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   1647篇
  免费   136篇
  国内免费   7篇
耳鼻咽喉   31篇
儿科学   31篇
妇产科学   54篇
基础医学   161篇
口腔科学   25篇
临床医学   126篇
内科学   392篇
皮肤病学   90篇
神经病学   144篇
特种医学   47篇
外科学   310篇
综合类   32篇
一般理论   1篇
预防医学   79篇
眼科学   16篇
药学   145篇
中国医学   12篇
肿瘤学   94篇
  2023年   10篇
  2022年   22篇
  2021年   36篇
  2020年   26篇
  2019年   55篇
  2018年   70篇
  2017年   58篇
  2016年   56篇
  2015年   52篇
  2014年   75篇
  2013年   86篇
  2012年   139篇
  2011年   122篇
  2010年   70篇
  2009年   48篇
  2008年   103篇
  2007年   88篇
  2006年   104篇
  2005年   89篇
  2004年   62篇
  2003年   89篇
  2002年   57篇
  2001年   32篇
  2000年   18篇
  1999年   10篇
  1998年   10篇
  1994年   5篇
  1992年   19篇
  1991年   16篇
  1990年   9篇
  1989年   7篇
  1988年   8篇
  1987年   8篇
  1986年   8篇
  1985年   13篇
  1984年   9篇
  1983年   7篇
  1982年   8篇
  1981年   4篇
  1980年   4篇
  1979年   9篇
  1978年   4篇
  1977年   8篇
  1975年   6篇
  1973年   4篇
  1972年   4篇
  1971年   7篇
  1970年   4篇
  1969年   4篇
  1968年   6篇
排序方式: 共有1790条查询结果,搜索用时 352 毫秒
21.
We compared sedation levels in children following administration of intranasal dexmedetomidine. One hundred and sixteen children aged between 1 and 8 years were enrolled in this prospective, randomised trial. Children were assigned to receive either intranasal dexmedetomidine 1 μg.kg?1 (Group 1) or 2 μg.kg?1 (Group 2). Thirty‐one (53%) patients from Group 1 and 38 (66%) patients from Group 2 were satisfactorily sedated at the time of anaesthetic induction. Logistic regression showed a significant interaction effect (p = 0.049), with the odds ratio between Group 2 over Group 1 estimated as 1.1 (95% CI 0.5–2.7) for the 1–4 year age group, and 10.5 (95% CI 1.4–80.2) for the 5–8 year age group. Both doses produced a similar level of satisfactory sedation in children aged 1–4 years, whereas 2 μg.kg?1 resulted in a higher proportion of satisfactory sedation in children aged 5–8 years. There were no adverse haemodynamic effects. We conclude that intranasal dexmedetomidine in a premedication dose of 2 μg.kg?1 resulted in excellent sedation in children.  相似文献   
22.
Toll-like receptors (TLRs) are part of the innate immune system, and they belong to the pattern recognition receptors (PRR) family. The PRR family is designed to recognize and bind conserved pathogen-associated molecular patterns, which are not generated by the host and are restricted and essential to microorganisms. TLR9, which recognizes unmethylated CpG (cytosine guanosine dinucleotide), is a very promising target for therapeutic activation. Stimulation of TLR9 activates human plasmacytoid dendritic cells and B cells, and results in potent T helper-1 (Th1)-type immune responses and antitumor responses in mouse tumor models and in patients. Several pharmaceutical companies, such as Pfizer, Idera, and Dynavax, are developing CpG oligodeoxynucleotides (ODNs) for the treatment of cancer, along with other conditions, such as infections and allergy. CpG ODNs have shown promising results as vaccine adjuvants and in combination with cancer immunotherapy. Several TLR9 agonists are being developed and have entered clinical trials to evaluate their safety and efficacy for the treatment of several hematopoietic and solid tumors. In this review, we discuss the use of CpG ODNs in several phase I and II clinical trials for the treatment of NHL, renal cell carcinoma, melanoma, and non-small cell lung cancer, either alone or in combination with other agents.  相似文献   
23.
The influence of coenzyme Q10 (CoQ10) in cold stress test (-15 degrees C for 4 hours) cardiac functional impairment was studied in isolated isovolumic heart of control rats (C; n=12) and of placebo (P; n=11) and treated rats (CoQ10; n=10). In addition, electron microscopic evaluation of left ventricular (LV) slices (n=3 in each group) allowed us to analyze the myocardial ultrastructure. Maximal values of developed pressure (DPmax) were similarly decreased in cold stressed animals (C=129+/-3.9 mmHg; P=106+/-6.7 mmHg; CoQ10=91+/-3.9 mmHg); however, volume-induced enhancement of pressure generation (slope of DP volume relations: C=0.248+/-0.0203 mmHg / microl; P=0.2831+/-0.0187 mmHg / microl; CoQ10=0.2387 ( 0.0225 mmHg / microl; p > 0.05), and the duration of systole (C=80+/-1.6 ms; P=78+/-1.3 ms; CoQ10=80+/-2.7 ms) were not altered. Myocardial relaxation, evaluated by the relaxation constant (C=39+/-1.9 ms; P=42+/-3.4 ms; CoQ10=51+/-6.0 ms), as well as resting stress / strain relations were unaffected by cold stress. Myocardial samples showed that pretreatment with CoQ10 attenuates myofibrillar and mitochondrial lesions, and prevents mitochondrial fractional area increase (P: 53.11%>CoQ10: 38.78%=C: 33.87%; p< 0.005) indicating that the exogenous administration of CoQ10 can reduce cold stress myocardial injury.  相似文献   
24.
H. Sheng  K. Ishii  U. Förstermann  F. Murad 《Lung》1995,173(6):373-383
Bradykinin (10–8-10–5M) caused a concentration-dependent increase in cyclic GMP (cGMP) production in bovine tracheal smooth muscle in the absence of epithelium. The effect was calcium-dependent and was inhibited by pyrogallol (10 M) and methylene blue (10 M). The inhibition of pyrogallol was reversed by superoxide dismutase (100 Usnowml). Nitric oxide (NO) synthase inhibitors, N G-methyl-l-arginine (10–100 M) and N G-nitro-l-arginine (10–100 M) reduced cGMP accumulation induced by bradykinin in a concentration-dependent fashion, and the inhibition was reversed by l-arginine. Immunohistochemistry with a specific antibody against neuronal NO synthase from rat cerebellum showed positive staining localized in some nerve fibers. Bradykinin-induced cGMP accumulation appears to be related to the release of NO, part of which is probably synthesized in nonadrenergic noncholinergic nerve in bovine trachea.Offprint requests to: Dr. Hong Sheng  相似文献   
25.
Objective: To evaluate the utility of cervical elastosonography (ES) in prediction of cervical insufficiency (CI).

Methods: A total of 40 women, of which 20 who had previously received the diagnosis of CI and 20 healty women were included in the study. None of the women were pregnant. All subjects underwent sonographic evaluation including cervical length measurement and ES of uterine cervix. Adjacent muscular tissue was the reference point for elastosonography evaluation. Tissue strain ratio values were obtained from all the patients.

Results: The area around the internal cervical os of the group with CI was found to be significantly softer as compared to the control group (higher SR rate, p?<?0.05). Furthermore, the outer parts of the cervix (sites A and D) were also found harder in the group that had CI (lower SR rate, p?<?0.05).

Conclusions: According to our knowledge, this is preliminary study to evaluate the predictive value of cervical ES in CI and we concluded that ES can be used as reliable method to determine CI but it is necessary to be studied in different cohort groups.  相似文献   

26.
27.
Objectives. We aimed to highlight sociodemographic differences in how patients access colonoscopy.Methods. We invited all eligible patients (n = 2500) from 2 academy-affiliated colonoscopy centers in Alachua County, Florida (1 free standing, 1 hospital based), to participate in a precolonoscopy survey (September 2011–October 2013); patients agreeing to participate (n = 1841, response rate = 73.6%) received a $5.00 gift card.Results. We found sociodemographic differences in referral pathway, costs, and reasons associated with obtaining the procedure. Patients with the ideal pathway (referred by their regular doctor for age-appropriate screening) were more likely to be Black (compared with other minorities), male, high income, employed, and older. Having the colonoscopy because of symptoms was associated with being female, younger, and having lower income. We found significant differences for 1 previously underestimated barrier, having a spouse to accompany the patient to the procedure.Conclusions. Patients’ facilitators and barriers to colonoscopy differed by sociodemographics in our study, which implies that interventions based on a single facilitator will not be effective for all subgroups of a population.Colorectal cancer (CRC), the second leading cause of US cancer deaths in 2013 (50 830),1 is not distributed equally. Nationally, it is estimated that incidence is 25% higher, and mortality from CRC 50% higher, in Black Americans than in Whites.2,3 Most CRC diagnoses follow evaluation by colonoscopy. Although consumers have a range of CRC screening tests, from least invasive (fecal occult blood test, fecal immunochemical test) to most invasive (sigmoidoscopy, colonoscopy),4 if polyps are indicated, a colonoscopy is required as follow-up. Thus, colonoscopy is both an entry point and a pivotal event in the process of preventing, detecting, and treating CRC. CRC can be prevented through the removal of precancerous polyps or detected at an early, easily treatable stage5; findings indicate6 that colonoscopy with polypectomy reduces mortality from CRC by 53%. Although rates of CRC screening have increased,3 there is need for improvement. More than one third of Americans are not in compliance with screening guidelines,7 with rates being lower in the southern United States.8In 2008, Etzioni et al.9 presented a model of patient and provider-level factors that influence decision-making in colon cancer and that can lead to health disparities in disease recurrence and survival. The Etzioni model identifies key points of vulnerability in the treatment process where the potential to achieve high-quality, guideline-recommended care can be lost. The model captures patients after surgery, beginning with the decision to refer patients to a medical oncologist for adjuvant treatment; it is relevant because there is considerable evidence of inequities in who receives adjuvant treatment based on older age,10,11 comorbidities,12,13 low income,7 coverage with Medicaid rather than Medicare,13 Black race,14 female gender,15,16 and being unmarried.9We propose that this model starts too late in the process; health disparities originate prior to colonoscopy and can increase at each decision point along a continuum. In an elaborated model (Figure 1), we suggest that CRC health disparities research should begin with an investigation of entry into the health care system and the subsequent pathways to colonoscopy. Referral patterns, costs, and patient demographics influence patient access to care, colonoscopy compliance, and postcolonoscopy decision-making.Open in a separate windowFIGURE 1—Pathways to colonoscopy, treatment, and outcomes.  相似文献   
28.
29.
Clinical Rheumatology - Adherence to prescribed medication regimens is fundamental to the improvement and maintenance of the health of patients with rheumatoid arthritis. It is therefore important...  相似文献   
30.

Background

Decision makers rely on meta-analytic estimates to trade off benefits and harms. Publication bias impairs the validity and generalizability of such estimates. The performance of various statistical tests for publication bias has been largely compared using simulation studies and has not been systematically evaluated in empirical data.

Methods

This study compares seven commonly used publication bias tests (i.e., Begg’s rank test, trim-and-fill, Egger’s, Tang’s, Macaskill’s, Deeks’, and Peters’ regression tests) based on 28,655 meta-analyses available in the Cochrane Library.

Results

Egger’s regression test detected publication bias more frequently than other tests (15.7% in meta-analyses of binary outcomes and 13.5% in meta-analyses of non-binary outcomes). The proportion of statistically significant publication bias tests was greater for larger meta-analyses, especially for Begg’s rank test and the trim-and-fill method. The agreement among Tang’s, Macaskill’s, Deeks’, and Peters’ regression tests for binary outcomes was moderately strong (most κ’s were around 0.6). Tang’s and Deeks’ tests had fairly similar performance (κ?>?0.9). The agreement among Begg’s rank test, the trim-and-fill method, and Egger’s regression test was weak or moderate (κ <?0.5).

Conclusions

Given the relatively low agreement between many publication bias tests, meta-analysts should not rely on a single test and may apply multiple tests with various assumptions. Non-statistical approaches to evaluating publication bias (e.g., searching clinical trials registries, records of drug approving agencies, and scientific conference proceedings) remain essential.
  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