全文获取类型
收费全文 | 3911篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 3篇 |
综合类 | 9篇 |
化学工业 | 21篇 |
金属工艺 | 9篇 |
机械仪表 | 15篇 |
建筑科学 | 12篇 |
矿业工程 | 5篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
水利工程 | 4篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 17篇 |
一般工业技术 | 30篇 |
冶金工业 | 3761篇 |
原子能技术 | 1篇 |
自动化技术 | 27篇 |
出版年
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 39篇 |
2006年 | 4篇 |
2005年 | 19篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 7篇 |
1999年 | 138篇 |
1998年 | 1232篇 |
1997年 | 665篇 |
1996年 | 454篇 |
1995年 | 253篇 |
1994年 | 206篇 |
1993年 | 237篇 |
1992年 | 29篇 |
1991年 | 41篇 |
1990年 | 46篇 |
1989年 | 48篇 |
1988年 | 37篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 29篇 |
1983年 | 3篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 62篇 |
1976年 | 147篇 |
1975年 | 1篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1962年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有3932条查询结果,搜索用时 468 毫秒
151.
Breda virus (BRV), a member of the genus torovirus, is an established etiological agent of diarrhea of cattle, which is found as two separate serotypes, BRV-1 and BRV-2. In this study, a 7.5 kb fragment of the BRV-1 genome that bracketed the genes for the structural proteins of BRV was amplified by long RT-PCR and the amplicon purified and sequenced directly. Sequence analysis revealed the presence of four open reading frames (ORF) corresponding to the peplomer (S), envelope (M), and nucleocapsid (N) genes, and an ORF for a novel 1.2 kb gene located between the M and N genes. This new gene was identical in nucleotide sequence to the hemagglutinin-esterase (HE) gene of BRV-2. With the exception of this new ORF, BRV-1 manifests 80% nucleotide sequence identity with the torovirus prototype, Berne virus (BEV) in the 7.5 kb region from the 3' end of the genome that contains the genes for the structural proteins. A 504 base segment containing the ORF for the BRV-1 N gene was amplified by RT-PCR, and cloned into an Escherichia coli expression system. The resulting protein was purified by SDS-PAGE and used to immunize guinea pigs. Hyperimmune serum was reactive with bovine torovirus (BTV) and human torovirus (HTV) antigens. By immunoelectron microscopy, it was shown to aggregate broken but not intact torovirus particles from BTV-positive fecal specimens. By immunoblot, the hyperimmune serum reacted specifically with the 20 kD N proteins of both BTV and HTV, as well as with the expressed N protein. BRV-1 and BRV-2 immune sera from gnotobiotic calves, but not human convalescent sera from HTV-infected patients, reacted with the expressed N protein by immunoblot. These findings were applied to the design of a dot blot assay that could specifically detect BTV and HTV from fecal specimens. 相似文献
152.
CA Uyl-de Groot B L?wenberg E Vellenga S Suciu R Willemze FF Rutten 《Canadian Metallurgical Quarterly》1998,100(4):629-636
The acute hemodynamic effects of the phosphodiesterase (PDE) III inhibitor saterinone were compared with dobutamine and sodium nitroprusside in 12 patients with idiopathic congestive cardiomyopathy (NYHA III). Hemodynamic measurements were obtained with a Swan-Ganz thermodilution catheter. At the peak of its dose-response curve, saterinone induced an increase in cardiac index (+102%), stroke volume (+97%), and heart rate (+6%), paralleled by a decrease in pulmonary capillary wedge pressure (-46%), right atrial pressure (-51%), pulmonary arterial pressure (systolic -32%, diastolic -45%, mean -38%), systemic blood pressure (systolic -3%, diastolic -13%, mean -9%), systemic vascular resistance (-54%), and pulmonary vascular resistance (-58%). Dobutamine had similar effects on cardiac index (+106%) and stroke volume (+87%) but lacked vasodilatory characteristics. In contrast to dobutamine, both nitroprusside and saterinone demonstrated more pronounced vasodilatory effects. Nitroprusside was less effective on cardiac index (+66%) and stroke volume (+56%) than was saterinone. The double product was markedly increased by dobutamine (+28%), did not change with saterinone treatment (+2%), and decreased with nitroprusside (-10%). This indicates that according to double product, only the application of dobutamine caused a relevant increase in myocardial oxygen consumption. Saterinone was demonstrated to be a safe and potent drug on short-term application; it combines the vasodilating properties of sodium nitroprusside with the positive inotropic effects of dobutamine without major changes in myocardial oxygen consumption. 相似文献
153.
Congenital abnormalities in Brazilian children associated with misoprostol misuse in first trimester of pregnancy 总被引:1,自引:0,他引:1
CH Gonzalez MJ Marques-Dias CA Kim SM Sugayama JA Da Paz SM Huson LB Holmes 《Canadian Metallurgical Quarterly》1998,351(9116):1624-1627
BACKGROUND: Misoprostol is commonly used to induce abortion in Brazil, and in other countries in South and Central America where abortions are illegal. However, misoprostol is not very effective in inducing abortions, and exposure to the drug in utero can cause abnormalities in the fetus. We aimed to define the common phenotypical effects of exposure to the drug. METHODS: We studied 42 infants from S?o Paulo, Brazil, who were exposed to misoprostol during the first 3 months of gestation, and then born with congenital abnormalities. We interviewed each of the infants' mothers to find out about misoprostol exposure and dosage. Each infant was physically examined by a geneticist or a neuropaediatrician. FINDINGS: 17 of the infants had equinovarus with cranial-nerve defects. Ten children had equinovarus as part of more extensive arthrogryposis. The most distinctive phenotypes were arthrogryposis confined to the legs (five cases) and terminal transverse-limb defects (nine cases) with or without Mobius sequence. The most common dose of misoprostol taken was 800 microg (range 200-16000 microg). INTERPRETATION: Deformities attributed to vascular disruption were found in these children. We suggest that the uterine contractions induced by misoprostol cause vascular disruption in the fetus, including brain-stem ischaemia. Information on the effects of taking misoprostol during pregnancy should be made more widely available, to dissuade women from misusing the drug. 相似文献
154.
155.
156.
157.
BR Lúdvíksson MC Sneller KS Chua C Talar-Williams CA Langford RO Ehrhardt AS Fauci W Strober 《Canadian Metallurgical Quarterly》1998,160(7):3602-3609
Wegener's granulomatosis (WG) is a granulomatous vasculitis that affects the upper respiratory tract, lung, and kidney. Since T cells make up a significant proportion of cells infiltrating granulomatous lesions in WG, we investigated the proliferative response and cytokine profile of T cells from these patients. PBMCs were isolated from 12 patients with active WG, 7 patients with inactive disease, and 12 healthy normal donors. PBMCs from clinically active WG patients exhibited increased proliferation following stimulation with either PMA/ionomycin or anti-CD2 and anti-CD28, when compared with normal donors. In addition, these PBMCs exhibited increased secretion of IFN-gamma, but not of IL-4, IL-5, or IL-10. Furthermore, TNF-alpha production from PBMCs and CD4+ T cells isolated from patients with WG was elevated, when compared with healthy donors. In further studies, we investigated the ability of WG patients' monocytes to produce IL-12 and showed that both inactive and active patients produced increased amounts of IL-12. Finally, the in vitro IFN-gamma production by WG PBMC is inhibited in a dose-dependent manner by exogenous IL-10. These data suggest that T cells from WG patients overproduce IFN-gamma and TNF-alpha, probably due to dysregulated IL-12 secretion, and that IL-10 may therefore have therapeutic implications for this disease. 相似文献
158.
159.
160.
Ca2+ entry under resting conditions may be important for contraction of vascular smooth muscle, but little is known about the mechanisms involved. Ca2+ leakage was studied in the A7r5 smooth muscle-derived cell line by patch-clamp techniques. Two channels that could mediate calcium influx at resting membrane potentials were characterized. In 110 mM Ba2+, one channel had a slope conductance of 6.0 +/- 0.6 pS and an extrapolated reversal potential of +41 +/- 13 mV (mean +/- SD, n = 8). The current rectified strongly, with no detectable outward current, even at +90 mV. Channel gating was voltage independent. A second type of channel had a linear current-voltage relationship, a slope conductance of 17.0 +/- 3.2 pS, and a reversal potential of +7 +/- 4 mV (n = 9). The open probability increased e-fold per 44 +/- 10 mV depolarization (n = 5). Both channels were also observed in 110 mM Ca2+. Noise analysis of whole-cell currents indicates that approximately 100 6-pS channels and 30 17-pS channels are open per cell. These 6-pS and 17-pS channels may contribute to resting calcium entry in vascular smooth muscle cells. 相似文献