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   13623篇
  免费   675篇
  国内免费   47篇
耳鼻咽喉   217篇
儿科学   253篇
妇产科学   129篇
基础医学   1646篇
口腔科学   387篇
临床医学   784篇
内科学   3519篇
皮肤病学   459篇
神经病学   872篇
特种医学   578篇
外科学   2556篇
综合类   44篇
一般理论   3篇
预防医学   344篇
眼科学   143篇
药学   816篇
中国医学   13篇
肿瘤学   1582篇
  2023年   60篇
  2021年   226篇
  2020年   141篇
  2019年   192篇
  2018年   212篇
  2017年   169篇
  2016年   189篇
  2015年   196篇
  2014年   257篇
  2013年   335篇
  2012年   577篇
  2011年   604篇
  2010年   343篇
  2009年   322篇
  2008年   581篇
  2007年   641篇
  2006年   600篇
  2005年   636篇
  2004年   582篇
  2003年   620篇
  2002年   548篇
  2001年   564篇
  2000年   552篇
  1999年   483篇
  1998年   156篇
  1997年   157篇
  1996年   137篇
  1995年   109篇
  1994年   107篇
  1993年   91篇
  1992年   359篇
  1991年   332篇
  1990年   308篇
  1989年   322篇
  1988年   290篇
  1987年   300篇
  1986年   268篇
  1985年   292篇
  1984年   171篇
  1983年   155篇
  1982年   75篇
  1981年   63篇
  1979年   135篇
  1978年   68篇
  1976年   59篇
  1975年   64篇
  1974年   72篇
  1973年   85篇
  1972年   63篇
  1971年   59篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
101.
We performed human leukocyte antigens(HLA)typing for class I antigens on 19 Japanese patients with Fisher's syndrome. We demonstrated a statistically significant association between the disease and the HLA-B39 antigen.  相似文献   
102.
The accumulation of oxygen free radicals is reported to occur in the organs subjected to temporary ischemia followed by reperfusion, resulting in the fatal outcome of the animals. The effects of human SOD, a representative scavenger of oxygen free radicals, on the survival rates were investigated in the rats with temporary splanchnic ischemia. The temporary ischemia was induced by the occlusion of anterior mesenteric and celiac arteries for 30min under anesthesia. Prior and after treatment with 2mg/100g of human SOD, iv or sc, produced significant improvements in survival rates. Human SOD, cloned from human placenta DNA and expressed in microorganisms, has extreme homogeneity. The results suggest the possible introduction of human SOD into clinical field as an effective scavenger of oxygen free radicals.(Ogawa R, Bitoh H, Ohi Y: The effect of human SOD on the survival rate in rats with temporary splanchnic ischemia. J Anesth 2: 41–45, 1988)  相似文献   
103.
We have investigated the clinical significance of urinary tissue polypeptide antigen (TPA) as a tumor marker for urothelial cancers. Urinary TPA levels were determined by the immunoradiometric assay of Prolifigen TPA Kit "Daiichi"-II in 486 healthy controls and 1835 patients with various diseases including 526 with urothelial cancers and 140 with prostatic cancer. The mean value of urinary TPA was 199 +/- 213 (1SD)U/1 in 486 healthy controls. 95% of them having a level below 600 U/l. Therefore, 600 U/l was applied as a cut-off level. Positive rates of urothelial cancers and reactivated prostatic cancer were 57.6% (148 of 248 cases) and 45.5% (5 of 11 cases) respectively. On the other hand, the false positive rate of most urological benign diseases was only about 20% except for the acute stage of urinary tract infections and upper urinary tract stones with hydronephrosis. There was no significant difference in the positive rate between urinary TPA level and urinary cytology in urothelial cancers. The combination of both tests raised the positive rate to 73.1%. Therefore, urinary TPA may be useful in the monitoring of urothelial cancers, and the combination of urinary TPA and urinary cytology may increase the diagnostic accuracy.  相似文献   
104.
The distributions of radioactivity were examined by whole body autoradiography and liquid scintillation spectrophotometry in male ddY mice following oral administration of tritium-labelled Irgasan® DP300 (2,4,4-trichloro-2-hydroxydiphenyl ether) (I) and its three chlorinated derivatives; 2,3,4,4-tetrachloro-2-hydroxydiphenyl ether (II), 2,4,4,5-tetrachloro-2-hydroxydiphenyl ether (III) and 2,3,4,4,5-pentachloro-2-hydroxydiphenyl ether (IV). The autoradiograms at 6 or 24 hr showed that the radioactivity distributed in the gall, liver, lung, heart, and kidneys. Among these tissues the radioactivity was most concentrated in the gall, suggesting the enterohepatic circulation of these compounds. A much higher level of radioactivity in each tissue was observed in mice receiving [3H]-III than the other compounds tested. Most of the radioactivity disappeared from each tissue in 24 hr due to [3H]-Irgasan DP300, [3H]-II or [3H]-IV, but in 96 hr it was due to [3H]-III.The cumulative radioactivity excreted in urine after administration of these compounds was in the order of [3H]-Irgasan DP300, [3H]-II, [3H]-IV and [3H]-III while that in feces was in the order of [3H]-IV, [3H]-III, [3H]-II and [3H]-Irgasan DP300,This work was presented at the 106th Annual Meeting of the Pharmaceutical Society of Japan (1986).  相似文献   
105.
Summary A new sensitive HPLC method for the determination of urinary delta-aminolevulinic acid (ALA-U) was used to evaluate the relationship between blood-lead (Pb-B) and ALA-U levels in male workers exposed to lead. The differences between the ALA-U levels determined by this method (ALAU-HP) and by a colorimetric method (ALA-U-CL) are discussed. The HPLC method gave values similar to the ALA-U-CL values at high ALA-U level. However, at low blood-lead levels (58 ± 22 g/l, n = 23), the mean ALA-U-HP level corrected by urinary creatinine level was one-third of the corrected ALA-UCL level (0.83 ± 0.14 and 2.4 ± 0.5 mg/g creatinine, respectively). A significant increase of the mean corrected ALA-U-HP level was observed at 162 ± 22 g/l Pb-B (P < 0.05, n = 26), while that of ALA-UCL was observed at 245 ± 30 g/l Pb-B (P < 0.01, n = 37). The regression equation based on the logistic model fitted well to the relationship data between the Pb-B level and the percentage of the subjects with corrected ALA-U-HP above the cut-off point (1.12 mg/g creatinine) and the expected Pb-B level for 50% response was 270 g/l Pb-B, while it did not fit well to the relationship data between Pb-B level and the percentage of the subjects with corrected ALAU-CL above the cut-off point (3.5 mg/g creatinine). The maximum responses for the two sets of corrected ALA-U levels were both observed at 625 ± 25 g/l. The corrected ALA-U level by HPLC method seems to be a useful indicator for biological monitoring of exposure to lead at low levels (< 400 g/l Pb-B = health-based biological limit, WHO) as well as high ones.  相似文献   
106.
Inhibition ELISA assay was used to examine the cross-reaction of the polyclonal anti-desmosine antiserum produced in rabbit against molecules possessing a "pyridinium ring" as their core structure i.e. isodesmosine, pentasine, pyridinoline and 2'-deoxypyridinoline, highly purified with column chromatography, and structurally unrelated substances, i.e. cysteic acid, taurine and 2-aminopyridine (core structure of desmosine). No cross-reaction was observed to the pyridinoline, 2'-deoxypyridinoline possessing "pyridinium ring" and derived from collagen cross-links, structurally unrelated cysteic acid and taurine, nor core structure of 2-aminopyridine. The antiserum specifically recognized the molecules derived from the elastin cross-links. Using the ELISA assay system with antisera and amino acids analysis, 10 micrograms of desmosine were extracted from 1.0 mg of the hydrolysate of commercial elastin.  相似文献   
107.
AIMS: To clarify the involvement of matrix metalloproteinase-7 (MMP-7) in cell dissociation and the subsequent invasion of pancreatic cancer cells.METHODS: Western blotting, in vitro invasion assay, immunocytochemistry, and immunohistochemistry were performed in pancreatic cancer cell lines or pancreatic cancer tissue.RESULTS: The active form of the MMP-7 protein was expressed exclusively in the conditioned medium of dissociated (PC-1.0 and AsPC-1) pancreatic cancer cells, whereas proMMP-7 protein was only detected in the conditioned medium of non-dissociated (PC-1 and Capan-2) cells. Both intracellular and conditioned medium localised MMP-7 was greatly reduced by treatment with the epidermal growth factor receptor (EGFR) inhibitor AG1478 and the mitogen activated protein kinase kinase (MEK) inhibitor U0126 in pancreatic cancer cells. MMP-7 treatment significantly induced the disruption of tight junction (TJ) structures and subsequent cell dissociation, and activation of the EGFR mediated MEK- ERK (extracellular signal regulated protein kinase) signalling pathway in the non-dissociated pancreatic cancer cells. Moreover, the strong in vitro invasiveness of dissociated cells was inhibited by AG1478 and U0126 treatment, whereas the weak invasiveness of non-dissociated cells was apparently induced by MMP-7 treatment. In addition, MMP-7 expression was stronger at the invasive front than at the centre of human pancreatic tumours.CONCLUSION: MMP-7 is involved in cell dissociation and the subsequent invasion of pancreatic cancer cells. It induces the disruption of TJ structures and forms a positive feedback loop with activation of the EGFR mediated MEK-ERK signalling pathway.  相似文献   
108.
It is known that benzodiazepines have a hypotensive effect, but the mechanism has not been well elucidated yet. To clarify whether this effect is due to central or peripheral mechanism, we administered 5 mg of diazepam or saline intravenously to healthy volunteers and assessed the change in blood pressure, heart rate, muscle sympathetic nerve activity and heart rate variability. After diazepam administration, systolic and mean blood pressure decreased significantly. Muscle sympathetic nerve activity was also significantly reduced but heart rate did not change, whereas the variables of spectral analysis of heart rate variability did not show significant change. We concluded that the hypotensive effect of diazepam in human is mainly due to the central mechanism.  相似文献   
109.
 The recently identified prostate cancer susceptibility gene ELAC2 (HPC2) harbors two common missense variants, a serine to leucine substitution at residue 217 (Leu217) and an alanine to threonine substitution at residue 541 (Thr541). We genotyped the two variants in a Japanese cohort consisting of 350 prostate cancer patients 242 male population controls, and 114 male low-risk controls. Both missense alleles, Leu217 and Thr541, were carried at higher frequency in Japanese patients than in the controls (Leu217, P = 0.0012; Thr541, P = 0.0145), and the odds ratios associated with carrying these sequence variants were higher in Japanese than in Caucasians. Although the Leu217 and Thr541 variants of ELAC2 are less common in Japanese than in Caucasians, both variants confer significantly increased risk of prostate cancer in Japanese. Carriage of these variants was not associated with age at diagnosis, tumor stage, or tumor grade in these Japanese prostate cancer patients. The allele-specific pattern of risk observed in Japanese and familial Caucasian patients was qualitatively similar; however, the magnitude of that risk was considerably greater in Japanese than in Caucasians. Received: September 3, 2002 / Accepted: October 2, 2002  相似文献   
110.
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