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   47808篇
  免费   2559篇
  国内免费   224篇
耳鼻咽喉   753篇
儿科学   2040篇
妇产科学   1357篇
基础医学   4380篇
口腔科学   1823篇
临床医学   4090篇
内科学   9663篇
皮肤病学   1000篇
神经病学   2988篇
特种医学   1710篇
外国民族医学   4篇
外科学   9469篇
综合类   914篇
现状与发展   3篇
一般理论   33篇
预防医学   2788篇
眼科学   1698篇
药学   3448篇
  1篇
中国医学   335篇
肿瘤学   2094篇
  2024年   54篇
  2023年   548篇
  2022年   1111篇
  2021年   1776篇
  2020年   1108篇
  2019年   1398篇
  2018年   1860篇
  2017年   1378篇
  2016年   1521篇
  2015年   1560篇
  2014年   2012篇
  2013年   2548篇
  2012年   3742篇
  2011年   3846篇
  2010年   2113篇
  2009年   1692篇
  2008年   2814篇
  2007年   3037篇
  2006年   2770篇
  2005年   2638篇
  2004年   2377篇
  2003年   2061篇
  2002年   1848篇
  2001年   709篇
  2000年   747篇
  1999年   527篇
  1998年   286篇
  1997年   194篇
  1996年   193篇
  1995年   141篇
  1994年   119篇
  1993年   92篇
  1992年   171篇
  1991年   174篇
  1990年   137篇
  1989年   128篇
  1988年   110篇
  1987年   102篇
  1986年   93篇
  1985年   121篇
  1984年   77篇
  1983年   57篇
  1982年   56篇
  1981年   58篇
  1980年   45篇
  1979年   58篇
  1978年   49篇
  1977年   37篇
  1976年   39篇
  1974年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Bone scintigraphy in tuberculous sacroiliitis   总被引:1,自引:0,他引:1  
Radionuclide bone imaging is becoming increasingly important in the evaluation of musculoskeletal pain of uncertain cause. A case in which Tc-99m MDP bone imaging was employed to investigate complaints of low back pain is presented. Scan abnormalities directed clinicians towards appropriate further workup and diagnosis of unilateral tuberculous sacroiliitis.  相似文献   
52.
3,4-Methylenedioxymethamphetamine damages fine serotonergic fibers and nerve terminals in adult organisms. Developing animals seem to be less susceptible to this effect, possibly due to a lack of drug-induced hyperthermia. We tested this hypothesis by producing hyperthermia in neonatal rats for 2 h after each of twice-daily MDMA (10 mg/kg s.c.) or saline injections administered from postnatal days 1–4. Other drug-treated and control litters were maintained at normothermic temperatures following injection. Changes in forebrain serotonergic innervation were assessed at postnatal day 25 (serotonin transporter binding and serotonin levels), postnatal day 60 (serotonin transporter binding), and 9 months of age (serotonin transporter immunohistochemistry). We also determined the influence of MDMA treatment on apoptotic activity by means of immunohistochemistry for cleaved caspase-3 at postnatal day 5. The hippocampus showed significant MDMA-related reductions in serotonergic markers at postnatal day 25 and postnatal day 60. At 9 months, there was no effect of prior MDMA exposure on serotonin transporter-immunoreactive fiber density in the hippocampus; however, significant reductions in fiber density were observed in two neocortical areas and a hyperinnervation was found in the caudate-putamen and nucleus accumbens shell. MDMA treatment also produced a two-fold increase in the number of cleaved caspase-3-immunoreactive cells in the rostral forebrain and hippocampus. All of these effects were completely independent of pup body temperature. These findings demonstrate that neonatal MDMA administration exposure stimulates apoptotic cell death in various forebrain areas and also leads to a long-term reorganization of the forebrain serotonergic innervation. Consequently, offspring of MDMA-using women may be at heightened risk for abnormal neural and behavioral development.  相似文献   
53.
54.
BACKGROUND AND AIM OF STUDY: Cardioplegic arrest remains the method of choice for myocardial protection in cardiac surgery. Caffeic acid phenethyl ester (CAPE) prevents lipid peroxidation induced by ischemia-reperfusion injury and has a potent antioxidant property. We investigated the advantages of CAPE supplemented cardioplegic solution (St. Thomas' Hospital cardioplegic solution No.: 2) on the antioxidant defense system of myocardium against ischemia-reperfusion injury. MATERIAL AND METHODS: Isolated rat hearts were mounted on a nonrecirculating type of Langendorff apparatus. The hearts were arrested for 60 min with cardioplegic solution given at 20-min intervals and then reperfused for 15 min. The hearts were divided into three groups. Cold saline (0.9%, 4 degrees C) in group 1, St. Thomas' Hospital solution in group 2 and CAPE added St. Thomas' Hospital solution in group 3 were used as the cardioplegic solution. Krebs-Henseleit buffer solution was used for reperfusion. The tissues were examined biochemically for oxidative stress. RESULTS: Significant differences among the three groups existed in tissue myeloperoxidase (MPO), catalase (CAT), Na+-K+ ATPase activity and in the concentrations of malonydealdehyde (MDA) and 3-nitrotyrosine (3-NT). Group 2 showed significant changes in MPO (P = 0.04), Na+-K+ ATPase enzyme activity (P = 0.02) and the levels of MDA (P = 0.004) and 3-NT (P = 0.01) in comparison with group 1. Group 3 efficiently reduced MDA levels (P = 0.004) and also led to significant decrease in levels of MPO (P = 0.006), 3-NT (P = 0.01) and Na+-K+ ATPase activity (P = 0.01) and increase in the level of CAT (P = 0.004) in comparison with group 1. Significant changes were also found in the levels of MDA (P = 0.03), MPO (P = 0.04) and CAT (P = 0.009) in comparison between groups 2 and 3. CONCLUSIONS: We demonstrated that the administration of CAPE into cardioplegic solutions improves the antioxidant defense system of rat heart during the ischemia-reperfusion injury.  相似文献   
55.
Rhesus monkeys exposed to marijuana smoke either 7 or 2 days/weeks (HI and LO groups, respectively), or ethanol-extracted marijuana smoke for 7 days/week (EM) or sham treatment (SH) for 1 year were sacrificed 7 months following the last exposure. Pulmonary levels of carcinogen-DNA adducts were determined. Although mean or median adduct levels were not statistically different, 15 of 22 adduct measures were highest in the EM group and lowest 12 of 22 times in the SH group. The levels of aromatic carcinogen-DNA adducts seem no higher in the lungs of animals exposed to marijuana smoke than in untreated animals. Ethanol-extracted marijuana may have effects greater than marijuana itself.  相似文献   
56.
OBJECTIVE: Heart failure (HF) and depression are both common in older adults, and the presence of depression is known to worsen HF outcomes. For community-dwelling older adults, admission to a nursing home (NH) is associated with loss of independent living and poor outcomes. The objective of this study was to examine the effect of depression on NH admission for older adults with HF. METHODS: Using the 2001-2003 National Hospital Discharge Survey datasets, the authors identified all community-dwelling older adults who were discharged alive with a primary discharge diagnosis of HF. The authors then identified those with a secondary diagnosis of depression. Using a multivariable logistic regression model, the authors then determined probability or propensity to have depression for each patient. The authors used propensity scores for depression to match all 680 depressed patients with 2,040 nondepressed patients. Finally, the authors estimated the association between depression and NH admission using bivariate and multivariable logistic regression analyses. RESULTS: Patients had a mean (+/- standard deviation) age of 79 (+/- 8) years, 72% were women, and 9% were blacks. Compared with 17% nondepressed patients, 25% depressed patients were discharged to a NH. Depression was associated with 50% increased risk of NH admission (unadjusted relative risk [RR]: 1.50; 95% confidence interval [CI]: 1.28-1.74). The association became somewhat stronger after multivariable adjustment for various demographic and care covariates (adjusted RR: 1.60; 95% CI: 1.35-1.68). CONCLUSION: In ambulatory older adults hospitalized with HF, a secondary diagnosis of depression was associated with a significant increased risk of NH admission.  相似文献   
57.
OBJECTIVE: Iatrogenic Oesophageal perforations are a dreaded complication and there is no consensus as to their best management. The aim of our study was to assess the results of conservative management in these cases. METHODS: Twenty-six patients with iatrogenic perforations of the oesophagus treated over a 10-year period were reviewed retrospectively. They were managed conservatively by keeping them nil by mouth on intravenous fluids and intravenous antibiotics. Out of these 26, nine were patients of carcinoma of the oesophagus while the remaining 17 had benign pathologies. Twenty-two were diagnosed within 6h, while the remaining four were diagnosed over 24h after perforation. Twenty-three of the 26 were caused by oesophageal dilatations. RESULTS: Twenty-two (84.6%) of the 26 survived on this regimen. Out of the four that died, two had advanced carcinomas and died of chest complications, one died of a myocardial infarction and the fourth was an old debilitated man who died of renal failure. All four who died had extension of the leak into the pleural cavity. Early diagnosis and treatment is of critical importance and is only possible by maintaining a high index of suspicion. CONCLUSIONS: Conservative management when applied to cases of iatrogenic oesophageal perforations gives results comparable to or better that those reported in series where early surgical intervention was practised. Extension of the leak into the pleura carries a worse prognosis.  相似文献   
58.
In this study we have investigated the negative influence of CO2 and Nd-YAG laser irradiation on rapid cranial regeneration and whether it has any use in certain types of craniosynostosis. Twenty-two newborn rats were used in the study. Both CO2 and Nd-YAG laser irradiation, which was applied to free bony edges after, suturectomies, resulted in a significant decrease in skull regeneration. Histopathological examinations revealed severe degeneration caused by both types of laser energies.  相似文献   
59.
60.
Retention is a major part of orthodontic treatment, not an optional secondary protocol. In recent years, studies investigating dentofacial changes during and after the growth period have led most clinicians to use fixed retention appliances after treatment. Fixed retainers can be attached to the teeth directly or indirectly. We present a practical, indirect method for bonding fixed retainers, using Sondhi Rapid-set Indirect Bonding Adhesive (3M Unitek, Monrovia, Calif).  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