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   2821篇
  免费   0篇
电工技术   2篇
化学工业   17篇
金属工艺   2篇
建筑科学   1篇
轻工业   2篇
石油天然气   2篇
无线电   6篇
一般工业技术   23篇
冶金工业   2752篇
自动化技术   14篇
  2021年   1篇
  2018年   1篇
  2017年   1篇
  2016年   2篇
  2014年   1篇
  2013年   1篇
  2012年   1篇
  2011年   6篇
  2010年   3篇
  2008年   4篇
  2007年   3篇
  2006年   1篇
  2005年   2篇
  2004年   4篇
  2003年   5篇
  2002年   2篇
  2000年   3篇
  1999年   83篇
  1998年   807篇
  1997年   438篇
  1996年   306篇
  1995年   167篇
  1994年   154篇
  1993年   172篇
  1992年   17篇
  1991年   34篇
  1990年   35篇
  1989年   37篇
  1988年   44篇
  1987年   39篇
  1986年   27篇
  1985年   33篇
  1984年   1篇
  1983年   3篇
  1982年   15篇
  1981年   14篇
  1980年   31篇
  1978年   8篇
  1977年   94篇
  1976年   212篇
  1975年   5篇
  1955年   4篇
排序方式: 共有2821条查询结果,搜索用时 15 毫秒
11.
BACKGROUND: The incidence of intrathyroidal parathyroid glands remains controversial. The purpose of this study was to determine the incidence in a series of patients with hyperparathyroidism. METHODS: Three hundred nine patients underwent parathyroidectomy. Patients were divided into two groups: uniglandular disease versus hyperplasia. RESULTS: Eighteen of 309 patients (6%) had abnormal intrathyroidal parathyroid glands. The incidence was 3% (7 of 222) in patients with uniglandular disease versus 15% (11 of 73) in those with hyperplasia. With a mean follow-up of 54 months, 12 patients are eucalcemic, 5 have persistent hypocalcemia, and 1 has recurrent hypercalcemia. There were no recurrent laryngeal nerve injuries. CONCLUSIONS: These data suggest that an intrathyroidal adenoma is an uncommon cause of failure, whereas abnormal intrathyroidal parathyroid tissue may be a more common cause of failure in patients with hyperplasia.  相似文献   
12.
Three studies were conducted to evaluate amino acid utilization by cattle. In Exp. 1, five steers (580 kg) were fed 86% rolled corn diets with mixtures of amino acids containing up to 6 g/d DL-Met, 24 g/d L-Lys, 6 g/d L-Thr, and 3 g/d L-Trp. Treatments had little effect on ruminal fermentation, diet digestibility, N flow to the duodenum, or microbial efficiency. Ruminal concentrations of Met and Lys increased linearly (P < .05) with amino acid supplementation, whereas Thr responded quadratically, and Trp was not altered. In Exp. 2, four steers (414 kg) were used to measure effects of dietary monensin or laidlomycin propionate in high-grain diets supplemented with amino acids. Ionophores had no significant effect on ruminal fermentation or outflows of amino acids from the rumen. In Exp. 3, 100 steers (287 kg initial BW) were fed diets containing 1% of a nonprotein N source. Treatments were 1) no supplemental N (UREA), 2) UREA plus soybean meal (SBM), 3) UREA plus 2 g/d DL-Met, 8 g/d L-Lys, 2 g/d L-Thr, and 1 g/d L-Trp, or 4) UREA plus 4 g/d DL-Met, 16 g/d L-Lys, 4 g/d L-Thr, and 2 g/d L-Trp. During the growing period (diets based on whole-plant milo silage), gains were higher for SBM-supplemented steers than for UREA steers and intermediate for steers supplemented with amino acids. Few significant differences in performance were observed among treatments during the finishing phase (diets based on dry-rolled corn) or for the entire experiment, but cattle fed SBM or amino acids tended to be fatter and have better marbling scores and quality grades. Amino acids did not greatly alter ruminal fermentation or cattle performance.  相似文献   
13.
This paper provides a review of materials and designs for sodium-beta alumina battery technology and discusses the challenges ahead for further technology improvement. Sodium-beta alumina batteries have been extensively developed in recent years and encouraging progress in performance and cycle life has been achieved. The battery is composed of an anode, typically molten sodium, and a cathode that can be molten sulfur (Na-S battery) or a transition metal halide incorporated with a liquid phase secondary electrolyte (e.g., ZEBRA battery). In most cases the electrolyte is a dense solid β″-Al2O3 sodium ion-conducting membrane. The issues prohibiting widespread commercialization of sodium-beta alumina technology are related to the materials and methods of manufacturing that impact cost, safety, and performance characteristics.  相似文献   
14.
We have determined the nucleotide sequence of the blaS gene encoding the carbapenem-hydrolyzing L-1 beta-lactamase from Stenotrophomonas maltophilia GN12873. Analysis of the DNA and deduced amino acid sequences identified a product of 290 amino acids. Comparisons of the L-1 amino acid sequence with those of other zinc beta-lactamases showed 88.6% identity with the L-1 enzyme from S. maltophilia IID1275 and less than 20% identity with other class B metalloenzymes.  相似文献   
15.
16.
17.
18.
We have reported our experience with splenectomy in fifty patients less than fourteen years old. The indications, results, and complications were enumerated. These data were then correlated with the recent literature regarding pediatric splenctomy. Of special note is the problem of immunologic incompetency associated with splenectomy in the patients less than five years old.  相似文献   
19.
A case of multiple adenocarcinoma arising from the kidney, bladder, and prostate is presented with a relevant discussion of the possible factors of pathogenesis. A staged approach of radical extirpative surgery is suggested.  相似文献   
20.
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