全文获取类型
收费全文 | 11457篇 |
免费 | 1073篇 |
国内免费 | 256篇 |
专业分类
耳鼻咽喉 | 28篇 |
儿科学 | 54篇 |
妇产科学 | 98篇 |
基础医学 | 1083篇 |
口腔科学 | 145篇 |
临床医学 | 1862篇 |
内科学 | 1415篇 |
皮肤病学 | 87篇 |
神经病学 | 502篇 |
特种医学 | 2937篇 |
外国民族医学 | 2篇 |
外科学 | 529篇 |
综合类 | 1239篇 |
现状与发展 | 1篇 |
预防医学 | 357篇 |
眼科学 | 666篇 |
药学 | 1092篇 |
5篇 | |
中国医学 | 289篇 |
肿瘤学 | 395篇 |
出版年
2024年 | 10篇 |
2023年 | 106篇 |
2022年 | 164篇 |
2021年 | 312篇 |
2020年 | 325篇 |
2019年 | 392篇 |
2018年 | 356篇 |
2017年 | 391篇 |
2016年 | 361篇 |
2015年 | 384篇 |
2014年 | 610篇 |
2013年 | 665篇 |
2012年 | 664篇 |
2011年 | 727篇 |
2010年 | 558篇 |
2009年 | 600篇 |
2008年 | 624篇 |
2007年 | 638篇 |
2006年 | 607篇 |
2005年 | 482篇 |
2004年 | 470篇 |
2003年 | 432篇 |
2002年 | 365篇 |
2001年 | 297篇 |
2000年 | 186篇 |
1999年 | 167篇 |
1998年 | 162篇 |
1997年 | 182篇 |
1996年 | 132篇 |
1995年 | 131篇 |
1994年 | 127篇 |
1993年 | 98篇 |
1992年 | 76篇 |
1991年 | 63篇 |
1990年 | 51篇 |
1989年 | 40篇 |
1988年 | 54篇 |
1987年 | 50篇 |
1986年 | 31篇 |
1985年 | 136篇 |
1984年 | 117篇 |
1983年 | 78篇 |
1982年 | 102篇 |
1981年 | 64篇 |
1980年 | 60篇 |
1979年 | 35篇 |
1978年 | 38篇 |
1977年 | 24篇 |
1976年 | 21篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
101.
102.
Besides intrinsic determinants of cell growth, epigenetic signals have been proposed to regulate development and maintenance of neurons. Here we provide evidence that cerebral astrocytes contribute significantly to the set of environmental influences that are required for long-term survival of neurons derived from the mammalian central nervous system. Cerebral astrocytes in serum-free culture express diffusible and non-diffusible neuron-supporting signals, including cell-adhesive neurite growth-promoting glycoproteins, diffusible neurotrophic factors as well as membrane-bound molecules that mediate cell contact interactions. The combination and synergistic interaction of these environmental signals markedly enhance the survival of brain neurons. While astroglia-derived cell-adhesive substrates that include a high molecular weight complex consisting of laminin β-chains and proteoglycan (Matthiessen et al., 1989) stimulate neurite outgrowth, they fail to enhance long-term neuronal survival when additional neurotrophic and cell-contact interactions are lacking. Astrocytes release a diffusible neurotrophic activity that, when permanently applied, maintains long-term survival of central neurons in culture. The soluble neurotrophic activity seems to interact synergistically with cell-bound signals which are also required for long-term survival and which are expressed by astrocytes and neurons, but not by fibroblasts. Among neurons from different brain areas, such as hippocampus, cerebral cortex and septum, regional differences in their responsiveness to the astroglial neurotrophic activity have been observed. 相似文献
103.
Fischer MH 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2001,136(2):224-230
A recent report that hand transport was sensitive to a size-contrast illusion (SCI) implied that the distinction between visual processing for perception versus action might only affect visual information obtained late during reaching. In this study, the presence of a perceptual SCI did not affect reaction time, movement time, or movement amplitude. However, both perception and action became sensitive to the SCI with memory-based responses. It is concluded that the distinction between visual processing for perception versus action does extend to hand transport. Immediate action is entirely based on veridical visuo-motor representations, whereas even slightly delayed actions begin to reflect distorted perceptual representations. 相似文献
104.
I. A. Volchegorskii A. V. Vlasov G. E. Livshits E. M. Akhkyamov N. A. Skobeleva R. I. Lifshits L. Ya. Ebert 《Bulletin of experimental biology and medicine》1995,119(2):150-153
Three identical oligopeptide-containing fractions of so-called “medium molecules”, isolated by sequential ultrafiltration
and gel chromatography from the blood of 8 intact dogs and 15 dogs with an extensive thermal burn, were examined for their
impact on phagocytic cells (neutrophil granulocytes and macrophages) in relation to the molecular-weight distribution of the
molecules. The relatively high-polymer fractions of medium molecules, unlike oligomeric fractions, stimulated the phagocytic
activity of these cells. Because of their increased polymerism, the fractions of medium molecules from dogs with thermal trauma
stimulated phagocytosis to a greater extent than did those from intact animals.
Translatedfrom Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N
o
2, pp. 159–162, February, 1995
Presented by V. A. Trufakin, Member of the Russian Academy of Medical Sciences 相似文献
105.
V. Kvedariene P. Martins L. Rouanet P. Demoly 《Clinical and experimental allergy》2006,36(8):1072-1077
Background Iodinated contrast media (ICM) hypersensitivity reactions represent a serious problem. Very few clinical data concerning systematic skin testing to ICM are available. Objective To evaluate the utility of ICM skin testing in patients with ICM hypersensitivity. Material and methods All patients referred over a 6‐year period for ICM hypersensitivity past reactions were skin tested for (a) the implicated ICM, or (b) a set of ICM if they were positive for the implicated ICM or if its name was unknown. Results Forty‐four patients, with a median age of 56 years, were studied (15 males, 29 females). The ICM skin tests were positive in 10 patients (23%): one had a positive skin prick test, seven an immediate positive intradermal test (IDT) and two a delayed positive IDT. Skin tests were more often positive in patients with immediate (9/32) as compared with those with non‐immediate reactions (1/11). The time interval between the reaction and skin testing was shorter for those patients with an immediate ICM reaction and a positive skin test result (3 months [2.5–174.0]) as compared with those with an immediate ICM reaction and a negative skin test (48 months [6.8–159.0]), (P<0.05). Respiratory allergy was more frequent in the positive group (6/10 vs. 7/34, P<0.05). Conclusions Skin tests with ICM are positive in a subgroup of patients with ICM hypersensitivity and may play an important role in the diagnosis of ICM allergy. 相似文献
106.
Human sperm chemotaxis: both the oocyte and its surrounding cumulus cells secrete sperm chemoattractants 总被引:5,自引:0,他引:5
Sun F Bahat A Gakamsky A Girsh E Katz N Giojalas LC Tur-Kaspa I Eisenbach M 《Human reproduction (Oxford, England)》2005,20(3):761-767
BACKGROUND: Human sperm chemotaxis to pre-ovulatory follicular fluid is well established in vitro. However, it is not known whether the female's oocyte-cumulus complex secretes sperm chemoattractants subsequent to ovulation (for enabling sperm chemotaxis within the Fallopian tube) and, if so, which of these cell types--the oocyte or the cumulus oophorus--is the physiological origin of the secreted chemoattractant. METHODS: By employing a directionality-based chemotaxis assay, we examined whether media conditioned with either individual, mature (metaphase II) human oocytes or the surrounding cumulus cells attract human sperm by chemotaxis. RESULTS: We observed sperm chemotaxis to each of these media, suggesting that both the oocyte and the cumulus cells secrete sperm chemoattractants. CONCLUSIONS: These observations suggest that sperm chemoattractants are secreted not only prior to ovulation within the follicle, as earlier studies have demonstrated, but also after oocyte maturation outside the follicle, and that there are two chemoattractant origins: the mature oocyte and the surrounding cumulus cells. 相似文献
107.
Metabolic pathways leading to lipid biosynthesis in four different developmental stages of Schistosoma mansoni were explored and quantified by incubation in the presence of labeled precursors in a chemically defined medium. At the schistosomulum stage and in male, female, or paired worms, glycerol and oleate incorporation into neutral lipids, mainly in the form of triacylglycerols, was greater than into phospholipids, whereas in 11-and 15-day-old worms, synthesis mainly led to phospholipids. Incorporation into phospholipids was recovered largely in phosphatidylcholine, and distribution into other phospholipids depended on the developmental stage. Incorporation of choline and ethanolamine into their respective phospholipids represented up to 15% of the parasitic phospholipid content. The formation of phosphatidylcholine by phosphatidylethanolamine methylation occurred mainly in the immature parasitic stages. Inositol incorporation was also measurable, whereas [14C]serine incorporation was low or undetectable. Addition of 1-palmitoyl-2-[14C]oleyl phosphatidylcholine revealed a very high uptake of this phospholipid by the immature stages but further metabolism was not detectable. In contrast, adult S. mansoni were completely unable to take up or absorb this exogenous phospholipid. The most striking aspect of this study was the relatively high metabolic activity in 11-day-old worms and the lower but sustained activity on day 15 and at the schistosomulum stage. By comparison, biosynthetic activity in adult S. mansoni, on which research studies have been focused until now, was very low. We also discuss the participation of lipid metabolism in the constant renewal of the membrane complex which is essential to parasitism by S. mansoni. 相似文献
108.
本文制备了巨噬细胞条件培养基(MφCM),并应用快速自动比色微量分析法检测MφCM对体外培养的生后7dSD大鼠小脑皮质神经元的作用。结果表明,分子量大于10kD的MφCM对神经元(细胞密度1×106/ml)的作用,与对照组比较有明显的神经营养活性(F<0.05);用盖玻片培养法表明,该组份有促进神经元突起生长的作用。MφCM经SephacrylS-100-HR凝胶层析和生物活性鉴定,获得了具有神经营养活性的第二峰洗脱液。此洗脱液经SDS-聚丙烯酰胺凝胶电泳分析,证明MφCM中神经营养活性成份的蛋白质其分子量为31kD-68kD之间。 相似文献
109.
Using the soft-agar colony assay, we have generated three MT3-associated clones: HJ1, HJ13, and HJ39, from an MLR combination of two unrelated individuals. Another clone, HJ37, appeared to recognize a novel HLA-D determinant. PLT inhibition studies with monoclonal anti-Ia-like antibodies (Mab) were conducted on clones HJ1, HJ39, and HJ37. Five different anti-DR Mab had no significant inhibitory effect on these clones. On the other hand, two Mab SG171 and Q5/13 which appear to react with DR and MT3 (I-A like) molecules strongly inhibited the two MT3-specific PLT clones. While SG171 and Q5/13 had little effect on HJ37, it was observed that a polymorphic Mab 17.15 had a strong inhibitory effect. These results, in concordance with biochemical data on Ia molecules precipitated by these Mab, suggest that these alloreactive clones may recognize non-DR PLT determinants. They also provide further indirect support that MT3 molecules represent the human homologue of murine I-A molecules. 相似文献
110.
《Acta histochemica》2022,124(4):151895
Cancer is a disease characterised by abnormal cell growth that can invade or spread to other regions of the body. Organoids are three-dimensional ex vivo tissue cultures made from embryonic stem cells, induced pluripotent stem cells, progenitor cells or tissue that serve as a physiological model for cancer research. These are designed to recapitulate the in vivo properties of tumours. Importantly, effective recapitulation of the structure of tissues and function is believed to predict patient response, allowing for the creation of personalised therapy in a timely manner that may be used in the clinic. This Review discusses the pre-clinical model and different types of human organoids as models for the development of high throughput drug screening and also aims to highlight how organoids are shaping the future of cancer research. 相似文献