全文获取类型
收费全文 | 30232篇 |
免费 | 889篇 |
国内免费 | 56篇 |
专业分类
耳鼻咽喉 | 110篇 |
儿科学 | 2091篇 |
妇产科学 | 827篇 |
基础医学 | 1614篇 |
口腔科学 | 501篇 |
临床医学 | 1844篇 |
内科学 | 6857篇 |
皮肤病学 | 324篇 |
神经病学 | 1064篇 |
特种医学 | 804篇 |
外科学 | 5253篇 |
综合类 | 2522篇 |
预防医学 | 4866篇 |
眼科学 | 463篇 |
药学 | 1247篇 |
8篇 | |
中国医学 | 177篇 |
肿瘤学 | 605篇 |
出版年
2024年 | 97篇 |
2023年 | 212篇 |
2022年 | 350篇 |
2021年 | 640篇 |
2020年 | 478篇 |
2019年 | 3556篇 |
2018年 | 2771篇 |
2017年 | 1291篇 |
2016年 | 299篇 |
2015年 | 335篇 |
2014年 | 1061篇 |
2013年 | 792篇 |
2012年 | 863篇 |
2011年 | 886篇 |
2010年 | 762篇 |
2009年 | 620篇 |
2008年 | 531篇 |
2007年 | 539篇 |
2006年 | 417篇 |
2005年 | 386篇 |
2004年 | 325篇 |
2003年 | 274篇 |
2002年 | 201篇 |
2001年 | 191篇 |
2000年 | 146篇 |
1999年 | 139篇 |
1998年 | 120篇 |
1997年 | 139篇 |
1996年 | 70篇 |
1995年 | 49篇 |
1994年 | 42篇 |
1993年 | 21篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1985年 | 975篇 |
1984年 | 1404篇 |
1983年 | 1051篇 |
1982年 | 1147篇 |
1981年 | 1099篇 |
1980年 | 956篇 |
1979年 | 1060篇 |
1978年 | 988篇 |
1977年 | 689篇 |
1976年 | 886篇 |
1975年 | 787篇 |
1974年 | 701篇 |
1973年 | 736篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The effect of adrenergic and cholinergic drugs on short incubation “active” E rosette formation was studied in 19 patients with bronchial asthma and 17 healthy controls. Both groups had an equal absolute number of baseline “active” E rosettes, but the asthmatics demonstrated a higher percent baseline value. The beta adrenergic drug isoproterenol (10?3 M) inhibited the formation of “active” E rosettes in asthmatics by only 18.0% as compared to a 60.8% inhibition in the control group. Carbamylcholine (10?5 M) a cholinergic agonist, also showed a lower than normal response in asthmatics, 34.3% enhancement of “active” E rosetting compared to a 52.4% enhancement in the controls. The alpha adrenergic agent phenylephrine (10?5 M) exhibited equal enhancing effects in both groups, 34.2% in the asthmatics and 36.5% in the controls. Isoproterenol (10?3 M) had a minimal effect on inhibition of long incubation “total” E rosettes in both groups studied. The beta adrenergic abnormality conforms to the beta blockade theory of asthma of Szentivanyi. The cholinergic abnormality is unexplained in view of the hyperresponsiveness of patients with asthma to cholinergic agents in vivo. Patients with bronchial asthma probably have an autonomic dysfunction that may play a role in the pathogenesis of their disease. 相似文献
22.
J G Hall M S Birbeck D Robertson J Peppard E Orlans 《Journal of immunological methods》1978,19(4):351-359
Lymph-borne immunoblasts were fixed in dilute glutaraldehyde and then treated with saponin. This treatment made most parts of the cells permeable to ferritin, so that anti-immunoglobulin (Ig) antibodies which had been conjugated to horse radish peroxidase (HRP) had no difficulty in gaining access to Ig which thus could be demonstrated at an ultrastructural level. Best results were obtained by fixing the cells in 0.1% glutaraldehyde for 7 min and then treating them with a 1% solution of saponin for 100 min at 55 degrees C before exposing them to the Ig-HRP conjugate. The method yielded reproducible results and although it causes a small amount of ultrastructural damage, it may be of value in detecting a variety of intracellular antigens. 相似文献
23.
Autopsies were performed in 40 cases of nonimmune hydrops fetalis during the period from 1975 to 1983. In 25 cases specific anatomic diagnoses, including hematologic disorders, infections, chromosomal abnormalities, congenital anomalies, and tumors, were made. In the majority the diagnosis of hydrops fetalis was made prenatally by ultrasonography. The mean gestational age at delivery was 30 weeks; 23 infants were stillborn, and 17 died during the neonatal period. Body weights were consistently increased; peripheral edema and ascites were present in all cases and pleural effusions in all but two cases. Hepatosplenomegaly, cardiomegaly, and pulmonary hypoplasia were frequent findings. The most consistent microscopic changes involved endocrine organs. Islet cell hyperplasia and Leydig cell hyperplasia were common, and thyroid hyperplasia was found occasionally. The fetal zone of the adrenal cortex was often thick and composed of swollen, vacuolated cells. Enhanced extramedullary erythropoiesis was observed in all cases. Thirty-nine placentas were examined; 34 were edematous (mean weight, 547 g), with villous edema, excess erythroblastemia and normoblastemia, and occasional intravillous hematopoiesis. Nonimmune hydrops fetalis has a range of known causes. Thorough autopsy, including placental examination, is the most useful approach for determining the etiology. In 23 cases the probable or possible cause was established in this manner. Antibody studies should also be performed in all cases to exclude an immunologic etiology. Synthesis of clinical, serologic, and pathologic data offers prospects for rational management and prediction of recurrence. 相似文献
24.
Birgitta Swolin Aleksander Weinfeld Johan Waldenström Jan Westin 《Cancer Genetics and Cytogenetics》1983,9(3):197-209
Of 33 consecutive patients with chronic myelocytic leukemia, examined during metamorphosis, 82% showed chromosome abnormalities in addition to the Ph1. Aberrations most frequently encountered were +8 (39%), +22q - (30%), and i(17q) (18%). Translocations other than the Ph1 were observed in four cases and - Y clones in four cases. Discrepancies in the cytogenetic pattern between bone marrow and extramedullary tissues or blood were noted in a total of 15 patients. In six cases, transformation occurred in extramedullary organs at a time when it was not present in the marrow. In three cases the bone marrow transformation was preceded by a lymph node blastic infiltrate; in one case, by a skin infiltrate; and in one case, by a subdural blastoma. Clonal abnormalities additional to the Ph1 were identified in the tumor tissue from all these cases. Patients with primary extramedullary transformation tended to have a lower median age at onset of metamorphosis, shorter survival, and higher incidence of chromosome abnormalities than the cases without extramedullary involvement. Patients with only Ph1-positive cells and no other anomalies had a slightly longer duration of metamorphosis and longer total survival. Basophilia and thrombocytopenia were more marked in cases with i(17q) than in the rest of the series. 相似文献
25.
W C Light R E Reisman V S Ilea J I Wypych T Okazaki C E Arbesman 《The Journal of allergy and clinical immunology》1976,58(2):322-329
The antigenic and allergenic properties of phospholipase A2 (PLA2) and whole bee venom were compared by measuring the IgG and IgE antibody responses in animals and man. Precipitating antibodies raised in rabbits and reaginic and other antibodies raised in mice reacted about equally with both bee venom and PLA. The majority of human sera containing bee venom-specific IgE also contained PLA-specific IgE, although in somewhat lower titers. Similarly, most human sera with significant amounts of total antibodies reacting with bee venom also had antibodies reacting with PLA. Histamine and SRS-a release from leukocytes of sensitive patients followed challenge with whole bee venom and PLA in the majority of instances. However, mediator release from several patients' cells was obtained with bee venom only. These studies suggest that although PLA is a major allergen and antigen in bee venom, significant exceptions in patients' reactivity may limit its potential diagnostic and therapeutic usefulness. 相似文献
26.
M W Yocum D E Johnstone J J Condemi 《The Journal of allergy and clinical immunology》1973,52(5):265-277
We have studied 46 Hymenoptera-allergic patients and 11 nonallergic controls by grading the severity of their sting reaction, determining their skin test reactivity, and performing human leukocyte histamine release with a commercial mixed stinging insect extract. A significant correlation was found between increasing severity of sting reaction and increasing skin test reactivity (p < 0.001). In allergic patients from 15 to 100 per cent release of total cellular histamine occurred, whereas in the 11 nonallergic controls no greater than 10 per cent release of total cellular histamine was observed. Skin test reactivity correlated significantly with cell sensitivity in the allergic patients (p < 0.001). Following hyposensitization therapy, cell sensitivity generally did not change, but significant increases in antigen-neutralizing capacity (A.N.C.) of allergic serum did occur in Hymenoptera-allergic patients. 相似文献
27.
Helen G. Morris M.D. Ittai Neuman M.D. Elliot F. Ellis M.D. 《The Journal of allergy and clinical immunology》1974,54(6):350-358
Plasma steroid concentrations were measured in asthmatic children 24 and 48 hours after administration of alternate-day treatment with prednisone, and the results were compared with those of control patients who did not receive corticosteroid treatment as well as those of patients who were treated with prednisone each day. It was found that 24 hours after administration of prednisone in any dose, plasma steroid concentrations were significantly lower than those of the control group. The degree of suppression in plasma steroid concentration was less marked in patients who received treatment on alternate days than in those who received the same doses of prednisone each day. Within 48 hours after administration of alternate-day treatment, plasma steroid concentrations approached the values observed in the control group and were independent of the magnitude of the prednisone dose. Although alternateday steroid treatment was associated with transient and incomplete suppression of pituitary-adrenal function, patients whose therapy was changed from a daily to an alternate-day regimen sometimes exhibited prolonged suppression of adrenal cortical function. 相似文献
28.
During prolonged nonconvulsive unilateral left limbic status epilepticus, a natural model of functional hemispheric inhibition, we performed two tachistoscopic experiments, a lexical decision task associated with a RVF (left hemisphere) superiority and a facial matching task associated with a LVF (right hemisphere) superiority. We found that epileptic activity in the left hemisphere, especially rhythmic high-frequency "tonic" discharges, inhibited performance on the lexical task but not on the facial matching task. This suggests that only cognitive activity in the discharging hemisphere is inhibited. Strikingly, the best performance of the right hemisphere was obtained while the left hemisphere was most inhibited, suggesting a functional balance of inhibition and release. 相似文献
29.
E Libman W Brender R Burstein S Hodgins 《Journal of behavior therapy and experimental psychiatry》1984,15(2):127-131
Three theoretical formulations of ejaculatory incompetence have been proposed in the literature. They include: (1) aversive conditioned inhibition of the ejaculatory reflex, (2) an "autosexual" orientation associated with discrepant levels in the cognitive and physiological dimensions of sexual arousal, and (3) a discriminative learning model. These three models are discussed in relation to their theoretical and therapeutic implications. Clinical data supporting the discriminative view is presented. 相似文献
30.
J Pearn 《Journal of the neurological sciences》1984,64(1):99-107
The concept of the differential diagnosis has a central place in all clinical medicine. In neurology and paediatrics, evolution of thought concerning the differential diagnosis of the child presenting with symptoms of neuromuscular disease was far in advance of similar diagnostic approaches to problems of infectious, infective and neoplastic disease; and as such forms a significant historical model for the development of modern clinical approaches to the sick or disabled child. The account presented in this paper provides a detailed historical review of the development of thought relating to the causes of neuromuscular disease. Nosological developments concerning diseases of the motor unit can be conveniently classified into three periods: (a) a "state of the art" period to 1850; (b) 1850-1890 - a period of parallel and interdependent advances in both normal neuro-anatomy and neurophysiology, and diseases recognized as variations from such norms. In this era Duchenne was the first to write about the differential diagnosis of the progressive muscular paralysis in childhood; and Gowers was the first to write specifically on the hereditary transmission of this group of diseases; (c) in 1891 was described the first case of childhood neuronopathy recognized as such, and with this development was ushered in the modern era of clinical differential diagnosis of childhood neuromuscular disease. The "splitters" have won the great debate concerning the clinical approach to neurological diseases. The continual further refining of an exact diagnosis is the only way in which a realistic prognosis can be forecast, correct genetic counseling can be offered, and (if the condition is treatable) optimal therapy can be introduced. 相似文献