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   13381篇
  免费   829篇
  国内免费   167篇
耳鼻咽喉   248篇
儿科学   86篇
妇产科学   152篇
基础医学   2449篇
口腔科学   346篇
临床医学   1112篇
内科学   2414篇
皮肤病学   489篇
神经病学   1151篇
特种医学   766篇
外科学   1794篇
综合类   44篇
一般理论   2篇
预防医学   503篇
眼科学   303篇
药学   1411篇
中国医学   185篇
肿瘤学   922篇
  2024年   9篇
  2023年   92篇
  2022年   368篇
  2021年   571篇
  2020年   244篇
  2019年   378篇
  2018年   445篇
  2017年   345篇
  2016年   481篇
  2015年   650篇
  2014年   776篇
  2013年   862篇
  2012年   1277篇
  2011年   1188篇
  2010年   746篇
  2009年   621篇
  2008年   867篇
  2007年   833篇
  2006年   708篇
  2005年   632篇
  2004年   504篇
  2003年   424篇
  2002年   362篇
  2001年   229篇
  2000年   195篇
  1999年   137篇
  1998年   64篇
  1997年   47篇
  1996年   32篇
  1995年   27篇
  1994年   20篇
  1993年   18篇
  1992年   35篇
  1991年   31篇
  1990年   32篇
  1989年   23篇
  1988年   16篇
  1987年   16篇
  1986年   8篇
  1985年   8篇
  1984年   10篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1979年   7篇
  1978年   5篇
  1977年   5篇
  1976年   5篇
  1969年   2篇
  1968年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Four new 3-methyl-4-ethylideneproline-containing peptides, lucentamycins A-D (1-4), have been isolated from the fermentation broth of a marine-derived actinomycete identified by phylogenetic methods as Nocardiopsis lucentensis (strain CNR-712). The planar structures of the new compounds were assigned on the basis of 1D and 2D NMR spectroscopic techniques, while the absolute configurations of the amino acid residues were determined by application of the advanced Marfey method. Lucentamycins A (1) and B (2) showed significant in vitro cytotoxicity against HCT-116 human colon carcinoma.  相似文献   
52.

Purpose

We investigated the effect of muscle relaxants (atracurium) on the outcomes of intermittent exotropia surgery under general anesthesia, with a focus on resection procedures.

Methods

Thirty four patients who underwent recession and resection (R&R) were divided into two groups: atracurium usage (group A, n=18) and no atracurium usage (group B, n=16). Patients were divided into two subgroups according to the amount of resection of the medial rectus (MR): less than 5 mm (group 1, n=13) or 5 mm and greater (group 2, n=21). Deviation angles were compared between groups and subgroups. Surgical outcome was defined as successful if distant deviation angles were equal to or less than 10 prism diopters.

Results

The overall postoperative deviation angles did not show statistically significant differences between groups A and B. However, in patients with larger MR resections (≥ 5 mm), the 1 week postoperative distant deviation was significantly larger in group A (1.8±2.6 PD) than in group B (-1.6±4.6 PD, p=0.048 by t-test). The overall undercorrection rate at 3 months postoperatively for group A was 16.7%, which was higher than that of group B (6.3%), and the difference was even larger in subgroups with larger MR resections (≥ 5 mm): 18.2% in group A and 0% in group B.

Conclusions

Patients who underwent R&R procedures under general anesthesia with a muscle relaxant tended to be less corrected than those without muscle relaxant, especially in the early postoperative period and with a larger MR resection equal to or greater than 5 mm. However, there was no significant difference in the later postoperative period.  相似文献   
53.
Objective:The effectiveness of adjuvant treatments for resected gallbladder carcinoma (GBC) has remained unclear due to lack of randomized controlled trials; thus, the aim of present study was to evaluate the role of adjuvant treatments, including chemoradiotherapy (CRT) and/or chemotherapy (CTx), in patients with resected GBC.Methods:A total of 733 GBC patients who received curative-intent surgical resection were identified in a multi-institutional database. Of 733 patients, 372 (50.8%) did not receive adjuvant treatment, whereas 215 (29.3%) and 146 (19.9%) received adjuvant CTx and CRT, respectively. The locoregional recurrence-free survival (LRFS), recurrence-free survival (RFS), and overall survival (OS) of the adjuvant treatment groups were compared according to tumor stage (stage II vs. stage III–IV).Results:In stage II disease (n = 381), the 5-year LRFS, RFS, and OS were not significantly different among the no-adjuvant therapy, CTx, and CRT groups, and positive resection margin, presence of perineural invasion, and Nx classification were consistently associated with worse LRFS, RFS, and OS in the multivariate analysis (P < 0.05). For stage III–IV (n = 352), the CRT group had significantly higher 5-year LRFS, RFS, and OS than the no-adjuvant therapy and CTx groups (67.8%, 45.2%, and 56.9%; 37.9%, 28.8%, and 35.4%; and 45.0%, 30.0%, and 45.7%, respectively) (P < 0.05).Conclusions:CRT has value as adjuvant treatment for resected GBC with stage III–IV disease. Further study is needed for stage II disease with high-risk features.  相似文献   
54.
Bronchiolitis generally refers to inflammation and/or fibrosis of the non-cartilaginous small airways located approximately from the 8th airway generation down to the terminal and respiratory bronchioles. In contrast to young children, the frequency of small airway infection in adult bronchiolitis appears less frequent and a number of other pathophysiological conditions have been implicated in adult bronchiolitis. However, little information is available on the exact medical burden of bronchiolitis such as its prevalence and comorbidities in the adult population. The aim of this study is to elucidate the prevalence and comorbidities of bronchiolitis. We used the Korea National Health Insurance Service-National Sample Cohort, which provides data for 1,000,000 individuals out of the entire population by 2% stratified random sampling according to age, sex, residential area, and level of household income. We defined the cause of bronchiolitis other than acute infection as a patient with diagnostic code J448 or J684 and over 20 years of age who visited a clinic or hospital in South Korea. Then, 1:1 propensity score matching was performed to define a non-bronchiolitis (control) group to compare the comorbidities and mortality in the 2 groups. The overall prevalence of bronchiolitis was 688 cases/1,000,000 population during the study period (95% confidence interval, 625–751). The most common comorbid clinical condition in adults with bronchiolitis was rhinitis (52.3%), followed by bronchial asthma (52.23%), hypertension (43.69%), gastroesophageal reflux disease (30.56%), sinusitis (28.72%), diabetes (22.77%), and osteoporosis (17.85%). Other common bronchiolitis-associated comorbidities were cerebrovascular disease (16.86%), angina (14.37%), peripheral vascular disease (13.42%), congestive heart failure (11.9%), and malignancy in any organ (10.6%). Healthcare costs for bronchiolitis increased steeply during the same period. Malignancy in any organ was the leading cause of mortality in the patient group, followed by bronchiolitis itself. Further larger prospective multiethnic cohort studies should be carried out in the near future.  相似文献   
55.
BackgroundThe rapid urease test (RUT) is a major diagnostic tool for detecting Helicobacter pylori infection. This study aimed to establish an objective method for measuring the color changes in the RUT kit to improve the test’s diagnostic accuracy.MethodsA UV-visible spectrophotometer was selected as the colorimeter; experiments were conducted in three stages to objectively identify the color changes in the RUT kit.ResultsFirst, the urea broth solution showed an identifiable color change from yellow to red as the pH increased by 0.2. The largest transmittance difference detected using the UV-visible spectrophotometer was observed at a 590-nm wavelength. Second, the commercialized RUT kit also showed a gradual color change according to the pH change detected using the UV-visible spectrophotometer. Third, 13 cases of negative RUT results with a biopsy specimen and 16 of positive RUT results were collected. The transmittance detected using the UV-visible spectrophotometer showed a clear division between the positive and negative RUT groups; the largest difference was observed at a 559-nm wavelength. The lowest transmittance in the negative RUT group was 64, while the highest in the positive RUT group was 56, at the 559-nm wavelength. The UV-visible spectrophotometry reading showed a consistency of 92.7% compared with that of manual reading.ConclusionA transmittance of 60 at a 559-nm wavelength detected using UV-visible spectrophotometer can be used as a cutoff value for interpreting RUT results; this will help develop an automatic RUT kit reader with a high accuracy.  相似文献   
56.
Eucommia ulmoides Oliv. Bark (EUE) is commonly used for the treatment of hypertension, rheumatoid arthritis, lumbago, and ischialgia as well as to promote longevity. In this study, we tested the effects of EUE aqueous extract in graded doses to protect and enhance cognition in scopolamine-induced learning and memory impairments in mice. EUE significantly improved the impairment of short-term or working memory induced by scopolamine in the Y-maze and significantly reversed learning and memory deficits in mice as measured by the passive avoidance and Morris water maze tests. One day after the last trial session of the Morris water maze test (probe trial session), EUE dramatically increased the latency time in the target quadrant in a dose-dependent manner. Furthermore, EUE significantly inhibited acetylcholinesterase (AChE) and thiobarbituric acid reactive substance (TBARS) activities in the hippocampus and frontal cortex in a dose-dependent manner. EUE also markedly increased brain-derived neurotrophic factor (BDNF) and phosphorylation of cAMP element binding protein (CREB) in the hippocampus of scopolamine-induced mice. Based on these findings, we suggest that EUE may be useful for the treatment of cognitive deficits, and that the beneficial effects of EUE are mediated, in part, by cholinergic signaling enhancement and/or protection.  相似文献   
57.
It is unclear which factors contribute to the developing pressure pain hypersensitivity of the upper trapezius, a type of neurophysiological hyperexcitability. The present study investigated the relationship between physical and psychological factors and pressure pain hypersensitivity of the upper trapezius for each sex. In total, 154 individuals with neck/shoulder myofascial pain participated, among 372 food service workers. Participants completed a questionnaire (Beck Depression Inventory, and Borg Rating of Perceived Exertion scale) and were photographed to measure posture. Pressure pain sensitivity, 2 range of motions (cervical lateral bending and rotation), and 4 muscle strengths (serratus anterior, lower trapezius [LT], biceps, and glenohumeral external rotator) were measured by a pressure algometer, iPhone application, and handheld dynamometer, respectively. For each sex, forward multivariate logistic regression was used to test our a priori hypothesis among selected variables that a combination of psychosocial and physical factors contributed to the risk for pressure pain hypersensitivity. In multivariate analyses, LT strength (odds ratio = 0.94, 95% confidence interval = 0.91–0.97, P = .001) was the only significant influencing factor for pressure pain hypersensitivity in men. Dominant painful ipsilateral cervical rotation range of motion (odds ratio = 0.96, 95% confidence interval = 0.92–0.99, P = .037) was the only influencing factor for pressure pain hypersensitivity in women. LT strength and dominant painful ipsilateral cervical rotation range of motion could serve as guidelines for preventing and managing pressure pain hypersensitivity of the upper trapezius in food service workers with nonspecific neck/shoulder myofascial pain.  相似文献   
58.
The objective of this study was to estimate solid cancer risk attributable to long‐term, fractionated occupational exposure to low doses of ionizing radiation. Based on cancer incidence for the period 1950–1995 in a cohort of 27,011 Chinese medical diagnostic X‐ray workers and a comparison cohort of 25,782 Chinese physicians who did not use X‐ray equipment in their work, we used Poisson regression to fit excess relative risk (ERR) and excess absolute risk (EAR) dose–response models for incidence of all solid cancers combined. Radiation dose reconstruction was based on a previously published method that relied on simulating measurements for multiple X‐ray machines, workplaces and working conditions, information about protective measures, including use of lead aprons, and work histories. The resulting model was used to estimate calendar year‐specific badge dose calibrated as personal dose equivalent (Sv). To obtain calendar year‐specific colon doses (Gy), we applied a standard organ conversion factor. A total of 1,643 cases of solid cancer were identified in 1.45 million person‐years of follow‐up. In both ERR and EAR models, a statistically significant radiation dose–response relationship was observed for solid cancers as a group. Averaged over both sexes, and using colon dose as the dose metric, the estimated ERR/Gy was 0.87 (95% CI: 0.48, 1.45), and the EAR was 22 per 104PY‐Gy (95% CI: 14, 32) at age 50. We obtained estimates of the ERR and EAR of solid cancers per unit dose that are compatible with those derived from other populations chronically exposed to low dose‐rate occupational or environmental radiation.  相似文献   
59.
OBJECTIVE: It is unknown whether obese women would benefit from oral contraceptives or screening as endometrial cancer prevention strategies. We estimated the net health benefits and cost-effectiveness of these strategies in a hypothetical cohort of obese women. METHODS: A Markov decision-analytic model evaluated 4 strategies: 1) no prevention (reference strategy); 2) oral contraceptive pills (OCPs) for 5 years; 3) annual screening with endometrial biopsy from age 30; 4) biennial screening from age 30. Net health benefit was life expectancy and primary outcome was the incremental cost-effectiveness ratio. Baseline and transition probabilities were obtained from published literature and the Surveillance Epidemiology and End Results database, and costs were from the U.S. Department of Health and Human Services and Agency for Healthcare Research and Quality. Sensitivity analyses were performed for uncertainty around various measures. RESULTS: Average life expectancy for all strategies ranged from 74.52 to 74.60 years. None of the strategies had an incremental cost-effectiveness ratio less than $50,000 per year of life saved relative to the next best strategy. Endometrial cancer risk in obese women had to be 13 times greater than the general population risk before OCPs were a cost-effective intervention. CONCLUSION: Oral contraceptives and current screening methods are not cost-effective endometrial cancer prevention strategies for obese women. Risk factors such as morbid obesity and longstanding anovulation may define a subgroup at highest risk of endometrial cancer for whom OCPs may be a cost-effective strategy. Interventions that reduce endometrial cancer risk further or those with additional health benefits are needed in this population. LEVEL OF EVIDENCE: III.  相似文献   
60.
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