全文获取类型
收费全文 | 6559篇 |
免费 | 448篇 |
国内免费 | 2篇 |
出版年
2023年 | 21篇 |
2022年 | 74篇 |
2021年 | 163篇 |
2020年 | 77篇 |
2019年 | 100篇 |
2018年 | 143篇 |
2017年 | 127篇 |
2016年 | 210篇 |
2015年 | 297篇 |
2014年 | 334篇 |
2013年 | 434篇 |
2012年 | 537篇 |
2011年 | 606篇 |
2010年 | 330篇 |
2009年 | 284篇 |
2008年 | 378篇 |
2007年 | 447篇 |
2006年 | 377篇 |
2005年 | 350篇 |
2004年 | 315篇 |
2003年 | 324篇 |
2002年 | 315篇 |
2001年 | 64篇 |
2000年 | 40篇 |
1999年 | 45篇 |
1998年 | 49篇 |
1997年 | 44篇 |
1996年 | 32篇 |
1995年 | 32篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1986年 | 12篇 |
1984年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1977年 | 26篇 |
1976年 | 21篇 |
1975年 | 15篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1972年 | 16篇 |
1969年 | 12篇 |
1968年 | 15篇 |
1966年 | 12篇 |
排序方式: 共有7009条查询结果,搜索用时 15 毫秒
961.
962.
963.
Lung cancer is the leading cause of cancer deaths worldwide. If we can define and detect preneoplastic lesions, we might have a chance of improving survival. The World Health Organization has defined three preneoplastic lesions of the bronchial epithelium: squamous dysplasia/carcinoma in situ; atypical adenomatous hyperplasia; and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. These lesions are believed to progress to squamous cell carcinoma, adenocarcinoma and carcinoid tumors, respectively. In this review we summarize the data supporting the preneoplastic nature of these lesions, and delve into some of the genetic changes found in atypical adenomatous hyperplasia and squamous dysplasia/carcinoma in situ. 相似文献
964.
Elisa Beghetto Andrea Pucci Olga Minenkova Andrea Spadoni Luca Bruno Wilma Buffolano Dominique Soldati Franco Felici Nicola Gargano 《International journal for parasitology》2001,31(14)
Excreted secreted antigens of the protozoan parasite Toxoplasma gondii play a key role in stimulating the host immune system during acute and chronic infection. With the aim of identifying the immunodominant epitopes of T. gondii antigens involved in the human B-cell response against the parasite, we employed a novel immunological approach. A library of cDNA fragments from T. gondii tachyzoites was displayed as fusion proteins to the amino-terminus of lambda bacteriophage capsid protein D. The lambdaD-tachyzoite library was then affinity-selected by using a panel of sera of pregnant women, all infected with the parasite. Some of the clones identified through this procedure matched the sequence of the dense granule GRA1 protein (p24), allowing us to identify its antigenic regions. In particular, the analysis of human antibody response against the recombinant GRA1 antigen fragments revealed the existence of an immunodominant epitope (epi-24 peptide). 相似文献
965.
Enhanced Levels of the Aroma and Flavor Compound S-Linalool by Metabolic Engineering of the Terpenoid Pathway in Tomato Fruits 总被引:20,自引:0,他引:20
Efraim Lewinsohn Fernond Schalechet Jack Wilkinson Kenji Matsui Yaakov Tadmor Kyoung-Hee Nam Orit Amar Elena Lastochkin Olga Larkov Uzi Ravid William Hiatt Shimon Gepstein Eran Pichersky 《Plant physiology》2001,127(3):1256-1265
The aromas of fruits, vegetables, and flowers are mixtures of volatile metabolites, often present in parts per billion levels or less. We show here that tomato (Lycopersicon esculentum Mill.) plants transgenic for a heterologous Clarkia breweri S-linalool synthase (LIS) gene, under the control of the tomato late-ripening-specific E8 promoter, synthesize and accumulate S-linalool and 8-hydroxylinalool in ripening fruits. Apart from the difference in volatiles, no other phenotypic alterations were noted, including the levels of other terpenoids such as gamma- and alpha-tocopherols, lycopene, beta-carotene, and lutein. Our studies indicate that it is possible to enhance the levels of monoterpenes in ripening fruits by metabolic engineering. 相似文献
966.
Elena Yu. Blishchenko Olga A. Kalinina Olga V. Sazonova Sergei V. Khaidukov Natalya S. Egorova Andrei Yu. Surovoy Marina M. Philippova Arpad A. Vass Andrei A. Karelin Vadim T. Ivanov 《Peptides》2001,22(12):1999-2008
It is shown that neokyotorphin (the -globin fragment 137–141) stimulates proliferation of normal cells (murine embryonic fibroblasts, red bone marrow and spleen cells) and tumor cells (murine melanoma and transformed fibroblasts L929) in the absence or in the presence of fetal bovine serum. In contrast to serum deprivation conditions, the ability to potentiate L929 cell growth in the presence of fetal serum is strongly cell density dependent. The peptide also enhances the viability of L929 cells, murine embryonic fibroblasts and of the primary cultures of murine red bone marrow cells and splenocytes under serum-deprivation conditions for at least 72 h. The results of flow cytometry analysis suggest that the effect of neokyotorphin on survival of L929 cells in serum-free culture medium is due to maintenance of cell proliferation in the absence of growth factors. Along with cell cycle progression the peptide induces reversible reduction of L929 cell size. 相似文献
967.
According to DNA hybridization data, thermophilic streptococci used in Russia as starters in the dairy industry are divided into six different genomovars, with a degree of DNA homology not exceeding 20–50%. The analysis of genomes from these genomovars using SmaI restriction endonuclease and pulsed-field gel electrophoresis revealed wide variability of the genome size. In some strains, the genome size considerably exceeded 2000 kbp. Most of the strains studied contained plasmids about 120 kbp in size. 相似文献
968.
969.
Olga G?ransson Svante Resj? Lars R?nnstrand Vincent Manganiello Eva Degerman 《Cellular signalling》2002,14(2):175-182
The mechanism of activation for protein kinase B (PKB), an important target for insulin signaling, has been scarcely investigated in primary cells. In this study, we have characterized the insulin-induced phosphorylation and activation of PKB beta in primary rat adipocytes. Insulin stimulation resulted in a translocation of PKB beta from cytosol to membranes, and phosphorylation and activation of PKB beta. Phosphoamino acid analysis and phosphopeptide mapping demonstrated that the phosphorylation occurred mainly on serines, also when using calyculin A, and that these were localized within one major phosphopeptide. Radiosequencing showed that the radioactivity was released in Cycle No. 7. In addition, the peptide was specifically immunoprecipitated from a tryptic digest of PKB beta using the anti-phospho-PKB (Ser-473) antibody. Taken together, these results show that rat adipocyte PKB beta mainly is phosphorylated on Ser-474 in response to insulin stimulation, in contrast to previous studies in human embryonic kidney (HEK) 293 cells demonstrating, in addition, phosphorylation of Thr-309. 相似文献
970.
Olga Malsam Michael Kilian Erich-Christian Oerke Heinz-Wilhelm Dehne 《Biocontrol Science and Technology》2002,12(3):337-348
The efficacy of Metarhizium anisopliae in combination with sublethal concentrations of oils and potassium-oleate for biological control of whiteflies was tested under controlled conditions. Three commercial products (Biola ® , Naturen ® , Neudosan ® ) and five experimental formulations of plant oils were tested. The efficacy of M. anisopliae against Trialeurodes vaporariorum and Bemisia tabaci without additives was about 50%. At 1/20 of their recommended dosages, all compounds tested significantly increased the efficacy of M. anisopliae for the control of T. vaporariorum , with the formulated sunflower oil Biola ® giving the highest synergistic effect, reaching nearly 100% control. Not only was the level of control increased but also the speed of action was improved, resulting in a higher reliability of control. Three of seven additives showed no effects on the viability of conidia on the leaf surface, whereas the formulations of the other oils and oleates reduced the longevity of spores. The synergistic effect of Biola resulted from the more even distribution of M. anisopliae conidia on leaves and insects. Other positive effects of oils on the efficacy of M. anisopliae are discussed in relation to an extended spectrum of environmental conditions and pests to be controlled. 相似文献