全文获取类型
收费全文 | 1090篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 10篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
轻工业 | 5篇 |
水利工程 | 1篇 |
无线电 | 16篇 |
一般工业技术 | 25篇 |
冶金工业 | 1012篇 |
原子能技术 | 1篇 |
自动化技术 | 12篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2016年 | 2篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 7篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 30篇 |
1998年 | 275篇 |
1997年 | 160篇 |
1996年 | 115篇 |
1995年 | 54篇 |
1994年 | 67篇 |
1993年 | 56篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 33篇 |
1976年 | 80篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有1091条查询结果,搜索用时 15 毫秒
81.
GF Haenlein 《Canadian Metallurgical Quarterly》1996,74(5):1173-1181
Among the major classes of U.S. livestock, dairy goats have yet to achieve USDA statistical reporting of their numbers, amounts of milk produced and processed, and cheese and other products marketed. However, the USDA has published buck proofs of approximately 16,000 does annually from Dairy Herd Improvement Association (DHIA) records of the Alpine, LaMancha, Nubian, Oberhasli, Saanen and Toggenburg breeds, thereby encouraging genetic progress. This represents a 1% participation in DHIA of the estimated 1.5 million U.S. dairy goats. Annual breed registrations are led by Nubians (11,000), and the leading states in descending order are California, Texas, Ohio, New York, and Pennsylvania. Breed average milk yields range from 960 kg of milk for Saanen to 726 kg of milk for Oberhasli. Average milk contents range from 4.5% fat and 3.69% protein for Nubian to 3.3% fat and 2.98% protein for Toggenburg. Leading lactation records are 3,023 kg of milk (Toggenburg) and 174 kg of fat (Nubian). Total annual registrations are 45,000+ animals by 16,000+ member breeders. Estimated total U.S. goat milk commercial production is 24,000+ t, with half going into commercial farm goat cheese production of 640+ t. Recent years have seen significantly increased numbers of dairy goat research projects and publications from Oklahoma, Texas, California, Georgia, Alabama, Florida, Louisiana, New York, Connecticut, Delaware, and Massachusetts. Furthermore, annual national and international symposia, annual national goat cheese judging competitions and workshops, an active national goat research foundation, representation on the National Interstate Milk Shippers Committee and Mastitis Council, and formation of a national association and council for the development and promotion of dairy goat products indicate an evolution from former emphasis on purebred breed development to a focus on market development. The conclusion is that dairy goats are emerging as a necessary and recognized U.S. industry. 相似文献
82.
AJ MacDonald EM Thornton GF Newlands SJ Galli R Moqbel HR Miller 《Canadian Metallurgical Quarterly》1996,88(3):375-383
The aim of this study was to compare the accuracy of computed tomography (CT) and single photon emission computerized tomography (SPECT) in the diagnosis of dementia. Fifty-two patients with clinical diagnosis of dementia and 11 controls were studied. The scans were interpreted by one experienced neuroradiologist and one nuclear radiologist, both blinded to the clinical data. In the diagnosis of dementia, CT and SPECT showed equal sensitivity (82.7%) and statistically similar specificity (63.8 and 81.8%, respectively). The specificity of SPECT in diagnosing Alzheimer's disease (100%) was statistically superior to CT (69%). However, both methods showed similar sensitivity in detecting Alzheimer's disease. In conclusion, SPECT and CT showed similar accuracy in the diagnosis of dementia. The quite high specificity of SPECT in Alzheimer's disease may be useful for confirming that diagnosis, particularly for patients with presenile onset of the disease. 相似文献
83.
The strength of knotted thread for 12 different types of suture knot in combination with 11 types of suture material used in surgery was investigated one week after insertion in subcutaneous tissue in rabbits. The results were compared with similar investigations on knot strength carried out with 'dry knots'. The thread dimension used in both experiments was 000 (USP). As in vitro, the weakest point of a suture loop subjected to traction was the knot. The incidence of thread rupture within the loop but outside the knot was 1.4% in vitro and 5.9% in vivo, and was commonest with plain catgut. With one exception, however, thread breakage occurred at greater strain than the average required to produce knot failure with the material in question. A greater proportion of knots slipped in vivo then in vitro (72% and 35% respectively), with reduction of the strength of the suture loop as result. There was also greater scatter of measured values under in vivo conditions (standard deviation: 11% in vitro, 23% in vivo). For 7 of 11 suture materials the results indicated a reduction in knot-holding power after one week in situ in the living animal compared with in vivo conditions. This was naturally enough most marked with the two types of catgut (chrome 48%, plain 57%). In contrast, Dexon apparently remained unchanged after one week in vivo. The non-absorbable materials tested showed an estimated average fall in knot-holding power from 100% to 88% (range 109-65%), viz, an average of 12% units. The loss of holding power in vivo was, however, apparently never greater than 1/3 compared with 'dry knots' and calculated on average for all types of knot with non-absorbable materials. 相似文献
84.
A patient with a unique case of chronic episodic arthritis coincident with flares of acneform, pustular, nodular and ulcerating skin lesions was observed over a five-year period. This patient and a review of the literature on arthritis associated with the inflammatory dermatoses provide evidence which may interrelate several of these nosologically confusing skin conditions, e.g., the family of leukocytoclastic angiitides with the newly posited acute febrile neutrophilic dermatosis of Sweet. Systemic manifestations and a variety of acneform, pustular, nodular and ulcerating cutaneous lesions in the inflammatory dermatoses are best explained by small vessel involvement, with individual syndromes being determined by the type and degree of vascular change. Perivascular neutrophilic infiltration is the unifying histologic feature of these small vessel diseases. Neutrophil infiltration differentiates these entities, and our patient, from the histologically nonspecific inflammations of the skin, e.g., Behcet's disease and pyoderma gangrenosum, which, although capable of causing identically appearing skin lesions, consist predominantly of lymphocytic dermal infiltrates even in the earlier stages. It appears important to recognized these morphologically varied acute inflammatory dermatoses with perivascular neutrophilic infiltration in view of their systemic features and the dramatic efficacy of corticosteroid therapy. 相似文献
85.
Threshold fluctuations are divided into short-term and long-term effects applying statistical methods. Sixteen normal and pathological visual fields were analysed in order to obtain values for the short-term, long-term and total fluctuations. Special attention is paid to fortuitous variations between the results obtained at successive examinations. Finally the concept of spatial correlations is introduced. 相似文献
86.
87.
Radioaerosol lung scintigraphy was performed in five infants in whom obstructive airway complications developed following assisted ventilation. These studies suggest that a primary functional defect was obstruction to airflow at the level of the major airways, which occurred during expiration. Perfusion lung scintigraphy showed areas of diminished or redistributed pulmonary blood flow, which, like the results of the radioaerosol scintigraphic studies, are findings often associated with adult chronic obstructive pulmonary disease. 相似文献
88.
H Yamamoto WB Atwood PH Baillon BC Barish GR Bonneaud A Courau GJ Donaldson R Dubois MM Duro EE Elsen SG Gao YZ Huang GM Irwin R Johnson H Kichimi J Kirkby DE Klem DE Koop J Ludwig GB Mills A Ogawa T Pal D Perret-Gallix R Pitthan DL Pollard CY Prescott LZ Rivkin LS Rochester W Ruckstuhl M Sakuda S Sherman EJ Siskind R Stroynowski SQ Wang SG Wojcicki WG Yan CC Young 《Canadian Metallurgical Quarterly》1985,32(11):2901-2910
89.
90.