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   33448篇
  免费   2339篇
  国内免费   1058篇
耳鼻咽喉   356篇
儿科学   416篇
妇产科学   372篇
基础医学   5171篇
口腔科学   505篇
临床医学   3449篇
内科学   5448篇
皮肤病学   804篇
神经病学   2399篇
特种医学   1606篇
外国民族医学   5篇
外科学   3806篇
综合类   2541篇
现状与发展   7篇
一般理论   9篇
预防医学   1842篇
眼科学   856篇
药学   3461篇
  15篇
中国医学   1070篇
肿瘤学   2707篇
  2024年   62篇
  2023年   413篇
  2022年   1096篇
  2021年   1509篇
  2020年   861篇
  2019年   947篇
  2018年   1075篇
  2017年   857篇
  2016年   1094篇
  2015年   1525篇
  2014年   1839篇
  2013年   1995篇
  2012年   2850篇
  2011年   2945篇
  2010年   1719篇
  2009年   1437篇
  2008年   2002篇
  2007年   1891篇
  2006年   1684篇
  2005年   1589篇
  2004年   1247篇
  2003年   1067篇
  2002年   881篇
  2001年   706篇
  2000年   733篇
  1999年   583篇
  1998年   264篇
  1997年   222篇
  1996年   169篇
  1995年   162篇
  1994年   137篇
  1993年   103篇
  1992年   162篇
  1991年   172篇
  1990年   140篇
  1989年   106篇
  1988年   88篇
  1987年   80篇
  1986年   73篇
  1985年   48篇
  1984年   34篇
  1983年   37篇
  1982年   30篇
  1981年   21篇
  1980年   21篇
  1979年   31篇
  1978年   18篇
  1977年   16篇
  1976年   13篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
81.
基因芯片对PMA激活的血管内皮细胞早期反应基因的研究   总被引:4,自引:1,他引:3  
目的 :用基因芯片研究 PMA激活的血管内皮细胞的早期反应基因 (imm ediate early response gene,ERG)。方法 :以包含 40 96条人类基因的 DNA芯片检测血管内皮细胞受代谢增强剂 PMA(phorbol myristate acetate)激活后早期的基因表达谱 ,并从中筛查出 ERG。结果 :血管内皮细胞受 PMA作用 6 h后 ,17条基因上调 ,11条下调。数据处理聚类分析表明 17条上调基因中多数 (13/ 17)属蛋白质磷酸酶和转录调控因子基因 ,而下调基因中多数 (9/ 11)为细胞分裂相关基因。结论 :证明PMA激活的人血管内皮细胞早期反应基因主要是转录调控因子和蛋白质磷酸酶基因。  相似文献   
82.
中国画的写意造型 ,展示的是似与不似之间、寓意于象、以象尽意“心物统一”的意象。在图形设计中采用写意造型方法 ,能使设计意念的表达更显符号化与象征性 ,同时也丰富观者感受层面与审美经验。  相似文献   
83.
不同地区妇女产褥期卫生行为研究   总被引:22,自引:0,他引:22  
目的 了解江苏、陕西和贵州三省妇女产褥期卫生行为和保健的一般情况;比较 不同地区间产褥期各种卫生行为的发生率;了解影响产褥期卫生行为的相关因素。方法 用问卷调查的形式对三者12个县的2352例2岁以下儿童母亲进行入户访问。结果 江苏、陕西、贵州三者产褥期各卫生行为的发和衣次为:洗头26.4%,38.8%,19.8%, 下身(指外阴部,下同)83.3%,26.9%,64.0%,正常活动76.9%,7  相似文献   
84.
通过用抗CD3,CD28+CD80 McAb激活健康人的PBLs,并以PHA,IL-2,PBLs为对照组;对各组不同时间段的淋巴细胞超微结构进行观察。结果提示:CD3及CD28+CD80刺激淋巴细胞增殖外,也能使淋巴细胞活化,细胞表现为胞体增大,细胞器增多,具有粗大的绒毛和突出伪足,并可见单核细胞吞噬活跃。  相似文献   
85.
From the roasted seeds ofCassia tora L., a new naphthopyrone glycoside was isolated and characterized as 10-[(β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl)oxyl-5-hydroxy-8-methoxy-2-methyl-4H-naphtho [1,2-b]pyran-4-one(isorubrofusarin gentiobioside). Along with isorubrofusarin gentiobioside, alaternin and adenosine were isolated and identified.  相似文献   
86.
Penicillin sensor was prepared by immobilizing penicillinase (Pcase) on H+-selective carboxylated poly (vinyl chloride) (PVC-COOH) membrane or cellulose filter membrane. The immobilization techniques are as follows. Pcase was immobilized with GTH on H+-selective PVC-COOH membrane or some amount of BSA was dropped on that membrane. Another method to make immobilization is to mix type I Pcase with GTH and drop on a cellulose filter membrane. According to immobilization techniques, there were some differences in response properties of enzyme electrodes, however, all electrodes responded to Pcase-resistant penicillin derivatives. Pcase immobilized on cellulose filter membrane with H+-selective PVC membrane eletrode was more stable and more sensitive to penicillinase-resistant penicillin derivatives than any other immobilization techniques.  相似文献   
87.
We determined the microviscosity of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex and liposomes of total lipids (SPMTL) and phospholipids (SPMPL) extracted from SPMV. Changes in the microviscosity induced by the range and rate of lateral diffusion were measured by the intramolecular excimerization of 1,3-di(1-pyrenyl)-propane (Py-3-Py). The microviscosity values of the direct probe environment in SPMV, SPMTL and SPMPL were 38.17, 31.11 and 27.64 cP, respectively, at 37°C and the activation energies (Ea) of the excimer formation of Py-3-Py in SPMV, SPMTL and SPMPL were 8.236, 7.448 amd 7.025 kcal/mol, respectively. Probe location was measured by polarity and polarizability parameters of the probe Py-3-Py and probe analogues, pyrene, 1-pyrenenonanol and 1-pyrenemethyl-3β-hydroxy-22,23-bisnor-5-cholenate (PMC), incorporated into membranes or solubilized in reference solvents. There existed a good linear relationship between the first absorption peak of the1La band and the polarizability parameter (n 2−1)/(2n 2+1). The calculated refractive index values for SPMV, SPMTL and SPMPL were close to 1.50, which is higher than that of liquid paraffin (n=1.475). The probe location was also determined by using a polarity parameter (f−1/2f1). Here f=(ε−1)/(2ε+1) is the dielectric constant function and f'=(n 2−1)/(2n 2+1) is the refractive index function. A correlation existed between the monomer fluorescence intensity ratio and the solvent polarity parameter. The probes incorporated in SPMV, SPMTL, and SPMPL report a polarity value close to that of 1-hexanol (ε=13.29). In conclusion, Py-3-Py is located completely inside the membrane, not in the very hydrophobic core, but displaced toward the polar head groups of phospholipid molecules, e.g., central methylene region of aliphatic chains of phospholipid molecules.  相似文献   
88.
Objective: The objective of this study was to determine whether human papillomavirus (HPV) infections are involved in the development of papillomatosis lesions of the lower female genital tract.Methods: A total of 616 biopsy specimens of genital papillomatous lesions (307 nodular and 309 papular types) from 598 patients were anaylyzed for the presence of HPV DNA sequences by polymerase chain reaction (PCR). These specimens were also examined by histopathological assessment for characteristic HPV-associated cytological changes, by immunohistochemical staining for HPV-associated antigen, and by electron microscopy for the presence of virions.Results: HPV DNA sequences were found in 97.9% (140 of 143 cases) and 1.1% (1 of 91 cases) of the nodular and papular papillomatosis cases tested, respectively. In 18 patients who had both types of papillomatosis lesions, HPV DNA was invariably found only in nodular tissues. HPV-associated antigen, koilocytosis, and virions were found in 53.6% (98 of 183 cases), 70.5% (129 of 183 cases), and 5.9% (5 of 85 cases) of nodular papillomatosis lesions tested, respectively.Conclusions: These data suggest that nodular papillomatosis was closely associated with HPV infection, but that papular papillomatosis of the lower female genital tract may have an etiology other than HPV infection.  相似文献   
89.
90.
Sclerosis is a disease process in which idiopathic hardening occurs in the skin and/or internal organs as a result of the accumulation of type I collagen, induced mainly by transforming growth factor-beta. Colchicine and D-penicillamine are widely used for its treatment. Their effects are known to be due to post-translational down-regulation of type I collagen synthesis, with colchicine also up-regulating interstitial collagenase. To determine whether or not they have any pre-translational effect on type I collagen and MMP-1, and also to observe their effects on the action of TGF-beta, cultured neonatal foreskin fibroblasts were treated with colchicine and D-penicillamine, singly and together. The amount of type I collagen and MMP-1 mRNA were quantitated by Northern blot hybridization. Colchicine suppresses the basal level of type I collagen mRNA but minimally stimulates the mRNA expression of MMP-1, whereas D-penicillamine does not have any significant effects on either. Colchicine was also able to significantly suppress the TGF-beta-induced up-regulation of type I collagen mRNA expression.  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