全文获取类型
收费全文 | 2068篇 |
免费 | 160篇 |
国内免费 | 1篇 |
专业分类
2229篇 |
出版年
2023年 | 19篇 |
2022年 | 26篇 |
2021年 | 63篇 |
2020年 | 32篇 |
2019年 | 38篇 |
2018年 | 54篇 |
2017年 | 49篇 |
2016年 | 73篇 |
2015年 | 126篇 |
2014年 | 127篇 |
2013年 | 165篇 |
2012年 | 168篇 |
2011年 | 161篇 |
2010年 | 102篇 |
2009年 | 80篇 |
2008年 | 113篇 |
2007年 | 138篇 |
2006年 | 127篇 |
2005年 | 80篇 |
2004年 | 94篇 |
2003年 | 73篇 |
2002年 | 70篇 |
2001年 | 30篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有2229条查询结果,搜索用时 28 毫秒
991.
Usefulness of multimodal MR imaging in the differential diagnosis of HaNDL and acute ischemic stroke
Tomas Segura Francisco Hernandez-Fernandez Pedro Sanchez-Ayaso Elena Lozano Lorenzo Abad 《BMC neurology》2010,10(1):120
Background
Syndrome of transient Headache and Neurological Deficits with cerebrospinal fluid Lymphocitosis (HaNDL) is a rare disease which can present with focal neurological deficits and mimic stroke. A neurologist-on-duty faced with a HaNDL patient in the first hours might erroneously decide to use thrombolytic drugs, a non-innocuous treatment which has no therapeutic effect on this syndrome. 相似文献992.
993.
Vinícius Silva Junqueira Leonardo de Azevedo Peixoto Bruno Galvêas Laviola Leonardo Lopes Bhering Simone Mendon?a Tania da Silveira Agostini Costa Rosemar Antoniassi 《PloS one》2016,11(6)
The biggest challenge for jatropha breeding is to identify superior genotypes that present high seed yield and seed oil content with reduced toxicity levels. Therefore, the objective of this study was to estimate genetic parameters for three important traits (weight of 100 seed, oil seed content, and phorbol ester concentration), and to select superior genotypes to be used as progenitors in jatropha breeding. Additionally, the genotypic values and the genetic parameters estimated under the Bayesian multi-trait approach were used to evaluate different selection indices scenarios of 179 half-sib families. Three different scenarios and economic weights were considered. It was possible to simultaneously reduce toxicity and increase seed oil content and weight of 100 seed by using index selection based on genotypic value estimated by the Bayesian multi-trait approach. Indeed, we identified two families that present these characteristics by evaluating genetic diversity using the Ward clustering method, which suggested nine homogenous clusters. Future researches must integrate the Bayesian multi-trait methods with realized relationship matrix, aiming to build accurate selection indices models. 相似文献
994.
995.
Breast cancer is the most frequent cause of cancer in women. In the current study, transition metal ruthenium was complexed with flavonoid chrysin to evaluate the chemotherapeutic potential of this compound in Michigan Cancer Foundation-7 (MCF-7) human mammary cancer cell line and 7,12-dimethylbenz(α)anthracene-induced mammary cancer in female Sprague–Dawley rats. The characterizations of the complex were accomplished through UV–visible, NMR, IR, Mass spectra, and XRD techniques and antioxidant activity was assessed by DPPH, FRAP, and ABTS methods. In vitro studies included cell viability, cell cycle analysis, DNA fragmentation, and marker analysis by western blot analysis and found that complex treatment suppressed cell growth-induced cell cycle arrest and enhanced the induction of apoptosis in cancer cells. Moreover, complex treatment modulated signaling pathways including mTOR, VEGF, and p53 in the MCF-7 cells. Acute and subacute toxicity was performed in rats to determine the therapeutic doses. Breast cancer in rats was initiated by the administration of 7,12-dimethylbenz(α)anthracene (0.5 mg/100 g body weight) via single tail vein injection. The histopathological analysis after 24 weeks of carcinogenesis study depicted substantial repair of hyperplastic lesions. Immunohistochemical analysis revealed upregulation of Bax and p53 and downregulation of Bcl2 proteins and TUNEL assay showed an increase in apoptotic index in ruthenium–chrysin-treated groups as compared to the carcinogen control. Our findings from the in vitro and in vivo study support the continued investigation of ruthenium–chrysin complex possesses a potential chemotherapeutic activity against breast cancer and was efficient in reducing hyperplastic lesions in the mammary tissues of rats by inducing apoptosis. 相似文献
996.
997.
Rodrigo María A. Puche Eric Segura Matilde Arnal Adriana Rojo Carmen 《Hydrobiologia》2021,848(21):5203-5221
Hydrobiologia - We contribute to the knowledge of charophyte meadows as key components of aquatic systems by analysing how they affect wetland sediments. We performed a factorial-design experiment... 相似文献
998.
Along a west-to-east axis spanning the Galicia Bank region (Iberian margin) and the Mediterranean basin, a reduction in surface primary productivity and in seafloor flux of particulate organic carbon was mirrored in the in situ organic matter quantity and quality within the underlying deep-sea sediments at different water depths (1200, 1900 and 3000 m). Nematode standing stock (abundance and biomass) and genus and trophic composition were investigated to evaluate downward benthic-pelagic coupling. The longitudinal decline in seafloor particulate organic carbon flux was reflected by a reduction in benthic phytopigment concentrations and nematode standing stock. An exception was the station sampled at the Galicia Bank seamount, where despite the maximal particulate organic carbon flux estimate, we observed reduced pigment levels and nematode standing stock. The strong hydrodynamic forcing at this station was believed to be the main cause of the local decoupling between pelagic and benthic processes. Besides a longitudinal cline in nematode standing stock, we noticed a west-to-east gradient in nematode genus and feeding type composition (owing to an increasing importance of predatory/scavenging nematodes with longitude) governed by potential proxies for food availability (percentage of nitrogen, organic carbon, and total organic matter). Within-station variability in generic composition was elevated in sediments with lower phytopigment concentrations. Standing stock appeared to be regulated by sedimentation rates and benthic environmental variables, whereas genus composition covaried only with benthic environmental variables. The coupling between deep-sea nematode assemblages and surface water processes evidenced in the present study suggests that it is likely that climate change will affect the composition and function of deep-sea nematodes. 相似文献
999.
Timothy Caulfield Jim Evans Amy McGuire Christopher McCabe Tania Bubela Robert Cook-Deegan Jennifer Fishman Stuart Hogarth Fiona A. Miller Vardit Ravitsky Barbara Biesecker Pascal Borry Mildred K. Cho June C. Carroll Holly Etchegary Yann Joly Kazuto Kato Sandra Soo-Jin Lee Karen Rothenberg Pamela Sankar Michael J. Szego Pilar Ossorio Daryl Pullman Francois Rousseau Wendy J. Ungar Brenda Wilson 《PLoS biology》2013,11(11)
1000.
Cheng Cui Bishwanath Chatterjee Thomas P. Lozito Zhen Zhang Richard J. Francis Hisato Yagi Lisa M. Swanhart Subramaniam Sanker Deanne Francis Qing Yu Jovenal T. San Agustin Chandrakala Puligilla Tania Chatterjee Terry Tansey Xiaoqin Liu Matthew W. Kelley Elias T. Spiliotis Adam V. Kwiatkowski Rocky Tuan Gregory J. Pazour Neil A. Hukriede Cecilia W. Lo 《PLoS biology》2013,11(11)
Planar cell polarity (PCP) regulates cell alignment required for collective cell movement during embryonic development. This requires PCP/PCP effector proteins, some of which also play essential roles in ciliogenesis, highlighting the long-standing question of the role of the cilium in PCP. Wdpcp, a PCP effector, was recently shown to regulate both ciliogenesis and collective cell movement, but the underlying mechanism is unknown. Here we show Wdpcp can regulate PCP by direct modulation of the actin cytoskeleton. These studies were made possible by recovery of a Wdpcp mutant mouse model. Wdpcp-deficient mice exhibit phenotypes reminiscent of Bardet–Biedl/Meckel–Gruber ciliopathy syndromes, including cardiac outflow tract and cochlea defects associated with PCP perturbation. We observed Wdpcp is localized to the transition zone, and in Wdpcp-deficient cells, Sept2, Nphp1, and Mks1 were lost from the transition zone, indicating Wdpcp is required for recruitment of proteins essential for ciliogenesis. Wdpcp is also found in the cytoplasm, where it is localized in the actin cytoskeleton and in focal adhesions. Wdpcp interacts with Sept2 and is colocalized with Sept2 in actin filaments, but in Wdpcp-deficient cells, Sept2 was lost from the actin cytoskeleton, suggesting Wdpcp is required for Sept2 recruitment to actin filaments. Significantly, organization of the actin filaments and focal contacts were markedly changed in Wdpcp-deficient cells. This was associated with decreased membrane ruffling, failure to establish cell polarity, and loss of directional cell migration. These results suggest the PCP defects in Wdpcp mutants are not caused by loss of cilia, but by direct disruption of the actin cytoskeleton. Consistent with this, Wdpcp mutant cochlea has normal kinocilia and yet exhibits PCP defects. Together, these findings provide the first evidence, to our knowledge, that a PCP component required for ciliogenesis can directly modulate the actin cytoskeleton to regulate cell polarity and directional cell migration. 相似文献