全文获取类型
收费全文 | 10688篇 |
免费 | 753篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 78篇 |
儿科学 | 297篇 |
妇产科学 | 310篇 |
基础医学 | 1431篇 |
口腔科学 | 233篇 |
临床医学 | 1305篇 |
内科学 | 2160篇 |
皮肤病学 | 271篇 |
神经病学 | 1114篇 |
特种医学 | 203篇 |
外科学 | 942篇 |
综合类 | 64篇 |
一般理论 | 17篇 |
预防医学 | 1332篇 |
眼科学 | 181篇 |
药学 | 731篇 |
中国医学 | 32篇 |
肿瘤学 | 779篇 |
出版年
2023年 | 137篇 |
2022年 | 229篇 |
2021年 | 466篇 |
2020年 | 266篇 |
2019年 | 368篇 |
2018年 | 385篇 |
2017年 | 280篇 |
2016年 | 321篇 |
2015年 | 330篇 |
2014年 | 406篇 |
2013年 | 608篇 |
2012年 | 863篇 |
2011年 | 842篇 |
2010年 | 485篇 |
2009年 | 381篇 |
2008年 | 646篇 |
2007年 | 637篇 |
2006年 | 592篇 |
2005年 | 561篇 |
2004年 | 481篇 |
2003年 | 453篇 |
2002年 | 403篇 |
2001年 | 60篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 68篇 |
1997年 | 71篇 |
1996年 | 64篇 |
1995年 | 53篇 |
1994年 | 40篇 |
1993年 | 46篇 |
1992年 | 36篇 |
1991年 | 37篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 41篇 |
1986年 | 34篇 |
1985年 | 30篇 |
1984年 | 39篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 37篇 |
1980年 | 41篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1975年 | 16篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1970年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Liu XH Kirschenbaum A Yao S Stearns ME Holland JF Claffey K Levine AC 《Clinical & experimental metastasis》1999,17(8):687-694
Upregulation of vascular endothelial growth factor (VEGF) expression induced by hypoxia is crucial event leading to neovascularization.
Cyclooxygenase-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, has been
demonstrated to be induced by hypoxia and play role in angiogenesis and metastasis. To investigate the potential effect of
COX-2 on hypoxia-induced VEGF expression in prostate cancer. We examined the relationship between COX-2 expression and VEGF
induction in response to cobalt chloride (CoCl2)-simulated hypoxia in three human prostate cancer cell lines with differing biological phenotypes. Northern blotting and
ELISA revealed that all three tested cell lines constitutively expressed VEGF mRNA, and secreted VEGF protein to different
degrees (LNCaP > PC-3 > PC3ML). However, these cell lines differed in the ability to produce VEGF in the presence of CoCl2-simulated hypoxia. CoCl2 treatment resulted in 40% and 75% increases in VEGF mRNA, and 50% and 95% in protein secretion by LNCaP and PC-3 cell lines,
respectively. In contrast, PC-3ML cell line, a PC-3 subline with highly invasive, metastatic phenotype, exhibits a dramatic
upregulation of VEGF, 5.6-fold in mRNA and 6.3-fold in protein secretion after treatment with CoCl2. The upregulation of VEGF in PC-3ML cells is accompanied by a persistent induction of COX-2 mRNA (6.5-fold) and protein (5-fold).
Whereas COX-2 expression is only transiently induced in PC-3 cells and not affected by CoCl2 in LNCaP cells. Moreover, the increases in VEGF mRNA and protein secretion induced by CoCl2 in PC-3ML cells were significantly suppressed following exposure to NS398, a selective COX-2 inhibitor. Finally, the effect
of COX-2 inhibition on CoCl2-induced VEGF production was reversed by the treatment with exogenous PGE2. Our data demonstrate that VEGF induction by cobalt chloride-simulated hypoxia is maintained by a concomitant, persistent
induction of COX-2 expression and sustained elevation of PGE2 synthesis in a human metastatic prostate cancer cell line, and suggest that COX-2 activity, reflected by PGE2 production, is involved in hypoxia-induced VEGF expression, and thus, modulates prostatic tumor angiogenesis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
42.
Alice H. Dodge Mark Brownfield Ian A. Reid Tadashi Inagami 《Developmental dynamics》1988,182(4):347-352
Diethylstilbestrol (DES) treatment of a male Syrian hamster resulted in the development of a renal tumor and its widely scattered scrosal metastases. Cells in both the primary tumor and metastatic nodules contained secretory granules. The tumors were transplanted serially into DES-supported and non-DES-supported host hamsters until DES-independent tumors developed. Rabbit antiserum to mouse salivary renin and rabbit antiserum to rat kidney resin were reacted with sections of the primary tumor, metastatic nodules, and all transport tumors. The sections were stained by the PAP and Vector-ABC-AP procedures. Renin-positive material was observed in all tumors. Plasma renin activity (PRA) was determined for the host hamsters carrying the renal tumor transplants and compared to the PRA values that had been determined for normal non-DES-treated male and female hamsters. It was found that the average PRA values of host hamsters carrying the tumor transplants were significantly higher than the normal PRA ralues. 相似文献
43.
Vesicular stomatitis virus (VSV), when reproduced in human tumor cell lines, assembled a specific subset of cell-derived proteins. These were detected by [35S]methionine labeling of cells prior to infection and subsequent immunoprecipitation of VSV grown in these cells, as well as by direct immunoprecipitation of labeled cell extracts with antiserum directed against the VSV-assembled proteins. Their molecular weight (Mr) ranged between 15K and 180K; the larger proteins were glycosylated. Two of the major protein species (gp88 and gp130) were common to all four cell lines used (HeLa—cervical carcinoma, T47D—breast carcinoma, and HMB2 and SK1477—two melanoma cell lines). Proteins of other molecular weights were detected only in one or two of the cell lines. The melanoma cell lines (even in the absence of VSV) shed large particulate material which had contained the same spectrum of proteins that were assembled by VSV. The major protein component had an Mr of 30K. Some of the VSV-assembled proteins might possibly serve as specific tumor markers. It is also conceivable that the proteins assembled by VSV as well as the large particulate material might be products of defective endogenous human retroviruses. 相似文献
44.
Maoxin Wu Lurmag Orta Joan Gil Gan Li Alice Hu David E Burstein 《Modern pathology》2008,21(5):553-558
The critical distinction of bronchioloalveolar carcinoma (BAC), well-differentiated adenocarcinoma (WDAC) of lung, adenomatous hyperplasia (AH) and atypical adenomatous hyperplasia (AAH), is based on morphological criteria alone, and is therefore potentially subjective. We examined expression of two markers, X-linked inhibitor of apoptosis protein (XIAP), the most potent of the inhibitor of apoptosis protein (IAP) family, and p63, a marker of bronchial reserve cells (BRC) and squamous cells, in these entities. H&E slides of 37 tissue blocks from 27 patients were reviewed and classified as AH (n=7), AAH (n=8), BAC (n=9) and WDAC (n=13). Immunostaining was performed on 4 mum sections with monoclonal anti-XIAP and monoclonal anti-p63. Granular or heterogeneous cytoplasmic staining for XIAP and nuclear staining for p63 were considered positive. Neither XIAP nor p63 were detected in normal lung alveolar cells. All seven AHs were negative for XIAP and negative or focally positive for p63. All eight AAHs were positive for XIAP and displayed p63 positivity in scattered cells. All BACs displayed XIAP positivity, which ranged from focal/weak to diffuse/strong. p63 was negative in seven and focally positive in two of nine BACs. Twelve of 13 WDACs showed XIAP positivity in a similar pattern to BAC; all were negative for p63. One aberrant case diagnosed on H & E as WDAC was negative for XIAP but strongly positive for p63. Significant XIAP expression appears to be useful for distinguishing AAH from AH. Commonality of XIAP staining in AAH, BAC and WDAC supports the possibility that AAH may be a pre-malignant lesion. The rarity of p63 expression confirms previous reports and supports a nonbronchial histogenesis of these entities. In contrast, diffuse p63 staining may facilitate the identification of rare cases that may have been misclassified as alveolar in origin based on morphology but may be of BRC origin. 相似文献
45.
46.
Summary
Gaeumannomyces graminis var.graminis andtritici were transformed to benomyl resistance using pBT3, a plasmid encoding fungicide-resistant -tubulin. Either circular or linear plasmid DNA producedG. graminis var.graminis transformants in which plasmid DNA was integrated into the fungal genome. There was no evidence for autonomous plasmid replication in any of the transformants examined. 4/11 linear DNA transformants had a single plasmid copy, whereas 8/9 circular DNA transformants had multiple copies of the plasmid. Integration of transforming DNA occurred by nonhomologous recombination in all (20/20) of these transformants. 相似文献
47.
We have previously demonstrated that p100H mutant mice, which lack a functional Sox6 gene, exhibit skeletal and cardiac muscle degeneration and develop cardiac conduction abnormalities soon after birth. To understand the role of Sox6 in skeletal muscle development, we identified muscle-specific genes differentially expressed between wild-type and p100H mutant skeletal muscles and investigated their temporal expression in the mutant muscle. We found that, in the mutant skeletal muscle, slow fiber and cardiac isoform genes are expressed at significantly higher levels, whereas fast fiber isoform genes are expressed at significantly lower levels than wild-type. Onset of this aberrant fiber type-specific gene expression in the mutant coincides with the beginning of the secondary myotube formation, at embryonic day 15-16 in mice. Together with our earlier report, demonstrating early postnatal muscle defects in the Sox6 null-p100H mutant, the present results suggest that Sox6 likely plays an important role in muscle development. 相似文献
48.
The isthmo-optic nuclei (ION) and ectopic neurons, which constitute the centrifugal visual system (CVS), are thought to be cholinoceptive and nitrergic. However, it is not clear which neurons express these markers, namely the ones that project to the retina rather than in neurons that only participate in a local circuit. Therefore, to characterize the neurochemical patterns of the centrifugal visual system in the post-hatched chick, retinopetal cells of the isthmo-optic nuclei and the ectopic region were identified via immunolabeling for cholera toxin, a neuronal tracer, which has been injected in the ocular globe. Then, double labeled with acetylcholinesterase histochemistry to reveal cholinergic synapses, or NADPH-diaphorase histochemistry as a nitrergic marker. Briefly, acetylcholinesterase activity was present mainly in cholera toxin labeled cell bodies of the isthmo-optic nucleus and the ectopic region indicating that retinal projecting neurons of centrifugal visual system comprise a cholinoceptive pathway. On the other hand, NADPH-diaphorase histochemistry was present in the neuropile and sparse cell bodies inside of the isthmo-optic nucleus and in ectopic neurons which were not cholera toxin positive suggesting their role in an intrinsic circuit of the centrifugal visual system. These data support the idea that these two neurochemical systems are present in distinct neuronal populations in the centrifugal visual system. 相似文献
49.
S. Luzzi S. Franchi-Micheli S. Spagnesi Elisabetta Rosi M. Ciuffi Lucilla Zilletti 《Inflammation research》1985,16(3-4):160-162
Inhibitory effect of GABA on anaphylactic histamine releasein vitro is not mimicked by 2-aminoethansulphonic acid (taurine), an aminoacid unrelated to GABA neurotransmission.Tetrodotoxin (TTX) 6×10–7
M, a concentration known to block neuronal mechanism but not to modify muscle membrane and anaphylactic histamine release, strongly prevented the inhibition caused by GABA in the Schultz-Dale reaction and in anaphylactic histamine release.The inhibitory effect of GABA on anaphylactic reactionin vitro thus appears to be specific for this aminoacid and is neurogenic in nature, in that it requires integrity of neuronal mechanisms. 相似文献
50.
Barriers and Facilitators to Participation in Health Screening: an Umbrella Review Across Conditions
Le Bonniec Alice Sun Sophie Andrin Amandine Dima Alexandra L. Letrilliart Laurent 《Prevention science》2022,23(7):1115-1142
Prevention Science - Screening is an essential prevention practice for a number of health conditions. However, screening coverage remains generally low. Studies that investigate determinants of... 相似文献