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   2225108篇
  免费   159979篇
  国内免费   3543篇
耳鼻咽喉   32133篇
儿科学   68993篇
妇产科学   58425篇
基础医学   316190篇
口腔科学   64913篇
临床医学   189004篇
内科学   445563篇
皮肤病学   48948篇
神经病学   174610篇
特种医学   85529篇
外国民族医学   727篇
外科学   343271篇
综合类   42974篇
现状与发展   2篇
一般理论   617篇
预防医学   167875篇
眼科学   50893篇
药学   169228篇
  5篇
中国医学   4992篇
肿瘤学   123738篇
  2019年   17247篇
  2018年   26147篇
  2017年   19166篇
  2016年   20801篇
  2015年   23448篇
  2014年   31345篇
  2013年   47402篇
  2012年   67369篇
  2011年   70953篇
  2010年   41153篇
  2009年   37725篇
  2008年   66495篇
  2007年   70885篇
  2006年   71068篇
  2005年   68890篇
  2004年   66404篇
  2003年   64016篇
  2002年   62487篇
  2001年   111941篇
  2000年   116539篇
  1999年   98053篇
  1998年   24615篇
  1997年   21845篇
  1996年   22270篇
  1995年   20922篇
  1994年   19567篇
  1993年   18059篇
  1992年   75356篇
  1991年   72963篇
  1990年   70746篇
  1989年   68014篇
  1988年   62432篇
  1987年   61085篇
  1986年   57081篇
  1985年   54781篇
  1984年   40099篇
  1983年   33856篇
  1982年   18674篇
  1981年   16697篇
  1979年   35957篇
  1978年   24541篇
  1977年   21126篇
  1976年   19119篇
  1975年   20936篇
  1974年   24872篇
  1973年   23845篇
  1972年   22263篇
  1971年   20696篇
  1970年   19577篇
  1969年   18154篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
We report on the case of a 6-year-old girl admitted as an emergency with an acute abdomen with the diagnosis of peritonitis; clinical examination under anesthesia revealed the presence of an abdomino-pelvic mass. Laparotomy confirmed the diagnosis of torsion of an ectopic spleen. Splenectomy was required because the spleen was gangrenous. A review of the literature from 1896 to 1990 revealed reports of 74 cases. Epidemiology, etiology, pathophysiology, the diagnostic and therapeutic problems are discussed.
Ektopische Milz beim Kind: Fallbericht und Literaturübersicht 1896–1990
Zusammenfassung Anhand eines Fallberichtes und einer Literaturübersicht über 74 Fälle werden Epidemiologie, Ätiologie, Pathophysiologie, Diagnostik und Therapie der im Kindesalter sehr seltenen ektopen Milz besprochen. Die klinischen Zeichen reichen von unspezifischen abdominellen Beschwerden bis hin zum Vollbild eines akuten Abdomen (50%). Die praeoperative Diagnostik richtet sich nach Klinik, Abdomenleeraufnahme und Sonographie, evtl. Computertomographie. Aufgrund der hohen Torsionsraten besteht generell eine Operationsindikation, wobei die Entscheidung über Splenopexie oder Splenektomie sich an dem Lokalbefund orientieren sollte. Zur Splenopexie wurden mehrere Techniken mit gleich guten Resultaten angegeben.
  相似文献   
932.
We studied the number and affinity of catecholamine receptors in SD rat kidney by radioreceptor technique. The following conclusions were obtained: 1) By using 3H-prazosin, the numbers of alpha 1-receptor (Bmax) in rat renal cortex were greater than those in rat kidney medulla. As for affinity (Kd), the significance was not recognized between the two. Bmax of the rat renal cortex to 3H-prazosin binding was 96.1 fmol/mg protein, and Kd was 0.17 nM, and for the rat renal medullar these values were 44.5 fmol/mg protein and 0.13 nM, respectively. 2) By measurement of D1-receptor using 3H-SKF38393 in the rat renal cortex in the Scatchard plot analysis, positive cooperativity was observed under the low concentration of hot ligand which was less than 1 nM. But at the concentration of hot ligand over 1 nM, the plots showed a straight line. Bmax of the rat renal cortex to 3H-SKF38393 was 2.5 pmol/mg protein and Kd was 5.3 nM. 3) Based on displacement by dopamine for 3H-prazosin binding to rat renal cortex, it was surmised that high concentration of dopamine had an affinity to alpha 1-adrenoceptors. 4) There was no change in the Kd and Bmax of alpha 1-receptor in the rat renal cortex after incubation of samples with low concentration of dopamine. However, in the case of high concentration of dopamine, a remarkable decrease of the affinity (Kd) of alpha 1-adrenoceptor was observed.  相似文献   
933.
A study was carried out in order to document any abnormalities in the electro-encephalogram (EEG) that might appear in young adolescents who have deliberately inhaled the range of volatile substances loosely referred to as 'glue'. The EEGs of a group of 'street children' being assisted in a Johannesburg shelter were examined. The records were analysed for any clinical abnormalities and also subjected to spectral analysis in order to examine the overall characteristics of frequency, power and spatial distribution. The EEGs clearly revealed that, although at the time of the examination the subjects were ostensibly abstinent, both clinical and normative evidence of continuing brain disturbance was present. It was concluded that glue sniffing is likely to have long term electrocerebral sequelae.  相似文献   
934.
The results of the in vitro fertilisation programme at Tygerberg Hospital for the period April 1983 to January 1988 are presented. Of the 1117 laparoscopies performed, 825 patients reached the transfer stage. A live-birth rate of 9.3% was achieved. The pregnancy rate after transfer of 4 embryos was 25.9% compared with 15.4% after 2 embryos and 10.8% after 3 embryos (P = less than 0.0001). The multiple pregnancy rate was 2.8% in the group receiving 2 embryos and 11.7% and 10.4% in those receiving 3 and 4 embryos, respectively. Of the 77 successful pregnancies (90 babies), 1 baby died at 34 weeks' gestation as the result of abruptio placentae due to preeclampsia and 1 cot death occurred. The only congenital abnormality encountered was a cleft palate.  相似文献   
935.
936.
ABSTRACT. This paper describes the method and results of a survey of aggressive behaviour amongst people with learning difficulties. The study was confined to a single health district in the South Western Region of the UK with a general population of about 370000. At the time of the survey, the Handicap Register for the district recorded 1362 people as having a learning difFiculty. The overall prevalence of aggressive behaviour amongst people with learning difficulties for whom base population data was available was 17.6%. The lowest rate was identified amongst day facilities (9.7 %) and the highest in hospitals within the district (38.2%). The prevalence rate amongst those attending schools for children with severe learning difSculties was 12.6%. Proportionately more males than females were reported to present problems of aggressive behaviour. The gender difference appeared to be largely accounted for by the disproportionate number of men identified within day facilities. There was no significant evidence of an association between the person's gender and the presence aggressive behaviour within schools or hospitals. The results indicated that, although physical and verbal aggression were the most frequently reponed behaviours, many of the sample were also said to engage in other forms of challenging behaviour, particularly self-injurious, ritualistic, stereotypical and withdrawn behaviour. The risk of a serious or very serious injury to another person was very low; 0.7% or six people with learning difiSculties firom the district were reponed to be currently presenting such a risk. Similarly, only 2% of the base population (n=18) were reponed to be extremely difficult to manage. The implications of the findings are discussed.  相似文献   
937.
Corpus cavernosography in a patient with erectile dysfunction revealed absence of communication between the 2 cavernous bodies. No similar case was found in a review of 100 consecutive cavernosograms or in the literature. The abnormality may be a source of error in pressure recordings or in intravenous injection of pharmaceutical agents.  相似文献   
938.
Gallstone dissolution   总被引:2,自引:0,他引:2  
Many methods are available for gallstone dissolution, including oral bile salts; cholesterol solvents such as mono-octanoin or methyl tert-butyl either; and calcium or pigment solvents such as EDTA and polysorbate. Which of these approaches will be appropriate for an individual patient depends on the type of stones; whether they are in the gallbladder or the bile ducts; whether access to the biliary tree is available; the patient's age and general medical condition; and the availability of necessary expertise. In the US, both chenodeoxycholate and ursodeoxycholate are now available. Ursodeoxycholate is more expensive but appears to produce fewer side effects and may be more efficacious. These agents are most effective in thin women with small floating, radiolucent cholesterol stones in a functioning gallbladder. Only about half of the small subset of patients will experience partial or complete dissolution of stones within a year. Stone recurrence and the potential toxicity of long-term therapy are problems with this approach. Therefore, for most patients, cholecystectomy, either in the traditional fashion or using a laparoscopic approach (see article later in this issue by Gadacz et al), is the most cost-effective and perhaps the safest option. Intragallbladder instillation of methyl tert-butyl ether probably will be applicable only to a small subset of patients, and treatment is likely to be followed by a high recurrence rate. In patients with retained common duct cholesterol stones and access to the biliary tree, mono-octanoin therapy is advantageous in that it can be initiated as soon as cholangiography demonstrates no extravasation. In properly selected patients, a 90% success rate with this technique can be expected within 7 days.  相似文献   
939.
G Nichol  A Nix  P J Barnes    K F Chung 《Thorax》1990,45(9):694-698
The effect of inhaled prostaglandin (PG) F2 alpha on the response to the inhaled tussive agent capsaicin was investigated in normal subjects. Seven subjects inhaled three breaths of four doses of capsaicin (0.3, 0.6, 1.2, and 2.4 nmol) before and immediately after inhaling PGF2 alpha (0.1 mumol) or placebo (0.15M NaCl) on separate days. The numbers of capsaicin induced coughs were greater after PGF2 alpha (mean 42.3 coughs) than after 0.15M sodium chloride (30.1). Visual analogue scores (0-10 on a 10 cm continuous scale) showed that capsaicin was more irritant after PGF2 alpha than after saline. Total respiratory resistance (Rrs), measured by the forced oscillation technique, was unaltered throughout the study. A double blind, placebo controlled study of the effects of inhaled salbutamol (200 micrograms, 0.6 mumol) and ipratropium bromide (40 micrograms, 0.1 mumol) on cough induced by capsaicin (2.4 nmol) and by PGF2 alpha (0.1 mumol) and on PGF2 alpha augmented, capsaicin induced coughing was performed in seven subjects. Neither drug had any effect on capsaicin induced coughing. Salbutamol reduced coughing due to PGF2 alpha (mean 7.7 coughs after salbutamol, 9.3 after placebo) but ipratropium bromide did not (mean 6.9 coughs after ipratropium bromide, 6.6 after placebo). Salbutamol also inhibited the augmentation of the capsaicin induced cough that followed inhalation of PGF2 alpha (mean augmentation 1.9 coughs after salbutamol, 4.1 after placebo), whereas ipratropium bromide did not (augmentation 1.7 coughs after ipratropium bromide, 2.7 after placebo). No changes in Rrs were seen after PGF2 alpha or either drug. Thus salbutamol reduces PGF2 alpha induced cough and the augmentation of capsaicin induced cough that follows PGF2 alpha.  相似文献   
940.
The fate of skin allografts exchanged among heterozygous and homozygous gynogenetic common carp siblings, and among newly developed inbred strains and F1 hybrids, is described. Heterozygous gynogenetic offspring were produced by fertilizing eggs with UV-irradiated sperm and by treating the resulting zygote with a cold shock (0 degree C, 45 min). The temperature shock causes retention of the second polar body, which allows the eggs to develop into normal diploid fry. Homozygous gynogenetic offspring were similarly produced by using a heat shock (40 degrees C, 2 min), which suppresses the first mitotic division. Skin allografts exchanged among heterozygous gynogenetic carp exhibited prolonged survival, with some allografts (21.8%) surviving for over 28 days. Furthermore, a strong histocompatibility locus was seen to segregate in this group. In contrast, skin allografts exchanged among homozygous gynogenetic siblings were all rejected within 14 days (MST 9.4 days). New homozygous inbred strains, designated JJ and MM, were produced by gynogenetic reproduction of homozygous female carps, while F1 hybrids were produced by crossing of these homozygous females with homozygous male siblings. All grafts exchanged among members of the same strain were permanently accepted. Likewise grafts from homozygous strain members were accepted by fish from the related F1-hybrids, while the reverse grafts were rejected. These results provide evidence for the idea that in the carp histocompatibility genes exist at least one major locus and multiple minor loci, which are codominantly expressed.  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