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   3501篇
  免费   225篇
  国内免费   22篇
耳鼻咽喉   31篇
儿科学   88篇
妇产科学   56篇
基础医学   343篇
口腔科学   56篇
临床医学   311篇
内科学   767篇
皮肤病学   47篇
神经病学   219篇
特种医学   50篇
外科学   564篇
综合类   101篇
一般理论   2篇
预防医学   280篇
眼科学   106篇
药学   408篇
中国医学   66篇
肿瘤学   253篇
  2023年   32篇
  2022年   129篇
  2021年   153篇
  2020年   80篇
  2019年   104篇
  2018年   115篇
  2017年   70篇
  2016年   93篇
  2015年   105篇
  2014年   134篇
  2013年   177篇
  2012年   273篇
  2011年   279篇
  2010年   133篇
  2009年   114篇
  2008年   225篇
  2007年   194篇
  2006年   177篇
  2005年   188篇
  2004年   165篇
  2003年   144篇
  2002年   124篇
  2001年   62篇
  2000年   65篇
  1999年   53篇
  1998年   37篇
  1997年   20篇
  1996年   18篇
  1995年   16篇
  1994年   16篇
  1993年   11篇
  1992年   24篇
  1991年   27篇
  1990年   15篇
  1989年   21篇
  1988年   15篇
  1987年   13篇
  1986年   17篇
  1985年   15篇
  1984年   12篇
  1983年   8篇
  1982年   5篇
  1980年   8篇
  1979年   7篇
  1978年   8篇
  1977年   5篇
  1976年   5篇
  1974年   6篇
  1973年   5篇
  1966年   6篇
排序方式: 共有3748条查询结果,搜索用时 15 毫秒
81.
Complete dislocation of the ulnar 4 carpometacarpal joints of the hand (excluding the thumb) is an uncommon injury. Anatomic reduction of the carpometacarpal joint (CMCJ) is essential to maintain function of the hand, and this can often be accomplished by prompt closed reduction and percutaneous Kirschner-wire fixation. The diagnosis is sometimes delayed or missed in the emergency department (ED), and a true lateral radiograph is mandatory in suspected cases. We present a case of dorsal unilateral dislocation of the ulnar 4 CMCJs without associated fracture. The injury was difficult to diagnose because of gross swelling of the hand. We describe a simple clinical test (Indian salutation test) that we found to be very helpful in raising the index of suspicion and hence increasing the likelihood of avoiding any clinical and medicolegal difficulties in such cases. A true lateral radiograph of the wrist confirmed the diagnosis, and prompt closed reduction and percutaneous Kirschner-wire fixation resulted in a good outcome in the case described here.  相似文献   
82.

Objective

To evaluate the efficacy of single oral mega-dose of Vitamin D3 for treatment and prevention of pneumonia in underfive children.

Design

Randomized, double blind, placebo-controlled trial.

Setting

Tertiary-care hospital.

Participants

324 children (of 980 assessed) between 6 mo-5 y age (median (IQR): 12 (7,19.8) mo) with WHO-defined severe pneumonia. Of these, 126 (39%) were vitamin D deficient (serum 25(OH)D <12 ng/mL).

Intervention

100,000 IU of oral cholecalciferol (n= 162) or placebo (n= 162) in single dose, administered at enrolment.

Outcome variables

Primary: Time to resolution of severe pneumonia and proportion of children having recurrence of pneumonia in next 6 months; Secondary: Change in serum levels of 25(OH)D; immunoglobulins IgA, IgG, IgM, and cathelicidin 2 weeks following supplementation; and time taken for overall resolution of illness.

Results

Median (95% CI) time for resolution of severe pneumonia was 30 (29, 31) h in the vitamin D group as compared to 31 (29,33) h in the placebo group [adjusted hazard ratio (95% CI): 1·39 (1·11, 1·76); P=0·005]. The risk of recurrence of pneumonia in next 6 months was comparable in the two groups [placebo: 36/158 (22·8%); vitamin D: 39/156 (25%); RR (95% CI): 1·13 (0·67,1·90); P=0·69]. Proportion of vitamin D deficient children declined from 38% to 4% in the supplementation group, and from 41% to 33% in the placebo group, two weeks after supplementation. There was no significant effect of vitamin D supplementation on serum levels of cathelicidin, IgA and IgG. The time taken for complete recovery from pneumonia, duration of hospitalization, and fever clearance time were comparable for the two groups. No adverse event was noted related to the intervention.

Conclusion

There is no robust evidence of a definite biological benefit, either for therapy or prevention, to suggest a routine megadose supplement of vitamin D3 for under-five children with severe pneumonia.
  相似文献   
83.
84.
Resveratrol (RL), a natural polyphenol, is known for its diverse biological effects against various human cancer cell lines. But low aqueous solubility, poor bioavailability, and stability limit its efficacy against prostate cancer. In this study polymeric nanoparticles encapsulating resveratrol (RLPLGA) were designed and their cytotoxic and mode of apoptotic cells death against prostate cancer cell line (LNCaP) was determined. Nanoparticles were prepared by solvent displacement method and characterized for particle size, TEM, entrapment efficiency, DSC and drug release study. RLPLGA exhibited a significant decrease in cell viability with 50% and 90% inhibitory concentration (IC50 and IC90) of 15.6?±?1.49 and 41.1?±?2.19?μM respectively against the LNCaP cells. This effect was mediated by apoptosis as confirmed by cell cycle arrest at G1-S transition phase, externalization of phosphatidylserine, DNA nicking, loss of mitochondrial membrane potential and reactive oxygen species generation in LNCaP cells. Furthermore, significantly greater cytotoxicity to LNCaP cells was observed with nanoparticles as compared to that of free RL at all tested concentrations. RLPLGA nanoparticles presented no adverse cytotoxic effects on murine macrophages even at 200?μM. Our findings support the potential use of developed resveratrol loaded nanoparticle for the prostate cancer chemoprevention/ chemotherapy with no adverse effect on normal cells.  相似文献   
85.
Hepatic lipid infiltration (steatosis) is a complication of the metabolic syndrome and can progress to nonalcoholic steatohepatitis and severe liver injury. Microsomal cytochrome P450 (P450) drug oxidases are down-regulated in experimental steatosis. In this study we evaluated the separate and combined effects of lipid accumulation and P450 down-regulation on the microsomal oxidation of the antipsychotic agent clozapine (CLZ), the use of which is associated with an increased incidence of the metabolic syndrome. Several important drug oxidizing P450s were down-regulated, and the formation of N-desmethyl-CLZ (norCLZ) and CLZ N-oxide was decreased in microsomal fractions from orotic acid-induced early steatotic rat liver. Inclusion of lipids extracted from steatotic, but not control, liver decreased the free concentration of CLZ in microsomes and suppressed norCLZ formation; CLZ N-oxidation was unchanged. Triglycerides increased in steatotic liver to 15-fold of control, whereas increases in the monounsaturated oleic acid to 10-fold of control and total polyunsaturated and saturated fatty acids to 4- and 5-fold of control also occurred. Addition of triglycerides containing esterified omega-6 and omega-3 fatty acids inhibited the microsomal formation of norCLZ but not that of CLZ N-oxide; triglycerides esterified with unsaturated and monounsaturated fatty acids were inactive. Thus, drug oxidation may be suppressed in steatosis by P450 down-regulation and the accumulation of polyunsaturated fatty esters. In contrast, the activity of the flavin-containing monooxygenase that mediates CLZ N-oxidation was unimpaired. Lipid deposition in livers of patients with the metabolic syndrome may necessitate dosage adjustments for toxic drugs, including CLZ.  相似文献   
86.
Introduction: Alzheimer’s disease (AD), which accounts for three fourth of all cases of dementia, is a major public health problem in modern society and, yet, there is no effective treatment available that can prevent or inhibit this chronic progressive neurodegenerative disease. A major current drug target is intraneuronal abnormally hyperphosphorylated microtubule-associated protein tau which is a histopathological hallmark of this disease and of a family of neurodegenerative diseases called tauopathies.

Areas covered: In this review, the authors discuss a growing number of studies that describe the nature and mechanism of tau pathology and various drug discovery options and most recent developments in tau-based therapeutics. PubMed was used to obtain relevant literature while clinicaltrials.gov site and Google search were employed to obtain the latest information on tau based AD clinical trials.

Expert opinion: In authors’ opinion, loss of neuronal connectivity leads to the hyperphosphorylation of tau and is thus a key therapeutic target. Rescue of neuronal connectivity loss and hyperphosphorylation of tau are most promising approaches. Consequently, tau immunotherapy has a high therapeutic potential.  相似文献   

87.
Bray  J. O.  Sutton  T. L.  Akhter  M. S.  Iqbal  E.  Orenstein  S. B.  Nikolian  V. C. 《Hernia》2022,26(6):1687-1694
Hernia - Telemedicine has emerged as a viable option to in-person visits for the evaluation and management of surgical patients. Increased integration of telemedicine has allowed for greater access...  相似文献   
88.
Origanum species are mostly distributed around the Mediterranean, Euro‐Siberian, and Iran‐Siberian regions. Since time immemorial, the genus has popularly been used in Southern Europe, as well as on the American continent as a spice now known all over the world under the name “oregano” or “pizza‐spice.” Origanum plants are also employed to prepare bitter tinctures, wines, vermouths, beer, and kvass. The major components of Origanum essential oil are various terpenes, phenols, phenolic acids, and flavonoids with predominant occurrence of carvacrol and thymol (with reasonable amounts of p‐cymen and ‐terpinene) or of terpinene‐4‐ol, linalool, and sabinene hydrate. Many species of Origanum genus are used to treat kidney, digestive, nervous, and respiratory disorders, spasms, sore throat, diabetes, lean menstruation, hypertension, cold, insomnia, toothache, headache, epilepsy, urinary tract infections, etc. Origanum essential oil showed potent bioactivities owing to its major constituents' carvacrol, thymol, and monoterpenes. Several preclinical studies evidenced its pharmacological potential as antiproliferative or anticancer, antidiabetic, antihyperlipidemic, anti‐obesity, renoprotective, antiinflammatory, vasoprotective, cardioprotective, antinociceptive, insecticidal, and hepatoprotective properties. Its nanotechnological applications as a promising pharmaceutical in order to enhance the solubility, physicochemical stability, and the accumulation rate of its essential oils have been investigated. However, Origanum has been reported causing angioedema, perioral dermatitis, allergic reaction, inhibition of platelet aggregation, hypoglycemia, and abortion. Conclusive evidences are still required for its clinical applications against human medical conditions. Toxicity analyses and risk assessment will aid to its safe and efficacious application. In addition, elaborate structure–activity studies are needed to explore the potential use of Origanum‐derived phytochemicals as promising drug candidates.  相似文献   
89.
Today, research in biomedicine often requires the knowledge and technologies in diverse fields. Therefore, there is an increasing need for collaborative team science that crosses traditional disciplines. Here, we discuss our own lessons from both interdisciplinary and transdisciplinary teams, which ultimately ushered us to expand our research realm beyond bone biology.  相似文献   
90.
Two ternary copper(II) complexes of dl-threonine and polypyridyl ligands with formula of [Cu(Thr)(Byp)Cl]·H2O (1) and [Cu(Thr)(Phen)H2O]Cl·2H2O (2) were synthesized. The complexes were characterized by spectral (NMR, FT-IR, and UV–Vis), CHN elemental analysis and have been structurally elucidated by X-ray crystallography. Both of the complexes formed slightly distorted square-pyramidal coordination geometry. The electronic absorption spectra of the complexes showed a very low intensity dd electronic band in the range of 610–620 nm in Tris–HCl/NaCl (5:5 mM) pH 7.2 buffer solution. The DNA binding interaction with calf-thymus DNA (CT-DNA) was investigated by electronic absorption spectral titration and viscosity measurements. The results revealed that the phenanthroline complex (2) interact with CT-DNA through intercalation while bipyridyl complex (1) through the groove binding mode. The calculated intrinsic binding constant (K b) of (1) and (2) were 0.5 and 4.4 × 105 M?1, respectively. Both the complexes were found to promote efficient DNA cleavage activities at low concentration in the presence of H2O2. The results showed that (2) has the highest DNA binding and nuclease activity. Furthermore, both the complexes were tested against human colon cancer (HCT 116) and breast cancer (MCF-7) cell lines and showed a dose-dependent antiproliferation effect.  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