全文获取类型
收费全文 | 2407篇 |
免费 | 204篇 |
国内免费 | 1篇 |
出版年
2022年 | 24篇 |
2021年 | 56篇 |
2020年 | 43篇 |
2019年 | 43篇 |
2018年 | 71篇 |
2017年 | 60篇 |
2016年 | 78篇 |
2015年 | 94篇 |
2014年 | 124篇 |
2013年 | 154篇 |
2012年 | 184篇 |
2011年 | 187篇 |
2010年 | 106篇 |
2009年 | 91篇 |
2008年 | 104篇 |
2007年 | 112篇 |
2006年 | 117篇 |
2005年 | 95篇 |
2004年 | 90篇 |
2003年 | 60篇 |
2002年 | 57篇 |
2001年 | 56篇 |
2000年 | 39篇 |
1999年 | 40篇 |
1998年 | 19篇 |
1997年 | 30篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 22篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 20篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1972年 | 12篇 |
1967年 | 10篇 |
排序方式: 共有2612条查询结果,搜索用时 62 毫秒
91.
Monika Sodhi M. Mukesh B. P. Mishra S. P. S. Ahlawat B. Prakash R. C. Sobti 《Animal biotechnology》2013,24(1):16-29
The present study aims to understand the existing genetic diversity and structure of six native cattle breeds (Rathi, Tharparkar, Nagori, Mewati, Gir, and Kankrej) adapted to the north-western arid and semi-arid region of India based on microsatellite loci. Various diversity estimates, mean number of alleles (12.84); effective number of alleles (5.02); gene diversity (0.769), and observed heterozygosity (0.667) reflected the existence of substantial within-breed diversity in all the investigated cattle breeds. Mean estimates of F-statistics: FIT = 0.144 ± 0.023, FIS = 0.071 ± 0.021, and FST = 0.078 ± 0.014 were significantly different from zero (P < 0.05). The interbreed relationships indicated moderate level of breed differentiation between the six cattle breeds with least differentiation between Kankrej-Mewati pair. The phylogeny structuring further supported close grouping of Kankrej and Mewati breeds. Correspondence analysis plotted Rathi, Tharparkar, and Gir individuals into three separate areas of multivariate space; whereas, Kankrej, Mewati, and Nagori cattle showed low breed specific clustering. This reflected the existence of discrete genetic structure for Tharparkar, Rathi, and Gir, the prominent dairy breeds of the region; whereas, admixture was observed for Kankrej, Mewati, and Nagori individuals. 相似文献
92.
Ravi Ranjan Rakesh Kumar Singh Thirupathi Yasotha Manish Kumar Kuldeep Kumar Renu Singh Monzamul Houque Vijay Prakash Mourya Gyanendra Singh Mihir Sarkar Bikash Chandra Das Sadhan Bag 《In vitro cellular & developmental biology. Animal》2013,49(7):486-491
The present study was conducted to see the in vivo developmental potency of caprine parthenogenetic embryos generated in a modified way. The good quality caprine oocytes were matured in presence of cytochalasin B (CCB) and then activated by 7% ethanol followed by 2 mM 6-dimethyl amino purine (6-DMAP) and embryo development was recorded. Early stage parthenogenetic embryos (two to four cells) were surgically transferred in recipients (10). The pregnancy diagnosis was done by nonreturn to oestrus, ultrasonography (USG), and progesterone estimation. The levels of progesterone were above normal values (1 ng/ml) of pregnancy and fall below the level of pregnancy just before retuned to oestrus. Progesterone profile revealed that out of ten recipients (G1–G10), four goats (G1, G2, G3, and G5) returned to oestrus after 43?±?7.29 (Mean?±?SE) d of embryo transfer and six goats (G4, G6, G7, G8, G9, and G10) did not return to cycle even after 70 d of embryo transfer. In three recipients (G4, G5, and G6), the USG on day 40 revealed that there was fluid filled uterine body with solid fetus-like structure. These might be dead fetus and had started resorption. The progesterone profile also corroborated the assumption of pregnancy in these animals. Authors believe that this may be the first report on in vivo diploid parthenogenetic embryo development in caprine species. 相似文献
93.
Prakash Maran Jeganathan Sivakumar Venkatachalam Thirugnanasambandham Karichappan Sridar Ramasamy 《Preparative biochemistry & biotechnology》2013,43(1):56-67
The objective of the present study is to find out the optimum extraction conditions for extraction of polyphenols from red grapes using Box–Behnken design. Red grapes polyphenols were extracted using acid–ethanol solvent at various extraction temperature (40–60°C), extraction time (20–100 min) and different solid–liquid ratio (1:5–1:15 g:ml). The effect (main and interactive) of extraction conditions on total anthocyanin, phenolic and flavonoid content were studied using Box–Behnken design (three factors at three levels). The results showed that the contribution of the quadratic model was significant for all the responses. Second-order mathematical regression models were developed and were found to fit well with observed data. Derringer's desirability function methodology was performed to find out the optimal conditions based on both individual and combinations of all responses (extraction temperature: 57°C, time: 61 min, and solid–liquid ratio: 1:8.7 g:ml) were established. At this optimal condition, the anthocyanin yield, total phenolic and flavonoid content were 73.92 mg/100 g, 221.4 mg GAE/100 g, and 79.08 mg CE/100 g, respectively. A desirability value of 0.902 was achieved at this point. 相似文献
94.
Pradeep Kumar Papolu Nagavara Prasad Gantasala Divya Kamaraju Prakash Banakar Rohini Sreevathsa Uma Rao 《PloS one》2013,8(11)
Root knot nematode, Meloidogyne incognita, is an obligate sedentary endoparasite that infects a large number of crop species and causes substantial yield losses. Non-chemical based control strategies for these nematodes are gaining importance. In the present study, we have demonstrated the significance of two FMRFamide like peptide genes (flp-14 and flp-18) for infection and development of resistance to M. incognita through host-derived RNAi. The study demonstrated both in vitro and in planta validation of RNAi-induced silencing of the two genes cloned from J2 stage of M. incognita. In vitro silencing of both the genes interfered with nematode migration towards the host roots and subsequent invasion into the roots. Transgenic tobacco lines were developed with RNAi constructs of flp-14 and flp-18 and evaluated against M. incognita. The transformed plants did not show any visible phenotypic variations suggesting the absence of any off-target effects. Bioefficacy studies with deliberate challenging of M. incognita resulted in 50-80% reduction in infection and multiplication confirming the silencing effect. We have provided evidence for in vitro and in planta silencing of the genes by expression analysis using qRT-PCR. Thus the identified genes and the strategy can be used as a potential tool for the control of M. incognita. This is the first ever report that has revealed the utility of host delivered RNAi of flps to control M. incognita. The strategy can also be extended to other crops and nematodes. 相似文献
95.
96.
Michelle W. Voss Chelsea N. Wong Pauline L. Baniqued Jonathan H. Burdette Kirk I. Erickson Ruchika Shaurya Prakash Edward McAuley Paul J. Laurienti Arthur F. Kramer 《PloS one》2013,8(11)
To better understand age differences in brain function and behavior, the current study applied network science to model functional interactions between brain regions. We observed a shift in network topology whereby for older adults subcortical and cerebellar structures overlapping with the Salience network had more connectivity to the rest of the brain, coupled with fragmentation of large-scale cortical networks such as the Default and Fronto-Parietal networks. Additionally, greater integration of the dorsal medial thalamus and red nucleus in the Salience network was associated with greater satisfaction with life for older adults, which is consistent with theoretical predictions of age-related increases in emotion regulation that are thought to help maintain well-being and life satisfaction in late adulthood. In regard to cognitive abilities, greater ventral medial prefrontal cortex coherence with its topological neighbors in the Default Network was associated with faster processing speed. Results suggest that large-scale organizing properties of the brain differ with normal aging, and this perspective may offer novel insight into understanding age-related differences in cognitive function and well-being. 相似文献
97.
98.
Deepak Poudyal Xiangli Cui Phuong Mai Le Anne B. Hofseth Anthony Windust Mitzi Nagarkatti Prakash S. Nagarkatti Aaron J. Schetter Curtis C. Harris Lorne J. Hofseth 《PloS one》2013,8(10)
Metastasis of colon cancer cells increases the risk of colon cancer mortality. We have recently shown that American ginseng prevents colon cancer, and a Hexane extract of American Ginseng (HAG) has particularly potent anti-inflammatory and anti-cancer properties. Dysregulated microRNA (miR) expression has been observed in several disease conditions including colon cancer. Using global miR expression profiling, we observed increased miR-29b in colon cancer cells following exposure to HAG. Since miR-29b plays a role in regulating the migration of cancer cells, we hypothesized that HAG induces miR-29b expression to target matrix metalloproteinase-2 (MMP-2) thereby suppressing the migration of colon cancer cells. Results are consistent with this hypothesis. Our study supports the understanding that targeting MMP-2 by miR-29b is a mechanism by which HAG suppresses the migration of colon cancer cells. 相似文献
99.
Vivek Khanna Manish Jain Vishal Singh Jitendra S. Kanshana Prem Prakash Manoj K. Barthwal Puvvada S. R. Murthy Madhu Dikshit 《PloS one》2013,8(10)
Effect of long term cholesterol diet withdrawal on accelerated atherosclerosis in iliac artery of New Zealand White (NZW) rabbits has not been explored so far. Atherosclerosis was thus induced in rabbits by a combination of balloon injury and atherogenic diet (AD) (1% cholesterol and 6% peanut oil) feeding for 8 weeks (baseline) followed by chow diet (CD) feeding for 4, 8, 16, 32, 50 and 64 weeks. The plaque characterization was done using histology, real time RT-PCR and vasoreactivity studies. Significant elevation in plasma lipids with AD feeding was normalized following 16 weeks of CD feeding. However, baseline comparison showed advanced plaque features even after 8 weeks of CD period with significant elevation in intima/media thickness ratio and plaque area later showing reduction at 50 and 64 weeks CD periods. Lesion lipid accumulation and CD68 positivity was maintained till 16 weeks of CD feeding which significantly reduced from 32 to 64 weeks CD periods. Baseline comparison showed significant increase in ground substance, MMP-9 and significant decrease in α-actin and collagen content at 8 weeks CD period indicating features of unstable plaque. These features regressed up to 64 weeks of CD. Partial restoration of functional vasoconstriction and vasorelaxation was seen after 64 weeks of CD feeding. mRNA expression of MCP-1, VCAM-1, collagen type I and III, MMP-9, TIMP-1, IFN-γ, TNF-α, IL-10 and eNOS supported the above findings. The study thus reveals insights into initial plaque instability and subsequent regression on AD withdrawal in this model. These results are suggestive of an appropriate window for drug intervention for plaque stability/regression and restenosis as well as improves understanding of plaque regression phenomenon in this model. 相似文献
100.
Prakash Rath Bachchu Lal Olutobi Ajala Yunqing Li Shuli Xia Jin Kim John Laterra 《Translational oncology》2013,6(2):104-IN1
Solid malignancies contain sphere-forming stem-like cells that are particularly efficient in propagating tumors. Identifying agents that target these cells will advance the development of more effective therapies. Recent converging evidence shows that c-Met expression marks tumor-initiating stem-like cells and that c-Met signaling drives human glioblastoma multiforme (GBM) cell stemness in vitro. However, the degree to which tumor-propagating stem-like cells depend on c-Met signaling in histologically complex cancers remains unknown. We examined the effects of in vivo c-Met pathway inhibitor therapy on tumor-propagating stem-like cells in human GBM xenografts. Animals bearing pre-established tumor xenografts expressing activated c-Met were treated with either neutralizing anti- hepatocyte growth factor (HGF) monoclonal antibody L2G7 or with the c-Met kinase inhibitor PF2341066 (Crizotinib). c-Met pathway inhibition inhibited tumor growth, depleted tumors of sphere-forming cells, and inhibited tumor expression of stem cell markers CD133, Sox2, Nanog, and Musashi. Withdrawing c-Met pathway inhibitor therapy resulted in a substantial rebound in stem cell marker expression concurrent with tumor recurrence. Cells derived from xenografts treated with anti-HGF in vivo were depleted of tumor-propagating potential as determined by in vivo serial dilution tumor-propagating assay. Furthermore, daughter xenografts that did form were 12-fold smaller than controls. These findings show that stem-like tumor-initiating cells are dynamically regulated by c-Met signaling in vivo and that c-Met pathway inhibitors can deplete tumors of their tumor-propagating stem-like cells. 相似文献