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   1775篇
  免费   98篇
  国内免费   11篇
耳鼻咽喉   2篇
儿科学   41篇
妇产科学   10篇
基础医学   270篇
口腔科学   70篇
临床医学   102篇
内科学   444篇
皮肤病学   22篇
神经病学   77篇
特种医学   71篇
外科学   333篇
综合类   16篇
预防医学   70篇
眼科学   42篇
药学   90篇
中国医学   2篇
肿瘤学   222篇
  2023年   31篇
  2022年   46篇
  2021年   56篇
  2020年   37篇
  2019年   45篇
  2018年   59篇
  2017年   38篇
  2016年   52篇
  2015年   55篇
  2014年   71篇
  2013年   84篇
  2012年   110篇
  2011年   118篇
  2010年   59篇
  2009年   36篇
  2008年   58篇
  2007年   70篇
  2006年   71篇
  2005年   69篇
  2004年   60篇
  2003年   55篇
  2002年   59篇
  2001年   30篇
  2000年   42篇
  1999年   39篇
  1998年   23篇
  1997年   14篇
  1996年   14篇
  1995年   12篇
  1994年   8篇
  1993年   19篇
  1992年   24篇
  1991年   18篇
  1990年   19篇
  1989年   25篇
  1988年   30篇
  1987年   28篇
  1986年   22篇
  1985年   19篇
  1984年   13篇
  1983年   9篇
  1982年   8篇
  1980年   8篇
  1979年   18篇
  1978年   16篇
  1977年   12篇
  1975年   11篇
  1974年   8篇
  1973年   8篇
  1972年   8篇
排序方式: 共有1884条查询结果,搜索用时 15 毫秒
101.
Post-initiation modifying effects of dietary administration of a super critical extract of propolis on major organs were examined using a two-stage carcinogenesis model. Groups of 21 or 22 F344 female rats were treated sequentially with 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN, i.g.), 7,12-dimethylbenz[a]anthracene (DMBA, i.g.), 1,2-dimethylhydrazine (DMH, s.c.) and N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, in drinking water) during the first 3 weeks for initiation, and then administered diet containing 0.1 or 0.01% propolis for 33 weeks. Further groups were treated with the carcinogens alone, 0.1% propolis alone or basal diet alone. All surviving animals were killed at week 36, and major organs were examined histopathologically for development of preneoplastic and neoplastic lesions. The incidence and multiplicity of mammary carcinomas were significantly decreased by the 0.1 and 0.01% propolis treatments. In the urinary bladder, the incidence of PN hyperplasia but not tumors was, in contrast, significantly increased by 0.1% propolis. Similarly, the number and area of glutathione S-transferase placental form (GST-P)-positive liver foci were significantly elevated with this high dose. The results indicate that a low dose of a super critical extract of propolis may find application as a potent chemopreventor of mammary carcinogenesis.  相似文献   
102.
103.

Background

Neuropsychological studies have demonstrated that cognitive dysfunction represents pathophysiological mechanisms underlying bipolar disorder. However, information processing deficits in bipolar disorder have not often been examined electrophysiologically. Here, we examined preattentive processing and sensory information processing using mismatch field (MMNm) and P1m components, respectively, using magnetoencephalography.

Methods

Ten patients with bipolar disorder and 20 healthy volunteers participated in the study. The participants were presented with auditory stimuli sequences comprising standard and deviant stimuli. MMNm was elicited in response to changes in duration and frequency of pure-tone stimuli and a vowel across-category change.

Results

The magnetic global field power of MMNm in the right hemisphere under the pure-tone condition was significantly delayed in patients with bipolar disorder compared to healthy volunteers, and that of P1m did not differ between the two groups. The MMNm dipole in the left hemisphere was located inferior in patients with bipolar disorder than in healthy volunteers. This finding did not correlate with clinical symptoms.

Conclusions

Information processing at the preattentive level is impaired in patients with bipolar disorder irrespective of clinical symptoms, and this dysfunction is not due to sensory level dysfunction. The quality of preattentive information processing impairment is different between patients with bipolar disorder and patients with major depressive disorder, as shown by the MMNm latency and power differences.  相似文献   
104.
Background:  The aim of the present study was to assess 3 year auditory and neurodevelopmental outcomes of persistent pulmonary hypertension of the newborn (PPHN) before and after introducing inhaled nitric oxide (i-NO) therapy, and to detect the clinical factors affecting poor outcome.
Methods:  A retrospective historical cohort study of 26 survivors with PPHN with oxygenation index (OI) ≥25 (13 infants without i-NO therapy, control group; 13 with i-NO therapy, i-NO group) was performed. Auditory brainstem response (ABR) at 6 and 12 months and neurodevelopmental outcomes at 3 years of age were evaluated.
Results:  ABR abnormalities at 6 months were observed in one infant in the i-NO group and six in the control group ( P  = 0.04). At 1 year, one infant in the i-NO group and two of six infants in the control group still had ABR abnormality. In the i-NO group, two children had abnormal neurodevelopmental outcomes, as compared with five children in the control group at 3 year follow up. Two children in the control group and no children in the i-NO group had hearing loss at 3 years of age. Hypocapnea ( P  = 0.04) and elevated creatine phosphokinase ( P  = 0.04) were found to be most predictive for neurodevelopmental abnormality.
Conclusion:  Avoidance of excessive hypocapnea via introduction of i-NO therapy might reduce both ABR and neurodevelopmental abnormalities.  相似文献   
105.
Although lithium–sulfur (Li–S) batteries are a promising secondary power source, it still faces many technical challenges, such as rapid capacity decay and low sulfur utilization. The loading of sulfur and the weight percentage of sulfur in the cathode usually have a significant influence on the energy density. Herein, we report an easy synthesis of a self-supporting sulfur@graphene oxide-few-wall carbon nanotube (S@GO–FWCNT) composite cathode film, wherein an aluminum foil current collector is replaced by FWCNTs and sulfur particles are uniformly wrapped by graphene oxide along with FWCNTs. The 10 wt% FWCNT matrix through ultrasonication not only provided self-supporting properties without the aid of metallic foil, but also increased the electrical conductivity. The resulting S@GO–FWCNT composite electrode showed high rate performance and cycle stability up to ∼385.7 mA h gelectrode−1 after 500 cycles and close to ∼0.04% specific capacity degradation per cycle, which was better than a S@GO composite electrode (353.1 mA h gelectrode−1). This S@GO–FWCNT composite self-supporting film is a promising cathode material for high energy density rechargeable Li–S batteries.

We report a synthesis of a self-supporting composite cathode film, wherein aluminum foil current collector is replaced by FWCNTs and sulfur particles are uniformly wrapped by graphene oxide along with FWCNTs.  相似文献   
106.
One of the possible causes of enhanced atherosclerosis in patients with chronic kidney disease (CKD) is the accumulation of uremic toxins. Since macrophage foam cell formation is a hallmark of atherosclerosis, we examined the direct effect of indoxyl sulfate (IS), a representative uremic toxin, on macrophage function. Macrophages differentiated from THP-1 cells were exposed to IS in vitro. IS decreased the cell viability of THP-1 derived macrophages but promoted the production of inflammatory cytokines (IL-1β, IS 1.0 mM: 101.8 ± 21.8 pg/mL vs. 0 mM: 7.0 ± 0.3 pg/mL, TNF-α, IS 1.0 mM: 96.6 ± 11.0 pg/mL vs. 0 mM: 15.1 ± 3.1 pg/mL) and reactive oxygen species. IS reduced macrophage cholesterol efflux (IS 0.5 mM: 30.3% ± 7.3% vs. 0 mM: 43.5% ± 1.6%) and decreased ATP-binding cassette transporter G1 expression. However, lipid uptake into cells was not enhanced. A liver X receptor (LXR) agonist, T0901317, improved IS-induced production of inflammatory cytokines as well as reduced cholesterol efflux. In conclusion, IS induced inflammatory reactions and reduced cholesterol efflux in macrophages. Both effects of IS were improved with activation of LXR. Direct interactions of uremic toxins with macrophages may be a major cause of atherosclerosis acceleration in patients with CKD.  相似文献   
107.
Fukuda M  Hamada S  Liu C  Shimomura Y 《Cornea》2008,27(Z1):S56-S61
Osteo-odonto-keratoprosthesis (OOKP) is a keratoprosthesis technique in which the patient's own tooth root is used to support an optical cylinder. It was invented by Strampelli in 1963 and modified and established by Falcinelli about 10 years later. This method is particularly useful for restoring sight in end-stage Stevens-Johnson syndrome (SJS) and ocular cicatricial pemphigoid (OCP). We started performing OOKP surgery in June 2003 supported by Dr Christopher Liu of Sussex Eye Hospital, Brighton, UK. Till now, we have performed 4 OOKP surgeries for end-stage SJS and OCP. We modified the original method by using artificial buccal mucous membranes to the bone and buccal mucous membrane defects for better wound healing. Case 1 was a 49-year-old woman (SJS), and the corrected visual acuity was 0.5 in 4 years 8 months. Case 2 was a 68-year-old woman (SJS), and the corrected visual acuity was 0.04 in 3 years 10 months. Case 3 was a 63-year-old man (SJS), and the corrected visual acuity was 0.1 in 3 years 2 months. Case 4 was a 71-year-old woman (OCP), and the corrected visual acuity was 0.04 in 1 year 3 months. Despite some minor optical cylinder troubles such as MRSA colonization, tilting, and buccal mucous coverage, their visual acuities were stable without any serious complications. It was demonstrated that OOKP is useful for visual rehabilitation and durable with minimum eye care for severe ocular surface diseases.  相似文献   
108.
BACKGROUND: We investigated the relationship between the retinal thickness and electroretinogram (ERG) components in patients with central retinal artery occlusion (CRAO). METHODS: The optical coherence tomographic (OCT) images and ERGs of the nine patients (six men and three women; mean age, 61.8 years) were retrospectively analyzed. The thickness of the inner and outer retinal layers at 1 and 2 mm nasal and temporal to the fovea was measured in the horizontally scanned OCT images. The ratio of the inner layer thickness/sensory retinal thickness (IT/ST ratio) was calculated. The amplitudes of the a- and b-waves of the mixed rod-cone ERGs and the photopic negative response (PhNR) of the photopic ERGs were analyzed. The ratio of the amplitude of each component in the affected eye to that of the healthy fellow eye (a/f ratio) was calculated. RESULTS: In the chronic phase (1 to 8 months after onset, eight eyes), the inner layer was significantly thinner than that in the acute phase (P = 0.0147, 0.0076, 0.002, and 0.0003 for 2 mm nasal, 1 mm nasal, 1 mm temporal, and 2 mm temporal respectively, within 5 days of onset, six eyes), while the thickness of outer layer was not significantly changed. The ERGs were recorded 6.4 +/- 1.5 days after the onset of CRAO. The median of the a/f ratio was 0.84 in the a-wave, 0.56 in the b-wave, and 0.27 in the PhNR. The IT/ST in the chronic phase was positively correlated with the a/f ratio of the amplitude of the PhNR. CONCLUSIONS: Measurement of retinal thickness by OCT can be useful for monitoring the changes following CRAO. The correlation between the retinal thickness, especially inner layer thickness, and the ERG components was determined, suggesting that the PhNR in the acute phase might be a good indicator for predicting the thinning of the damaged retina in the chronic phase.  相似文献   
109.
Deformable image registration (DIR) is fundamental technique for adaptive radiotherapy and image-guided radiotherapy. However, further improvement of DIR is still needed. We evaluated the accuracy of B-spline transformation-based DIR implemented in elastix. This registration package is largely based on the Insight Segmentation and Registration Toolkit (ITK), and several new functions were implemented to achieve high DIR accuracy. The purpose of this study was to clarify whether new functions implemented in elastix are useful for improving DIR accuracy. Thoracic 4D computed tomography images of ten patients with esophageal or lung cancer were studied. Datasets for these patients were provided by DIR-lab (dir-lab.com) and included a coordinate list of anatomical landmarks that had been manually identified. DIR between peak-inhale and peak-exhale images was performed with four types of parameter settings. The first one represents original ITK (Parameter 1). The second employs the new function of elastix (Parameter 2), and the third was created to verify whether new functions improve DIR accuracy while keeping computational time (Parameter 3). The last one partially employs a new function (Parameter 4). Registration errors for these parameter settings were calculated using the manually determined landmark pairs. 3D registration errors with standard deviation over all cases were 1.78 (1.57), 1.28 (1.10), 1.44 (1.09) and 1.36 (1.35) mm for Parameter 1, 2, 3 and 4, respectively, indicating that the new functions are useful for improving DIR accuracy, even while maintaining the computational time, and this B-spline-based DIR could be used clinically to achieve high-accuracy adaptive radiotherapy.  相似文献   
110.
Gemcitabine is widely used for the treatment of advanced biliary tract cancer (BTC) as first-line chemotherapy. However, there is no standard chemotherapy for patient with advanced BTC refractory to gemcitabine. We conducted a multicenter phase II study of S-1 monotherapy as second-line chemotherapy for patients with advanced BTC that were refractory to gemcitabine. S-1 was administered orally at a dose of 80 mg/m(2) for 28 days, followed by 14 days of rest. This regimen was repeated every 6 weeks. Tumor response was assessed every two cycles using the Response Evaluation Criteria in Solid Tumors version 1.0. Twenty-two patients were enrolled between March 2007 and January 2010, with 14 patients (64%) representing cases of recurrence after surgery. The overall response rate was 22.7%, and the overall disease control rate was 50.0%. The median overall survival time was 13.5 months (95% CI, 7.1-23.1 months) and the median time-to-progression was 5.4 months (95% CI, 2.6-17.2 months). Grade 3/4 toxicities included neutropenia (5%) and anemia (5%). The most common non-hematological toxicities were nausea (27%), anorexia (55%), and pigmentation (32%). In conclusion, S-1 monotherapy is feasible and moderately efficacious second-line chemotherapy for advanced BTC.  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