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   50540篇
  免费   3219篇
  国内免费   160篇
耳鼻咽喉   522篇
儿科学   1435篇
妇产科学   1174篇
基础医学   6648篇
口腔科学   2115篇
临床医学   4596篇
内科学   11543篇
皮肤病学   1075篇
神经病学   4106篇
特种医学   1390篇
外科学   7159篇
综合类   514篇
一般理论   51篇
预防医学   4646篇
眼科学   909篇
药学   3144篇
  1篇
中国医学   142篇
肿瘤学   2749篇
  2023年   293篇
  2022年   558篇
  2021年   1258篇
  2020年   756篇
  2019年   1168篇
  2018年   1474篇
  2017年   1020篇
  2016年   982篇
  2015年   1332篇
  2014年   1742篇
  2013年   2214篇
  2012年   3403篇
  2011年   3665篇
  2010年   1872篇
  2009年   1662篇
  2008年   2937篇
  2007年   3079篇
  2006年   2879篇
  2005年   2760篇
  2004年   2404篇
  2003年   2176篇
  2002年   1990篇
  2001年   914篇
  2000年   890篇
  1999年   757篇
  1998年   419篇
  1997年   368篇
  1996年   324篇
  1995年   309篇
  1994年   281篇
  1993年   259篇
  1992年   583篇
  1991年   582篇
  1990年   526篇
  1989年   503篇
  1988年   460篇
  1987年   406篇
  1986年   370篇
  1985年   435篇
  1984年   342篇
  1983年   303篇
  1982年   202篇
  1981年   176篇
  1979年   248篇
  1978年   214篇
  1976年   168篇
  1975年   174篇
  1974年   188篇
  1973年   216篇
  1972年   185篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Except for two reported patients, increased free sialic acid excretion has been associated with lysosomal storage. This is a report of a child with progressive neurologic deterioration and increased excretion of free sialic acid. Although lysosomal storage was absent, nuclear invagination or inclusions were present.  相似文献   
92.
93.
A series of studies designed to define the requirement of normal infants for sulfur-containing amino acids (methionine, cystine) was conducted with formulas providing 3.0, 2.8, 2.6, 2.2 or 1.8 g of isolated soy protein per 100 kcal. The formulas were fed with or without a methionine supplement. Adequacy of the diet was determined by measurement of growth, serum chemical indices and nitrogen balance. Nitrogen balance demonstrated a beneficial effect of methionine supplementation only at the lowest protein concentration (1.8 g/100 kcal). However, measurement of weight gain and/or serum concentrations of urea nitrogen and albumin clearly showed a beneficial effect of methionine supplementation at protein concentrations of 2.2 and 2.6 g/100 kcal. Intakes of sulfur-containing amino acids of 435 and 495 mumol/100 kcal therefore appear inadequate. At higher intakes of protein (2.8 and 3.0 g/100 kcal) there was no beneficial effect of methionine supplementation. Possible exceptions were male infants provided with 3.0 g protein per 100 kcal, in whom weight gain between 8 and 56 d of age was significantly (P less than 0.05) greater with than without a methionine supplement. Based on intakes of sulfur-containing amino acids from the formula providing 2.8 g of isolated soy protein per 100 kcal without methionine supplementation, we conclude that for male infants older than 56 d the requirement for sulfur-containing amino acids is no more than 588 mumol/100 kcal when intake of methionine is 264 mumol/100 kcal. However, it seems possible that such intake fails to meet the requirement in male infants less than 56 d of age. For female infants, regardless of age, 533 mumol/100 of sulfur-containing amino acids per 100 kcal meet the requirement when intake of methionine is 239 mumol/100 kcal.  相似文献   
94.
Corneal allograft rejection in rabbits   总被引:1,自引:0,他引:1  
We performed a phase I study to assess the therapeutic efficacy of an anti-T cell monoclonal antibody conjugated with ricin A-chain in a corneal graft rejection model. Corneal allografts were exchanged between Dutch and New Zealand rabbits. Rejections occurred within 16-22 days in untreated animals. Graft rejection was delayed by topical or retrobulbar cyclosporine, but not by subconjunctival injections of a murine anti-rabbit T cell monoclonal antibody, nor by either subconjunctival or intravenous F(ab')2-ricin conjugate.  相似文献   
95.
Exposure of ZR-75-1 human breast cancer cells for 48 h to human recombinant interferon alpha (IFN alpha) resulted in increased expression of oestrogen receptors as measured in a whole cell binding assay. This effect was inversely proportional to dose being significant following treatment with 10-100 IU IFN ml-1 and was only observed at a low initial cell plating density. The extent of the increase in oestrogen receptor levels ranged from 1.2- to 7.2-fold following treatment with 10 IU IFN ml-1. No increase in progesterone receptor expression was observed under the same experimental conditions. Concentrations of IFN which increased oestrogen receptor levels had no effect on cell proliferation. IFN (500 IU ml-1) inhibited cell proliferation and the combination of this treatment with tamoxifen (2 microM) had a greater anti-proliferative effect than either drug alone although there was no evidence of synergism. However, a 5-day pretreatment of cells with IFN (10 IU ml-1) markedly sensitised them to the growth-inhibiting effect of a subsequent 6-day exposure to tamoxifen.  相似文献   
96.
Recovery from the transient pulmonary reaction which accompanies the nasal instillation of variola virus in mice was followed by a measurable protection against the homologous virus and also against vaccinia. Variola virus which regularly survived in the lung of normally susceptible mice through the 5th day was noticeably reduced in titer on the 3rd day in the lung of recovered animals, and usually eliminated by the 5th day. Vaccinia virus produced a less severe systemic reaction in recovered mice and its titer in the lung was significantly reduced on the 5th day. The residence of both viruses in the lung of recovered mice was attended by pathological changes, visible macroscopically.  相似文献   
97.
OBJECTIVE: Compare the immunological and echocardiographic data of decellularized versus cryopreserved allografts used for RVOT reconstruction during Ross operation. METHODS: From 16/01/03 thru 07/10/03, 20 Ross operations were performed using decellularized (n=11) or cryopreserved (n=9) allografts. Echocardiography was done at discharge, 1, 3, 6 and 12 months and annually thereafter. Samples for determination of antibodies against HLA class I and II were obtained preoperatively and at days 5, 10, 30, 90 and 180 postoperatively. These samples were tested by the ELISA method in LAT-M dishes (unspecific) for identification of circulating antibodies and the results expressed as mean sample values (Is=DO/cutoff). If positive, LAT-E (specific) was performed and PRA levels determined. RESULTS: There was no mortality. Cryopreserved allografts showed marked Is values elevations for class I and II antibodies which started at the first month and remained elevated up to 6 months. In contrast, of the patients receiving decellularized allografts, seven remained negative, two patients had only marginal elevation of class I antibodies and two patients showed abnormal elevations of PRA levels. This response happened earlier than in the cryopreserved group, starting on the 5th postoperative day and has returned to baseline levels in one case. Echocardiography showed mild, but significant, elevation of gradients in cryopreserved valves but none in the decellularized. CONCLUSIONS: Decellularized allografts had normal function up to 18 months and showed important reduction of the immunogenic response when compared to cryopreserved valves.  相似文献   
98.
Bacterial infections are frequent in cadaveric organ donors and can be transmitted to the transplantation recipient, which could have devastating consequences for the recipients if adequate preventive measures are not adopted.
From the 355 consecutive brain dead cadaveric organ donors procured at our center in the last four years, 2000–2003, four of them (1.1%) had bacterial endocarditis as cause of death. The bacteria responsible for the endocarditis were Staphylococcus epidermidis, coagulase-negative Staphylococcus , Staphylococcus hominis and Streptococcus viridans , respectively. We performed five kidney and two liver transplantations on seven recipients. All donors and recipients received antibiotic treatment against the germ causing the respective endocarditis.
Infection by the bacteria responsible for the endocarditis in the respective donors was not transmitted to any of the recipients. Six of the seven recipients were alive with normal-functioning grafts after between 13 and 24 months' follow-up. Transplantectomy was performed on one kidney recipient due to thrombosis of the renal vein of the graft not related to the endocarditis.
Liver and kidney transplantation from donors dying from bacterial endocarditis can be performed without causing the transmission of infection to the recipient or the dysfunction of the graft.  相似文献   
99.
BACKGROUND: Epinephrine injected by an autoinjector in the anterolateral aspect of the thigh is the standard of care in the emergency self-treatment of anaphylaxis. In the United States, the autoinjector EpiPen is widely used for the self-treatment of anaphylaxis. OBJECTIVE: To investigate whether EpiPen autoinjector, with a needle length of 1.43 cm, is sufficient for intramuscular delivery of epinephrine in men and women. METHODS: The distance from skin to muscle in the anterolateral aspect of the thigh was measured in 50 men and 50 women who had undergone computed tomography of the thighs for other medical reasons. For each individual, body mass index (BMI; a measure of weight in kilograms divided by the square of height in meters) was also calculated, and the individuals were classified as underweight (BMI, < 18.5), normal (BMI, 18.5-24.9), overweight (BMI, 25.0-29.9), and obese (BMI, > or = 30.0) using standard definition. RESULTS: In the study participants the mean +/- SD distance from skin to muscle was 0.66 +/- 0.47 cm for men and 1.48 +/- 0.72 cm for women (P < .001). One man (obese at a BMI of 42.2) and 21 women (11 obese with a mean BMI of 35.2, 6 overweight with a mean BMI of 30.1, and 4 normal with a mean BMI of 24.5) had a greater distance from skin to muscle than the EpiPen needle length of 1.43 cm. CONCLUSION: The distance from skin to muscle for the anterolateral aspect of the thigh is higher in women compared with men. This difference suggests that EpiPen may not deliver epinephrine to the intramuscular tissue in many women.  相似文献   
100.
BACKGROUND: Neither the presence nor prevalence of enteric hyperoxaluria has been recognized after Roux-en-Y gastric bypass (RYGBP). We have noted a high rate of oxalate nephrolithiasis and even 2 patients with oxalate nephropathy in this patient population postoperatively. Our aim was to determine the frequency of the occurrence and effects of enteric hyperoxaluria after RYGBP. METHODS: Retrospective review of all patients at our institution diagnosed with calcium oxalate nephrolithiasis or oxalate nephropathy after standard (n = 14) or distal (n = 9) RYGBP. The mean postoperative follow-up was 55 months. RESULTS: A total of 23 patients (14 men and 9 women; mean age 45 years; mean preoperative body mass index 55 kg/m(2)) developed enteric hyperoxaluria after RYGBP, defined by the presence of oxalate nephropathy (n = 2) or calcium oxalate nephrolithiasis (n = 21) and increased 24-hour excretion of urinary oxalate and/or calcium oxalate supersaturation. Enteric hyperoxaluria was recognized after a mean weight loss of 46 kg at 29 months (range 2-85) after RYGBP. Two patients developed renal failure and required chronic hemodialysis. Of the 21 patients with nephrolithiasis, 14 had no history of nephrolithiasis preoperatively, and 19 of 21 required lithotripsy or other intervention. Of the 23 patients, 20 tested had increased oxalate excretion, and 14 of 15 tested had high urine calcium oxalate supersaturation. CONCLUSION: Enteric hyperoxaluria, nephrolithiasis, and oxalate nephropathy must be considered with the other risks of RYGBP. Efforts should be made to identify factors that predispose patients to developing hyperoxaluria.  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