全文获取类型
收费全文 | 4461篇 |
免费 | 288篇 |
国内免费 | 13篇 |
出版年
2023年 | 36篇 |
2022年 | 46篇 |
2021年 | 229篇 |
2020年 | 123篇 |
2019年 | 133篇 |
2018年 | 151篇 |
2017年 | 145篇 |
2016年 | 184篇 |
2015年 | 245篇 |
2014年 | 287篇 |
2013年 | 381篇 |
2012年 | 348篇 |
2011年 | 321篇 |
2010年 | 232篇 |
2009年 | 201篇 |
2008年 | 204篇 |
2007年 | 199篇 |
2006年 | 158篇 |
2005年 | 128篇 |
2004年 | 122篇 |
2003年 | 112篇 |
2002年 | 110篇 |
2001年 | 66篇 |
2000年 | 67篇 |
1999年 | 52篇 |
1998年 | 16篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 35篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 27篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1980年 | 11篇 |
1978年 | 12篇 |
1976年 | 8篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1971年 | 9篇 |
1969年 | 7篇 |
1967年 | 9篇 |
排序方式: 共有4762条查询结果,搜索用时 15 毫秒
1.
2.
M. Y. Shukor M. F. Rahman Z. Suhaili N. A. Shamaan M. A. Syed 《World journal of microbiology & biotechnology》2009,25(7):1225-1234
A bacterium that was able to tolerate and reduce as high as 50 mM of sodium molybdate to molybdenum blue has been isolated
from a metal recycling ground. The isolate was tentatively identified as Serratia sp. strain Dr.Y8 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny.
ANOVA analysis showed that isolate Dr.Y8 produced significantly higher (P < 0.05) amount of Mo-blue with 3, 5.1 and 11.3 times more molybdenum blue than previously isolated molybdenum reducers such
as Serratia
marcescens strain Dr.Y6, E. coli K12 and E. cloacae strain 48, respectively. Its molybdate reduction characteristics were studied in this work. Electron donor sources such as
sucrose, mannitol, fructose, glucose and starch supported molybdate reduction. The optimum phosphate, pH and temperature that
supported molybdate reduction were 5 mM, pH 6.0 and 37°C, respectively. The molybdenum blue produced from cellular reduction
exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium,
silver, copper and mercury resulted in approximately 61, 57, 80, and 69% inhibition of the molybdenum-reducing activity at
1 mM, respectively. The reduction characteristics of strain Dr.Y8 suggest that it would be useful in future molybdenum bioremediation. 相似文献
3.
Although cryopreservation has been developed and optimized over the past decades, it causes various stresses, including cold shock, osmotic stress, and ice crystal formation, thereby reducing fertility. During cryopreservation, addition of cryoprotective agent (CPA) is crucial for protecting spermatozoa from freezing damage. However, the intrinsic toxicity and osmotic stress induced by CPA cause damage to spermatozoa. To identify the effects of CPA addition during cryopreservation, we assessed the motility (%), motion kinematics, capacitation status, and viability of epididymal spermatozoa using computer-assisted sperm analysis and Hoechst 33258/chlortetracycline fluorescence staining. Moreover, the effects of CPA addition were also demonstrated at the proteome level using two-dimensional electrophoresis. Our results demonstrated that CPA addition significantly reduced sperm motility (%), curvilinear velocity, viability (%), and non-capacitated spermatozoa, whereas straightness and acrosome-reacted spermatozoa increased significantly (p < 0.05). Ten proteins were differentially expressed (two decreased and eight increased) (>3 fold, p < 0.05) after CPA, whereas NADH dehydrogenase flavoprotein 2, f-actin-capping protein subunit beta, superoxide dismutase 2, and outer dense fiber protein 2 were associated with several important signaling pathways (p < 0.05). The present study provides a mechanistic basis for specific cryostresses and potential markers of CPA-induced stress. Therefore, these might provide information about the development of safe biomaterials for cryopreservation and basic ground for sperm cryopreservation. 相似文献
4.
The incidence of postoperative deep vein thrombosis diagnosed by radioisotope scanning in 100 Sudanese patients aged 40 or over was 12%. This compares with an incidence of nearly 30% in 542 patients reported from British hospitals using the same diagnostic technique. The reason for the difference is obscure and needs further investigation. 相似文献
5.
6.
7.
Activity of phosphate-dissolving bacteria in Egyptian soils 总被引:1,自引:0,他引:1
S. M. Taha S. A. Z. Mahmoud A. Halim El-Damaty A. M. Abd El-Hafez 《Plant and Soil》1969,31(1):149-160
8.
9.
F Nagase K Ueda K Kawashima S M Jamshedur Rahman K Isobe T Yoshida Y Hasegawa K Ando T Iwamoto E Nagura 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(7):2359-2365
When a murine leukemia L1210-specific Lyt-2+ T cell clone, K7L, was injected i.p. into CD2F1 mice together with L1210, the normal growth of L1210 in the peritoneal cavity of the mice at the early stage (days 0 to 5) was strongly inhibited, but L1210 grew progressively at the middle-stage (days 5 to 10), and then was rejected at the late stage (days 10 to 20). The mice thus survived for long times (more than 60 days), whereas the normal control injected with L1210 alone died within 14 days. The L1210 that grew at the middle stage in mice initially inoculated with L1210 together with K7L was a K7L-insensitive (K7L-) variant. All of eight tumor clones established from L1210-K7L- by limiting dilution was insensitive to the antitumor activity of K7L, and this property of tumor clones was stable after repeated in vitro passage. The initial depression of the L1210 growth by K7L followed by growth and rejection of the variant L1210-K7L- by the host T cell activity was then found to prepare a strong, long-lasting (more than 3 mo) immunity to protect mice against the high-dose (10(7) cells per mouse) challenge of original L1210. Corresponding to this result, definite tumor (L1210)-specific cytotoxic T lymphocyte (CTL) activity against both variant and original L1210 targets was developed by antigen (L1210) restimulation in the culture of spleen cells from these mice, but was not increased to a detectable level before L1210-K7L- variant started to grow. It was suggested that the 1210-K7L- variant and the original L1210 should have the common tumor-specific antigen that was independent of the K7L-reactive antigen, and that original L1210, whose growth was retarded by K7L, primed the host with the common antigen to be enormously boosted by the subsequently growing L1210-K7L- variant. 相似文献
10.
Effect of orally-administered epidermal growth factor on intestinal iron absorption and mucosal permeability 总被引:1,自引:0,他引:1
A progressive increase in intestinal 59Fe3+ absorption was observed on oral feeding of mice with physiological doses of EGF/UGO. Maximal changes were apparent after 3d and appeared to be dose-dependent. In addition to a small increase in intestinal cell proliferation, as reflected by increased ornithine decarboxylase activity, EGF/UGO-feeding increased mucosal permeability (evaluated with [51Cr]-EDTA): the latter could account for the increase in iron absorption. Sialoadenectomy, to remove the major source of endogenous EGF/UGO, had no appreciable effect on the intestinal absorption of iron. 相似文献