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   3382篇
  免费   218篇
  国内免费   16篇
耳鼻咽喉   26篇
儿科学   160篇
妇产科学   130篇
基础医学   427篇
口腔科学   133篇
临床医学   338篇
内科学   710篇
皮肤病学   61篇
神经病学   349篇
特种医学   369篇
外科学   231篇
综合类   72篇
预防医学   176篇
眼科学   29篇
药学   253篇
中国医学   10篇
肿瘤学   142篇
  2022年   29篇
  2021年   55篇
  2020年   28篇
  2019年   42篇
  2018年   68篇
  2017年   50篇
  2016年   45篇
  2015年   62篇
  2014年   103篇
  2013年   129篇
  2012年   166篇
  2011年   147篇
  2010年   101篇
  2009年   118篇
  2008年   130篇
  2007年   137篇
  2006年   120篇
  2005年   117篇
  2004年   105篇
  2003年   91篇
  2002年   113篇
  2001年   73篇
  2000年   92篇
  1999年   86篇
  1998年   105篇
  1997年   72篇
  1996年   87篇
  1995年   66篇
  1994年   70篇
  1993年   61篇
  1992年   78篇
  1991年   74篇
  1990年   65篇
  1989年   89篇
  1988年   69篇
  1987年   57篇
  1986年   48篇
  1985年   41篇
  1984年   33篇
  1983年   32篇
  1982年   36篇
  1981年   37篇
  1980年   23篇
  1979年   22篇
  1978年   28篇
  1977年   27篇
  1976年   17篇
  1975年   26篇
  1974年   15篇
  1973年   17篇
排序方式: 共有3616条查询结果,搜索用时 15 毫秒
51.
Quality of care assessment is in a rather rudimentary state of development in most long-term health care settings. Some of the mandates and initiatives in this area of evaluation are described and discussed. A few caveats are presented and suggestions made as to appropriate approaches to quality assessment in chronic care facilities, which are different in many respects from the more traditional approaches used in acute care hospitals. Of particular importance, and at the same time of greatest difficulty, is the assessment of quality of life in institutions where many patients spend the remainder of their lives.  相似文献   
52.
This randomized controlled study compared two types of case management for skilled nursing level patients living at home: the centralized individual model and the neighborhood team model. The team model differed from the individual model in that team case managers performed client assessments, care planning, some direct services, and reassessments; they also had much smaller caseloads and were assigned a specific catchment area. While patients in both groups incurred very high estimated health services costs, the average annual cost during 1983-85 for team cases was 13.6 percent less than that of individual model cases. While the team cases were 18.3 percent less expensive among "old" patients (patients who entered the study from the existing ACCESS caseload), they were only 2.7 percent less costly among "new" cases. The lower costs were due to reductions in hospital days and home care. Team cases averaged 26 percent fewer hospital days per year and 17 percent fewer home health aide hours. Nursing home use was 48 percent higher for the team group than for the individual model group. Mortality was almost exactly the same for both groups during the first year (about 30 percent), but was lower for team patients during the second year (11 percent as compared to 16 percent). Probable mechanisms for the observed results are discussed.  相似文献   
53.
Zusammenfassung Die Untersuchung vergleicht unter Verwendung zweier Placebo-Kontrollgruppen veränderte Bewußtseinszustände, die unter den Halluzinogenen (–)9-trans-Tetrahydrocannabinol (9-THC) und N,N-Dimethyltryptamin (DMT) auftreten. 24 Probanden erhielten 250g 9-THC p.o. pro kg Körpergewicht, und 26 Probänden wurde 250g DMT pro Körpergewicht i.m. appliziert. Die Placebogruppe bestand aus insgesamt 24 Probanden. Die Effekte wurden retrospektiv mit einem Fragebogen erfaßt, dessen Items nach inhaltlichen und testtheoretischen Gesichtspunkten zu den folgenden 8 Skalen zusammengefaßt wurden: Optische Sinnestäuschungen, akustische Sinnestäuschungen, Konzentrations- und Gedächtnisstörungen, Derealisationserscheinungen, Depersonalisationserscheinungen, Leiberlebensveränderungen, euphorisches Zustandsbild und dysphorisches Zustandsbild.In allen acht Syndromen unterschieden sich die beiden Halluzinogene signifikant von Placebo. Zwischen den Halluzinogenen konnte jedoch keine signifikante Differenz nachgewiesen werden. In der Skala optische Sinnestäuschungen zeigte sich als Tendenz, daß DMT hier eine stärkere Wirkung als 9-THC entfaltet.Methodische Probleme des Vergleichs verschiedener Halluzinogene werden diskutiert.  相似文献   
54.
OBJECTIVES: To determine the spectrum of N and G genotypes of respiratory syncytial virus (RSV) causing respiratory tract infection and whether particular genotypes are associated with severity of infection. PATIENTS AND METHODS: Nasopharyngeal aspirates (NPAs) were obtained from 114 infants with acute respiratory tract infection due to RSV over two seasons. Viral mRNA was extracted from NPAs or cultured virus, reverse transcribed, and the cDNA amplified by the polymerase chain reaction using primers directed to parts of the N and G gene respectively. Amplicons were separately digested with four different restriction endonucleases for each gene. The fragments were separated by agarose gel, electrophoresis, and the electrophoretic patterns used to assign the various genotypes. Disease severity was assessed as very mild (upper respiratory tract signs only), mild (coryza and signs of lower respiratory tract infection), moderate (requiring nasogastric or intravenous fluids), and severe (requiring oxygen or ventilation). RESULTS: Five of the six known N genotypes were detected, but NP4 and NP2 were found most frequently. There was no association between N genotype and disease severity. Six G (SHL) genotypes were detected. Significantly (p = 0.04) more of the infants infected with the SHL2 genotype had severe or moderate disease. CONCLUSIONS: During the seasonal peaks of RSV respiratory tract infection at least 10 different RSV genotypes cocirculated. While there is no association between N genotypes and disease severity, infection with the SHL2 G genotype appears to result in moderate to severe disease.  相似文献   
55.
56.
IL Ackerman  CA Karn  SC Denne  GJ Ensing  CA Leitch 《Pediatrics》1998,102(5):1172-1177
OBJECTIVE: The purpose of this study was to determine the effect of left-to-right shunting on the resting energy expenditure (REE), total energy expenditure (TEE), and energy intake in a group of 3- to 5-month-old infants with moderate to large unrepaired ventricular septal defects (VSDs) compared with age-matched, healthy infants. METHODS: Eight infants with VSDs and 10 healthy controls between 3 to 5 months of age participated in the study. Indirect calorimetry was used to measure REE and the doubly-labeled water method was used to measure TEE and energy intake. An echocardiogram and anthropometric measurements were performed on all study participants. Daily urine samples were collected at home for 7 days. Samples were analyzed by isotope ratio mass spectrometry. Data were compared using analysis of variance. RESULTS: No significant differences were found in REE (VSD, 42.2 +/- 8.7 kcal/kg/d; control, 43.9 +/- 14.1 kcal/kg/d) or energy intake (VSD, 90.8 +/- 19.9 kcal/kg/d; control, 87.1 +/- 11.7 kcal/kg/d) between the groups. The percent total body water was significantly higher in the VSD infants and the percent fat mass was significantly lower. TEE was 40% higher in the VSD group (VSD, 87.6 +/- 10.8 kcal/kg/d; control, 61.9 +/- 10.3 kcal/kg/d). The difference between TEE and REE, reflecting the energy of activity, was 2.5 times greater in the VSD group. CONCLUSIONS: REE and energy intake are virtually identical between the two groups. Despite this, infants with VSDs have substantially higher TEE than age-matched healthy infants. The large difference between TEE and REE in VSD infants suggests a substantially elevated energy cost of physical activity in these infants. These results demonstrate that, although infants with VSDs may match the energy intake of healthy infants, they are unable to meet their increased energy demands, resulting in growth retardation.  相似文献   
57.
58.
In this paper, a ternary system of albumin-protamine-oligonucleotide nanoparticles (AlPrO-NP) recently developed by Vogel et al. [V. Vogel, D. Lochmann, J. Weyermann, G. Mayer, C. Tziatzios, J.A. van den Broek, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which could serve as a potential drug delivery system for antisense oligonucleotides. Former studies of binary protamine-oligonucleotide nanoparticles showed two main disadvantages: (i) aggregation of the particles within a few minutes in the presence of salt; (ii) low intracellular dissociation between protamine and oligonucleotide, especially phosphorothioates. To overcome these problems, human serum albumin (HSA) as a non-toxic, biodegradable macromolecule was introduced as protective colloid. The assembly process of AlPrO-NP was investigated by small angle X-ray scattering (SAXS), fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS) measurements and scanning electron microscopy (SEM). 'Initial complexes' of HSA and protamine sulphate with a mean hydrodynamic diameter (dh) of about 10-14 nm were found. After adding oligonucleotides (unmodified, phosphorothioate DNA and small interfering RNA), nanoparticles (NPs) were assembled in water and in isotonic media with a dh in a range of 230-320 nm for most preparations. The chemical composition of the particles was investigated by high performance liquid chromatography and fluorescence spectrometry. The whole amount of oligonucleotides (30 microg) was entrapped into the particles at a 1:2 mass ratio (oligonucleotide/protamine). Approximately 7-10% (w/w) of the HSA was bound to the particles. The surface charge of the particles ranged from about +12 to -60 mV depending on the protamine concentration and the ionic conditions. The size and the molecular weight of the components, initial complexes and two model NP preparations were calculated from FCS data. These data verified the PCS, SEM and SAXS measurements.  相似文献   
59.
Transplantation of embryonic nigral tissue is used as an experimental therapy for patients with Parkinson's disease but is hampered by a limited survival rate of dopaminergic neurons. Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for nigrostriatal dopaminergic neurons, and the present in vitro study aimed at improving the survival of dopaminergic neurons in porcine mesencephalic brain slice cultures by adding transfected, immortalized, temperature-sensitive GDNF-releasing HiB5 cells (HiB5-GDNF). Embryonic (E27/28) porcine ventral mesencephalic brain slices were placed on membrane inserts in six-well plates with serum-containing medium, and HiB5-GDNF, nontransfected HiB5 cells (HiB5-control), or green fluorescent protein-producing HiB5 cells (HiB5-GFP) were seeded onto each tissue slice. The concentration of GDNF in the coculture medium was 0.49 +/- 0.13 ng/ml at day 9 and 0. 22 +/- 0.05 ng/ml at day 19 (mean +/- SEM) as measured by GDNF ELISA. The decrease in release of GDNF over time was paralleled by a gradual reduction in the number of HiB5-GFP cells expressing the reporter gene (EGFP). At day 12, HPLC analysis revealed that medium from HiB5-GDNF cocultures contained 2.0 times more dopamine than medium from HiB5-control cocultures. At day 21 there was 1.6 times more dopamine. Similar results were obtained for the dopamine metabolite 3,4-dihydroxyphenylacetic acid. At day 21, cell counts showed that HiB5-GDNF cocultures contained 1.5 times more tyrosine hydroxylase immunoreactive neurons than HiB5-control cocultures, which must be compared with a 1.8 fold increase after chronic treatment with rhGDNF (10 ng/ml). In conclusion, the better survival of HiB5-GDNF cocultures is promising for the generation of effective cell lines for local delivery of neurotrophic factors to intracerebral nigral grafts.  相似文献   
60.
A giant appendix is an extremely rare and improbable finding during surgery in suspected cases of acute appendicitis. Although this condition is primarily suggestive of neoplasia, it is usually due to an inflammatory or infectious disease. We report a case of Crohn's disease limited to the appendix, which was diagnosed after a short right ileocolectomy. Only 156 similar diagnoses have been reported in the literature to date. This disease appears to have a benign course and therefore differs from classical Crohn's ileocolitis. For this reason, these patients do not require any specific investigation or follow-up.  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