全文获取类型
收费全文 | 24287篇 |
免费 | 2011篇 |
国内免费 | 926篇 |
专业分类
27224篇 |
出版年
2023年 | 269篇 |
2022年 | 555篇 |
2021年 | 939篇 |
2020年 | 620篇 |
2019年 | 698篇 |
2018年 | 807篇 |
2017年 | 649篇 |
2016年 | 843篇 |
2015年 | 1302篇 |
2014年 | 1327篇 |
2013年 | 1605篇 |
2012年 | 1928篇 |
2011年 | 1771篇 |
2010年 | 1040篇 |
2009年 | 958篇 |
2008年 | 1290篇 |
2007年 | 1112篇 |
2006年 | 968篇 |
2005年 | 868篇 |
2004年 | 801篇 |
2003年 | 722篇 |
2002年 | 621篇 |
2001年 | 580篇 |
2000年 | 494篇 |
1999年 | 474篇 |
1998年 | 247篇 |
1997年 | 190篇 |
1996年 | 197篇 |
1995年 | 216篇 |
1994年 | 184篇 |
1993年 | 155篇 |
1992年 | 232篇 |
1991年 | 272篇 |
1990年 | 200篇 |
1989年 | 206篇 |
1988年 | 173篇 |
1987年 | 154篇 |
1986年 | 137篇 |
1985年 | 156篇 |
1984年 | 129篇 |
1983年 | 112篇 |
1982年 | 70篇 |
1981年 | 68篇 |
1980年 | 67篇 |
1979年 | 75篇 |
1978年 | 77篇 |
1977年 | 64篇 |
1975年 | 57篇 |
1974年 | 51篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Two strains of Agrobacterium rhizogenes (15834, LBA 9402) and one Agrobacterium tumefaciens strain [GV 3101 (PMP90RK, p35SGUS-2)] and four culture media were tested and compared for their ability to induce hairy root formation on wounded Papaver somniferum L. hypocotyls. Five weeks after the infection with A. rhizogenes LBA 9402, hairy roots appeared on 80% of the hypocotyls maintained in the hormone-free liquid medium. Six hairy-root cultures were established. Transformation was confirmed by polymerase chain reaction analysis. One clone was analysed for its alkaloid production. The total alkaloid content was higher in the transformed roots (0.46±0.06% DW) than in the untransformed roots (0.32±0.05% DW). The transformed roots accumulated three times more codeine (0.18±0.02% DW) than intact roots (0.05±0% DW). Moreover, morphine (0.255±0.03% DW) and sanguinarine (0.014±0% DW) were found in the liquid culture medium.Abbreviations
2,4-D
2,4-Dichlorophenoxyacetic acid
-
LS
Linsmaier and Skoog 相似文献
992.
Le Diguarher T Ortuno JC Shanks D Guilbaud N Pierré A Raimbaud E Fauchère JL Hickman JA Tucker GC Casara PJ 《Bioorganic & medicinal chemistry letters》2004,14(3):767-771
A structure-activity study was performed by synthesis on N,N'-disubstitution of 3-aminobenzo[c] and [d]azepin-2-one 2 and 3 to afford potent and specific farnesyl transferase inhibitors with low nM enzymatic and cellular activities. 相似文献
993.
The internalization of various cargo proteins and lipids from the mammalian cell surface occurs through the clathrin and lipid-raft endocytic pathways. Protein-lipid and protein-protein interactions control the targeting of signalling molecules and their partners to various specialized membrane compartments in these pathways. This functions to control the activity of signalling cascades and the termination of signalling events, and therefore has a key role in defining how a cell responds to its environment. 相似文献
994.
Darwin J. Prockop Malcolm Brenner Willem E. Fibbe Edwin Horwitz Katarina Le Blanc Donald G. Phinney Paul J. Simmons Luc Sensebe Armand Keating 《Cytotherapy》2010,12(5):576-578
We address the issue of the potential for malignant transformation of cultured mesenchymal stromal cells (MSC) commonly used in clinical cell-therapy protocols and describe the culture conditions under which tumorigenesis is likely to be an extremely uncommon event. 相似文献
995.
The objective of this investigation was to explore possible molecular changes for role of a high-fat diet (HFD)-induced oxidative stress in splenic lymphocytes, and whether a dietary lipoic acid (LA) supplement could attenuate these changes. Male C57BL/6 mice were fed one of three diets 10 weeks and outcome measures centered on parameters of oxidative stress and lymphocytes apoptosis in spleen. Two-dimensional gel electrophoresis was used to compare the proteomes of splenic lymphocytes with three dietary groups. Differentially expressed spots whose expression altered over three fold were identified by MALDI-TOF MS. In this study, HFD resulted in oxidative stress in mice spleen, and significantly increased apoptotic percentage of splenic lymphocytes. Bioinformatic evaluation results of MALDI-TOF MS showed that 20 differentially expressed protein spots were known to be involved in many processes associated with cell function, such as cytoskeleton, energy metabolism and oxidative stress, signal transduction and cell defense. In conclusion, these results indicate that HFD-induced oxidative stress could lead to the functional decline of splenic lymphocytes, and LA supplement attenuates the alterations of protein expression to maintain the basic biological processes. 相似文献
996.
Background: Numerous studies have investigated the risk of cancer associated with the polymorphism of epidermal growth factor (EGF) 61A>G, but the results have been inconsistent. We performed this meta-analysis to drive a more precise estimation of association between this polymorphism and risk of cancer. Methods: Electronic searches of PubMed and EMBASE were conducted to select studies. Case-control studies containing available genotype frequencies of EGF 61A>G were chose, and Odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association. Results: 23 case-control studies including 5578 cases and 7306 controls were identified. This meta-analysis showed significant effect of EGF 61A>G on cancer risk (GG vs. AA: OR = 1.34, 95%CI = 1.05–1.72; GG vs. GA + AA: OR = 1.23, 95%CI = 1.03–1.47; GG + GA vs. AA: OR = 1.18, 95%CI = 1.02–1.38). In subgroup analysis, significant increased risk was found in gastric cancer and glioma in additive model (OR = 1.54, 95%CI = 1.13–2.12; OR = 1.69, 95%CI = 1.21–2.37) and in recessive model (OR = 1.29, 95%CI = 1.10–1.52; OR = 1.54, 95%CI = 1.16–2.04). Conclusion: This meta-analysis suggested that the EGF 61G allele is a risk factor of cancer, especially for gastric cancer and glioma. 相似文献
997.
研究了盲蝽科齿爪盲蝽亚科Deraeocorinae点盾盲蝽属AlloeotomusFieber中国种类 ;共记载 5个种 ,其中包括 2新种 (突肩点盾盲蝽A .humeralissp.nov.,云南点盾盲蝽A .yunnanensissp .nov.)和 1个新异名 (A .kerzhneriQi&Nonnaizab =A .montanusQi&Nonnaizab,syn.nov .)。新种模式标本均存于天津南开大学生物系昆虫标本室 相似文献
998.
999.
Tran Tinh Hien Nguyen Thi Dung Nguyen Thanh Truong Ninh Thi Thanh Van Tran Nguyen Bich Chau Nguyen Van Minh Hoang Tran Thi Thu Nga Cao Thu Thuy Pham Van Minh Nguyen Thi Cam Binh Tran Thi Diem Ha Pham Van Toi To Song Diep James I. Campbell Elaine Stockwell Constance Schultsz Cameron P. Simmons Clare Glover Winnie Lam Filipe Marques James P. May Anthony Upton Ronald Budhram Gordon Dougan Jeremy Farrar Nguyen Van Vinh Chau Christiane Dolecek 《PloS one》2010,5(7)
Background
The emergence of drug resistant typhoid fever is a major public health problem, especially in Asia. An oral single dose typhoid vaccine would have major advantages. M01ZH09 is a live oral single dose candidate typhoid vaccine containing Salmonella enterica serovar Typhi (Ty2 aroC − ssaV −) ZH9 with two independently attenuating deletions. Studies in healthy adults demonstrated immunogenicity and an acceptable safety profile.Objectives
We conducted a randomised placebo controlled, single-blind trial to evaluate the safety and immunogenicity of M01ZH09 in healthy Vietnamese children aged 5 to 14 years.Methods
Subjects were randomly assigned to receive either a nominal dose of 5×109 CFU of M01ZH09 or placebo and were followed up for 28 days. The primary safety outcome was the proportion of subjects with any adverse event attributed to M01ZH09. The primary immunogenicity endpoint was the proportion of subjects who showed a positive immune response to M01ZH09 in the Salmonella Typhi lipopolysaccharide (LPS) specific serum IgA and IgG ELISA.Principal Findings
One hundred and fifty-one children were enrolled, 101 subjects received M01ZH09 and 50 subjects received placebo. An intention to treat analysis was conducted. There were no serious adverse events and no bacteraemias. In the M01ZH09 group, 26 (26%; 95% CI, 18–5%) of 101 subjects experienced adverse events compared to 11 (22%; 95% CI, 12–36%) of 50 subjects in the placebo group (odds ratio (OR) [95%CI] = 1.23 [0.550–2.747]; p = 0.691). Faecal shedding of S. Typhi (Ty2 aroC − ssaV −) ZH9 was detected in 51 (51%; 95% CI, 41–61%) of 100 M01ZH09 subjects. No shedding was detected beyond day 3. A positive immune response, defined as 70% increase (1.7 fold change) in LPS specific serum IgG (day 14 or 28) and/or 50% increase (1.5 fold change) in LPS specific serum IgA (day 7 or 14) from baseline was detected in 98 (97%; 95% CI, 92–99%) of 101 M01ZH09 recipients and 8 (16%; 95% CI, 7–29%) of 50 placebo recipients. Twenty-eight (100%; 95% CI, 88–100%) of 28 vaccine recipients who were evaluated in the LPS specific IgA ELISPOT assay showed a positive response compared to none of the 14 placebo recipients tested.Conclusions
This was the first phase II trial of a novel oral candidate typhoid vaccine in children in an endemic country. M01ZH09 had an appropriate safety profile and was immunogenic in children.Trial Registration
Controlled-trials.comISRCTN91111837 相似文献1000.
Yves‐Marie Coïc Charlotte Le Lan Jean‐Michel Neumann Nadège Jamin Françoise Baleux 《Journal of peptide science》2010,16(2):98-104
This work contributes to highlight the benefits of pseudoproline dipeptides introduction in difficult SPPS. We show how a slight modification in the positioning choice conditioned the synthesis achievement of a 54 amino acid long caveolin‐1 peptide encompassing the intramembrane domain. Furthermore, we report a side reaction correlated with the coupling steps and generating truncated fragments with a mass deviation of + 42 Da. Considering the need of structural data for membrane proteins, most of which are considered as prevalent therapeutic targets, chemical synthesis provides an interesting alternative pathway to obtain hydrophobic domains by pushing back the frontiers of conventional RP methods of purification. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. 相似文献