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   9208篇
  免费   451篇
  国内免费   32篇
耳鼻咽喉   57篇
儿科学   197篇
妇产科学   131篇
基础医学   1252篇
口腔科学   344篇
临床医学   602篇
内科学   2305篇
皮肤病学   149篇
神经病学   665篇
特种医学   401篇
外科学   1457篇
综合类   53篇
预防医学   278篇
眼科学   213篇
药学   594篇
中国医学   8篇
肿瘤学   985篇
  2023年   55篇
  2022年   93篇
  2021年   174篇
  2020年   64篇
  2019年   143篇
  2018年   174篇
  2017年   147篇
  2016年   149篇
  2015年   160篇
  2014年   214篇
  2013年   275篇
  2012年   477篇
  2011年   507篇
  2010年   257篇
  2009年   264篇
  2008年   481篇
  2007年   522篇
  2006年   442篇
  2005年   467篇
  2004年   449篇
  2003年   442篇
  2002年   500篇
  2001年   294篇
  2000年   306篇
  1999年   220篇
  1998年   86篇
  1997年   92篇
  1996年   77篇
  1995年   82篇
  1994年   71篇
  1993年   50篇
  1992年   179篇
  1991年   159篇
  1990年   164篇
  1989年   146篇
  1988年   136篇
  1987年   149篇
  1986年   141篇
  1985年   133篇
  1984年   81篇
  1983年   70篇
  1982年   58篇
  1979年   61篇
  1978年   42篇
  1977年   33篇
  1975年   30篇
  1974年   49篇
  1973年   30篇
  1972年   40篇
  1969年   34篇
排序方式: 共有9691条查询结果,搜索用时 15 毫秒
91.
We report the anesthetic management for stents placement in patients with tracheobronchial stenosis. The subjects were 6 patients with lung cancer and one patient with tracheal invasion of esophageal cancer. Anesthesia was induced with propofol, fentanyl and vecuronium, and maintained with propofol and vecuronium. After intubation, tracheostomy was performed. The patients were kept apnic during insertion of stents. Three patients had dynamic stents inserted from tracheostomy site and one orally. Three patients had Dumon stents inserted orally, but the procedure in one patient was cancelled because her stent could not be placed at appropriate position. We recommend the anesthetic management through the tracheostomy site for the placement of Dumon tubes or dynamic stents.  相似文献   
92.
The proximal isovelocity surface area (PISA) method for calculating volume flow through the regurgitant orifice has attracted significant attention. A number of in vitro studies and clinical studies in adults suggest that the method is accurate. However, when applying the method to children it must be noted that the absolute regurgitation volume is small, and the range of body sizes is wide. This study investigated the accuracy of the PISA method for quantitative assessment of the severity of mitral regurgitation in children. Twenty children aged 7 months to 12 years (average 4.7 years) with mitral regurgitation but without interventricular shunt or aortic stenosis were selected for this study. Underlying cardiac diseases included atrioventricular septal defects in nine, isolated mitral regurgitation in five, and association with other heart defects in six. The PISA radius (r) and the duration of regurgitation (T) were measured on color M-mode recordings, with the M line passing through the center of the PISA. Assuming that the PISA is a hemisphere, maximal regurgitant flow rate (MFR: ml/s) was calculated as MFR = 2π×~ r 2×~ V (r= maximal radius, V= aliasing velocity), and regurgitant stroke volume (RSVpisa) as RSVpisa = 2π×~ MSR ×~ V×~ T (MSR = mean square of the PISA radius during regurgitation). As a validating standard, total stroke volume (TSV) using two-dimensional echocardiography determined by the area–length volumetry method and forward stroke volume (FSV) by the pulsed Doppler method were measured, and regurgitant stroke volume (RSVD: RSVD= TSV − FSV) and regurgitant fraction (RF: RF = RSVD/TSV) were calculated. A linear correlation was found between MFR, RSVpisa, and RSVD (X) (MFR = 4.2X + 54.0, r= 0.84. RSVpisa = 1.0X + 9.8, r= 0.90), and both RSVpisa and MFR divided by body surface area (BSA: m2) revealed a significant correlation with regurgitant fraction (X) by nonlinear regression analysis (RSVpisa/BSA = 26.2 ×~ X/(1 − X) + 16.8, r= 0.85. MFR/BSA = 121.8 ×~ X/(1 − X) + 92.2, r= 0.79). It is concluded that maximal regurgitant flow rate, regurgitant stroke volume, and regurgitant fraction can be accurately predicted in children using the PISA method by Doppler echocardiography.  相似文献   
93.
An extremely rare case of clear cell adenocarcinoma of the uterine cervix in pregnancy is reported. The primary lesion was first found at 34 weeks of pregnancy in a 34-year-old patient, and was cytologically suspected to be malignant. At 39 weeks of pregnancy, the patient underwent abdominal cesarean section concomitantly with removal of huge right ovarian tumor (3050 g) and delivered a normal male baby weighing 3590 g. Histological findings for cone biopsy at 22 days postpartum revealed invasive adenocarcinoma, and abdominal radical hysterectomy and pelvic lymphoadenectomy were performed at 36 days postpartum. Microscopically, the tumor tissue was composed of clear and hobnail-type cells. It showed a considerable amount of PAS-positive diastase-labile glycogen but was only weakly positive for immunoperoxidase staining of carcinoembryonic antigen.  相似文献   
94.
95.
We have examined the suppressive effect of herbimycin A on the reduction of gap-junctional Intercellular communication that is induced by a tumor-promoting phorbol ester in 3T3-L1 cells. Most cells in growth arrest participated in dye-coupling, as evaluated by the transfer between cells of a fluorescent dye (Lucifer Yellow CH). Treatment of cells with 0.25 μg/ml herbimycin A slightly enhanced the dye-coupling. This enhancement required treatment for periods as long as 24 h. Addition of 100 ng/ml 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a rapid reduction of dye-coupling. However, addition of TPA did not suppress dye-coupling in cells pretreated for more than 24 h with herbimycin A. Pretreatment of cells for less than 6 h with herbimycin A did not suppress the TPA-induced reduction of dye-coupling. These results suggest that herbimycin A suppresses the reduction of gap-junctional intercellular communication that is induced by TPA through enhancement of the ability of the cells to participate in gap-junctional intercellular communication  相似文献   
96.
97.
98.
Objective To evaluate the relationship between dietary folate intake and genetic polymorphisms of 5, 10-methylenetetrahydrofolate reductase (MTHFR) with reference to breast cancer risk. Methods A case-control study was conducted with 669 cases and 682 population-based controls in Jiangsu province of China. MTHFR C677T and AI298C genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Dietary folate intake was assessed by using an 83-item food frequency questionnaire. Odds ratios (OR) were estimated with an unconditional logistic model. Results The frequencies of MTHFR C677T C/C, C/T and T/T genotypes were 32. 37% (202/624), 48. 88% (3051624) and 18. 75% (117/624) in cases and 37. 66% (235/624), 48.24% (301/624) and 14. 10% (88/624) in controls,respectively. The difference in distribution was significant (X2=6. 616, P=0. 037), the T/T genotype being associated with an elevated OR for breast cancer (1.62, 95% CI: 1.14 -2. 30). The frequencies of MTHFR A1298C A/A,A/C and C/C were 71.47% (446/624), 27.08% (169/624) and 1.44% (9/624) in cases and 68. 11% (425/624) ,30. 13% (188/624) and 1.76% (11/624) in controls, with no significant differences found (X2=1.716, P=0. 424). Folate intake of cases [(263.00±137. 38)μg/d]was significantly lower than that of controls [(285. 12±149. 61)μg/d](t=-2. 830,P=0. 005). Compared with the lowest tertile (≤199. 08μg/d) of folate intake,the adjusted OR for breast cancer in the top tertile (≥315.μg/d) was 0. 70 (95% CI:0. 53 -0. 92). Among individuals with the MTHFR A1298C A/A genotype,adjusted OR for breast cancer were 0. 89 (95% CI: 0. 62 -1.27)and 1.69 (95% CI: 1.20 -2. 36) for the second to the third tertite of folato intake compared with thehighest folate intake group (Xtrend2=11. 372, P=0. 001). Conclusion The findings of the present study suggest that MTHFR genetic polymorphisms, and dietary intake of folate may modify susceptibility to breast cancer.  相似文献   
99.
The antiobesity effects of (S)-(+)-1-(4-chlorophenylthiomethyl)-N-methylethylamine fumarate (AO-124) were examined in rats and dogs. AO-124 suppressed food intake dose dependently in normal, Zucker fatty and VMH-obese rats, and beagle dogs. Its anorectic activity was not altered by pretreatment with methysergide, a serotonin receptor blocker. AO-124 also reduced the hyperphagia induced by 2-deoxy-D-glucose but not that induced by insulin, noradrenaline or muscimol, suggesting that the anoretic mechanism of AO-124 may be implicated in a glucostatic regulatory system of feeding. In addition, AO-124 decreased insulin secretion in response to an oral, but not an intravenous, glucose load. Such a suppression in insulin secretion may be explained by slow absorption of glucose from the intestine: AO-124 delayed the gastric emptying time of glucose and inhibited the active transport of glucose as observed in the everted small intestine. Two week administration of AO-124 to Zucker fatty rats resulted in a significant reduction of plasma insulin levels, body weight gain, and body lipid without exerting any changes in body protein. These findings indicate that AO-124 may be useful as an antibesity agent on the basis of its unique mechanisms of action.  相似文献   
100.
On a single po administration of the four chiral isomers of fenvalerate ([RS]-alpha-cyano-3-phenoxybenzyl [RS]-2-(4-cholorophenyl)isovalerate) to rats and mice at 2.5 mg/kg, the [2R, alpha S]-isomer showed relatively higher residues in all analyzed tissues as compared with the other three isomers. Similarly, this isomer showed higher tissue concentrations than other isomers when mice were fed a diet containing 500 ppm of the [2S, alpha S]-, and [2R, alpha R]-isomers for 2 weeks. The [2R, alpha S]-isomer produced a lipophilic metabolite in all the examined tissues on the basis of thin-layer chromatography analysis, but not for the other isomers. The amounts of lipophilic metabolite differed among tissues, being higher in adrenal, liver, and mesenteric lymph nodes following feeding to mice at 500 ppm of the [2R, alpha S]-isomer for 2 weeks. However, the amount did not increase proportionally with time and apparently reached a plateau within a rather short time. This metabolite was identified as cholesteryl [2R]-2-(4-chlorophenyl)isovalerate ([2R]-CPIA-cholesterol ester) on the basis of spectroanalysis and chromatographic behavior after purification on silica gel, Florisil, thin-layer, and high-pressure liquid chromatography. The presence of the same metabolite also was indicated in rat tissues. The CPIA-cholesterol ester was rapidly formed and found in all the analyzed tissues of mice 1 hr after a single po administration of the [2R, alpha S]-isomer.  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