全文获取类型
收费全文 | 1620篇 |
免费 | 4篇 |
专业分类
化学工业 | 10篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
轻工业 | 8篇 |
水利工程 | 1篇 |
一般工业技术 | 4篇 |
冶金工业 | 1592篇 |
自动化技术 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2011年 | 4篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 6篇 |
1999年 | 41篇 |
1998年 | 467篇 |
1997年 | 274篇 |
1996年 | 190篇 |
1995年 | 109篇 |
1994年 | 79篇 |
1993年 | 87篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1982年 | 6篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 45篇 |
1976年 | 104篇 |
1975年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有1624条查询结果,搜索用时 15 毫秒
251.
252.
253.
254.
RATIONALE AND OBJECTIVES: The authors characterize magnetic resonance (MR) features of oligodendroglioma that permit diagnosis. These features may be used to guide MR stereotactic biopsies. METHODS: Fifteen patients with mixed oligodendroglioma and four with pure oligodendroglioma were studied on a 1.5-tesla MR unit with contrast and also by computed tomography (CT). All patients had their diagnosis confirmed by light and electron microscopy, and by immunohistochemical staining. RESULTS: The most characteristic finding was a honeycomb tumor matrix (4 of 19) in oligodendroglioma. The most common finding was an amorphous pattern (12 of 19) and the least common was a large cystic pattern (3 of 19). Contrast enhancement most commonly was minimal and dot-like or lacy in appearance (11 of 19), or absent (5 of 19). Calcification was present in the majority (11 of 19). CONCLUSIONS: The honeycomb and stippled amorphous patterns reflect the cytoarchitecture of oligodendroglioma and were the most characteristic MR features. The amorphous pattern was the most commonly encountered pattern. There was a wider range of imaging findings on MR compared with CT; the flocculent calcification on CT was typical, but it was not always detected on MR. Including these characteristic areas that appear along the path of the stereotactic biopsy may ensure a correct diagnosis of oligodendroglioma because it most often is seen with another tumor, usually of the astrocytic family. Identifying the oligodendrogliomatous portion of the tumor will influence the therapy. No differences could be found in the MR appearance or biologic behavior of pure versus mixed oligodendrogliomas. 相似文献
255.
MP Scolnik MF Palacios SH Acevedo MV Castuma IB Larripa A Palumbo EB Moiraghi AM Sasot AB Huberman 《Canadian Metallurgical Quarterly》1998,31(1-2):231-236
The murine monoclonal antibody A7 (MAb A7) is reactive against most human gastric cancer cell lines. Using a nude mouse peritoneal dissemination model of human gastric cancer, we investigated targeted chemotherapy using a conjugate of neocarzinostatin (NCS) with MAb A7 (A7-NCS). After demonstrating cytotoxicity of the complex against the human gastric cancer cell line MKN45 in vitro, we intraperitoneally injected A7-NCS, NCS or saline into nude mice bearing peritoneally disseminated human gastric cancer. A7-NCS inhibited peritoneal dissemination significantly more effectively than NCS. MAb A7 may prove to be an effective carrier for antineoplastic drugs in patients with peritoneal dissemination of gastric cancer. 相似文献
256.
DR Duerksen JE Van Aerde L Gramlich JB Meddings G Chan AB Thomson MT Clandinin 《Canadian Metallurgical Quarterly》1996,111(4):1111-1117
BACKGROUND & AIMS: Cholestasis complicates total parenteral nutrition (TPN) in preterm infants. Ursodeoxycholic acid (UDCA) is used for several cholestatic problems. The hypothesis of this study was that intravenous UDCA prevents TPN-induced cholestasis by (1) maintaining normal basal and stimulated bile flow, (2) altering bile composition, and (3) changing hepatocyte membrane composition and Na+,K(+)-adenosine triphosphatase (ATPase) activity. METHODS: Three groups of piglets were studied: group 1 received sow's milk, groups 2 and 3 received TPN, and group 3 also received 100 mumol.kg-1.day-1 UDCA intravenously. After 3 weeks, basal and stimulated bile flow were measured. Cholesterol, bile acids, phospholipids, and phospholipid fatty acids were analyzed in bile, and fluidity, phospholipid fatty acid composition, and Na+,K(+)-ATPase were analyzed in hepatocyte membranes. RESULTS: Bile acid secretion and basal and stimulated bile flow were similar in control and UDCA-treated animals but reduced to < 50% in the TPN group. Bile acid-dependent and -independent bile flow were lower in the TPN group. UDCA did not normalize abnormalities in TPN-induced bile composition. Sinusoidal but not canalicular membrane fluidity was different in TPN than in control and UDCA-treated animals. UDCA also increased Na+,K(+)-ATPase activity. Bile and membrane phospholipid fatty acids reflected dietary fatty acids. CONCLUSIONS: Intravenous UDCA improves bile flow and reduces bilirubin levels in the serum and liver in piglets with TPN-induced cholestasis. 相似文献
257.
L Liu AB Jefferson X Zhang FA Norris PW Majerus G Krystal 《Canadian Metallurgical Quarterly》1996,271(47):29729-29733
To gain insight into the intracellular signaling cascades that are activated by the binding of interleukin-3 (IL-3) to its target cells, we have embarked on the identification of proteins that are associated with the IL-3 receptor (IL-3R). In a previous study we reported that a 110-kDa serine/threonine protein kinase is constitutively associated with the IL-3R and activated following IL-3 stimulation. We now report that a phosphatidylinositol-3,4, 5-trisphosphate (PtdIns-3,4,5-P3) 5-phosphatase (5-ptase) is also constitutively associated with the IL-3R. This 5-ptase is magnesium-dependent and removes the 5-position phosphate from PtdIns-3,4,5-P3 but does not metabolize PtdIns-4,5-P2, inositol (Ins)-1,3,4,5-P4, or Ins-1,4,5-P3. This substrate specificity distinguishes it from any previously characterized 5-ptase. Interestingly, it may be bound indirectly via phosphatidylinositol 3-kinase (PI 3-kinase), another enzyme that is constitutively bound to the IL-3R. However, unlike PI 3-kinase which becomes activated following IL-3 stimulation, this receptor-associated 5-ptase activity does not increase following IL-3 stimulation, and its primary function may be to keep the principal in vivo product of PI 3-kinase, PtdIns-3,4,5-P3, at low levels in unstimulated cells, to terminate the PI 3-kinase signal following IL-3 stimulation or to metabolize PtdIns-3,4,5-P3 to a metabolically active second messenger, i.e. PtdIns-3,4-P2. 相似文献
258.
259.
260.
AB Swanson G de Groot Swanson DH DeHeer TD Pierce K Randall JM Smith CC Van Gorp 《Canadian Metallurgical Quarterly》1997,(342):46-58
In 1984, in an effort to address the silicone wear particle problem, titanium implants were developed for the scaphoid, lunate, and trapeziometacarpal joint. The design of these implants closely resembled their silicone counterparts, though some modifications were made to accommodate the properties of unalloyed titanium and enhance their stability. Carpal bone implants act as articulating spacers to help maintain the relationship of adjacent carpal bones after local resection procedures. Their use allows carpal stabilization procedures and provides functional mobility with good strength and pain relief. Their surgical application began in 1985. The 10-year clinical experience seems very promising to date. 相似文献