首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   126篇
  免费   4篇
林业   5篇
农学   7篇
  5篇
综合类   25篇
农作物   1篇
水产渔业   33篇
畜牧兽医   52篇
植物保护   2篇
  2021年   3篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2017年   2篇
  2016年   8篇
  2015年   4篇
  2014年   2篇
  2013年   7篇
  2012年   13篇
  2011年   8篇
  2010年   1篇
  2008年   2篇
  2007年   2篇
  2006年   5篇
  2005年   7篇
  2004年   8篇
  2003年   2篇
  2002年   2篇
  2001年   9篇
  2000年   5篇
  1999年   7篇
  1998年   1篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   5篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
  1969年   2篇
排序方式: 共有130条查询结果,搜索用时 31 毫秒
91.
The satellite images of volcanic clouds in Kyushu, Japan during September–November 1989 were studied in connection with the mountain site measurement of atmospheric qualities at Unzen-Nodake and the SO2 concentration data at Aso Volcano Museum. The images strongly indicate that many high concentration events of SO2 were the results of the long-range transport of volcanic gas from Mt. Aso and Mt. Sakurajima to these stations. Brief comments on the 2000 eruption of Miyake-jima volcano are added.  相似文献   
92.
93.
The assessment of thyroid volume plays an indispensable role in the diagnosis and management of different thyroid diseases. The present study evaluates the accuracy of dolphin thyroid volume measurement as determined by four two-dimensional (2D) ultrasound methods (A-D), with a standard of reference using three-dimensional (3D) ultrasound. The measurement accuracy for different recognized thyroid configuration is also evaluated. Inter- and intraoperator variability of the measurement methods was determined. Thyroid ultrasound examinations were conducted in 16 apparently healthy Indo-Pacific bottlenose dolphins (Tursiops aduncus) with 2D and 3D ultrasound under identical scanning conditions. All 2D ultrasound measurement methods yielded high accuracies (79.9-81.3%) when compared with the 3D ultrasound measurement, and had high measurement reproducibility (77.6-86.2%) and repeatability (78.1-99.7%). For 2D ultrasound measurements, Methods A and B were more accurate and reliable than Methods C and D, regardless of thyroid configuration. Ultrasound is useful in the measurement of thyroid volume in bottlenose dolphins. For the first time, a reliable ultrasound scanning protocol for measuring dolphin thyroid volume was developed, which provides a means to establish a normative reference for the diagnosis of thyroid pathologies and to monitor the thyroid volume during the course of treatment in living dolphins. Key words: 3D ultrasound, Indo-Pacific bottlenose dolphin, thyroid volume measurement, Tursiops aduncus.  相似文献   
94.
The extinct p-process nuclide (146)Sm serves as an astrophysical and geochemical chronometer through measurements of isotopic anomalies of its α-decay daughter (142)Nd. Based on analyses of (146)Sm/(147)Sm α-activity and atom ratios, we determined the half-life of (146)Sm to be 68 ± 7 (1σ) million years, which is shorter than the currently used value of 103 ± 5 million years. This half-life value implies a higher initial (146)Sm abundance in the early solar system, ((146)Sm/(144)Sm)(0) = 0.0094 ± 0.0005 (2σ), than previously estimated. Terrestrial, lunar, and martian planetary silicate mantle differentiation events dated with (146)Sm-(142)Nd converge to a shorter time span and in general to earlier times, due to the combined effect of the new (146)Sm half-life and ((146)Sm/(144)Sm)(0) values.  相似文献   
95.
Previous studies have suggested the presence of a glucose-sensing mechanism in the hindbrain that appears to regulate reproductive function as well as feeding behavior. The ependymocytes lining the ventricular wall of the hindbrain showed immunoreactivities to pancreatic glucokinase (GK), a key enzyme for glucose sensing in pancreatic B cells. Our goal in the present study was to test whether the GK-immunopositive ependymocytes in the wall of the fourth cerebroventricle (4V) play a role in regulating gonadal activity. Our approach was to determine the effect of injecting alloxan, a GK inhibitor, into the 4V on pulsatile luteinizing hormone (LH) secretion. Estrogen-primed ovariectomized rats received an injection of alloxan (10 or 20 microg/animal) into the 4V and blood samples were collected every 6 min for 3 h for measurement of blood LH, corticosterone and glucose levels. Pulsatile LH secretion was suppressed after alloxan injection and all pulse parameters were significantly (P<0.05) inhibited by 20 microg alloxan. Plasma corticosterone levels were increased significantly (P<0.05) by 20 microg alloxan, suggesting that LH pulse suppression by alloxan may be at least partly mediated by activation of the hypothalamo-pituitary-adrenal axis. The present results suggest that acute suppression of GK activity in the hindbrain inhibits pulsatile LH secretion in female rats, and supports the idea that GK-immunopositive ependymocytes may sense glucose levels in the cerebrospinal fluid and play a role in regulation of LH secretion.  相似文献   
96.
Because heavy metals cause various health hazards, we studied biosorption by Weissella viridescens MYU 205. MYU 205 showed high biosorption for Cd (II) and Hg (II) and was low for Zn (II). The Hg (II) biosorption rate was high at about 80%. Different biosorptions were shown for each metal after successive incubation. About 20% of the Zn (II) biosorption was observed after 3 h. Cd (II) biosorption increased in a time‐dependent manner until 3 h, then gradually decreased. Hg (II) was immediately sorbed at 79.6 ± 4.7% and decreased at 3 h to 52.9 ± 2.6%, and then gradually increased to 77.8 ± 3.6%. Using heat‐killed cells, the rate of biosorption of Zn (II) and Cd (II) decreased whereas Hg (II) tended to increase. The metal resistance was high, that is Zn (II) > Cd (II) > Hg (II); while the affinity was opposite where MYU 205 showed high affinity to Hg (II) and low affinity to Zn (II). Our data shows lactic acid bacteria may be powerful heavy metal sorbents for detoxification.  相似文献   
97.
Acute central lipoprivation suppresses pulsatile luteinizing hormone (LH) release and increases blood glucose levels through noradrenergic input to the hypothalamic paraventricular nucleus (PVN) in female rats. The present study was conducted to identify adrenergic receptor subtypes involved in central lipoprivation-induced suppression of pulsatile LH secretion and increases in plasma glucose levels in female rats. Acute hindbrain lipoprivation was produced by injection into the fourth cerebroventricle (4V) of 2-mercaptoacetate (MA), an inhibitor of fatty acid oxidation, in estradiol-implanted ovariectomized rats. Two min before MA injection, alpha1-, alpha2- or beta-adrenergic receptor antagonist was injected into the PVN. Injection of MA into the 4V suppresses pulsatile LH release in PVN vehicle-treated rats, whereas pretreatment of animals with injection of alpha1- or alpha2-adrenergic antagonist into the PVN blocked the effect of the 4V MA injection on LH pulses. beta-Adrenergic antagonist did not affect MA-induced suppression of LH pulses. The counter-regulatory increase in plasma glucose levels after 4V MA injection was also partially blocked by pretreatment with alpha1- and alpha2-adrenergic receptor antagonists. These results suggest that alpha1- and alpha2-adrenergic receptors in the PVN mediate hindbrain lipoprivation-induced suppression of LH release and counter-regulatory increases in plasma glucose levels in female rats.  相似文献   
98.
Metastin/kisspeptin, the KiSS-1 gene product, has been identified as an endogenous ligand of GPR54 that reportedly regulates GnRH/LH surges and estrous cyclicity in female rats. The aim of the present study was to determine if metastin/kisspeptin neurons are a target of estrogen positive feedback to induce GnRH/LH surges. We demonstrated that preoptic area (POA) infusion of the anti-rat metastin/kisspeptin monoclonal antibody blocked the estrogen-induced LH surge, indicating that endogenous metastin/kisspeptin released around the POA mediates the estrogen positive feedback effect on GnRH/LH release. Metastin/kisspeptin neurons in the anteroventral periventricular nucleus (AVPV) may be responsible for mediating the feedback effect because the percentage of c-Fos-expressing KiSS-1 mRNA-positive cells to total KiSS-1 mRNA-positive cells was significantly higher in the afternoon than in the morning in the anteroventral periventricular nucleus (AVPV) of high estradiol (E(2))-treated females. The percentage of c-Fos-expressing metastin/kisspeptin neurons was not different between the afternoon and morning in the arcuate nucleus (ARC). Most of the KiSS-1 mRNA expressing cells contain ERalpha immunoreactivity in the AVPV and ARC. In addition, AVPV KiSS-1 mRNA expressions were highest in the proestrous afternoon and lowest in the diestrus 1 in females and were increased by estrogen treatment in ovariectomized animals. On the other hand, the ARC KiSS-1 mRNA expressions were highest at diestrus 2 and lowest at proestrous afternoon and were increased by ovariectomy and decreased by high estrogen treatment. Males lacking the surge mode of GnRH/LH release showed no obvious cluster of metastin/kisspeptin-immunoreactive neurons in the AVPV when compared with high E(2)-treated females, which showed a much greater density of these neurons. Taken together, the present study demonstrates that the AVPV metastin/kisspeptin neurons are a target of estrogen positive feedback to induce GnRH/LH surges in female rats.  相似文献   
99.
本文是通过在城市不同环境、不同季节少年儿童学习、生活娱乐的初步调查后,得出的结论.必须在城市改建规划中,挖掘城市用地的潜力,为少年儿童提供足够数量的游戏场.我们对四个街区儿童游戏空间进行分析得出的一些有趣的资料,应引起专家们的关注  相似文献   
100.
ICR-derived strain with glomerulonephritis (ICGN) is a strain of mice with hereditary nephrotic syndrome with an unidentified cause. Based on histopathological and biochemical data, ICGN mice are considered to be a good experimental model for human idiopathic nephrotic syndrome. In the present study, we histochemically investigated the changes in localization of extracellular matrix (ECM) components and transforming growth factor beta1 (TGF-beta1). Strong immunohistochemical staining of basal membrane ECM components (collagen IV and laminin) and interstitial ECM components (type III collagen and fibronectin) were demonstrated in glomeruli and tubulointerstitum of ICGN mice as compared with those of sex and age-matched ICR mice, used as normal healthy controls. Marked type I collagen and tenascin deposition, which were not detected in the glomeruli of ICR mice, were seen in the glomeruli of ICGN mice. A remarkable increase in active-TGF-beta1 was also detected only in glomeruli of ICGN mice, but not in those of ICR mice. Furthermore, strikingly increased alpha-smooth muscle actin, a marker of activated glomerular mesangial cells, was demonstrated in the glomeruli, mainly in the mesangial cells, of ICGN mice. These findings indicated that ECM components are increased in the glomerulus and tubulointerstitum of ICGN mice, and that active-TGF-beta1 induces such increases in ECM components. The present findings may contribute to elucidation of the pathogenic mechanisms of hereditary nephrotic syndrome in ICGN mice and, in future, human idiopathic nephrotic syndrome.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号