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   76060篇
  免费   7368篇
  国内免费   5718篇
耳鼻咽喉   558篇
儿科学   851篇
妇产科学   580篇
基础医学   7730篇
口腔科学   1231篇
临床医学   9534篇
内科学   10122篇
皮肤病学   601篇
神经病学   3727篇
特种医学   3151篇
外国民族医学   39篇
外科学   8153篇
综合类   15658篇
现状与发展   14篇
一般理论   16篇
预防医学   6084篇
眼科学   1563篇
药学   8503篇
  82篇
中国医学   5041篇
肿瘤学   5908篇
  2024年   287篇
  2023年   1090篇
  2022年   2811篇
  2021年   3484篇
  2020年   2857篇
  2019年   2245篇
  2018年   2414篇
  2017年   2345篇
  2016年   2123篇
  2015年   3514篇
  2014年   4374篇
  2013年   4371篇
  2012年   6407篇
  2011年   7137篇
  2010年   5033篇
  2009年   4240篇
  2008年   4682篇
  2007年   4659篇
  2006年   4360篇
  2005年   3966篇
  2004年   2778篇
  2003年   2462篇
  2002年   2109篇
  2001年   1629篇
  2000年   1463篇
  1999年   1155篇
  1998年   811篇
  1997年   775篇
  1996年   615篇
  1995年   540篇
  1994年   402篇
  1993年   306篇
  1992年   251篇
  1991年   203篇
  1990年   204篇
  1989年   213篇
  1988年   170篇
  1987年   150篇
  1986年   117篇
  1985年   110篇
  1984年   57篇
  1983年   43篇
  1982年   37篇
  1981年   30篇
  1980年   22篇
  1979年   19篇
  1978年   13篇
  1977年   14篇
  1976年   9篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Gemins modulate the expression and activity of the SMN complex   总被引:1,自引:0,他引:1  
Reduction in the expression of the survival of motor neurons (SMN) protein results in spinal muscular atrophy (SMA), a common motor neuron degenerative disease. SMN is part of a large macromolecular complex (the SMN complex) that includes at least six additional proteins called Gemins (Gemin2-7). The SMN complex is expressed in all cells and is present throughout the cytoplasm and in the nucleus where it is concentrated in Gems. The SMN complex plays an essential role in the production of spliceosomal small nuclear ribonucleoproteins (snRNPs) and likely other RNPs. To study the roles of the individual proteins, we systematically reduced the expression of SMN and each of the Gemins (2-6) by RNA interference. We show that the reduction of SMN leads to a decrease in snRNP assembly, the disappearance of Gems, and to a drastic reduction in the amounts of several Gemins. Moreover, reduction of Gemin2 or Gemin6 strongly decreases the activity of the SMN complex. These findings demonstrate that other components of the SMN complex, in addition to SMN, are critical for the activity of the complex and suggest that Gemin2 and Gemin6 are potentially important modifiers of SMA as well as potential disease genes for non-SMN motor neuron diseases.  相似文献   
62.
肢端黏液样炎性纤维母细胞肉瘤2例及文献复习   总被引:1,自引:2,他引:1  
目的探讨肢端黏液样炎性纤维母细胞肉瘤的临床病理学特征及鉴别诊断。方法对2例发生在下肢末端的黏液样炎性纤维母细胞肉瘤进行光镜观察和免疫组化标记,并复习文献。结果2例发生在下肢末端的病程较长的渐进性肿块,术后局部复发。镜检:病变呈多结节状,边界不清;黏液样基质中见数量不等的各类炎细胞浸润,散在或灶性分布梭形、奇异形和多空泡状脂肪母细胞样3种形态的瘤细胞。免疫表型:肿瘤细胞Vim弥漫阳性,CD68和CD34灶性阳性,CK、SMA、HHF-35、S-100蛋白、CD45、CD45R0、CD15、CD30均阴性。结论此病病程较长,术后易局部复发,是一种低度恶性的肿瘤。鉴于病变黏液样基质及各类炎细胞浸润的背景较为突出,而特征性的瘤细胞稀疏,应注意与炎症性病变或具有相似组织形态的良性或恶性肿瘤鉴别。  相似文献   
63.
Sperm quality in Hodgkin's disease versus non-Hodgkin's lymphoma   总被引:3,自引:4,他引:3  
The study was conducted to determine the deleterious effect of lymphoma disease on spermatogenesis and to evaluate the possibility that the disease is mediated primarily by inherent mechanisms in Hodgkin's disease and non-Hodgkin's lymphoma patients. A total of 89 patients with lymphoma disease (Hodgkin's and non-Hodgkin's) were referred for sperm preservation prior to adjuvant treatments. A comparison was made of pre- and post-thaw sperm quality between lymphoma patients and healthy volunteers who applied for sperm donation. This was followed by further assessment of the differences between patients with Hodgkin's disease and non-Hodgkin's lymphoma in terms of sperm variables, clinical parameters and blood hormone concentrations. It was found that patients with lymphoma disease had significantly impaired pre-freeze and post-thaw sperm quality compared with that of healthy volunteers. Patients with non-Hodgkin's lymphoma had spermatozoa of higher quality than patients with Hodgkin's disease. No differences were found in the clinical or hormonal parameters between these two groups. As expected, reduced testicular size and abnormal testicular consistency were correlated with decreased sperm quality. The mere presence of cancer disease has a direct negative effect on spermatogenesis, which is probably not related to incidental side-effects. A variable degree of impairment should be expected with different categories of cancer.   相似文献   
64.
Gene therapy is defined as the introduction of a therapeutic gene into a cell, whose expression can lead to a cure of a disease or offer a transient advantage for tissue growth and regeneration. The delivery of genes can be undertaken for a number of purposes, usually it is attempted to enhance or add a function to a cell or a tissue or to delete or reduce another function. In this brief overview we describe various vehicles and techniques that have been developed to deliver therapeutic genes into cells, such as viral vectors and physical/chemical gene delivery methods including naked DNA and particle-mediated gene transfer, the microseeding technique and the application of lipids. Furthermore we review the potential utility of gene therapy from the perspective of a reconstructive surgeon. Several tissues will be discussed, particularly muscle, tendon, nerve, bone, skin and wounds.  相似文献   
65.
淋巴结血管内T细胞淋巴瘤1例报道及文献复习   总被引:1,自引:0,他引:1  
目的 探讨血管内淋巴瘤 (IVL)的临床病理特征。方法 对 1例腹股沟淋巴结IVL临床、病理组织学及免疫表型进行观察分析并复习文献。结果 男性 31岁 ,不明原因高热伴消瘦 5 0天 ,右腹股沟直径 1cm淋巴结 1枚 ,B超示肝脏轻度增大 ,血LDH明显升高伴ESR及转氨酶轻度升高 ,外周血WBC 3 3× 10 7/L ,骨髓像、多种病原及各肿瘤相关抗原检测均无异常。病理活检 :腹股沟淋巴结大部分破坏 ,代之以大量扩张的中小血管 ,腔内充满大量异型淋巴样细胞 ,局部伴管壁、管周浸润并累及结外脂肪组织。瘤细胞免疫表型CD4 5、CD4 5RO、CD3阳性 ,CK、CD6 8、CD79α、CD2 0均阴性 ,血管壁及内皮细胞CD31、CD34阳性。行CHOP化疗后症状缓解 ,现仍在随访中。结论 IVL是一罕见的非霍奇金淋巴瘤 ,好发于中枢神经系统及皮肤 ,其他部位少见 ,绝大数为B细胞型 ,T型罕见 ,以浅表淋巴结活检确诊者尚无报道。临床表现有一定提示性 ,确诊靠组织病理学检查 ,部分病例对化疗敏感 ,但多数病例预后差  相似文献   
66.
Using functional magnetic resonance imaging (fMRI), we explored the binocular interactions occurring when subjects viewed dichoptically presented checkerboard stimuli. A flickering radial checkerboard was presented to each eye of the subject, while T2*-weighted images were acquired over the visual cortex with gradient-echo, echoplanar sequences. We compared responses in striate and extrastriate visual cortex under four conditions: both eyes were stimulated at the same time (binocular condition), each eye was stimulated in alternation (monocular condition) or first the one eye then the other eye was stimulated (left eye first - right eye trailing, or vice versa). The results indicate that only the striate area, in and near the calcarine fissure, shows significant differences for these stimulation conditions. These differences are not evident in more remote extrastriate or associational visual areas, although the BOLD response in the stimulation-rest comparison was robust. These results suggest that the effect could be related to inhibitory interactions across ocular dominance columns in striate visual cortex.  相似文献   
67.
Using the rigid and hydrophobic polystyrene (PS) chain as backbone, onto which flexible and hydrophilic stearyl-poly(ethylene oxide) (SPEO) chains are grafted, a new kind of amphiphilic, microphase-separated graft copolymer was synthesized using the macromonomer technique. Stearyl-poly(ethylene oxide) macromonomers with acryloyl end-group (SPEO-A) were prepared through an end-group exchange reaction of α-stearyl-ω-hydroxypoly(ethylene oxide) (SPEO-OH) and acryloyl chloride in the presence of triethylamine. The radical copolymerization of styrene with SPEO-A was carried out under various experimental conditions. Following a careful examination of their purity, the structure of the prepared copolymers was characterized by means of IR, 1H NMR and GPC analyses. A new feasible method using first derivative UV spectrometry was developed for quantitative determination of the bulk composition of the graft copolymers. Copolymers with a wide range of bulk composition and satisfactory grafting degree were obtained.  相似文献   
68.
69.
70.
女贞子、刺五加对T细胞促进作用的实验研究   总被引:11,自引:0,他引:11  
女贞子和刺五加都是扶正中药.女贞子在体内体外对 T 细胞均有促进作用,但对其作用机理报导很少。刺五加是典型的“适应原样”药物,对机体免疫功能亦有促进作用,但其对 T 细胞的作用尚未见报导.  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