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   28546篇
  免费   2218篇
  国内免费   83篇
耳鼻咽喉   227篇
儿科学   698篇
妇产科学   625篇
基础医学   4128篇
口腔科学   389篇
临床医学   2941篇
内科学   5679篇
皮肤病学   322篇
神经病学   2658篇
特种医学   633篇
外国民族医学   3篇
外科学   3914篇
综合类   550篇
一般理论   45篇
预防医学   2564篇
眼科学   891篇
药学   2369篇
中国医学   37篇
肿瘤学   2174篇
  2023年   192篇
  2022年   267篇
  2021年   615篇
  2020年   394篇
  2019年   631篇
  2018年   630篇
  2017年   490篇
  2016年   591篇
  2015年   688篇
  2014年   973篇
  2013年   1436篇
  2012年   1996篇
  2011年   2117篇
  2010年   1201篇
  2009年   1045篇
  2008年   1754篇
  2007年   1886篇
  2006年   1944篇
  2005年   1942篇
  2004年   1890篇
  2003年   1643篇
  2002年   1510篇
  2001年   253篇
  2000年   199篇
  1999年   279篇
  1998年   352篇
  1997年   293篇
  1996年   279篇
  1995年   259篇
  1994年   207篇
  1993年   217篇
  1992年   173篇
  1991年   159篇
  1990年   142篇
  1989年   119篇
  1988年   122篇
  1987年   113篇
  1986年   105篇
  1985年   109篇
  1984年   122篇
  1983年   125篇
  1982年   136篇
  1981年   131篇
  1980年   102篇
  1979年   73篇
  1978年   80篇
  1977年   75篇
  1976年   74篇
  1974年   71篇
  1973年   64篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.
102.
When conservative management of intestinal obstruction fails, the surgeon has two operative choices for decompression: the open procedure with enterotomies and suction and the closed procedure consisting of retrograde stripping and nasogastric suction. A previously undocumented complication of the latter procedure — pulmonary aspiration — is reported in a 20-year-old man with small-bowel obstruction. Practical modifications to the technique of small-bowel decompression are suggested. They include feeding the nasogastric tube into the distal duodenum, using a wider bore tube, inserting an esophageal balloon before extubation, using a nasogastric tube with suction throughout extubation and, immediately postoperatively, making a more conscious effort to remove all gastric contents before extubation, and milking the contents distally through the ileocecal valve.  相似文献   
103.
Because hypothermia and anorexia were previously found to be more sensitive indices of the effects of lindane than were convulsions, these endpoints were used to quantify the ability of benzodiazepines (BDs) and phenytoin either to ameliorate or exacerbate the toxicity of lindane in the rat. After administration of lindane (40 or 50 mg/kg) in oil per os, toxicity was counteracted by phenytoin and the "central" BD agonists diazepam and clonazepam, but was worsened by Ro 5-4864 a "peripheral" BD agonist. Clonazepam and diazepam were each more effective in counteracting lindane-induced anorexia than in stimulating food intake, presumably because the animals had been fasted and probably even controls ate maximally when food was presented. Diazepam alone (3 injections in 1 day) produced withdrawal-induced decreased food intake the following day. Clonazepam and diazepam alone each transiently decreased colonic temperature, yet effectively blocked the more severe hypothermia produced by lindane. Ro 5-4864 by itself did not produce any measurable effects, yet exacerbated all of the effects, including lethal effects, of lindane. The present findings are compatible with other evidence that lindane and Ro 5-4864 act at the picrotoxinin receptor of the GABAA-activated chloride channel and that systemic administration of agents acting at this site may produce a constellation of effects, including seizures, hypothermia and anorexia.  相似文献   
104.
An audit was undertaken to determine how well a primary care team supported lay carers of the demented elderly. The following standards were set: (1) primary care teams should know of the existence of symptomatic demented elderly patients in the community; (2) lay carers should be knowledgeable about dementia; and (3) the resources which the lay carers felt they needed should be supplied unless they were unavailable.

The primary care team knew of the existence of all symptomatic demented elderly patients in the practice but lay carers lacked knowledge about dementia and had unmet needs. Giving lay carers a booklet about dementia and reporting their unmet needs to the primary care team led to improvements in standards 2 and 3. In addition, stress among lay carers was reduced. In spite of a reduction in the number of carers' unmet needs, there was no overall change in the use of available resources following intervention.

It is concluded that structured support is necessary and worthwhile in order to provide effective support for lay carers of the demented elderly in the practice.

  相似文献   
105.
Despite evidence of an interaction between cannabinoids and estrogen in the brain, little information is available regarding the consequences of this interaction on behavior. A within-subjects design was used to examine the effects of estrogen and delta9-tetrahydrocannabinol (delta9-THC) on learning and memory in ovariectomized rats responding under a multiple schedule of repeated acquisition and performance. Treatment with low physiological levels of estrogen, delivered in Silastic capsules, improved response accuracy without affecting response rate during acquisition. Estrogen also attenuated the ability of delta9-THC (0.56- 3.2 mg/kg) to decrease response accuracy and rate during acquisition and response accuracy during performance. Results indicate that estrogen can improve accuracy during acquisition of a nonspatial operant task and can attenuate delta9-THC- induced behavioral deficits.  相似文献   
106.
The cellular response within lesions and in draining lymph was examined in sheep following a primary intracutaneous injection of live or killedS. aureus. Microscopic examination of sections from liveS. aureus lesions (12, 24, 48, and 96 h following vaccination) revealed a high ratio of neutrophils to macrophages at all times. This ratio was initially high following inoculation of killedS. aureus but decreased steadily at successive sampling times. Representative sections from lesions were subjected to indirect immunofluorescent staining to identify IgM-, IgG1-, and IgG2-containing cells. The ratio of IgG2- to IgG1-containing cells in lesions produced following liveS. aureus vaccination was significantly greater than the ratio in lesions produced by killed staphylococci. Lesions induced by liveS. aureus recruited significantly greater numbers of51Cr-labeled allogeneic neutrophils from blood than did lesions induced by killedS. aureus. During the first 6 h this difference was approx. 20-fold. The volume of lymph and the number of leukocytes draining liveS. aureus lesions was considerably greater than from lesions produced by killed staphylococci. The proportion of neutrophils in lymph draining both types of lesions increased markedly during the first two days of the response but was observed to be greater and remained higher for a longer period of time in lymph draining vaccine lesions produced following injection of live staphylococci. The increase in proportion of neutrophils in lymph was accompanied by a concomitant decrease in proportion of lymphocytes and macrophages. No immunoglobulin-containing cells or anti-staphylococcal antibody production was detected in lymph draining either type of lesion. These differences in inflammatory responses may contribute to the documented differences in immune responses to live and killed staphylococcal vaccines.  相似文献   
107.
Three monoclonal antibodies (MoAbs L49-15, L81-11 and L238-14) were raised against recombinant human lymphotoxin (rLT) derived from E. coli containing the cDNA sequence specifying LT. MoAb L81-11 strongly neutralised the cytotoxicity of LT derived either from E. coli or the RPMI 1788 lymphoblastoid cell line, whilst the other two MoAbs were only weakly neutralising in this respect. L81-11 and L238-14 MoAbs bound to different antigenic determinants on the rLT molecule, but neither bound to other lymphokines such as the structurally related tumour necrosis factor (TNF). As such, these MoAbs were ideal reagents for immunoassay of LT and a very sensitive, highly specific immunoradiometric assay (IRMA) was developed. This assay was rapid to perform and was capable of detecting as little as 10 pg/ml of LT. Application of the LT IRMA in combination with previously developed human gamma-interferon (IFN-gamma) and human TNF-specific IRMA (Crane et al., 1985; Meager et al., 1987) permitted independent estimations of these three substances to be carried out in parallel. By these means, it was found that RPMI 1788 produced both LT and TNF, but not IFN-gamma. Extensive analyses on cytokine (monokine and lymphokine) preparations derived from a variety of activated lymphocytes are also reported. Co-production of LT, TNF and IFN-gamma was a common finding, even occurring in alloantigen-specific T helper cell clones.  相似文献   
108.
This paper describes how an age-sex register may be used as a sampling frame for the selection of matched controls in studies of the use of general practice. It discusses both the analysis of data collected in this way and the advantages and limitations of the method itself. The application of the method to a case-study suggests that patients who use hospital accident departments are also high users of general practice. Although care is needed in the interpretation of such results, it is concluded that matched controls can be used to ameliorate some of the problems of research in general practice.  相似文献   
109.
We present two cases of a thrombus in the ascending aorta causing an acute myocardial infarction (AMI) and review the 10 other cases previously reported in the literature. This life-threatening condition appears to be more common in female smokers in their fifth decade. Suspicion should be raised in individuals at low risk for atherosclerotic disease with coronary angiographic findings not in keeping with the clinical presentation. The diagnosis may be obtained by transesophageal echocardiography, and we generally recommend surgical thrombectomy.  相似文献   
110.
Two series of block copolymers have been synthesized comprising of soft polytrifluoroacetaldehyde (polyacetal) segments and of hard 4,4′-methylenedi(phenyl isocyanate)/cis-cyclohexane-1,4-diol polyurethane segments. The series-A copolymers in which the soft segments were directly bound to the hard segments had significantly lower thermal stability than the series-B copolymers in which the soft segments were linked to the hard segments by sebacic ester units. In both series the thermal stability decreased with increasing soft segment content. The series-A copolymers exhibited two thermal transitions both characteristic of Tg's and separated by about 60 K. In contrast the series-B copolymers exhibited two characteristic Tg's separated by 200–250 K, depending on composition, together with an additional endothermic transition at about ambient temperature. All transitions for both series decreased with increasing soft segment content. The observations have been compared with those of other polyether and polyester based polyurethanes.  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