全文获取类型
收费全文 | 2465篇 |
免费 | 86篇 |
国内免费 | 61篇 |
专业分类
电工技术 | 64篇 |
综合类 | 137篇 |
化学工业 | 149篇 |
金属工艺 | 60篇 |
机械仪表 | 53篇 |
建筑科学 | 48篇 |
矿业工程 | 14篇 |
能源动力 | 36篇 |
轻工业 | 112篇 |
水利工程 | 25篇 |
石油天然气 | 12篇 |
武器工业 | 4篇 |
无线电 | 78篇 |
一般工业技术 | 86篇 |
冶金工业 | 1597篇 |
原子能技术 | 9篇 |
自动化技术 | 128篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 35篇 |
2021年 | 41篇 |
2020年 | 35篇 |
2019年 | 20篇 |
2018年 | 14篇 |
2017年 | 24篇 |
2016年 | 24篇 |
2015年 | 28篇 |
2014年 | 42篇 |
2013年 | 45篇 |
2012年 | 72篇 |
2011年 | 76篇 |
2010年 | 78篇 |
2009年 | 77篇 |
2008年 | 72篇 |
2007年 | 83篇 |
2006年 | 76篇 |
2005年 | 43篇 |
2004年 | 38篇 |
2003年 | 30篇 |
2002年 | 25篇 |
2001年 | 33篇 |
2000年 | 17篇 |
1999年 | 52篇 |
1998年 | 472篇 |
1997年 | 294篇 |
1996年 | 171篇 |
1995年 | 97篇 |
1994年 | 71篇 |
1993年 | 92篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 48篇 |
1976年 | 132篇 |
1975年 | 6篇 |
1955年 | 2篇 |
排序方式: 共有2612条查询结果,搜索用时 312 毫秒
21.
A polymerase chain reaction (PCR) technique for the identification of Shiga-like toxin (SLT)-producing Escherichia coli was assessed by using 95 strains of SLT-producing E. coli and 5 Shigella dysenteriae type 1 strains. PCR was used for the amplification of slt gene sequences from whole bacterial colonies. A digoxigenin-labeled DNA probe was used for identification of the PCR products in a spot blot hybridization assay. Modifications were made to adapt this technique for the proper identification of 10 SLT-producing isolates which were refractory to the heat lysis step that was used to liberate whole-cell DNA for PCR and 6 isolates which gave nonspecific amplification products. The sensitivity and specificity of this assay were each 99% when compared with toxin neutralization results by using SLT-specific monoclonal antibodies. These values indicate that this detection technique could be suitable for use in a clinical laboratory. 相似文献
22.
23.
S el-Shoura A Sheikha M al-Janadi N Morad AR Khan A Westmuckett 《Canadian Metallurgical Quarterly》1993,34(4):259-264
The ultrastructural features of histiocytes in the bone marrow (BM) were studied in a febrile, splenomegalic and pancytopenic Sudanese patient who was diagnosed by one of us as visceral leishmaniasis (VL) associated with low level of parasitaemia and mimicking malignant histiocytosis (MH). Serial thick (STS) and ultrathin (SUT) sections showed that the BM was hypercellular and markedly infiltrated by large histiocytes with prominent phagocytosis. A thorough examination of various ST and UT section revealed only a single, typical Leishman-Donovan body. At transmission electron microscopy (TEM) level, two principal types of histiocytic cells were identified: Type I, subdivided into two subtypes, were actively phagocytic histiocytes (PH) with large digestive vacuoles and primary lysosomes; type II were nonphagocytic histiocytes (nPH) with primary lysosomes only. The rate of PH to nPH ws 7:2 in plastic STS. The interaction between the PH and ingested cells is described. Both types of cell were morphologically similar to previously described malignant histiocytic cells. However, this study showed a better characterization of PH during VL. 相似文献
24.
W Cao M Britos-Bray DF Claxton CA Kelley NA Speck PP Liu AD Friedman 《Canadian Metallurgical Quarterly》1997,15(11):1315-1327
CBF beta-SMMHC is expressed from the inv(16) chromosome in M4Eo AML. Mice lacking CBF subunits or expressing the CBF beta-SMMHC or AML1-ETO oncoproteins failed to develop definitive hematopoiesis. To investigate these effects on hematopoiesis, we expressed CBF beta-SMMHC from the metallothionein promoter, in both 32D cl3 myeloid cells and Ba/F3 B-lymphoid cells. Addition of zinc increased CBF beta-SMMHC levels more than tenfold, with higher levels evident in Ba/F3 lines. Levels obtained in 32D cl3 cells were similar to those of endogenous CBF beta. Indirect immunofluorescence revealed zinc-inducible speckled, nuclear staining in Ba/F3 cells and diffuse nuclear staining in 32D cl3 cells. CBF beta-SMMHC reduced endogenous CBF DNA-binding fivefold in both cell types, increased cell generation time 1.9-fold, on average, in 32D cl3 cells and 1.5-fold in Ba/ F3 cells and decreased tritiated thymidine incorporation into DNA correspondingly. CBF beta-SMMHC increased the proportion of cells in G1 1.7-fold, on average, in 32D cl3 and Ba/F3 cells, and decreased the proportion of cells in S phase by a similar degree. CBF beta-SMMHC induced a marked increase in hypophosphorylated Rb, but did not alter IL-3 Receptor alpha or beta subunit levels. Neither apoptosis nor 32D differentiation was induced by zinc in IL-3 in these lines. Induction of CBF beta-SMMHC in 32D cl3 cells did not inhibit their differentiation to neutrophils or their expression of myeloperoxidase mRNA in G-CSF, and did not produce an eosinophilic phenotype. Additional, proliferative genetic changes in M4eo AMLs might potentiate inhibition of differentiation by CBF beta-SMMHC by allowing its increased expression. 相似文献
25.
26.
TK Cherniaeva NA Matveeva IuG Kuzmichev MP Gracheva 《Canadian Metallurgical Quarterly》1997,36(3):26-28
Nuchal screening has the following advantages: Non invasive. First trimester procedure. Results are obtained quickly. 80-90% detection rate for Down's Syndrome. 相似文献
27.
SF Ding JD Delhanty JS Dooley L Bowles CB Wood NA Habib 《Canadian Metallurgical Quarterly》1993,17(3):405-409
We have previously shown that the tumor suppressor gene for hepatocellular carcinoma (HCC) without cirrhosis may be located on chromosome 5q35-qter. In this study, we analyzed nine cases of primary HCC without cirrhosis using probes from the MCC and APC genes, which are in the region 5q21-22. None of the informative cases had allele loss detected by these probes, whereas the probe lambda MS8 for the region 5q35-qter showed allele loss in six out of six informative cases. The results confirm that the putative tumor suppressor gene for HCC without cirrhosis on chromosome 5q is distinct from the MCC and APC genes. 相似文献
28.
29.
30.
DJ Benos BH Hahn JK Bubien SK Ghosh NA Mashburn MA Chaikin GM Shaw EN Benveniste 《Canadian Metallurgical Quarterly》1994,91(2):494-498
Infection by human immunodeficiency virus type 1 (HIV-1) is often complicated by a variety of neurological abnormalities. The most common clinical syndrome, termed acquired immunodeficiency syndrome (AIDS) dementia complex, presents as a subcortical dementia with cognitive, motor, and behavioral disturbances and is unique to HIV-1 infection. The pathogenesis of this syndrome is poorly understood but is believed to involve interactions among virally infected macrophages/microglia, astrocytes, and neurons. In this study, we show that exposure of primary rat and human astrocytes to heat-activated HIV-1 virions, or to eukaryotically expressed HIV-1 and HIV-2 envelope glycoproteins (gp120) stimulates amiloride-sensitive Na+/H+ antiport, potassium conductance, and glutamate efflux. These effects are blocked specifically by amiloride, an inhibitor of Na+/H+ antiport and by the selective removal of gp120 with immobilized monoclonal antibody. As a result of modulation of astrocytic function by gp120, the ensuing neuronal depolarization and glutamate exposure could activate both voltage-gated and N-methyl-D-aspartate-regulated Ca2+ channels, leading to increases in intraneuronal Ca2+ and neuronal death. These findings implicate the astrocyte directly in the pathogenesis of AIDS dementia complex. 相似文献