全文获取类型
收费全文 | 1852篇 |
免费 | 0篇 |
专业分类
化学工业 | 6篇 |
机械仪表 | 2篇 |
建筑科学 | 2篇 |
能源动力 | 2篇 |
轻工业 | 17篇 |
一般工业技术 | 3篇 |
冶金工业 | 1816篇 |
原子能技术 | 1篇 |
自动化技术 | 3篇 |
出版年
2022年 | 1篇 |
2017年 | 2篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 4篇 |
1999年 | 44篇 |
1998年 | 542篇 |
1997年 | 273篇 |
1996年 | 200篇 |
1995年 | 111篇 |
1994年 | 92篇 |
1993年 | 102篇 |
1992年 | 18篇 |
1991年 | 29篇 |
1990年 | 23篇 |
1989年 | 36篇 |
1988年 | 37篇 |
1987年 | 31篇 |
1986年 | 33篇 |
1985年 | 18篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 55篇 |
1976年 | 126篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1852条查询结果,搜索用时 0 毫秒
81.
82.
DH Shah RR Vartak SS Naik SR Dandekar R Ganapati 《Canadian Metallurgical Quarterly》1994,62(4):539-546
Children residing in a low-endemic region (LER), a high-endemic region (HER), and a leprosy colony contact population (CP) were evaluated for lepromin response as well as reactivity to the Mycobacterium leprae-specific synthetic antigen, ND-BSA. The mean reactivity to ND-BSA in the LER group (OD 0.03 +/- 0.03, N = 71) was significantly lower (p < 0.001) than that in the contact population (OD 0.14 +/- 0.09, N = 140) as well as the population residing in the HER (OD 0.09 +/- 0.08, N = 1340). ELISA-positive results were the highest (21.4%) with the CP group and lowest (0.0%) in the LER group, suggesting that it was a measure of the extent of exposure of M. leprae. In the contact population, females showed a preponderance for ELISA positivity over males (p < 0.005), a finding not observed with the HER population. The Mitsuda responses showed a Gaussian-type distribution in all of the three populations examined with the mean response being highest in the LER (6.0 mm +/- 2.9) and lowest in the HER (4.5 mm +/- 2.0) groups. The percent positivity for the Mitsuda reaction was found to be highest in the LER (93.0%) and lowest in the HER (88.3%) groups. The Mitsuda response thus appears to be independent of M. leprae exposure, and its interpretation in a given population needs consideration of several factors, such as nutritional, environmental, etc.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
83.
Analysis of mitochondrial (mt)DNA size polymorphism in the form of variable number tandem repeats (mtVNTRs) has become an increasingly popular methodology for addressing questions in molecular ecology. When detected by PCR, mtVNTR analysis can provide a sensitive, rapid, and cost-effective measure of genetic variability that may be exploited in studies of population differentiation and biogeography. Despite the emergence of this approach, there has been little critical evaluation of its success or utility as a practical tool. In this review, we identify problematic methodological, theoretical and interpretive factors that can influence the utility of mtVNTR analysis. The reliability of the procedure is considered in terms of both detection of alleles and scoring of intra-individual allele frequencies. While many of the potential technical problems of the technique do not raise serious practical concerns, this rapid and sensitive methodology is seriously compromised by the difficulty of reliably assessing allele frequencies, of assaying only germline tissue, and in our ignorance of the mechanisms generating mtVNTR diversity. Thus, although there is a considerable potential for mtVNTR pilot studies to assess genetic diversity, the utility of the technique to resolve broader questions in molecular ecology should be treated cautiously until such a time as the system is better understood. 相似文献
84.
JE Cobb SG Blanchard EG Boswell KK Brown PS Charifson JP Cooper JL Collins M Dezube BR Henke EA Hull-Ryde DH Lake JM Lenhard W Oliver J Oplinger M Pentti DJ Parks KD Plunket WQ Tong 《Canadian Metallurgical Quarterly》1998,41(25):5055-5069
3-?4-[2-(Benzoxazol-2-ylmethylamino)ethoxy]phenyl?-(2S)-((2- benzoylph enyl)amino)propionic acid (1) and (2S)-((2-benzoylphenyl)amino)-3-?4-[2-(5-methyl-2-phenyloxazol-4-y l)e thoxy]phenyl?propionic acid (2) are peroxisome proliferator-activated receptor gamma (PPARgamma) agonists and have antidiabetic activity in rodent models of type 2 diabetes. As part of an effort to develop the SAR of the N-2-benzoylphenyl moiety of 1 and 2, a series of novel carboxylic acid analogues, 23-66, modified only in the N-2-benzoylphenyl moiety were synthesized from L-tyrosine and evaluated as PPARgamma agonists. In general, only modest changes in the N-2-benzoylphenyl moiety of 1 and 2 are tolerated. More specifically, the best changes involve bioisosteric replacement of one of the two phenyl rings of this moiety. Addition of substituents to this moiety generally produced compounds that are less active in the cell-based functional assays of PPARgamma activity although binding affinity to PPARgamma may be maintained. A particularly promising set of analogues is the anthranilic acid esters 63-66 in which the phenyl ring in the 2-benzoyl group of 1 and 2 has been replaced by an alkoxy group. In particular, (S)-2-(1-carboxy-2-?4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phen yl? ethylamino)benzoic acid methyl ester (63) has a pKi of 8.43 in the binding assay using human PPARgamma ligand binding domain and a pEC50 of 9.21 in the in vitro murine lipogenesis functional assay of PPARgamma activity. Finally, 63 was found to normalize glycemia when dosed at 3 mg/kg bid po in the Zucker diabetic fatty rat model of type 2 diabetes. 相似文献
85.
Recent studies have suggested that protein kinase C (PKC) may be involved in the formation of brain edema. In this paper, the effects of two kinds of PKC inhibitors, H-7 and matrine, were examined on the brain edema formation in experimental models. The results showed that pretreatment with H-7 6.25 and 12.5 mg.kg-1 prevented the accumulation of water and certain electrolytes in the unilateral hemisphere of the brain evoked by ligation of a single common carotid artery in Mongolian gerbil; pretreatment with matrine 25 and 50 mg.kg-1 reduced the extent of cerebral edema formation evoked by ligation of a single common carotid artery in gerbil and by middle cerebral artery occlusion in Sprague-Dawley rats. These results present new evidence for the involvement of PKC in the formation of brain edema. 相似文献
86.
DH Spodick 《Canadian Metallurgical Quarterly》1976,54(4):698-699
87.
Differential characteristics of the electrocardiogram in early repolarization and acute pericarditis
DH Spodick 《Canadian Metallurgical Quarterly》1976,295(10):523-526
Electrocardiographic mimicry necessitates differentiation between acute pericarditis and early repolarization. Among 96 persons, limb-lead RST deviations occurred in all 48 with pericarditis, but only 27 with early repolarization. RS-T vectors (A RS-T) in pericarditis tended to be horizontal (25 patients) and left of the T vector, A T (28 patients); in early repolarization, A RS-T was vertical in 15 subjects and right of A T (20 subjects); P less than or equal to 0.01. RS-T depression in Lead V1 was more common in pericarditis (14 vs. two); isoelectric RS-T in Lead V6 was more common in early repolarization (10 vs. one); P less than or equal to 0.01. PR segment deviations occurred in both limb and precordial leads in pericarditis; in early repolarization they were confined to either lead group. Thus, R-ST deviations in both limb and precordial leads with horizontal A RS-T to left of A T and RS-T depression in Lead V1 favor pericarditis; vertical A RS-T and isoelectric RS-T in Lead V6 favor early repolarization. 相似文献
88.
89.
90.
MT LaRocco LF Rodriguez CY Chen GS Smith DH Russell SI Myers CS Cocanour RL Reed TA Miller 《Canadian Metallurgical Quarterly》1993,40(3):212-220
The present study was undertaken to determine the conditions under which acute periods of hemorrhagic shock induce bacterial translocation. Rats (at least six per group) were anesthetized intraperitoneally with the barbiturate, pentobarbital (50 or 65 mg/kg), or the inhalation anesthetic methoxyflurane. Following anesthesia, the femoral artery was catheterized, from which blood was withdrawn to maintain a mean arterial blood pressure of 30 mmHg for 30, 60, or 90 min, followed by reinfusion of shed blood. Instrumented, but nonshocked animals served as controls. Rats were sacrificed at 0, 2, or 24 hr postshock, and quantitative bacterial cultures of the mesenteric lymph node complex (MLN), liver, and spleen were made. Within groups, the effects of heparinization were also determined. In pentobarbital-treated animals, regardless of the extent of heparinization, consistent translocation to both MLN and distant organs occurred when shock was prolonged for 90 min, and assessment of translocation was made 24 hr after reinfusion of shed blood. Furthermore, a mortality rate of approximately 30% was found in rats subjected to this protocol. The magnitude of translocation was less consistent, and did not differ from that in sham shock controls, under other conditions of shock and evaluation. In rats anesthetized with methoxyflurane, no mortality occurred, and no statistical significance between the incidence or degree of translocation in shocked animals vs. sham shock controls could be demonstrated, regardless of the shock protocol. In additional studies, effects of these anesthetics on intestinal morphology and superior mesenteric arterial (SMA) flow in the context of hemorrhagic shock were assessed.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献