全文获取类型
收费全文 | 79604篇 |
免费 | 5818篇 |
国内免费 | 256篇 |
专业分类
耳鼻咽喉 | 911篇 |
儿科学 | 2050篇 |
妇产科学 | 1084篇 |
基础医学 | 10758篇 |
口腔科学 | 843篇 |
临床医学 | 8452篇 |
内科学 | 17055篇 |
皮肤病学 | 884篇 |
神经病学 | 7748篇 |
特种医学 | 3065篇 |
外科学 | 12828篇 |
综合类 | 890篇 |
一般理论 | 91篇 |
预防医学 | 5966篇 |
眼科学 | 1964篇 |
药学 | 5366篇 |
中国医学 | 94篇 |
肿瘤学 | 5629篇 |
出版年
2024年 | 56篇 |
2023年 | 667篇 |
2022年 | 1039篇 |
2021年 | 2414篇 |
2020年 | 1360篇 |
2019年 | 2209篇 |
2018年 | 2529篇 |
2017年 | 1803篇 |
2016年 | 1898篇 |
2015年 | 2215篇 |
2014年 | 3209篇 |
2013年 | 4064篇 |
2012年 | 6519篇 |
2011年 | 6758篇 |
2010年 | 3693篇 |
2009年 | 3238篇 |
2008年 | 5393篇 |
2007年 | 5598篇 |
2006年 | 5185篇 |
2005年 | 5138篇 |
2004年 | 4636篇 |
2003年 | 4248篇 |
2002年 | 3853篇 |
2001年 | 597篇 |
2000年 | 396篇 |
1999年 | 565篇 |
1998年 | 786篇 |
1997年 | 588篇 |
1996年 | 477篇 |
1995年 | 425篇 |
1994年 | 399篇 |
1993年 | 395篇 |
1992年 | 250篇 |
1991年 | 197篇 |
1990年 | 179篇 |
1989年 | 162篇 |
1988年 | 156篇 |
1987年 | 129篇 |
1986年 | 132篇 |
1985年 | 145篇 |
1984年 | 182篇 |
1983年 | 150篇 |
1982年 | 236篇 |
1981年 | 232篇 |
1980年 | 164篇 |
1979年 | 95篇 |
1978年 | 114篇 |
1977年 | 99篇 |
1976年 | 69篇 |
1975年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
Greg Reynolds Martin Wilson Andrew Peet Theodoros N Arvanitis 《Magnetic resonance in medicine》2006,56(6):1211-1219
The quantitation of metabolite concentrations from in vitro NMR spectra is hampered by the sensitivity of peak positions to experimental conditions. The quantitation methods currently available are generally labor intensive and cannot readily be automated. Here, an algorithm is presented for the automatic time domain analysis of high-resolution NMR spectra. The TARQUIN algorithm uses a set of basis functions obtained by quantum mechanical simulation using predetermined parameters. Each basis function is optimized by subdividing it into a set of signals from magnetically equivalent spins and varying the simulated chemical shifts of each of these groups to match the signal undergoing analysis. A novel approach to the standard multidimensional minimization problem is introduced based on evaluating the fit resulting from different permutations of possible chemical shifts, obtained from one-dimensional searches. Results are presented from the analysis of (1)H proton magic angle spinning spectra of cell lines illustrating the robustness of the method in a typical application. Simulation was used to investigate the biggest peak shifts that can be tolerated. 相似文献
162.
163.
Tumor targeting by an aptamer. 总被引:10,自引:0,他引:10
Brian J Hicke Andrew W Stephens Ty Gould Ying-Fon Chang Cynthia K Lynott James Heil Sandra Borkowski Christoph-Stephan Hilger Gary Cook Stephen Warren Paul G Schmidt 《Journal of nuclear medicine》2006,47(4):668-678
Aptamers are small oligonucleotides that are selected to bind tightly and specifically to a target molecule. We sought to determine whether aptamers have potential for in vivo delivery of radioisotopes or cytotoxic agents. METHODS: TTA1, an aptamer to the extracellular matrix protein tenascin-C, was prepared in fluorescent and radiolabeled forms. After in vivo administration, uptake and tumor distribution of Rhodamine Red-X-labeled aptamer was studied by fluorescence microscopy. In glioblastoma (U251) and breast cancer (MDA-MB-435) tumor xenografts, biodistribution and imaging studies were performed using TTA1 radiolabeled with (99m)Tc. Tenascin-C levels and tumor uptake were studied in a variety of additional human tumor xenografts. To assess the effect of radiometal chelate on biodistribution, mercapto-acetyl diglycine (MAG(2)) was compared with diethylenetriaminepentaacetic acid and with MAG(2)-3,400-molecular-weight PEG (PEG(3,400)). RESULTS: Intravenous injection of fluorescent aptamer TTA1 produced bright perivascular fluorescence in a xenografted human tumor within 10 min. In the ensuing 3 h, fluorescence diffused throughout the tumor. Labeled with (99m)Tc, TTA1 displayed rapid blood clearance, a half-life of less than 2 min, and rapid tumor penetration: 6% injected dose (%ID)/g at 10 min. Tumor retention was durable, with 2.7 %ID/g at 60 min and a long-lived phase that stabilized at 1 %ID/g. Rapid tumor uptake and blood clearance yielded a tumor-to-blood ratio of 50 within 3 h. Both renal and hepatic clearance pathways were observed. Using the (99m)Tc-labeled aptamer, images of glioblastoma and breast tumors were obtained by planar scintigraphy. Aptamer uptake, seen in several different human tumors, required the presence of the target protein, human tenascin-C. Modification of the MAG(2) radiometal chelator dramatically altered the uptake and clearance patterns. CONCLUSION: TTA1 is taken up by a variety of solid tumors including breast, glioblastoma, lung, and colon. Rapid uptake by tumors and rapid clearance from the blood and other nontarget tissues enables clear tumor imaging. As synthetic molecules, aptamers are readily modified in a site-specific manner. A variety of aptamer conjugates accumulate in tumors, suggesting imaging and potentially therapeutic applications. 相似文献
164.
The effect of monoclonal antibodies to calcitonin gene-related peptide (CGRP) on CGRP-induced vasodilatation in pig coronary artery rings. 下载免费PDF全文
N. E. Shaw R. Foulkes D. P. Andrew D. T. Brown B. Hughes 《British journal of pharmacology》1992,106(1):196-198
1. The modification of the vasodilator effect of calcitonin gene-related peptide (CGRP) by a panel of monoclonal antibodies (MAbs), which map to discrete epitopes on the CGRP molecule, was investigated in pig coronary artery rings (PCA). The preparations were pre-constricted with acetylcholine (3 x 10(-7) M) and concentration-response curves to CGRP (2 x 10(-10)-2.56 x 10(-8) M) were obtained in the presence or absence of each MAb. 2. CGRP caused a concentration-dependent relaxation of PCAs which reached a maximum (98.2 +/- 4.8%, n = 25) at 1.28 x 10(-8) M and gave an EC50 of 3.8 +/- 0.8 x 10(-9) M. 3. Two MAbs which map to the N-terminal, CN1 and CRA3, did not affect the CGRP response whilst a third, CRA5, significantly inhibited its effect. 4. The C-terminal MAb, CRA2, did not modify the CGRP response whilst, in contrast, CB3 (C-terminal) potentiated its effect. A similar augmentation of the CGRP-induced vasodilatation was seen in the presence of the middle-region MAb, CRA8. 5. These results suggest that regional specific MAbs can modify the vasodilator effect of CGRP causing either inhibition (CRA5, N-terminal) or potentiation (CB3, C-terminal; CRA8, middle region). 相似文献
165.
Karoly Szepeshazi Slobodan Milovanovic Karoly Lapis Kate Groot Andrew V. Schally 《Breast cancer research and treatment》1992,21(3):181-192
Summary Female BDF1 mice inoculated with MXT (3.2) estrogen independent mouse mammary carcinoma were treated for three weeks with microcapsules of the luteinizing hormone-releasing hormone (LH-RH) agonist [D-Trp6]LH-RH, the antagonist SB-75, the somatostatin analog RC-160, or combinations. The lack of estrogen dependence of the tumor was proved by bilateral surgical ovariectomy, which had no effect. In two experiments, treatment with 25µg/day doses of each analog alone resulted in a significant inhibition of tumor growth as shown by a 40–53% inhibition of tumor volumes, 38–43% decrease in tumor weights, and histological signs of tumor regression. However, the combination of SB-75 or [D-Trp6]LH-RH with somatostatin analog RC-160 caused greater reduction of tumor volume (68 and 61%) or tumor weights (59 and 56%), than single analogs, and histologically the occurrence of apoptosis and decrease in AgNOR numbers was more pronounced in the groups receiving combination therapy. Specific binding sites for [D-Trp6]LH-RH, EGF, and IGF-I were demonstrated in the tumor membranes. The binding capacity of LH-RH receptors was decreased by treatment with the analogs, the greatest down-regulation being caused by combination therapy. A significant decrease in EGF binding capacity was observed after treatment with the LH-RH analogs, alone or especially in combination with somatostatin analog RC-160. The combination of these analogs also caused a reduction in IGF-I receptors. The finding that LH-RH agonists and antagonists and somatostatin analogs inhibit the growth of estrogen independent mammary tumors, and that combinations are more effective than single analogs, might be of practical importance in human breast cancer therapy. 相似文献
166.
167.
168.
169.
170.