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   864篇
  免费   44篇
  国内免费   2篇
林业   31篇
农学   39篇
基础科学   5篇
  143篇
综合类   113篇
农作物   49篇
水产渔业   33篇
畜牧兽医   425篇
园艺   15篇
植物保护   57篇
  2023年   5篇
  2022年   5篇
  2021年   16篇
  2020年   21篇
  2019年   21篇
  2018年   16篇
  2017年   20篇
  2016年   14篇
  2015年   11篇
  2014年   12篇
  2013年   37篇
  2012年   35篇
  2011年   41篇
  2010年   37篇
  2009年   17篇
  2008年   36篇
  2007年   42篇
  2006年   40篇
  2005年   43篇
  2004年   33篇
  2003年   39篇
  2002年   52篇
  2001年   18篇
  2000年   19篇
  1999年   21篇
  1998年   11篇
  1997年   11篇
  1996年   5篇
  1995年   11篇
  1994年   7篇
  1992年   12篇
  1991年   16篇
  1990年   14篇
  1989年   6篇
  1988年   10篇
  1987年   7篇
  1986年   10篇
  1985年   10篇
  1984年   7篇
  1980年   5篇
  1979年   8篇
  1978年   8篇
  1977年   7篇
  1976年   9篇
  1975年   9篇
  1974年   8篇
  1972年   5篇
  1969年   4篇
  1967年   4篇
  1943年   5篇
排序方式: 共有910条查询结果,搜索用时 15 毫秒
141.
142.
143.
A 12-year-old, neutered female, Siberian Husky dog presented with a hind limb weakness of one month duration. To facilitate making a diagnosis multiple imaging modalities were performed. These modalities included radiography, ultrasonography, magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) and selective angiography of the abdominal aorta. In this dog, the MRI/MRA studies provided the first documentation of the external iliac thrombi and the collateral circulation via the lumbar arteries. At necropsy, an aortoiliac thrombus caused by a mineralized arteriosclerotic plaque was noted.  相似文献   
144.
Thirteen dogs with histopathologically confirmed malignancies were treated with mitoxantrone and cyclophosphamide combination therapy. One to four doses were administered at 21-day intervals. Recombinant human granulocyte colony-stimulating factor was administered to ameliorate myelosuppression in dogs with neutrophil nadirs less than 1,000/microl. While the protocol appears to be safe for use in tumor-bearing dogs, an advantage over mitoxantrone single-agent protocols in terms of tumor response was not demonstrated in this initial pilot study.  相似文献   
145.
Two experiments were conducted with chicks to examine the effect of high dietary levels of soluble sources of Zn on tissue Zn, Cu, and Fe concentrations as influenced by two methods of oral Zn administration from 14 to 21 d of age. Treatments included the basal diet (62 ppm Zn), basal diet supplemented with 1,000 ppm Zn from Zn sulfate, acetate, or chloride fed continuously, or basal diet plus crop intubation with a single oral dose of water (control) or 1,000 ppm Zn dietary equivalent from the sources based on feed intake from the previous day. In Exp. 2, crop-intubated doses were administered daily from 14 to 21 d of age. In Exp. 1, chicks given Zn by gavage decreased (P < .0001) feed intake at 24 h after oral dose compared with chicks fed either the control or high-Zn diets. After the gavage dosing stopped, feed intake was similar among treatments. Bone Zn was increased (P < .0001) by Zn source and was greater at 24 than at 168 h after dosing by gavage. In chicks given a single gavage dose of Zn, liver and kidney Zn measured at 24 h after oral dosing was greater (P < .0001) than at 168 h. In birds given a single oral dose of Zn, time x Zn source interactions were observed in pancreas (P < .0001), mucosal cells (P < .01), and remaining intestinal tract segments (P < .001). In Exp. 2, greater bone, pancreas, kidney (P < .0001), and liver (P < .001) Zn accumulations were observed in chicks given daily gavage doses of Zn compared with those fed Zn in diets. Zinc from the four sources was absorbed and stored in tissues to a similar extent.  相似文献   
146.
Thirteen crossbred ewes were used to compare weigh-suckle-weigh (WSW) and machine milking (MM) methods for determining milk production of ewes that were rearing single or twin lambs. At parturition, ewes were 13 mo of age and produced six single lambs and seven pairs of twin lambs. Milk production estimates were initiated on d 6 of lactation and a 3-d rotation of the two techniques was implemented. On d 6, milk production was measured using WSW; on d 7, MM was used. No measurement was made on d 8. The 3-d rotation was repeated 20 times throughout a 63-d lactation, resulting in 20 point estimates of milk production for each method of measurement for each ewe. The WSW procedure consisted of a 3-h period in which lambs were withheld from suckling their dams. This was followed by a suckling period, a second 3-h withholding period, and a second suckling period. Differences in pre- and postsuckling lamb weights of the second suckling period were defined as milk consumption and, indirectly, 3-h milk production. The MM procedure included an administration of 10 IU of oxytocin (i.v.), followed by evacuation of the udder with a machine using commercially available sheep milking equipment, and the milk was discarded. Lambs were withheld from suckling the ewes for a 3-h period, followed by a repetition of the oxytocin and machine milking procedures. Milk from the second milking was weighed. Milk production estimates determined using the WSW and MM techniques were similar (P = .42). Average 3-h milk production was 340 and 351 g for WSW and MM, respectively. Machine milking provides a reliable tool in evaluating the milk-producing ability of ewes that are rearing single or twin lambs.  相似文献   
147.
A new series of substituted 2-anilino-3-methylbutyrates has been prepared; bioassay data for these compounds on Heliothis virescens, Musca domestica, Aphis fabae and Tetranychus urticae are presented and discussed. Some unexpected relationships were observed between the nature of the substituents and the biological activity. Increases in foliar stability were noted with certain substitution patterns. Both α-cyano-3-phenoxybenzyl 3-methyl-2-(α, α, α,2-tetrafluoro-p-toluidino)butyrate and the corresponding 2-(2-chloro-α, α, α-trifluoro-p-toluidino)-3-methylbutyrate showed good stability in air and light, and exhibited biological activities of a similar nature and potency to those of previously known synthetic pyrethroids. Esters of the (R)-2- anilino-3-methylbutyric acids are far more active than those prepared from the (S)-enantiomers. The (R)-configuration at C-2 in these acids is sterically equivalent to the active absolute configuration at the chiral carbon α to the carboxylate group in both the permethrin and the fenvalerate types of pyrethroids. A new class of insecticidal 2-(isoindolin-2-yl)alkanoates is also reported. In this series the most biologically active analogue was α-cyano-3-phenoxybenzyl 3-methyl-2-(4,5,6,7-tetrafluoroisoindolin-2-yl)butyrate. These esters were considerably less stable than the anilino analogues on exposure to air and light.  相似文献   
148.
149.

Background

Transitional cell carcinoma is the most common bladder cancer of dogs. Cisplatin combined with piroxicam provides superior response rates, but unacceptable rates of nephrotoxicity. Tavocept is a chemoprotectant that has mitigated cisplatin toxicity and decreased the required infusion/diuresis volume in clinical trials in humans.

Hypothesis/Objectives

We hypothesized that Tavocept would decrease diuresis volume and time and facilitate safe administration of a cisplatin/piroxicam protocol to dogs with bladder cancer. Secondary objectives were to compare response rate and survival times to an historical comparator group treated without Tavocept.

Animals

Fourteen client‐owned dogs were prospectively enrolled.

Methods

Tumor volume was measured by computed tomography at days 0, 42, and 84. Dogs received combination Tavocept/cisplatin with a shortened diuresis protocol. A total of 4 doses was planned, with concurrent administration of piroxicam. Serial biochemical analyses were evaluated for azotemia.

Results

A 90‐minute infusion/diuresis time was used for all dogs. Three dogs (21%) had concurrent increases in serum creatinine (>2.0 mg/dL) and BUN (>42 mg/dL) concentrations; 2 of these dogs were isosthenuric. This frequency of nephrotoxicity is significantly less (P = 0.0406) than that of an historical control group treated without Tavocept. Overall response rate was 27%. Median survival time was comparable to historical controls (253 vs. 246 days).

Conclusions and Clinical Importance

Tavocept decreased the required diuresis time with cisplatin from > 6 hours to 90 minutes, while also decreasing occurrence of azotemia. Survival time was comparable, but the response rate was inferior to an historical comparator group. Further evaluation in other tumors susceptible to platinum agents is warranted.  相似文献   
150.
Amblyomma variegatum, the Tropical Bont Tick (TBT), is the principal vector of heartwater and is associated with dermatophilosis, major causes of losses in animal production and mortality in Caribbean livestock. From 1995 to 2007, the Caribbean Amblyomma Programme (CAP) supported treatment and surveillance activities in 11 islands of the Eastern Caribbean with an initial objective of eradicating TBT. In addition to control activities, surveillance data were collected between 1997 and 2006 in a unique regional database. We report the analysis of the surveillance data from four islands (Nevis, St Kitts, St Lucia, and Barbados) where control and surveillance followed the initial protocol and where enough data were collected. We describe the evolution of TBT infestation levels and the efforts carried out throughout the surveillance period. Logistic regression identified factors associated with herds found infested with TBT. Overall, treatment programmes were associated with a decrease in proportion of TBT-infested farms. High surveillance efforts were carried out throughout the 1997–2007 period for all island of interest, but inadequate level of surveillance was observed in several quarters especially for St Kitts. Third quarter of the year, as indication of adult TBT seasonality on livestock, was significantly associated with the risk of detecting TBT in Nevis and St Kitts livestock farms. Also, presence of cattle in Nevis farms was shown associated with an increasing probability of farms being declared TBT-infested. Outcomes of these analyses provide basis for recommendations to improve future national and regional control and surveillance activities. This analysis demonstrates the usefulness of long term and adequate surveillance data for control programmes and identification of factors associated with risk of having infested herds.  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