全文获取类型
收费全文 | 4510篇 |
免费 | 254篇 |
国内免费 | 20篇 |
出版年
2023年 | 39篇 |
2022年 | 96篇 |
2021年 | 223篇 |
2020年 | 125篇 |
2019年 | 116篇 |
2018年 | 171篇 |
2017年 | 135篇 |
2016年 | 167篇 |
2015年 | 262篇 |
2014年 | 315篇 |
2013年 | 360篇 |
2012年 | 334篇 |
2011年 | 315篇 |
2010年 | 210篇 |
2009年 | 188篇 |
2008年 | 209篇 |
2007年 | 218篇 |
2006年 | 194篇 |
2005年 | 138篇 |
2004年 | 121篇 |
2003年 | 106篇 |
2002年 | 93篇 |
2001年 | 57篇 |
2000年 | 51篇 |
1999年 | 50篇 |
1998年 | 25篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 24篇 |
1992年 | 27篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1974年 | 9篇 |
1971年 | 13篇 |
1967年 | 9篇 |
排序方式: 共有4784条查询结果,搜索用时 15 毫秒
111.
Junaid Aslam Abdul Mujib Maheshwar Prasad Sharma 《Saudi Journal of Biological Sciences》2013,20(1):63-68
A protocol has been developed for in vitro plant regeneration from a nodal explant of Dracaena sanderiana Sander ex Mast. Nodal explant showed high callus induction potentiality on MS medium supplemented with 6.78 μM 2,4-dichlorophenoxyacetic acid (2,4-D) followed by 46.5 μM chlorophenoxy acetic acid (CPA). The highest frequency of shoot regeneration (85%) and number of shoots per explant (5.6) were obtained on medium supplemented with 7.84 μM N6-benzylaminopurine (BA). Rooting was high on MS solid compared to liquid medium when added with 7.38 μM indole-3-butyric acid (IBA). Fifty percent of the roots were also directly rooted as microcuttings on soil rite, sand and peat mixture (1:1:1). In vitro and ex vitro raised plantlets were used for acclimatization. More than 90% of the plantlets was successfully acclimatized and established in plastic pots. Ex vitro transferred plantlets were normal without any phenotypic aberrations. 相似文献
112.
Ji?í ?míd Ji?í Moravec Luká? Kratochvíl Václav Gvo?dík Abdul Karim Nasher Salem M. Busais Thomas Wilms Mohammed Y. Shobrak Salvador Carranza 《ZooKeys》2013,(355):79-107
A recent molecular phylogeny of the Arid clade of the genus Hemidactylus revealed that the recently described H. saba and two unnamed Hemidactylus species from Sinai, Saudi Arabia and Yemen form a well-supported monophyletic group within the Arabian radiation of the genus. The name ‘Hemidactylus saba species group’ is suggested for this clade. According to the results of morphological comparisons and the molecular analyses using two mitochondrial (12S and cytb) and four nuclear (cmos, mc1r, rag1, rag2) genes, the name Hemidactylus granosus Heyden, 1827 is resurrected from the synonymy of H. turcicus for the Sinai and Saudi Arabian species. The third species of this group from Yemen is described formally as a new species H. ulii
sp. n. The phylogenetic relationships of the members of ‘Hemidactylus saba species group’ are evaluated and the distribution and ecology of individual species are discussed. 相似文献
113.
Raheleh Halabian Hossein Abdul Tehrani Ali Jahanian-Najafabadi Mehryar Habibi Roudkenar 《Cell stress & chaperones》2013,18(6):785-800
Despite many advantages of mesenchymal stem cells (MSCs) that make them suitable for cell therapy purposes, their therapeutic application has been limited due to their susceptibility to several stresses (e.g., nutrient-poor environment, oxidative stress, and hypoxic and masses of cytotoxic factors) to which they are exposed during their preparation and following transplantation. Hence, reinforcing MSCs against these stresses is a challenge for both basic and clinician scientists. Recently, much attention has been directed toward equipping MSCs with cytoprotective factors to strengthen them against unfavorable microenvironments. Here, we engineered MSCs with lipocalin 2 (Lcn2), a cytoprotective factor that is naturally induced following exposure of cells to stresses imposed by the microenvironment. Lcn2 overexpression not only did not interfere with the multidifferentiation capacity of the MSCs but also granted many protective properties to them. Lcn2 potentiated MSCs to withstand oxidative, hypoxia, and serum deprivation (SD) conditions via antagonizing their induced cytotoxicity and apoptosis. Adhesion rate of MSCs to coated culture plates was also enhanced by Lcn2 overexpression. In addition, Lcn2 induced antioxidants and upregulated some growth factors in MSCs. Our findings suggested a new strategy for prevention of graft cell death in MSC-based cell therapy. 相似文献
114.
N. Madan N. Sundar Raj M.A. Farook S. Vimal C. Venkatesan S. Abdul Majeed K.S.N. Nambi A.S. Sahul Hameed 《Process Biochemistry》2013,48(12):1893-1898
Hepatopancreatic Parvovirus (HPV) causes infection in the early stages of shrimp leading to retarded growth, ultimaltely resulting in monetary loss to the shrimp farmers. To over come this situation screening of post-larvae (PL) by immunology-based diagnostics is required. Hence, the specific gene of capsid protein for HPV was cloned into pRSET B expression vector and rHCP overexpressed with 6-histidine tagged fusion protein in Escherichia coli BL21(DE3). Immunology-based methods like Western blot, dot blot and ELISA techniques were employed to detect HPV in infected samples using the antiserum raised in rabbits against recombinant HCP of HPV. The dot blot assay using anti-rHCP was found to be capable of detecting HPV in HPV infected post-larvae as early as at 24 h post infection. The antiserum could detect the HPV in the infected samples at 1 ng of total protein. HPV infection estimated by ELISA using anti-HCP and pure r-HCP as a standard was found to increase gradually during the course of infection from 24 h post infection. The sensitivity of antibody-based diagnostics employed in the present study was compared with that of PCR diagnostic method to screen the post-larvae for the detection of HPV. 相似文献
115.
116.
Elodie Lainey Alice Wolfromm Abdul Qader Sukkurwala Jean-Baptiste Micol Pierre Fenaux Lorenzo Galluzzi Oliver Kepp Guido Kroemer 《Cell cycle (Georgetown, Tex.)》2013,12(18):2978-2991
By means of an unbiased, automated fluorescence microscopy-based screen, we identified the epidermal growth factor receptor (EGFR) inhibitors erlotinib and gefitinib as potent enhancers of the differentiation of HL-60 acute myeloid leukemia (AML) cells exposed to suboptimal concentrations of vitamin A (all-trans retinoic acid, ATRA) or vitamin D (1α,25-hydroxycholecalciferol, VD). Erlotinib and gefitinib alone did not promote differentiation, yet stimulated the acquisition of morphological and biochemical maturation markers (including the expression of CD11b and CD14 as well as increased NADPH oxidase activity) when combined with either ATRA or VD. Moreover, the combination of erlotinib and ATRA or VD synergistically induced all the processes that are normally linked to terminal hematopoietic differentiation, namely, a delayed proliferation arrest in the G0/G1 phase of the cell cycle, cellular senescence, and apoptosis. Erlotinib potently inhibited the (auto)phosphorylation of mitogen-activated protein kinase 14 (MAPK14, best known as p38MAPK) and SRC family kinases (SFKs). If combined with the administration of ATRA or VD, the inhibition of p38MAPK or SFKs with specific pharmacological agents mimicked the pro-differentiation activity of erlotinib. These data were obtained with 2 distinct AML cell lines (HL-60 and MOLM-13 cells) and could be confirmed on primary leukemic blasts isolated from the circulation of AML patients. Altogether, these findings point to a new regimen for the treatment of AML, in which naturally occurring pro-differentiation agents (ATRA or VD) may be combined with EGFR inhibitors. 相似文献
117.
Zena A. Al-Mudaris Aman S. A. Majid Dan Ji Ban A. Al-Mudarris Shih-Hsun Chen Po-Huang Liang Hasnah Osman Shah Kamal Khan Jamal Din Amin M. S. Abdul Majid 《PloS one》2013,8(11)
Benzyl-o-vanillin and benzimidazole nucleus serve as important pharmacophore in drug discovery. The benzyl vanillin (2-(benzyloxy)-3-methoxybenzaldehyde) compound shows anti-proliferative activity in HL60 leukemia cancer cells and can effect cell cycle progression at G2/M phase. Its apoptosis activity was due to disruption of mitochondrial functioning. In this study, we have studied a series of compounds consisting of benzyl vanillin and benzimidazole structures. We hypothesize that by fusing these two structures we can produce compounds that have better anticancer activity with improved specificity particularly towards the leukemia cell line. Here we explored the anticancer activity of three compounds namely 2-(2-benzyloxy-3-methoxyphenyl)-1H-benzimidazole, 2MP, N-1-(2-benzyloxy-3-methoxybenzyl)-2-(2-benzyloxy-3-methoxyphenyl)-1H-benzimidazole, 2XP, and (R) and (S)-1-(2-benzyloxy-3-methoxyphenyl)-2, 2, 2-trichloroethyl benzenesulfonate, 3BS and compared their activity to 2-benzyloxy-3-methoxybenzaldehyde, (Bn1), the parent compound. 2XP and 3BS induces cell death of U937 leukemic cell line through DNA fragmentation that lead to the intrinsic caspase 9 activation. DNA binding study primarily by the equilibrium binding titration assay followed by the Viscosity study reveal the DNA binding through groove region with intrinsic binding constant 7.39 µM/bp and 6.86 µM/bp for 3BS and 2XP respectively. 2XP and 3BS showed strong DNA binding activity by the UV titration method with the computational drug modeling showed that both 2XP and 3BS failed to form any electrostatic linkages except via hydrophobic interaction through the minor groove region of the nucleic acid. The benzylvanillin alone (Bn1) has weak anticancer activity even after it was combined with the benzimidazole (2MP), but after addition of another benzylvanillin structure (2XP), stronger activity was observed. Also, the combination of benzylvanillin with benzenesulfonate (3BS) significantly improved the anticancer activity of Bn1. The present study provides a new insight of benzyl vanillin derivatives as potential anti-leukemic agent. 相似文献
118.
Anatoly Dubnovitsky Anders Sandberg M. Mahafuzur Rahman Iryna Benilova Christofer Lendel Torleif H?rd 《PloS one》2013,8(7)
Structural and biochemical studies of the aggregation of the amyloid-β peptide (Aβ) are important to understand the mechanisms of Alzheimer''s disease, but research is complicated by aggregate inhomogeneity and instability. We previously engineered a hairpin form of Aβ called Aβcc, which forms stable protofibrils that do not convert into amyloid fibrils. Here we provide a detailed characterization of Aβ42
cc protofibrils. Like wild type Aβ they appear as smooth rod-like particles with a diameter of 3.1 (±0.2) nm and typical lengths in the range 60 to 220 nm when observed by atomic force microscopy. Non-perturbing analytical ultracentrifugation and nanoparticle tracking analyses are consistent with such rod-like protofibrils. Aβ42
cc protofibrils bind the ANS dye indicating that they, like other toxic protein aggregates, expose hydrophobic surface. Assays with the OC/A11 pair of oligomer specific antibodies put Aβ42
cc protofibrils into the same class of species as fibrillar oligomers of wild type Aβ. Aβ42
cc protofibrils may be used to extract binding proteins in biological fluids and apolipoprotein E is readily detected as a binder in human serum. Finally, Aβ42
cc protofibrils act to attenuate spontaneous synaptic activity in mouse hippocampal neurons. The experiments indicate considerable structural and chemical similarities between protofibrils formed by Aβ42
cc and aggregates of wild type Aβ42. We suggest that Aβ42
cc protofibrils may be used in research and applications that require stable preparations of protofibrillar Aβ. 相似文献
119.
Diana E. Mitchell Chenkai Dai Mehdi A. Rahman Joong Ho Ahn Charles C. Della Santina Kathleen E. Cullen 《PloS one》2013,8(10)
The vestibular system detects motion of the head in space and in turn generates reflexes that are vital for our daily activities. The eye movements produced by the vestibulo-ocular reflex (VOR) play an essential role in stabilizing the visual axis (gaze), while vestibulo-spinal reflexes ensure the maintenance of head and body posture. The neuronal pathways from the vestibular periphery to the cervical spinal cord potentially serve a dual role, since they function to stabilize the head relative to inertial space and could thus contribute to gaze (eye-in-head + head-in-space) and posture stabilization. To date, however, the functional significance of vestibular-neck pathways in alert primates remains a matter of debate. Here we used a vestibular prosthesis to 1) quantify vestibularly-driven head movements in primates, and 2) assess whether these evoked head movements make a significant contribution to gaze as well as postural stabilization. We stimulated electrodes implanted in the horizontal semicircular canal of alert rhesus monkeys, and measured the head and eye movements evoked during a 100ms time period for which the contribution of longer latency voluntary inputs to the neck would be minimal. Our results show that prosthetic stimulation evoked significant head movements with latencies consistent with known vestibulo-spinal pathways. Furthermore, while the evoked head movements were substantially smaller than the coincidently evoked eye movements, they made a significant contribution to gaze stabilization, complementing the VOR to ensure that the appropriate gaze response is achieved. We speculate that analogous compensatory head movements will be evoked when implanted prosthetic devices are transitioned to human patients. 相似文献
120.
Eun Ju Lee Majid Rasool Kamli Smritee Pokharel Adeel Malik K. M. A. Tareq Abdul Roouf Bhat Hee-Bok Park Yong Seok Lee SangHoon Kim Bohsuk Yang Ki Young Chung Inho Choi 《PloS one》2013,8(11)