全文获取类型
收费全文 | 768篇 |
免费 | 44篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 35篇 |
妇产科学 | 11篇 |
基础医学 | 97篇 |
口腔科学 | 24篇 |
临床医学 | 98篇 |
内科学 | 151篇 |
皮肤病学 | 29篇 |
神经病学 | 80篇 |
特种医学 | 39篇 |
外科学 | 92篇 |
综合类 | 19篇 |
预防医学 | 53篇 |
眼科学 | 8篇 |
药学 | 47篇 |
中国医学 | 3篇 |
肿瘤学 | 31篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 19篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 28篇 |
2013年 | 40篇 |
2012年 | 48篇 |
2011年 | 37篇 |
2010年 | 32篇 |
2009年 | 37篇 |
2008年 | 41篇 |
2007年 | 30篇 |
2006年 | 37篇 |
2005年 | 43篇 |
2004年 | 25篇 |
2003年 | 30篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 19篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 4篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1932年 | 5篇 |
1930年 | 5篇 |
1929年 | 2篇 |
1928年 | 3篇 |
1927年 | 2篇 |
排序方式: 共有828条查询结果,搜索用时 15 毫秒
1.
神经生长因子对小鼠突触体内Ca^2+水平的调节作用 总被引:4,自引:1,他引:3
观察了多次海马内微注射NGF对小鼠突触体内游离钙水平的影响,并在离体情况下观察NGF对EGTA和CaCl2分别造成突触体内低钙和高钙状态的调节作用。结果如下:(1)在体实验表明,一定剂量的NGF可显著降低老年小鼠海马突触体内游离钙水平(P<005);(2)离体实验表明,当突触体游离钙水平降低时,适当剂量的NGF具有升高游离钙水平的作用;而突触体内游离钙水平升高时,则NGF有降低游离钙水平的作用。提示NGF对游离钙水平的双向调节作用可能是NGF改善老年性记忆衰退的作用机制。 相似文献
2.
Perla A Vargas Pippa M Simpson Margo Bushmiaer Rajiv Goel Craig A Jones James S Magee Charles R Feild Stacie M Jones 《Annals of allergy, asthma & immunology》2006,96(6):787-793
BACKGROUND: Children with poorly controlled asthma are at high risk of airway remodeling, sleep disruption, school absenteeism, and limited participation in activities. OBJECTIVE: To determine asthma prevalence and characterize disease severity and burden in school-aged children. METHOD: A case-finding study was conducted via a multiple-choice questionnaire and asthma algorithm. Items used for analysis include physician diagnosis of asthma, symptom severity, and health care utilization. The chi2 test was used to determine the significance of differences among cases. Logistic regression was used to evaluate the association of patient factors and asthma indicators. RESULTS: Of the 5,417 children surveyed, 1,341 (25%) were classified as being at risk of asthma. Of these asthma cases, 55% were positive by diagnosis and algorithm (active), 10% were positive per algorithm alone (suspected), and 35% were positive per diagnosis alone (nonactive). Only 14% of all asthma cases reported experiencing no respiratory symptoms (< 1% active, 2% suspected, and 40% nonactive) compared with 75% of noncases. Also, 75% of noncases reported never missing school compared with 19%, 33%, and 54% of active, suspected, and nonactive asthma cases. African American race, Medicaid enrollment, and male sex were independent predictors of asthma risk. Similarly, African American race, Medicaid enrollment, age, and persistent asthma were independent predictors of emergency department use among asthma cases. DISCUSSION: Prevalence of active symptoms suggestive of poor asthma control was extremely high among urban, minority children enrolled in Arkansas' largest public school district. Poor asthma control greatly affects quality of life, including school attendance and performance. Interventions should raise expectations and emphasize the importance of achieving asthma control. 相似文献
3.
MY Mancao LJ Sindel PH Richardson FM Silver 《Acta paediatrica (Oslo, Norway : 1992)》1996,85(1):118-120
Croup is an acute infectious illness usually occurring in children; it is characterized by brassy cough and stridor. The main pathogens include mainly parainfluenza and influenza viruses. Recently there have been reports of prolonged croup caused by the herpes simplex viruses. We report two cases of prolonged croup due to herpes simplex types 1 and 2. We also review and summarize the reported pediatric cases of herpetic croup. 相似文献
4.
Duncan WC; Illingworth PJ; Young FM; Fraser HM 《Human reproduction (Oxford, England)》1998,13(9):2532-2540
The molecular mechanisms involved in luteolysis are still unclear in the
primate. This study aimed to investigate the effect of induced luteolysis
on the ovarian luteinizing hormone (LH) receptor and the steroidogenic
enzyme, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the marmoset
monkey. Luteolysis was induced in the mid-luteal phase either directly by
systemic prostaglandin F2alpha (PGF2alpha), or indirectly by LH withdrawal
using systemic gonadotrophin releasing hormone antagonist (GnRHant)
treatment. The LH receptor was studied by isotopic mRNA in-situ
hybridization and in-situ ligand binding and 3beta-HSD expression was
studied using isotopic mRNA in-situ hybridization and immunohistochemistry.
Induced luteolysis was associated with a reduction in the expression of LH
receptor (P < 0.0001) and 3beta-HSD mRNA, closely followed by a
reduction in the LH receptor (P < 0.05) and 3beta-HSD protein
concentrations within 24 h. There were no differences in the findings
whether luteolysis was induced with PGF2alpha or GnRHant. This study shows
that disparate mechanisms to induce luteolysis in the primate result in an
identical rapid loss of the LH receptor and 3beta-HSD. In conclusion,
induced luteolysis leads to rapid loss of the steroidogenic pathway in
luteal cells.
相似文献
5.
6.
7.
8.
9.
Transition metal complexes containing vanadium IV have been shown to
modulate the cellular redox potential and catalyse the generation of
reactive oxygen intermediates (ROI). Since sperm function is exquisitely
susceptible to ROI, we examined the effects of stable chelate complexes of
vanadocenes on human sperm motility. We synthesized seven structurally
distinct chelate complexes of bis(cyclopentadienyl)vanadium(IV) with
bidentate ligands [i.e. vanadocene acetylacetonato monotriflate (VDacac),
vanadocene hexafluoro acetylacetonato monotriflate (VDHfacac), vanadocene
N-phenyl benzohydroxamato monotriflate (VDPH), vanadocene acethydroxamato
monotriflate (VDH), vanadocene catecholate (VDCAT), vanadocene bipyridino
ditriflate (VDBPY), and vanadocene dithiocarbamate monotriflate (VDDTC)],
and evaluated their spermicidal activity using computer-assisted sperm
analysis (CASA; Hamilton-Thorne). All seven chelate complexes of vanadocene
elicited potent spermicidal activity at micromolar concentrations (EC50
values: 3.9-106 microM) without affecting the sperm acrosome integrity. The
catecholate and acetylacetonate complexes of vanadocene were the most
active and the bipyridyl complex the least active with an order of efficacy
VDCAT > VDacac > VDDTC > VDPH > VDH > VDHfacac > VDBPY.
The spermicidal activity of chelate complexes of vanadocenes was rapid and
irreversible since the treated spermatozoa underwent apoptosis, as
determined by the flow cytometric analysis of mitochondrial membrane
potential, surface annexin V binding assay, in-situ nick-end labelling of
sperm nuclei, and confocal laser scanning microscopy. These results provide
unprecedented evidence that chelate complexes of vanadocene with bidentate
ligands have spermicidal and apoptosis inducing properties. These
vanadocene complexes, especially VDacac, may be useful as contraceptive
agents.
相似文献
10.
Tamara T Perry Perla A Vargas Jeremy Bufford Charles Feild Michael Flick Pippa M Simpson Robert G Hamilton Stacie M Jones 《Annals of allergy, asthma & immunology》2008,100(4):358-363
BACKGROUND: The impact of preschool environmental conditions on classroom aeroallergen concentrations is not fully understood. OBJECTIVE: To examine the relationship between school environmental conditions and classroom aeroallergen concentrations in the Pulaski County Head Start (HS) Program. METHODS: Thirty-three HS centers in Pulaski County, Arkansas, underwent a detailed environmental evaluation. Classroom settled dust samples were analyzed for the presence of common indoor allergens. RESULTS: Classroom eating (70%), wall-to-wall carpeting (58%), and water damage (33%) were common. Median classroom allergen levels were as follows: dust mite (Der p 1 and Der f 1), 0.6 microg/g; Fel d 1, 0.4 microg/g; Can f 1, 1.7 microg/g; cockroach, below detection; Mus m 1, 0.18 microg/g; and mold spores, 17,800 CFU/g. Can f 1 and Mus m 1 allergens were detected in 100% of HS centers. Facilities with carpeting, increased humidity, and single-use facilities showed trends toward increased dust mite concentrations. Detectable cockroach allergen was more common in classrooms cleaned by teachers than by professional housekeepers. CONCLUSIONS: Aeroallergens were commonly detected in Pulaski County HS center classrooms, with dog and mouse allergens detected in 100% of centers. Median classroom allergen concentrations were low, and classroom characteristics were not strongly predictive of increased allergen exposure. 相似文献