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   1334135篇
  免费   95952篇
  国内免费   2904篇
耳鼻咽喉   19713篇
儿科学   40229篇
妇产科学   38659篇
基础医学   187201篇
口腔科学   39811篇
临床医学   112615篇
内科学   262362篇
皮肤病学   30205篇
神经病学   106356篇
特种医学   53665篇
外国民族医学   435篇
外科学   208208篇
综合类   31043篇
现状与发展   6篇
一般理论   436篇
预防医学   92030篇
眼科学   31357篇
药学   100055篇
  4篇
中国医学   2987篇
肿瘤学   75614篇
  2018年   11738篇
  2015年   11872篇
  2014年   16683篇
  2013年   25238篇
  2012年   32995篇
  2011年   34859篇
  2010年   20728篇
  2009年   20225篇
  2008年   33571篇
  2007年   36675篇
  2006年   37249篇
  2005年   36004篇
  2004年   35080篇
  2003年   34058篇
  2002年   33584篇
  2001年   63613篇
  2000年   65322篇
  1999年   55387篇
  1998年   14650篇
  1997年   13458篇
  1996年   12937篇
  1995年   12221篇
  1994年   11467篇
  1992年   42762篇
  1991年   41280篇
  1990年   40553篇
  1989年   39550篇
  1988年   36963篇
  1987年   36408篇
  1986年   34899篇
  1985年   33101篇
  1984年   24822篇
  1983年   21052篇
  1982年   12664篇
  1981年   11568篇
  1980年   10772篇
  1979年   23923篇
  1978年   17068篇
  1977年   14834篇
  1976年   13386篇
  1975年   15267篇
  1974年   18080篇
  1973年   17560篇
  1972年   16810篇
  1971年   15717篇
  1970年   14914篇
  1969年   14346篇
  1968年   13460篇
  1967年   12015篇
  1966年   11258篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
851.
We report the identification of a new transthyretin (TTR) gene mutation and variant protein, Glu61Gly, in a 55-year-old man with progressive cardiomyopathy, mild peripheral neuropathy and bilateral carpal tunnel syndrome. A diagnosis of TTR-associated familial amyloidosis (ATTR) was considered after an endomyocardial biopsy revealed amyloid deposits in the heart of a patient who had no family history of amyloidosis and no evidence of a plasma cell dyscrasia. Serum screening for a TTR variant by isoelectric focusing (IEF) was positive and prompted further studies to identify the genetic abnormality and to characterize the amyloidogenic protein. Direct DNA sequence analysis of all four coding regions in the TTR gene demonstrated heterozygosity in exon 3. Near equal amounts of guanine (G) and adenine (A) were observed at the second base position of codon 61. The wild-type (GAG) and mutated (GGG) sequences found in codon 61 correspond to glutamic acid (Glu) and glycine (Gly) residues, amino acids which differ in mass by -72 Da. Mass spectrometric analyses of TTR immunoprecipitated from serum showed the presence of both wild-type and variant proteins. The observed mass results for the wild-type and variant proteins were consistent with the predicted values calculated from the genetic analysis data.  相似文献   
852.
853.
The cementoblastoma is a rare benign tumor of odontogen origin that interests the roots of the teeth especially the lower molars. The evolution is often silent, the radiological exam is not specific, the diagnosis of certainty is histological. The surgical treatment assures the recovery without aftermath. The authors report a case of cementoblastoma at a patient of 37 years for which he has benefited of a resection by vestibular way and debate diagnosis and therapeutic modes of this affection.  相似文献   
854.
855.
With topical treatment of skin diseases, the requirement of a high and reproducible drug uptake often still is not met. Moreover, drug targeting to specific skin strata may improve the use of agents which are prone to cause local unwanted effects. Recent investigations have indicated that improved uptake and skin targeting may become feasible by means of nanoparticular systems such as solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and nanoemulsions (NE). Here we describe techniques to characterize drug loading to carrier systems and skin penetration profiles by using the lipophilic dye nile red as a model agent. Since the mode of drug association with the particle matrix may strongly influence the efficiency of skin targeting, parelectric spectroscopy (PS) was used to differentiate between matrix incorporation and attachment to the particle surface and fluorescence spectroscopy (FS) to solve dye distribution within NLC particles. Nile red was incorporated into the lipid matrix or the covering tensed shell, respectively, of SLN and NLC with all the lipids studied (Compritol, Precirol, oleic acid, Miglyol). In NLC, the dye was enriched in the liquid phase. Next, nile red concentrations were followed by image analysis of vertical sections of pigskin treated with dye-loaded nanoparticular dispersions and an oil-in-water cream for 4 and 8 h in vitro. Following the SLN dispersions, dye penetration increased about fourfold over the uptake obtained following the cream. NLC turned out less potent (相似文献   
856.
INTRODUCTION: The use of botulinum toxin injection therapy is soaring significantly today, with an ever-wider field of applications despite well-known side effects of the treatment. This article aims at analysing the medicolegal practices of practitioners who use this therapy, especially the information given to patients and finding a common practice for providing that information. METHODS: We sent a questionnaire to 340 practitioners who might use the therapy (physiatrists, neurologists, ophthalmologists, ENT specialists, plastic surgeons) working in hospitals and in physical therapy and rehabilitation centres in France. Besides mentioning the possible side effects of the therapy, the questionnaire focused on how such information was transmitted before the injection. RESULTS: Data collection and analysis were performed by use of a spreadsheet software programme. A total of 124 questionnaires were analysed. We did not analyse the items dealing with side effects. Sixty-five percent of the responders said they did not seek statutory authorisation for injections. Only 31% provided written, detailed information and 12% required a signed consent form. Complaints were rare, approximately 12%, were written or verbal, and were always dismissed. DISCUSSION: Side effects after botulinum toxin injection are clearly described in the medical literature. Therefore, it is of utmost importance for this product to be used therapeutically and only by experienced therapists who will carefully respect the product's standard rules of use and inform their patients to the best of their ability. Issuing a detailed letter of information describing all the side effects seems necessary. We suggest a model information letter such as that provided to the patients in our facility. CONCLUSION: Botulinum toxin is a very worthwhile product for numerous abnormalities but has side effects, often brief, at the site of the injection. Therefore it is our duty to inform patients effectively.  相似文献   
857.
OBJECTIVES: To determine the modification in postoperative D-dimer level as a function of the surgical act and to assess the relevance of this measure for diagnosing thromboembolism. METHOD: A cohort of 179 patients was followed: group 1 comprised 128 patients undergoing lower limb arthroplasty, group 2 comprised 29 patients undergoing lower limb surgery without implant, and group 3 comprised 22 patients undergoing spinal or upper limb surgery. D-dimer level was systematically measured on admission and then once a week for 4 weeks. Doppler ultrasonography was performed on clinical suspicion of deep vein thrombosis. D-dimer levels were compared between patients with and without deep vein thrombosis. RESULTS: D-dimer levels were constantly elevated postsurgery (2- to 6-fold above normal) and returned to normal by week 4 in groups 2 and 3 but remained elevated in group 1 (3-fold above normal). Deep vein thrombosis was suspected in 45 cases and confirmed by Doppler ultrasonography in 10 cases. D-dimer level was not significantly different between patients with deep vein thrombosis and those without. DISCUSSION AND CONCLUSIONS: In the postoperative period, measurement of D-dimer level does not aid in diagnosing thromboembolism since its constant high level obviates any negative predictive value.  相似文献   
858.
Previously, the lower generation (DAB 8-generation 2 and DAB 16-generation 3) polypropylenimine dendrimers have been shown to be effective gene delivery systems in vitro. In the current work, we sought to: (a) test the effect of the strength of the carrier, DNA electrostatic interaction on gene transfer and (b) to study the in vivo gene transfer activity of these low molecular weight (<1687 Da) non-amphiphilic plain and quaternary ammonium gene carriers. Towards this aim, methyl quaternary ammonium derivatives of DAB 4 (generation 1), DAB 8, DAB 16 and DAB 32 (generation 4) were synthesised to give Q4, Q8, Q16 and Q32, respectively. Quaternisation of DAB 8 proved to be critical in improving DNA binding, as evidenced by data from the ethidium bromide exclusion assay and dendrimer-DNA colloidal stability data. This improved colloidal stability had a major effect on vector tolerability, as Q8-DNA formulations were well tolerated on intravenous injection while a similar DAB 8-DNA dose was lethally toxic by the same route. Quaternisation also improved the in vitro cell biocompatibility of DAB 16-DNA and DAB 32-DNA dendrimer complexes by about 4-fold but not that of the lower generation DAB 4-DNA and DAB 8-DNA formulations. In contrast to previous reports with non-viral gene delivery systems, the intravenous administration of DAB 16-DNA and Q8-DNA formulations resulted in liver targeted gene expression as opposed to the lung targeted gene expression obtained with the control polymer-Exgen 500 [linear poly(ethylenimine)] and a lung avoidance hypothesis is postulated. We conclude that the polypropylenimine dendrimers are promising gene delivery systems which may be used to target the liver and avoid the lung and also that molecular modifications conferring colloidal stability on gene delivery formulations have a profound effect on their tolerability on intravenous administration.  相似文献   
859.
Due to limited aqueous solubility of dorzolamide at physiologic pH, the pH of Trusopt eye drops (cont. 2% dorzolamide) has to be kept at about 5.65, and to increase the topical bioavailability of the drug from Trusopt the contact time of the drug with the eye surface is increased by increasing the viscosity of the eye drops to 100 cps. This low pH and high viscosity can lead to local irritation. In this study, dorzolamide hydrochloride was formulated as 2% and 4% low viscosity solutions (viscosity 3 to 5 cps) containing randomly methylated beta-cyclodextrin at pH 7.45. These formulations were evaluated in rabbits. The animals were sacrificed at various time points after topical administration of the drug and the dorzolamide concentration determined in the different parts of the eye. Trusopt was used as a reference standard. The topical availability of dorzolamide from the cyclodextrin-containing eye drops appeared to be comparable to that from Trusopt and the drug reached retina and optic nerve to give measurable concentrations for at least 8 h after administration of the eye drops.  相似文献   
860.
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