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   31607篇
  免费   3125篇
  国内免费   2215篇
耳鼻咽喉   264篇
儿科学   428篇
妇产科学   396篇
基础医学   3585篇
口腔科学   554篇
临床医学   4318篇
内科学   4586篇
皮肤病学   277篇
神经病学   1499篇
特种医学   1329篇
外国民族医学   13篇
外科学   3505篇
综合类   5385篇
现状与发展   9篇
一般理论   3篇
预防医学   2028篇
眼科学   707篇
药学   3434篇
  31篇
中国医学   1843篇
肿瘤学   2753篇
  2024年   77篇
  2023年   456篇
  2022年   869篇
  2021年   1567篇
  2020年   1190篇
  2019年   1044篇
  2018年   1072篇
  2017年   1052篇
  2016年   1035篇
  2015年   1474篇
  2014年   1802篇
  2013年   1640篇
  2012年   2139篇
  2011年   2507篇
  2010年   1635篇
  2009年   1283篇
  2008年   1625篇
  2007年   1709篇
  2006年   1659篇
  2005年   1560篇
  2004年   1181篇
  2003年   1193篇
  2002年   1073篇
  2001年   894篇
  2000年   818篇
  1999年   777篇
  1998年   444篇
  1997年   511篇
  1996年   342篇
  1995年   302篇
  1994年   238篇
  1993年   190篇
  1992年   230篇
  1991年   212篇
  1990年   183篇
  1989年   167篇
  1988年   133篇
  1987年   134篇
  1986年   115篇
  1985年   76篇
  1984年   50篇
  1983年   28篇
  1982年   16篇
  1981年   17篇
  1980年   25篇
  1979年   45篇
  1978年   22篇
  1975年   17篇
  1974年   20篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
石景亮教授治疗多囊卵巢综合征的经验   总被引:3,自引:0,他引:3  
石景亮(1939-),国家级第二批名老中医.业医三十余载,学验俱丰,对内科的脾胃病、肾病及妇科疑难杂症的治疗积累了丰富的经验.现就石老师治疗多囊卵巢综合征的经验介绍如下.  相似文献   
42.
43.
c-myc is required for osteoclast differentiation.   总被引:1,自引:0,他引:1  
The role of the receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL)-a tumor necrosis factor (TNF)-related cytokine-in osteoclast formation has been established clearly. However, the downstream signaling pathways activated by this cytokine remain largely unknown. To identify genes that play a role in osteoclastogenesis, we used RAW 264.7 mouse monocytes as a model system for the differentiation of multinucleated osteoclasts from mononucleated precursors. RAW 264.7 cells were induced with RANKL to form multinucleated giant osteoclast-like cells (OCLs) that expressed a number of osteoclast-specific markers and were able to form resorption pits on both calcium phosphate films and bone slices. This system was used to identify genes that are regulated by RANKL and may play a role in osteoclast differentiation. The proto-oncogene c-myc was strongly up-regulated in RANKL-induced OCLs but was absent in undifferentiated cells. Expression of Myc partners Max and Mad, on the other hand, was constant during OCL differentiation. We expressed a dominant negative Myc in RAW 264.7 cells and were able to block RANKL-induced OCL formation. Northern Blot analysis revealed a delay and a significant reduction in the level of messenger RNA (mRNA) for tartrate-resistant acid phosphatase (TRAP) and cathepsin K. We conclude that c-myc is a downstream target of RANKL and its expression is required for RANKL-induced osteoclastogenesis.  相似文献   
44.
Serine hydroxymethyltransferase (SHMT) provides activated one-carbon units required for the biosynthesis of nucleotides, protein, and methyl group by converting serine and tetrahydrofolate to glycine and N(5),N(10)-methylenetetrahydrofolate. It is postulated that SHMT activity is associated with the development of methotrexate resistance and the in vivo activity of SHMT is regulated by the binding of N(5)-CHO-THF, the rescue agent in high-dose methotrexate chemotherapy. The aim of this study is to advance our understanding of the folate-mediated one-carbon metabolism in zebrafish by characterizing zebrafish mitochondrial SHMT. The cDNA encoding zebrafish mitochondrial SHMT was cloned, overexpressed in Escherichia coli, and purified with a three-step purification protocol. Similarities in structural, physical, and kinetic properties were revealed between the recombinant zebrafish mitochondrial SHMT and its mammalian orthologs. Surprisingly, leucovorin significantly inhibits the aldol cleavage of serine catalyzed by zebrafish cytosolic SHMT but inhibits to a lesser extent the reaction catalyzed by the mitochondrial isozyme. This is, to our knowledge, the first report on zebrafish mitochondrial folate enzyme as well as the differential inhibition of leucovorin on these two SHMT isoforms. Western blot analysis revealed tissue-specific distribution with the highest enrichment present in liver for both cytosolic and mitochondrial SHMTs. Intracellular localization was confirmed by confocal microscopy for both mitochondrial and cytosolic SHMTs. Unexpectedly, the cytosolic isoform was observed in both nucleus and cytosol. Together with the previous report on zebrafish cytosolic SHMT, we suggest that zSHMTs can be used in in vitro assays for folate-related investigation and antifolate drug discovery.  相似文献   
45.
Changes in T .lymphocyte subsets after severe traumatic brain inJury   总被引:2,自引:0,他引:2  
BACKGROUND: Besides local changes of cranial parenchymal cells, hemorrhage, etc., severe traumatic brain injuries also cause the changes of total body fluid and various functions, and the changes of lymphocytes and T lymphocyte subsets should be paid more attention to. OBJECTIVE: To reveal the changing laws of T lymphocyte subsets after severe traumatic brain injury, and compare with mild to moderate brain injury. DESIGN: A comparative observation. SETTINGS: Department of Neurosurgery, Longgang District Buji People's Hospital of Shenzhen City; Central Laboratory of Shenzhen Hospital of Prevention and Cure for Chronic Disease. PARTICIPANTS: All the subjects were selected from the Department of Neurosurgery, Longgang District Buji People's Hospital of Shenzhen City from August 2002 to August 2005. Thirty patients with severe brain injury, whose Glasgow coma score (GCS) was ≤ 8 points, were taken as the experimental group, including 21 males and 9 females, aging 16 - 62 years. Meanwhile, 30 patients with mild traumatic brain injury were taken as the control group (GCS ranged 14- 15 points), including 18 males and 12 females, aging 15 -58 years. All the subjects were in admission at 6 hours after injury, without disease of major organs before injury Informed consents were obtained from all the patients or their relatives. METHODS: (1) The T lymphocytes and the subsets in peripheral blood were detected with immunofluorescent tricolor flow cytometry at l, 3, 7 and 14 days after injury in both groups. (2) The conditions of pulmonary infections were observed at 4 days after injury. The differences of measurement data were compared with the t test. MAIN OUTCOME MEASURES: Changes of T lymphocytes subsets at 1 - 14 days after severe and mild or moderate traumatic injury. RESULTS: Finally, 28 and 25 patients with mild to moderate traumatic brain injury, whereas 25 and 21 patients with severe traumatic brain injury were analyzed at 7 and 14 days respectively, and the missed ones died due to the development of disease. (1) Changes of T lymphocyte subsets: At 1 and 3 days after injury, CD3, CD4, CD8, CD4/CD8 began to decrease, whereas CD8 increased in the experimental group, which were very significantly different from those in the control group (t =2.77 - 3.26, P 〈 0.01), and began to recover at 7 days, which were significantly different from those in the control group (t = 2.06 - 2.24, P 〈 0.05), and generally recovered to the normal levels at 14 days (P 〉 0.05). (2) Conditions of pulmonary infections: At 4 days after injury, the rate of pulmonary infection was significantly different between the experimental group and control group [73% (22/30), 0, x2=37.29, P 〈 0.01]. CONCLUSION: Patients with severe traumatic brain injury suffer from damages of cellular immune function at early period (within 7 days), and they are easily to be accompanied by pulmonary infections.  相似文献   
46.
以钒基核苷酸复合物为核酸酶抑制剂,从人胚组织中制备总RNA,所得产品几乎不含DNA和蛋白质,经过分离Poly(A)~ mRNA,证明制品有合成cDNA的完整功能,方法比较简捷,适于大量制备以满足分离mRNA 之需,并讨论了此法的优缺点。  相似文献   
47.
Monoclonal antibody 131I-COC183B2, developed in our laboratory and proved to fit for human treatment was injected intraperitoneally or subcutaneously in 13 patients. In 8 cases with i.p. injection the disease corresponded with the image, i.e. 3 primary ovarian epithelial cancers showed positive images, 1 ovarian Krukenberg tumor was negative and the other 4 negative images included 1 uterine myoma and 3 ovarian teratomas. In the subcutaneous injection group, 4 cases had ovarian carcinoma, surgery and chemotherapy. Two negative images corresponded with the clinical status-in good health, another negative case had metastatic left supraclavicular lymph node due to ovarian mucinous adenocarcinoma. The last negative image in this group was a case of benign ovarian teratoma which was proved after surgery. The 1 positive case was waiting to be proved by a scheduled third operation. The computer scintigram calculation of T/NT was 5.35 to 13.7. The results suggest that this monoclonal antibody can be used for radioimmunoimaging for the localization of ovarian carcinoma, which is not only helpful for clinical staging and differential diagnosis but is also a good follow-up method.
  相似文献   
48.
p16INK4A (p16) binds to cyclin-dependent kinase 4/6 and negatively regulates cell growth. Recent studies have led to an understanding of additional biologic functions for p16; however, the detailed mechanisms involved are still elusive. In this article, we show an unexpected expression of anion exchanger 1 (AE1) in the cytoplasm in poorly and moderately differentiated gastric and colonic adenocarcinoma cells and in its interaction with p16, thereby sequestrating the protein in the cytoplasm. Genetic alterations of p16 and AE1 were not detectable. Forced expression of AE1 in these cells sequestrated more p16 in the cytoplasm, whereas small interfering RNA-mediated silencing of AE1 in the cells induced the release of p16 from the cytoplasm to the nucleus, leading to cell death and growth inhibition of tumor cells. By analyzing tissue samples obtained from patients with gastric and colonic cancers, we found that 83.33% of gastric cancers and 56.52% of colonic cancers coexpressed AE1 and p16 in the cytoplasm. We conclude that AE1 plays a crucial role in the pathogenesis of gastric and colonic adenocarcinoma and that p16 dysfunction is a novel pathway of carcinogenesis.  相似文献   
49.
创伤性浮膝伴血管损伤的早期诊治   总被引:3,自引:0,他引:3  
目的 探讨创伤性浮膝同时伴同侧血管损伤患者的早期诊断及救治.方法 总结1996年6月~2002年12月收治28例30个浮膝的手术固定方法、血管修复情况及术后治疗和恢复情况.结果 术后伤口一期愈合5例,17例伤口二期行植皮修复,4例胫前骨折部外露二期行皮瓣转移术,截肢2例,保肢成功率92.9%.术后26例经18个月~8年随访,骨折均愈合,下肢功能恢复优良率64.3%.结论 对浮膝损伤患者应高度重视伴有血管损伤可能,早期作出诊断,积极合理治疗,对患者预后至关重要.  相似文献   
50.
目的:获得较高比例的已分化表皮细胞,为表皮细胞去分化研究奠定基础.方法:采用常规表皮细胞培养方法对人表皮角质细胞系(HEK)进行培养和传代.每一代细胞均通过免疫细胞化学染色和Western blot 方法进行表皮干细胞和表皮细胞相应标志物的检测,包括β1整合素、角蛋白19(K19)、角蛋白10(K10)等指标.结果:第1代HEK呈克隆样生长,表皮干细胞标志物β1整合素、K19均有高表达,而K10的表达为阴性.经过数次传代,细胞克隆形成数目减少,细胞逐渐呈分散分布,K10的表达逐渐增高,而β1整合素、K19的表达呈下降趋势,比例减少.细胞培养至第5~6代时,为其生长的一个转折点,即此时细胞增殖能力开始明显降低,但形态良好,K10表达阳性细胞比例明显增高,而β1整合素、K19表达阳性细胞比例迅速降低.细胞培养至10~11代时,为其生长的第二个转折点,此时细胞几乎丧失增殖能力,数量显著减少,体积变大,核浆比明显减小,完全见不到β1整合素、K19表达阳性细胞,K10染色均为阳性.结论:可以选取适当代数的HEK用于去分化研究,为增加HEK的新用途提供了实验基础.  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