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   1491536篇
  免费   113630篇
  国内免费   2903篇
耳鼻咽喉   20740篇
儿科学   49980篇
妇产科学   39048篇
基础医学   208967篇
口腔科学   37927篇
临床医学   133332篇
内科学   302543篇
皮肤病学   30926篇
神经病学   122444篇
特种医学   60513篇
外国民族医学   673篇
外科学   229855篇
综合类   29411篇
现状与发展   2篇
一般理论   551篇
预防医学   111302篇
眼科学   33081篇
药学   108984篇
  3篇
中国医学   2721篇
肿瘤学   85066篇
  2021年   12709篇
  2019年   13537篇
  2018年   18527篇
  2017年   13942篇
  2016年   15260篇
  2015年   17492篇
  2014年   24610篇
  2013年   36453篇
  2012年   51426篇
  2011年   54234篇
  2010年   31905篇
  2009年   30353篇
  2008年   50993篇
  2007年   54374篇
  2006年   54251篇
  2005年   52993篇
  2004年   51360篇
  2003年   48995篇
  2002年   47803篇
  2001年   65936篇
  2000年   68009篇
  1999年   58389篇
  1998年   17678篇
  1997年   15805篇
  1996年   15997篇
  1995年   15101篇
  1994年   14197篇
  1993年   13209篇
  1992年   45571篇
  1991年   44408篇
  1990年   43030篇
  1989年   40862篇
  1988年   37589篇
  1987年   36844篇
  1986年   34304篇
  1985年   32979篇
  1984年   25056篇
  1983年   21061篇
  1982年   12716篇
  1981年   11604篇
  1979年   21835篇
  1978年   15342篇
  1977年   12977篇
  1976年   12116篇
  1975年   12948篇
  1974年   14989篇
  1973年   14403篇
  1972年   13146篇
  1971年   11914篇
  1970年   11185篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Mouse polyclonal antisera were raised to the Mr 130,000 and Mr 115,000 cell surface glycoproteins, desmocollins, of desmosomes from bovine nasal epithelium. Immunoblotting confirmed that the antisera were specific for the desmocollins. An immunofluorescence study showed that the antisera distinguished between the basal and suprabasal layers of bovine and human epidermis. The antibodies reacted with cultured keratinocytes only after calcium-induced stratification. In epidermis, therefore, there appears to be a difference between the desmocollins of basal and suprabasal cells that may be important in relation to epidermal differentiation. Previous work has shown that polyclonal antisera raised in other animals (guinea pigs and rabbits) against desmocollins, as well as against other desmosomal components, react with all desmosome-containing epithelia. In contrast, an immunofluorescence survey of bovine, rat, and human tissues showed that the present mouse antisera stained only suprabasal skin cells and the arachnoid layer of the meninges, demonstrating that these have common determinants that distinguished their desmocollins from those of all other tissues. The antibodies also stained 11 of 12 meningiomas and, therefore, may be useful as a marker not only for the diagnosis of these tumors but also for investigation of their histogenesis.  相似文献   
992.
Pharmacosomes--a novel drug delivery system   总被引:2,自引:0,他引:2  
  相似文献   
993.
To ascertain the effect of theophylline on the cardiac chronotropic response to beta-adrenergic stimulation, isoproterenol dose-response curves in healthy young subjects were compared during saline and theophylline maintenance infusions. Each study was repeated 1 to 3 weeks later to evaluate reproducibility. Neither the dose of isoproterenol required to raise the heart rate by 25 bpm (2.32 +/- 0.81 vs. 1.55 +/- 0.46 micrograms on day 1 and 1.28 +/- 0.22 vs. 1.27 +/- 0.25 micrograms on day 2) nor the slopes of the dose-response curves were affected by theophylline. Higher heart rates were observed after isoproterenol bolus dosing during theophylline than during saline infusion because of additive chronotropic effects of theophylline and isoproterenol. Since theophylline does not interact in a synergistic fashion with isoproterenol, phosphodiesterase inhibition appears to be an unlikely mechanism of the chronotropic effect of methylxanthines at therapeutic concentrations.  相似文献   
994.
995.
996.
997.
Piroximone (MDL 19,205), a new imidazolone derivative, was given intravenously to 14 patients with congestive heart failure (NYHA class II-III), while under constant daily doses of digitalis and diuretics. In the first 3 patients, we determined the dose safely eliciting a favorable hemodynamic response. The subsequent 11 patients received 1 mg/kg of piroximone intravenously, and the hemodynamic effects were compared with those of sodium nitroprusside (SN) at a dose-lowering mean blood pressure by 10-20 mm Hg. Piroximone increased heart rate (13.2 +/- 2.0 beats/min, mean +/- SEM) and lowered mean arterial pressure (9 +/- 2.3 mm Hg). Both agents reduced similarly wedge pressure (6.5 +/- 2.9 and 9 +/- 2.9 mm Hg, respectively, for SN and piroximone) and total peripheral resistance. Cardiac index was increased less by SN (15%) than piroximone (48%) (p less than 0.001), and stroke work index significantly enhanced only by piroximone (p less than 0.001). The changes in loading conditions induced by the two agents being similar, it is likely that piroximone not only acts by peripheral vasodilation, but also possesses positive inotropic properties. Myocardial oxygen demand, assessed indirectly by tension-time index, was not affected by piroximone. Thus, piroximone appears to combine well-balanced vasodilator and inotropic properties which make this new agent potentially very useful for the management of congestive heart failure.  相似文献   
998.
Power density producing damage at a probability of 0.5 (ie, damage threshold, DT-50) was determined for PMMA (with/without UV absorber) and Silicone intraocular lenses. Scattered light from a collinear diagnostic He:Ne beam was one of four damage monitors deployed to enhance the sensitivity of the system. In order of increasing laser resistance the following results were obtained: injection molded PMMA (1.9/GW/cm2) Silicone (2.63 GW/cm2) Lathe-cut PMMA (4.47 GW/cm2), Lathe-cut PMMA with UV absorber (8.32 GW/cm2), Cast-molded PMMA (12.30 GW/cm2). An analysis of variance revealed interclass differences significant at the .01 level. Cast-molded PMMA was the most laser-resistant IOL material.  相似文献   
999.
Clinico-x-ray-laboratory investigation, bronchoscopy were performed, respiratory function and ECG were studied in 212 patients with different forms of chronic bronchitis. Six groups of patients were defined with relation to the presence or absence of obstruction, its nature (permanent, transient), prevalence (small, medium and large bronchi), genesis of disease (inflammatory, allergic). The characteristics of the groups and their clinico-x-ray, functional and immunological features were presented. Treatment including methods of climatotherapy, exercise therapy, pharmacological agents (antibacterial, broncholithic and antihistaminic), physiotherapy and administered with relation to the defined groups, proved to be effective. The improvement of bronchial permeability was noted in 49.5% (ranging from 40.0 to 68.7% in different groups).  相似文献   
1000.
Peripheral arterial thromboembolism and thrombosis of arterial grafts continue to threaten viability of extremities. Percutaneous intra-arterial thrombolysis (IAT) and angiodilatation have afforded limb salvage in some of these patients. Proper patient selection appears to be the hallmark of success with IAT. During a recent three-year period, we used IAT in 32 extremities in 28 patients who had acute arterial insufficiency. Before IAT, 16 extremities were painful at rest, and 16 had incapacitating claudication. The overall success rate was 38%, but some degree of thrombolysis occurred in 88%. Limb salvage was achieved in 27 of 32 extremities (84%). Only five of 17 limbs (29%) with arterial graft thrombosis required no operation or an operation of lesser magnitude than predicted before IAT. Of six extremities with native arterial embolism, four (67%) were completely cleared with IAT. Major complications occurred in eight cases (25%), with two IAT-related deaths (6%). This study suggests that IAT is best reserved for individuals with acute limb ischemia caused by arterial embolus, those whose degree of ischemia would tolerate a 24-hour trial of IAT, and those whose femoral or tibial runoff is not likely to require remedial operation.  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