontrolled) observational study. SETTING: Thirty-one HD units affiliated with academic centers and tertiary-care hospitals. PATIENTS: Adult patients treated by HD for at least 6 months. Inclusion criteria were: serum albumin concentration < or =39 g/L and at least 4% loss of body weight during the last 6 months in otherwise stable HD patients. From a cohort of 133 patients who were enrolled, 97 (54 men and 43 women) were eligible for the analysis. INTERVENTION: Intradialytic AA supplementation with 500 mL 10% solution per HD session for a period of 6 months. MAIN OUTCOME MEASURES: Serum albumin concentration, modified Subjective Global Assessment (SGA) score, body mass index (BMI), mid-arm circumference (MAC), and total lymphocyte count. Measurements were recorded at baseline and after 3 and 6 months of AA supplementation. RESULTS: Serum albumin concentration increased significantly from the mean 32.5 +/- 4.6g/L at baseline to 36.4 +/- 4.8 g/L at 3 months (P <.001) and 37.1 +/- 4.8 g/L at final observation (P <.001 versus baseline). Significant correlation was observed between frequency of AA supplementation and serum albumin increase (r = 0.41; P <.0001). Rate of improvement negatively correlated significantly with baseline concentration of serum albumin (r = - 0.42; P <.0001). SGA score significantly improved from median of 16 points at baseline to 12 points at 3 months (P <.01) and 11 points at 6 months (P <.01 versus baseline), and this improvement also correlated with the frequency of AA supplementation. Small yet significant increase of MAC was observed at 6 months (from baseline 24.1 +/- 4.3 to 24.8 +/- 4.8 cm; P <.01), whereas BMI remained unchanged. CONCLUSION: Intradialytic AA supplementation improves selected nutritional parameters of HD patients with malnutrition. The improvement depends on the intensity of supplementation.  相似文献   
109.
Many cells in inferotemporal cortex respond more actively to a novel presentation than to a subsequent re-presentation of the same image, exhibiting stimulus specific adaptation (SSA). Previously, analysis of this adaptation was limited to visually excited cells, excluding visually inhibited cells. In the present experiment we studied 654 cells in four macaques performing visual tasks. Strong SSA (P < 0.0001) was observed in those cells which were excited by visual stimuli. This adaptation was also seen in the subset of such cells which, though excited by visual stimuli, failed to show visual specificity in their responses. Interestingly, no SSA (P > 0.1) was observed in the group of cells inhibited by visual stimuli. Furthermore, most inhibited cells failed to show visual specificity. This lack of visual specificity and SSA suggest that the visually inhibited cells have a limited role in the detailed information processing of visual perception and memory activated by the tasks used in the present experiments.  相似文献   
110.
Abstract: 203Hg-Mercuric chloride was administered intragastrically to female rats. The absorption rate evaluated for a broad range of doses was found constant for low and medium range, and higher for high doses. Mercury was determined in internal organs and intestines. The time-course of intestinal mercury indicated that a deposit formed initially in the mucosa was further absorbed into the circulation. No indication was found of a protection mechanism based on exfoliation of the mucosal deposits of metal.  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