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   4518篇
  免费   247篇
  国内免费   20篇
耳鼻咽喉   46篇
儿科学   61篇
妇产科学   66篇
基础医学   553篇
口腔科学   76篇
临床医学   313篇
内科学   970篇
皮肤病学   48篇
神经病学   279篇
特种医学   158篇
外科学   1048篇
综合类   30篇
一般理论   1篇
预防医学   154篇
眼科学   148篇
药学   318篇
中国医学   4篇
肿瘤学   512篇
  2023年   35篇
  2022年   69篇
  2021年   106篇
  2020年   62篇
  2019年   92篇
  2018年   109篇
  2017年   82篇
  2016年   115篇
  2015年   116篇
  2014年   142篇
  2013年   165篇
  2012年   281篇
  2011年   273篇
  2010年   168篇
  2009年   134篇
  2008年   229篇
  2007年   258篇
  2006年   259篇
  2005年   252篇
  2004年   205篇
  2003年   206篇
  2002年   220篇
  2001年   103篇
  2000年   91篇
  1999年   93篇
  1998年   50篇
  1997年   41篇
  1996年   49篇
  1995年   31篇
  1994年   32篇
  1993年   16篇
  1992年   60篇
  1991年   80篇
  1990年   84篇
  1989年   70篇
  1988年   67篇
  1987年   59篇
  1986年   61篇
  1985年   44篇
  1984年   42篇
  1983年   39篇
  1982年   8篇
  1981年   8篇
  1979年   18篇
  1978年   13篇
  1977年   13篇
  1976年   3篇
  1975年   3篇
  1967年   4篇
  1966年   9篇
排序方式: 共有4785条查询结果,搜索用时 15 毫秒
61.
Although important roles of dietary n-3 fatty acids in the prevention of coronary heart disease (CHD) have been suggested, long-term effects of dietary alpha-linolenic acid (ALA, 18:3n-3) have not yet been established under controlled conditions. We tested whether a moderate increase of dietary ALA affects fatty acids composition in serum and the risk factors of CHD. Oxidized LDL (OxLDL) was directly measured by ELISA using antibody specific to OxLDL. By merely replacing soybean cooking oil (SO) with perilla oil (PO) (i.e., increasing 3 g/d of ALA), the n-6/n-3 ratio in the diet was changed from 4:1 to 1:1. Twenty Japanese elderly subjects were initially given a SO diet for at least 6 mo (baseline period), a PO diet for 10 mo (intervention period), and then returned to the previous SO diet (washout period). ALA in the total serum lipid increased from 0.8 to 1.6% after 3 mo on the PO diet, but EPA and DHA increased in a later time, at 10 mo after the PO diet, from 2.5 to 3.6% and 5.3 to 6.4%, respectively (p<0.05), and then returned to baseline in the washout period. In spite of increases of serum n-3 fatty acids, the OxLDL concentration did not change significantly when given the PO diet. Body weight, total serum cholesterol, triacylglycerol, glucose, insulin and HbA1c concentrations, platelet count and aggregation function, prothrombin time, partial thromboplastin time, fibrinogen and PAI-1 concentration, and other routine blood analysis did not change significantly when given the PO diet. These data indicate that, even in elderly subjects, a 3 g/d increase of dietary ALA could increase serum EPA and DHA in 10 mo without any major adverse effects.  相似文献   
62.
Carcinogen-resistant inbred DRH rat strain was established from closed colony Donryu rats in the presence of 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB). Despite using 3'-Me-DAB during the stage of selection, the DRH rats developed normally and did not show any spontaneous tumor at over 1 year of age. In the present study, we examined the polymorphism in mannose 6-phosphate/insulin-like growth factor 2 receptor (M6p/Igf2r) gene and found that the DRH rat showed CCC (Proline)-type polymorphism in exon 48 and the Donryu rat had GCC (Alanine) sequence. Since the DRH rat was developed from the Donryu rat, we examined whether this polymorphism in exon 48 of M6p/Igf2r gene was due to mutation that occurred at the stage of selection in the presence of 3'-Me-DAB, using several other laboratory and wild rats. We detected the presence of polymorphism at the same site of the M6p/Igf2r gene among these rats. It is likely that the polymorphism in exon 48 of the M6p/Igf2r gene is present broadly in rats since ancient times and not due to the mutation during the course of selection unless this site is a hot spot for chemical carcinogens.  相似文献   
63.
Lethality and physiological disorders induced by tritium beta particles were studied in rats. Newborn CD/Crj rats received i.p. HTO saline at 0, 8.14, 16.28, 24.42 and 32.56 MBq/g body weight (BW). At four weeks of age, HTO over 24.42 MBq/g BW was fatal, especially in male rats, but it was not obvious under 16.28 MBq/g BW. Surviving female rats were weaned at four weeks of age and rats were monitored for heart rate and blood pressure (systolic, mean and diastolic) at 13, 23 and 30 weeks of age and sacrificed. The blood pressure significantly increased with the administered doses of HTO. Sclerotic kidneys were frequently observed in hypertensive rats exposed to HTO over 24.42 MBq/g BW. Thickened intermediate layer of artery, infiltrating lymphocytes and atrophic mesangiums were observed in sclerotic kidneys. These results indicate that internal exposure to HTO as infants was induced consequent hypertension in association with sclerotic kidney at sublethal doses.  相似文献   
64.
The murine Lewis lung carcinoma 3LL cells give rise to spontaneous and experimental lung metastasis in C57BL/6 mice. Tumor cells maintained by serial subcutaneous transplantation in mice retain their ability to form lung metastasis, while cells carried in vitro loose metastatic potential with time. In order to obtain the non-metastatic subline, 3LL cells selected for its high lung colonization potential was grown continuously in vitro for 24 weeks. The present study was undertaken to characterize the expression of both urokinase-type plasminogen activator (uPA) and urinary trypsin inhibitor (UTI) in the non-metastatic (3LL(-)) and the metastatic (3LL(+)) cells. Both cells were tested on the Matrigel for invasive ability using a modified Boyden chamber and assayed for expression of uPA and UTI. The 3LL(+) cells secreted 5 times more uPA (6.25 mu g per 10(6) cells per 24 h) than the 3LL(-) cells (1.25 mu g per 10(6) cells per 24 h). The 3LL(+) cells, which expressed 2 times more cell-surface receptor-bound enzymatically active uPA (0.32 +/- 0.06 OD405) than the 3LL(-) cells (0.15 +/- 0.03 OD405), had larger amounts of cell-surface receptor-bound uPA. On the other hands, UTI levels in the conditioned media was decreased 25-fold in the 3LL(+) cells (0.05 mu g/10(6) cells/24 h) compared to the 3LL(-) cells (1.25 mu g/10(6) cells/24 h). The 3LL(-) cells expressed significantly higher levels of cell-associated UTI as indicated by a cell ELISA (3LL(+), 0.30 +/- 0.04 OD450; 3LL(-), 1.30 +/- 0.21 OD450) and by Western blot analysis. Metastatic competence in the 3LL(+) tumor model is associated with increased expression and release of uPA, as well as decreased UTI production, consistent with a more invasive phenotype. These data support our hypothesis that UTI may contribute to the inhibition of uPA expression in tumor cells.  相似文献   
65.
A case of Schonlein-Henoch-purpura is presented. The immunofluorescent study of skin lesions of the patient showed granular deposits of IgA and C3 in the blood vessel walls perivascular deposits of plasminogen and diffuse localization of fibrin and fibrinogen in the upper dermis. Complement activation via the alternative pathway through IgA, C3 and plasminogen deposits was suggested.  相似文献   
66.
BACKGROUND: Ketotic hypoglycemia is the most common cause of recurrent hypoglycemia in early childhood but its etiology is poorly understood. Elimination diets have been used for the prevention or treatment of some allergic diseases; however, these diets entail a risk to the normal nutrition and growth of children. The present study investigated whether elimination diets are related to the occurrence of ketotic hypoglycemia. METHODS: The prevalence of allergy treated with elimination diet therapy was retrospectively investigated in 18 patients with ketotic hypoglycemia seen in Yamaguchi University Hospital between January 1995 and September 1999. Data were gathered by reviewing the patients' medical charts. RESULTS: Ten (55.6%) of 18 patients with ketotic hypoglycemia had allergic diseases. Six (60%) of the patients had been treated with strict elimination diets and the others were on incomplete elimination diets for the prevention of allergy. The ketotic hypoglycemia patients with allergic diseases had experienced fewer pre-existing infectious diseases than those without allergic diseases. CONCLUSIONS: Patients with allergic diseases treated with elimination diets have a relatively high tendency towards developing ketotic hypoglycemia. They might have a lower capacity to tolerate fasting due to their excessive avoidance of many foods, even during periods when they are not undergoing strict elimination diets.  相似文献   
67.
68.
BACKGROUND: Induction of unresponsiveness to graft is one of major interest in xenotransplantation. Two different modalities [direct graft treatment by mitomycin C (MMC) and blockage of the lymphocyte function-associated antigen-1/intracellular adhesion molecule-1 (LFA-1/ICAM-1) pathway in recipients by species-specific mAbs] were tested for their ability to produce unresponsiveness to secondary islet xenografts. METHODS: Collagenase-digested WS (RT1k) rat islets, purified by Ficoll density gradient, were incubated for 30 min with MMC 10 microg/ml, cultured for 20 hr, and transplanted into the renal subcapsular space of streptozotocin-induced diabetic C57BL/6 (H-2b) mice. Recipient mice were divided into experimental groups according to anti-rat ICAM-1 and/or anti-mouse LFA-1 mAb treatment and transplantation of MMC-treated or nontreated islets. RESULTS: MMC pretreatment alone prolonged graft survival, with a mean survival time (MST) of 23.0+/-7.4 days, compared with that of cultured islets (12.4+/-2.7 days; P<0.01). MMC treatment of islets significantly augmented graft survival, compared with that of crude islet grafts under treatment with anti-donor ICAM-1 mAb (MST: >41.3+/-30 vs. 16.6+/-5.4 days, P<0.01), anti-recipient LFA-mAb (MST: >70.3+/-28.9 vs. 30.4+/-10.4 days, P<0.001), or both mAbs (MST: >88.1+/-24.1 vs. 23+/-7.4 days, P<0.0001). One of six, four of nine, and six of eight animals accepted MMC-treated islet xenografts over 100 days after treatment with anti-rat ICAM-1, anti-mouse LFA-1, or both mAbs treatments, respectively, whereas none of the animals accepted nontreated islets under the same treatment. When the mice bearing long-term functioning xenografts were challenged with the secondary graft from the original donor strain, the animals previously treated with anti-recipient LFA-1 and anti-donor ICAM-1 mAbs were more prone to accept it than animals given anti-recipient LFA-1 mAb alone (MST: 55.8+/-25.7 vs. 15+/-2.4 respectively; P<0.001), although they rejected the third-party xenograft and allograft acutely. CONCLUSIONS: In the xenogeneic islet transplantation model, MMC graft pretreatment and blockage of the ICAM-1/LFA-1 pathway constitute a potent protocol for inducing unresponsiveness to islet xenografts.  相似文献   
69.
OBJECTIVES: To compare health-related quality of life (HRQOL) in patients with a neobladder and in patients with an ileal conduit. METHODS: HRQOL was assessed using the SF-36 survey, supplemented with a questionnaire concerning micturition status. RESULTS: Patients (n = 36) with a neobladder were significantly younger at time of surgery and time of survey than patients with an ileal conduit (n = 20). Mean (+/- SD) follow-up periods for patients with a neobladder and with an ileal conduit were 31.3 +/- 33.1 and 44.8 +/- 30.7 months, respectively. No significant difference was apparent in any scale score between neobladder and ileal conduit groups. Role-physical functioning (RP) and role-emotional functioning (RE) scale scores in both neobladder and ileal conduit patients appeared to be below the general U.S. population norm. Patients with neobladder 65 years old or older (n = 17) showed significantly lower RP and RE scores than those younger than 65 years (n = 19; P <0.05). Duration of follow-up was not related to scale scores. Continence status did not measurably affect HRQOL. CONCLUSIONS: All scales concerning HRQOL except RP and RE were favorable with both neobladder and ileal conduit, and no significant differences were observed between these two types of urinary tract reconstruction. Generally, patients with a neobladder or an ileal conduit were satisfied with their overall quality of life and health.  相似文献   
70.
PURPOSE: To evaluate the prognostic value of vascular endothelial growth factor (VEGF)-D and VEGF receptor (VEGFR)-3 in endometrial carcinoma. EXPERIMENTAL DESIGN: We assessed the levels of immunoreactivity for VEGF-D and VEGFR-3 in 71 endometrial carcinomas, 14 complex atypical endometrial hyperplasias, and 16 normal endometria by immunohistochemistry. RESULTS: VEGF-D was stained in both tumor cells and adjacent stromal cells. VEGFR-3 was stained in both tumor cells and adjacent endothelial cells. Immunoreactivity for VEGF-D in tumor cells and adjacent stromal cells became significantly stronger as lesions progressed from normal endometrium to advanced carcinoma. Similarly, immunoreactivity for VEGFR-3 in tumor cells and adjacent endothelial cells was significantly greater as lesions progressed from normal endometrium to advanced carcinoma. A strong correlation was found between high levels of VEGF-D immunoreactivity in carcinoma cells and VEGFR-3 in both carcinoma cells and adjacent endothelial cells. Similarly, high levels of VEGF-D immunoreactivity in stromal cells were significantly correlated with those of VEGFR-3 in both carcinoma cells and endothelial cells. High levels of VEGF-D in carcinoma cells and stromal cells, as well as those of VEGFR-3 in carcinoma cells and endothelial cells, were significantly related to myometrial invasion and lymph node metastasis. A strong correlation was found between poor survival and high levels of VEGF-D in both carcinoma cells and stromal cells and between poor survival and high levels of VEGFR-3 in carcinoma cells. Moreover, the high levels of VEGF-D in stromal cells and VEGFR-3 in carcinoma cells were independent prognostic factors in endometrial carcinoma. CONCLUSIONS: The presence of VEGF-D and VEGFR-3 in endometrial carcinoma may predict myometrial invasion and lymph node metastasis and may prospectively identify patients who are at increased risk for poor outcome. In addition, VEGF-D and VEGFR-3 may be promising targets for new therapeutic strategies in endometrial carcinoma.  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