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   24918篇
  免费   1957篇
  国内免费   102篇
耳鼻咽喉   293篇
儿科学   732篇
妇产科学   459篇
基础医学   2820篇
口腔科学   485篇
临床医学   2571篇
内科学   5437篇
皮肤病学   400篇
神经病学   2402篇
特种医学   749篇
外国民族医学   2篇
外科学   3900篇
综合类   563篇
一般理论   26篇
预防医学   2129篇
眼科学   655篇
药学   1632篇
中国医学   34篇
肿瘤学   1688篇
  2022年   201篇
  2021年   441篇
  2020年   267篇
  2019年   421篇
  2018年   463篇
  2017年   348篇
  2016年   337篇
  2015年   455篇
  2014年   620篇
  2013年   963篇
  2012年   1412篇
  2011年   1392篇
  2010年   824篇
  2009年   729篇
  2008年   1281篇
  2007年   1398篇
  2006年   1415篇
  2005年   1404篇
  2004年   1323篇
  2003年   1247篇
  2002年   1204篇
  2001年   384篇
  2000年   339篇
  1999年   374篇
  1998年   300篇
  1997年   252篇
  1996年   261篇
  1995年   212篇
  1994年   184篇
  1993年   174篇
  1992年   268篇
  1991年   228篇
  1990年   268篇
  1989年   204篇
  1988年   231篇
  1987年   218篇
  1986年   207篇
  1985年   205篇
  1984年   222篇
  1983年   220篇
  1982年   226篇
  1981年   211篇
  1980年   219篇
  1979年   213篇
  1978年   171篇
  1977年   140篇
  1976年   146篇
  1975年   129篇
  1974年   156篇
  1973年   135篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
Metabolic alterations in immature rabbit joint tissues were examined following in vitro and in vivo exposure to the alkylating agents Thiotepa and nitrogen mustard. Brief exposure in vitro to either agent resulted in marked suppression of incorporation of radiolabeled precursors of protein, RNA, and glycosaminoglycan synthesis in articular cartilage, which was partially reversible after Thiotepa exposure. In vivo, nitrogen mustard had little effect on synovium and transient inhibitory effects on cartilage vital processes, whereas Thiotepa caused a prolonged inhibition of synovial metabolism with little effect on cartilage. Autoradiographic localization of labeled agents indicated that synovial tissue and cartilage were readily penetrated by nitrogen mustard, but only a few synovial lining cells and superficial chondrocytes were labeled with 35S-Thiotepa. Furthermore, trypsin significantly reduced labeling of cartilage with 14C-nitrogen mustard. These data suggest that alkylating agents differentially affect metabolic processes in joint tissues in vivo and that with Thiotepa, this interference occurs primarily in the synovium. The degree of interference is apparently dependent upon time of exposure to the agents and the relative DNA-RNA synthetic activity of the joint tissue.  相似文献   
962.
Periprosthetic fractures of the acetabulum are a rare but potentially disastrous complication of total hip arthroplasty. Such fractures occur either as early perioperative complications or late complications when they are associated with either significant trauma or as a result of the loss of the structural integrity of the bone supporting the prosthesis, such as aseptic osteolysis. The incidence of such fractures appears to be increasing with the increased use of uncemented acetabular components. This article explores the current literature on the epidemiology, etiology, and classification of periprosthetic acetabular fractures as well as offering potential treatment strategies.  相似文献   
963.
964.
Prenatal stress is considered as an early epigenetic factor able to induce long-lasting alterations in brain structures and functions. It is still unclear whether prenatal stress can induce long-lasting modifications in the hypothalamo-pituitary-adrenal axis. To test this possibility the effects of restraint stress in pregnant rats during the third week of gestation were investigated in the functional properties of the hypothalamo-pituitary-adrenal axis and hippocampal type I and type II corticosteroid receptors in the male offspring at 3, 21 and 90 days of age. Plasma corticosterone was significantly elevated in prenatally-stressed rats at 3 and 21 days after exposure to novelty. At 90 days of age, prenatally-stressed rats showed a longer duration of corticosterone secretion after exposure to novelty. No change was observed for type I and type II receptor densities 3 days after birth, but both receptor subtypes were decreased in the hippocampus of prenatally-stressed offspring at 21 and 90 days of life. These findings suggest that prenatal stress produces long term changes in the hypothalamo-pituitary-adrenal axis in the offspring.  相似文献   
965.
Effects of cholinergic stimulation on pituitary hormone release   总被引:1,自引:0,他引:1  
Physostigmine was infused into human volunteers to assess the effect of central cholinergic stimulation on memory and on neuroendocrine function. Methscopolamine bromide, a peripheral anticholinergic agent, was given simultaneously. The lower dose of physostigmine (1.0 mg) produced no change in AVP, cortisol, melatonin, GH or LH in those subjects without unpleasant cholinergic side effects. Larger doses of physostigmine usually produced nausea, and were associated with marked elevations of AVP, cortisol and prolactin, but no change in GH, LH or melatonin. Thus, cholinergic agents easily induce a stress response, but the GH component of this response can be suppressed by peripheral cholinergic blockade.  相似文献   
966.
New diagnostic criteria for multiple sclerosis integrating magnetic resonance image assessment with clinical and other paraclinical methods were introduced in 2001. The "McDonald Criteria" have been extensively assessed and used since 2001. New evidence and consensus now strengthen the role of these criteria in the multiple sclerosis diagnostic workup to demonstrate dissemination of lesions in time, to clarify the use of spinal cord lesions, and to simplify diagnosis of primary progressive disease. The 2005 Revisions to the McDonald Diagnostic Criteria for MS should simplify and speed diagnosis, whereas maintaining adequate sensitivity and specificity.  相似文献   
967.
Recovery of D1- and D2-dopamine receptors in Wistar rat corpora striata were assessed following N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ blockade). Absolute recovery declines during senescence approximately 25 and 40% for the D1- and D2-subtypes, respectively. Net biosynthetic reductions are comparable to the overall age-related decreases in receptor concentrations for this rat strain. EEDQ administration also induces catalepsy behavior and impairs ability of animals to remain on an inclined screen. Recovery of inclined screen performance is also reduced with age, but is not strictly proportional to recovery of receptor concentrations.  相似文献   
968.
The effects of norepinephrine microinjected into the anterior hypothalamus were examined in feline affective defense behavior elicited by electrical stimulation of the region of the ventromedial nucleus. Anterior hypothalamic sites from which affective defense behavior could also be elicited by electrical stimulation and which are known to receive inputs from both the ventromedial nucleus and brainstem noradrenergic neurons were selected for pharmacological analysis. Intracerebral injections of 250 ng (1 nM) and 500 ng (2 nM) quantities of norepinephrine placed into the anterior hypothalamus resulted in a significant lowering of the attack thresholds. These reductions in response thresholds which were reversed by either pre- or post-treatment with yohimbine, indicate that the noradrenergic system may play an important role in the regulation of affective defense behavior.  相似文献   
969.
Carbamylcholine stimulated [3H]inositol phosphate accumulation in mouse cerebral cortical slices with an ED50 value of approximately 70 μM. Increasing concentrations of the M2 selective muscarinic cholinergic receptor antagonist, AF-DX 116 (0.3–3.0 μM), produced parallel shifts to the right for concentration-response curves to carbamylcholine. A pA2 value for AF-DX 116 of 6.5 (low affinity) was obtained frommSchild plot analysis. It is concluded that the M2 muscarinic receptor subtype, as defined by high affinity [3H]AF-DX 116 radioligand binding, is not appreciably coupled to polyphosphoinositide hydrolysis in the mouse cerebral cortex.  相似文献   
970.
Objective: To compare outcomes using a wheelchair back designed to support the natural seated spinal curves versus an upholstered back that promotes posterior pelvic tilt and thoracolumbar kyphosis.Design: Cross-over intervention.Setting: Two free-standing spinal cord injury (SCI) model system hospitals.Participants: Fifty adults with motor complete SCI C6-T4, between the ages of 18–60 years who use a manual wheelchair for mobility were recruited from a convenience sample.Intervention: Each participant’s wheelchair back support was removed and replaced by an upholstered back and a solid back in randomized order. Postural and functional outcomes, pain, and satisfaction were evaluated using each back.Outcome measures: Seated postural measurements included pelvic angle, spinal angle of kyphosis and linear measurement of spine. Functional outcomes included vertical forward reach, one stroke push, timed forward wheeling, ramp ascent and descent. Numerical pain rating and a satisfaction survey provided input pertaining to both backs.Results: The solid back demonstrated significance in seated postural measurements. Participants using the solid back trended to higher scores in functional outcome measures including vertical forward reach, one stroke push and timed ramp ascent. Participants reported increased satisfaction with comfort and stability with the solid back.Conclusions: This pilot study demonstrated that a wheelchair back, which supports the seated spinal curves improves upright posture, functional reach, and wheelchair propulsion skills. Further research is necessary to demonstrate statistical findings as well as to assess back height and lateral support.  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