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   10880篇
  免费   607篇
  国内免费   23篇
耳鼻咽喉   82篇
儿科学   332篇
妇产科学   298篇
基础医学   1917篇
口腔科学   220篇
临床医学   1021篇
内科学   1934篇
皮肤病学   226篇
神经病学   1120篇
特种医学   478篇
外科学   1285篇
综合类   91篇
一般理论   3篇
预防医学   927篇
眼科学   142篇
药学   726篇
中国医学   30篇
肿瘤学   678篇
  2022年   57篇
  2021年   145篇
  2020年   95篇
  2019年   131篇
  2018年   163篇
  2017年   128篇
  2016年   163篇
  2015年   224篇
  2014年   272篇
  2013年   394篇
  2012年   661篇
  2011年   696篇
  2010年   402篇
  2009年   366篇
  2008年   627篇
  2007年   649篇
  2006年   634篇
  2005年   651篇
  2004年   608篇
  2003年   542篇
  2002年   552篇
  2001年   116篇
  2000年   90篇
  1999年   114篇
  1998年   136篇
  1997年   96篇
  1996年   89篇
  1995年   93篇
  1994年   74篇
  1993年   70篇
  1992年   64篇
  1991年   78篇
  1990年   55篇
  1989年   59篇
  1988年   59篇
  1985年   59篇
  1984年   55篇
  1983年   49篇
  1982年   51篇
  1974年   51篇
  1933年   71篇
  1932年   59篇
  1931年   57篇
  1930年   52篇
  1929年   44篇
  1928年   45篇
  1927年   52篇
  1926年   54篇
  1925年   49篇
  1924年   52篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
With the advent of the digital information age, schools of nursing are developing and using web-based programs, courses, and course materials to meet students' needs for access and high-quality learning experiences. In an attempt to maximize scant resources, including faculty, many schools are seeking grant funding, joining consortia, or forming partnerships that require sharing of web-based course materials. Entering such collaborative arrangements usually requires licensing agreements to transfer intellectual capital. This article explains licensing and the related concepts of intellectual property, copyright, and technology transfer. It also identifies the advantages and disadvantages of licensing and describes a licensing process.  相似文献   
992.
Restraint is a construct of potential use forunderstanding addictive behaviors. In terms of alcoholand other drug use, restrained individuals arecognitively and behaviorally preoccupied withcontrolling their substance use. Previous work in thecontext of alcohol consumption suggests that whenregulation fails, alcohol and other drug users are morelikely to engage in excessive substance use. Thisproposition was evaluated in a clinical population ofalcohol and other substance users admitted to aninpatient treatment program. A confirmatory factoranalysis of alcoholics' responses to the Temptation andRestraint Inventory, a measure of drinking restraint,replicated the two second-order factors previouslyreported for social drinkers: Cognitive and EmotionalPreoccupation (CEP) and Cognitive and Behavioral Control (CBC). CEP scores were a negative predictor ofpretreatment percentage of days abstinent and a positivepredictor of percentage of drinking days engaged inheavy drinking, drinks per drinking day, and drinking consequences. CBC scores were a negativepredictor onlyof drinks per drinking day. An analysis ofdrug users' responses to a drug version of theTemptation and Restraint Inventory also replicated thepreviously found CEP and CBC factors. Scores on the CEPfactor were a positive predictor and scores on the CBCfactor a negative predictor of drug use frequency. CEPscores also were a positive predictor of drug use consequences. The data taken together representa potentially useful extension of the restraintconstruct to alcoholics and other drug users and supporta multifactorial characterization of substance use restraint as reflecting a reciprocalrelationship between restricted and excessive substanceuse.  相似文献   
993.
Clinical chemical reference values for older persons are sparse and mostly intermixed with those for younger persons. We had a unique opportunity to obtain blood samples from volunteers who were 75 years old and living in two districts of Vienna, Austria. Consequently, we utilized stored plasma samples to obtain reference intervals for 120 apparently healthy 75-year-old participants for pro-brain natriuretic peptide (proBNP), as well as for troponin T. The N-terminal (NT)-proBNP protein assay is currently used as a diagnostic and prognostic aid in patients with heart failure and as a prognostic marker in acute coronary syndromes. Specifically, the concentration of NT-proBNP in serum or plasma aids in the prognosis of ventricular systolic dysfunction and helps to differentiate between cardiac and non-cardiac causes. The median NT-proBNP plasma value for men and women in our cohort was calculated as 98 pg/ml, comparing favorably with reported values, in that a NT-proBNP concentration less than 100 pg/ml excludes acutely decompensated heart failure. Our calculated 97.5 percentile was slightly higher (359 pg/ml) than the 97.5 percentile in a group of 50-65-year-old persons (198 and 222 pg/ml for men and women, respectively) revealing the influence of age on this parameter. Because of its high tissue-specificity, cardiac troponin T is a cardiospecific, highly sensitive marker for myocardial damage. However, the troponin T concentrations in the plasma specimens from this cohort were all below the detection limit of 0.01 ng/ml, preventing any further data handling.  相似文献   
994.
Purpose In this exploratory, prospective study evaluated quality of life (QoL) changes in patients with diverse cancers during the first cycle of myelosuppressive chemotherapy.Patients and methods Of 80 patients enrolled, 71 were observed during one of five chemotherapy regimens: docetaxel; CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone); carboplatin-paclitaxel; carboplatin-docetaxel; and carboplatin-gemcitabine. Complete blood counts were taken weekly. QoL and symptom burden measures were administered at baseline and throughout the cycle, and included SF-36, Cancer Care Monitor (CCM), Hospital Anxiety and Depression Scale (HADS), and Psychosocial Adjustment to Illness Scale (PAIS). Using generalized estimating equations, we modeled the change in each measure from baseline to the end of each week using the following covariates: baseline QoL measure, baseline SF-36 Physical and Mental Health Summary scores, sex, age, cycle week, grade 4 neutropenia any time in the past 7 days (yes/no), and the interaction of the latter two covariates.Results Of the 71 patients observed, 33 developed grade 4 neutropenia during the first 2 weeks. Changes from baseline in SF-36 Bodily Pain, HADS Anxiety, and PAIS Social Environment scores were significantly less favorable (P<0.05) when patients experienced grade 4 neutropenia any time in the past 7 days compared to when they did not (grade 0–3). A similar, but non-significant, trend was also observed for 12 other QoL measures.Conclusion QoL may be adversely affected up to 7 days after patients experience grade 4 (versus grade 0–3) neutropenia. Such findings need to be examined further in studies with adequate statistical power to test a priori hypotheses regarding specific QoL measures.Support for this work was provided by Amgen Inc.Portions of the research were previously presented at: Mayo Clinic Assessing Clinical Significance for QoL Measures in Oncology Research, State-of-the-Science, March 2002, Rochester, MN; the 27th Meeting of the European Society of Medical Oncology, October 2002, Nice, France; and the American Society of Hematology, December 2002, Philadelphia, PA.  相似文献   
995.
Angiogenesis and vascular remodeling support fibroproliferative processes; however, no study has addressed the importance of angiogenesis during fibro-obliteration of the allograft airway during bronchiolitis obliterans syndrome (BOS) that occurs after lung transplantation. The ELR(+) CXC chemokines both mediate neutrophil recruitment and promote angiogenesis. Their shared endothelial cell receptor is the G-coupled protein receptor CXC chemokine receptor 2 (CXCR2). We found that elevated levels of multiple ELR(+) CXC chemokines correlated with the presence of BOS. Proof-of-concept studies using a murine model of BOS not only demonstrated an early neutrophil infiltration but also marked vascular remodeling in the tracheal allografts. In addition, tracheal allograft ELR(+) CXC chemokines were persistently expressed even in the absence of significant neutrophil infiltration and were temporally associated with vascular remodeling during fibro-obliteration of the tracheal allograft. Furthermore, in neutralizing studies, treatment with anti-CXCR2 Abs inhibited early neutrophil infiltration and later vascular remodeling, which resulted in the attenuation of murine BOS. A more profound attenuation of fibro-obliteration was seen when CXCR2(-/-) mice received cyclosporin A. This supports the notion that the CXCR2/CXCR2 ligand biological axis has a bimodal function during the course of BOS: early, it is important for neutrophil recruitment and later, during fibro-obliteration, it is important for vascular remodeling independent of neutrophil recruitment.  相似文献   
996.
We determined allelic polymorphisms in the mec complexes of 524 methicillin-resistant Staphylococcus aureus isolates by partial or complete sequencing of three mec genes, mecA, mecI, and mecR1. The isolates had been collected over a 10-year period from patients living in rural Wisconsin, where the use of antibiotics was expected to be lower than in the bigger cities. Of the 18 mutation types identified, 16 had not been described previously. The five most common mutations were a mutation 7 nucleotides (nt) upstream from the start site (G-->T) in the mecA promoter (34.7%), an E246G change encoded by mecA (2.2%), a cytosine insertion at codon 257 in mecA (13.2%), an N121K change encoded by mecI (7.8%), and a major mecI-mecR1 deletion designated as a class B1 mec complex deletion type (25.4%). There was a high degree of conservation of the amino acid sequence of MecR1. Strains with the same mutations had variable resistance to oxacillin, and the median MIC for isolates that harbored the 7-nt-upstream mutation was lower than that for strains harboring other mutations. Our data suggest that the mecA promoter mutation plays a more important role in determining methicillin resistance than mutations in mecI and mecA do. Eighty-five percent of the tested isolates (n = 148) with the mecA promoter mutation and the class B1 mec complex deletion belonged to the same major clonal group, identified as MCG-2, and harbored the type IV staphylococcal cassette chromosome mec DNA. There was also a wide range of oxacillin MICs for strains with wild-type mecA, mecI, and mecR1 sequences, suggesting that the genetic backgrounds of clinical strains are significant in determining susceptibility to methicillin.  相似文献   
997.
Diagnosis of gastritis by means of a combination of serological analyses   总被引:10,自引:0,他引:10  
Background: Gastroscopy and examination of biopsy is normally required for diagnosis of gastritis. This is costly and inconvenient for the patient, and there is a need for a simple pregastroscopic screening method to reduce the endoscopy workload. Our aim was to develop a serological screening test for gastritis. Methods: Sera from subjects examined with gastroscopy and biopsy were analyzed for H,K-ATPase antibodies, Helicobacter pylori antibodies and pepsinogen I. The diagnoses were normal gastric mucosa (n=50), duodenal ulcer (n=53) and atrophic corpus gastritis, with (n=50) or without pernicious anemia (n=46). Results: An evaluation scheme was constructed to optimize the diagnostic agreement between serology and gastric mucosal morphology. The sensitivity to detect gastritis was 98% (146/149) (95% CI 94–100%) and the specificity 84% (42/50) (95% CI 71–93%). Additional sera from 483 subjects from the general population were analyzed. There was a good agreement between serology and gastric mucosal morphology. Conclusions: Assays of multiple serum analytes are useful for the initial screening of gastritis. They are complementary to upper gastroscopy by identification of subjects with a normal gastric mucosa, those who qualify for eradication of H. pylori, and those who have developed atrophy and are at risk of developing malignancy and, therefore, require gastroscopic examination.  相似文献   
998.
Using colorectal cancer (CRC) as an example, we present the hypothesis that quantitative immunoassays for wild-type (full-length) proteins can be used to identify carriers of traits for hereditary diseases. In the case of hereditary CRC, this involves identifying individuals with germline mutations in a mismatch-repair (MMR) gene (mainly hMSH2 or hMLH1) or in the adenomatous polyposis coli (APC) gene. Because expression of wild-type protein should reflect wild-type gene dosage, we predicted that individuals harboring a germline mutation will have a reduction of approximately 50% in expression in lymphocytes of the corresponding full-length protein. In this pilot study, we tested lymphoblastoid cell lines that had been established from controls and individuals with, or at high risk for, hereditary CRC: 9 lines from healthy, unaffected individuals; 4 from affected members in familial adenomatous polyposis families (with known germ-line APC mutation); 42 from CRC patients in our Familial CRC Registry (increased risk of hereditary nonpolyposis colon cancer as assessed by family history, age at adenoma or carcinoma diagnosis, and other clinical criteria). For MSH2 and MLH1 we used western blots; for APC we used immunoprecipitation. All familial adenomatous polyposis lines had about 50% less immunoprecipitable full-length APC protein. Some cell lines (7 of 42) from Familial CRC Registry patients showed on western blots a reduction (mean 46%) in either MSH2 or MLH1 (relative to the other protein). All 7 subsequently were proved to contain a germline MMR mutation. We conclude that (1) because most of the expected CRC-causing germ line mutations are truncation-causing, immunoassays for wild-type protein should be able to identify most individuals with hereditary CRC-causing traits; (2) these assays, which are more practical and inexpensive than current mutation-detecting tests for hereditary CRC traits, have the potential for commercial development into broad-based population screens of high-risk patients and their families and the potential to save both lives and health-care dollars; (3) this strategy may be useful for other hereditary cancers and even other hereditary diseases; (4) our approach has the potential to greatly benefit public-health programs for cancer control.  相似文献   
999.
Guinea pigs hyperimmunized with single protein antigens or hapten conjugates emulsified in complete adjuvants produced two types of precipitating antibodies with different electrophoretic mobilities. "Slow" migrating antibody generally appeared earlier and "fast" migrating antibody later in the course of immunization. Animals initially immunized by the intraperitoneal route with hapten conjugates without adjuvants produced primarily fast migrating antibody. Purified guinea pig antibodies were also separable into slow and fast migrating components by electrophoresis in supporting media. Using suitable antisera prepared in rabbits hyperimmunized with guinea pig serum, it was demonstrated that slow and fast antibodies have both common and distinct antigenic determinants. Analytical ultracentrifugation disclosed that both antibodies have sedimentation coefficients of approximately 7S. These antibodies have been designated guinea pig 7Sγ1 and 7Sγ2.  相似文献   
1000.
Introduction: Burn healing is a complicated process and very few treatments can positively alter its effects. The aim of this study was to investigate the effects Salvia miltiorrhiza (SM -Danshen), a traditional Chinese medicine, on burn wound healing.

Material and methods: Twenty rats were included in this study and divided into two groups. 3?×?2?cm wide burn areas were created in the dorsal skin of all the animals with thermal contact. Intraoral 1?ml/day saline and 1?g/kg/day SM were given in control and experiment groups, respectively. Fourteen days following the burn injury burn zones were evaluated with indocyanine green-SPY imaging device, and multiple samples were collected for histopathological evaluation. Standard photographs were taken for the evaluation of necrotic skin areas.

Results: Neovascularization was increased in the SM group when compared with the control group (p?=?0.0406). SPY studies revealed a meaningful increase in the tissue perfusion in the SM group (p?=?0.0286). The average amount of necrotic area in the control and experiment group on the postoperative 14th day was 71.6% (±16.51) and 42.5% (±10.64) respectively (p?=?0.0002).

Conclusion: Our study shows that SM can decrease the amount of necrosis in burn wounds by increasing tissue perfusion and neovascularization.  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