全文获取类型
收费全文 | 34492篇 |
免费 | 2605篇 |
国内免费 | 8篇 |
专业分类
37105篇 |
出版年
2023年 | 200篇 |
2022年 | 155篇 |
2021年 | 320篇 |
2020年 | 363篇 |
2019年 | 341篇 |
2018年 | 794篇 |
2017年 | 704篇 |
2016年 | 1165篇 |
2015年 | 1761篇 |
2014年 | 1710篇 |
2013年 | 2301篇 |
2012年 | 3140篇 |
2011年 | 2918篇 |
2010年 | 1573篇 |
2009年 | 1220篇 |
2008年 | 2303篇 |
2007年 | 2195篇 |
2006年 | 2162篇 |
2005年 | 1895篇 |
2004年 | 1871篇 |
2003年 | 1734篇 |
2002年 | 1611篇 |
2001年 | 668篇 |
2000年 | 773篇 |
1999年 | 424篇 |
1998年 | 242篇 |
1997年 | 132篇 |
1996年 | 161篇 |
1995年 | 175篇 |
1994年 | 146篇 |
1993年 | 138篇 |
1992年 | 148篇 |
1991年 | 119篇 |
1990年 | 112篇 |
1989年 | 104篇 |
1988年 | 77篇 |
1987年 | 60篇 |
1986年 | 62篇 |
1985年 | 86篇 |
1984年 | 110篇 |
1983年 | 63篇 |
1982年 | 82篇 |
1981年 | 54篇 |
1980年 | 60篇 |
1979年 | 55篇 |
1978年 | 46篇 |
1977年 | 43篇 |
1976年 | 64篇 |
1975年 | 48篇 |
1974年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
André Soares Luís Vasco Louro Marta Almeida Olga Sousa 《Reports of Practical Oncology and Radiotherapy》2012,17(6):384-388
Thymomas are rare neoplasms that have an indolent growth with a preferentially intra-thoracic dissemination pattern. Surgery is currently the standard treatment of thymomas; however radiotherapy is often used in an adjuvant setting due to a high sensitivity of these tumors to such treatment. Postoperative entire hemithoracic irradiation has been used in selected Masaoka stage IVa cases after complete surgical excision of metastatic lesions.In the present article, the authors report three cases of Masaoka stage IVa thymoma that underwent entire hemithorax irradiation after surgical excision of metastatic lesions. The first two patients presented as stage IVa thymomas. The third case consisted of a pleural recurrence of a thymoma.Hemithoracic irradiation with low doses has been used by different authors; the available data shows that it is a well-tolerated treatment that could potentially lead to better loco-regional control and increased overall survival. 相似文献
104.
ágnes Lendvai Frank Johannes Christina Grimm Jasper J.H. Eijsink René Wardenaar Haukeline H. Volders Harry G. Klip Harry Hollema Ritsert C. Jansen Ed Schuuring G. Bea A. Wisman Ate G.J. van der Zee 《Epigenetics》2012,7(11):1268-1278
Epigenetic modifications, such as aberrant DNA promoter methylation, are frequently observed in cervical cancer. Identification of hypermethylated regions allowing discrimination between normal cervical epithelium and high-grade cervical intraepithelial neoplasia (CIN2/3), or worse, may improve current cervical cancer population-based screening programs. In this study, the DNA methylome of high-grade CIN lesions was studied using genome-wide DNA methylation screening to identify potential biomarkers for early diagnosis of cervical neoplasia. Methylated DNA Immunoprecipitation (MeDIP) combined with DNA microarray was used to compare DNA methylation profiles of epithelial cells derived from high-grade CIN lesions with normal cervical epithelium. Hypermethylated differentially methylated regions (DMRs) were identified. Validation of nine selected DMRs using BSP and MSP in cervical tissue revealed methylation in 63.2–94.7% high-grade CIN and in 59.3–100% cervical carcinomas. QMSP for the two most significant high-grade CIN-specific methylation markers was conducted exploring test performance in a large series of cervical scrapings. Frequency and relative level of methylation were significantly different between normal and cancer samples. Clinical validation of both markers in cervical scrapings from patients with an abnormal cervical smear confirmed that frequency and relative level of methylation were related with increasing severity of the underlying CIN lesion and that ROC analysis was discriminative. These markers represent the COL25A1 and KATNAL2 and their observed increased methylation upon progression could intimate the regulatory role in carcinogenesis. In conclusion, our newly identified hypermethylated DMRs represent specific DNA methylation patterns in high-grade CIN lesions and are candidate biomarkers for early detection. 相似文献
105.
Thomas Ratschiller Marcus-André Deutsch Julia Calzada-Wack Frauke Neff Christiane Roesch Ralf Guenzinger Ruediger Lange Markus Krane 《Journal of visualized experiments : JoVE》2015,(102)
The heterotopic cervical heart transplantation in mice is a valuable tool in transplant and cardiovascular research. The cuff technique greatly simplifies this model by avoiding challenging suture anastomoses of small vessels thereby reducing warm ischemia time. In comparison to abdominal graft implantation the cervical model is less invasive and the implanted graft is easily accessible for further follow-up examinations. Anastomoses are performed by pulling the ascending aorta of the graft over the cuff with the recipient’s common carotid artery and by pulling the main pulmonary artery over the cuff with the external jugular vein. Selection of appropriate cuff size and complete mobilization of the vessels are important for successful revascularization. Ischemia-reperfusion (I/R) injury can be minimized by perfusing the graft with a cardioplegic solution and by hypothermia. In this article, we provide technical details for a simplified and improved cuff technique, which should allow surgeons with basic microsurgical skills to perform the procedure with a high success rate. 相似文献
106.
Mugnaini C Manetti F Esté JA Clotet-Codina I Maga G Cancio R Botta M Corelli F 《Bioorganic & medicinal chemistry letters》2006,16(13):3541-3544
S-Aryl-S-DABO derivatives, a novel subclass of S-DABO anti-HIV-1 agents, were synthesized via Ullmann type reaction starting from the corresponding 2-thiouracils by the aid of microwave irradiation. The results of their evaluation as inhibitors of RT are reported together with their antiviral activity in cellular assays. 相似文献
107.
Christophe Morell André Grand Alejandro Toro-Labbé Henry Chermette 《Journal of molecular modeling》2013,19(7):2893-2900
In this work, the third derivative of the energy with respect to the number of electrons, the so-called hyper-hardness, is investigated to assess whether this quantity has a chemical meaning. To achieve this goal a new working expression for hyper-hardness is developed and analyzed. It transpired from this analysis that hyper-hardness, just like hardness, can measure the reactivity or the stability of electron systems. Interestingly, positive values of hyper-hardness point to quite stable species such as noble gases and molecules. On the other hand, radicals almost always display large negative values of hyper-hardness. 相似文献
108.
Priscila da Silva Delabona Deise Juliana Lima Diogo Robl Sarita Cândida Rabelo Cristiane Sanchez Farinas José Geraldo da Cruz Pradella 《Journal of industrial microbiology & biotechnology》2016,43(5):617-626
The use of glycerol obtained as an intermediate of the biodiesel manufacturing process as carbon source for microbial growth is a potential alternative strategy for the production of enzymes and other high-value bioproducts. This work evaluates the production of cellulase enzymes using glycerol for high cell density growth of Trichoderma harzianum followed by induction with a cellulosic material. Firstly, the influence of the carbon source used in the pre-culture step was investigated in terms of total protein secretion and fungal morphology. Enzymatic productivity was then determined for cultivation strategies using different types and concentrations of carbon source, as well as different feeding procedures (batch and fed-batch). The best strategy for cellulase production was then further studied on a larger scale using a stirred tank bioreactor. The proposed strategy for cellulase production, using glycerol to achieve high cell density growth followed by induction with pretreated sugarcane bagasse, achieved enzymatic activities up to 2.27 ± 0.37 FPU/mL, 106.40 ± 8.87 IU/mL, and 9.04 ± 0.39 IU/mL of cellulase, xylanase, and β-glucosidase, respectively. These values were 2 times higher when compared to the control experiments using glucose instead of glycerol. This novel strategy proved to be a promising approach for improving cellulolytic enzymes production, and could potentially contribute to adding value to biomass within the biofuels sector. 相似文献
109.
110.
Here we describe the visualization by confocal microscopy of ingested gold (15nm)-labeled transferrin in epimastigote forms of the protozoan Trypanosoma cruzi. Intracellular gold labeling was evident at two sites, which represent the bottom of the cytopharynx and the reservosomes. The gold tracer was best observed by confocal microscopy by using the 633nm excitation wavelength. Intracellular gold clusters larger than 60nm could be visualized by either gold reflection (light scattering) or photoluminescence modes. The gold reflection mode, the gold photoluminescence mode and the anti-transferrin immunofluorescence image of gold-labeled transferrin showed co-localization, thus demonstrating that the gold visualization modes did not represent artifacts or mislocalization of the biomarker. Visualization of protein-gold nanoparticle complexes by confocal microscopy thus emerges as a promising imaging tool to explore the endocytic pathway in trypanosomes and other cell types, as well as to perform immunolocalization studies using gold-labeled secondary antibodies. 相似文献