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   1967篇
  免费   121篇
  国内免费   11篇
耳鼻咽喉   9篇
儿科学   64篇
妇产科学   54篇
基础医学   248篇
口腔科学   42篇
临床医学   168篇
内科学   408篇
皮肤病学   31篇
神经病学   118篇
特种医学   68篇
外科学   343篇
综合类   40篇
预防医学   139篇
眼科学   68篇
药学   166篇
中国医学   3篇
肿瘤学   130篇
  2023年   10篇
  2022年   40篇
  2021年   72篇
  2020年   36篇
  2019年   59篇
  2018年   64篇
  2017年   42篇
  2016年   65篇
  2015年   40篇
  2014年   74篇
  2013年   99篇
  2012年   143篇
  2011年   141篇
  2010年   100篇
  2009年   95篇
  2008年   107篇
  2007年   102篇
  2006年   89篇
  2005年   82篇
  2004年   80篇
  2003年   70篇
  2002年   66篇
  2001年   27篇
  2000年   20篇
  1999年   12篇
  1998年   14篇
  1997年   11篇
  1996年   13篇
  1995年   15篇
  1994年   11篇
  1993年   12篇
  1992年   11篇
  1991年   15篇
  1990年   18篇
  1989年   19篇
  1988年   16篇
  1987年   15篇
  1986年   14篇
  1985年   15篇
  1984年   8篇
  1983年   15篇
  1981年   9篇
  1980年   12篇
  1979年   15篇
  1978年   13篇
  1974年   11篇
  1973年   12篇
  1972年   10篇
  1971年   8篇
  1970年   9篇
排序方式: 共有2099条查询结果,搜索用时 296 毫秒
91.
92.
Five new isostructural lanthanide–organic complexes, [Ln2O2(OH)(HQXD)(H2QXD)2]·H2O (Ln = Eu 1, Tb 2, Sm 3 Dy 4 and Gd 5; H2QXD = quinoxaline-2,3(1H,4H)-dione), have been synthesized under hydrothermal conditions. These complexes are characterized by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric-differential thermal analysis (TG-DTA) and photo-luminescent spectroscopy. Single crystal X-ray diffraction analysis of complex 1 revealed that the structure featured in 1D chiral “Eu2O3” chains surrounded by coordinating organic ligands. These chains are interconnected via hydrogen bonding and offset π⋯π stacking interactions of the ligands to form the 3D supramolecular frameworks. The photo-luminescence studies for complexes 1–5 disclosed that the ligand (H2QXD) showed an antenna effect to transfer energy toward the lanthanide cations. The energy transfer mechanism investigations show that the energy transition from the triplet energy level (3ππ*) of ligand H2QXD to the Tb3+ cation is more effective than to the Eu3+, Sm3+ and Dy3+ ions; therefore it has been selected as a representative to examine the potential for sensing small molecules. Complex 2′, which was obtained by the heating treatment of 2 at 150 °C, displayed a high luminescence sensitivity towards small solvent molecules. Tertiary butanol (t-butanol) was found to be an excellent sensitizer, while tetrahydrofuran (THF) was a highly quenching species. Complex 2′ could regain a higher photo-luminescence intensity after treating for 5 cycles with t-butanol, revealing a prospect for reusability.

A series of isostructural lanthanide–quinoxaline-2,3(1H,4H)-dione containing 1D chiral chains shows high sensing effect toward the small solvent molecules, in which tertiary butanol was an excellent sensitizer, while tetrahydrofuran was a highly quenching species.  相似文献   
93.
IntroductionRT‐PCR is widely used as a diagnostic test for the detection of SARS‐CoV‐2. In this study, we aim to describe the clinical utility of serial PCR testing in the final detection of COVID‐19.MethodWe collected multiple nasopharyngeal swab samples from patients who had negative RT‐PCR test on the first day after hospitalization. RT‐PCR tests were performed on the second day for all patients with initial negative result. For the patients with secondary negative results on day 2, tertiary RT‐PCR tests were performed on day 3 after hospitalization.ResultAmong 68 patients with initial negative test results, at the end of follow‐up, the mortality number was 20 (29.4%). About 33.8% of patients had subsequent positive PCR test results for the second time and 17.4% of the patients who performed third PCR test had positive result.ConclusionBased on this study, serial RT‐PCR testing is unlikely to yield additional information.  相似文献   
94.
Saffron (Crocus sativus L.) is a medicinal plant, originally cultivated in the East and Middle East, and later in some Mediterranean countries. Saffron is obtained from the stigmas of the plant. Currently, the use of saffron is undergoing a revival. The medicinal virtues of saffron, its culinary use and its high added value have led to the clarification of its phytochemical profile and its biological and therapeutic characteristics. Saffron is rich in carotenoids and terpenes. The major products of saffron are crocins and crocetin (carotenoids) deriving from zeaxanthin, pirocrocin and safranal, which give it its taste and aroma, respectively. Saffron and its major compounds have powerful antioxidant and anti-inflammatory properties in vitro and in vivo. Anti-tumor properties have also been described. The goal of this review is to present the beneficial effects of saffron and its main constituent molecules on neuropsychiatric diseases (depression, anxiety and schizophrenia) as well as on the most frequent age-related diseases (cardiovascular, ocular and neurodegenerative diseases, as well as sarcopenia). Overall, the phytochemical profile of saffron confers many beneficial virtues on human health and, in particular, on the prevention of age-related diseases, which is a major asset reinforcing the interest for this medicinal plant.  相似文献   
95.
96.
Congenital spondyloytic spondylolisthesis (CSS) is characterized as a pars-interarticularis well-corticated cleft with antherolithesis. The presence of spina bifida and vertebral dysplastic changes corroborate the possibility of a congenital etiology. It is a rare condition, usually discovered incidentally, especially after a trauma and should be differentiated from traumatic spondylolysis, which requires aggressive treatments. The management is often conservative, with surgery being indicated for symptomatic or unstable lesions. We report the case of a sixth cervical vertebra Congenital Spondylolytic Spondylolisthesis (CCS), discovered fortuitously following a minor trauma, in a 19-year-old male patient, treated conservatively with a favorable evolution.  相似文献   
97.
Objective: To further investigate the underlying pathology of axial and appendicular skeletal abnormalities such as painful spine stiffness, gait abnormalities, early onset osteoarthritis and patellar instability in patients with Stickler syndrome type I. Radiographic and tomographic analyses were organized.Methods: From a series of Stickler syndrome patients followed from early life to late childhood. Ten patients (6 boys and four girls of different ethnic origins were consistent with the diagnosis of Stickler syndrome type I ). Phenotypic characterization was the baseline tool applied for all patients and genotypic correlation was performed on four familiesResults: A constellation of axial abnormalities namely; anterolateral ossification of the anterior longitudinal spinal ligament with subsequent fusion of two cervical vertebrae, early onset Forestier disease (progressive spinal hyperostosis with subsequent vertebral fusion on top of bridging osteophytes and “Bamboo-like spine” resembling ankylosing spondylitis) and severe premature spine degeneration were evident. Appendicular abnormalities in connection with generalized epiphyseal dysplasia were the underlying aetiology in patients with Intoeing gait and femoral anteversion, early onset severe osteoarthritis of the weight bearing joint. Remarkable trochleo-patellar dysplasia secondary to severe osteoarthritis causing effectively the development of patellar instability was additional pathology. Mutation of COL2A1 has been confirmed as the causative gene for Stickler syndrome type IConclusion: We concluded that conventional radiographs and the molecular determination of a COL2A1 in patients with (Stickler syndrome type I) are insufficient tools to explain the reasons behind the tremendous magnitude of axial and appendicular skeletal abnormalities. We were able to modify the criteria of the clinical phenotype as designated by Rose et al in accordance with the novel axial and appendicular criteria as emerged from within our current study.  相似文献   
98.
OBJECTIVEWe determined the efficacy of self-administered subcutaneous mini-dose glucagon (MDG) to treat fasting-induced hypoglycemia in type 1 diabetes (T1D).RESEARCH DESIGN AND METHODSThis was a 4-week randomized, controlled crossover trial of 2-week MDG or 2-week oral glucose tablets (OG, control) involving 17 adults with T1D during Ramadan.RESULTSCompared with OG, MDG demonstrated a significant higher change in blood glucose from baseline to 30 min (Δt30, P < 0.001) and 1 h (Δt60, P = 0.02). The efficacy of MDG was preserved following ≥8 h fasting with significantly higher Δt30 in MDG (P = 0.01). Over the entire 2 weeks, MDG period had increased time in 70–180 mg/dL (P = 0.009) and less time <70 mg/dL (P = 0.04). MDG use resulted in higher completion of fasts compared with OG (P < 0.001).CONCLUSIONSMDG administration is an effective alternative to OG for prevention and treatment of fasting-induced hypoglycemia, offering improved glycemic control and promoting successful completion of prolonged fasts.  相似文献   
99.
100.
Artificial intelligence (AI)–synthesized text, audio, image, and video are being weaponized for the purposes of nonconsensual intimate imagery, financial fraud, and disinformation campaigns. Our evaluation of the photorealism of AI-synthesized faces indicates that synthesis engines have passed through the uncanny valley and are capable of creating faces that are indistinguishable—and more trustworthy—than real faces.  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