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   857篇
  免费   50篇
  国内免费   1篇
林业   56篇
农学   39篇
基础科学   1篇
  126篇
综合类   73篇
农作物   49篇
水产渔业   105篇
畜牧兽医   407篇
园艺   11篇
植物保护   41篇
  2023年   2篇
  2022年   10篇
  2021年   10篇
  2020年   7篇
  2019年   22篇
  2018年   17篇
  2017年   18篇
  2016年   23篇
  2015年   20篇
  2014年   19篇
  2013年   41篇
  2012年   45篇
  2011年   64篇
  2010年   29篇
  2009年   23篇
  2008年   42篇
  2007年   43篇
  2006年   51篇
  2005年   38篇
  2004年   37篇
  2003年   41篇
  2002年   36篇
  2001年   32篇
  2000年   40篇
  1999年   31篇
  1998年   7篇
  1997年   9篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1992年   15篇
  1991年   9篇
  1990年   15篇
  1989年   16篇
  1988年   15篇
  1987年   12篇
  1986年   7篇
  1985年   10篇
  1984年   4篇
  1983年   3篇
  1982年   2篇
  1981年   4篇
  1980年   3篇
  1979年   4篇
  1976年   5篇
  1975年   2篇
  1973年   3篇
  1972年   2篇
  1971年   2篇
  1970年   5篇
排序方式: 共有908条查询结果,搜索用时 31 毫秒
771.
Muscle damage induces massive macrophage infiltration of the injury site, in which activated pro‐inflammatory and anti‐inflammatory phenotypes (currently classified as M1 and M2, respectively) have been documented as distinct functional populations predominant at different times after the conventional acute injury by intramuscular injection of snake venoms (cardiotoxin, notexin) or chemicals (bupivacaine hydrochloride, barium chloride). The present study employed a muscle‐crush injury model that may better reflect the physiologic damage and repair processes initiated by contusing a gastrocnemius muscle in the lower hind‐limb of adult mice with hemostat forceps, and examined the time‐course invasion of M1 and M2 macrophages during muscle regeneration by immunocytochemistry of CD197 and CD206 marker proteins. CD197‐positive M1 macrophages were observed exclusively at 1–4 days after crush followed by the alternative prevalence of CD206‐positive M2 at 7 days of myogenic differentiation, characterized by increasing levels of myogenin messenger RNA expression. Preliminary PCR analysis showed that M2 may produce hepatocyte growth factor (HGF) in culture, providing additional benefit to understanding that M2 populations actively promote regenerative myogenesis (muscle fiber repair) and moto‐neuritogenesis (re‐attachment of motoneuron terminals onto damaged fibers) through their time‐specific infiltration and release of growth factor at the injury site early in muscle regeneration.  相似文献   
772.
In rats, it is sometimes difficult to distinguish malignant reticuloses from astrocytomas in routine histopathological assessment. In the present study, four spontaneous brain neoplasms developing in the cerebrum of one Wistar Hannover rat and three Sprague-Dawley rats were immunohistochemically examined using microglia and macrophage markers. Histopathologically, these neoplasms were localized mainly in the cerebral cortex, hypothalamus or piriform lobe, and the portions showing solid growth did not show characteristic cellular arrangement but had an indistinct boundary with the surrounding brain parenchyma. Neoplastic cells had oval or pleomorphic small nuclei with abundant eosinophilic cytoplasm. Two cases showed neoplastic cell infiltration into the meninges and perivascular spaces. Silver staining showed lack of reticulin fiber production in the stroma of the neoplasms. Immunohistochemically, the neoplastic cells were strongly positive for Iba-1 and sporadically positive for CD68 in all four cases. On the basis of these results, all the neoplasms examined here could be distinguished from astrocytomas and diagnosed as malignant reticuloses. Thus, immunohistochemical demonstration of microglia/macrophage characters, such as using Iba-1, is considered to be helpful for differential diagnosis of malignant reticuloses from astrocytomas among spontaneously occurring primary brain neoplasms in rats.  相似文献   
773.
We investigate the effect of climate change on water resources as snow storage (WRSS) using a regional climate model with a 20-km mesh (MRI-RCM20), in the Tedori River basin of Japan. We make four main predictions. First, annual average temperature in Kanazawa is predicted to increase by 2.7 °C by 2081–2100, compared to the period 1981–2000. The smallest predicted temperature difference is 1.1 °C in August, and the largest is 3.4 °C in April and December. The annual average temperature is predicted to change from 14.5 to 17.2 °C. Second, annual average precipitation is predicted to increase by 3.8 %, and precipitation during the snowfall season (December–February) is predicted to decrease by 13.2 %, as a result of increasing temperatures. Third, average WRSS for the period 2001–2100 is predicted by degree-day and tank model analyses. Both the analyses show very similar results. The degree-day analysis shows 200 mm of average WRSS in 2100, and 477 mm in 2050. These values constitute 26 and 63 % of the WRSS value in 2000 (754 mm). The tank model analysis shows WRSS of 260 mm in 2100 and 523 mm in 2050, which are 33 and 67 % of the WRSS (785 mm) in 2000, respectively. Fourth, to examine the effect on irrigation water especially on the paddy paddling period, discharge is predicted and considered under the predicted average WRSS is 520 mm in 2050, 258 mm in 2100, and reaches a minimum of 41 mm in 2100.  相似文献   
774.
A 10‐year‐old neutered female soft‐coated wheaten terrier and a 10‐year‐old, entire female Pomeranian were presented for vomiting and anorexia. Using ultrasound, an oval structure with a stellate, kiwifruit‐like appearance typical of a gall bladder mucocoele was observed in the caudal abdomen of the soft‐coated wheaten terrier and adjacent to the liver in the Pomeranian. There was also a moderate volume of abdominal effusion in both dogs. Cytology of the peritoneal fluid indicated a sterile exudative process but varied between the two dogs, with an absence of bile pigment in the soft‐coated wheaten terrier and marked bile peritonitis in the Pomeranian. An entire free‐floating ectopic mucocoele was confirmed via exploratory laparotomy with concomitant gall bladder rupture and common bile duct obstruction. Both dogs recovered completely after surgery. This is the first report of cases of gall bladder rupture with entire free‐floating gall bladder mucocoeles in dogs.  相似文献   
775.
776.
Decreased fertility associated with maternal ageing is a well‐known critical problem, and progesterone (P4) concentration decreases during the menopause transition in women. The corpus luteum (CL) secretes P4, thereby supporting the implantation and maintenance of pregnancy. It is proposed that a bovine model is suitable for studying age‐associated decline of fertility in women because the physiology of cows is similar to that of women and cows have a greater longevity compared with other animal models. Thus, we investigated the age‐dependent qualitative changes and inflammatory responses in the bovine CL. In vivo experiment: Cows were divided into three groups, namely, young (mean age: 34.8 months), middle (80.1 months) and aged (188.9 months). Blood samples were collected on days 7 and 12 during the estrous cycle. In vitro experiments: Cows were divided into young (mean age: 27.6 months) and aged (183.1 months). The CL tissues of these groups were collected from a local slaughterhouse and used for tissue culture experiments. An in vivo experiment, plasma P4 concentration in aged cows was significantly lower than that in young cows, whereas no difference was found regarding the area of CL. An in vitro examination in the bovine CL tissues showed that the luteal P4 concentration, P4 secretion, and mRNA expression of StAR and 3β‐HSD were lower in aged cows compared with young cows, especially in the early luteal phase. However, no differences were detected in the mRNA expression of inflammation‐ and senescence‐related factors and inflammatory responses to lipopolysaccharides between the CL tissues from young and aged cows, indicating that an age‐dependent increase in inflammation is not involved in the luteal function. P4 production and secretion from the bovine CL diminish in old cows, especially during the early luteal phase, suggesting that senescence may affect the luteal function in cows.  相似文献   
777.
This study was conducted to determine if dietary supplementation with coenzyme Q10 (CoQ10), which can act as a potent antioxidant and is an obligatory cofactor of mitochondrial uncoupling protein, suppresses the heat stress (HS)‐induced overproduction of mitochondrial reactive oxygen species (ROS) and oxidative damage in the skeletal muscle of birds. The carbonyl protein content of skeletal muscle was significantly higher in birds exposed to HS treatment (34°C, 12 h) than in thermoneutral birds (25°C). This increase was suppressed by CoQ10 supplementation (40 mg/kg diet). Succinate‐supported mitochondrial ROS production was increased by HS treatment, and this increase was also suppressed by CoQ10 supplementation. In contrast, CoQ10 supplementation did not affect the HS‐induced decrease in mitochondrial proton leak. The mitochondrial membrane potential (ΔΨ), to which HS‐induced ROS production was previously shown to be sensitive, tended to be increased by HS treatment, but this rise in ΔΨ was not affected by CoQ10 supplementation. Taken together, these results suggest that dietary CoQ10 supplementation attenuates HS‐induced oxidative damage to skeletal muscle, by preventing the overproduction of succinate‐supported mitochondrial ROS in a manner that is independent of ΔΨ. © 2015 Japanese Society of Animal Science  相似文献   
778.
779.
The frequency of the Glu-D1f allele in Japanese, Chinese, and other Asian hexaploid wheat varieties was analyzed in order to investigate a possible transmission route for hexaploid wheat to the Far East, Japan. The 1380 published data sets were compared to the results for 1107 hexaploid Asian wheat varieties which were determined in this study. The frequency of the Glu-D1f allele was clearly different between areas; the allele was present from northern and southern Japan, from Xinjiang, Jiangsu, Zhejiang, and Beijing in China, and from Afghanistan. A high frequency of the high-molecular-weight glutenin Glu-D1f allele was found predominantly in southern Japan. This distribution of an adaptively neutral character suggests a specific route of transmission for hexaploid wheat to eastern China and the Far East, Japan. It was introduced from Afghanistan, carried to Xinjiang (in northwest China), Jiangsu, and Zhejiang (in southeast China), and then to southern Japan along the so-called Silk Road. It is believed that cultivated hexaploid wheat originated in the Middle East and the Near East and was carried along the Silk Road through China to the Far East, Japan. Japan is the most geographically remote region of wheat production in the world. During the course of its long journey and its adaptation to diverse local environments, Japanese hexaploid wheat has developed a unique composition of glutenin Glu-D1 alleles. The frequency of this allele in different wheat varieties allowed us to hypothesize a possible route for the transmission of hexaploid wheat into the Far East, Japan.  相似文献   
780.
All eight C6-aliphatic alcohol and aldehyde compounds in naturally occurring green leaves showed bacteriostatic effects against Staphylococcus aureus IFO 12732, methicillin-resistant S. aureus, Escherichia coli IFO 3301, E. coli O157:H7, and Salmonella enteritidis, with bacteriostatic activities of less than 12.5 microg mL(-1). In this study, the susceptibility of Gram-positive bacteria tested was observed to be greater than that of Gram-negative bacteria. The bactericidal action of the aldehyde compounds was found to be much stronger than that of the alcohol compounds under both liquid and gaseous conditions. The most effective compound was (3E)-hexenal at concentrations of 0.1 and 1 microg mL(-1), which killed 2.1 x 10(5) cfu mL(-1) of S. aureus IFO 12732 and 1.4 x 10(5) cfu mL(-1) of E. coli IFO 3301, respectively, by direct contact with the compound. Lethality of (3E)-hexenal against S. aureus IFO 12732 and E. coli IFO 3301 was also observed as a result of gaseous contact at concentrations of 3 and 30 microg mL(-1), respectively. The bactericidal effects of 30 microg mL(-1) (3E)-hexenal were thoroughly maintained throughout periods of 2 days and 1 day against S. aureus IFO 12732 and E. coli IFO 3301, respectively, by a complex formation with alpha-cyclodextrin.  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