全文获取类型
收费全文 | 2716篇 |
免费 | 0篇 |
专业分类
化学工业 | 4篇 |
建筑科学 | 1篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
石油天然气 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 2篇 |
冶金工业 | 2689篇 |
自动化技术 | 2篇 |
出版年
2019年 | 2篇 |
2017年 | 1篇 |
2011年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 1篇 |
1999年 | 80篇 |
1998年 | 805篇 |
1997年 | 470篇 |
1996年 | 290篇 |
1995年 | 152篇 |
1994年 | 141篇 |
1993年 | 177篇 |
1992年 | 20篇 |
1991年 | 34篇 |
1990年 | 43篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 21篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 15篇 |
1980年 | 32篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 70篇 |
1976年 | 181篇 |
1975年 | 4篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2716条查询结果,搜索用时 0 毫秒
101.
102.
103.
Congenital dislocation of the knee is a uncommon malformation. Frequently there is an association with other congenital deformities including congenital dislocation of the hip. The classification of Leveuf and Pais into three separate groups (Type A, Type B, Type C) is now widely accepted. Between October 1989 and April 1995 we evaluated ten children (five girls and five boys) with twelve dislocated knees. Clinical, radiographic and different ultrasonography examinations were carried out on both knees. The sonographic classification showed Type A in 3, Type B in 5 and Type C in 4 cases. The sonographic examination revealed the essential anatomic structures and their pathomorphology. The anterior and the posterior cruciate ligament could be demonstrated in the majority of the cases. Three dislocated knees showed an obliteration of the recessus suprapatellaris and fibrotic changes in the m. quadriceps. These cases required operative treatment. With conservative treatment we achieved a satisfactory result in eight children with nine disease knees. There was a good functional result with an average flexion of 106 degrees. Early conservative treatment recommend as the therapy of choice. Ultrasonography imaging offers the possibility of reliable differentiation into one of the three groups of the classification of Leveuf and Pais. Radiographic documentation during the therapy has become the exception. Ultrasonography imaging helped substantially in the decision making and the timing of operative treatment. 相似文献
104.
For ultrasonographic B-scan images collected by means of a handheld transducer moving in the elevational direction, frame spacings are computed with a speckle-decorrelation algorithm, without additional positioning hardware. Fully developed speckle volumes are automatically segmented and spacing computed from the decorrelation curves. Position accuracy is within 10% for phantoms and 15% for breast studies. The algorithm provides image-based registration, which allows accurate three-dimensional volume rendering. 相似文献
105.
JB Thomas SW Mascarella RB Rothman JS Partilla H Xu KB McCullough CM Dersch BE Cantrell DM Zimmerman FI Carroll 《Canadian Metallurgical Quarterly》1998,41(11):1980-1990
A study of the binding site requirements associated with the N-substituent of (+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) derivatives was undertaken using a set of rigid vs flexible N-substituents. The study showed that compounds 7-9 bearing the trans-cinnamyl N-substituent most closely reproduced the potency at the opioid receptor of the flexible N-propylphenyl or N-propylcyclohexyl analogues previously reported. Neither the N-substituted cis-cinnamyl nor the cis-phenylcyclopropylmethyl compounds 10 and 11, respectively, showed high affinity for the opioid receptor. However, the N-trans-phenylcyclopropylmethyl compound 12 closely approximated the affinity of compounds 7-9. Additionally, we found that free rotation of the phenyl ring is necessary for high affinity binding and mu receptor subtype selectivity as the planar N-substituted thianaphthylmethyl and benzofuranylmethyl compounds 13 and 14 had significantly lower binding affinities. Altogether, these findings suggest that the high binding affinity, selectivity, and antagonist potency of N-propylphenyl or N-propylcyclohexyl analogues of (+)-(3R, 4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) are achieved via a conformation wherein the connecting chain of the N-substituents is extended away from piperidine nitrogen with the appended ring system rotated out-of-plane relative to the connecting chain atoms. This conformation is quite similar to that observed in the solid state for 5, as determined by single crystal X-ray analysis. Additionally, it was found that, unlike naltrexone, N-substituents bearing secondary carbons attached directly to the piperidine nitrogen of 4 suffer dramatic losses of potency vs analogues not substituted in this manner. Using a functional assay which measured stimulation or inhibition of [35S]GTP-gamma-S binding, we show that the trans-cinnamyl analogues of (+)-(3R, 4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) retain opioid pure antagonist activity and possess picomolar antagonist potency at the mu receptor. 相似文献
106.
The efficacy of two different types of commercial competitive exclusion (CE) products against Salmonella was studied in three chicken assay trials. Chicks were treated on the day of hatch and challenged one day later either with Salm. infantis (Trials 1 and 2) or a combination of Salm. infantis and Salm. enteritidis (Trial 3). The caeca of the birds were examined for Salmonella five days after challenge. The mean logarithmic counts of Salmonella were from 3.4 to 5.7 in the groups treated with product. A derived from the whole caecal contents of an adult bird, from 0.0 to 1.2 in the groups treated with product B, a highly selected product that does not contain any clostridia, and from 6.3 to 7.6 in the control groups. None of the challenge organisms superseded the other in Trial 3, and neither did the double challenge affect the protective capacity of the treatment materials. 相似文献
107.
JM Mariner JB McMahon BR O'Keefe K Nagashima MR Boyd 《Canadian Metallurgical Quarterly》1998,248(3):841-845
Concentrations of the potent, HIV(human immunodeficiency virus) inactivating protein, cyanovirin-N (CV-N), which completely inhibit HIV-1 infectivity, do not block the binding of soluble CD4-receptor (sCD4) to HIV-1 lysates nor the attachment of intact HIV-1 virions to several target T-cell lines. Furthermore, in contrast to the known disassociative effects of sCD4 on viral envelope glycoproteins, treatment of HIVRF with high concentrations of CV-N results in complete viral inactivation but without apparent shedding of gp120 or other ultrastructural changes. These results are consistent with the view that the virucidal effects of CV-N result from interference with step(s) in the fusion process subsequent to the initial binding of the virus to target cells. 相似文献
108.
F Tesson P Richard P Charron B Mathieu C Cruaud L Carrier O Dubourg N Lautié M Desnos A Millaire R Isnard AA Hagege JB Bouhour M Bennaceur B Hainque P Guicheney K Schwartz M Komajda 《Canadian Metallurgical Quarterly》1998,12(6):385-392
The effects of two progestogen-only pills containing either 75 microgram desogestrel (DSG) or 30 microgram levonorgestrel (LNG) on hemostasis were investigated in a double-blind, randomized, controlled study of seven treatment cycles in 78 healthy women. DSG reduced factor VII activity (p < 0.05) and prothrombin fragment 1+2 (p < 0.05) and increased protein S (p < 0.001). LNG reduced factor VII activity (p < 0.01) and plasminogen activity (p < 0.01) and increased tissue-plasminogen activator (t-PA) (p < 0.05). At the end of the post-treatment cycle with DSG, protein S (p < 0.01) and t-PA (p < 0.05) were increased and plasminogen activity was decreased (p < 0.05), whereas with LNG, t-PA was increased (p < 0.001) and prothrombin fragment 1+2 (p < 0.05) and plasminogen activity (p < 0.001) were decreased. Between-group comparisons revealed higher values for DSG regarding the anticoagulatory parameter protein S at cycle 7 (p < 0.01) and post-treatment assessments (p < 0.05), and the fibrinolytic parameter plasmin-antiplasmin complex was higher with DSG at cycle 7 (p < 0.05) and at post-treatment (p < 0.05). Both preparations had comparable and potentially favorable effects of hemostasis, and may offer suitable hormonal contraception to women with a personal or family history of venous thromboembolic diseases. 相似文献
109.
DJ Rouse WW Andrews FY Lin CW Mott JC Ware JB Philips 《Canadian Metallurgical Quarterly》1998,92(6):931-934
OBJECTIVE: To determine the contemporary antibiotic susceptibility profile of vertically acquired group B streptococcal isolates. METHODS: Susceptibility to ampicillin, penicillin G, erythromycin, clindamycin, cefazolin, and gentamicin was assessed by two methods, minimal inhibitory concentration and disc diffusion. RESULTS: The susceptibility profiles of 119 colonizing and eight invasive strains of group B streptococcus isolated from January 1996 to September 1997 at two hospitals in Birmingham, Alabama-University of Alabama at Birmingham and Cooper Green-were studied. Minimal inhibitory concentration determinations indicated that all colonizing strains were susceptible or moderately susceptible to ampicillin and penicillin G. Resistance was noted by at least one strain to each of the other antibiotics; all were resistant to gentamicin, whereas 27 (21%) were resistant to erythromycin, five (4%) to clindamycin, and one (1%) to cefazolin. All of the eight invasive strains were susceptible or moderately susceptible to ampicillin, penicillin G, clindamycin, and cefazolin; one (13%) was resistant to erythromycin, and all were resistant to gentamicin. Disc diffusion results generally were concordant with minimal inhibitory concentration results, although by disc diffusion fewer isolates were classified as susceptible, and more as moderately susceptible, to ampicillin and penicillin G than by minimal inhibitory concentration. CONCLUSION: Universal susceptibility of group B streptococcus to members of the penicillin family supports the continued use of penicillin G or ampicillin for early onset neonatal group B streptococcal disease prevention. For patients allergic to beta-lactam agents, clindamycin (4% resistance) may be a better alternative than erythromycin (21% resistance). 相似文献
110.