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   24324篇
  免费   1267篇
  国内免费   132篇
耳鼻咽喉   262篇
儿科学   322篇
妇产科学   329篇
基础医学   3246篇
口腔科学   766篇
临床医学   1668篇
内科学   6335篇
皮肤病学   382篇
神经病学   1458篇
特种医学   760篇
外科学   3968篇
综合类   123篇
一般理论   1篇
预防医学   836篇
眼科学   576篇
药学   1654篇
中国医学   66篇
肿瘤学   2971篇
  2023年   108篇
  2022年   227篇
  2021年   409篇
  2020年   236篇
  2019年   308篇
  2018年   431篇
  2017年   320篇
  2016年   413篇
  2015年   409篇
  2014年   537篇
  2013年   654篇
  2012年   997篇
  2011年   1152篇
  2010年   626篇
  2009年   529篇
  2008年   955篇
  2007年   1080篇
  2006年   1044篇
  2005年   1084篇
  2004年   1027篇
  2003年   1076篇
  2002年   970篇
  2001年   889篇
  2000年   906篇
  1999年   865篇
  1998年   291篇
  1997年   236篇
  1996年   250篇
  1995年   203篇
  1994年   177篇
  1993年   162篇
  1992年   684篇
  1991年   617篇
  1990年   570篇
  1989年   649篇
  1988年   553篇
  1987年   508篇
  1986年   517篇
  1985年   473篇
  1984年   304篇
  1983年   234篇
  1982年   132篇
  1981年   100篇
  1980年   108篇
  1979年   219篇
  1978年   171篇
  1977年   135篇
  1974年   109篇
  1971年   119篇
  1969年   126篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Purpose:It has been reported previously that intravenously administered gadolinium-based contrast agent (GBCA) leaks into the subarachnoid space around the cortical veins at 4 h after injection in all old people over 37 years, but not in younger people up to 37 years of age in 3D-real IR images. The purpose of this study was to investigate whether there was a strict threshold of 37 years of age for the leakage of the GBCA into the subarachnoid space.Methods:The subjects included 190 patients, that were scanned for 3D-real IR images at 4 hours after intravenous injection of GBCA as a diagnostic test for endolymphatic hydrops. The patient’s age ranged from 14 to 81 years. Two experienced neuroradiologists evaluated the images to determine whether the GBCA leakage around the cortical veins was positive or negative. Any discrepancies between the two observers were discussed and a consensus was obtained.A Mann–Whitney U test and receiver operating characteristic (ROC) curve analysis were used to compare the positive and the negative group and to set the age cut-off value for the prediction of GBCA leakage.Results:The GBCA leakage around the cortical veins was negative in 35 patients and positive in 155 patients. The average age was 33 ± 11 years in the negative group, and 55 ± 12 years in the positive group (P < 0.01). In the ROC analysis for the age and leakage of the GBCA, an area under the curve was 0.905 and the cut-off age was 37.317 years (sensitivity of 0.942 and specificity of 0.771).Conclusion:Intravenously administered GBCA leaks into the subarachnoid space around the cortical veins in most patients over 37 years of age. However, it should be noted that it can be found occasionally in patients under 37 years of age.  相似文献   
5.
Angiotensin II receptor blockers (ARBs) are widely used for the treatment of hypertension. It is believed that treatment with an ARB increases the level of plasma angiotensin II (Ang II) because of a lack of negative feedback on renin activity. However, Ichikawa (Hypertens Res 2001; 24: 641-646) reported that long-term treatment of hypertensive patients with olmesartan resulted in a reduction in plasma Ang II level, though the mechanism was not determined. It has been reported that angiotensin 1-7 (Ang-(1-7)) potentiates the effect of bradykinin and acts as an angiotensin-converting enzyme (ACE) inhibitor. It is known that ACE2, which was discovered as a novel ACE-related carboxypeptidase in 2000, hydrolyzes Ang I to Ang-(1-9) and also Ang II to Ang-(1-7). It has recently been reported that olmesartan increases plasma Ang-(1-7) through an increase in ACE2 expression in rats with myocardial infarction. We hypothesized that over-expression of ACE2 may be related to a reduction in Ang II level and the cardioprotective effect of olmesartan. Administration of 0.5 mg/kg/day of olmesartan for 4 weeks to 12-week-old stroke-prone spontaneously hypertensive rats (SHRSP) significantly reduced blood pressure and left ventricular weight compared to those in SHRSP given a vehicle. Co-administration of olmesartan and (D-Ala7)-Ang-(1-7), a selective Ang-(1-7) antagonist, partially inhibited the effect of olmesartan on blood pressure and left ventricular weight. Interestingly, co-administration of (D-Ala7)-Ang-(1-7) with olmesartan significantly increased the plasma Ang II level (453.2+/-113.8 pg/ml) compared to olmesartan alone (144.9+/-27.0 pg/ml, p<0.05). Moreover, olmesartan significantly increased the cardiac ACE2 expression level compared to that in Wistar Kyoto rats and SHRSP treated with a vehicle. Olmesartan significantly improved cardiovascular remodeling and cardiac nitrite/ nitrate content, but co-administration of olmesartan and (D-Ala7)-Ang-(1-7) partially reversed this anti-remodeling effect and the increase in nitrite/nitrate. These findings suggest that olmesartan may exhibit an ACE inhibitory action in addition to an Ang II receptor blocking action, prevent an increase in Ang II level, and protect cardiovascular remodeling through an increase in cardiac nitric oxide production and endogenous Ang-(1-7) via over-expression of ACE2.  相似文献   
6.
7.
The direct causal relationship between dermatomyositis-polymyositis (PM) and malignancy remains controversial. We describe herein the case of a patient who underwent surgical treatment for colon cancer, which had preceded the onset of PM with tumor relapse. The PM markedly improved following the initiation of steroid therapy, and has remained under control, probably as a result of chemotherapy. The current concepts of variable clinical courses and the possible mechanism for the association of PM with malignancy are discussed following this case report.  相似文献   
8.
We evaluated the therapeutic efficacy of miconazole (MCZ, Florid-F inj.), a new antifungal agent for parenteral use, in deep-seated fungal infections of respiratory tract system. A daily dose of 400-1,800 mg of MCZ was given intravenously for 12-38 days (mean: 23.4 days) to 7 patients: 2 patients with pulmonary aspergillosis, 1 patient with bronchial aspergillosis, 1 patient with pulmonary candidiasis and 3 patients with candidemia. One additional patient with pulmonary aspergillosis received three instillations of 20 mg of MCZ into the thoracic cavity. The clinical effects were excellent in 1, good in 4 and poor in 3 patients. The efficacy rate was 100% in 5 cases with respiratory fungal infections but 3 cases with candidemia did not respond well to the treatment. Four strains each of Aspergillus sp. and Candida sp. were identified as causative organisms. Seven of the 8 strains were eradicated by administration of MCZ. Side effects observed were irritation and heat in a leg in 1 patient, hyperlipoidemia in 2 patients and eosinophilia in 1 patient. The adverse reactions disappeared after the completion of the therapy. From the above results, we conclude that MCZ is one of the most useful antifungal agents for parenteral use as a first choice on deep-seated fungal infections in the respiratory tract.  相似文献   
9.
Although the human tumor clonogenic assay (HTCA) is extremely reliable in determining clinical correlations, it is a complicated process requiring considerable time in order to obtain results. Thus, an experimental study on cytopathologic observation (cytologic assay) and comparative evaluation between it and HTCA were performed in order to establish a more rapid and accurate drug sensitivity test. Materials included Colon 26, a cell line established in our department, malignant effusion and surgical specimens. In carrying out HTCA according to the Hamburger-Salmon method, the cell suspension samples following exposure to anti-tumor agents (MMC, L-PAM, ADM, CDDP) were cultivated in test tubes for 3-8 hours and stained by the Papanicolaou and Giemsa methods. According to Tokita's criteria, when cellular changes showed as nuclear pyknosis and nuclear destruction were found to have increased significantly in comparison with a control group, the cells were judged to be sensitive. Very similar and parallel results were obtained between HTCA and cytologic assay in this study, with a significant correlation. Cytologic assay was proved to be an easy, rapid and accurate method for testing drug sensitivity and its clinical application can be expected in the future.  相似文献   
10.
We examined the mechanisms of the inhibition of DNA synthesis by a new platinum compound, (-)-( R )-2-aminomethylpyrrolidine(1,1-cyclobutane-dicarboxylato)-2-platinum(II) monohydrate (DWA-2114R), a derivative of the antitumor drug cis- diamminedichloroplatinum(II) (CDDP), using prokaryotic and eukaryotic DNA polymerases. Preincubating activated DNA with CDDP or DWA-2114R reduced its template activity for prokaryotic and eukaryotic DNA polymerases in a dose-dependent manner. DWA2114R required six times greater drug concentration and two times longer incubation time to show the same decrease of the template activity compared to CDDP. Treatment of primed pUC118 ssDNA templates with the two drugs followed by second-strand synthesis by prokaryotic and eukaryotic DNA polymerases revealed that DWA2114R bound to DNA in a similar manner to CDDP and these adducts blocked DNA elongation by DNA polymerases of eukaryotes as well as of prokaryotes. With these two drugs, the elongations by E. coli DNA polymerase I (Klenow fragment), T7 DNA polymerase and calf thymus DNA polymerase α were strongly arrested at guanine-guanine sequences (GG). Stop bands were also observed at adenine-guanine sequences (AG) guanine-adenine-guanine sequences (GAG) and mono-guanine sequence (G). Calf testis DNA polymerase β was also arrested efficiently at AG, GAG and G, but much more weakly at GG. This pattern was common to DWA2114R and CDDP.  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