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   17280篇
  免费   913篇
  国内免费   19篇
林业   830篇
农学   565篇
基础科学   124篇
  2524篇
综合类   2730篇
农作物   918篇
水产渔业   960篇
畜牧兽医   8446篇
园艺   197篇
植物保护   918篇
  2021年   158篇
  2020年   162篇
  2019年   186篇
  2018年   314篇
  2017年   368篇
  2016年   263篇
  2015年   201篇
  2014年   323篇
  2013年   678篇
  2012年   504篇
  2011年   637篇
  2010年   433篇
  2009年   416篇
  2008年   640篇
  2007年   563篇
  2006年   520篇
  2005年   465篇
  2004年   434篇
  2003年   437篇
  2002年   381篇
  2001年   499篇
  2000年   479篇
  1999年   376篇
  1998年   180篇
  1997年   203篇
  1996年   159篇
  1995年   192篇
  1993年   165篇
  1992年   286篇
  1991年   317篇
  1990年   312篇
  1989年   314篇
  1988年   289篇
  1987年   248篇
  1986年   300篇
  1985年   255篇
  1984年   213篇
  1983年   209篇
  1979年   256篇
  1978年   166篇
  1975年   171篇
  1974年   236篇
  1973年   217篇
  1972年   253篇
  1971年   234篇
  1970年   203篇
  1969年   195篇
  1968年   158篇
  1967年   160篇
  1966年   166篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A method is described for production of an equine anti-bovine leukocyte serum (EABLS). Leukocytes were harvested from the milk of cow's udders which had been irritated with endotoxin. The washed leukocytes as antigens were administered to 2 horses in a series of subcutaneous and intravenous injections. There was a variably progressive increase in total serum proteins and a decrease in albumin/blobulin ratios, but the most pronounced change was an increase in beta2-globulins. Accompanying these changes was an increase in the number of precipitin lines as shown by Ouchterlony analysis. Four old cows and 2 calves were intravenously given a 50- and 20-ml dose, respectively, of the EABLS. Two of the cows and 1 of the calves were given the EABLS which had been heated to 56 C for 30 minutes. Both calves and the 2 cows given heated EABLS and 1 cow given unheated EABLS developed marked neutropenia within the 1st hour. The 4th cow given unheated EABLS developed only slight neutropenia. It was concluded that there may be variation in the individual animal's susceptibility to the neutropenia-inducing activity of EABLS.  相似文献   
62.
63.
64.
65.
66.
In a 7 year old female poodle an adrenocortical tumor was diagnosed on basis of laboratory and ultrasonographic examinations. One year after adrenalectomy, a relapse was diagnosed, at that time the suspicion of metastases in the liver arose for the first time. By treatment with Mitotane in a dose aiming at completely destroying the adrenal cortex, a complete disappearance of the tumor as well as a dramatic reduction of the size of the metastases could be achieved. 12 months after the begin of the chemotherapy, the dog is in good general condition.  相似文献   
67.
68.
Previously, the structure of the adult goat parotid salivary glands (PGs) was studied. However, little information was elucidated of the juvenile ones. This study aimed to clarify the correlations between the structure of goats' PGs and the nature of food intake among milk‐suckling kids (MSKs) and diet‐fed goats (DFGs). The secretory endpieces of the goats' PGs are of the pure serous type. The serous cells in MSKs showed apical accumulation of numerous secretory granules (SGs) of smaller size and of more intense positive periodic acid‐Schiff reaction. Ultrastructurally, most of the SGs in the DFGs contained peripherally located inclusions that showed dense reaction products for acid phosphatase. In MSKs, the PGs showed less‐developed basal infoldings, sparseness of the inter‐cellular inter‐digitations, fewer inter‐cellular canaliculi and microvilli and also less‐developed myoepithelial cells with fewer and shorter cytoplasmic processes. In conclusion, the less‐developed membrane specializations and myoepithelial cells, as well as the accumulated SGs in the PGs of MSKs, suggest that it secretes less saliva with a little secretory activity than that of DFGs, which may be correlated with the reduced masticatory activity.  相似文献   
69.
A survey of aldicarb poisoning in companion animals was conducted by posting questionnaires to all private practitioners in Gauteng Province, South Africa. The survey was designed to determine the percentage of aldicarb cases seen, treatment regimen, clinical signs observed, proposals for preventative actions and more effective treatments. Other questions included duration of treatment, survival rate, cost to clients, post mortem findings and reasons for poisonings.  相似文献   
70.
Global climate change is expected to influence the distribution of global biodiversity. C4 and C3 perennial grasses co-occur in the fire-prone KwaZulu-Natal uKhahlamba-Drakensberg grasslands, with C3 grass species occurring at cooler locations in the mountain range and C4 grass species at warmer locations. If a warming climate is expected to cause a contraction in the ranges of C3 grasses, evidence of temperature controlling current distributions is required. This study modelled the distribution of five C3 grass species, namely Tenaxia stricta, Tenaxia disticha, Festuca costata, Merxmuellera drakensbergensis and Merxmuellera stereophylla, to temperature-related surrogate variables using presence–absence data collected across the environmental heterogeneity of the mountain range. Distributions of each species, and of all species combined, were modelled using generalised additive models. These temperature-related variables accounted for the distribution of all five species, least so for F. costata. Four species could therefore contract in range in response to climate change, whereas F. costata is least likely to have a range contraction directly related to a warming climate and could experience a range expansion owing to the fertilising effect of increased [CO2].  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