全文获取类型
收费全文 | 830篇 |
免费 | 83篇 |
出版年
2023年 | 4篇 |
2022年 | 18篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 24篇 |
2015年 | 46篇 |
2014年 | 62篇 |
2013年 | 64篇 |
2012年 | 83篇 |
2011年 | 73篇 |
2010年 | 48篇 |
2009年 | 30篇 |
2008年 | 39篇 |
2007年 | 57篇 |
2006年 | 46篇 |
2005年 | 65篇 |
2004年 | 42篇 |
2003年 | 27篇 |
2002年 | 38篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有913条查询结果,搜索用时 15 毫秒
901.
Luke D Wilson Jacqueline M Sackett Bryce D Mieczkowski Abigail L Richie Kara Thoemke Jon N Rumbley Tim L Kroft 《BMC developmental biology》2011,11(1):10
Background
The C. elegans sperm protein SPE-42, a membrane protein of unknown structure and molecular function, is required for fertilization. Sperm from worms with spe-42 mutations appear normal but are unable to fertilize eggs. Sequence analysis revealed the presence of 8 conserved cysteine residues in the C-terminal cytoplasmic domain of this protein suggesting these residues form a zinc-coordinating RING finger structure. 相似文献902.
Demet Aydogan Kirmizi Emre Baser Asl Okan Mustafa Kara Ethem Serdar Yalvac Zuleyha Doganyigit 《Experimental Animals》2021,70(1):37
Ovarian ischemia is a gynecological emergency case that occurs as a result of ovarian torsion. Oxidative stress plays a central role in the development of ischemia/reperfusion (IR) injuries. Lycopene (LYC) is a lipophilic, natural carotenoid well known for its antioxidant properties. This study provides information on the potential applications of lycopene. The Wistar Albino rats were distributed into six groups: Sham group (only a laparotomy was performed), Control group [laparotomy and intraperitoneal dissolvent (olive oil)], IR group, IR+olive oil group, IR+LYC 2.5 mg/kg/dose, intraperitoneal group, IR+LYC 5 mg/kg/dose intraperitoneal group. Evaluated in terms of histopathological changes, tissue malondialdehyde levels (MDA), ovarian expressions of phosphorylated nuclear factor-kappa B (p-NF-κB) and the TUNEL method was utilized to show apoptosis of ovarian tissue. There was a significant decrease in MDA, p-NF-κB values and the proportion of apoptotic cells assessed by TUNEL compared to the group that did not receive intraperitoneal LYC in rat injury with IR damage (P<0.05). In histopathological damage scoring, it was observed that the cell damage was significantly reduced in LYC-administered groups. LYC showed significant ameliorative effects on ovary injury caused by IR through acting as an antioxidant, antiinflammatory, and antiapoptotic agent. 相似文献
903.
Cell pastes and supernatant Escherichia coli samples, taken from an industrial bioprocess overproducing recombinant alpha 2 IFN were analysed using pyrolysis mass spectrometry (PyMS) and diffuse reflectance-absorbance Fourier transform infrared spectroscopy (FT-IR). PyMS and FT-IR are physico-chemical methods which measure predominantly the bond strengths of molecules and the vibrations of bonds within functional groups, respectively. They therefore give quantitative information about the total biochemical composition of the bioprocess sample. The interpretation of these hyperspectral data, in terms of the quantity of alpha 2 IFN in the cell pastes and supernatant samples was possible only after the application of the 'supervised learning' methods of artificial neural networks (ANNs) and partial least squares (PLS) regression. Both PyMS and FT-IR are novel, rapid and economical methods for the screening and the quantitative analysis of complex biological bioprocess over producing recombinant proteins. Models established using either spectral data set had a similarly satisfactory predictive ability. This shows that whole-reaction mixture spectral methods, which measure all molecules simultaneously, do contain enough information to allow their quantification when the entire spectra are used as the inputs to methods based on supervised learning. Moreover, this is the first study where FT-IR in the mid-IR range has been used to quantify the expression of a heterologous protein directly from fermentation broths and the first study to compare the abilities of PyMS and FT-IR for the quantitative analyses of an industrial bioprocess. 相似文献
904.
Laigle Idaline Moretti Marco Rousseau Laurent Gravel Dominique Venier Lisa Handa I. Tanya Messier Christian Morris Dave Hazlett Paul Fleming Rob Webster Kara Shipley Bill Aubin Isabelle 《Ecosystems》2021,24(7):1716-1737
Ecosystems - Direct and indirect effects of habitat modification and changes in biotic interactions should be taken into consideration to understand the ecological consequences of forest... 相似文献
905.
Stefanie B?hm Barnabas Szakal Benjamin W. Herken Meghan R. Sullivan Michael J. Mihalevic Faiz F. Kabbinavar Dana Branzei Nathan L. Clark Kara A. Bernstein 《The Journal of biological chemistry》2016,291(9):4442-4452
DNA damage must be repaired in an accurate and timely fashion to preserve genome stability. Cellular mechanisms preventing genome instability are crucial to human health because genome instability is considered a hallmark of cancer. Collectively referred to as the DNA damage response, conserved pathways ensure proper DNA damage recognition and repair. The function of numerous DNA damage response components is fine-tuned by posttranslational modifications, including ubiquitination. This not only involves the enzyme cascade responsible for conjugating ubiquitin to substrates but also requires enzymes that mediate directed removal of ubiquitin. Deubiquitinases remove ubiquitin from substrates to prevent degradation or to mediate signaling functions. The Saccharomyces cerevisiae deubiquitinase Ubp7 has been characterized previously as an endocytic factor. However, here we identify Ubp7 as a novel factor affecting S phase progression after hydroxyurea treatment and demonstrate an evolutionary and genetic interaction of Ubp7 with DNA damage repair pathways of homologous recombination and nucleotide excision repair. We find that deletion of UBP7 sensitizes cells to hydroxyurea and cisplatin and demonstrate that factors that stabilize replication forks are critical under these conditions. Furthermore, ubp7Δ cells exhibit an S phase progression defect upon checkpoint activation by hydroxyurea treatment. ubp7Δ mutants are epistatic to factors involved in histone maintenance and modification, and we find that a subset of Ubp7 is chromatin-associated. In summary, our results suggest that Ubp7 contributes to S phase progression by affecting the chromatin state at replication forks, and we propose histone H2B ubiquitination as a potential substrate of Ubp7. 相似文献
906.
Knowledge Integration and Good Marine Governance: A Multidisciplinary Analysis and Critical Synopsis
Poto Margherita Paola Kuhn Annegret Tsiouvalas Apostolos Hodgson Kara K. Treffenfeldt Montoya Valentina M.Beitl Christine 《Human ecology: an interdisciplinary journal》2022,50(1):125-139
Human Ecology - Our research addresses knowledge integration for the good governance of the environment and the oceans: (a) through a comprehensive legal, political science, and anthropological... 相似文献
907.
Meyer Michael F. Hampton Stephanie E. Ozersky Tedy Rusanovskaya Olga O. Woo Kara H. 《Hydrobiologia》2017,796(1):309-318
Hydrobiologia - As lakes warm worldwide, temperature may alter plankton community structure and abundance by affecting not only metabolism but also trophic interactions. Siberia’s Lake Baikal... 相似文献
908.
Kara L. Marlatt Dori R. Pitynski-Miller Kathleen M. Gavin Kerrie L. Moreau Edward L. Melanson Nanette Santoro Wendy M. Kohrt 《Obesity (Silver Spring, Md.)》2022,30(1):14-27
Every year, 2 million women reach menopause in the United States, and they may spend 40% or more of their life in a postmenopausal state. In the years immediately preceding menopause—known as the menopause transition (or perimenopause)—changes in hormones and body composition increase a woman’s overall cardiometabolic risk. In this narrative review, we summarize the changes in weight, body composition, and body fat distribution, as well as the changes in energy intake, energy expenditure, and other cardiometabolic risk factors (lipid profile, glucose metabolism, sleep health, and vascular function), that occur during the menopause transition. We also discuss the benefits of lifestyle interventions in women in the earlier stages of menopause before these detrimental changes occur. Finally, we discuss how to include perimenopausal women in research studies so that women across the life-span are adequately represented. 相似文献
909.
910.
Sophie Dream Sandra Park Tina W. Yen William Rilling Lisa Rein Kara Doffek James W. Findling Steven B. Magill Srividya Kidambi Douglas B. Evans Tracy S. Wang 《Endocrine practice》2022,28(3):276-281
ObjectiveIn patients with primary aldosteronism, adrenal venous sampling (AVS) is performed to determine the presence of unilateral or bilateral adrenal disease. During AVS, verification of catheter positioning within the left adrenal vein (AV) and the right AV by comparison of AV and inferior vena cava (IVC) cortisol levels can be variable. The objective of this study was to determine the utility of AV epinephrine levels in assessing successful AV cannulation.MethodsThis was a single institution, retrospective review of patients who underwent AVS with cosyntropin stimulation for primary aldosteronism between 2009 and 2018. Successful cannulation of the AV was defined by an AV/IVC cortisol ratio selectivity index (SI) ≥3:1. Epinephrine thresholds to predict catheter placement in the AV were determined using logistic regression. The calculated epinephrine thresholds were compared with previously published thresholds.ResultsAVS was performed on 101 consecutive patients and, based on the SI, successful cannulation of the left AV and right AV occurred in 98 (97%) and 91(90%) patients, respectively. The calculated optimal epinephrine threshold to predict AV cannulation was 364 pg/mL (sensitivity, 92.1%; specificity, 94.6%) and the calculated optimal AV/IVC epinephrine ratio threshold was 27.4, (sensitivity, 92.1%; specificity, 91.3%). Among the 14 patients with failed AV cannulation, 3 patients would have been considered to have successful AVS using AV epinephrine levels >364 pg/mL and AV/IVC epinephrine ratio >27.4 thresholds.ConclusionObtaining 2 right AV samples routinely as well as AV and IVC epinephrine levels during AVS could prevent unnecessary repeat AVS in patients with failed AV cannulation based on cortisol-based SI <3:1. 相似文献