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   195416篇
  免费   11344篇
  国内免费   503篇
耳鼻咽喉   2436篇
儿科学   6123篇
妇产科学   3999篇
基础医学   26730篇
口腔科学   7840篇
临床医学   14759篇
内科学   44228篇
皮肤病学   4963篇
神经病学   16301篇
特种医学   5991篇
外国民族医学   29篇
外科学   24729篇
综合类   1654篇
现状与发展   1篇
一般理论   88篇
预防医学   19675篇
眼科学   3635篇
药学   11827篇
  1篇
中国医学   744篇
肿瘤学   11510篇
  2023年   947篇
  2022年   2061篇
  2021年   3930篇
  2020年   2635篇
  2019年   3766篇
  2018年   5228篇
  2017年   3891篇
  2016年   3693篇
  2015年   4320篇
  2014年   5989篇
  2013年   7718篇
  2012年   11958篇
  2011年   12581篇
  2010年   6493篇
  2009年   5960篇
  2008年   10024篇
  2007年   10755篇
  2006年   10094篇
  2005年   10469篇
  2004年   9831篇
  2003年   9065篇
  2002年   7104篇
  2001年   5323篇
  2000年   5259篇
  1999年   4720篇
  1998年   1898篇
  1997年   1605篇
  1996年   1551篇
  1995年   1344篇
  1994年   1319篇
  1993年   1197篇
  1992年   2943篇
  1991年   2843篇
  1990年   2588篇
  1989年   2568篇
  1988年   2305篇
  1987年   2155篇
  1986年   2047篇
  1985年   1955篇
  1984年   1457篇
  1983年   1205篇
  1982年   784篇
  1981年   741篇
  1980年   671篇
  1979年   1055篇
  1978年   737篇
  1977年   610篇
  1975年   652篇
  1974年   641篇
  1973年   632篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Summary In 1981 generalized anaphylaxis was registered on 166 occasions in Dutch general and academic hospitals. Clinical details of 120 of those patients revealed that in 107 anaphylaxis was either probable (n=90) or possible (n=17), whereas in 13 cases some other reaction than anaphylaxis had occurred. The series of confirmed cases contained 46 men and 61 women, with mean ages of 47 y and 48 y, respectively.There was a complete recovery in 102 patients and two patients died. Hypotension was present in 79 cases (74%), dyspnoea in 34 cases (32%) and a skin reaction, mainly urticaria, erythema or angioedema, was mentioned in 62 cases (58%). Most cases of anaphylaxis were drug-induced (76%), the main causes being the analgesic glafenine and contrast media. Glafenine was mentioned as the cause in 36% of all admissions for drug-induced anaphylaxis. Only 3.7% of cases had been reported to the voluntary reporting scheme of the Netherlands Centre for Monitoring of Adverse Reactions to Drugs.On the basis of reimbursement data, the risk of developing severe anaphylaxis to glafenine was estimated at 11.7–19.3-fold relative to indomethacin, and 13.4–20.2-fold relative to oral penicillins.  相似文献   
102.
We report the clinical, neurophysiological (comprehending electromyography, nerve conduction velocities, and multimodal evoked potentials), histological study of the nerve and muscle and the effect of vitamin E supplement in a 32-year-old case with chronic vitamin E deficiency subsequent to acquired intestinal malabsorption. An early diagnosis for an early treatment is essential in preventing severe neurological deterioration.  相似文献   
103.
To standardize the maximal static force (Fo) of the arm flexors, the accuracy of an anthropometric method for estimating the mid-arm cross-sectional muscle and bone area (MBA) was investigated. This was done by comparing the anthropometrically determined area (MBA.A) with the area measured by means of computerized tomography (MBA.S). In the same way, the accuracy of Heymsfield's equations (Heymsfield et al., 1982) for predicting MBA (MBA.H) from anthropometric measures was tested. MBA.A was significantly larger than MBA.S, the relative difference increasing with the thickness of the subcutaneous fat layer. This difference was attributed to a 27% underestimation of the fat layer thickness as measured with the skinfold caliper. Women being fatter than men, this caused the standardized maximal static force (Fo/MBA) to be lower in women than in men. MBA.H was 12% smaller than MBA.S. This may have been due to a difference in the way of measuring the arm circumference between the present authors and Heymsfield et al.  相似文献   
104.
The aim of the present study was to probe the structural integrity of insulin after being entrapped into chitosan/alginate nanoparticles produced by ionotropic polyelectrolyte pre-gelation. By manipulating the alginate:chitosan mass ratio and the pH during nanoparticle production, desired nanoparticles with a mean size of 850 (+/-88)nm and insulin association efficiency of 81 (+/-2)% were obtained. Insulin secondary structure was assessed by Fourier transform infrared (FTIR) and circular dichroism (CD) after entrapment into nanoparticles and after release from the particles under gastrointestinal simulated conditions. FTIR second-derivative spectra and area-overlap compared to an insulin standard confirmed that no significant conformational changes of insulin occurred in terms of alpha-helix and beta-sheet content. Far-UV-CD spectra corroborated the preservation of insulin structure during the nanoparticle production procedure. The presented nanoparticulate system is a promising carrier for insulin oral delivery since it preserves insulin structure and therefore also, potentially, its bioactivity.  相似文献   
105.
OBJECTIVE: The authors tested the effect of blood sampling (skin versus venous puncture) on some biochemical and hematological blood parameters in athletes to answer whether skin puncture could be used as a substitute for venous puncture. DESIGN: Comparative study of 2 methods of blood samples collection. SETTING: The blood was collected in the same athletes at 3 different moments of the preparatory training phase. PARTICIPANTS: Fourteen male indoor soccer players (22 +/- 1 years old) and 7 female handball players (18 +/- 1 years old) participated. MAIN OUTCOME MEASUREMENT: Blood was collected in heparin and K3EDTA by Vacutainer BD or Microvette Sarstedt system for biochemical and hematological analyses, respectively. RESULTS: There were no significant statistical differences between the 2 methods for the values of creatine kinase, urea, creatinine, lymphocytes, and platelets. The other hematological analyzes and uric acid exhibited significant higher values in skin blood, although they were all within the normal expected range. A high degree of correlation was observed between the 2 techniques for all parameters. CONCLUSIONS: Skin puncture is a reliable, easy, accurate, and less invasive sampling method for assessing hematological and some biochemical parameters in athletes, respecting that blood samples should always be obtained from the same site, especially in follow-up studies.  相似文献   
106.
BACKGROUND: Exposure to a high level of house dust mite allergens (HDMAs) is considered as a risk factor for HDM sensitization and development of asthma in genetically disposed people. Mattresses are one of the most important sources of HDMA in people's living environment. OBJECTIVE: The aim of this study was to evaluate the association between mattress characteristics and HDMA concentrations on mattresses. METHODS: Dust samples of mattress surfaces were taken to evaluate the level of Der p 1 allergen. All participants filled in a questionnaire about the type of mattress, the type of covering (upper layer) of the mattress, dwelling characteristics and cleaning habits. Humidity and temperature of the bedroom were measured at the time of dust sampling. RESULTS: One hundred and sixty-eight questionnaires were filled in. Synthetic upper layer of the mattress was associated with a higher level of Der p 1 compared with cotton upper layer (2.6 vs. 0.8 microg/g Der p 1). Moreover, higher relative humidity (RH) was associated with significant higher concentrations and density of Der p 1. CONCLUSIONS: Two factors were associated with lower levels of Der p 1 found on mattresses, namely: a cotton upper layer of the mattress compared with a layer of synthetic material and lower RH at the time of sampling. As far as we know, the association between type of upper layer and concentration of Der p 1 has not been described before and could lead to the formulation of practical advices in order to reduce HDMA concentrations on mattresses.  相似文献   
107.
1. alpha 2-Adrenoceptors on platelet membranes and beta 2-adrenoceptors on lymphocytes were studied in 24 patients with primary Raynaud's phenomenon and in 24 age- and sex-matched control subjects. In two subgroups, a standardized mental arithmetic test and a finger-cooling test were performed. 2. Baseline blood pressure, heart rate and forearm blood flow did not differ between the two groups. 3. Baseline skin microcirculation (laser Doppler flux) was decreased in primary Raynaud's phenomenon (19 +/- 15 arbitrary units) compared with control subjects (33 +/- 14 arbitrary units) (P less than 0.01). 4. Baseline plasma noradrenaline concentration (2.00 +/- 1.44 versus 1.16 +/- 0.36 nmol/l) and alpha 2-adrenoceptor density (301 +/- 119 versus 210 +/- 82 fmol/mg) were increased in patients with primary Raynaud's phenomenon in comparison with the control subjects. The alpha 2-adrenoceptor density/beta 2-adrenoceptor density ratio in patients with primary Raynaud's phenomenon was, with a value of 0.37 +/- 0.04, higher than in the control subjects, where a value of 0.25 +/- 0.02 was measured (P less than 0.001). Plasma adrenaline concentration, beta 2-adrenoceptor density and the antagonist affinity to both receptor subtypes did not differ between both groups under baseline conditions. 5. Whereas during the finger-cooling test no differences were seen in the responses of the parameters measured, the mental arithmetic test induced an increase in laser Doppler flux in patients with primary Raynaud's phenomenon and a decrease in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
108.
109.
Plasma pyridoxal-5'-phosphate and pyridoxal levels increased significantly (p less than 0.05) when single, oral bolus doses of pyridoxine were increased from 10 to 25 and from 25 to 50 mg in nine female volunteers. However, when the dose was increased to 100 mg, plasma pyridoxal-5'-phosphate levels did not differ significantly from those recorded after the 50 mg dose. Within 3 h plasma pyridoxal levels rose with a factor of 3.85 compared with the 50 mg dose but high pyridoxal levels were eliminated from the circulation. Renal clearance of pyridoxal remained a constant, low percentage (less than 2.0%) of each pyridoxine supplement in spite of the observed very high circulating pyridoxal levels. Pyridoxine supplementation is discussed in relation to circulating pyridoxal-5'-phosphate and pyridoxal availability for cellular metabolism.  相似文献   
110.
Mucosa isolated from the proximal third of the small intestine of infant rats had much lower cyclic nucleotide concentrations (expressed both per unit wet weight and per unit DNA content) than those determined in the intestinal wall. The steady-state concentrations of both cyclic AMP and cyclic GMP in jejunum showed dramatic increases during the first 5 d post partum. Another increase in cyclic nucleotide concentrations was observed in the isolated mucosa between d 15 and 21. Starvation for 24 h always resulted in lower intestinal cyclic nucleotide concentrations than those of the fed littermates. This effect was more pronounced in younger animals and more evident for cyclic AMP values. Three-week-old rats fed a high carbohydrate diet for 24-48 h exhibited more pronounced elevations in the concentrations of cyclic nucleotides from the jejunal mucosa than did rats fed a high fat diet.  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