全文获取类型
收费全文 | 4616篇 |
免费 | 16篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 4634篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 15篇 |
2012年 | 32篇 |
2011年 | 22篇 |
2010年 | 22篇 |
2009年 | 16篇 |
2008年 | 25篇 |
2007年 | 10篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 130篇 |
1998年 | 1239篇 |
1997年 | 683篇 |
1996年 | 499篇 |
1995年 | 240篇 |
1994年 | 221篇 |
1993年 | 235篇 |
1992年 | 38篇 |
1991年 | 82篇 |
1990年 | 70篇 |
1989年 | 66篇 |
1988年 | 64篇 |
1987年 | 61篇 |
1986年 | 45篇 |
1985年 | 58篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1982年 | 31篇 |
1981年 | 31篇 |
1980年 | 42篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 117篇 |
1976年 | 270篇 |
1975年 | 13篇 |
1956年 | 2篇 |
1955年 | 7篇 |
1911年 | 2篇 |
排序方式: 共有4634条查询结果,搜索用时 0 毫秒
991.
992.
J van den Born LP van den Heuvel MA Bakker JH Veerkamp KJ Assmann JH Berden 《Canadian Metallurgical Quarterly》1994,42(1):89-102
We raised monoclonal antibodies (MAb) against the core protein and the heparan sulfate (HS) side chain of heparan sulfate proteoglycan (HSPG) from glomerular basement membranes (GBM). Anti-HSPG-core MAb were obtained after immunization of mice with HSPG purified from human GBM and the anti-HS MAb after immunization of mice with HSPG from rat glomeruli, which crossreacted with human HS and GBM HSPG. The specificity of the MAb was demonstrated by ELISA studies, Western blotting, inhibition experiments, and indirect immunofluorescence (IF) on kidney cryostat sections pre-treated with glycosaminoglycan (GAG)-degrading enzymes. Indirect IF on normal human kidney tissue showed prominent GBM staining for both MAb, with variable staining of the other renal basement membranes (BMs). By indirect immunoelectron microscopy (IEM), most intense staining was observed at the endothelial side of the GBM for both MAb, although the staining patterns were not identical. Both MAb were used to localize HSPG in human tissues by indirect IF. They bound to antigens present in the BMs of most tissues examined, including those of epithelia and endothelia. Differences between both MAb were observed for BMs of muscle cells, since the anti-HSPG core protein MAb (JM-72) staining was negative, whereas the anti-HS MAb (JM-403) clearly stained these structures. Comparison of our staining patterns in human tissues with the distribution of other anti-BM HSPG antibodies suggests that there are at least two types of BM HSPG, which have common epitopes on the HS side chains recognized by JM-403. 相似文献
993.
994.
995.
Although in vitro analyses of long-term changes in the sensorimotor connection of Aplysia have been used extensively to understand long-term sensitization, relatively little is known about the ways in which the connection is modified by learning in vivo. Moreover, sites other than the sensory neurons might be modified as well. In this paper, several different biophysical properties of sensory neurons, motor neurons, and LPl17, an identified interneuron, were examined. Membrane properties of sensory neurons, which were expressed as increased excitability and increased spike afterdepolarization, were affected by the training. The biophysical properties of motor neurons also were affected by training, resulting in hyperpolarization of the resting membrane potential and a decrease in spike threshold. These results suggest that motor neurons are potential loci for storage of the memory in sensitization. The strength of the connection between sensory and motor neurons was affected by the training, although the connection between LPl17 and the motor neuron was unaffected. Biophysical properties of LPl17 were unaffected by training. The results emphasize the importance of plasticity at sensory-motor synapses and are consistent with the idea that there are multiple sites of plasticity distributed throughout the nervous system. 相似文献
996.
WG Beamer KL Shultz BJ Tennent JH Nadeau GA Churchill EM Eicher 《Canadian Metallurgical Quarterly》1998,58(16):3694-3699
Spontaneous juvenile ovarian granulosa cell (GC) tumors that occur in young girls are similar to GC carcinomas that develop in SWR-derived inbred mice. We analyzed female offspring from a series of matings among SWR and SJL inbred mice for chromosomal loci underlying tumor susceptibility. Intercross F2 female mice were produced by reciprocal matings of (SWR x SJL)F1 and (SJL x SWR)F1 parents. Tumorigenesis in these F2 mice as well as in SWXJ recombinant inbred and congenic strains of mice derived from SWR and SJL showed significant (P < 0.001) association with Gct1, a dominant susceptibility locus on chromosome (CHR) 4 and with Gct2 on CHR 12. Suggestive (P < 0.01) association was found with Gct3 on CHR 15. A fourth susceptibility locus, Gct4 on CHR X, was demonstrated with a strong parent-of-origin effect associated with the paternal genotype. Imprinting and complex interactions among these four loci combine to establish the probability for GC tumorigenesis in this mouse model. 相似文献
997.
M Norredam M Groenvold JH Petersen A Krasnik 《Canadian Metallurgical Quarterly》1998,47(11):1659-1663
This study examines the effect of socio-economic inequalities on the tumour size at diagnosis and the choice of surgical treatment in Danish women with breast cancer. The Danish Breast Cancer Cooperative Group (DBCG) registers all women with breast cancer in Denmark and provides clinical register data on tumour size and surgical treatment for 1594 women <75 yr diagnosed with breast cancer between 1991 and 1996. A questionnaire including questions on social class was sent to the women. The tumour size at diagnosis (an indicator of access to treatment) and the surgical procedure (lumpectomy or mastectomy) for patients who were potential candidates for lumpectomy were the main outcome measures examined. Social class was not associated with tumour size at diagnosis. The tumour size was associated with age and the existence of a mammographic screening program in the county. However, treatment was strongly related to social class. Among women considered candidates for lumpectomy 77% underwent lumpectomy in the highest social class, compared to 50% in the lowest social class. Treatment was associated with age, tumour size and hospital status. It was concluded that the study showed no socio-economic inequalities related to access to health services as measured by tumour size, though significant social differences were found regarding treatment. 相似文献
998.
JH Rex JE Bennett AM Sugar PG Pappas CM van der Horst JE Edwards RG Washburn WM Scheld AW Karchmer AP Dine 《Canadian Metallurgical Quarterly》1994,331(20):1325-1330
BACKGROUND: Amphotericin B has long been the standard treatment for candidemia, but its use is complicated by its toxicity. More recently, fluconazole, a water-soluble triazole with activity against candida species and little toxicity, has become available. We conducted a multicenter randomized trial that compared amphotericin B with fluconazole as treatment for candidemia. METHODS: To be eligible, patients had to have a positive blood culture for candida species, a neutrophil count > or = 500 per cubic millimeter, and no major immunodeficiency. Patients were randomly assigned to receive either amphotericin B (0.5 to 0.6 mg per kilogram of body weight per day) or fluconazole (400 mg per day), each continued for at least 14 days after the last positive blood culture. Outcomes were assessed by a group of investigators blinded to treatment assignment. RESULTS: Of the 237 patients enrolled, 206 met all entry criteria. The most common diagnoses were renal failure, nonhematologic cancer, and gastrointestinal disease. There was no statistically significant difference in outcome: of the 103 patients treated with amphotericin B, 81 (79 percent) were judged to have been treated successfully, as were 72 of the 103 patients treated with fluconazole (70 percent P = 0.22; 95 percent confidence interval for the difference, -5 to 23 percent). The bloodstream infection failed to clear in 12 patients in the amphotericin group and 15 in the fluconazole group; the species most commonly associated with failure was Candida albicans. There were 41 deaths in the amphotericin group and 34 deaths in the fluconazole group (P = 0.20). Intravascular catheters appeared to be the most frequent source of candidemia. There was less toxicity with fluconazole than with amphotericin B. CONCLUSIONS: In patients without neutropenia and without major immunodeficiency, fluconazole and amphotericin B are not significantly different in their effectiveness in treating candidemia. 相似文献
999.
Under normal physiologic conditions the level of circulating red blood cells is regulated precisely by the glycoprotein erythropoietin. In major elective surgery, patients who are participating in preoperative autologous blood donation or who are anemic may not have the capacity to manufacture sufficient red blood cells in response to increases in endogenous erythropoietin that is sufficient to avoid perioperative allogeneic blood transfusion. In these patients pharmacologic doses of recombinant human erythropoietin (Epoetin alfa) have been shown to accelerate erythropoiesis, thereby increasing preoperative red blood cell production, hematocrit level, and hemoglobin concentration and reducing exposure to allogeneic blood transfusion. In four large multicenter studies, 869 patients undergoing major elective surgery were treated with a daily regimen (300 or 100 IU/kg x 14 or 15 doses) or a weekly regimen (600 IU/kg x 4 doses) of subcutaneous Epoetin alfa beginning either 2 or 3 weeks before surgery, respectively. Although all Epoetin alfa regimens were effective at accelerating erythropoiesis and increasing red blood cell production, the weekly regimen was the most patient friendly, cost effective regimen for treating preoperative anemia and minimizing patient risk of allogeneic blood transfusion. 相似文献
1000.
S Ramcharan PL Meenhorst JM Otten CH Koks D de Boer RA Maes JH Beijnen 《Canadian Metallurgical Quarterly》1998,36(7):727-731
This study was designed to evaluate the potential advantages of combined epidural and light general anesthesia over the commonly employed general anesthesia during open heart surgery. Twenty-four patients undergoing mitral valve replacement were thus studied. General anesthesia was maintained with an isoflurane-nitrous oxide-oxygen was mixture and morphine sulfate (0.4 mg/kg i.v. initially) followed by postoperative pain control with morphine in 12 patients (group GA). The remaining 12 patients (group EAA) received continuous epidural bupivacaine (0.125%)-morphine (50 micrograms/ml) supplemented with the same gas mixture as group GA. Epidural infusion was continued until the third postoperative day. Changes in the serum cortisol and beta-endorphin levels together with postoperative pain relief defined as good (scale 0-2), fair (3-4), or poor (5-10) were observed serially. Lower cortisol levels were observed in group EAA than in group GA (P < 0.05) just before skin closure, on the second and the third postoperative day. The beta-endorphin levels were substantially lower in group EAA than in group GA throughout the observation. The pain scores were good in 2 patients (17%), fair in 6 (50%), and poor in 4 (33%) for group GA, and good in 8 (67%), fair in 3 (25%), and poor in 1 (8%) for group EAA. We thus conclude that a combined epidural and light general anesthesia is considered to attenuate the stress response and thereby provides a better quality of postoperative pain control. 相似文献