全文获取类型
收费全文 | 1498篇 |
免费 | 63篇 |
国内免费 | 19篇 |
专业分类
1580篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 22篇 |
2021年 | 38篇 |
2020年 | 28篇 |
2019年 | 32篇 |
2018年 | 38篇 |
2017年 | 30篇 |
2016年 | 27篇 |
2015年 | 33篇 |
2014年 | 113篇 |
2013年 | 124篇 |
2012年 | 85篇 |
2011年 | 139篇 |
2010年 | 114篇 |
2009年 | 88篇 |
2008年 | 96篇 |
2007年 | 73篇 |
2006年 | 79篇 |
2005年 | 56篇 |
2004年 | 71篇 |
2003年 | 50篇 |
2002年 | 23篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1580条查询结果,搜索用时 15 毫秒
21.
Shanyi Li Chan Wang Ying Dai Yan Yang Hongwei Pan Jingxiang Zhong Jiansu Chen 《Tissue & cell》2013,45(6):387-396
Reagents which can promote the proliferation, adhesion and migration of cultured corneal endothelial cells (CECs) will be helpful for the treatment of reduced visual acuity due to CECs deficiency. The objectives of this study were to investigate the potential use of an inhibitor of Rho-associated protein kinase (ROCK), Y-27632, to cultured bovine corneal endothelial cells (B-CECs) and evaluated its effects on the proliferation, adhesion and migration of B-CECs. The proliferation of cultured B-CECs was moderately enhanced by 10 μM Y-27632. Y-27632 induced fibroblast-like morphological changes in the cultured B-CECs and normal cell morphology could recover after Y-27632 removal. In addition, Y-27632 was found to significantly enhance the adhesion and migration of B-CECs. Furthermore, the hanging drop aggregation assay showed that Y-27632 promoted B-CECs to form cellular networks and sheets, which proliferated along the liquid–air interface and migrated to the surface of the lid of dish. Our study demonstrated that Y-27632 is a potentially powerful reagent which can enhance the proliferation of cultured B-CECs. Y-27632 will be useful in CEC injection therapy and topical application for CEC deficiency. 相似文献
22.
Keith A. Hobson 《Oecologia》1999,120(3):314-326
To understand the ecology of migratory animals it is important to link geographic regions used by individuals including breeding,
wintering, and intermediate stopover sites. Previous conventional approaches used to track animal movements have relied on
extrinsic markers and typically the subsequent recovery of individuals. This approach has generally been inappropriate for
most small, or non-game animals. The use of intrinsic markers such as fatty acid profiles, molecular DNA analyses, and the
measurement of naturally occurring stable isotopes in animal tissues offer alternative approaches. This paper reviews the
use of stable isotope analyses (primarily δ13C, δ15N, δ34S, δD, δ87Sr) to trace nutritional origin and migration in animals. This approach relies on the fact that foodweb isotopic signatures
are reflected in the tissues of organisms and that such signatures can vary spatially based on a variety of biogeochemical
processes. Organisms moving between isotopically distinct foodwebs can carry with them information on the location of previous
feeding. Such an approach has been used to track animal use of inshore versus offshore, marine versus freshwater, terrestrial
C3 versus marine, terrestrial mesic versus xeric, and C3 versus C4 or Crassulacean acid metabolism foodwebs. More recently, the use of stable hydrogen isotope analyses (δD) to link organisms
to broad geographic origin in North America is based on large-scale isotopic contours of growing-season average δD values
in precipitation. This technique, especially when combined with the assay of other stable isotopes, will be extremely useful
in helping to track migration and movement of a wide range of animals from insects to birds and mammals. Future research to
refine our understanding of natural and anthropogenic-induced isotopic gradients in nature, and to explore the use of stable
isotopes of other elements, is recommended.
Received: 1 July 1998 / Accepted: 9 December 1998 相似文献
23.
T. K. McCarthy P. Frankiewicz P. Cullen M. Blaszkowski W. O’Connor D. Doherty 《Hydrobiologia》2008,609(1):109-124
The Shannon, Ireland’s largest river, is used for hydroelectricity generation since 1929. Subsequently, the Electricity Supply
Board assumed responsibility for management of its eel stocks, due to the impact of the hydro-dam on recruitment to the commercial
fishery. In order to negate a decline in juvenile recruitment resulting from the installation of hydroelectric facilities,
management was focused on stocking lakes with elvers and fingerling eels. These were trapped at the hydropower facilities
and in estuarine tributaries during their up-stream migrations. Due to the decline of natural recruitment in more recent times,
attempts have also been made to develop an estuarine glass eel fishery. Stock levels are then monitored through annual surveys
of the population trends of juvenile (glass eel, elver), growing phase (yellow eel) and downstream migrating pre-spawners
(silver eels). Survey results and fishery management programmes are reviewed in this article. In addition to the long-term
effects the hydroelectric facilities have had on the stock levels, there is also an annual effect on the migratory patterns
of downstream migratory silver eels. In the lower reaches of the river system flow rates are regulated by the hydroelectric
stations. We review previous work that had highlighted the importance of flow in determining the timing of the silver eels
migrations, and assess the relationship between flow and migration in more detail through the use of hydroacoustic and telemetric
studies. Current research on seaward migrating silver eel populations, suggests that spawner escapement rates can most effectively
be increased by trapping migrating eels at fishing weirs located up-stream of the power station and transporting them towards
the estuary.
Guest editors: R. L. Welcomme & G. Marmulla
Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries 相似文献
24.
青藏公路沿线白昼交通运输等人类活动对藏羚羊迁徙的影响 总被引:24,自引:0,他引:24
To study effects of traffic during daytime and other human activities, we conducted surveys on the migration of Tibetan antelope Pantholops hodgsoni along the Qinghai-Tibet highway between Kunlun Mountain Pass to Wudaoliang,using line transects (LT) from June to September in 2001 and 2002, Data were collected for 64 days with 17 days in 2001, and 47days in 2002. The Stationary Observation Method (SOM) was also adopted for the investigation of status of the disturbance from traffic when antelopes passing the highway and the traffic situation from August 6 to 28 (6 : 30-19: 00), 4 to 20 (6: 00- 18: 00) and from December 21 to 29 (9:00- 19: 00) in 2002. The results showed that,the period of migration in 2002 was more prolonged than in 2001, and it took at least 45 min for each group to cross the highway, with success ratio of only 30.2 %, and the traffic flow of summer daytime was 76/h, while the winter‘s traffic flow was 29/h. Highway and rail traffic should be managed during daylight hours from June to August, to allow for the migration of the antelopes. Also conservation education and a further survey should be emphasized for the protection on the species [Acta Zoologica Sinica 50 (4) : 669-674, 2004]. 相似文献
25.
Maddala R Chauhan BK Walker C Zheng Y Robinson ML Lang RA Rao PV 《Developmental biology》2011,360(1):30-43
Morphogenesis and shape of the ocular lens depend on epithelial cell elongation and differentiation into fiber cells, followed by the symmetric and compact organization of fiber cells within an enclosed extracellular matrix-enriched elastic capsule. The cellular mechanisms orchestrating these different events however, remain obscure. We investigated the role of the Rac1 GTPase in these processes by targeted deletion of expression using the conditional gene knockout (cKO) approach. Rac1 cKO mice were derived from two different Cre (Le-Cre and MLR-10) transgenic mice in which lens-specific Cre expression starts at embryonic day 8.75 and 10.5, respectively, in both the lens epithelium and fiber cells. The Le-Cre/Rac1 cKO mice exhibited an early-onset (E12.5) and severe lens phenotype compared to the MLR-10/Rac1 cKO (E15.5) mice. While the Le-Cre/Rac1 cKO lenses displayed delayed primary fiber cell elongation, lenses from both Rac1 cKO strains were characterized by abnormal shape, impaired secondary fiber cell migration, sutural defects and thinning of the posterior capsule which often led to rupture. Lens fiber cell N-cadherin/β-catenin/Rap1/Nectin-based cell–cell junction formation and WAVE-2/Abi-2/Nap1-regulated actin polymerization were impaired in the Rac1 deficient mice. Additionally, the Rac1 cKO lenses were characterized by a shortened epithelial sheet, reduced levels of extracellular matrix (ECM) proteins and increased apoptosis. Taken together, these data uncover the essential role of Rac1 GTPase activity in establishment and maintenance of lens shape, suture formation and capsule integrity, and in fiber cell migration, adhesion and survival, via regulation of actin cytoskeletal dynamics, cell adhesive interactions and ECM turnover. 相似文献
26.
Yu Shun Tian 《Biochemical and biophysical research communications》2009,386(3):499-4024
Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21cip1 and p27kip1 and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification. 相似文献
27.
Akihiko Nishikimi Mutsuko Kukimoto-Niino Shigeyuki Yokoyama Yoshinori Fukui 《Experimental cell research》2013
DOCK proteins constitute a family of evolutionarily conserved guanine nucleotide exchange factors (GEFs) for Rho family of GTPases. Although DOCK family proteins do not contain the Dbl homology domain typically found in GEFs, they mediate the GTP–GDP exchange reaction through DHR-2 domain. Accumulating evidence indicates that the DOCK proteins act as major GEFs in varied biological settings. For example, DOCK2, which is predominantly expressed in hematopoietic cells, regulates migration and activation of leukocytes through Rac activation. On the other hand, it was recently reported that mutations of DOCK8, another member of the DOCK family proteins, cause a combined immunodeficiency syndrome in humans. This article reviews the structure, functions and signaling of DOCK2 and DOCK8, especially focusing on their roles in immune responses. 相似文献
28.
Involvement of Matrix Metalloproteinases on the Inhibition of Cells Invasion and Migration by Emodin in Human Neuroblastoma SH-SY5Y Cells 总被引:1,自引:0,他引:1
Hsu-Feng Lu Kuang-Chi Lai Shu-Chun Hsu Hui-Ju Lin Chao-Lin Kuo Ching-Lung Liao Jai-Sing Yang Jing-Gung Chung 《Neurochemical research》2009,34(9):1575-1583
Emodin (1,3,8-trihydroxy-6-methylanthaquinone), an active component present in the root and rhizome of Rheum palmatum L. (Polygonaceae) has anti-bacterial, anti-tumor, diuretic and vasorelaxant effects. However, its mechanism of action on
the cell migration and invasion of human neuroblastoma cancer SH-SY5Y cells is not fully understood. In this study, firstly,
the effects of emodin on the percentage of viable cells were examined by using MTT assay and it was found that emodin induced
dose-and time-dependent inhibition in human neuroblastoma SH-SY5Y cells. Second, the effects of emodin on the migration and
invasion of SH-SY5Y cells were examined by using wound assay and matrigel counting and the results showed that emodin suppressed
the migration and invasion of SH-SY5Y cells. Third, we examined the effect of emodin on the levels of associated proteins
by using Western blotting and the results indicated that emodin inhibited the levels of GRB2, RhoA, HIF-1α, VEGF, FAK, iNOS,
COX2, p-p38, p-c-jun, MMP2, MMP9 and MMP7 but promoted the levels of PKC, PI3K, MEKK3 and NF-κB p65 that led to the inhibition
of migration and invasion of SH-SY5Y cells in vitro. 相似文献
29.
30.
Zhongyin Yang Chen Li Chao Yan Jianfang Li Min Yan Bingya Liu Zhenggang Zhu Yingli Wu Qinlong Gu 《生物化学与生物物理学报:疾病的分子基础》2019,1865(1):181-192
The kinesin family member 14 (KIF14) is a potential oncogene and is involved in the metastasis of various cancers. Nevertheless, its function in gastric cancer (GC) remains poorly defined. The expression of KIF14 was examined in GC cell lines and a clinical cohort of GC specimens by qPCR, western blotting and immunohistochemistry (IHC) staining. The relationship between KIF14 expression and the clinicopathological features was analyzed. The effect of KIF14 on cell proliferation, colony formation, invasion and migration were investigated in vitro and in vivo. The expression of KIF14 was significantly increased in the GC tissues and cell lines. High KIF14 expression was associated with tumor stage, tumor-node-metastasis (TNM) stage and metastasis. KIF14 was an independent prognostic factor for the overall survival of GC, and a higher expression of KIF14 predicted a poorer survival. KIF14 silencing resulted in attenuated proliferation, invasion and migration in human gastric cancer cells, whereas KIF14 ectopic expression facilitated these biological abilities. Notably, the depressed expression of KIF14 inhibited Akt phosphorylation, while overexpressed KIF14 augmented Akt phosphorylation. Additionally, there was a significant correlation between the expression of KIF14 and p?Akt in GC tissues. Importantly, the proliferation, invasion and migration of the GC cells, which was promoted by KIF14 overexpression, was abolished by the Akt inhibitor MK-2206, while Akt overexpression greatly rescued the effects induced by KIF14 knockdown. Our findings are the first to demonstrate that KIF14 is overexpressed in GC, is correlated with poor prognosis and plays a crucial role in the progression and metastasis of GC. 相似文献