全文获取类型
收费全文 | 95831篇 |
免费 | 3141篇 |
国内免费 | 66篇 |
专业分类
林业 | 4144篇 |
农学 | 3035篇 |
基础科学 | 468篇 |
11018篇 | |
综合类 | 17197篇 |
农作物 | 3311篇 |
水产渔业 | 4753篇 |
畜牧兽医 | 48349篇 |
园艺 | 1068篇 |
植物保护 | 5695篇 |
出版年
2019年 | 842篇 |
2018年 | 1376篇 |
2017年 | 1473篇 |
2016年 | 1333篇 |
2015年 | 1144篇 |
2014年 | 1409篇 |
2013年 | 3271篇 |
2012年 | 2629篇 |
2011年 | 3105篇 |
2010年 | 2072篇 |
2009年 | 2102篇 |
2008年 | 3079篇 |
2007年 | 3012篇 |
2006年 | 2839篇 |
2005年 | 2639篇 |
2004年 | 2560篇 |
2003年 | 2572篇 |
2002年 | 2316篇 |
2001年 | 3209篇 |
2000年 | 3212篇 |
1999年 | 2517篇 |
1998年 | 961篇 |
1997年 | 917篇 |
1996年 | 867篇 |
1995年 | 1061篇 |
1994年 | 938篇 |
1993年 | 885篇 |
1992年 | 1944篇 |
1991年 | 2005篇 |
1990年 | 1948篇 |
1989年 | 1872篇 |
1988年 | 1777篇 |
1987年 | 1839篇 |
1986年 | 1774篇 |
1985年 | 1745篇 |
1984年 | 1424篇 |
1983年 | 1261篇 |
1982年 | 818篇 |
1979年 | 1204篇 |
1978年 | 992篇 |
1977年 | 860篇 |
1976年 | 820篇 |
1975年 | 905篇 |
1974年 | 1153篇 |
1973年 | 1051篇 |
1972年 | 1132篇 |
1971年 | 1053篇 |
1970年 | 953篇 |
1969年 | 1002篇 |
1967年 | 844篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
F Urayama T Sato H Shibuya W Shirai M Matsutani R Yamazaki 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(11):1249-1252
An apocrine adenocarcinoma was observed in the subcutis of the abdomen of golden hamster. Histologically, the tumor cells irregularly formed multiple layers of cysts and some detached cells were presented in the cystic space. PAS stain with alpha-amylase digestion revealed PAS-positive alpha-amylase-resistant granules in the cytoplasm. Immunohistochemically, cytokeratin was demonstrated in the tumor cells. By electron microscopy, the tumor cells had an oval nucleus with invagination, abundant cytoplasmic organelles and microvilli protruding into the intercellular spaces. 相似文献
32.
33.
The effect of salinity on seed germination, plant yield parameters, and plant Na, Cl and K concentrations of chickpea and lentil varieties was studied. Results showed that in both crops percentage emergence was significantly reduced by increasing NaCl levels (0–8dSm?1). From the plant growth studies it was found that differences existed among chickpea and lentil varieties in their response to NaCl application. In chickpea, the variety Mariye showed the comparatively lowest germination percentage and the lowest seedling shoot dry weight in response to salinity and was also among the two varieties which had the lowest relative plant height, shoot and root dry weight and grain yield at maturity. Similarly, variety DZ-10-16-2, which was the second best in germination percentage and the highest in terms of seedling shoot dry weight, also had the highest relative plant height, shoot and root dry weights, and grain yield at maturity. In lentil, however, such relationships were less pronounced. Chloride concentration (mg g?1) in the plant parts at salt levels other than the control was about 2–5 times that of Na. K concentration in the plants was significantly reduced by increasing NaCl levels. Chickpea was generally more sensitive to NaCl salinity than lentil. While no seeds were produced at salinity levels beyond 2dSm?1 in chickpea (no seeds were produced at this salt level in the most sensitive variety, Mariye), most lentil varieties could produce some seeds up to the highest level of NaCl application. Overall, varieties R-186 (lentil) and Mariye (chickpea) were the most sensitive of all varieties. On the other hand, lentil variety NEL-2704 and chickpea variety DZ-10-16-2 gave comparatively higher mean relative shoot and root dry weights, and grain yield, thus showing some degree of superiority over the others. The observed variations among the varieties may be useful indications for screening varieties of both crops for salt tolerance. 相似文献
34.
35.
T Bilzer 《Tier?rztliche Praxis》1991,19(3):276-281
Invasive tumors of the pituitary gland associated with Cushing's disease and diabetes insipidus are described in ten dogs. All patients showed typical clinical symptoms including polyuria/polydipsia and acanthosis nigricans. All tumors led to compression und partial destruction of the posterior lobe of the pituitary gland and the infundibular stalk; two of them infiltrated the hypothalamic region. All tumors produced ACTH and caused hyperadrenocorticism. In six cases, additional expression of beta-lipoprotein and MSH were found: in pars intermedia adenomas many cells stained strongly for MSH and/or beta-lipoprotein, whereas in tumors of the pars distalis only occasional cells stained positive. The purpose of the present study was to describe the neuropathological findings and the immunohistochemistry of hormone excretion in pituitary tumors in dogs resulting in Cushing's disease associated with D.i., to review the literature and to discuss the pathogenesis. 相似文献
36.
J L Becht R D Park S L Kraft P F Steyn R H Wrigley 《Veterinary Clinics of North America: Equine Practice》2001,17(1):1-18
Effective radiographic interpretation requires a veterinarian who is knowledgeable of equine limb anatomy and the various principles that affect the resulting image. The normal and its variations must be recognized and understood before the abnormal can be confidently identified as pathologic. Proper patient positioning and sound radiographic technique are mandatory if reliable diagnostic radiographs are to be produced. This review emphasizes equine foot radiographic variations of normal and pseudolesions that occur with commonly used radiographic views performed in equine practice. 相似文献
37.
The technique of liver puncture as described by Holtenius (1961) was assessed with regard to its practicability and safety in a preliminary study of 26 cattle and a follow-up study of 108 German black pied cattle. The sample material was smeared, stained and examined by light microscope. All animals with changes of grade 5 had to be slaughtered. Liver puncture is a simple, quick and safe technique which supplies useful information about the various stages of hepatic fatty degeneration in individual cattle. 相似文献
38.
Sandy‐textured Mediterranean soils are invariably depleted in organic matter and supply only small amounts of N to crops. To compensate for these deficiencies, we tested the N supply from six organic wastes applied to a Cambic Arenosol in pots growing ryegrass. The results showed that the behaviour of the wastes in supplying N to a ryegrass crop grown in this soil can be predicted by observing their performance in laboratory aerobic incubations. The N made available during these incubations fitted well to a one‐pool kinetic model. 相似文献
39.
Conrado M. Gempesaw J. Richard Bacon Ferdinand F. Wirth 《Journal of the World Aquaculture Society》1992,23(1):38-48
The objective of this study was to evaluate the relationship of pond size and hybrid striped bass growout profitability as an alternative source of farm income in the Mid-Atlantic region. A dynamic, whole farm, Montdarlo capital budgeting simulation model (AQUASIM) and stochastic dominance with respect to a function technique were used to analyze the economics of hybrid striped bass growout from phase II to market production stage for eight farms categorized by pond sizes. Three scenarios are assumed to examine the effects of pond-size dependent changes in feed conversion efficiency and fingerling survival rates on discounted after-tax net present values and probabilities of economic survival and success. Optimal pond sizes were found to be in the 2.5 acre to 10 acre range. 相似文献
40.
K Miyahara T Matsumoto S Tose H Sakurai I Igarashi A Saito T Hirose N Suzuki 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(1):87-93
Spleen cells from Toxoplasma lysate antigen (TLA)-sensitized BALB/c mice showed the strong cytotoxic activity against both natural killer (NK)-sensitive cells (YAC-1 and RL male-1) and NK-insensitive cells (P-815), when incubated with TLA or recombinant human IL-2 (rhIL-2). The increment of TLA concentration in culture medium increased the cytotoxic activity. Treatment of effector cells; spleen cells from TLA-sensitized mice incubated with TLA, with anti-asialo GM1 or anti-Thy-1 plus complement inhibited the cytotoxic activity of effector cells, whereas treatment with anti-mouse Lyt-2.2 serum plus complement had no effect on the cytotoxic activity. Treatment of spleen cells from TLA-sensitized mice with anti-asialo GM1 and/or anti-Thy-1 plus complement inhibited cytotoxic activities of effector cells. These results suggested that spleen cells sensitized with TLA both in vivo and in vitro were asialo GM1 positive and Thy-1 positive, and the majority of cytotoxic cells induced by TLA were similar to lymphokine-activated killer (LAK) cells induced by IL-2. 相似文献