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   32725篇
  免费   3956篇
  国内免费   585篇
耳鼻咽喉   533篇
儿科学   591篇
妇产科学   525篇
基础医学   6354篇
口腔科学   624篇
临床医学   1962篇
内科学   5384篇
皮肤病学   560篇
神经病学   4961篇
特种医学   602篇
外国民族医学   4篇
外科学   2732篇
综合类   2182篇
现状与发展   2篇
预防医学   1144篇
眼科学   206篇
药学   4712篇
  4篇
中国医学   579篇
肿瘤学   3605篇
  2024年   25篇
  2023年   140篇
  2022年   1299篇
  2021年   1841篇
  2020年   875篇
  2019年   1029篇
  2018年   1038篇
  2017年   1269篇
  2016年   1213篇
  2015年   1914篇
  2014年   1954篇
  2013年   1704篇
  2012年   1882篇
  2011年   1969篇
  2010年   1788篇
  2009年   1504篇
  2008年   1697篇
  2007年   1188篇
  2006年   1116篇
  2005年   1100篇
  2004年   964篇
  2003年   942篇
  2002年   774篇
  2001年   705篇
  2000年   576篇
  1999年   588篇
  1998年   702篇
  1997年   656篇
  1996年   509篇
  1995年   440篇
  1994年   416篇
  1993年   443篇
  1992年   305篇
  1991年   267篇
  1990年   237篇
  1989年   182篇
  1988年   207篇
  1987年   205篇
  1986年   283篇
  1985年   247篇
  1984年   206篇
  1983年   174篇
  1982年   165篇
  1981年   158篇
  1980年   118篇
  1979年   68篇
  1978年   45篇
  1977年   34篇
  1976年   28篇
  1975年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Cytokines including IL-1 beta have been implicated in the pathophysiology of sepsis and the systemic inflammatory response. It is believed that certain critically ill patients may be 'primed' with respect to cytokine production, and that subsequent 'triggers' may cause exaggerated cytokine production in these patients with exacerbation of their clinical condition; however, no means of identifying 'primed' patients has been described. The presence of cytoplasmic IL-1 beta within peripheral blood mononuclear cells (PBMC) from patients in the ICU was investigated as a means of identifying 'primed' patients, using fluorescent antibody labelling and flow cytometry. The study revealed that PBMC from ICU patients had a different staining pattern for IL-1 beta than those from healthy subjects, and that PBMC from certain ICU patients did indeed stain strongly for IL-1 beta; however, the presence of these strongly staining cells was not associated with clinical condition or outcome. It is concluded that whilst it might be possible to identify 'primed' patients in the ICU using this technique, this is of no clinical value as a predictor of clinical course.  相似文献   
53.
Abstract: We analyzed the expression of CEA, CA19-9, CA125, CA15-3 (DF3), PCNA and p53 immunohistochemically in 14 tissue specimens of mucosal cancers in adenoma, seven tubulovillous adenoma specimens, and 16 tubular adenoma specimens. The rates of positive staining for mucosal cancer in adenoma, tubulovillous adenoma and tubular adenoma specimens, respectively, were: for CEA: 100%, 85.7% and 75%; for CA19-9: 71.4%, 71.4% and 56.2%; for CA125:0%, 0% and 0%;for CA15-3 (DF3): 64.3 %, 0% and 0 %; for PCNA: 100%, 88.9% and 56.2%; and for p53: 35.7%, 0% and 0% . The results suggest that the expressions of CEA, CA19-9, CA15-3 (DF3), PCNA and p53 are related to colorectal tumorigenesis. None of the specimens studied showed staining for CA125, suggesting that CA125 is not involved in the early stages of colorectal carcinogenesis. There was no significant difference in the rates of positive staining for CEA and CA19-9 among mucosal cancer in adenoma, tubular adenoma and tubulovillous adenoma specimens. However, the rates of positive staining for PCNA and p53 were significantly higher in mucosal cancer in adenoma specimens than for tubular adenoma specimens (p<0.05), and the rate of CA15-3 (DF3) positive staining was significantly higher for mucosal cancer in adenoma than for tubulovillous adenoma (p<0.01) and tubular adenoma (p< 0.001) specimens. Therefore, the CA15-3 (DF3) antigen is an immunohistochemical marker for colorectal carcinomas. The present results suggest that CA15-3 (DF3), PCNA and p53 play important roles in the genesis of colorectal adenomas.  相似文献   
54.
In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2 – 26 ). The compounds were tested in vitro for inhibition of the three target enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition of P450 18 (bovine adrenal mitochondria), P450 see (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vivo, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre- and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found: 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone ( 4 ) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin ( 12 ) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12 , the 6-OCH3 derivative (compound 11 ) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone ( 13 ) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin ( 17 ) as well as 2-(imidazol-1-ylmethyl)-tetralin ( 16 ) and 7-OCH3-2-imidazol-1-yl-3,4-dihydronaphthalene ( 25 ) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests.  相似文献   
55.
对雄性Wisiaf大鼠腹腔1次注射碘-13l, 注入活度分别为0.59×104Bq,2.37×104Bq, 4.34×104Bq, 8.23×104Bq, 碘-125注入活度分别为3.7×104Bq, 7.4×104Bq, 14.8×104Bq, 22.2×104Bq.碘-131诱发肿痛实际注入活度在2.37×104Bq以下,碘-125的为7.4×104以下.诱发的肿瘤以甲状腺肿瘤为主,其次为垂体肿瘤.  相似文献   
56.
标记抗原在贮存过程中,由于受幅射分解和脱碘影响而使免疫活性和生物活性降低。我们对自制的~(125)碘-绒毛膜促性腺激素进行了实验观察。结果显示:贮存1月后,其免疫活性和生物活性分别降低了33.1%和44.0%;经电泳纯化后的标记物的免疫活性和生物活性明显提高,分别达到了最初的90.5%和95.3%。  相似文献   
57.
Gingival crevicular fluid (GCF) IL-8 and IL-1,1β levels were determined by sandwich enzyme-linked immunosorbent assays. Associations between IL-8 and IL-1β GCF levels, and between these cytokines and patient estrogen status were evaluated. IL-8 and IL-1β were detected more frequently and in higher amounts/30 s GCF sample in estrogen-deficient patients than in estrogensufficient patients. IL-8 and IL-1β GCF levels were significantly correlated. These lindings suggest that GCF IL-8 levels are associated with patient estrogen status and local IL-1β concentrations.  相似文献   
58.
Aim: Rheumatoid arthritis (RA) is the most common chronic inflammatory erosive joint disease with the worldwide distribution of approximately 0.5–1.0%. Etiology of RA is not exactly known but immunologic and genetic factors play an important role in the pathogenesis of the disease. Genetic factors such as human leukocyte antigens (HLA) are responsible for many autoimmune diseases; therefore we decided to look for a correlation between RA and the presence of HLA‐DQβ1 alleles as possible genetic markers. Methods: Genomic DNA from the whole blood samples of 25 patients with RA and 86 normal individuals as control group were extracted by salting out method. The genomic DNA was amplified by polymerase chain reaction‐sequence specific primer (PCR‐SSP) technique. HLA‐typing was done by this method after optimizing the PCR reaction for each allele. In this procedure seven serological subclasses of HLA‐DQβ1 can be detected. Results: Comparing the results between the patients and controls show a significant increase in the frequency of HLA‐DQ8 (*0302, *0305) alleles in RA patients. The P‐values were 0.007 and the relative risk for these alleles was evaluated higher than 1. Conclusions: The results suggest that DQ8 is the dominant HLA‐DQβ1 allele that is associated with susceptibility to RA in north‐eastern Iran.  相似文献   
59.
目的探讨CD11b在肺纤维化患者外周血中性粒细胞上的表达及红霉素对它的影响.方法肺纤维化患者(A组,n=13)13例经红霉素治疗3个月,收集治疗前后及健康对照组(B组,n=13)13例的外周血中性粒细胞涂片,用桥联酶免疫法测定CD11b表达阳性的中性粒细胞百分率.结果A组治疗前后,患者外周血中性粒细胞CD11b的表达阳性率均显著高于健康对照组(P<0.01);A组治疗前,患者外周血中性粒细胞CD11b的表达阳性率显著高于治疗后(P<0.01).结论肺纤维化患者外周血中性粒细胞CD11b的表达阳性率显著高于健康对照组;红霉素能抑制肺纤维化患者外用血中性粒细胞CD11b的表达.  相似文献   
60.
SK&F 86466, 6-chloro-3-methyl-2,3,4,5-tetrahydro-1-H-3-benzazepine, is a potent and selective antagonist of the α2-adrenoceptor in vitro. This compound produced a small pressor response accompanied by a marked bradycardia when administered i.v. to the pithed normotensive rat. The pressor response was not affected by reserpine treatment, pretreatment with α- or β-adrenoceptor antagonists, atropine, or hexamethonium. The bradycardia was markedly reduced by bilateral vagotomy and pretreatment with atropine and attenuated by hexamethonium. The negative chronotropic action of SK&F 86466 was abolished by a combination of vagotomy and atropine. Mediation of the bradycardia by a baroreceptor reflex was ruled out by the observations that a lack of change in heart rate was associated with the vasopressor response to phenylephrine in the pithed rat pretreated with propranolol. It is concluded that the negative chronotropic action of SK&F 86466 in the pithed rat is mediated indirectly by activation of the cholinergic innervation of the heart.  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