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   16570篇
  免费   1091篇
  国内免费   118篇
耳鼻咽喉   161篇
儿科学   374篇
妇产科学   578篇
基础医学   2212篇
口腔科学   520篇
临床医学   1485篇
内科学   3527篇
皮肤病学   312篇
神经病学   1323篇
特种医学   531篇
外国民族医学   3篇
外科学   2469篇
综合类   302篇
一般理论   9篇
预防医学   1259篇
眼科学   216篇
药学   932篇
  1篇
中国医学   94篇
肿瘤学   1471篇
  2023年   127篇
  2022年   253篇
  2021年   580篇
  2020年   312篇
  2019年   459篇
  2018年   527篇
  2017年   369篇
  2016年   411篇
  2015年   464篇
  2014年   613篇
  2013年   760篇
  2012年   1217篇
  2011年   1204篇
  2010年   655篇
  2009年   575篇
  2008年   935篇
  2007年   972篇
  2006年   817篇
  2005年   821篇
  2004年   800篇
  2003年   677篇
  2002年   659篇
  2001年   414篇
  2000年   391篇
  1999年   386篇
  1998年   144篇
  1997年   152篇
  1996年   101篇
  1995年   93篇
  1994年   102篇
  1993年   78篇
  1992年   200篇
  1991年   173篇
  1990年   145篇
  1989年   162篇
  1988年   99篇
  1987年   148篇
  1986年   96篇
  1985年   71篇
  1984年   83篇
  1983年   51篇
  1982年   29篇
  1981年   36篇
  1980年   31篇
  1979年   51篇
  1978年   27篇
  1976年   36篇
  1975年   25篇
  1974年   37篇
  1972年   31篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: The recurrent chronic orofacial swelling caused by orofacial granulomatosis (OFG) can cause significant cosmetic and functional problems but can be prevented if the disease is diagnosed early and promptly treated. Although the enlargement of the lips is described to be the most common presenting complaint, the clinical onset of OFG may be characterized by minor associated mucosal and neurological manifestations, making early diagnosis very difficult or, sometimes, merely presumable. PATIENTS AND METHODS: We retrospectively analyzed the clinical manifestations of 19 patients with OFG, who were examined at our institution between 1998 and 2002, in order to determine their initial manifestations and presenting symptoms. RESULTS: A total of 10 patients showed classical recurrent enlargement of the lips (six lower; four upper) as presenting symptom. In the other nine patients, OFG onset was characterized by transient unilateral facial nerve palsy (two cases), intraoral manifestations (two cases), recurrent swelling of the periorbital area (two cases), of the chin (one case), of the zygomatic area (one case), and of the cheeks (one case). CONCLUSION: Our data underlined that OFG onset could be frequently characterized by widely variable, multiform, and temporary clinical findings. Involvement of atypical sites of the orofacial region and presence of single minor manifestations may occur as presenting symptoms, often preceding the development of traditional clinical findings.  相似文献   
2.
Three isoforms of human tau protein were compared for their abilities to induce microtubule assembly. The three isoforms, tau 3 (tau containing three microtubule-binding domains), tau 4 (tau containing four microtubule-binding domains) and tau 4L (tau containing four microtubule binding domains plus a 58-amino-acid insert near the N-terminus) were expressed in E. coli and purified using ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. All three isoforms induced microtubule assembly at micromolar concentrations and showed similar critical concentrations for assembly of 0.4-0.45 microM. However, tau 4 induced microtubule formation at a rate five- to tenfold faster than either tau 3 or tau 4L. The rate of microtubule elongation seen with tau 4 was twofold greater than with tau 3 or tau 4L, suggesting that the faster rate of microtubule assembly seen with tau 4 was due, at least in part, to faster elongation. Tau 4 induced a greater number of microtubules to form at steady state than did tau 3 or tau 4L. The microtubules generated with each tau isoform had similar steady-state length distributions and were equally susceptible to cold-induced disassembly. These results indicate that the additional microtubule-binding domain in tau 4 enhances microtubule assembly, while the 58-amino-acid insert negates the stimulatory effect of the fourth microtubule-binding domain.  相似文献   
3.
Focal heavy charged particle irradiation of the rabbit brain created defined lesions which were observable by nuclear magnetic resonance (NMR) and positron emission tomography (PET) imaging techniques. The lesions appeared approximately 9-11 months after left partial hemibrain irradiation with 30 Gy (230 MeV/u helium ions), and were restricted to the white matter tracts and deep perithalamic and thalamic regions. 82Rubidium PET and Gadolinium DTPA enhanced NMR imaging were used to detect blood-brain barrier perturbations. 18Fluordeoxyglucose PET studies demonstrated widespread decreases in cerebral glucose uptake in the cortex and thalamus of the irradiated hemisphere. NMR and PET imaging results correlated well with histological findings. Rabbits irradiated with 15 Gy did not demonstrate any abnormalities in the brain with sequential NMR scans through 14 months post-irradiation.  相似文献   
4.
Expression of tau protein in non-neuronal cells can result in a redistribution of the microtubule cytoskeleton into thick bundles of tau-containing microtubules (Lewis et al.: Nature 342:498-505, 1989; Kanai et al.: J Cell Biol 109:1173-1184, 1989). We reconstituted microtubule bundles using purified tubulin and tau in order to study the assembly of these structures. Taxol-stabilized tubulin polymers were incubated with various concentrations of recombinant human tau and examined by electron microscopy. With increasing concentrations of tau 3 (tau isoform containing three microtubule binding domains) or tau 4 (isoform containing four microtubule binding domains) the microtubules changed orientation from a random distribution to loosely and tightly packed parallel arrays and then to thick cables. In contrast, tau 4L, the tau isoform containing four microtubule binding domains plus a 58-amino acid insert near the N-terminus, showed minimal bundling activity. tau 4-induced bundling could be inhibited by the addition of 0.5 M NaCl or 0.4 mM estramustine phosphate, conditions which are known to inhibit tau binding to microtubules. A tau construct that contained only the microtubule binding domains plus 19 amino acids to the C-terminus was fully capable of bundling microtubules. Phosphorylation of tau 3 with cAMP-dependent protein kinase had no effect on its ability to induce microtubule bundling. These results indicate that tau protein is directly capable of bundling microtubules in vitro, and suggests that different tau isoforms differ in their ability to bundle microtubule filaments.  相似文献   
5.
Previously, we reported that transgenic mice overexpressing endothelin-1 in astrocytes showed more severe neurological deficits and increased infarct after transient focal ischemia. In those studies, we also observed increased level of aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, which has been implicated in osmotic and oxidative stress. To further understand the involvement of the polyol pathway, the mice with deletion of enzymes in the polyol pathway, AR, and sorbitol dehydrogenase (SD), which is the second enzyme in this pathway, were challenged with similar cerebral ischemic injury. Deletion of AR-protected animals from severe neurological deficits and large infarct, whereas similar protection was not observed in mice with SD deficiency. Most interestingly, AR(-/-) brains showed lowered expression of transferrin and transferrin receptor with less iron deposition and nitrotyrosine accumulation. The protection against oxidative stress in AR(-/-) brain was also associated with less poly(adenosine diphosphate-ribose) polymerase (PARP) and caspase-3 activation. Pharmacological inhibition of AR by Fidarestat also protected animals against cerebral ischemic injury. These findings are the first to show that AR contributes to iron- and transferrin-related oxidative stress associated with cerebral ischemic injury, suggesting that inhibition of AR but not SD may have therapeutic potential against cerebral ischemic injury.  相似文献   
6.
Geste antagonistes, or sensory tricks, are well described in focal dystonia affecting the neck, hand, and face. Improvement in dystonic movements is typically maintained while the trick is performed, but disappears when the geste ends. We investigated the phenomenological features of geste antagoniste maneuvers in 19 patients with idiopathic lower cranial dystonia who were prospectively evaluated over a period of 6 years. Of the 19, 10 were men, mean age of onset was 49.8 years, and the most commonly involved lower cranial area was the jaw (10 patients). In most patients, dystonia was task-specific. Taking advantage of the improvement with a sensory geste, we manufactured oral appliances that mimicked the geste in 8 patients, and 3 continue to use it.  相似文献   
7.
Summary 4-amino-1-hydroxybutylidene-1,1-bis-phosphonate (AHButBP) was given intravenously (2.5–25 mg/day for 4 days) to 14 patients with Paget's disease of bone, five of whom had been treated with dichloromethylidene bisphosphonate (Cl2MBP) 32 months earlier. In the nine patients who had not been treated previously with bisphosphonates, the short course of AHButBP induced a suppression of serum alkaline phosphatase and urinary hydroxyproline values down to 30% of initial values. The biochemical suppression of the disease was sustained for 2–18 months and the time to relapse did correlate to the logarithm of the dose (P<0.001). In the five patients previously treated for Paget's disease, an apparent resistence to treatment with AHButBP was observed. However, in these patients both serum alkaline phosphatase and urinary hydroxyproline fell to or even below the nadir values which had previously been achieved with Cl2MBP, irrespective of the degree of relapse. Thus the degree of suppression of Paget's disease of bone, achievable after treatment with bisphosphonates, seems to be constant for each patient, such that normal levels of serum alkaline phosphatase and urinary hydroxyproline cannot usually be attained in patients with extremely active disease.  相似文献   
8.
9.
Fluphenazine decanoate is commonly used as part of maintenance treatment of schizophrenia, but its pharmacokinetics are poorly understood. We administered a single intramuscular dose of fluphenazine decanoate to nine patients and found that plasma fluphenazine level did not decline to 50% of the peak level by day 26 in any of the patients. This means that it has a long half-life measurable in months rather than weeks.  相似文献   
10.
Tumor necrosis factor-alpha (TNFalpha) and Fas are induced after traumatic brain injury (TBI); however, their functional roles are incompletely understood. Using controlled cortical impact (CCI) and mice deficient in TNFalpha, Fas, or both (TNFalpha/Fas-/-), we hypothesized that TNFalpha and Fas receptor mediate secondary TBI in a redundant manner. Compared with wild type (WT), TNFalpha/Fas-/- mice had improved motor performance from 1 to 4 days (P<0.05), improved spatial memory acquisition at 8 to 14 days (P<0.05), and decreased brain lesion size at 2 and 6 weeks after CCI (P<0.05). Protection in TNFalpha/Fas-/- mice from histopathological and motor deficits was reversed by reconstitution with recombinant TNFalpha before CCI, and TNFalpha-/- mice administered anti-Fas ligand antibodies had improved spatial memory acquisition versus similarly treated WT mice (P<0.05). Tumor necrosis factor-alpha/Fas-/- mice had decreased the numbers of cortical cells with plasmalemma damage at 6 h (P<0.05 versus WT), and reduced matrix metalloproteinase-9 activity in injured brain at 48 and 72 h after CCI. In immature mice subjected to CCI, genetic inhibition of TNFalpha and Fas conferred beneficial effects on histopathology and spatial memory acquisition in adulthood (both P<0.05 versus WT), suggesting that the beneficial effects of TNFalpha/Fas inhibition may be permanent. The data suggest that redundant signaling pathways initiated by TNFalpha and Fas play pivotal roles in the pathogenesis of TBI, and that biochemical mechanisms downstream of TNFalpha/Fas may be novel therapeutic targets to limit neurological sequelae in children and adults with severe TBI.  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