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   16804篇
  免费   864篇
  国内免费   189篇
耳鼻咽喉   135篇
儿科学   329篇
妇产科学   145篇
基础医学   1862篇
口腔科学   259篇
临床医学   998篇
内科学   5576篇
皮肤病学   372篇
神经病学   1007篇
特种医学   607篇
外科学   2789篇
综合类   67篇
一般理论   3篇
预防医学   340篇
眼科学   468篇
药学   900篇
中国医学   35篇
肿瘤学   1965篇
  2024年   23篇
  2023年   165篇
  2022年   300篇
  2021年   548篇
  2020年   311篇
  2019年   424篇
  2018年   441篇
  2017年   361篇
  2016年   438篇
  2015年   459篇
  2014年   615篇
  2013年   720篇
  2012年   1220篇
  2011年   1340篇
  2010年   782篇
  2009年   588篇
  2008年   1016篇
  2007年   1170篇
  2006年   1091篇
  2005年   1084篇
  2004年   991篇
  2003年   915篇
  2002年   945篇
  2001年   175篇
  2000年   140篇
  1999年   150篇
  1998年   190篇
  1997年   183篇
  1996年   156篇
  1995年   120篇
  1994年   106篇
  1993年   97篇
  1992年   80篇
  1991年   67篇
  1990年   68篇
  1989年   61篇
  1988年   33篇
  1987年   35篇
  1986年   24篇
  1985年   26篇
  1984年   29篇
  1983年   14篇
  1982年   18篇
  1981年   20篇
  1980年   18篇
  1979年   12篇
  1977年   11篇
  1976年   8篇
  1975年   8篇
  1968年   8篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Although the cardiovascular events such as stroke, angina pectoris and myocardial infarction can occur at any time of day, it has been known that the peak incidence of the cardiovascular events increases during the morning period. In elderly hypertensives, a greater morning blood pressure surge is associated with an advanced silent cerebrovascular disease as well as a higher incidence of stroke. Thus, the blood pressure control of the early morning period may become an important therapeutic strategy for preventing the cardiovascular events. In this review, we focused on the recent strategy for morning blood pressure rising in the elderly hypertensives.  相似文献   
992.
OBJECTIVE: To assess the prognostic role of ambulatory 24-h pulse pressure (PP) on various vascular events in relatively young type 2 diabetic subjects under 60 years of age. RESEARCH DESIGN AND METHODS: In this prospective study, 237 type 2 diabetic subjects without any history of vascular complications were analyzed. After excluding 9 dropout subjects, 228 subjects (mean age, 46 years; 69% men; mean follow-up period, 100 months) entered the study. RESULTS: Distribution of 24-h PP for all subjects showed left skewed data, indicating that there may be a diabetic subgroup that had a wide PP. Therefore, further analysis was performed by stratifying the diabetic subjects by quartile of 24-h PP. Outcomes for the widest quartile (n = 58; cut point = 53.3 mmHg) was then compared with those from the other narrower quartiles (n = 170). In the diabetic subjects with a wide PP, cardiovascular events occurred more frequently than those in the diabetic subjects with a narrow one (20.7 vs. 4.1%; P < 0.001), resulting in the significant difference in the cumulative incidence of cardiovascular events (P < 0.001, log-rank test), but not cerebrovascular events, between the two subgroups. The Cox model revealed that a wide 24-h PP at baseline independently predicted subsequent cardiovascular events but not cerebrovascular events. By contrast, only duration of diabetes was the risk factor for cerebrovascular events. CONCLUSIONS: This study showed that a wide 24-h PP is predictive for cardiovascular events in relatively young diabetic subjects.  相似文献   
993.
CD163 is a marker of activated macrophages, and increased levels of soluble CD163 have been detected in sera obtained from patients with hepatitis. The aim of this study was to detect the expression of CD163 in the liver from patients with viral hepatitis. Frozen sections of liver specimens were obtained from 5 patients with acute viral hepatitis (AH) and from 23 patients with chronic viral hepatitis (CH). The expression of CD163 in the liver was determined immunohistochemically using monoclonal antibody to human CD163. Double immunostaining was done to assess those cell types that express CD163 in the liver. The frequencies of CD163-positive cells were significantly higher both in the portal areas and in the hepatic lobules in the liver of patients with AH compared to those with CH (p < 0.05). Double immunostaining revealed that most of the CD163-positive cells were macrophages and Kupffer cells, because they expressed CD68. The expression of CD163 was very low in endothelial cells and liver stellate cells. This study shows that macrophages are activated in hepatitis liver.  相似文献   
994.
Cementum is a specialized mineralized tissue covering root surface of the tooth. Although the tissue's composition resembles bone, there are distinct structural and functional differences between the two mineralized tissues. In this study, the genes that are differentially expressed in putative cementoblasts (human cementum-derived cells [HCDCs]) compared with preosteoblastic cells (human bone marrow stromal cells [BMSCs]) were screened by two independent microarray systems, and some of the selected genes were further analyzed by quantitative real-time RT-PCR. The gene encoding glucose transporter 1 [GLUT1], which showed the greatest difference between the two groups by the latter analysis, was subjected to further analyses. High levels of the GLUT1 protein in HCDCs, but not in BMSCs, were detected by Western blotting and immunocytochemistry. Furthermore, intense immunoreactivities for GLUT1 were observed in cementoblasts and cementocytes but not in osteoblasts or osteocytes in human periodontal tissues. These results indicate that GLUT1 may play a role in cementogenesis and could serve as a biomarker to differentiate between cells of cementoblastic and osteoblastic lineage.  相似文献   
995.
The effects of capsaicin and mucosal acidification on gastric HCO3(-) secretion were compared in wild-type and prostacyclin (PGI2) IP receptor or prostaglandin E receptor EP1 or EP3 knockout C57BL/6 mice as well as rats. Under urethane anesthesia, the stomach was mounted on an ex vivo chamber, perfused with saline, and the secretion of HCO3(-) was measured at pH 7.0 using the pH-stat method. Capsaicin or 200 mM HCl was applied to the chamber for 10 min. Capsaicin increased the secretion of HCO3(-) in rats and wild-type mice, the response at 0.3 mg/ml being equivalent to that induced by acidification. This effect of capsaicin in rats was abolished by ablation of capsaicin-sensitive afferent neurons and attenuated by indomethacin, N(G)-nitro-L-arginine methylester (L-NAME), and capsazepine [transient receptor potential vanilloid type 1 (TRPV1) antagonist] but not FR172357 [3-bromo-8-[2,6-dichloro-3-[N[(E)-4-(N,N-dimethylcarbamoyl) cinnamidoacetyl]-N-methylamino]benzyloxy]-2-metylimidazo[1,2-a]pyridine; bradykinin B2 antagonist] or the EP1 antagonist. The acid-induced HCO3(-) secretion was attenuated by indomethacin, L-NAME, the EP1 antagonist, and sensory deafferentation, but not affected by capsazepine or FR172357. Prostaglandin E2 (PGE2), NOR-3 [(+/-)-(E)-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexeneamine] (NO donor), and bradykinin stimulated the secretion of HCO3(-), and the effect of bradykinin was blocked by indomethacin and L-NAME as well as FR172357. The stimulatory effect of capsaicin disappeared in IP (-/-) mice, whereas that of acidification disappeared in EP1 (-/-) mice. Intragastric application of capsaicin increased mucosal PGI2 but not PGE2 levels in the rat stomach. These results suggested that both capsaicin and acid increase gastric HCO3(-) secretion via a common pathway, involving PG and NO as well as capsaicin-sensitive afferent neurons, yet their responses differ concerning TRPV1 or prostanoid receptor dependence.  相似文献   
996.
997.
Subcellular distribution of 111In and 169Yb in tumor and liver   总被引:1,自引:1,他引:0  
Subcellular distribution of 111In and 169Yb was quantitatively determined to evaluate the role of the lysosome in accumulation of these nuclides in malignant tumor tissue and in the liver using three different tumor models and the host liver. In Yoshida sarcoma and Ehrlich tumor, most of the radioactivity of these nuclides was localized in the supernatant fraction, and only a small amount of radioactivity was localized in the mitochondrial fraction, which contains lysosomes. In the liver, most of the radioactivity was concentrated in the mitochondrial fraction. The radioactivity of this fraction increased with time after the administration of these nuclides and reached approximately 50% of the total radioactivity within 24 h. In the case of hepatoma AH109A, radioactivity of the mitochondrial fraction increased with time after administration, and about 30% of the total radioactivity was concentrated in this fraction after 24 h. It is concluded that the lysosome does not play a major role in the tumor concentration of these nuclides, although it may play an important role in their liver concentration. In the case of hepatoma AH109A, it is presumed that lysosome plays a considerably important role in the tumor concentration of these nuclides, hepatoma AH109A possessing some residual features of the liver.  相似文献   
998.
999.
1000.
To objectively evaluated the usefulness of the standard formulation of cefaclor (CCL) and the long-acting formulation of cefaclor (S6472) in noncatheterized complicated urinary tract infection (UTI), a double-blind comparison study was carried out using cephalexin (CEX) as a control. Patients were orally treated with either 500 mg of CCL 3 times/day, 750 mg of S6472 2 times/day, or 500 mg of CEX 4 times/day for 14 days. Overall clinical effect was evaluated on days 5 and 14 in accordance with the UTI therapeutic evaluation standard, with check for recurrence on day 21. There was no demographic difference between the groups. There was no difference in the effective rate on day 5 among the 3 treatment groups: 58.1% in S6472 group, 66.0% in CCL group and 61.9% in CEX group. Nor on day 14, was there any significant difference in the effective rate among the 3 groups: 70.8% in S6472 group, 63.4% in CCL group and 61.8% in CEX group. Stratification analyses (by UTI group, infection site, in- or out-patient, time of starting treatment, pretreatment severity of pyuria, total number of bacteria before treatment) revealed no significant difference among the 3 groups. Therapeutic effect evaluated by physicians in charge was not significantly different among the 3 groups on day 5 or day 14. In terms of overall therapeutic effect, all 3 products were very effective in patients infected with sensitive bacteria: On day 5, 85.4% in S6472 group, 84.4% in CCL group, and 83.7% in CEX group. There was no significant difference among the 3 groups on either day. The incidence of side effects was not significantly different among the 3 groups: 4 out of 129 patients treated with S6472 (3.1%), 2 of 131 treated with CCL (1.5%) and 2 of 128 with CEX (1.6%). Clinical laboratory tests revealed 4 abnormal findings in 4 patients treated with S6472, 6 findings in 4 treated with CCL, and 4 findings in 2 treated with CEX, showing no significant difference in incidence among the 3 groups. Both side effects and abnormal clinical laboratory findings were mild and reversible. Physicians in charge judged the usefulness of the 3 drugs on days 5 and 14, taking efficacy and safety into consideration. Significant difference was not observed. The presence of recurrence was examined 7 days after drug withdrawal in patients regarded as remarkable responders to 14-day treatment by overall therapeutic effect evaluation.(ABSTRACT TRUNCATED AT 400 WORDS)  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