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   166169篇
  免费   7894篇
  国内免费   483篇
耳鼻咽喉   2382篇
儿科学   5330篇
妇产科学   4546篇
基础医学   22882篇
口腔科学   4619篇
临床医学   11065篇
内科学   38022篇
皮肤病学   5440篇
神经病学   13579篇
特种医学   3946篇
外国民族医学   31篇
外科学   21224篇
综合类   949篇
一般理论   38篇
预防医学   17105篇
眼科学   3390篇
药学   11943篇
中国医学   527篇
肿瘤学   7528篇
  2023年   899篇
  2022年   1503篇
  2021年   3607篇
  2020年   1894篇
  2019年   3556篇
  2018年   4865篇
  2017年   3091篇
  2016年   3102篇
  2015年   3423篇
  2014年   4485篇
  2013年   6634篇
  2012年   9976篇
  2011年   10280篇
  2010年   5686篇
  2009年   4889篇
  2008年   8432篇
  2007年   8878篇
  2006年   8670篇
  2005年   8674篇
  2004年   8090篇
  2003年   7516篇
  2002年   7212篇
  2001年   5251篇
  2000年   5411篇
  1999年   4509篇
  1998年   1280篇
  1997年   908篇
  1996年   861篇
  1995年   735篇
  1994年   622篇
  1992年   2239篇
  1991年   2144篇
  1990年   1993篇
  1989年   1764篇
  1988年   1616篇
  1987年   1579篇
  1986年   1466篇
  1985年   1400篇
  1984年   1040篇
  1983年   892篇
  1979年   1001篇
  1978年   667篇
  1975年   681篇
  1974年   880篇
  1973年   852篇
  1972年   740篇
  1971年   693篇
  1970年   746篇
  1969年   706篇
  1968年   669篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
Sodium succinate improves the survival of a skin graft in mice, rats, and dogs normalizes histamine and serotonin concentrations in the epidermis and blood, exhibits antitoxic activity, improves microcirculation in the skin, brain, heart, kidneys, and testes without any appreciable effect on systemic arterial pressure, cardiac function, and liver blood flow in rats. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 10, pp. 420–424, October, 1998  相似文献   
962.
Abstract: Genotyping of the HLA-C locus by PCR-SSP in Behçet's disease patients from southern Spain reveals a statistically significant association with Cw*1602 (OR 20.15, corrected ρ<0.05). This is an uncommon allele absent from the healthy control group, which seems to confer higher relative risk than B51 in this study (OR 1.85). Stratified frequencies do not show statistically significant differences but suggest that the Cw*1602-B51 haplo-type could be the main HLA marker of Behçet's disease in the analyzed population.  相似文献   
963.
A molecular analysis of the maternal and child CTG repeat size and intergenerational amplification was performed in order to estimate the risk of having a child with congenital myotonic dystrophy (CMD). In a study of 124 affected mother-child pairs (42 mother-CMD and 82 mother-non-CMD) the mean maternal CTG allele in CMD cases was three times higher (700 repeats) than in non-CMD cases (236 repeats). When the maternal allele was in the 50-300 repeats range, 90% of children were non-CMD. In contrast, when the maternal allele was greater than 300 repeats, 59% inherited the congenital form. Furthermore, the risk of having a CMD child is also related to the intergenerational amplification, which was significantly greater in the mother-CMD pairs than in the mother-non-CMD pairs. Although the risk of giving birth to a CMD child always exists for affected mothers, our data show that such a risk is considerably higher if the maternal allele is greater than 300 repeats.  相似文献   
964.
This report is of a community-based case control study to assess whether the severity of acute diarrhea by rotavirus (RV) in young children is associated with a particular VP7 (G) or VP4 (P) RV serotype. Five hundred twenty children younger than 2 years of age with diarrhea lasting less than 3 days were age and gender matched with 520 children with no diarrhea. The G and P serotypes were determined with specific monoclonal antibodies, and the VP4 serotype specificity in a subgroup was confirmed by genotyping. Infection with a G3 serotype led to a higher risk of diarrhea than infection with a G1 serotype. Infection with a G3-nontypeable-P serotype was associated with more severe gastroenteritis than infection with a G3 (or G1) P1A[8] serotype. A child with diarrhea-associated dehydration was almost five times more likely to be infected with a G3-nontypeable-P serotype than a child without dehydration (P < 0.001). Moreover, the two predominant monotypes within serotype P1A[8] had significantly different clinical manifestations. In this study, the severity of RV-associated diarrhea was related to different P serotypes rather than to G serotypes. The relationship between serotype and clinical outcomes seems to be complex and to vary among different geographic areas.  相似文献   
965.
(1) Antibodies reactive with purified DNA in the complement fixation system and induced by active immunization of rabbits with methylated bovine serum albumin—DNA aggregate (MBSA—DNA) have been previously described. The present study demonstrates their reactivity in the quantitative and double diffusion preciptin systems. In these systems they have shown preferential reactivity with heat denatured DNA and great cross-reactivity with denatured DNA from various sources.

(2) Methylated rabbit serum albumin—DNA aggregate (MRSA—DNA) is an effective immunizing antigen resulting in the production of antibodies similar to those produced by MBSA—DNA.

(3) The precipitating antibodies in this system are 19S immunoglobulins and appear to be identical to the complement fixing antibodies.

(4) The precipitin reaction is not significantly inhibited by mono-nucleotides.

  相似文献   
966.
967.
Summary Utilization of carbohydrates and free fatty acids (FFA) has been investigated in gastrocnemii of dogs during long lasting isotonic rhythmical exercise induced by supramaximal stimulation of the sciatic nerve. Uptake or output of gases and substrates was determined according to the Fick principle. The first measurements were done at about 2 min after the beginning of work when blood flow has reached a steady state, and the latest at about 100 min after the beginning of exercise.During the first 7 min when the work performed exceeded 5 kg/100g×min and O2 consumption exceeded 11 ml/100g×min, uptake of arterial glucose and FFA was low, accounting for less than 40% of the total O2 consumption. Since the RQ values at the same time were about 1.0, glycogen must have been oxidized as the major aerobic energy source.About 13 min after the beginning of exercise, the work the muscles could perform declined to about half of the initial value and remained so for the following 90 min. During this time the oxygen extraction ratio of FFA was about 50% and of arterial glucose was 40–50%, while the RQ value was about 0.8.During initial strong exercise an output of lactic acid (LA) of about 10 mg/100 g×min was measured. With the decrease of work as a consequence of fatigue, LA output became negligible, and in many experiments small amounts of LA were taken up by the working gastrocnemii.It is concluded that glycogen is the major aerobic energy source for strong muscular exercise which cannot be substituted for by the oxidation of arterial glucose or FFA.Supported by the Deutsche Forschungsgemeinschaft.  相似文献   
968.
969.
970.
To determine the effects of creatine supplementation during short-term resistance training overreaching on performance, body composition, and resting hormone concentrations, 17 men were randomly assigned to supplement with 0.3 g/kg per day of creatine monohydrate (CrM: n=9) or placebo (P: n=8) while performing resistance exercise (5 days/week for 4 weeks) followed by a 2-week taper phase. Maximal squat and bench press and explosive power in the bench press were reduced during the initial weeks of training in P but not CrM. Explosive power in the bench press, body mass, and lean body mass (LBM) in the legs were augmented to a greater extent in CrM (P0.05) by the end of the 6-week period. A tendency for greater 1-RM squat improvement (P=0.09) was also observed in CrM. Total testosterone (TT) and the free androgen index (TT/SHBG) decreased in CrM and P, reaching a nadir at week 3, whereas sex hormone binding globulin (SHBG) responded in an opposite direction. Cortisol significantly increased after week 1 in CrM (+29%), and returned to baseline at week 2. Insulin was significantly depressed at week 1 (–24%) and drifted back toward baseline during weeks 2–4. Growth hormone and IGF-I levels were not affected. Therefore, some measures of muscular performance and body composition are enhanced to a greater extent following the rebound phase of short-term resistance training overreaching with creatine supplementation and these changes are not related to changes in circulating hormone concentrations obtained in the resting, postabsorptive state. In addition, creatine supplementation appears to be effective for maintaining muscular performance during the initial phase of high-volume resistance training overreaching that otherwise results in small performance decrements.  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