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   1620篇
  免费   65篇
  国内免费   11篇
耳鼻咽喉   7篇
儿科学   25篇
妇产科学   25篇
基础医学   188篇
口腔科学   9篇
临床医学   137篇
内科学   493篇
皮肤病学   46篇
神经病学   174篇
特种医学   74篇
外科学   203篇
综合类   7篇
预防医学   57篇
眼科学   56篇
药学   90篇
中国医学   1篇
肿瘤学   104篇
  2021年   11篇
  2020年   10篇
  2019年   15篇
  2018年   13篇
  2017年   19篇
  2016年   26篇
  2015年   37篇
  2014年   30篇
  2013年   39篇
  2012年   69篇
  2011年   63篇
  2010年   39篇
  2009年   50篇
  2008年   57篇
  2007年   74篇
  2006年   88篇
  2005年   89篇
  2004年   94篇
  2003年   78篇
  2002年   99篇
  2001年   47篇
  2000年   61篇
  1999年   51篇
  1998年   29篇
  1997年   23篇
  1996年   14篇
  1995年   16篇
  1994年   19篇
  1993年   8篇
  1992年   23篇
  1991年   24篇
  1990年   29篇
  1989年   20篇
  1988年   24篇
  1987年   11篇
  1986年   15篇
  1985年   26篇
  1984年   15篇
  1983年   13篇
  1981年   12篇
  1980年   15篇
  1979年   17篇
  1978年   16篇
  1975年   13篇
  1974年   11篇
  1973年   15篇
  1972年   13篇
  1969年   16篇
  1968年   11篇
  1965年   8篇
排序方式: 共有1696条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: A number of meta-analyses have led to contradictory results regarding the efficacy of the psychological and pharmacological treatment of anxiety disorders. The main reasons for these inconsistent results seem to be the inclusion of heterogeneous studies and influences of selection biases. We performed a meta-analysis, which only included studies using a direct comparison of pharmacological, psychological, or combined treatments. METHOD: Sixteen studies on panic disorder, six studies on social anxiety disorder, and two studies on generalized anxiety disorder have been analyzed. Effect sizes for differences between the different treatment modalities were calculated. Also, the effect sizes of the pre-post differences were calculated. RESULTS: Pharmacological treatment, cognitive-behavioural treatment, and the combination of both treatment modalities all led to substantial improvement between pre- and post-treatment. Combined pharmacological and psychological treatment was superior to the monotherapies for panic disorder. For social anxiety disorder, there is only preliminary support for combined treatment. Due to lack of sufficient data, no final conclusions can be drawn for generalized anxiety disorder. CONCLUSIONS: While drug treatment and CBT showed equal efficacy, only in panic disorder the combination of pharmacological and psychological treatment was superior to either treatment alone. For the other anxiety disorders, the evidence for greater efficacy of combination treatment is still not sufficient due to lack of studies.  相似文献   
2.
3.
The accumulation of blood monocytes at sites of predilection of the vessel wall is an early cellular event of atherogenesis. Proteins of the vessel wall may facilitate monocyte adhesion and thus promote their recruitment. It has been shown that the relative content of extracellular fibrinogen increases during lesion development, and this study investigated the contribution of immobilized fibrinogen to monocyte adhesion and the underlying mechanism. Freshly isolated human blood monocytes were cultivated in serum-free RPMI 1640 in tissue culture wells precoated with albumin, fibrinogen, or fibrin. After 16 h the plates were washed and adherent cells enumcrated. Immobilized fibrinogen enhanced monocyte adhesion more than 1.9-fold compared to immobilized albumin or fibrin (P<0.05). Concomitant addition of the protein kinase C (PKC) inhibitors staurosporine or H7 suppressed monocyte adherence to immobilized fibrinogen but exerted no significant effect upon adhesion to any other surface tested. Stimulation of monocytes using phorbol myristate acetate resulted in increased binding of monocytes on fibrinogen but not on bovine serum albumin. When PKC activity was reduced through prolonged incubation with PMA for 16h, a significant reduction of monocyte adhesion on fibrinogen was observed. Peptides containing RGD sequences, which have been demonstrated to be ligands for certain integrins, did not inhibit monocyte adhesion. The data suggest that fibrinogen promotes monocyte adhesion in vitro by a PKC-dependent mechanism. PKC appears to be important not only for the initial cell adhesion but also for sustained binding of monocytes to fibrinogen.Abbreviations BSA Bovine serum albumin - ECM Extracellular matrix - PKC Protein kinase C - PMA Phorbol myristate acetate  相似文献   
4.
In 15 cases of 350 consecutive coronary angioplasties conventional low profile balloon catheters did not traverse the stenosis or occlusion over the guide-wire. A balloon on a wire device ("Microprobe", 2 mm) passed the stenosis or occlusion easily with a good primary result in 14 cases. The angioplasty procedure could then be completed with a larger standard balloon catheter. Use of the balloon on a wire device expands the technical facilities of angioplasty and increases the primary success rate in technically difficult cases.  相似文献   
5.
Summary The temporal development of infarcts was histochemically and functionally determined in porcine hearts. In one series of experiments (22 pigs), the distal third of the left anterior descending coronary artery (LAD) was transiently occluded for periods between 20 and 90 min and was reperfused for another 24h. At the end of the experiments, the infarcted myocardium of four tissue slices was determined with a tetrazolium stain and related to the risk region which was delineated by a fluorescent dye. Infarcts started to develop in the ischemic septum and the subendocardial layer of the free anterior wall between 20 and 35 min of ischemia. Thereafter, infarctions progressed rapidly from the inner towards the outer layer at risk. The jeopardized anterior left ventricular wall became almost completely infarcted within 60 min of ischemia. In a second series of experiments (10 pigs) recovery of systolic shortening was studied with implanted ultrasonic crystals over 3 weeks of reperfusion. At the end of the experiments, systolic shortening was about 75% of baseline level when ischemia had lasted between 20 and 35 min. Almost no recovery was observed when the occlusion time lasted 45 to 60 min. This study suggests that the assessment of myocardial infarction with a tetrazolium stain after 24 h of reperfusion corresponds very well with functional recovery after 3 weeks of reperfusion. Furthermore, determination of regional myocardial function of the ischemic, reperfused segment in the chronic stage may be considered an additional tool to evaluate therapeutic effects on infarct size in this model.The study was supported by a grant of Deutsche Forschungsgemeinschaft (DFG) Sonderforschungsbereich 330 Organprotektion Göttingen.This paper contains parts of the Habilitationsschrift of Dr. H. H. Klein.  相似文献   
6.
Taste buds are chemosensory endorgans consisting of modified epithelial cells. Fish and other vertebrates use their taste bud cells to sample potential food, either selecting or rejecting substances according to their edibility. The adult gustatory system in fish has been studied thoroughly, including regeneration experiments. Taste buds occur in the epithelia of the lips, the mouth cavity, the oropharyngeal cavity, and also in the skin of the barbels, the head, and sometimes even all over the body surface. Despite its importance for feeding, little is known about the ontogeny of the fish taste system. We examined the development of taste buds in the zebrafish on the light microscopical and the scanning and transmission electron microscopical levels. Taste buds develop later than the olfactory organ and the solitary chemosensory cells, two other chemosensory systems in aquatic vertebrates. The first few taste bud primordia are visible within the epithelia of lips and gill arches 3 to 4 days after fertilization, and the first few taste buds with open receptor areas appear on the lips and simultaneously on the gill arches 4-5 days after fertilization, which coincides with the onset of feeding. Taste buds in the mouth cavity, on the head, and on the barbels are formed later in development. As seen in other fish, zebrafish taste buds contain elongate dark and light cells, termed according to their electron density. Dark cells with a cell apex of many short microvilli appear first, followed by the light cells with one large microvillus. In addition, the zebrafish has a third fusiform cell type, which appears last. This cell type is low in electron density and has a brush-like apical ending with several small microvilli. This cell type has not been described previously. Furthermore, in zebrafish, the ontogenetic processes of taste bud formation differ from regenerative processes described in the literature.  相似文献   
7.
Free electron lasers (FELs) allow the generation of electromagnetic radiation (EM) in a wide field of frequencies (respectively wavelengths) through the proper adjustment of the energy of an electron beam and the field configuration of a magnetic undulator passed by this beam. Terahertz (THz) radiation covers the region of the electromagnetic spectrum between approximately 0.3 and 30 THz and thus can be considered a continuation of the optical spectrum beyond the far infrared (IR). The very interesting results obtained from various studies of the interaction between IR radiation and biomolecules or tissue have stimulated increasing interest in the study of biological systems using THz radiation. This paper points out what role modern FELs can play in this research.  相似文献   
8.
Summary The hypothesis that different receptor sites for algesic agents exist at free nerve endings in skeletal muscle has been tested by administering bradykinin and 5-hydroxytryptamine (5-HT) repeatedly in anaesthetized cats and evaluating the response behaviour of single group IV afferent units from the gastrocnemius-soleus muscle.Repeated intraarterial administration of bradykinin at intervals of 1 and 2 min usually elicited fibre responses without tachyphylaxis. Injections of equieffective doses of 5-HT, however, given in the same manner evoked fibre reactions that were strongly tachyphylactic. In units responding to both bradykinin and 5-HT a refractoriness to 5-HT could be induced by repeated injections of this agent without impairing the stimulating potency of bradykinin on the same nerve ending. Such a lack of cross-tachyphylaxis seems to apply also to the effects of histamine on one side and bradykinin or 5-HT on the other.These findings suggest that bradykinin, 5-HT and probably histamine exert their excitatory action on muscular group IV afferent units via different receptor sites.  相似文献   
9.
STUDY OBJECTIVES: The prostaglandin D system plays an important role in animal sleep. In humans, alterations in the prostaglandin D system have been found in diseases exhibiting sleep disturbances as a prominent symptom, such as trypanosoma infection, systemic mastocytosis, bacterial meningitis, major depression, or obstructive sleep apnea. Assessment of this system's activity in relation to human physiologic sleep was the target of the present study. DESIGN: Serum concentrations of lipocalin-type prostaglandin D synthase (L-PGDS, former beta-trace), and plasma levels of the pineal hormone melatonin were measured in 20 healthy humans (10 women, 10 men; aged: 23.3 +/- 2.39 years) at 4-hour intervals over a period of 5 days and nights, which included physiologic sleep, rapid eye movement sleep deprivation, and total sleep deprivation. In addition, the serum L-PGDS and plasma melatonin levels of 6 subjects were determined under conditions of bright white (10,000 lux) or dark red light (< 50 lux) in a crossover design during total sleep deprivation. Nocturnal blood sampling was performed by a through-the-wall tube system. L-PGDS was measured by an automated immunonephelometric assay, and melatonin was analyzed by direct radioimmunoassay. RESULTS: Serum L-PGDS concentrations showed marked time-dependent changes with evening increases and the highest values at night (P < .0005). This nocturnal increase was suppressed during total sleep deprivation (P < .05), independent of external light conditions and melatonin secretion. Rapid eye movement sleep deprivation had no impact on circulating L-PGDS levels. CONCLUSIONS: The circadian L-PGDS pattern and its suppression by total sleep deprivation indicate an interaction of the prostaglandin D system and human sleep regulation. L-PGDS measurements may well provide new insights into physiologic and pathologic sleep regulation in humans.  相似文献   
10.
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