全文获取类型
收费全文 | 27898篇 |
免费 | 1936篇 |
国内免费 | 110篇 |
专业分类
耳鼻咽喉 | 285篇 |
儿科学 | 799篇 |
妇产科学 | 594篇 |
基础医学 | 4244篇 |
口腔科学 | 2523篇 |
临床医学 | 2277篇 |
内科学 | 5523篇 |
皮肤病学 | 601篇 |
神经病学 | 2113篇 |
特种医学 | 654篇 |
外国民族医学 | 1篇 |
外科学 | 3093篇 |
综合类 | 356篇 |
一般理论 | 7篇 |
预防医学 | 3197篇 |
眼科学 | 349篇 |
药学 | 2017篇 |
2篇 | |
中国医学 | 281篇 |
肿瘤学 | 1028篇 |
出版年
2023年 | 260篇 |
2022年 | 489篇 |
2021年 | 1064篇 |
2020年 | 736篇 |
2019年 | 926篇 |
2018年 | 1065篇 |
2017年 | 794篇 |
2016年 | 811篇 |
2015年 | 947篇 |
2014年 | 1221篇 |
2013年 | 1459篇 |
2012年 | 2218篇 |
2011年 | 2433篇 |
2010年 | 1285篇 |
2009年 | 970篇 |
2008年 | 1604篇 |
2007年 | 1505篇 |
2006年 | 1385篇 |
2005年 | 1126篇 |
2004年 | 994篇 |
2003年 | 888篇 |
2002年 | 793篇 |
2001年 | 554篇 |
2000年 | 606篇 |
1999年 | 487篇 |
1998年 | 191篇 |
1997年 | 134篇 |
1996年 | 133篇 |
1995年 | 124篇 |
1994年 | 104篇 |
1993年 | 83篇 |
1992年 | 218篇 |
1991年 | 210篇 |
1990年 | 202篇 |
1989年 | 197篇 |
1988年 | 180篇 |
1987年 | 139篇 |
1986年 | 127篇 |
1985年 | 129篇 |
1984年 | 104篇 |
1983年 | 88篇 |
1979年 | 89篇 |
1978年 | 80篇 |
1977年 | 49篇 |
1975年 | 58篇 |
1974年 | 62篇 |
1973年 | 62篇 |
1970年 | 60篇 |
1969年 | 47篇 |
1967年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Joaquim Ferreira MD João Maia Silva MD Rita Freire BS João Pignatelli MD Leonor Correia Guedes MD Alexandra Feijó MD Mário Miguel Rosa MD Miguel Coelho MD João Costa MD Ana Noronha BS Russell Hewett MD A. Marques Gomes PhD J.L. Cirne de Castro MD Olivier Rascol PhD Cristina Sampaio PhD 《Movement disorders》2007,22(10):1471-1475
Our objective was to evaluate the frequency of neoplastic and preneoplastic skin lesions in Parkinson's disease (PD) patients when compared with an aged-matched population. We performed a cross-sectional survey in PD patients and in an age-matched control group. Patients and controls were examined by a movement disorder specialist and a dermatologist. 150 PD patients and 146 controls were included. Thirty-five PD patients (23.3%) presented skin lesions that could be classified as neoplastic or preneoplastic vs. 20 subjects in the control group (13.7%) (OR 95%, CI 1.92 [1.05, 3.51]). However, this difference lost statistical significance when adjusted for gender (recruitment of controls was matched just for age with an over representation of males in the PD group). Twenty-nine PD patients (19%) presented actinic keratosis and basal cell carcinoma was diagnosed in 4 patients (3%). Although nonconclusive, our results are in agreement with previous studies suggesting an increased risk of skin cancer in PD patients. The frequency of actinic keratosis in PD patients and the associated risk to develop melanoma recommends its screening in future epidemiological studies. 相似文献
112.
Amyloid fibril formation by human stefin B: influence of pH and TFE on fibril growth and morphology.
Eva Zerovnik Miha Skarabot Katja Skerget Silva Giannini Veronika Stoka Sasa Jenko-Kokalj Rosemary A Staniforth 《Amyloid》2007,14(3):237-247
As shown before, human stefin B (cystatin B) populates two partly unfolded species, a native-like state at pH 4.8 and a structured molten globule state at pH 3.3 (high ionic strength), from each of which amyloid fibrils grow. Here, we show that the fibrils obtained at pH 3.3 differ from those at pH 4.8 and that those obtained at pH 3.3 (protofibrils) do not transform readily to mature fibrils. In addition we show that amorphous aggregates are also a source of fibrils. The kinetics of amyloid fibril formation at different trifluoroethanol (TFE) concentrations were measured. TFE accelerates fibril growth at predenaturational concentrations of the alcohol. At concentrations higher than 10%, the fibrillar yield decreases proportionately as the population of an all alpha-helical, denatured form of the protein increases. At an optimum TFE concentration, the lag and the growth phases are observed, similarly to some other amyloidogenic proteins. Morphology of the protein species at the beginning and the end of the reactions was observed using atomic force microscopy and transmission electron microscopy. Final fibril morphologies differ depending on solvent conditions. 相似文献
113.
P. de Silva 《Clinical psychology & psychotherapy》1994,1(3):174-178
This paper discusses short-term treatment for morbid jealousy. A brief account of the clinical presentation of morbid jealousy is given. Theoretical approaches to this phenomenon are summarized and commented on. Specific behavioural and cognitive techniques are described, and their rationale explained. Case examples are cited to illustrate the use of these techniques. Some general comments on the application of these techniques are also made. 相似文献
114.
Cleide G. da Silva Ana Rúbia F. Bueno Patrícia F. Schuck Guilhian Leipnitz Csar A. J. Ribeiro Clvis M. D. Wannmacher Angela T. S. Wyse Moacir Wajner 《International journal of developmental neuroscience》2003,21(4):217-224
L-2-Hydroxyglutaric acid (LGA) is the biochemical hallmark of patients affected by the neurometabolic disorder known as L-2-hydroxyglutaric aciduria (LHGA). Although this disorder is predominantly characterized by severe neurological findings and pronounced cerebellum atrophy, the neurotoxic mechanisms of brain injury are virtually unknown. In the present study, we investigated the effect of LGA, at 0.25-5mM concentrations, on total creatine kinase (tCK) activity from cerebellum, cerebral cortex, cardiac muscle and skeletal muscle homogenates of 30-day-old Wistar rats. CK activity was measured also in the cytosolic (Cy-CK) and mitochondrial (Mi-CK) fractions from cerebellum. We verified that tCK activity was significantly inhibited by LGA in the cerebellum, but not in cerebral cortex, cardiac muscle and skeletal muscle. Furthermore, CK activity from the mitochondrial fraction was inhibited by LGA, whereas that from the cytosolic fraction of cerebellum was not affected by the acid. Kinetic studies revealed that the inhibitory effect of LGA on Mi-CK was non-competitive in relation to phosphocreatine. Finally, we verified that the inhibitory effect of LGA on tCK was fully prevented by pre-incubation of the homogenates with reduced glutathione (GSH), suggesting that this inhibition is possibly mediated by oxidation of essential thiol groups of the enzyme. Considering the importance of creatine kinase activity for energy homeostasis, our results suggest that the selective inhibition of this enzyme activity by increased levels of LGA could be possibly related to the cerebellar degeneration characteristically found in patients affected by L-2-hydroxyglutaric aciduria. 相似文献
115.
116.
117.
Tamoxifen (TAM), a non-steroid antiestrogen, is the mostly used drug for chemotherapy and chemoprevention of breast cancer. However, the mechanisms by which TAM inhibits cell proliferation in breast cancer are not fully understood. TAM strongly incorporates in biomembranes and a variety of effects have been assigned to biophysical and biochemical interactions with membranes. Therefore, a better understanding of the physicochemical basis of interaction of TAM with biomembranes is essential to elucidate the molecular mechanisms of action. A strain of Bacillus stearothermophilus has been used as a model to clarify the interaction of TAM with the cell membrane. TAM effects on the ultrastructure of membranes of this bacterium were evaluated by electron microscopy. Important ultrastructural alterations were observed in B. stearothermophilus treated with TAM, namely change in the geometry of the membrane profile from asymmetric to symmetric, disaggregation of ribosomes, coagulation of the cytoplasmic matrix, occurrence of mesossomes, appearance of fractures in membranes and the alteration of the ultrastructure of cell wall. These ultrastructural alterations confirm that TAM is a membrane-active drug and that membrane damage may be involved in molecular mechanisms of cell death induced by this drug. 相似文献
118.
Tamoxifen (TAM), a non-steroid antiestrogen, is the mostly used drug for chemotherapy and chemoprevention of breast cancer. However, the mechanisms by which TAM inhibits cell proliferation in breast cancer are not fully understood. TAM strongly incorporates in biomembranes and a variety of effects have been assigned to biophysical and biochemical interactions with membranes. Therefore, a better understanding of the physicochemical basis of interaction of TAM with biomembranes is essential to elucidate the molecular mechanisms of action. A strain of Bacillus stearothermophilus has been used as a model to clarify the interaction of TAM with the cell membrane. TAM effects on the ultrastructure of membranes of this bacterium were evaluated by electron microscopy. Important ultrastructural alterations were observed in B. stearothermophilus treated with TAM, namely change in the geometry of the membrane profile from asymmetric to symmetric, disaggregation of ribosomes, coagulation of the cytoplasmic matrix, occurrence of mesossomes, appearance of fractures in membranes and the alteration of the ultrastructure of cell wall. These ultrastructural alterations confirm that TAM is a membrane-active drug and that membrane damage may be involved in molecular mechanisms of cell death induced by this drug. 相似文献
119.
Flavia Nogueira Edinaldo Castro E. Silva Wolfgang Junk 《International journal of environmental health research》1997,7(3):181-192
The Pocone gold minings are situated in the Bento Gomes River Basin, at the border of the Pantanal of Mato Grosso. Gold-bearing quartz veins are removed from the subsoils, milled with water, centrifuged and the heavier fraction is subsequently mixed with mercury for gold separation. The gold mining activities caused a very intensive landscape change, threatening many environmental processes like sediment control and storage and recycling capacity of mercury. Cold Vapor Atomic Fluorescence System (CVAFS) was used to determinate total mercury in water, suspended material and sediments from Bento Gomes River, sampled monthly for 1 year. Apart from the fact that mercury concentrations are low in water and bottom sediments, they are slightly higher in relation to background levels measured in the area. The concentration in suspended material is also lower than other rivers with gold mining activities, but the floodplains of the Bento Gomes River act as mercury sinks. Therefore, the discharge of mercury into the Pantanal floodplain should be avoided, in spite of actual contamination of the system being very low. 相似文献
120.
E Massad P H Saldiva C D Saldiva M P Caldeira L M Cardoso A M de Morais D F Calheiros R da Silva G M B?hm 《Environmental research》1986,40(2):479-486
A comparative chronic inhalation exposure study was performed to investigate the potential health effects of gasoline and ethanol engine exhaust fumes. Test atmospheres of gasoline and ethanol exhaust were given to Wistar rats and Balb C mice housed in inhalation chambers for a period of 5 weeks. Gas concentration and physical parameters were continually monitored during the exposure period. Several biological parameters were assessed after the exposure including pulmonary function, mutagenicity, and hematological, biochemical, and morphological examinations. The results demonstrated that the chronic toxicity of the gasoline-fueled engine is significantly higher than that of the ethanol engine. 相似文献