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   7603篇
  免费   463篇
  国内免费   9篇
耳鼻咽喉   247篇
儿科学   215篇
妇产科学   315篇
基础医学   1198篇
口腔科学   153篇
临床医学   535篇
内科学   1489篇
皮肤病学   191篇
神经病学   573篇
特种医学   420篇
外国民族医学   5篇
外科学   1158篇
综合类   53篇
一般理论   1篇
预防医学   579篇
眼科学   83篇
药学   556篇
中国医学   4篇
肿瘤学   300篇
  2021年   85篇
  2020年   54篇
  2019年   80篇
  2018年   102篇
  2017年   72篇
  2016年   105篇
  2015年   109篇
  2014年   147篇
  2013年   195篇
  2012年   322篇
  2011年   311篇
  2010年   203篇
  2009年   222篇
  2008年   314篇
  2007年   321篇
  2006年   334篇
  2005年   344篇
  2004年   305篇
  2003年   277篇
  2002年   255篇
  2001年   280篇
  2000年   333篇
  1999年   267篇
  1998年   104篇
  1997年   76篇
  1996年   65篇
  1995年   56篇
  1992年   140篇
  1991年   127篇
  1990年   146篇
  1989年   143篇
  1988年   94篇
  1987年   122篇
  1986年   111篇
  1985年   109篇
  1984年   84篇
  1983年   54篇
  1979年   94篇
  1978年   57篇
  1977年   74篇
  1976年   57篇
  1975年   81篇
  1974年   93篇
  1973年   84篇
  1972年   73篇
  1971年   62篇
  1970年   53篇
  1969年   72篇
  1968年   62篇
  1967年   56篇
排序方式: 共有8075条查询结果,搜索用时 15 毫秒
131.
Proliferative activity in primary ovarian carcinoid tumors.   总被引:1,自引:0,他引:1  
The proliferative potential of six primary ovarian carcinoids with different clinical outcome and histogenetic origin was examined immunohistochemically. The results showed that two cases with extremely high level of proliferative activity were associated with metastatic spread. In the remaining tumors, the examined factor was found to be at low level comparable with excellent prognosis of typical carcinoids in other locations. The preliminary results showed a possibility of a prognosis prediction according to typing of the ovarian carcinoids into two categories, i.e., tumors of low and intermediate malignancy. Topoisomerase II-alpha and Ki-67 are suitable markers giving valuable information about this phenomenon.  相似文献   
132.
133.
Background and purpose: Amifostine has been shown to protect against xerostomia induced by radiotherapy for head and neck cancer, but its impact on the therapeutic index is unknown. This is the first report focusing on amifostine related adverse effects leading to discontinuation of amifostine treatment.

Patients and methods: Thirty-nine patients from two centers irradiated for head and neck cancer received i.v.-infusions of amifostine prior to each radiation fraction. In a phase III study, two daily amifostine doses, 200 mg/m2 (n=21) and 340 mg/m2 (n=18), were compared for protection against radiation induced toxicity. Total radiation dose was 60–70 Gy (2 Gy per fraction), nine patients received concurrent chemotherapy with cisplatin/5-FU. amifostine was usually discontinued after >1 episode of serious toxicity during subsequent treatment sessions.

Results: In 16/39 patients (41%) amifostine was discontinued due to severe adverse effects, which led to discontinuation of the phase III study. In four of 16 patients radiotherapy was delayed due to amifostine related adverse effects for 1–3 days. Discontinuation occurred more often in patients receiving chemotherapy. The results led to a literature review for amifostine treatment during radiotherapy in head and neck cancer patients. Regarding our series and published series using an amifostine schedule comparable to ours, total discontinuation rate was 27% (57/214). Discontinuation was significantly influenced by chemotherapy (P=0.007), but not by amifostine dose (P=0.156).

Conclusion: Daily i.v. administration of amifostine during radiotherapy in head and neck cancer is associated with a high rate of serious adverse effects leading to discontinuation of amifostine treatment and sometimes delay of radiotherapy.  相似文献   

134.
BACKGROUND: Current organ shortage has led to a reconsideration of non-heart-beating cadaveric donation. METHODS: We assessed the effectivity of dual, i.e., arterial and portal-venous versus exclusive, arterial gravity perfusion for procurement of rat livers after 30 min and 60 min of cardiac arrest, analyzing the rate and homogeneity of microvascular perfusion by in situ fluorescence microscopy. RESULTS: After 30 min of cardiac arrest, a nearly 100% recovery of acinar perfusion with a sinusoidal density not significantly different from that of normal, nonischemic livers was achieved by dual gravity perfusion. Prolongation of cardiac arrest to 60 min caused an almost 50% deficit of acinar and sinusoidal perfusion (P<0.05) with a concomitant 2-3-fold increase of heterogeneity of hepatic microperfusion. Regardless of the warm ischemic time period, dually perfused livers exhibited significantly (P<0.05) higher rates of both acinar and sinusoidal perfusion with increased homogeneity of microcirculation when compared with exclusive arterial perfusion. CONCLUSION: These data underline the need and benefit of dual perfusion as well as the limitation of warm ischemic tolerance to 30 min for safe liver procurement of non-heart-beating donors.  相似文献   
135.
Achalasia is an esophageal motor disorder characterized by abnormal relaxation of the lower esophageal sphincter and absence of progressive peristalsis in the esophageal body. Previous studies evaluating esophagomyotomy and esophageal resection specimens have shown the presence of myenteric inflammation to be a consistent and early pathologic change in patients with achalasia. Thus, the goal of this study was to determine the immunohistochemical characteristics of the inflammatory infiltrate within the myenteric plexus in patients with clinically early and end-stage achalasia. Using formalin-fixed tissue, we analyzed the immunohistochemical features of the myenteric lymphocytes using antibodies that recognize B cells (CD20), T cells (CD3), T cell subsets (CD8), and the activation state of T cell subpopulations (TIA-1 and granzyme B) in nine patients with clinically early achalasia who underwent esophagomyotomy and 13 patients with clinically endstage achalasia who underwent esophageal resection. The myenteric infiltrate in all nine esophagomyotomy specimens was composed predominantly of T cells (CD3-positive), the majority of which also stained for CD8. In five of nine specimens, the majority of CD8-positive cells stained for TIA-1. In the esophageal resection specimens, the myenteric infiltrate was composed predominantly of CD3-positive T cells in seven of 13 cases. In three cases, there was a predominance of CD20-positive B cells, and in the remaining three cases there were relatively equal numbers of T and B cells. In eight of 13 cases, the majority of T cells stained for CD8. TIA-1 immunoreactivity was found in the majority of CD8-positive cells in nine of 13 cases. In all esophagomyotomy and esophageal resection specimens studied, rare granzyme B-positive cells were detected. In conclusion, the majority of myenteric inflammatory cells in patients with achalasia are CD3-positive T cells, most of which are also CD8-positive, although the relative percentage of such cells appears to decrease with disease progression. Furthermore, many of the CD3-positive/CD8-positive myenteric lymphocytes also express TIA-1, suggesting they are resting or activated cytotoxic T cells. The immunohistochemical demonstration of granzyme B in a subpopulation of these cells supports the contention that achalasia is an immune-mediated disease, although the inciting antigen remains an enigma.  相似文献   
136.
Zusammenfassung Fragestellung: Geburtstraumatische L?sionen des Plexus brachialis treten in 0,6–2,5‰ aller Geburten auf. 80–95% dieser L?sionen bilden sich spontan zurück. Sollte keine spontane Funktionsrückkehr innerhalb der ersten 6 Monate eintreten, mü?te nach entsprechender Diagnostik, wie elektrophysiologische und myelocomputertomographische Untersuchungen eine operative Freilegung des Plexus brachialis erfolgen. Methode: In einem Zeitraum von 5 Jahren haben wir 7 Kinder mit postpartaler Plexusl?sion unter 99 operativ versorgten Plexusl?sionen behandelt. 6/7 Kindern zeigten pr?operativ Wurzelausrisse. Bei 2 Kindern wurde eine Neurotisation, bei 4 eine autologe Transplantation und beim letzten eine ?u?ere Neurolyse des Plexus brachialis vorgenommen. Ergebnisse: Bisher wurden nur 3/7 Kindern über einen l?ngeren Zeitraum (26–42 Monate) nachuntersucht. Alle transplantierten Nerven zeigten klinisch eine Reinnervation. Eine Wiederherstellung der normalen Funktion war durch begleitende Wurzelausrisse limitiert. Schlu?folgerungen: Wir empfehlen als optimalen Zeitpunkt für die Operation den Zeitraum zwischen dem 6. und 9. Monat. Um optimale Ergebnisse bei diesen Kindern zu erzielen, mu? sich zun?chst eine intensive krankengymnastische Behandlung anschlie?en und sp?ter sollte die Option für Muskeltransfers und orthop?dische Operationen gew?hrleistet sein.   相似文献   
137.
138.
Oral immunoglobulin has been described as preventing necrotizing enterocolitis(NEC) in preterm infants. To prevent NEC in extremely low birth weight infants (ELBW), we have carried out oral IgG prophylaxis since April 1991. The efficacy of this prophylaxis was examined in a study comparing historical cohorts. ELBW infants delivered in the Department of Obstetrics and Gynaecology of the University of Ulm and treated until day 28 in the level III intensive care nursery, Division of Neonatology, University of Ulm were included. Cohort 1, born between 1.1.1988 and 31.3.1991, received no oral IgG and served as a control [n=84, gestational age: median 26 weeks, range 24–34; birth weight: 811 g, 490–990], cohort 2, born between 1.4.1991 and 31.12.1995 [n=137, gestational age: 26 weeks, 22–32; birth weight: 760 g, 362–995], received 6 × 100 mg/kg human IgG (Beriglobin) orally on days 1–28. NEC, stage 2a and higher according to the modified classification of Bell, was observed in 9 of 84 (10.7%) infants of cohort 1 and in 11 of 137 (8%) infants of cohort 2 until day 28. The difference did not reach statistical significance (P=0.63 Fisher's exact test). Conclusion In this historical cohort study, ELBW infants were not protected against NEC by oral IgG. The present published evidence does not allow recommendation of oral human IgG administration in preterm infants as a prophylactic measure against NEC. Received: 8 June 1997 / Accepted in revised form: 1 January 1998  相似文献   
139.
The purpose of this study was to investigate the value of bone scintigraphy including single-photon emission tomography (SPET) and semiquantitative analysis for the assessment of graft viability following microvascularized bone transplantation. We evaluated 60 scintigraphic studies of 36 patients with 39 bone grafts. Thirty-four investigations were performed 6-11 days (early bone scans) and 26 up to 11 months (late bone scans) after mandibular reconstruction. After administration of 550 MBq technetium-99m methylene diphosphonate, planar scintigrams and a SPET study were performed. The data were reconstructed iteratively. Scans were evaluated visually and semiquantitatively by a region of interest technique using the ratio between transplant and cranium (T/C). Patients with uncomplicated healing showed a T/C ratio >1.0 in early and late bone scans. In cases with necrosis, the T/C ratio was below 1.0 when performing early bone scans. However, in late bone scans, some patients with necrosis showed a slightly increased uptake and a T/C ratio >1.0. The data demonstrate that as early as 6-11 days after mandibular reconstruction, increased tracer uptake proves that the surgery has been successful and indicates a normal healing process. Especially in the early bone scans no false-positive or false-negative results were observed and the T/C ratio clearly differentiated between vital and non-vital bone grafts. At later times false-positive findings could be observed; these were, however, rare because of the significantly higher tracer uptake of the healthy grafts when compared with completely or partially necrotic transplants.  相似文献   
140.
K(ATP) channels regulate the neuronal excitability and their activation during hypoxia/ischemia protect neurons. The activation of K(ATP) channels during hypoxia is assumed to occur mainly due to the fall in intracellular ATP levels, but other intracellular signalling pathways can be also involved. We measured single K(ATP) channel currents in inspiratory brainstem neurones of neonatal mice. The activity of K(ATP) channels was enhanced in hypoosmotic bath solutions, or after applying negative pressure to the recording pipette. Cytochalasin B activated K(ATP) channels and prevented the effects of osmo-mechanical stress, indicating that cytoskeleton rearrangements, which occur during hypoxia, contribute to the activation of K(ATP) channels. During hypoxia, extracellular levels of many neurotransmitters increase, leading to activation of corresponding metabotropic receptors that can modulate K(ATP) channels. K(ATP) channels were activated by GABA(B) agonist, baclofen, by mGLUR2/3 agonists and were inhibited by mGLUR1/5 agonists. K(ATP) channels were activated by phorbol esters and were inhibited by staurosporine. These treatments did not occlude the modulating actions of mGLUR agonists, indicating that they are not mediated by protein kinase C. Activator of alpha-subunits of G-proteins Mas 7 increased and their inhibitor GPant-2 decreased the activity of K(ATP) channels. In the presence of either agent, the modulatory actions of baclofen and mGLUR agonists were not observed. We conclude that K(ATP) channels are modulated by G-proteins that are activated by metabotropic receptors for GABA and glutamate and their release during hypoxia complements activation of channels by osmo-mechanical stress and [ATP](i) depletion.  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