全文获取类型
收费全文 | 3908篇 |
免费 | 286篇 |
出版年
2023年 | 27篇 |
2022年 | 36篇 |
2021年 | 111篇 |
2020年 | 86篇 |
2019年 | 84篇 |
2018年 | 135篇 |
2017年 | 77篇 |
2016年 | 132篇 |
2015年 | 210篇 |
2014年 | 232篇 |
2013年 | 281篇 |
2012年 | 358篇 |
2011年 | 305篇 |
2010年 | 211篇 |
2009年 | 201篇 |
2008年 | 206篇 |
2007年 | 207篇 |
2006年 | 174篇 |
2005年 | 173篇 |
2004年 | 156篇 |
2003年 | 126篇 |
2002年 | 112篇 |
2001年 | 40篇 |
2000年 | 49篇 |
1999年 | 36篇 |
1998年 | 32篇 |
1997年 | 22篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 22篇 |
1993年 | 26篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有4194条查询结果,搜索用时 31 毫秒
991.
Effects of sampling location and time,and host animal on assessment of bacterial diversity and fermentation parameters in the bovine rumen 总被引:1,自引:0,他引:1
M. Li G.B. Penner E. Hernandez‐Sanabria M. Oba L.L. Guan 《Journal of applied microbiology》2009,107(6):1924-1934
Aims: To investigate, using culture‐independent methods, whether the ruminal bacterial structure, population and fermentation parameters differed between sampling locations and time. Methods and Results: The detectable bacteria and fermentation parameters in the digesta from five locations in the rumen of three cows at three time points were analysed. The PCR‐denaturing gradient gel electrophoresis (PCR‐DGGE) profiles were similar among digesta samples from five locations (95·4%) and three time points (93·4%) within cows; however, a lower similarity was observed for samples collected from different host animals (85·5%). Rumen pH and concentration of volatile fatty acids (VFA) were affected by time points of sampling relative to feeding. Conclusions: The detectable bacterial structure in the rumen is highly conserved among different locations and over time, while the quantity of individual bacterial species may change diurnally in response to the feeding. Significance and impact of the study: This study supplies the fundamental understanding of the microbial ecology in the rumen, which is essential for manipulation of ruminal microflora and subsequent improvement in animal production. 相似文献
992.
Raquel Sobrino Pelayo Acevedo Marco A. Escudero Javier Marco Christian Gortázar 《European Journal of Wildlife Research》2009,55(2):161-165
We conducted spotlight counts from 1992 to 2006 in 59 localities to describe carnivore presence, distribution and relative
abundance in open agriculture lands in Aragon, northeastern Spain. During the study period, urban waste and carcases of domestic
livestock became less available to wild animals, and rabbit (Oryctolagus cuniculus) abundance was low after rabbit haemorragic disease. We calculated a kilometric abundance index (KAI, individuals seen per
100 km surveyed) and the ratio between the number of positive localities in which a species was detected and the total of
localities surveyed in a year. Indices to abundance and presence included: red fox (Vulpes vulpes), KAI per 100 km 10.70 and 100.0% localities per year; stray dog (Canis familiaris), KAI 0.48 and 22.6% localities; wildcat (Felis silvestris), KAI 0.10 and 19.1% localities; domestic cat (Felis catus), KAI 0.21 and 20.6% localities; polecat (Mustela putorius), KAI 0.02 and 2.0% localities; badger (Meles meles), KAI 0.16 and 23.6% localities; stone marten (Martes foina), KAI 0.11 and 19.6% localities; weasel (Mustela nivalis), KAI 0.002 and 0.6% localities; and genet (Genetta genetta), KAI 0.06 and 10.0% localities. Indices of badger abundance increased significantly, whereas indices of stray dogs decreased
significantly over the study period. Abundance indices of red fox, the most important predator of small game, were stable
throughout the study period. No significant trend was observed to other studied species. This study concludes that Aragon
region maintains a diverse and rather stable carnivore community and shows that large scale data may help to identify trends
of the more abundant wild and feral carnivores. 相似文献
993.
The proteolysis of cheese whey with the aid of immobilized enzymes is an attractive alternative for this by-product of the
dairy industry. Among some possible applications for whey protein hydrolysates, one may cite their use as protein source for
individuals with reduced capacity of digestion, or with genetic metabolic disorders (phenylketonuria patients, for instance).
The multipurpose plant that processes whey is named here as a cheese whey biorefinery. This work presents the remote control
and monitoring of the whey biorefineries using the Internet. In an integrated environment, the web application also enables
simulation and economic analyses of the process. This technology might allow small companies to access a remote “engineering
centre”, with know-how on plant design and advanced control techniques. The idea can also be extended to large dairy companies,
providing the remote control of geographically spread sites of production. 相似文献
994.
995.
996.
Angel Montero Ovidio Hernando Veronica Caon Diana Guevara Jeannete Valero Xin Chen-Zhao Paz Garcia-Acilu Emilio Sanchez Mercedes Lopez Raquel Ciervide Mariola Garcia-Aranda Beatriz Alvarez Alejandro Prado Rosa Alonso Pedro Fernandez-Leton Carmen Rubio 《Reports of Practical Oncology and Radiotherapy》2021,26(4):605
BackgroundAbout 5% of prostate cancer cases are metastatic at diagnoses. Radiotherapy of both primary tumor and secondary lesions can be, in addition to systemic treatments, a radical alternative for selected patients.Materials and methodsPatients with de novo prostate carcinoma with bone or lymph node metastases were retrospectively reviewed. All patients received moderate hypofractionated IMRT/VMAT up to 63 Gy in 21 daily fractions of 3 Gy to prostate and metastases with neoadjuvant and concurrent androgen deprivation therapy (ADT). According to known advances some patients also received abiraterone, enzalutamide, or docetaxel.ResultsBetween 2015–2020, we attended 26 prostate cancer patients (median age 69.5 years, range 52–84) with simultaneous oligometastases [mean 2.1 metastases, median 1.5 metastases (range 1–6)]. Eighteen patients (69%) presented lymph node metastases, 4 (15.5%) bone metastases and 4 (15.5%) both lymph node and bone metastases. With a median follow-up of 15.5 months (range 3–65 months), 16 patients (62%) are alive and tumor free while 10 (38%) are alive with tumor. Four patients (17%) developed tumor progression, out of irradiated area in all cases, with a median time to progression of 43.5 months (range 27–56 months). Actuarial progression-free survival (PFS) rates at 12 and 24 months were 94.1% and 84.7%, respectively. No grade > 2 acute or late complications were recorded.ConclusionsSimultaneous directed radical hypofractionated radiation therapy for prostate and metastases is feasible, well tolerated and achieves an acceptable PFS rate. However, further studies with longer follow-up are necessary to definitively address these observations. 相似文献
997.
Susana M. Ortigosa Pedro Díaz-Vivancos María José Clemente-Moreno Marta Pintó-Marijuan Isabel Fleck Jon Veramendi Mireya Santos José Antonio Hernandez José M. Torné 《Planta》2010,232(3):593-605
As part of a project aiming to characterize the role of maize plastidial transglutaminase (chlTGZ) in the plant chloroplast,
this paper presents results on stress induced by continuous chlTGZ over-expression in transplastomic tobacco leaves. Thylakoid
remodelling induced by chlTGZ over-expression in young leaves of tobacco chloroplasts has already been reported (Ioannidis
et al. in Biochem Biophys Acta 1787:1215–1222, 2009). In the present work, we determined the induced alterations in the photosynthetic apparatus, in the chloroplast ultrastructure,
and, particularly, the activation of oxidative and antioxidative metabolism pathways, regarding ageing and functionality of
the tobacco transformed plants. The results revealed that photochemistry impairment and oxidative stress increased with transplastomic
leaf age. The decrease in pigment levels in the transformed leaves was accompanied by an increase in H2O2 and lipid peroxidation. The rise in H2O2 correlated with a decrease in catalase activity, whereas there was an increase in peroxidase activity. In addition, chlTGZ
over-expression lead to a drop in reduced glutathione, while Fe-superoxide dismutase activity was higher in transformed than
in wild-type leaves. Together with the induced oxidative stress, the over-expressed chlTGZ protein accumulated progressively
in chloroplast inclusion bodies. These traits were accompanied by thylakoid scattering, membrane degradation and reduction
of thylakoid interconnections. Consequently, the electron transport between photosystems decrease in the old leaves. In spite
of these alterations, transplastomic plants can be maintained and reproduced in vitro. These results are discussed in line
with chlTGZ involvement in chloroplast functionality. 相似文献
998.
999.
Raquel Lüdtke Gustavo Agostini Silvia T. Sfoggia Miotto Tatiana T. Souza-Chies 《Plant Molecular Biology Reporter》2010,28(2):317-323
The genus Polygala is one of the seven Polygalaceae genera that occur in the Brazilian flora, covering approximately 110 species. During the
taxonomic review of Polygalaceae in Southern Brazil, difficulties were found when classifying species with very similar morphology,
and morphological data alone could not clarify these interspecific relationships. In this context, inter-simple sequence repeat
(ISSR) molecular markers were used in an attempt to characterize the genetic diversity and relationships among Polygala species. Nine Polygala species were analyzed using six selected ISSR primers that generated a total of 75 bands (100% polymorphic). The relationships
were evaluated by dendrograms using the unweighted pair group method using arithmetic averages algorithm. The use of ISSR
to solve the taxonomic problems was very useful for the Brazilian Polygala species. This is the first report of a molecular characterization of the Brazilian Polygala species to successfully group the different species. The ISSR results are in agreement with the morphological evidence of
a new Polygala species from Southern Brazil. 相似文献
1000.
Michele M. Castro Elen Rizzi Cibele M. Prado Marcos A. Rossi Jose E. Tanus-Santos Raquel Fernanda Gerlach 《Matrix biology》2010,29(3):194-201
Structural vascular changes in two-kidney, one-clip (2K-1C) hypertension may result from increased matrix metalloproteinase (MMP)-2 activity. MMP-2 activation is regulated by other MMPs, including transmembrane-MMPs, and by tissue inhibitors of MMPs (TIMPs). We have investigated the localization of MMP-2, -9, -14, and TIMPs 1–4 in hypertensive aortas and measured their levels by zymography/Western blotting and immunohistochemistry. Gelatinolytic activity was assayed in tissues by in situ zymography. Sham-operated and 2K-1C hypertensive rats were treated with doxycycline (or vehicle) for 8 weeks, and the systolic blood pressure was monitored weekly. Doxycycline attenuated 2K-1C hypertension (165 ± 11.7 mmHg versus 213 ± 7.9 mm Hg in hypertensive controls, P < 0.01), and completely prevented increase in the thicknesses of the media and the intima in 2K-1C animals (P < 0.01). Increased amounts of MMP-2, -9, and -14 were found in hypertensive aortas, as well as enhanced gelatinolytic activity. A gradient in the localization of MMP-2, -9, and -14 was found, with increased amounts detected in the intima, at sites with higher gelatinolytic activity. Doxycycline attenuated hypertension induced increases in all the 3 investigated MMPs in both the media and the intima (all P < 0.05), but it did not change the amounts of TIMPs 1–4 (P > 0.05). Therefore, an imbalance between increased amounts of MMPs at the tissue level without a corresponding increase in the quantities of TIMPs, particularly in the intima and inner media layers, appears to account for the increased proteolytic activity found in 2K-1C hypertension-induced maladaptive vascular remodeling. 相似文献