首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13244篇
  免费   1163篇
  国内免费   810篇
耳鼻咽喉   105篇
儿科学   110篇
妇产科学   121篇
基础医学   1449篇
口腔科学   209篇
临床医学   1589篇
内科学   1972篇
皮肤病学   279篇
神经病学   677篇
特种医学   468篇
外国民族医学   5篇
外科学   1304篇
综合类   2260篇
现状与发展   6篇
一般理论   1篇
预防医学   871篇
眼科学   411篇
药学   1373篇
  9篇
中国医学   667篇
肿瘤学   1331篇
  2024年   44篇
  2023年   211篇
  2022年   477篇
  2021年   627篇
  2020年   454篇
  2019年   384篇
  2018年   424篇
  2017年   404篇
  2016年   402篇
  2015年   586篇
  2014年   693篇
  2013年   698篇
  2012年   997篇
  2011年   1035篇
  2010年   661篇
  2009年   560篇
  2008年   695篇
  2007年   766篇
  2006年   640篇
  2005年   607篇
  2004年   598篇
  2003年   564篇
  2002年   515篇
  2001年   440篇
  2000年   318篇
  1999年   302篇
  1998年   155篇
  1997年   168篇
  1996年   133篇
  1995年   113篇
  1994年   121篇
  1993年   68篇
  1992年   78篇
  1991年   56篇
  1990年   32篇
  1989年   38篇
  1988年   30篇
  1987年   35篇
  1986年   29篇
  1985年   16篇
  1984年   10篇
  1983年   8篇
  1982年   7篇
  1981年   4篇
  1980年   2篇
  1979年   4篇
  1977年   2篇
  1971年   1篇
  1970年   1篇
  1964年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
腺病毒载体介导的lacZ基因在NG细胞系及大鼠黑质的表达   总被引:1,自引:0,他引:1  
本实验用标记基因lacZ5型重组腺病毒(Ad5CMVlacZ)转染培养的NG细胞系,X-gal染色检测转染效率.在培养的NG细胞系,当病毒滴度为2×108时,转集率达到50%,当滴度为2×109时,转染率达100%,有较好的量效关系;固定病毒液度为1010,培养2~16h,细胞的转染率随时间延长而提高,有较好的时效关系。将Ad5CMVlacZ注射到大鼠黑质部位后,分别于注射后3~120d取脑、切片、X-gal染色,发现黑质局部从第7d开始有部分蓝染,第10d达高峰,注射局部感染率100%;90d时开始下降,持续至120d;纹状体等其它部位无蓝染.上述结果提示,腺病毒载体介导的标记基因可在培养的神经细胞系和中脑黑质部位高效表达,为进一步开展中枢神经系统退变性疾病尤其是帕金森氏病的基因治疗奠定基础。  相似文献   
52.
检测了42例健康儿童和17例反复上呼吸道感染患儿(复感儿)的血淋巴细胞腺苷脱氨酶(ADA)活性,结果表明:复感儿的血淋巴细胞中ADA活性较健康儿童低下,且大多同样伴有不同程度的免疫功能低下;从复感儿组中筛选了两侧ADA活性和免疫功能明显低下的患儿,拟采用这两例患儿的血淋巴细胞进行ADA-SCID基因治疗的实验研究。  相似文献   
53.
Li J  You Z  Chen Z  Song C  Lu C 《Neuroscience letters》2001,300(1):54-58
Effect of chronic morphine treatment on oxytocin (OT) release from the long term-cultured organotypic slice of the supraoptic nucleus (SON) was investigated using radioimmunoassay. The co-localization of oxytocin and mu-opioid receptor in neurons within the SON was observed with the double-labeled methods of in situ hybridization combined with immunohistochemistry. After exposure to morphine for 6days, the OT levels in culture media were significantly decreased. Naloxone caused much greater release of OT in chronic morphine treatment group than in controls. Naloxone has no effect after acute morphine treatment. 90% of OT-ir (immunoreactive) neurons expressed mu-opioid receptor mRNA in the SON and 45% of the neurons that expressed mu-opioid receptor mRNAs were OT-ir neurons. These results indicated that the neurons within SON could develop dependence on morphine in vitro, and these effects might be exerted via mu-opioid receptor in oxytocin neurons of the SON.  相似文献   
54.
Vascular endothelial growth factor-receptors (VEGF-Rs) are pivotal regulators of vascular development, but a specific role for these receptors in the formation of heart valves has not been identified. We took advantage of small molecule inhibitors of VEGF-R signaling and showed that blocking VEGF-R signaling with receptor selective tyrosine kinase inhibitors, PTK 787 and AAC 787, from 17-21 hr post-fertilization (hpf) in zebrafish embryos resulted in a functional and structural defect in cardiac valve development. Regurgitation of blood between the two chambers of the heart, as well as a loss of cell-restricted expression of the valve differentiation markers notch 1b and bone morphogenetic protein-4 (bmp-4), was readily apparent in treated embryos. In addition, microangiography revealed a loss of a definitive atrioventricular constriction in treated embryos. Taken together, these data demonstrate a novel function for VEGF-Rs in the endocardial endothelium of the developing cardiac valve.  相似文献   
55.
TCP80 is an approximately 80kDa mammalian cytoplasmic protein that binds to a set of mRNAs and inhibits their translation in vitro and ex vivo. This protein has high sequence similarity to interleukin-2 enhancer-binding factors (NF90/ILF3) and the M-phase phosphoprotein (MPP4)/DRBP76. A 110kDa immunologic isoform of TCP80/NF90/MPP4/DRBP76, termed TCP110, also is present in cytoplasm and nuclei of many types of cells. A cDNA sequence coding for TCP110 was derived by 5(')RACE. The TCP110 sequence is identical to ILF3. The gene coding for TCP110/ILF3 mapped to human chromosome 19 and the gene organization was analyzed using TCP80 and TCP110/ILF3 cDNA sequences. The TCP/ILF3 gene spans >34.8kb and contains 21 exons. At least one alternatively spliced product involving exons 19-21 exists and predicts the formation of either TCP80 or TCP110/ILF3. However, the functional relationships of TCP80 and TCP110/ILF3 required elucidation. The metabolic turnover rates and subcellular distribution of TCP80 and TCP110/ILF3 during the cell cycle showed TCP80 to be relatively stable (t(1/2)=5 days) in the cytoplasmic compartment. In comparison, TCP110/ILF3 migrated between the cytoplasmic and nuclear compartments during the cell cycle. The TCP110 C-terminal segment contains an additional nuclear localizing signal that plays a role in its nuclear translocation. This study indicates that the multiple cellular functions, i.e., translation control, interleukin-2 enhancer binding, or cell division, of TCP/ILF3 are fulfilled by alternatively spliced isoforms.  相似文献   
56.
基质金属蛋白酶1与冠状动脉粥样硬化斑块破裂的关系   总被引:28,自引:2,他引:28  
Guo A  Wei L  Shi H  Li X  You L 《中华病理学杂志》2000,29(4):263-268
目的 探讨冠状动脉粥样硬化斑块破裂与基质金属蛋白酶1(MMP-1)的关系,以及不稳定斑块中MMP-1的来源。方法 收集20例死于急性心肌梗死、10例有不稳定心绞痛史,以及12例有稳定心绞痛史的尸体解剖病例共42例,从冠状动脉各分支取材,常规病理检查、部分节段行MMP-1、平滑肌肌动蛋白、CD68、CD45RO和CD20洒色。结果 在急性心肌梗死及不稳定心绞痛病例中,均见有斑块破裂伴血栓形成,而在稳  相似文献   
57.
目的 探讨酒精对小鼠睾丸的组织结构、内皮型一氧化氮合酶 (eNOS)、增殖细胞核抗原 (PCNA)及细胞凋亡的影响。 方法 用 5 %、10 %及 15 % 3种不同浓度的酒精作用于 2 2d龄小鼠 ,取睾丸做石蜡切片、HE染色 ;用免疫组织化学方法检测睾丸eNOS、细胞增殖的变化 ;TUNEL法检测细胞凋亡的变化 ,并进行统计学分析。 结果 随着酒精浓度的增大 ,睾丸组织结构发生明显改变 ,生精小管的直径逐渐减小 ,eNOS阳性细胞面积密度逐渐增大 ,单位面积内PCNA阳性细胞和凋亡细胞数目增加 ,高浓度酒精组与其他组差异极显著 (P <0 0 1)。 结论 酒精可使生精小管的直径变小 ,eNOS及PCNA表达增强 ,凋亡细胞增加并随酒精浓度的增大而变化加重。这可能是过量饮酒导致生精细胞减少 ,生殖能力降低的重要因素。  相似文献   
58.
Nonmyelinated (C-) fibers represent the majority of vagal afferents innervating the airways and lung, and play an important role in regulating the respiratory and cardiovascular functions under both normal and abnormal physiologic conditions. Studies of the relationship between the conduction velocities of the vagal afferents and their sensitivities to capsaicin and other chemical irritants reveal that C-fibers are the primary type of chemosensitive afferents in the rat lung. Furthermore, a distinct sensitivity to capsaicin and a weak response to lung inflation are the defining characteristics of these afferents. In cultured rat nodose and jugular ganglion neurons, capsaicin-sensitive cells were identified by measurement of the capsaicin-evoked calcium transients using the Fura-2-based ratiometric imaging technique. The percentage of capsaicin-sensitive neurons gradually decreases as the cell diameter increases. However, the capsaicin-sensitive neurons cannot be precisely identified solely on the basis of the cell size. Anandamide, an endogenous cannabinoid released from leukocytes and epithelial cells, consistently evokes a stimulatory effect on pulmonary C-fiber endings by activating vanilloid receptor type 1 (VR1). The discharge pattern of pulmonary C-fibers evoked by anandamide closely resembles that produced by a much lower ( approximately 1/600) dose of capsaicin in the same fibers. Whether anandamide acts as a potential endogenous ligand to VR1 at the C-fiber terminals is unclear, and the physiological role of VR1 in modulating the transduction properties of these afferents also remains to be determined.  相似文献   
59.
Hu WP  You XH  Guan BC  Ru LQ  Chen JG  Li ZW 《Neuroscience letters》2004,365(2):147-152
The present study aimed to investigate the interaction between the coexistent SP receptor and 5-HT3 receptor in trigeminal ganglion (TG) neurons using whole-cell patch clamp technique. The majority of the neurons examined responded to 5-HT with an inward current (I5-HT) (78.2%, 79/101) that could be blocked by 5-HT3 receptor antagonist, ICS-205,930. The I5-HT was potentiated by preapplication of SP (10(-10) to 10(-8) M) in most 5-HT-sensitive cells(78.5%, 62/79). Coapplication of SP and GR-82334, antagonist of NK1 receptor, had no enhancing effect on I5-HT. The concentration-response curves for 5-HT with and without SP preapplication show that: (1) the threshold 5-HT concentrations with and without SP preapplication are basically the same, while SP preapplication increased the maximal value of I5-HT by 38.0% of its control; (2) the EC50 values of the curves with and without SP pretreatment are very close, i.e. 1.89 x 10(-5) M and 2.08 x 10(-5) M (P > 0.1; n = 9), respectively. Intracellular dialysis of GDP-beta-S, a non-hydrolyzable GDP analog, and GF-109203X, a selective protein kinase C inhibitor, removed the SP potentiation of I5-HT. These results may offer a clue to understanding the mechanism underlying the generation and/or regulation of peripheral pain caused by tissue damage inflammation, etc.  相似文献   
60.
Gao Q  Wu B  Zhang J  You J  Zhong H  Fang W 《中华病理学杂志》1999,28(3):191-193
目的 探讨Ⅰ型膜型基质金属蛋白酶在人肿瘤细胞系中的表达情况及其与明胶酶的分泌和活化的关系。方法 运用逆转录巢式PCR,RNA印迹分析和蛋白质印迹分析的方法,检测MT1-MMP,mRN和MMP2蛋白在4个黑色素瘤,2个肺癌和2个前列腺癌细胞系中的表达水平。结果 MT1-MMPmRNA在所有癌细胞系中均有表达,但表达水平很不一致;在4个黑色素瘤细胞系中的表达水平明显高于肺癌和前列腺癌细胞系;  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号