全文获取类型
收费全文 | 19161篇 |
免费 | 1167篇 |
国内免费 | 248篇 |
专业分类
耳鼻咽喉 | 468篇 |
儿科学 | 243篇 |
妇产科学 | 319篇 |
基础医学 | 3193篇 |
口腔科学 | 355篇 |
临床医学 | 1419篇 |
内科学 | 3830篇 |
皮肤病学 | 542篇 |
神经病学 | 1462篇 |
特种医学 | 1314篇 |
外科学 | 2575篇 |
综合类 | 95篇 |
现状与发展 | 3篇 |
一般理论 | 13篇 |
预防医学 | 697篇 |
眼科学 | 482篇 |
药学 | 1668篇 |
中国医学 | 234篇 |
肿瘤学 | 1664篇 |
出版年
2024年 | 15篇 |
2023年 | 160篇 |
2022年 | 460篇 |
2021年 | 778篇 |
2020年 | 333篇 |
2019年 | 537篇 |
2018年 | 641篇 |
2017年 | 484篇 |
2016年 | 761篇 |
2015年 | 1077篇 |
2014年 | 1169篇 |
2013年 | 1296篇 |
2012年 | 1921篇 |
2011年 | 1767篇 |
2010年 | 1063篇 |
2009年 | 903篇 |
2008年 | 1153篇 |
2007年 | 1143篇 |
2006年 | 963篇 |
2005年 | 794篇 |
2004年 | 646篇 |
2003年 | 570篇 |
2002年 | 467篇 |
2001年 | 309篇 |
2000年 | 256篇 |
1999年 | 181篇 |
1998年 | 87篇 |
1997年 | 75篇 |
1996年 | 42篇 |
1995年 | 43篇 |
1994年 | 33篇 |
1993年 | 32篇 |
1992年 | 43篇 |
1991年 | 45篇 |
1990年 | 36篇 |
1989年 | 41篇 |
1988年 | 33篇 |
1987年 | 36篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
In order to determine the effect of ultraviolet radiation (UVR) on the cell adhesion molecules expressed in human dermal microvascular endothelial cells (HDMEC), the cells were exposed to varying UVR doses and the cell surface was examined for expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM- 1), and E-selectin. The effect of UVB irradiation on the binding of T lymphocytes to HDMEC was also examined. UVA irradiation did not affect the surface expression of ICAM-1, VCAM-1, or E-selectin on the HDMEC. However, following UVB exposure, ELISA demonstrated a significant increase in the baseline ICAM-1 cell surface expression on the HDMEC. However, no induction of either E-selectin or VCAM-1 was noted. UVB also significantly augmented ICAM-1 induction by IL-1alpha and TNF-alpha. VCAM-1 was induced by stimulating HDMEC with IL-1alpha following a UVB irradiation dose of 100 mJ/cm2. Flow cytometric analysis of the HDMEC stimulated with IL-1alpha for 24h demonstrated that 12% of the cells expressed VCAM-1 but either IL-1alpha or UVB irradiation alone failed to induce VCAM-1 expression. Enhancement of T cell-HDMEC binding by IL-1alpha or TNF-alpha treatment was not significantly affected after UVB irradiation. This study demonstrated that UVB irradiation can alter ICAM-1 and VCAM-1 expression on the HDMEC surface and that augmentation of ICAM-1 expression and the IL-1alpha-dependent induction of VCAM-1 following UVB exposure might be important steps in the pathogenesis of sunburn. 相似文献
82.
Byoung Won Kang Kazuyuki Hattori Takashi Yoshida Makoto Hirai Yoon Soung Chio Toshiyuki Uryu 《Macromolecular chemistry and physics.》1997,198(5):1331-1345
Ring-opening polymerization of a new anhydro ribose-type monomer, 1,4-anhydro-3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-α-D -ribopyranose (A3ASR), was investigated. The monomer was synthesized from 1,4-anhyro-α-D -xylopyranose by three steps comprising Walden inversion at the C3 position into ribose configuration. Ring-opening polymerization of A3ASR by Lewis acid catalysts such as boron trifluoride etherate and stannic chloride gave a stereoregular 3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-(1→5)-α-D -ribofuranan having specific rotations of +246 ~ +271 deg · dm?1 · g?1 · cm3 and number-average molecular weights of 18,7 × 103 ~ 25,1 × 103. When the polymerization was carried out by antimony pentachloride at 0°C, the resulting polymer exhibited a negative specific rotation of ?6 deg · dm?1 · g?1 · cm3 and the C1 absorption in the 13C NMR spectrum shifted downfield to 107,5 ppm, suggesting that the polymer might consist of 1,5-β furanosidic unit. The reduction of the azido group of the 1,5-α and 1,5-β furanosidic polymers into amino group and subsequent desilylation gave 3-amino-3-deoxy-(1→5)-α- and -β-D -ribofuranans, respectively. In addition, copolymerization of A3ASR with 1,4-anhydro-2,3-di-O-tert-butyldimethylsilyl-α-D -ribopyranose (ADSR) in various feeds was performed by boron trifluoride etherate as catalyst to give copolymers with different monomeric components. The structural analysis of the homopolymers and copolymers was examined by means of 1H and 13C NMR spectroscopies, IR spectroscopy, and optical rotation. 相似文献
83.
The progressive myoclonus epilepsy of the Lafora type (LD; MIM 254780) is a rare autosomal recessive disorder characterized by epilepsy, myoclonus, progressive neurological deterioration, and the presence of periodic acid-Schiff-positive polyglucosan inclusions (Lafora bodies). Mutations in the EPM2A gene have recently been found to cause LD and about 30 or more mutations have been reported thus far. LD is relatively common in countries of the Mediterranean Basin, the Middle East, India, and Pakistan. Although a few sporadic cases with the typical LD phenotype have also been reported in the Far East including Korea and Japan, a recent effort to find mutations in Japanese LD families was not successful. In the present study, we report two novel mutations in a Korean girl with LD; a 1-bp insertion mutation (c.223insC; G75fsX107) in exon 1 and a missense mutation (c.559A>G; T187A) in exon 3 of the EPM2A gene. To our knowledge, this is the first report of a genetically confirmed case of LD in Koreans and also in the Far East. 相似文献
84.
Malignant transformation of mature cystic teratoma of the ovary can develop with an incidence of 1-2%. Squamous cell carcinoma is the most common malignant tumor arising in benign cystic teratoma. The authors have recently experienced a case of combined microcystic adnexal carcinoma and squamous cell carcinoma arising in a benign cystic teratoma of the ovary in a 72-year-old Korean woman. The right ovarian cystic mass had been ruptured and firmly adhered with salpinx and omental fat tissue on operation. Thickened cystic wall with yellowish white solid infiltrative lesion was noted grossly, and two different malignant tumors of microcystic adnexal carcinoma exhibiting both eccrine and hair follicular differentiation and squamous cell carcinoma were observed microscopically. PAS and CEA positivities suggested eccrine differentiation in areas of microcystic adnexal carcinoma. 相似文献
85.
The diabetogenic capacity of the M-variant of encephalomyocarditis (EMC) virus was markedly diminished after passage in mouse kidney cell cultures. One passage in mice fully restored this capacity. Virus harvested after five passages in either susceptible (SWR/J) or resistant (C57BL/6J) strains of mice was capable of producing diabetes in susceptible SWR/J mice but not in resistant C57BL/6J mice. Resistance was not overcome by inoculating mice with high concentrations of virus. Immunofluorescence studies showed that islets from strains of mice (i.e. CBA, AKR, C57BL/6J, A/J) that did not develop diabetes after infection with EMC virus, nonetheless, contained virus antigens. The percentage of cells in the islets containing virus antigens varied from 3-6% in CBA to 13-5% in A/J. In contrast 38% of the islet cells in susceptible SWR/J mice contained virus antigens. It is concluded that both the genetic background of the host and the passage history of the virus influence the development of diabetes. 相似文献
86.
Yoon JH Lee HV Lee JS Park JB Kim CY 《The International journal of artificial organs》1999,22(11):769-777
There is a need to develop human hepatocyte cell lines which retain both replicating capacity and highly differentiated functions to facilitate the development of an efficient bioartificial liver. The present study was undertaken to differentiate, using sodium butyrate, the actively replicating immortalized human liver cell line. The effects of butyrate on cell growth and cell cycle were analyzed, and the albumin synthesis, cytochrome P450 and ammonia-detoxifying activity of the butyrate-treated cells were measured. Butyrate treatment resulted in G2/M arrest of the cell cycle and polygonal changes in the cell morphology. Neither the control nor the butyrate-treated cells showed transformed characteristics. Butyrate treatment increased the amount of albumin secretion, cytochrome P450 activity, and the urea production rate of the cells. The present study provides non-transformed human hepatocytes, which can replicate unlimitedly and then restore differentiated hepatocyte-specific functions by butyrate, and therefore, have applications for the development of an efficient bioartificial liver. 相似文献
87.
Missing data such as appropriateness ratings in clinical research are a common problem and this often yields a biased result. This paper aims to introduce the multiple imputation method to handle missing data in clinical research and to suggest that the multiple imputation technique can give more accurate estimates than those of a complete-case analysis. The idea of multiple imputation is that each missing value is replaced with more than one plausible value. The appropriateness method was developed as a pragmatic solution to problem of trying to assess "appropriate" surgical and medical procedures for patients. Cataract surgery was selected as one of four procedures that were evaluated as a part of the Clinical Appropriateness Initiative. We created mild to high missing rates of 10%, 30% and 50% and compared the performance of logistic regression in cataract surgery. We treated the coefficients in the original data as true parameters and compared them with the other results. In the mild missing rate (10%), the deviation from the true coefficients was quite small and ignorable. After removing the missing data, the complete-case analysis did not reveal any serious bias. However, as the missing rate increased, the bias was not ignorable and it distorted the result. This simulation study suggests that a multiple imputation technique can give more accurate estimates than those of a complete-case analysis, especially for moderate to high missing rates (30 - 50%). In addition, the multiple imputation technique yields better accuracy than a single imputation technique. Therefore, multiple imputation is useful and efficient for a situation in clinical research where there is large amounts of missing data. 相似文献
88.
Kim SN Rhee JH Song YH Park DY Hwang M Lee SL Kim JE Gim BS Yoon JH Kim YJ Kim-Ha J 《Neurobiology of aging》2005,26(7):1083-1091
Previous gene expression profiling studies in Drosophila have provided clues for understanding the aging process at the gene expression level. For a detailed understanding, studies of specific regions of the body are necessary. We therefore employed microarray analysis to examine gene expression changes in the Drosophila head during aging. Six hundred and eighty-four of the 5405 genes present in the microarray showed significant age-dependent changes as determined by significance analysis of microarray (SAM) (q < 0.05). The biological significance of the changes was analyzed using the gene annotations provided by the Gene Ontology Consortium. Major changes involved genes affecting energy metabolism (proton transport, energy pathways, oxidative phosphorylation) and neuronal function, especially responses to light. Genes involved in protein catabolism and several other metabolic processes also showed age-dependent changes. Most of the changes were reductions in gene expression and occurred before day 13 of adult life. After day 13, the age-dependent gene expression changes were relatively smaller than earlier life. Interestingly, the two biological processes of major gene expression changes are related to the two known environmental changes that increase life span in Drosophila: caloric restriction and light reduction. Our findings suggest that light signaling and energy metabolism may be important biological processes affected by aging and be interesting targets for the further investigation related to the longevity in Drosophila. 相似文献
89.
90.
Irina Maljkovic Berry Melanie C. Melendrez Simon Pollett Katherine Figueroa Darunee Buddhari Chonticha Klungthong Ananda Nisalak Michael Panciera Butsaya Thaisomboonsuk Tao Li Tyghe G. Vallard Louis Macareo In-Kyu Yoon Stephen J. Thomas Timothy Endy Richard G. Jarman 《Emerging infectious diseases》2021,27(6):1637
Dengue control approaches are best informed by granular spatial epidemiology of these viruses, yet reconstruction of inter- and intra-household transmissions is limited when analyzing case count, serologic, or genomic consensus sequence data. To determine viral spread on a finer spatial scale, we extended phylogenomic discrete trait analyses to reconstructions of house-to-house transmissions within a prospective cluster study in Kamphaeng Phet, Thailand. For additional resolution and transmission confirmation, we mapped dengue intra-host single nucleotide variants on the taxa of these time-scaled phylogenies. This approach confirmed 19 household transmissions and revealed that dengue disperses an average of 70 m per day between households in these communities. We describe an evolutionary biology framework for the resolution of dengue transmissions that cannot be differentiated based on epidemiologic and consensus genome data alone. This framework can be used as a public health tool to inform control approaches and enable precise tracing of dengue transmissions. 相似文献