全文获取类型
收费全文 | 868篇 |
免费 | 46篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 2篇 |
妇产科学 | 27篇 |
基础医学 | 113篇 |
口腔科学 | 2篇 |
临床医学 | 54篇 |
内科学 | 267篇 |
皮肤病学 | 3篇 |
神经病学 | 36篇 |
特种医学 | 26篇 |
外科学 | 128篇 |
综合类 | 2篇 |
预防医学 | 29篇 |
药学 | 99篇 |
中国医学 | 15篇 |
肿瘤学 | 112篇 |
出版年
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 3篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 34篇 |
2012年 | 46篇 |
2011年 | 46篇 |
2010年 | 28篇 |
2009年 | 29篇 |
2008年 | 60篇 |
2007年 | 33篇 |
2006年 | 45篇 |
2005年 | 68篇 |
2004年 | 49篇 |
2003年 | 38篇 |
2002年 | 41篇 |
2001年 | 40篇 |
2000年 | 34篇 |
1999年 | 31篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1969年 | 3篇 |
1967年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有920条查询结果,搜索用时 0 毫秒
1.
1. Magnesium sulphate was studied for its effects on diarrhoea, fluid secretion, gastrointestinal transit and nitric oxide (NO) synthase activity in rats. 2. At a dose of 2 g kg-1 orally magnesium sulphate produced diarrhoea that was delayed in onset and intensity in a dose-related manner by the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). This was prevented by the NO precursor, L-arginine and the NO donating compound, isosorbide-5-mononitrate (IMN). 3. Nitric oxide synthase activity was stimulated in gut tissue from rats given magnesium sulphate and this was inhibited by L-NAME. Dexamethasone (1 mg kg-1, i.p.), an inhibitor of inducible NO synthase, had no effect on magnesium sulphate-induced diarrhoea. 4. Magnesium sulphate stimulated fluid and electrolyte accumulation in the intestinal lumen; these effects were prevented by L-NAME but not D-NAME. 5. Gastrointestinal transit of a non-absorbable marker (charcoal suspension) was increased by oral magnesium sulphate from a mean value of 54.1% to 72.9% (P < 0.01), and this was prevented by pretreatment with L-NAME. 6. The results demonstrate that oral magnesium sulphate produces diarrhoea in rats by increasing the accumulation of fluid in the intestinal lumen and enhancing flow from the proximal to distal intestine. The mechanism involves release of NO, probably through stimulation of the constitutive form of NO synthase. Whether or not the effects of magnesium sulphate are due to an osmotic action or an intrinsic effect of the magnesium or sulphate ions cannot be determined from these experiments. 相似文献
2.
The sensory and motor deficits of the CNS are varied, depending on the etiologic factors and the structures involved. Nevertheless, the clinical picture is predictable, provided one has an adequate knowledge of the neuroanatomy and the functions of the different fiber tracts, nuclei, and other specific regions of the brain and spinal cord. The purpose of this section is to provide an overall view of the sensory and motor deficits of the CNS, which will enable the clinician to treat these patients in a more objective and effective manner. Etiologically, the diseases affecting the CNS can be grouped under the following categories: congenital, traumatic, inflammatory, neoplastic, and degenerative. Congenital conditions usually manifest in infancy and childhood. Examples are hydrocephalus, spina bifida, and Arnold-Chiari malformation. There are a host of other conditions, but the discussion in this article is confined to the more common entities. Traumatic conditions such as cerebral concussion, contusion, laceration, hematomas--extradural, subdural, or intracerebral--and spinal cord injuries can occur in any age group, though their incidence is higher during the more active period of life (20 to 35 years). Automobile accidents are by far the most common etiologic factor for the traumatic lesions. Others, such as falls, gunshot and stab wounds, and so forth account for the remainder. Among the inflammatory conditions, three conditions are important: brain abscess, meningitis, and transverse myelitis. Though brain abscess develops by direct extension from an adjacent focus of infection, often it forms as a result of metastatic infection, chiefly from lung abscess or bronchoectasis. It behaves more like an intracranial space occupying lesion. Of the various types of meningitis, meningococcal meningitis is the commonest. Transverse myelitis may be caused by viruses or bacteria. The clinical picture resembles that of spinal cord injury. Neoplasms of the brain and spinal cord present a wide and varied spectrum. They may be benign or malignant. Meningioma and neurofibroma are essentially benign lesions. Malignant tumors can be primary or secondary. Gliomas and specifically astrocytomas are the commonest primary malignant tumors. The commonest sites of metastatic tumors are lung, breast, kidney, and gastrointestinal tract. The clinical picture will depend on the location of the tumor and the structures pressed upon or infiltrated. Any age group can be affected. Many of the malignant tumors are slowly and relentlessly progressive. Complete surgical extirpation where possible, followed by radiation therapy, is the treatment of choice. Chemotherapy has not been of much benefit.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
3.
4.
Investigation of intestine function during acute viral hepatitis using combined sugar oral loads. 下载免费PDF全文
One fifth of all cases of A virus hepatitis (AVH) have symptoms of gastroenteritis at the onset. This study investigated the mediated intestinal absorption of D-xylose (D-xyl) and 3-o-methyl-D-glucose (3-omG) and the non-mediated permeation of lactulose (Lacl, mol wt 342) and L-rhamnose (L-rh, mol wt 164) during acute and remission phases of AVH. Ten patients with AVH were given an oral load containing these sugars (5 g D-xyl: 2.5 g 3-omG, 1 g L-rh, 5 g lacl in 250 ml water) once during the acute phase and again during remission. The same load was given once to a group of 22 healthy controls. The mean concentration of D-xyl in urine and the ratio of D-xyl to 3-omG in plasma and urine were normal in both the AVH phases, ruling out intestinal malabsorption even in the acute phase. This study showed a significant increase in non-mediated permeation to Lacl, but not to L-rh, during the acute phase. These data indicate that the barrier function of the intestine is compromised in AVH infection while the absorptive function is not. An abnormally low concentration of D-xyl and 3-omG in plasma at one hour was found in all patients during the acute phase. This finding cannot be explained by alterations in intestinal absorption, but could be accounted for by increased space distribution of the sugars because of increased diffusion into tissue cells and/or expansion of the extracellular space by fluid retention. 相似文献
5.
Markers of cell-mediated immunity after vaccination with an inactivated, whole-cell Q fever vaccine 总被引:7,自引:0,他引:7
A clinical trial of Q fever vaccine in four South Australian abattoirs showed apparently complete protection against natural infection; however, only 50%-60% of vaccinees developed complement-fixing or immunofluorescent antibody after vaccination. Cell-mediated immunity to Coxiella burnetii antigens, as measured by an index of lymphoproliferative responses (LSI) of peripheral blood mononuclear cells, was therefore assessed. Eighty-five percent of 13 subjects with "low risk" of exposure to Q fever and with an initially negative LSI converted to a positive LSI after vaccination; conversion was noted nine to 13 days after vaccination, and positive values were obtained for at least 96 d. Only 35% of this group seroconverted. In a "high-risk" group (abattoir workers), higher rates of positive LSI (greater than 95%) and of antibody (50%-70%) were observed after vaccination; greater than 95% of vaccinees in this group, who had been vaccinated five years previously, had positive LSI values. 相似文献
6.
Memory T lymphocytes generated by Mycobacterium bovis BCG vaccination reside within a CD4 CD44lo CD62 ligand(hi) population 下载免费PDF全文
In the lungs of mice vaccinated with Mycobacterium bovis BCG, there was an accumulation of CD4 cells expressing the activated effector phenotype CD44hi CD62 ligandlo) (CD62Llo) which were capable of secreting gamma interferon. Upon cell transfer, however, cells expressing a resting/na?ve phenotype (CD44lo CD62Lhi) were capable of protecting the recipients from a virulent challenge infection, suggesting the emergence of T-cell memory from within this subset. 相似文献
7.
8.
Scarano MI De Rosa M Panariello L Carlomagno N Riegler G Rossi GB Bucci L Pesce G Toni F Renda A Izzo P 《Human mutation》1999,13(3):256-257
Germline mutations within the adenomatous polyposis coli (APC) gene, a tumor suppressor gene, are responsible for most cases of familial adenomatous polyposis (FAP), an autosomal dominantly inherited predisposition to colorectal cancer. To date, more than 300 germ-line causative mutations within this gene have been described (Beroud and Soussi, 1996). Of these, about 95% are chain-terminating mutations, and more than 60% have been localized within exon 15 (Nagase and Nakamura, 1993, Beroud and Soussi, 1996). Using polymerase chain reaction-single strand conformation polymorphism, protein truncation test (PTT) and DNA sequencing we have identified five new frameshift mutations (2523insCTTA, 2638delA, 2803insA, 3185delAA, 4145delTCATGT), all occurring within exon 15 and giving rise to truncated protein products. Two of these new mutations are of particular interest because of the unusual phenotypic features shown by probands. The phenotype of the proband bearing the 2523insCTTA mutation at codon 842 was very aggressive with onset of the symptoms at 12 years, while the patient bearing the 3185delAA mutation at codon 1062 exhibited features of an attenuated form of FAP (AAPC). Our data reiterate the great heterogeneity of the mutational spectrum in FAP that gives rise to an extreme variability of the clinical expression. 相似文献
9.
In order to learn what morphological substrate might underly the histochemical compartments of the neostriatum, sections of the caudate nucleus and the putamen of cats and ferrets were stained immunocytochemically with antisera directed against several neuropeptides and transmitter-related enzymes and were then Golgi-impregnated. Adjacent sections were stained to reveal acetylcholinesterase activity to identify the acetylcholinesterase-poor striosomes. The immunostaining produced by several of the antibody preparations was in register with the acetylcholinesterase-poor striosomes but the most prominent staining of these zones occurred with the antibodies directed against substance P. The striosomes were delineated by intense substance P-immunostaining of neuronal perikarya and dendrites, and in the rostral and dorsal caudate nucleus the boundary between substance P-immunostained and extrastriosomal matrix was abrupt. For these reasons we analysed Golgi-impregnated neurons in sections immunostained for substance P in order to assess the influence of the chemically defined striosomal architecture on the position and dendritic arborization of neurons located both within the striosomes and within the extrastriosomal matrix. The most commonly impregnated neurons were of the medium-size densely spiny class. Those that were present within the striosomes and lay within one dendritic radius of the boundary were divided into two types: (1) neurons whose dendritic arborization was apparently not influenced by the boundary and (2) neurons whose dendritic arborization was markedly influenced by the boundary. For neurons of the latter type, dendrites either emerged from the parts of the perikaryon away from the boundary, so avoiding crossing it, or they exhibited abrupt changes in their course, apparently to avoid crossing the boundary. Spiny neurons located in the extrastriosomal matrix but close to the striosomal boundary had dendrites that were either influenced by, or not influenced by the compartmental boundary. We conclude that there is a specific cytoarchitecture underlying the histochemical compartments of the neostriatum and that different sub-populations of medium-size spiny neurons underly (1) the segregation of information flow in striosomes and the extrastriosomal matrix and (2) communication between striosomes and the extrastriosomal matrix. 相似文献
10.
Type 2 diabetes mellitus (T2DM) represents a major health burden for the elderly population, affecting approximately 25% of people over the age of 65 years. This percentage is expected to increase dramatically in the next decades in relation to the increased longevity of the population observed in recent years. Beyond microvascular and macrovascular complications, sarcopenia has been described as a new diabetes complication in the elderly population. Increasing attention has been paid by researchers and clinicians to this age-related condition—characterized by loss of skeletal muscle mass together with the loss of muscle power and function—in individuals with T2DM; this is due to the heavy impact that sarcopenia may have on physical and psychosocial health of diabetic patients, thus affecting their quality of life. The aim of this narrative review is to provide an update on: (1) the risk of sarcopenia in individuals with T2DM, and (2) its association with relevant features of patients with T2DM such as age, gender, body mass index, disease duration, glycemic control, presence of microvascular or macrovascular complications, nutritional status, and glucose-lowering drugs. From a clinical point of view, it is necessary to improve the ability of physicians and dietitians to recognize early sarcopenia and its risk factors in patients with T2DM in order to make appropriate therapeutic approaches able to prevent and treat this condition. 相似文献