全文获取类型
收费全文 | 4656篇 |
免费 | 178篇 |
国内免费 | 17篇 |
专业分类
耳鼻咽喉 | 117篇 |
儿科学 | 117篇 |
妇产科学 | 220篇 |
基础医学 | 592篇 |
口腔科学 | 12篇 |
临床医学 | 312篇 |
内科学 | 1296篇 |
皮肤病学 | 100篇 |
神经病学 | 284篇 |
特种医学 | 82篇 |
外科学 | 590篇 |
综合类 | 41篇 |
一般理论 | 1篇 |
预防医学 | 249篇 |
眼科学 | 71篇 |
药学 | 381篇 |
中国医学 | 4篇 |
肿瘤学 | 382篇 |
出版年
2023年 | 23篇 |
2022年 | 111篇 |
2021年 | 201篇 |
2020年 | 61篇 |
2019年 | 92篇 |
2018年 | 112篇 |
2017年 | 87篇 |
2016年 | 104篇 |
2015年 | 122篇 |
2014年 | 160篇 |
2013年 | 215篇 |
2012年 | 365篇 |
2011年 | 409篇 |
2010年 | 185篇 |
2009年 | 103篇 |
2008年 | 295篇 |
2007年 | 360篇 |
2006年 | 335篇 |
2005年 | 313篇 |
2004年 | 332篇 |
2003年 | 334篇 |
2002年 | 239篇 |
2001年 | 36篇 |
2000年 | 26篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 28篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1968年 | 1篇 |
排序方式: 共有4851条查询结果,搜索用时 15 毫秒
31.
Thrombotic thrombocytopenic purpura (TTP) is characterized by microangiopathic hemolytic anemia and thrombocytopenia, accompanied by microvascular thrombosis that causes variable degrees of tissue ischemia and infarction. About 10-20% of TTP cases are associated with the pregnancy. Preterm delivery and intrauterine fetal death are frequent pregnancy complications of TTP. The following paper presents the case of a 32-year-old woman with TTP relapse at 10 weeks of her second pregnancy. Despite regular fresh frozen plasma transfusions, intrauterine fetal death occurred at 21 weeks of gestation. Current views on TTP management during pregnancy have been presented in the article as well. 相似文献
32.
33.
Iciek R Wender-Ozegowska E Seremak-Mrozikiewicz A Drews K Brazert J 《Ginekologia polska》2007,78(8):642-646
The article presents information about leptin as the major metabolic hormone. The structure, localization of the hormone and its receptor have been described focusing on maturation and fertility processes. Several polymorphisms of leptin gene and its receptor have been described as potential developmental factors of pregnancy complications such as diabetes mellitus or pregnancy induced hypertension. 相似文献
34.
Semczuk-Sikora A Krzyzanowski A Stachowicz N Robak J Kraczkowski J Kwiatek M Semczuk M 《Ginekologia polska》2007,78(10):783-786
INTRODUCTION: Pathomechanism of intrauterine growth restriction is a complex issue, involving many different factors, and is still undergoing an investigation. Improper placental angiogenesis, resulting in placental pathology, is considered to be one of the most important causes of IUGR. Placental vascular growth factors--placental growth factor (PIGF), vascular endothelial growth factor (VEGF) and its receptor (VEGFR-1), are involved in the mechanism of placental vascular development and maternal endothelial function during the pregnancy. AIM: The aim of our study was to evaluate the maternal serum concentration of vascular growth factors (PIGF, VEGF) and their receptor (VEGFR-1), as well as the placental volume in pregnancies complicated by IUGR, and to compare the results with healthy control groups. MATERIAL AND METHODS: 20 patients with intrauterine growth restriction and 18 healthy pregnant women were recruited. Their blood serum samples were assayed for the placental growth factor (PIGF), vascular endothelial growth factor (VEGF) and their receptor (VEGFR-1). These placental factors were measured with the ELISA- method (R@D Systems Kits. In all cases the placental volume was assessed with an ultrasound (Voluson V730 GE) with VOCAL (Virtual Organ Komputer-aided AnaLysis). RESULTS: Our investigation revealed significantly lower maternal serum concentrations of PIGF in pregnancies with IUGR, comparing to the controls in the third trimester. In most cases, VEGF concentrations were undetectable in the maternal serum both, in the second as well as in the third trimester. In the 2nd trimester VEGFR-1 concentrations were statistically higher in the investigated group. In the 3rd trimester the concentrations of VEGFR-1 were higher in the investigated group, but the difference has not achieved the level of statistical importance. The mean placental volume was lower in the investigated group but with not statistical gnificance. CONCLUSIONS: Presented and documented dependencies may indicate the involvement of angiogenic factors in a pathomechanism of intrauterine growth restriction process. It seems that the measurement of placental volume may be useful in IUGR diagnosis. However, it should be a complementary examination only, due to technical limitations. 相似文献
35.
36.
Payam Samadi Michal J. Binczarski Aleksandra Pawlaczyk Jacek Rogowski Malgorzata I. Szynkowska-Jozwik Izabela A. Witonska 《Materials》2022,15(12)
A porous TiO2 layer was prepared with the plasma electrolytic oxidation (PEO) of Ti. In a further step, Pd was deposited on the TiO2 surface layer using the adsorption method. The activity of the Pd/TiO2/Ti catalyst was investigated during the oxidation of CO to CO2 in a mixture of air with 5% CO. The structure of the catalytic active layer was studied using a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray diffraction (XRD). The PEO process provided a porous TiO2 layer with a uniform thickness in the range of 5–10 µm, which is desirable for the production of Pd-supported catalysts. A TOF-SIMS analysis showed the formation of Pd nanoparticles after the adsorption treatment. The conversion of CO to CO2 in all samples was achieved at 150–280 °C, depending on the concentration of Pd. The composition of Pd/ TiO2/Ti was determined using ICP-MS. The optimum concentration of Pd on the surface of the catalyst was approximately 0.14% wt. This concentration was obtained when a 0.4% PdCl2 solution was used in the adsorption process. Increasing the concentration of PdCl2 did not lead to a further improvement in the activity of Pd/ TiO2/Ti. 相似文献
37.
IntroductionRetroperitoneal fibrosis (RPF) is a rare disease associated with the formation of hard inflammatory and fibrous tissue in the retroperitoneum. Taking into consideration the fact that RPF is a rare disease with different subtypes, we compared the basal clinical and biochemical characteristics of the vascular and urorenal subtypes.Patients and methodsFrom January 2005 until December 2021, 27 patients were identified as vascular subtype (18 males) and 11 as urorenal subtype (9 males).ResultsPatients with a primary urorenal origin had significantly worse kidney function as reflected by serum creatinine and eGFR (both p < 0.001); they also had higher serum cholesterol (p < 0.01). Hypertension, diabetes, hyperlipidemia and nicotinism were significantly more prevalent in vascular subtype (all p < 0.001).ConclusionVascular subtype is more prevalent in our study with more cardiovascular risk factor present. Due to the diversity of symptoms, diagnosis of RPF becomes a challenge for specialists as well as therapy. 相似文献
38.
Tomasz Bartosik Joanna Drogosz-Stachowicz Anna Janecka Jacek Kdzia Barbara Pacholczyk-Sienicka Jacek Szymaski Katarzyna Gach-Janczak Tomasz Janecki 《Materials》2022,15(9)
In this report, we present efficient and stereoselective syntheses of 2,6-disubstituted trans-3-methylidenetetrahydropyran-4-ones and 2-(4-methoxyphenyl)-5-methylidenetetrahydropyran-4-one that significantly broaden the spectrum of the available methylidenetetrahydropyran-4-ones with various substitution patterns. Target compounds were obtained using Horner–Wadsworth–Emmons methodology for the introduction of methylidene group onto the pyranone ring. 3-Diethoxyphosphoryltetrahydropyran-4-ones, which were key intermediates in this synthesis, were prepared by fully or highly stereoselective addition of Gilman or Grignard reagents to 3-diethoxyphosphoryldihydropyran-4-ones. Addition occurred preferentially by axial attack of the Michael donors on the dihydropyranone ring. Relative configurations and conformations of the obtained adducts were assigned using a detailed analysis of the NMR spectra. The obtained methylidenepyran-4-ones were evaluated for cytotoxic activity against two cancer cell lines (HL-60 and MCF-7). 2,6-Disubstituted 3-methylidenetetrahydropyran-4-ones with isopropyl and phenyl substituents in position 2 were more cytotoxic than analogs with n-butyl substituent. Two of the most cytotoxic analogs were then selected for further investigation on the HL-60 cell line. Both analogs induced morphological changes characteristic of apoptosis in cancer cells, significantly inhibited proliferation and induced apoptotic cell death. Both compounds also generated DNA damage, and one of the analogs arrested the cell cycle of HL-60 cells in the G2/M phase. In addition, both analogs were able to inhibit the activity of topoisomerase IIα. Based on these findings, the investigated analogs may be further optimized for the development of new and effective topoisomerase II inhibitors. 相似文献
39.
Lake Szmaragdowe and Czarnog?owy Reservoir are both characterized by atypical origin as both were formed when quarries were flooded. The geological substrates of the two basins are unique, and they are both highly valued as recreational and tourist destinations. These two basins are among the most interesting in northwestern Poland. Studies of their thermal regimes confirmed that water mass mixing in Lake Szmaragdowe is bradymictic. The waters in the Czarnog?owy Reservoir mix entirely to a depth of 20 m, and this layer is also characterized by bradymixia. Deeper waters do not mix. This indicates that mixing in this basin is of the meromictic type. 相似文献
40.
Jan Marcin Węsławski Lucyna Kryla-Straszewska Jan Warzocha Jacek Urbański Maria Włodarska-Kowalczuk Lech Kotwicki 《Oceanological and hydrobiological studies.》2013,42(3):289-295
Extensive sampling (450 grabs) was performed all over the inner part of Puck Bay (105 km2 area) in summers of 2007–2009. The GIS-based analysis of samples was performed to assess in detail the distribution of 32 benthic species. The minimum area of occurrence was less than 1 km2 for Lekanosphaera rugicauda and the maximum was 83 km2 for Cerastoderma glaucum. The material reveals that species with the pelagic larval stage were most widespread, with the least distance between individuals and the highest average density (e.g. Cerastoderma glaucum, Hydrobia ventrosa). The most isolated and the least dense species within the studied area were discretely mobile, non-larval crustaceans (e.g. Gammarus oceanicus and Lekanosphaera rugicauda), present at single sites with the largest distance from each other. We conclude that analysis of species distribution helps in understanding the threats to populations of marine invertebrates and marine spatial planning, through locating the isolated species and populations. 相似文献