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   1248篇
  免费   38篇
  国内免费   4篇
林业   66篇
农学   25篇
基础科学   18篇
  243篇
综合类   159篇
农作物   61篇
水产渔业   95篇
畜牧兽医   482篇
园艺   37篇
植物保护   104篇
  2024年   4篇
  2023年   6篇
  2022年   12篇
  2021年   15篇
  2020年   20篇
  2019年   27篇
  2018年   23篇
  2017年   15篇
  2016年   14篇
  2015年   21篇
  2014年   18篇
  2013年   60篇
  2012年   72篇
  2011年   87篇
  2010年   62篇
  2009年   56篇
  2008年   80篇
  2007年   81篇
  2006年   86篇
  2005年   69篇
  2004年   72篇
  2003年   79篇
  2002年   85篇
  2001年   13篇
  2000年   13篇
  1999年   13篇
  1998年   16篇
  1997年   11篇
  1996年   12篇
  1995年   10篇
  1994年   9篇
  1993年   10篇
  1992年   5篇
  1991年   7篇
  1990年   4篇
  1989年   6篇
  1988年   10篇
  1987年   9篇
  1986年   11篇
  1985年   11篇
  1984年   9篇
  1983年   10篇
  1982年   6篇
  1980年   7篇
  1978年   4篇
  1976年   2篇
  1975年   6篇
  1974年   3篇
  1973年   2篇
  1967年   2篇
排序方式: 共有1290条查询结果,搜索用时 15 毫秒
61.
Umbilical hernias were diagnosed in two captive-born, female Asian elephant (Elephas maximus) calves several weeks after birth. Daily manual reduction of the hernias for 5 wk in the first case and for 5 mo in the second resulted in complete closure of the defects. Nonsurgical repair of uncomplicated, fully reducible umbilical hernias in Asian elephants can be an alternative to surgery.  相似文献   
62.
OBJECTIVE: To evaluate the cytopathic effects of Tritrichomonas foetus and a purified cysteine protease (ie, CP30) of T foetus on cultured bovine uterine epithelial cells (BUECs) in vitro. SAMPLE POPULATION: 10 reproductive tracts were obtained from late-term bovine fetuses at a commercial abattoir. PROCEDURE: An in vitro culture system of BUECs was developed to study the cytopathic effects of T foetus and purified CP30 of T foetus on host cells. Cytotoxicity of T foetus or CP30 on exposed BUECs was determined. Fluorescence microscopy and flow cytometry analyses were used to detect apoptosis. A fluorometric assay was used to detect BUEC caspase 3 activation. The CP inhibitor E-64 and a caspase inhibitor were used to inhibit apoptosis. RESULTS: Cytopathic effects were observed in BUECs treated with parasites or CP30 and were concentration and time dependent. The BUECs underwent apoptosis in the presence of parasites or CP30. The specific CP inhibitor E-64 abolished the induction of apoptosis in BUECs by CP30. The caspase inhibitor reduced the amount of apoptosis in BUECs. CONCLUSIONS AND CLINICAL RELEVANCE: T foetus and its CP30 induce apoptosis in cultured BUECs in vitro. Induction of apoptosis by CP30 is correlated with protease activity. Endometrial cell death as a result of a T foetus infection is likely to be more important in mediating infertility than a direct effect on the conceptus. Provoking an apoptotic reaction in the host may mitigate an inflammatory reaction or immune response and therefore favor survival of the parasite in a chronic infection.  相似文献   
63.
This paper provides a working framework for enhancing the well-being of senior pet dogs and cats. Approaches to screening the medical status of senior pets are described in detail, with particular emphasis on establishing baseline data in healthy animals, the testing of clinically ill animals, and assessing senior pets prior to anesthesia and surgery. The management of pain and distress and the application of hospice and palliative care are addressed. Advice on ways to approach euthanasia and dealing with end-of-life issues is also provided.  相似文献   
64.
In the voluminous literature on the subject of bGH we have yet to find an attempt to frame the issue in specifically moral terms or to address systematically its ethical implications. I argue that there are two moral objections to the technology: its treatment of animals, and its dislocating effects on farmers. There are agricultural biotechnologies that deserve funding and support. bGH is not one of them.  相似文献   
65.
An economic analysis of tray cultured oysters in Dongonab Bay, Red Sea was conducted based on production costs collected by the Red Sea Fisheries Research Centre. The analysis showed that oflbottom oyster farming was economically attractive at a price around 1.5 Sudanese pounds (US $0.75) per kilogram of shell and discount rates of 40% or less.  相似文献   
66.
Decapsulation of Artemia spp. cysts in strong hypochlorite solutions reportedly increases the number of nauplii that hatch. Commercial cysts of Artemia franciscano were subjected to four decapsulation methods prior to hatching them in aerated seawater. Samples were removed from the hatch vessels every 5 h from 15 through 45 h, and fully hatched nauplii were counted. The experiment was performed three times. No significant difference was seen between mean numbers of control nauplii and nauplii obtained using the decapsulation method that yielded the best hatch: oxidation for 15 min in equal parts Clorox® and seawater plus 6 mL of a 40% NaOH solution, followed by reduction with 100 mL of 0.7 M sodium thiosulfate. A third treatment was inferior to either of these, and two others produced very low yields. It was concluded that of the methods evaluated, none is superior to no treatment at all, and some are clearly detrimental to developing Artemia embryos.  相似文献   
67.
68.
Thunderstorm simulation in the laboratory setting induces fearful and anxious behavior in beagles, most notably manifested by increased inactivity (“freezing”), which, in a companion study, was ameliorated by the anxiolytic diazepam (Araujo et al., 2009). Using this protocol, the present study assessed the efficacy of Harmonease, a chewable oral anxiolytic botanical product containing a proprietary blend of extracts of Magnolia officinalis and Phellodendron amurense. A balanced, placebo-controlled, blinded, single crossover design including 20 healthy adult beagles was used for this study. After a baseline thunderstorm test, subjects received Harmonease Chewable Tablets or placebo treatment daily and were reassessed on the treatment day 7. After a 7-day washout period, the treatments were crossed over and a design identical to that used in the first phase was used. The thunderstorm test was performed in an open-field arena (8 ft × 9 ft) and consisted of three 3-minute phases: an anticipatory phase in which no stimulus was provided; the thunderstorm phase in which a thunderstorm track was played over a speaker system; and a recovery phase in which no stimulus was presented. Inactivity duration was considered the primary variable for assessing efficacy which was measured by a trained observer. Difference in number of dogs improved versus worsened by treatment group was significant at P < 0.05. Specifically, 12 of 20 (60%) dogs improved from baseline when treated with Harmonease, whereas only 5 of 20 (25%) improved on placebo. Furthermore, 9 of 20 (45%) placebo dogs showed increased inactivity duration (worsened), whereas only 4 of 20 (20%) treatment dogs worsened. Increases in distance travelled consistent with reduced inactivity were also seen under Harmonease. Harmonease reduced fear-related inactivity or freezing in dogs in this thunderstorm simulation model. This supports past studies demonstrating that the combination of botanical extracts in Harmonease is effective in dogs for the management of stress-related behaviors.  相似文献   
69.
70.
OBJECTIVE: To determine whether alterations in myoplasmic calcium regulation can be identified in muscle cell cultures (myotubes) and intact muscle fiber bundles derived from Thoroughbreds affected with recurrent exertional rhabdomyolysis (RER). ANIMALS: 6 related Thoroughbreds with RER and 8 clinically normal (control) Thoroughbred or crossbred horses. PROCEDURES: Myotube cell cultures were grown from satellite cells obtained from muscle biopsy specimens of RER-affected and control horses. Fura-2 fluorescence was used to measure resting myoplasmic calcium concentration as well as caffeine- and 4-chloro-m-cresol (4-CMC)-induced increases in myoplasmic calcium. In addition, intact intercostal muscle fiber bundles were prepared from both types of horses, and their sensitivities to caffeine- and 4-CMC-induced contractures were determined. RESULTS: Myotubes of RER-affected and control horses had identical resting myoplasmic calcium concentrations. Myotubes from RER-affected horses had significantly higher myoplasmic calcium concentrations than myotubes from control horses following the addition of > or = 2mM caffeine; however, there was no difference in their response to 4-CMC (> or = 1 mM). Caffeine contracture thresholds for RER and control intact muscle cell bundles (2 vs 10mM, respectively) were significantly different, but 4-CMC contracture thresholds of muscle bundles from RER-affected and control horses (500 microM) did not differ. CONCLUSIONS AND CLINICAL RELEVANCE: An increase in caffeine sensitivity of muscle cells derived from a family of related RER-affected horses was detected in vitro by use of cell culture with calcium imaging and by use of fiber bundle contractility techniques. An alteration in muscle cell calcium regulation is a primary factor in the cause of this heritable myopathy.  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