全文获取类型
收费全文 | 7813篇 |
免费 | 115篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 3篇 |
化学工业 | 422篇 |
金属工艺 | 69篇 |
机械仪表 | 54篇 |
建筑科学 | 28篇 |
矿业工程 | 4篇 |
能源动力 | 61篇 |
轻工业 | 304篇 |
水利工程 | 8篇 |
石油天然气 | 19篇 |
无线电 | 104篇 |
一般工业技术 | 252篇 |
冶金工业 | 6409篇 |
原子能技术 | 11篇 |
自动化技术 | 156篇 |
出版年
2024年 | 7篇 |
2023年 | 16篇 |
2022年 | 56篇 |
2021年 | 87篇 |
2020年 | 48篇 |
2019年 | 66篇 |
2018年 | 63篇 |
2017年 | 78篇 |
2016年 | 61篇 |
2015年 | 37篇 |
2014年 | 69篇 |
2013年 | 127篇 |
2012年 | 95篇 |
2011年 | 103篇 |
2010年 | 89篇 |
2009年 | 79篇 |
2008年 | 78篇 |
2007年 | 52篇 |
2006年 | 48篇 |
2005年 | 53篇 |
2004年 | 34篇 |
2003年 | 52篇 |
2002年 | 21篇 |
2001年 | 16篇 |
2000年 | 21篇 |
1999年 | 218篇 |
1998年 | 2022篇 |
1997年 | 1119篇 |
1996年 | 804篇 |
1995年 | 419篇 |
1994年 | 348篇 |
1993年 | 383篇 |
1992年 | 47篇 |
1991年 | 91篇 |
1990年 | 56篇 |
1989年 | 73篇 |
1988年 | 71篇 |
1987年 | 69篇 |
1986年 | 70篇 |
1985年 | 54篇 |
1983年 | 7篇 |
1982年 | 27篇 |
1981年 | 38篇 |
1980年 | 62篇 |
1979年 | 7篇 |
1978年 | 17篇 |
1977年 | 136篇 |
1976年 | 315篇 |
1975年 | 11篇 |
1955年 | 5篇 |
排序方式: 共有7929条查询结果,搜索用时 562 毫秒
991.
992.
Unilateral hyphema, hematuria, and ecchymoses developed in a previously healthy 42-year-old women after the ingestion of aspirin and ethanol. There was no evidence for ocular trauma, disease, or vascular malformation by slit-lamp examination and gonioscopy. Platelet count and coagulation tests were normal. The patient's bleeding time was prolonged and there was impaired platelet aggregation. Delayed (secondary) aggregation in response to collagen, adenosine diphosphate, and epinephrine was decreased, as was aggregation induced by thrombin and serotonin. These data indicate that the qualitative platelet defect was induced by both aspirin and ethanol. Anterior chamber hemorrhage subsided after discontinuation of aspirin and ethanol, and the hyphema subsequently resolved. Bleeding time and platelet aggregation were normal two weeks after the patient's initial presentation. A prolonged bleeding time in association with normal platelet count, prothrombin time, and partial thromboplastin time indicated a qualitative platelet defect, which is most commonly drug-induced. Defective platelet function resulted in spontaneous hyphema. 相似文献
993.
Identification and fractionation of plant histones 总被引:4,自引:0,他引:4
994.
Three patients with the rare association of secundum ASD and congenital clefts of A-V valves are reported. These three patients illustrate the predictive valve of vectoracardiographic analysis in precisely determining the anatomic location of the valvular pathology. The embryologic origins of the lesion are briefly discussed. A review of the literature supports the use of vector analysis in the evaluation of the patients with this type of heart disease. 相似文献
995.
Experience gained from the treatment of 41 patients with 42 operations for the relief of Vth nerve pain over the past 5 years is reported. For the selective section of the posterior root of the trigeminal nerve 28 retrolabyrinthine procedures were performed for typical tic douloureux with complete lasting relief in 25; 1 was relieved with the addition of aspirin; and 2 were relieved by Tegratol even though it was ineffective before surgery. There were no deaths and no serious complications. None had facial paralysis or anesthesia dolorosa. The retrolabyrinthine approach to the posterior root of the trigeminal nerve is ideally suited for those patients with refractory tic douloureux or patients with facial pain secondary to other causes such as tumor. Because of its effectiveness and low morbidity, this procedure offers advantages over other surgical techniques. 相似文献
996.
997.
998.
R Curtis JR Tonra JL Stark KM Adryan JS Park KD Cliffer RM Lindsay PS DiStefano 《Canadian Metallurgical Quarterly》1998,12(3):105-118
We investigated the retrograde axonal transport of 125I-labeled neurotrophins (NGF, BDNF, NT-3, and NT-4) from the sciatic nerve to dorsal root ganglion (DRG) sensory neurons and spinal motor neurons in normal rats or after neuronal injury. DRG neurons showed increased transport of all neurotrophins following crush injury to the sciatic nerve. This was maximal 1 day after sciatic nerve crush and returned to control levels after 7 days. 125I-BDNF transport from sciatic nerve was elevated with injection either proximal to the lesion or directly into the crush site and after transection of the dorsal roots. All neurotrophin transport was receptor-mediated and consistent with neurotrophin binding to the low-affinity neurotrophin receptor (LNR) or Trk receptors. However, transport of 125I-labeled wheat germ agglutinin also increased 1 day after sciatic nerve crush, showing that increased uptake and transport is a generalized response to injury in DRG sensory neurons. Spinal cord motor neurons also showed increased neurotrophin transport following sciatic nerve injury, although this was maximal after 3 days. The transport of 125I-NGF depended on the expression of LNR by injured motor neurons, as demonstrated by competition experiments with unlabeled neurotrophins. The absence of TrkA in normal motor neurons or after axotomy was confirmed by immunostaining and in situ hybridization. Thus, increased transport of neurotrophic factors after neuronal injury is due to multiple receptor-mediated mechanisms including general increases in axonal transport capacity. 相似文献
999.
P Rousseau JL Habrand D Sarrazin C Kalifa MJ Terrier-Lacombe C Rekacewicz A Rey 《Canadian Metallurgical Quarterly》1994,28(2):381-386
PURPOSE: There are still major controversies in the optimal management of children with intracranial ependymomas. To assess the impact of tumor site, histology, and treatment, the outcome of children treated at the Institut Gustave Roussy was reviewed retrospectively. METHODS AND MATERIALS: Between 1975 and 1989, 80 children aged 4 months to 15.8 years were seen at the Institut Gustave Roussy for postoperative management of an intracranial ependymoma. Location of tumor was infratentorial in 63 cases and supratentorial in 17. Surgical treatment consisted of complete resection in 38, incomplete resection in 38 and biopsy only in 4. Postoperative irradiation was done in 65 patients and chemotherapy in 33. Surviving patients have been followed from 12-197 months with a median of 54 months. RESULTS: The 5-year actuarial survival and event-free survival are 56% and 38%, respectively. Thirty-four patients relapsed from 3-72 months after diagnosis (median 25 months). In 20 patients, the only site of failure was the original tumor site. Three patients failed locally and at distance, while 10 others failed only at distance. Survival at 5 years was significantly better for patients who had complete resection of the tumor (75% vs. 41%, p = 0.001) and for those who received radiation therapy (63% vs. 23%, p = 0.003). Event-free survival at 5 years was superior in patients with complete resection of the tumor (51% vs. 26%, p = 0.002) and in patients who received radiation therapy (45% vs. 0%, p < 0.001). Sex and tumor site had no impact on survival or event-free survival. There was no difference in survival, event-free survival, or pattern of failure between patients treated with local field, whole brain or craniospinal irradiation, while severe longterm sequelae were noted predominantly in the latter two groups. CONCLUSION: Considering that failures were predominantly local and that there was no apparent benefit from prophylactic irradiation, we recommend local field irradiation with doses above 50.0 Gy for all children with intracranial ependymomas, without meningeal dissemination at diagnosis. Special considerations are necessary for children < 3 years of age. 相似文献
1000.