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   9776篇
  免费   918篇
  国内免费   1260篇
  11954篇
  2024年   53篇
  2023年   216篇
  2022年   462篇
  2021年   701篇
  2020年   524篇
  2019年   558篇
  2018年   518篇
  2017年   395篇
  2016年   539篇
  2015年   677篇
  2014年   867篇
  2013年   834篇
  2012年   995篇
  2011年   852篇
  2010年   473篇
  2009年   473篇
  2008年   498篇
  2007年   436篇
  2006年   327篇
  2005年   278篇
  2004年   246篇
  2003年   157篇
  2002年   174篇
  2001年   80篇
  2000年   85篇
  1999年   65篇
  1998年   51篇
  1997年   49篇
  1996年   35篇
  1995年   41篇
  1994年   38篇
  1993年   23篇
  1992年   30篇
  1991年   31篇
  1990年   31篇
  1989年   33篇
  1988年   14篇
  1987年   19篇
  1986年   11篇
  1985年   9篇
  1983年   11篇
  1982年   8篇
  1981年   4篇
  1979年   3篇
  1977年   5篇
  1973年   3篇
  1966年   2篇
  1962年   2篇
  1950年   2篇
  1940年   2篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
目的:制备抗干扰素诱导的跨膜蛋白-1(interferon-induced transmembrane protein 1, IFITM1)的单克隆抗体,为检测IFITM1 及进一步研究其在结肠肿瘤发生过程中的作用提供实验基础。方法:以结肠癌患者的癌组织为材料,提取总RNA,以RT-PCR扩 增得到IFITM1 cDNA 序列,经ECoRⅠ和HindⅢ双酶切后,克隆入pGEX-4T-3 进行原核表达并纯化得IFITM1-GST;以该融合蛋 白免疫BALB/c 小鼠,淋巴细胞杂交瘤法制备单克隆抗体;采用ELISA、Western-blot及免疫组织化学法以制备的抗体检测结肠癌 患者结肠癌组织中的IFITM1。结果:成功构建了IFITM1 原核表达载体,获得了IFITM1-GST 重组蛋白;制备得到了1 株抗 IFITM1 单克隆抗体,腹水ELISA 效价为1:30000,抗体亚类为IgG1,可用于ELISA、Western-blot及免疫组织化学法检测结肠癌患 者结肠癌组织中的IFITM1。结论:获得了1 株可用于ELISA、Western-blot及免疫组织化学法的抗IFITM1 单克隆抗体2F-1,为进 一步研究IFITM1在结肠肿瘤发生过程中的作用提供了实验基础。  相似文献   
72.
Solar radiation regulates most biological activities on Earth. Prolonged exposure to solar UV radiation can cause deleterious effects by inducing two major types of DNA damage, namely, cyclobutane pyrimidine dimers (CPDs) and pyrimidine 6-4 pyrimidone photoproducts. These lesions may be repaired by the photoreactivation (Phr) and nucleotide excision repair (NER) pathways; however, the principal UV-induced DNA repair pathway is not known in the fungal genus Pseudogymnoascus. In this study, we demonstrated that an unweighted UV-B dosage of 1.6 kJ m−2 d−1 significantly reduced fungal growth rates (by between 22% and 35%) and inhibited conidia production in a 10 d exposure. The comparison of two DNA repair conditions, light or dark, which respectively induced photoreactivation (Phr) and NER, showed that the UV-B-induced CPDs were repaired significantly more rapidly in light than in dark conditions. The expression levels of two DNA repair genes, RAD2 and PHR1 (encoding a protein in NER and Phr respectively), demonstrated that NER rather than Phr was primarily activated for repairing UV-B-induced DNA damage in these Pseudogymnoascus strains. In contrast, Phr was inhibited after exposure to UV-B radiation, suggesting that PHR1 may have other functional roles. We present the first study to examine the capability of the Arctic and Antarctic Pseudogymnoascus sp. to perform photoreactivation and/or NER via RT-qPCR approaches, and also clarify the effects of light on UV-B-induced DNA damage repair in vivo by quantifying cyclobutene pyrimidine dimers and pyrimidine 6-4 pyrimidone photoproducts. Physiological response data, including relative growth rate, pigmentation and conidia production in these Pseudogymnoascus isolates exposed to UV-B radiation are also presented.  相似文献   
73.
Yangmin Ma  Hao Wu  Jin Zhang  Yanchao Li 《Chirality》2013,25(10):656-662
A series of single isomers tetrahydro‐β‐carboline diketopiperazines were stereoselectively synthesized starting from l ‐tryptophan methyl ester hydrochloride and six aldehydes through a four‐step reaction including Pictet‐Spengler reaction, crystallization‐induced asymmetric transformations (CIAT), Schotten‐Baumann reaction, and intramolecular ester amidation. The chemical structures were characterized by nuclear magnetic resonance (NMR) and elemental analysis, among which two compounds were determined by x‐ray single crystal diffraction. Moreover, antimicrobial activities of all the compounds were also tested. Chirality 25:656–662, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   
74.
Sun W  Xing B  Sun Y  Du X  Lu M  Hao C  Lu Z  Mi W  Wu S  Wei H  Gao X  Zhu Y  Jiang Y  Qian X  He F 《Molecular & cellular proteomics : MCP》2007,6(10):1798-1808
Hepatocellular carcinoma (HCC) is a highly malignant tumor, and chronic infection with hepatitis B virus is one of its major risk factors. To identify the proteins involved in HCC carcinogenesis, we used two-dimensional fluorescence DIGE to study the differentially expressed proteins in tumor and adjacent nontumor tissue samples. Samples from 12 hepatitis B virus-associated HCC patients were analyzed. A total of 61 spots were significantly up-regulated (ratio >/= 2, p 相似文献   
75.
Tandem MS (MS2) quantification using the series of N‐ and C‐terminal fragment ion pairs generated from isobaric‐labelled peptides was recently considered an accurate strategy in quantitative proteomics. However, the presence of multiplexed terminal fragment ion in MS2 spectra may reduce the efficiency of peptide identification, resulting in lower identification scores or even incorrect assignments. To address this issue, we developed a quantitative software tool, denoted isobaric tandem MS quantification (ITMSQ), to improve N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantification. A spectrum splitting module was designed to separate the MS2 spectra from different samples, increasing the accuracy of both identification and quantification. ITMSQ offers a convenient interface through which parameters can be changed along with the labelling method, and the result files and all of the intermediate files can be exported. We performed an analysis of in vivo terminal amino acid labelling labelled HeLa samples and found that the numbers of quantified proteins and peptides increased by 13.64 and 27.52% after spectrum splitting, respectively. In conclusion, ITMSQ provides an accurate and reliable quantitative solutionfor N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantitative methods.  相似文献   
76.
77.
A novel spectrophotometric method to study the kinetics of the guanine nucleotide exchange factors-catalyzed reactions is presented. The method incorporates two coupling enzyme systems: (a). GTPase-activating protein which stimulates the intrinsic GTP hydrolysis reaction of small GTPases and (b). purine nucleotide phosphorylase and its chromophoric substrate, 7-methyl-6-thioguanosine, for quantitation of the resultant inorganic phosphate. The continuous coupled enzyme system was used for characterization of the interactions between the small GTPase RhoA and its guanine nucleotide exchange factors, Lbc and Dbl. Kinetic parameters obtained here show that there is no significant difference in kinetic mechanism of these GEFs in interaction with RhoA. The Michaelis-Menten constants were determined to be around 1micro M, and the rate constants k(cat) were around 0.1s(-1).  相似文献   
78.
Zhang  Hao  Wang  Jin-Yan  Chen  Yi-Juan  Siemann  Evan  Ji  Xiang-Yun  Jiang  Jie-Xian  Wan  Nian-Feng 《BioControl》2022,67(1):1-13
BioControl - The effects of plant volatiles on parasitoids are important with regards to the tri-trophic interactions among host plants, insect herbivores, and their natural enemies. However, the...  相似文献   
79.
Biomechanics and Modeling in Mechanobiology - Subcutaneous injection of therapeutic monoclonal antibodies (mAbs) has gained increasing interest in the pharmaceutical industry. The transport,...  相似文献   
80.
International Journal of Peptide Research and Therapeutics - It is demonstrated that gonadotropin-releasing hormone (GnRH) analogs can directly inhibit the proliferation of reproductive tissue...  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