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   3874篇
  免费   180篇
  国内免费   21篇
耳鼻咽喉   30篇
儿科学   63篇
妇产科学   42篇
基础医学   535篇
口腔科学   71篇
临床医学   248篇
内科学   1220篇
皮肤病学   56篇
神经病学   218篇
特种医学   154篇
外科学   556篇
综合类   10篇
预防医学   214篇
眼科学   38篇
药学   218篇
中国医学   2篇
肿瘤学   400篇
  2023年   21篇
  2022年   35篇
  2021年   61篇
  2020年   35篇
  2019年   50篇
  2018年   73篇
  2017年   46篇
  2016年   45篇
  2015年   56篇
  2014年   92篇
  2013年   110篇
  2012年   189篇
  2011年   193篇
  2010年   122篇
  2009年   95篇
  2008年   187篇
  2007年   233篇
  2006年   245篇
  2005年   219篇
  2004年   208篇
  2003年   188篇
  2002年   200篇
  2001年   83篇
  2000年   102篇
  1999年   109篇
  1998年   51篇
  1997年   65篇
  1996年   50篇
  1995年   35篇
  1994年   32篇
  1993年   39篇
  1992年   74篇
  1991年   80篇
  1990年   72篇
  1989年   67篇
  1988年   73篇
  1987年   56篇
  1986年   52篇
  1985年   41篇
  1984年   30篇
  1983年   42篇
  1982年   19篇
  1980年   17篇
  1979年   26篇
  1978年   17篇
  1977年   12篇
  1976年   14篇
  1971年   12篇
  1970年   12篇
  1965年   11篇
排序方式: 共有4075条查询结果,搜索用时 15 毫秒
51.
Summary To evaluate the effects of calcium disodium ethylenediamine tetraacetate (CaEDTA) on the concentrations of lead, zinc and copper in plasma, erythrocyte and urine, and the delta-aminolevulinic acid dehydratase (ALAD) activity in erytrocyte, we administered CaEDTA in 1-h intravenous infusion to ten male gun metal founders with blood-lead concentration of 39 to 64 g/dl (mean 49 g/dl). We found that the plasma concentration of lead, following a rapid rise within the first 3 h, fell temporarily to the level significantly lower than the initial level 19 h after start of the infusion. The plasma concentration of zinc fell to the minimal level 5 h after the infusion; and the erythrocyte concentration of zinc and the ALAD activity concurrently rose to the maximal level 5 h after the infusion. By contrast, no significant alteration was observed in the concentrations of copper in plasma and erythrocyte. The maximal level of urinary metal excretion was attained during the period between 1 and 2 h after start of CaEDTA infusion for lead; within 2 h for zinc; and between 2 and 4 h for copper. The urinary metal excretion returned to the initial level 14 to 24 h after infusion for zinc and copper; but lead excretion was still higher than the initial level during this period. The difference in the kinetics of the three metals following CaEDTA injection is discussed in the light of these findings.  相似文献   
52.
53.
Clinical and Experimental Nephrology - The progression of chronic kidney disease (CKD) depends on the extent of fibrosis in the kidneys; however, a renal biopsy is necessary to evaluate the...  相似文献   
54.
Ovarian involvement of cytomegalovirus (CMV) is rarely observed in autopsy and biopsy materials. Cortical necrosis of the ovaries was found in an autopsy case with generalized CMV infection. The patient was an 11-year-old girl in a remission state of acute lymphocytic leukemia. Autopsy revealed several areas showing necrotic change up to 2 mm in size in the cortex of both ovaries. Many cytomegalic cells were found in both the necrotic and intact areas of the cortex. CMV had infected the granulosa, thecal and stromal cells as well as vascular endothelial cells. Oocytes of neither primary nor graafian follicles showed cytomegalic changes, although they were destroyed due to the necrosis. CMV antigen was immunohistologically detected in these cytomegalic cells. Ultrastructurally, herpesvirus-type particles were revealed in the nuclei and cytoplasm of the cytomegalic cells. This case demonstrated that ovarian infection with CMV can potentially induce cortical necrosis and decrease the number of oocytes. ACTA PATHOL JPN 38 : 1069 ∼ 1076, 1988.  相似文献   
55.
31P and 23Na nuclear magnetic resonance (NMR) spectroscopy was employed to study the dynamic changes in intracellular high-energy phosphates and sodium during 15min of forebrain ischemia and recirculation in in vivo rat brain. In the presence of the shift reagent Dysprosium triethylenetetramine-N,N,N,N,N,N-hexaacetic and [Dy(TTHA)], the sodium peak separated into two peaks, unshifted and shifted. During 15min of ischemia, the unshifted sodium peak decreased and the shifted sodium peak increased. With recirculation, the unshifted and the shifted sodium peaks returned to the preischemia level within 10min, but the shifted one increased during 30–60min. Intracellular high-energy phosphates and intracellular pH (pHi) decreased during 15min of ischemia and returned to the preischemia levels within 20min of recirculation. We conclude that the decrease in unshifted sodium peak during ischemia is due to the decrease in subarachnoid sodium and the cellular influx of interstitial sodium would be minimum. The increase in shifted sodium peak during ischemia is considered to be due to the dilatation of cerebral blood vessels and the increase in interstitial sodium which was transported from subarachnoid space.(Kurata M: 31P and 23Na nuclear magnetic resonance study on forebrain ischemia in rats with shift reagent Dy(TTHA). J Anesth 7: 325–333, 1993)  相似文献   
56.
Mechanical stimulation of one mammary tumor cell in culture induced an increase in its intracellular calcium concentration which spread to surrounding cells. The increase in calcium can also be induced by addition of a solution in which cultured mammary tumor cells were stimulated by repeated pipetting (solution after pipetting cells, SAPC). The activity of the SAPC was completely abolished by treatment with snake venom phosphodiesterase or pyrophosphatase. Uridine triphosphate (UTP), uridine diphosphate (UDP) and ATP (1 M each) were detected in the SAPC, whereas 5-UMP and 5-AMP were produced by phosphodiesterase digestion. A mixture of UTP, UDP and ATP (1 M each) elicited a calcium response which was comparable to that induced by SAPC, while UTP, UDP or ATP alone at 1 M elicited a small increase in calcium concentration in mammary tumor cells. Suramin, a competitive antagonist of P2 purinoceptors, diminished the spreading of the calcium wave induced by mechanical stimulation. It also blocked the responses to SAPC, UTP, UDP and ATP. These findings suggest that the mechanical stimulation results in the release of UTP, UDP and ATP into the extracellular space which mediates induction of the spreading calcium response via P2U-type purinoceptors.  相似文献   
57.
The ability of plasmid DNA encoding hemagglutinin (HA), neuraminidase (NA) or matrix protein (M1) from influenza virus A/PR/8/34 (PR8) (H1N1), and mixtures of these plasmid DNAs (HA + NA and HA + NA + M1) to protect against homologous or heterologous virus infection was examined in BALB/c mice. Each DNA was inoculated twice, 3 weeks apart, or four times, 2 weeks apart, at a dose of 1 microg of each component per mouse by particle-mediated DNA transfer to the epidermis (gene gun). Seven days after the last immunization, mice were challenged with a lethal homologous or heterologous virus and the ability of each DNA to protect the mice from influenza was evaluated by observing lung virus titers and survival rates. The administration of a plasmid DNA mixture of either (HA + NA) or (HA + NA + M1) provided almost complete protection against the PR8 virus challenge, and this protection was accompanied by high levels of specific antibody responses to the respective components. The degree of protection afforded in these groups is significantly higher than that in mice given either HA- or NA-expressing DNA alone, which provided only a partial protection against PR8 challenge or that in mice given M1-expressing DNA, which failed to provide any protection. In addition, both of the plasmid DNA mixtures (HA + NA) and (HA + NA + M1) showed a slight tendency to provide cross-protection against an A/Yamagata/120/86 (H1N1) virus challenge, and this was accompanied by a relatively high level of cross-reacting antibodies. Thus, there was no clear difference between the ability of the HA + NA and HA + NA + M1 plasmid DNA mixtures in providing protection against either a PR8 or heterologous virus challenge. These results suggest that in mice immunized by gene gun, a mixture of plasmid DNAs encoding HA and NA can provide the most effective protection against the virus challenge. The addition of the M -expressing plasmid DNA to this mixture does not enhance the degree of protection afforded.  相似文献   
58.
(E)-2-deoxy-2-(fluoromethylene)cytidine (FMdC), one of the most potent inhibitors of ribonucleoside diphosphate reductase, was selected for clinical development because of its novel mechanisms of action, and strong antitumor activity against experimental tumor models. This study was designed to determine the toxicities, maximum-tolerated dose (MTD), and pharmacokinetic profile of FMdC. FMdC was given orally for 5 consecutive days every 3 or 4 weeks in patients with advanced solid tumors. The starting dose was 8 mg/m2/day. Pharmacokinetic studies were carried out on days 1 through 5 of the first cycle. Ten patients with non-small cell lung cancer received 15 courses of FMdC at doses which were de-escalated from 8 mg/m2/day to 2 mg/m2/day because of unexpected severe toxicities at the starting dose level. Neutropenia was the dose-limiting toxicity. Thrombocytopenia and anemia were mild. Flu-like symptoms and fever were the common non-hematologic toxicities. The MTD was 4 mg/m2/day, since four of six patients developed grade 3–4 neutropenia. At the 4 mg/m2/day dose level, the mean terminal half-life, maximum plasma concentration (Cmax), plasma clearance, and mean residence time on day 1 were 3.20 h, 15.8 ng/ml, 2.91 l/h/kg, and 4.03 h, respectively. The recommended dose for phase II studies with this schedule is also 4 mg/m2/day for 5 days. Further investigations are necessary to establish optimal dosing schedules and routes for the administration of FMdC.  相似文献   
59.
Zusammenfassung Cyproheptadin ist seit Jahren als Antimetabolit des Serotonins verwendet worden. Es wurde über eine Wirksamkeit desselben bei extrapyramidalen Hyperkinesien (von den Angelsachsen als tardive dyskinesia bezeichnet) nach Neuroleptika-Medikation berichtet. Wir behandelten 11 Patienten, die wegen chronischer Schizophrenie behandelt wurden und schwere Dyskinesien aufwiesen, Cyproheptadin (Periactinol®, Periactin) verabreicht. In vier Fällen verschwand unter dieser Medikation das extrapyramidale hyperkinetische Syndrom vollständig, bei vier weiteren Fällen trat eine befriedigende Besserung auf. Im Verlaufe der Therapie wurden keine nennenswerten Nebenwirkungen beobachtet, die eindeutig auf das Cyproheptadin zurückzuführen gewesen wären.  相似文献   
60.
There has been a dramatic decline in reported hospitalization and mortality rates for peptic ulcer disease in the past two decades. Data from the National Center for Health Statistics and from the Commission on Professional and Hospital Activities were examined to determine the cause(s) for this decline. Gastric and duodenal ulcer mortality rates decreased by 58 per cent and 68 per cent, respectively, from 1962 to 1978; changes in criteria for selecting the underlying cause of death might account for some of this apparent decrease. Hospitalization rates for duodenal ulcers decreased nearly 50 per cent from 1970 to 1978, but hospitalizations for gastric ulcers did not decrease. During this same time period, hospitalizations for peptic ulcers as one of the "all listed" causes remained stable, and hospitalizations for a closely related diagnosis, gastritis/duodenitis, increased. Changes in coding practices, hospitalization criteria, and diagnostic procedures appear to have contributed to the decline in reported hospitalization and mortality rates for peptic ulcer disease.  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