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   914067篇
  免费   73506篇
  国内免费   1875篇
耳鼻咽喉   13544篇
儿科学   26232篇
妇产科学   26331篇
基础医学   131938篇
口腔科学   27442篇
临床医学   80203篇
内科学   173760篇
皮肤病学   18290篇
神经病学   75670篇
特种医学   37577篇
外国民族医学   171篇
外科学   143362篇
综合类   24786篇
现状与发展   2篇
一般理论   292篇
预防医学   70363篇
眼科学   21576篇
药学   68263篇
中国医学   1669篇
肿瘤学   47977篇
  2018年   8511篇
  2016年   7854篇
  2015年   8751篇
  2014年   12296篇
  2013年   19021篇
  2012年   25535篇
  2011年   27091篇
  2010年   15527篇
  2009年   14121篇
  2008年   25784篇
  2007年   27964篇
  2006年   27669篇
  2005年   27213篇
  2004年   26660篇
  2003年   25820篇
  2002年   24795篇
  2001年   37924篇
  2000年   39190篇
  1999年   32354篇
  1998年   9672篇
  1997年   8934篇
  1996年   8780篇
  1995年   8261篇
  1994年   7984篇
  1992年   26885篇
  1991年   26289篇
  1990年   25805篇
  1989年   24902篇
  1988年   23389篇
  1987年   23073篇
  1986年   21929篇
  1985年   21334篇
  1984年   16669篇
  1983年   14223篇
  1982年   9054篇
  1981年   8376篇
  1980年   7833篇
  1979年   16934篇
  1978年   12254篇
  1977年   10339篇
  1976年   9478篇
  1975年   10285篇
  1974年   12739篇
  1973年   12274篇
  1972年   11613篇
  1971年   10748篇
  1970年   10288篇
  1969年   9979篇
  1968年   8995篇
  1967年   8292篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Adverse ocular effects associated with niacin therapy.   总被引:2,自引:0,他引:2       下载免费PDF全文
In a retrospective survey of patients taking medication for hyperlipidaemia, those taking niacin (nicotinic acid) were more likely (p < 0.05) to report sicca syndromes, blurred vision, eyelid oedema, and macular oedema compared with those who never took niacin. Additionally, 7% of those taking niacin discontinued the drug owing to adverse ocular side effects, while none of the other lipid lowering agents were found to cause these side effects (p = 0.016). Data from spontaneous reporting systems support a possible association of decreased vision, cystoid macular oedema, sicca-like symptoms, discoloration of the eyelids with or without periorbital or eyelid oedema, proptosis, loss of eyebrow or eyelashes, and superficial punctate keratitis with the use of niacin in high doses. Decreased vision may be marked, and if the drug is not discontinued, may progress to cystoid macular oedema. All ocular side effects listed above are reversible if the association with niacin is recognised and the drug is discontinued; both the incidence and severity of the ocular side effects seem to be dose dependent.  相似文献   
83.
84.
In 41 patients with recurrent sustained ventricular tachycardia and/or ventricular fibrillation an integrated pacemaker-defibrillator-system (PCD, Medtronic, model 7216 A or 7217 B) was implanted. In 21 out of 24 (88%) patients a new transvenous implantation technique in combination with a subcutaneous patch electrode was used. The implanted devices comprise antibradycardiac pacemaker functions, two different forms of antitachycardiac pacemaker functions (ramp and burst pacing), and internal cardioversion or defibrillation capabilities. During a mean follow-up of 8 months 147 episodes of ventricular tachycardia were detected, 131 of them were terminated successfully by antitachycardiac pacing; in 13 episodes internal cardioversion was applied to revert ventricular tachycardia. Twenty-seven episodes of ventricular fibrillation or rapid ventricular tachycardia (greater than 200/min) were detected and successfully terminated by internal defibrillation. In six patients with intermittent rapid atrial fibrillation, change of antiarrhythmic therapy was required to avoid activation of the device. The new integrated pacemaker-defibrillator systems improve therapy in patients with life-threatening tachyarrhythmias by reducing the number of internal cardioversions/defibrillations; the non-thoracotomy approach reduces the post operative risk.  相似文献   
85.
86.
To study micrometastasis at its earliest stages, the bacterial lacZ marker gene was introduced into human EJ Ha-ras-transformed BALB/c 3T3 cells (LZEJ), followed by their intravenous injection into nude mice. Lung micrometastases were easily identified by blue staining of lacZ-tagged cells minutes/hours after injection, permitting effective evaluation of establishment/clearance mechanisms of LZEJ cells. Different treatments were used to disable LZEJ cells (fixation, irradiation, or mitomycin C) to determine modulation of these processes--although unable to divide, these cells stain for lacZ expression for days after treatment. Fixation-killed cells generated large microfoci (> 13-15 cells/focus) with well-rounded morphologies while live, irradiated, or mitomycin-treated cells generated smaller, irregularly shaped foci (3-7 cells/focus). Fixed-cell foci were cleared more slowly from lungs than the other three classes, even when prefiltered to remove large aggregates. All foci of disabled cells were eventually cleared while a basal level of live-cell foci persisted. Co-injection of fixed and live cells (or preinjection of fixed cells, followed by live cells) resulted in complete clearance of live-cell microfoci; in contrast, preinjection of live cells (then injection of fixed cells) led to survival of live-cell micrometastases. Therefore, altered deformability and/or cell surface interactions of tumor cells modulate the effectiveness of host-clearing mechanisms in the lung and in some situations these altered cells facilitate clearance of live tumor cells that are normally tumor-progressing.  相似文献   
87.
Nephrotoxic cysteine conjugates derived from a variety of halogenated alkenes are enzymatically activated via the beta-lyase pathway to yield reactive sulfur-containing metabolites which bind covalently to cellular macromolecules. Mitochondria contain beta-lyase enzymes and are primary targets for binding and toxicity. Previously, mitochondrial protein and/or DNA have been considered as molecular targets for cysteine conjugate metabolite binding. We now report that metabolites of nephrotoxic cysteine conjugates form covalent adducts with rat kidney mitochondrial phospholipids. Rat kidney mitochondria were incubated with the 35S-labeled conjugates S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFEC), S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC), S-(1,2-dichlorovinyl)-L-cysteine, and S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine. Quantitation of metabolite binding to whole mitochondria and to mitochondrial protein and lipid fractions revealed that as much as 42% of the 35S-label associated with the mitochondria was found in the lipid fraction. Total lipids were also extracted from 35S-treated mitochondria and separated by thin-layer chromatography. 35S-Containing metabolites were found in the lipid fractions from mitochondria treated with each of the conjugates. Lipids from both [35S]CTFC- and [35S]-TFEC-treated mitochondria contained major 35S-labeled lipid adducts which had similar mobility by thin-layer chromatography. Fatty acid analysis, 19F and 31P NMR spectroscopy, and mass spectrometric analyses confirmed that the major TFEC and CTFC adducts are thioamides of phosphatidylethanolamine.  相似文献   
88.
PATIENTS AND METHOD: The aim of the present study was to contribute to a more accurate indication and better integration of developing third molar transplantation into orthodontic space management, using the results gleaned from the authors' own pool of patients. For this purpose, a clinical and radiographic examination of 61 transplanted developing molars in 57 patients was carried out after an average of 3.3 years. RESULTS: The overall success rate was 85%. Failure was due in 10% of cases to impaired periodontal healing (inflammatory root resorption, ankylosis, or increased pocket probing depths) and in 5% of cases to insufficient or arrested postoperative root development accompanied by increased transplant mobility. The incidence of postoperative cessation of further root development was significantly higher (p = 0.011) in transplants at early developmental stages, which also had a negative impact on the final root length, the crown-root ratio and the mobility values of these transplants. CONCLUSIONS: The transplantation of developing third molars should be given stronger consideration in treatment plans for orthodontic space management although it represents a real alternative to orthodontic space closure only in exceptional cases. However, unlike implantological or prosthodontic treatment, it offers an opportunity to replace a missing or non-retainable tooth with a patient's own vital and fully functional tooth, provided the appropriate transplant is selected.  相似文献   
89.
90.
The authors aimed at evaluating the impact of psychotraumas in psychiatric outpatients. One hundred forty psychiatric outpatients were consecutively included, without distinction of their current pathology. They filled in an inventory of potentially traumatic experiences, a psychological dissociative experiences scale, a somatoform dissociative experiences questionnaire, and underwent a structured interview for diagnosis of posttraumatic stress disorder (according to the DSM-IV). One hundred subjects related psychological trauma, and 76 patients suffered from posttraumatic stress disorder. Dissociative disorders are found significantly correlated with traumatic experience and to posttraumatic stress disorder. The traumatic impact is found more substantial as the number of events was elevated. This study confirms the elevated prevalence of the psychological traumas and psychotraumatic aftermaths in outpatients of a department of psychiatry, independently from the mental disorder.  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