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   34252篇
  免费   2487篇
  国内免费   123篇
耳鼻咽喉   396篇
儿科学   840篇
妇产科学   765篇
基础医学   4699篇
口腔科学   549篇
临床医学   3257篇
内科学   8000篇
皮肤病学   616篇
神经病学   3767篇
特种医学   1291篇
外国民族医学   4篇
外科学   5557篇
综合类   398篇
一般理论   9篇
预防医学   1976篇
眼科学   486篇
药学   2274篇
中国医学   95篇
肿瘤学   1883篇
  2022年   232篇
  2021年   505篇
  2020年   308篇
  2019年   530篇
  2018年   647篇
  2017年   495篇
  2016年   558篇
  2015年   720篇
  2014年   930篇
  2013年   1264篇
  2012年   1935篇
  2011年   2043篇
  2010年   1269篇
  2009年   1117篇
  2008年   1915篇
  2007年   2014篇
  2006年   1877篇
  2005年   1946篇
  2004年   1896篇
  2003年   1918篇
  2002年   1809篇
  2001年   686篇
  2000年   656篇
  1999年   651篇
  1998年   502篇
  1997年   415篇
  1996年   372篇
  1995年   366篇
  1994年   308篇
  1993年   331篇
  1992年   489篇
  1991年   468篇
  1990年   406篇
  1989年   410篇
  1988年   405篇
  1987年   401篇
  1986年   399篇
  1985年   325篇
  1984年   324篇
  1983年   291篇
  1982年   225篇
  1981年   192篇
  1980年   179篇
  1979年   239篇
  1978年   145篇
  1977年   169篇
  1975年   131篇
  1974年   148篇
  1973年   165篇
  1972年   133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Abstract: Three phospholipase A2 (PLA2s), OS1 and OS1 purified from the taipan snake venom Oxyuranus scutellatus scutellatus and bee venom PLA2 were injected to rats by the intracerebroventricular route. OS1 showed no sign of neurotoxicity at doses at which OS2 and bee venom PLA2 produced multiform dose-dependent behavioural effects including motor disturbances (stereotyped movements), compulsive scratching, convulsions and breathing difficulties. EEG recordings showed at the very time when the animal was motionless the induction of several episodes of a low frequency hippocampal theta rhythm, index of long-term changes in synaptic neuroplasticity. Spike-wave discharges were also produced but the occurrence was not systematic. These seizures were often accompanied with behavioural convulsions. Blockers of NMDA receptors and drugs modifying the GABAergic transmission could not abolish the neurotoxic effects of PLA2s except for diazepam (10 mg/kg intraperitoneally) that prevented only OS2-induced disturbances. Blockers of L-type Ca2+ channels and K+ channel openers were also without effect. The toxicity of OS2 and bee venom PLA2 is probably due to their initial specific binding to their neuronal receptor sites.  相似文献   
132.
Although negative symptoms were traditionally considered to be unresponsive to neuroleptic medication, recent studies have demonstrated that negative symptoms do improve during neuroleptic treatment and that such improvement tends to occur concurrently with improvement in positive symptoms. Clozapine is an atypical neuroleptic that is effective in a significant proportion of otherwise neuroleptic-nonresponsive schizophrenic patients; in contrast to conventional neuroleptics, clozapine is also purported to possess unique efficacy in the amelioration of negative symptoms. How clozapine-associated reduction in negative symptoms relates to change in positive symptoms is not clear. To study the relationship between change in positive and negative symptoms during clozapine treatment, we monitored symptomatology in 40 DSM-III-R schizophrenic patients before and about 8 weeks after a trial of clozapine. Both positive and negative symptoms improved significantly. There was a significant correlation (r = .63,p <.01) between change in positive symptoms and change in negative symptoms; as with conventional neuroleptics, negative symptoms improved concomitantly with positive symptoms during clozapine treatment. Clozapine's apparent greater efficacy on negative symptoms may be related to its greater efficacy on positive symptoms in otherwise neuroleptic-refractory patients and its lesser propensity to cause extrapyramidal side-effects.  相似文献   
133.
A case of hyperreactio luteinalis in an otherwise normal pregnancy is reported. Ascites was present, but no peritoneal implants or adenopathy were seen. Findings that would have suggested the correct diagnosis are the symmetrical and bilateral pattern of the mass, as well as the rather uniform size of the loculi, which were 1 to 3 cm in diameter.  相似文献   
134.
Summary Goal of Surgery Stable internal fixation of extraarticular proximal humeral fractures. Indications Extraarticular fractures angulated more than 30° which can be reduced closely or through a small incision. Epiphysiolysis. Fracture-dislocation of the humeral head. Contraindications Pathological fractures. Four part fractures. Segmental fractures of the humerus. Positioning and Anaesthesia Supine; the affected shoulder overhanging the edge of the table and supported by a radiolucent board. General or regional anaesthesia. Surgical Technique Closed pinning of two part and certain three part fractures of the proximal humerus being displaced, unstable, and mainly at the metaphyseal level. Introduction of Kirschner wires through a diaphyseal window and advancement into the proximal fragments after reduction which is controlled by image intensification. Postoperative Management Temporary immobilization in a sling. Passive and active assisted movements after a few days. Active movements after 2 weeks. Removal of wires after 3 months. Possible Complications Fracture of the humerus at the site of the cortical window. Injury to the radial nerve. Results 32 patients, mean age 49 years, 30 two part fractures and 2 three part fractures. Number of Kirschner wires used: 3 to 6, mean 4. Two out of 3 patients complained of pain at the site of wire insertion. All fractures consolidated. No avascular necrosis nor infection. Complications: Partial loss of internal fixation in 3 patients. One fracture of the humeral shaft. Sympathetic reflex dystrophy in 3 patients. Half of the patients had a normal range of motion. Time of follow-up: 6 to 24 (mean 10) months. Division of Orthopaedics and Traumatology, Purpan Hospital, Toulouse, France.  相似文献   
135.
136.
The myocardial uptake of fatty acids labeled with radioactive iodine and injected i.v. can only be evaluated with SPECT if their oxidation kinetics is slow enough. For this reason, we evaluated different iodomethylated fatty acids in mice and dogs to determine which of them shows the highest myocardial uptake and the slowest oxidation. The most suitable was found to be 16-iodo-3-methyl hexadecanoic acid (mono ) since its myocardial fixation was the same as that of the reference, i.e. 16-iodo-9-hexadecenoic acid (IHA), whereas it was degraded more slowly. Thirty min after injection of mono into dogs, the decrease in myocardial activity with respect to the maximum was two fold less than after IHA injection. The myocardial uptake of the two dimethylated fatty acids studied, i.e. 16-iodo-2,2-methyl hexadecanoic acid and 16-iodo-3,3-methyl hexadecanoic acid, was less than that of IHA in mice and dogs. In the latter, the myocardial uptake was so small that we were unable to study the time course of its activity. Consequently, these dimethylated fatty acids are not suitable for the study of the myocardial uptake of fatty acids in man.  相似文献   
137.
A new computed tomographic and sonographic appearance of renal metastatic melanoma is described. Bilateral cystic masses with thick walls, many with mural nodules, were noted. Sonography also demonstrated complex echopenic masses with irregularly thickened walls and mural nodules.  相似文献   
138.
Our work concerned 15 patients (9 males, 6 females) with a mean age of 29.5 years, having a hematologic malignant disease and undergoing allogenic bone marrow transplantation.We studied :
1. The metabolic disorders induced by the conditioning regimen (chemotherapy and total body irradiation) pregraft accompanying cytolysis (day −7, −5, −2).
2. The corrective effect of a total parenteral nutrition introduced 2 days before the transplantation and pursued during 30 days post-graft (day −2 to day 30).
3. The interest of a high calorie intake (BEE × 2) and, after randomisation, of a variable nitrogen intake (24% of the total calorie intake for group A [8 patients] and 14% for group B [7 patients]). The patient characteristics of these two groups were closely comparable. Urinary parameters were studied daily (3-methylhistidine, cratinine, nitrogen) and blood parameters weekly (transferrin, pre-albumin, albumin, retinol binding protein).
We observed globally :
-- An excellent result of the nutritional support without significant weight loss;
-- protein catabolism stopped with a recovery of synthesis of RBP after day 7 and pre-albumin from day 7;
-- a decrease in muscle catabolism.
The randomized study showed :
-- a significant difference in nitrogen excretion between group A and group B;
-- earlier and better protein synthesis recovery in group A, particularly with regard to RBP and pre-albumin.
In conclusion, we recommend for the patients undergoing bone marrow transplantation :
-- nutritional support should be introduced before the conditioning regimen;
-- a high calorie intake (BEE × 2) with a nitrogen intake between 14% and 24% of the total calorie intake;
-- cyclic parenteral nutrition should be pursued during the second and third month post-graft.

Résumé

Nous avons étudié chez 15 malades (9 hommes, 6 femmes) d'âge moyen 29,5 ans, présentant une hémopathie maligne et nécessitant une greffe de moelle osseuse allogénique :
1. Les désordres métaboliques induits par la chimiothérapie et l'irradiation corporelle totale en période de prégreffe au cours de la cytolyse (J −7, J −5, J −2).
2. L'effet correcteur d'une nutrition parentérale introduite deux jours avant la greffe et exclusive durant les 30 jours post-greffe (J −2, J + 30).
3. L'intérêt d'un apport calorique élevé (BEE × 2) et, par randomisation, d'un apport azoté variable (24 % de l'apport calorique total pour le groupe A et 14 % pour le groupe B).
Nous avons étudié quotidiennement certains paramètres urinaires (3MeH, créatinine, azote) et les paramètres sanguins (transferrine, préalbumine, albumine, RBP) l'ont été de façon hebdomadaire.Nous avons constaté globalement un excellent résultat du support nutritif sans perte de poids significative, un arrêt du processus catabolique protéique avec reprise de synthèse après J +7 pour la RBP et pour la préalbumine et une réduction du catabolisme musculaire.L'étude randomisée a mis en évidence :
-- une différence statistique dans l'excrétion axotée, plus intense dans le groupe A,
-- une reprise des synthèses protéiques, plus précoce et plus performante dans ce même groupe pour la RBP et la préalbumine.
En conclusion et compte tenu de l'ensemble des éléments, nous préconisons chez ces malades devant subir une greffe de moelle osseuse allogénique :
-- une attitude préventive en ce qui concerne la nutrition à débuter avant le conditionnement,
-- un apport calorique élevé (BEE × 2) et un apport azoté situé entre 14 % et 24 % de l'apport calorique total,
-- une étude prospective quant à l'intérêt de certains acides aminés et d'une nutrition parentérale cyclique poursuivie au 2e et au 3e mois post-greffe.
Mots clés: greffe de moelle osseuse; nutrition parentérale totale; apport azotéKey-words: bone marrow transplantation; total parenteral nutrition; nitrogen intake  相似文献   
139.
This study describes our experience using a percutaneously placed small-bore catheter for drainage of malignant pleural effusions and subsequent instillation of a sclerosing agent to obliterate the pleural space. We treated 15 consecutive patients with known metastatic cancer and a symptomatic pleural effusion. Twelve patients survived for more than four weeks after the procedure; 11 of these 12 patients had a successful objective clinical response. The procedure was well tolerated, with little or no discomfort during catheter placement and the maintenance period. No serious complications were encountered. We conclude that the use of a small-bore percutaneously placed "pneumothorax" catheter in the management of malignant pleural effusions is an effective and more comfortable alternative to large-bore closed-tube thoracostomy.  相似文献   
140.
In 1987 Medicare benefits for the mentally ill were expanded for the first time in 22 years. A major change was the removal of limits and copayments for the "medical management of psychopharmacologic agents." Payment for medical management recognizes the trend toward the remedicalization of psychiatry; however, medical management can be defined either broadly or narrowly. The authors suggest pricing strategies for both medical management of mental disorders and psychotherapy. Enlightened design of psychiatric benefits will cover all forms of treatment according to appropriate rules. Access to treatment for mental illness is at stake as these rules develop.  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