全文获取类型
收费全文 | 387篇 |
免费 | 37篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 7篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 20篇 |
2012年 | 31篇 |
2011年 | 31篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 19篇 |
2005年 | 19篇 |
2004年 | 30篇 |
2003年 | 19篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有424条查询结果,搜索用时 15 毫秒
401.
Nurit Keinan Yeela Scharff Oron Goldstein Michael Chamo Stefan Ilic Roi Gazit 《Cell death & disease》2021,12(2)
Animal models are necessary to study cancer and develop treatments. After decades of intensive research, effective treatments are available for only a few types of leukemia, while others are currently incurable. Our goal was to generate novel leukemia models in immunocompetent mice. We had achieved abilities for overexpression of multiple driving oncogenes simultaneously in normal primary cells, which can be transplanted and followed in vivo. Our experiments demonstrated the induction of primary malignant growth. Leukemia lines that model various types of leukemia, such as acute myeloid leukemia (AML) or chronic lymphocytic leukemia (CLL), were passaged robustly in congenic wild-type immunocompetent mice. These novel leukemia lines, which may complement previous models, offer the flexibility to generate tailored models of defined oncogenes of interest. The characterization of our leukemia models in immunocompetent animals can uncover the mechanisms of malignancy progression and offer a unique opportunity to stringently test anti-cancer chemotherapies.Subject terms: Cancer models, Haematopoietic stem cells, Leukaemia 相似文献
402.
Tamar Meshulam David Font-Vivanco Vered Blass Tamar Makov 《Journal of Industrial Ecology》2023,27(3):882-895
The digital sharing economy is commonly thought to promote sustainable consumption and improve material efficiency through better utilization of existing product stocks. However, the cost savings and convenience of using digital sharing platforms can ultimately stimulate additional demand for products and services. As a result, some or even all of the expected environmental benefits attributed to sharing could be offset, a phenomenon known as the rebound effect. Relying on a unique dataset covering over 750,000 food items shared in the United Kingdom through a free peer-to-peer food-sharing platform, we use econometric modeling, geo-spatial network analysis, and environmentally extended input–output analysis to quantify how much of the expected environmental benefits attributed to sharing are offset via rebound effects under seven re-spending scenarios. We find that rebound effects can offset 59–94% of expected greenhouse gas (GHG) emission reduction, 20–81% of expected water depletion benefits, and 23–90% of land use benefit as platform users re-spent the money saved from food sharing on other goods and services. Our results demonstrate that rebound effects could limit the potential to achieve meaningful reductions in environmental burdens through sharing, and highlight the importance of incorporating rebound effects in environmental assessments of the digital sharing economy. 相似文献
403.
Type C particles released from cultured murine myeloma MOPC-315 cells were significantly protected when the purification steps were all conducted in the presence of 10% chicken egg yolk fluid. The yolk fluid also slowed down the inactivation of viral particles during incubation at 37 degrees C and enabled full recovery of viral particles through several cycles of freezing and thawing. The purification of viral particles in the presence of yolk fluid did not affect the capability of the viral DNA polymerase to reverse-transcribe the virion RNA in vitro, nor that of the viral RNA to act as a functional template. 相似文献
404.
Robot-aided neuro-rehabilitation is increasingly being incorporated into rehabilitation practices. The aim of this study was to search for patterns in the data acquired by a robot in the baseline evaluation session which could predict progress over the next therapy sessions. Kinematic and kinetic data were acquired during robot-mediated evaluation sessions of 12 children with motor impairments due to hemiplegic cerebral palsy (CP). Time and wavelets features were extracted from the data and used for K-means clustering. The data were labeled by the Quality of Upper Extremity Skills Test (QUEST) and the gradient of improvement change in the QUEST between the baseline assessment and therapy follow-up one month after completion of 16 robot-mediated therapy sessions. Two distinct clusters segregated these 12 children into performers and non-performers in terms of the QUEST. 相似文献
405.
Effect of diet on survival,in the laboratory and the field,of sterile male Mediterranean fruit flies
To improve the effectiveness of the sterile insect technique against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), our objectives in this study were two‐fold. First, to evaluate the ability of sterile males of the Vienna‐8 strain to survive starvation, we compared them to wild males under laboratory conditions. The second objective was to determine the effect of protein‐rich nutrition on sterile male fly survival, under starvation conditions in the laboratory, under semi‐natural conditions in a field enclosure, and under natural conditions in the open field. Therefore, we released marked sterile flies of the two diet regimes, protein‐fed or protein‐deprived, and monitored their survival by recapturing them after 4, 6, and 7 days. In the laboratory, wild males endured starvation significantly better than sterile ones and protein addition to sterile fly diet resulted in even greater reduced capability to endure starvation. On the other hand, the addition of protein to sterile‐male diet did not affect their ability to survive in a field enclosure or in the open field. We conclude that under natural conditions, where food is available, sterile male fly survival is unaffected by protein‐rich pre‐release diet. 相似文献
406.
Vered Eshed Avi Gopher Ron Pinhasi Israel Hershkovitz 《American journal of physical anthropology》2010,143(1):121-133
This study addresses changes in health which were consequential to the Neolithic transition in the southern Levant, judged on the basis of the study of specific and nonspecific stress indicators, trauma, and degenerative joint disease in 200 Natufian (hunter‐gatherer) skeletons (10,500–8300 BC) and 205 Neolithic (agricultural) skeletons (8300–5500 BC) from the southern Levant. The comparison of the health profiles of pre‐Neolithic (Natufian) and Neolithic populations reveals a higher prevalence of lesions indicative of infectious diseases among the Neolithic population, and an overall reduction in the prevalence of skull trauma among males. No change over time was observed in the prevalence of degenerative joint disease. These results indicate that in the southern Levant the Neolithic transition did not simply lead to an overall deterioration in health but rather resulted in a complex health profile which was shaped by 1) an increase exposure to disease agents, 2) changes in diet, 3) population aggregation in larger and denser settlements, 4) changes in activity patterns and the division of labor, and possibly 5) a higher resistant immunological system and response capacity to environmental aggressions (mainly infections). Am J Phys Anthropol 143:121–133, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
407.
Recombinant TGF-beta1 stimulates bone marrow osteoprogenitor cell activity and bone matrix synthesis in osteopenic, old male mice. 总被引:3,自引:0,他引:3
We have previously hypothesized that the osteopenic changes seen in the skeletons of old male BALB/c mice are due to reductions in the availability and/or synthesis of bone TGF-beta which results in fewer, less osteogenic marrow osteoprogenitor cells (CFU-f; OPCs) and lower levels of bone formation. Among other things, this hypothesis would predict that introducing exogenous TGF-beta into old mice (growth factor replacement) should stimulate marrow CFU-f and increase bone formation. In the present study, we have tested this prediction and, indirectly the hypothesis, by injecting human recombinant TGF-beta1, i.p., into both young adult (4 month) and old mice (24 month). The effects of the growth factor on the skeleton were then assessed by measurements of trabecular bone volume, bone formation, fracture healing, and the number, proliferative, apoptotic, and alkaline phosphatase activity of marrow CFU-f/OPCs. Our data show that the introduction of 0.5 or 5.0 ug/day of TGF-beta1 into old mice for 20 days 1) increases trabecular bone volume, bone formation and the mineral apposition rate, 2) augments fracture healing, 3) increases the number and size of CFU-f colonies, and 4) increases proliferation and diminishes apoptosis of CFU-f in primary bone marrow cultures. Importantly, these stimulatory effects of injected growth factor are apparently age-specific, i.e., they are either not seen in young animals or, if seen, are found at much lower levels. While these observations do not exclude other possible mechanisms for the osteopenia of old mice, they provide further support for the hypothesis that, with age, diminished TGF-beta synthesis or availability results in a reduction in the marrow osteoprogenitor pool and bone formation. The findings also demonstrate that the latter changes can be reversed, at least transiently, by introducing exogenous TGF-beta1. 相似文献
408.
Helena Krasnov Yafit Cohen Eitan Goldshtein Miriam Silberstein Yoav Gazit Lior Blank 《Journal of Applied Entomology》2021,145(5):417-426
Understanding species movement in the agroecological system is an important theme in ecology. A mark–release–capture experiment was conducted to study the dispersion behaviour of the Mediterranean fruit fly, Ceratitis capitata (Wied.; Diptera: Tephritidae; Medfly) in northern Israel. Four pairs of pear and citrus orchards were selected for the field experiments. Sterile flies dyed with different colours were released in three seasons during 2015 and 2016, based on the phenological stages of the hosts. The total number of captured marked sterile flies per trap (FT) was approx 300 in both April and August. In November, FT values decreased by about 35% to approximately 200. The wild Medfly that were also captured showed an opposite trend, from an FT of 1.8 and 6.4 in April and August, respectively, to an FT of about 330 in November. Marked sterile flies were captured in both the release and the neighbouring orchard sites. We found that the Medfly migrates from pear to citrus orchards during spring and from citrus to pear during summer, when there are no fruit-bearing trees in the orchards. However, during November, when the wild Medfly population prevails in the area, a clear pattern of migration is hard to identify, perhaps because of a possible interaction with the wild fly's population. 相似文献
409.
Establishment and characterization of a cell line derived from human colon adenocarcinoma (HuCCL-14)
A continuous human colon carcinoma cell line (HuCCL-14) was established whose cells possess an epithelial-like morphology and are capable of growing in soft agar and on monolayers of normal cells. HuCCL-14 cells yielded high levels of carcinoembryonic antigen, and the analysis of their chromosomal constitution revealed a mode of 70 chromosomes per cell. HuCCL-14 cells produce malignant tumors when injected into nude mice. Preliminary virologic studies indicate the release of RNA particles having a density of 1.15--1.19 g/ml. 相似文献
410.
Vered Naor Jaime Kigel Yosi Ben-Tal Meira Ziv 《Journal of Plant Growth Regulation》2008,27(3):211-220
Phenologic changes and variation in the level of endogenous gibberellins (GAs), abscisic acid (ABA), carbohydrate content,
and α-amylase activity were examined in colored Zantedeschia spp. cv. Cala Gold. These changes were examined in the primary bud tissues and in the attached tuber tissue during the growth
cycle. Dormant tubers were dry-stored at 20°C for 3 months, planted in a phytotron, and grown under 22/16 ± 1°C. Plant development
was monitored under continued irrigation until leaf senescence and tuber dormancy. GAs and ABA were extracted from the primary
bud tissues, fractionated by HPLC, and analyzed using GC-SIM. Starch, glucose, soluble protein, and α-amylase activity were
monitored in the tuber tissue attached to the primary bud. Endogenous changes in GAs and ABA in the primary bud were correlated
with endogenous changes in carbohydrate content and α-amylase activity in the attached tuber tissue. These correlations were
observed during the rest and the growth periods and were associated with developmental changes in the plant, that is, bud
dormancy relaxation, bud growth, and inflorescence differentiation. ABA content decreased and a transient pulse of GA was
measured in the primary bud concomitantly with the onset of shoot elongation in dry tubers during storage, before planting.
The sharp increase of GAs in the bud preceded inflorescence differentiation as observed in dissected apices by about 15 days,
as well as the increase in α-amylase activity in the attached tuber tissue. A steep decrease in starch level was measured
in the tuber after planting, concomitantly with massive plant growth. These findings suggest a possible involvement of gibberellin
in the initiation of α-amylase activity during dormancy relaxation in colored Zantedeschia and in the autonomous induction of flowering. 相似文献