全文获取类型
收费全文 | 33380篇 |
免费 | 2339篇 |
国内免费 | 1039篇 |
专业分类
耳鼻咽喉 | 357篇 |
儿科学 | 417篇 |
妇产科学 | 372篇 |
基础医学 | 5162篇 |
口腔科学 | 505篇 |
临床医学 | 3440篇 |
内科学 | 5426篇 |
皮肤病学 | 804篇 |
神经病学 | 2397篇 |
特种医学 | 1605篇 |
外国民族医学 | 5篇 |
外科学 | 3803篇 |
综合类 | 2502篇 |
现状与发展 | 7篇 |
一般理论 | 9篇 |
预防医学 | 1842篇 |
眼科学 | 861篇 |
药学 | 3457篇 |
15篇 | |
中国医学 | 1065篇 |
肿瘤学 | 2707篇 |
出版年
2024年 | 60篇 |
2023年 | 412篇 |
2022年 | 1094篇 |
2021年 | 1509篇 |
2020年 | 859篇 |
2019年 | 945篇 |
2018年 | 1071篇 |
2017年 | 854篇 |
2016年 | 1092篇 |
2015年 | 1522篇 |
2014年 | 1834篇 |
2013年 | 1995篇 |
2012年 | 2841篇 |
2011年 | 2935篇 |
2010年 | 1715篇 |
2009年 | 1432篇 |
2008年 | 1999篇 |
2007年 | 1881篇 |
2006年 | 1682篇 |
2005年 | 1587篇 |
2004年 | 1246篇 |
2003年 | 1061篇 |
2002年 | 877篇 |
2001年 | 705篇 |
2000年 | 733篇 |
1999年 | 583篇 |
1998年 | 264篇 |
1997年 | 222篇 |
1996年 | 168篇 |
1995年 | 161篇 |
1994年 | 137篇 |
1993年 | 103篇 |
1992年 | 162篇 |
1991年 | 171篇 |
1990年 | 140篇 |
1989年 | 106篇 |
1988年 | 88篇 |
1987年 | 80篇 |
1986年 | 72篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 31篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Isometric and isokinetic torque curves at the knee joint 总被引:1,自引:0,他引:1
Isometric and isokinetic torques of bilateral quadriceps and hamstrings were measured with Isokinetic Rehabilitation and Testing System (Model No. Cybex 340) on 40 normal untrained subjects, 20 males and 20 females, ranging between the ages of 23 and 35 years. The mean peak isometric and isokinetic torque values of both muscle groups showed no significant differences between dominant (right) and nondominant (left) limbs in both sexes; however there were significant differences between the male and the female. As the angular velocity increased, the peak torque significantly decreased, and the point of peak torque output occurred significantly later in the range of motion for quadriceps and hamstrings (p less than 0.01). There were no significant changes in the hamstrings to quadriceps (H/Q) ratios as the angular velocity increased. However, there were significant differences of mean H/Q ratio between male and female (p less than 0.01). Height had significant positive correlation with peak isometric and isokinetic torques for both quadriceps and hamstrings (p less than 0.01). Weight was found to correlate significantly with peak isometric and isokinetic torques (p less than 0.01). The mean isometric torques were significantly higher than the mean isokinetic torques for any joint angles in both sexes (p less than .01). 相似文献
52.
Bronchial asthma with cockroach hypersensitivity is prevalent among urban asthmatic populations. To elucidate characteristics of cockroach asthma, we analyzed 592 consecutive urban Chicago asthmatic patients retrospectively. Allergy skin testing (AST) with common inhalants, serum total IgE, and cockroach-specific IgE (IgE-CR) antibodies were measured. Some cockroach asthmatics were studied further for bronchial reactivity in vivo and histamine releasability (HR) in vitro against cockroach allergen (CRa), and diagnostic accuracy for asthma was analyzed. Clinical characteristics were evaluated and compared with those of ragweed asthmatics and asthmatics in general. Two hundred eighty-three (196 women, 87 men) were reactive to CRa by AST. The average age and duration of cockroach asthma were 30.4 and 15.1 years, respectively. Steroid dependency of the cockroach asthma was higher (32%) than those of general asthmatics (P less than .05) and ragweed asthma (P less than .05). IgE level was elevated (geometric mean 413.2 IU/mL), higher than that of general asthmatics (P less than .001), and 87% showed IgE level higher than 100 IU/mL. IgE-CR and BPT-CR were positive in 61% (175 tested) and in 87% (166 tested), respectively. Sensitivity and specificity of skin test were 99% and 40%, while those of IgE-CR were 91% and 58%, respectively. IgE-CR increased probability of cockroach asthma from 87% to 91%. BPT with CRa was correlated well with the HR of leukocytes (P less than .0001). Thus, cockroach asthma is a severe allergic asthma and can be diagnosed accurately by skin test plus BPT or skin test plus HR. 相似文献
53.
Jin H Kang Y Xiao C Zhu K Ma Y Xie Q Ma J Xie Q He C Yang Z Sun Z Zhang X Chen M Zhang F Wang B 《Viral immunology》2005,18(3):539-548
Prime-boost strategy has been exhibited its potency to enhance immune responses, which would be important to the success to develop a vaccine against the foot-and-mouth disease virus (FMDV). An eukaryotic expression construct encoding the FMDV capsid VP1 protein with a recombinant VP1 protein or a commercial FMDV vaccine were tested in the prime-boost strategy in mice and cattle trials. The levels of induced specific antibodies, T cell proliferations, and DTH activities were significantly higher in the prime-boost groups than in those vaccinated with DNA, protein or FMDV vaccine alone. More importantly, the levels of neutralizing antibodies in the former groups were significantly higher than others and could last for at least four months in cattle trials. This study suggests that the prime-boost strategy significantly improves the effective immunity and may provide a longer protection against FMDV infection. 相似文献
54.
In our previous study, we demonstrated that immobilization stress blocked estrogen-induced luteinizing hormone (LH) surge possibly by inhibiting the synthesis and release of gonadotropin-releasing hormone (GnRH) at the hypothalamic level and by blocking estrogen-induced prolactin (PRL) surge by increasing the synthesis of dopamine receptor at the pituitary level in ovariectomized rats. The present study was performed to determine whether immobilization stress affects pituitary LH responsiveness to GnRH, and whether endogenous opioid peptide (EOP) and dopamine systems are involved in blocking LH and PRL surges during immobilization stress. Immobilization stress was found to inhibit basal LH release and to completely abolish LH surge. However, the intravenous application of GnRH agonist completely restored immobilization-blocked LH surge and basal LH release. Treatment with naloxone did not exert any effect on immobilization-blocked LH surge but increased basal LH release during immobilization stress. Pimozide did not affect immobilization-blocked LH surge or basal LH release. Naloxone also decreased immobilization-induced basal PRL release, but had no effect on immobilization-blocked PRL surge. Immobilization-increased basal PRL levels were augmented by pimozide treatment and immobilization-blocked PRL surge was dramatically restored by pimozide. We conclude that immobilization stress does not impair pituitary LH response to GnRH, and that the immobilization stress-induced blockage of LH surge is probably not mediated by either the opioidergic or the dopaminergic system. However, immobilization-blockade of PRL surge may be partly mediated by the dopaminergic system. 相似文献
55.
4-1BB(CD137) is a member of the tumour necrosis factor receptor superfamily and is expressed on activated T cells, monocytes and natural killer (NK) cells. The interaction of 4-1BB and 4-1BB ligand provides a costimulatory signal leading to T-cell activation. The expression of 4-1BB has been known to be activation dependent. Interestingly, we found that expression of 4-1BB increased in human peripheral blood mononuclear cells after exposure to mitomycin C. Thus, we tested whether the treatment with other DNA-damaging agents, such as doxorubicin, bleomycin, and gamma-irradiation, could induce 4-1BB expression. The data indicated that 4-1BB expression increased dose-dependently by these agents reaching maximum at 2-3 days after the exposure. We found that the major 4-1BB-expressing population was CD3+ T cells, although a moderate number of CD14+ cells and a few NKB1+ cells also expressed 4-1BB. The levels of 4-1BB expression induced by anticancer drugs, were relatively lower than that induced by CD3 ligation. Interestingly, at subcytotoxic concentrations, doxorubicin and bleomycin considerably enhanced 4-1BB expression induced by CD3 ligation in CEM cells. The ligation of the damage-induced 4-1BB by monoclonal antibody enhanced the viability and proliferating capacity of the cells. In conclusion, the expression of 4-1BB might be one of the cellular responses of the immune cells against various genotoxic stresses. 相似文献
56.
Immunocytochemical localization of metallothionein and its relation to doxorubicin toxicity in transgenic mouse heart 下载免费PDF全文
Previous studies using a cardiac-specific metallothionein-overexpressing transgenic mouse model have demonstrated that metallothionein protects the heart from doxorubicin toxicity. The present study was undertaken to determine cellular and subcellular distribution of metallothionein and located the antioxidant action of this protein in the transgenic heart. Using light microscopic immunoperoxidase method, it was identified that the overexpressed metallothionein is localized exclusively in cardiomyocytes. The electron microscopic immunogold method revealed that elevated metallothionein is in nucleus, myofibers, and sarcoplasm. In contrast with these distributions, metallothionein in nontransgenic myocardium was undetectable by immunoperoxidase light microscopy and was seldom found in nucleus and myofibers by immunogold electron microscopy. Treatment with doxorubicin induced cytoplasmic vacuolization and severe damages in myofilaments and nucleus in nontransgenic myocardium. The most prominent injury, however, occurred in mitochondria, including striking size and shape changes, focal swelling and loss of cristae. These damages were rarely found in the doxorubicin-treated transgenic myocardium. In particular, the internal morphology of mitochondria was maintained essentially normal, although metallothionein was not localized in this compartment in transgenic hearts. This study thus demonstrates that although the subcellularly localized action of metallothionein is important, it also plays a significant role in protection against oxidative injury by doxorubicin in remote organelles. 相似文献
57.
We report two cases of lichen planus pigmentosus (LPP) that developed in a unilateral linear pattern. The patients presented with unilateral linear brown macules on the extremities. Skin biopsy showed orthokeratosis, basal hydropic degeneration with scarce lymphohistiocytic infiltrates, and numerous melanophages in both patients. These patients, to the best of our knowledge, are the first cases of LPP presenting with a linear pattern. LPP should be considered in the differential diagnosis of linear hyperpigmented skin lesions. 相似文献
58.
Lee JK Kim JH Kim JS Kim TS Jung S Kim SH Kang SS Lee JH 《Journal of Korean medical science》2001,16(4):532-536
Amenorrhea is rarely presented as a manifestation of endocrinological disturbances in patients of chronic hydrocephalus. We describe two cases of secondary amenorrhea caused by hydrocephalus due to aqueductal stenosis. Two female patients of age 30 and 20 yr presented with amenorrhea and increasing headache. Magnetic resonance images revealed marked, noncommunicating hydrocephalus without any tumorous lesion. In one patient, emergent extraventricular drainage was necessary because of progressive neurological deterioration. Each patient underwent surgical intervention for the hydrocephalus-ventriculoperitoneal shunt and endoscopic third ventriculostomy. Both resumed normal menstruation continuing so far with further normal menstrual bleeding. These two cases and others reported in the literature indicated that the surgical intervention for hydrocephalus resolves amenorrhea in all the cases of amenorrhea due to hydrocephalus. The suspected role of the surgery is the correction of increased intracranial pressure, which is an important pathogenetic factor in the development of amenorrhea. 相似文献
59.
Chung JP Chi SW Park YN Lee SJ Song SY Lee KS Chung JB Lee SI Kang JK Kim KW Chi HS 《Yonsei medical journal》2000,41(4):528-532
Intraductal papillary mucinous tumor (IPMT) of the pancreas, a lesion consisting of mucin-producing cells with neoplastic potential, is characterized by duct ectasia, mucin hypersecretion, often extensive papillary intraductal growth, varying degrees of cytologic atypia, and relatively indolent growth. The clinical presentation of IPMT of the pancreas is characterized by chronic or recurrent attacks of abdominal discomfort often in association with low level pancreatic enzyme elevations. Less commonly these lesions may be detected as asymptomatic radiographic abnormalities. Interestingly, a case of a minute IPMT (2 mm in height and 7 mm in length, adenoma) in the main pancreatic duct presenting with acute pancreatitis in a 55 year-old man has been reported in the Japanese literature. Recently, we also experienced a case of a minute IPMT in a branch pancreatic duct causing repeated bouts of acute pancreatitis in a 75 year-old man. A filling defect at the neck of the main pancreatic duct seen on an endoscopic retrograde pancreatogram performed after recovery of the second attack of acute pancreatitis led the patient to undergo an exploratory laparotomy. After a near-total pancreatectomy was carried out, a minute (3 x 7 mm) IPMT of borderline malignancy was discovered in a branch duct at the head portion near the pancreatic neck without any lesions in the main pancreatic duct. Surprisingly, despite the resective surgery the patient died of carcinomatosis 8.5 months after the operation. We herein report a case of a minute but aggressive IPMT of the pancreas with a review of the literature. 相似文献
60.
Cooperative transformation of murine fibroblast NIH3T3 cells by hepatitis C virus core protein and hepatitis B virus X protein 总被引:7,自引:0,他引:7
Co-infection with hepatitis B virus (HBV) and hepatitis C Virus (HCV) is associated with increased frequency in the development of hepatocellular carcinoma (HCC). Here, we demonstrated that HBV X protein (HBx) and HCV core cooperate to transform mouse fibroblast NIH3T3 cells. They additively stimulated cell growth, especially in the absence of serum growth factors. In addition, co-expression of HBx and HCV core had additive effects on the induction of anchorage-independent cell growth as well as on the secretion of matrix metalloproteases, which may contribute to increased metastatic potential. Furthermore, the cells expressing both viral proteins exhibited higher tumorigenicity, as demonstrated in athymic nude mice. 相似文献