全文获取类型
收费全文 | 1961篇 |
免费 | 31篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 1993篇 |
出版年
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 21篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 30篇 |
2013年 | 60篇 |
2012年 | 30篇 |
2011年 | 38篇 |
2010年 | 34篇 |
2009年 | 27篇 |
2008年 | 32篇 |
2007年 | 40篇 |
2006年 | 29篇 |
2005年 | 43篇 |
2004年 | 27篇 |
2003年 | 32篇 |
2002年 | 24篇 |
2001年 | 25篇 |
2000年 | 10篇 |
1999年 | 47篇 |
1998年 | 389篇 |
1997年 | 195篇 |
1996年 | 124篇 |
1995年 | 97篇 |
1994年 | 81篇 |
1993年 | 72篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 27篇 |
1976年 | 52篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1965年 | 4篇 |
排序方式: 共有1993条查询结果,搜索用时 0 毫秒
91.
OBJECTIVES: To assess the comparability of the Hybritech Tandem-R and Abbott AxSYM PSA assays in the setting of a hospital laboratory changing methods of PSA assay. METHODS: A total of 115 serum samples were tested simultaneously with both reagent kits. These include samples from patients evaluated for screening, benign prostatic hyperplasia, and follow-up of prostate cancer. RESULTS: The outcomes of the Hybritech Tandem-R PSA test ranged from 0.0 to 48.3 ng/mL with a median value of 2.4 ng/mL (mean 3.48, SD 5.46). The outcomes of the Abbott AxSYM PSA test ranged from 0.0 to 49.33 ng/mL with a median of 2.22 ng/mL (mean 3.82, SD 5.59). The outcomes of the two assays were found to be highly correlated by the Pearson correlation coefficient (r = 0.9942). When samples were divided according to PSA levels of 0.0 to less than 2.5, 2.5 to less than 4.0, 4.0 to less than 10.0, and 10.0 to less than 25.0 ng/mL, the outcomes were also highly correlated in all PSA level ranges (r = 0.9619, 0.8094, 0.9167, and 0.9081, respectively). CONCLUSIONS: The PSA values of the Tandem-R and Abbott AxSYM assays are highly correlated in the PSA level ranges of 0.0 to less than 2.5, 2.5 to less than 4.0, 4.0 to less than 10.0, and 10.0 to less than 25.0 ng/mL. 相似文献
92.
PJ Simpson-Haidaris MA Courtney TW Wright R Goss A Harmsen F Gigliotti 《Canadian Metallurgical Quarterly》1998,66(9):4431-4439
Pneumocystis carinii is an important pulmonary pathogen responsible for morbidity and mortality in patients with AIDS. The acute-phase response (APR), the primary mechanism used by the body to restore homeostasis following infection, is characterized by increased levels of circulating fibrinogen (FBG). Although the liver is the primary site of increased FBG synthesis during the APR, we unexpectedly discovered that FBG is synthesized and secreted by lung alveolar epithelial cells in vitro during an inflammatory stimulus. Therefore, we sought to determine whether lung epithelial cells produce FBG in vivo using animal models of P. carinii pneumonia (PCP). Inflammation was noted by an influx of macrophages to P. carinii-infected alveoli. Northern hybridization revealed that gamma-FBG mRNA increased two- to fivefold in P. carinii-infected lung tissue, while RNA in situ hybridization demonstrated increased levels of gamma-FBG mRNA in the lung epithelium. Immunoelectron microscopy detected lung epithelial cell-specific production of FBG, suggesting induction of a localized inflammatory response resembling the APR. A systemic APR was confirmed by a two- to fivefold upregulation of the levels of hepatic gamma-FBG mRNA in animals with PCP, resulting in a corresponding increase in levels of FBG in plasma. Furthermore, immunoelectron microscopy revealed the presence of FBG at the junction of cell membranes of trophic forms of P. carinii organisms aggregated along the alveolar epithelium. These results implicate FBG in the pathogenesis of PCP in a manner similar to that of the adhesive glycoproteins fibronectin and vitronectin, which are known to participate in intra-alveolar aggregation of organisms and adherence of P. carinii to the lung epithelium. 相似文献
93.
K Hoogenberg WJ Sluiter G Navis TW Van Haeften AJ Smit WD Reitsma RP Dullaart 《Canadian Metallurgical Quarterly》1998,9(4):643-654
Exogenous norepinephrine (NE) increases intraglomerular pressure in animal experiments, but it is unknown whether NE induces a microproteinuric response in humans. Moreover, it has not been studied whether possible microproteinuric and renal hemodynamic changes induced by NE are altered in insulin-dependent diabetes mellitus (IDDM) complicated by microalbuminuria. Therefore, the microproteinuric and renal hemodynamic responses to exogenous NE infusions were measured in eight matched normoalbuminuric IDDM patients (group D1), microalbuminuric IDDM patients (group D2), and control subjects (group C). As anticipated, mean arterial pressure (MAP)-NE dose-response curves were significantly shifted leftward in groups D1 and D2 compared with group C (P < 0.05), indicating a higher systemic NE responsiveness in IDDM. On separate days, NE or placebo was infused at individually determined NE threshold doses (T; delta MAP = 0 mmHg), 20% pressor doses (20% P; delta MAP = 4 mmHg), and pressor doses (P; delta MAP = 20 mmHg), with measurement of urinary albumin (UalbV), IgG excretion (UIgGV), GFR (by 125I-iothalamate), and effective renal plasma flow (by 131I-hippurate). At NE pressor dose, UalbV and UIgGV rose in all groups (P < 0.05 to 0.01), whereas urinary beta 2-microglobulin was unchanged. The increases in UalbV and UIgGV were more pronounced in the microalbuminuric group than in the other groups (P < 0.05). An NE dose-dependent fall in effective renal plasma flow and rise in filtration fraction were found in all groups (P < 0.05 to 0.001 for all), whereas GFR did not change significantly. The renal hemodynamic dose-response relationship was similar in the groups. In conclusion, exogenous NE acutely promotes glomerular protein leakage, and it is plausible that intraglomerular NE effects contribute to this phenomenon. The microproteinuric response is enhanced in microalbuminuric IDDM despite unaltered renal hemodynamic responsiveness, which may reflect a specific NE response or a general effect of vasopressor stimuli to promote glomerular protein leakage in patients with a preexistent defect in glomerular permselectivity. 相似文献
94.
DC McAvoy CP Grady J Blok TC Feijtel TW Federle RJ Larson 《Canadian Metallurgical Quarterly》1998,36(10):2291-2304
Various mathematical relationships have been used to assess exposure concentrations of organic chemicals when emissions occur via wastewater treatment. These relationships range from a simple removal factor calculation to more sophisticated approaches using kinetic based mathematical models. While these existing approaches have been used by decision makers to screen new chemicals for exposure assessments, they all have limitations in the predictive capabilities. Thus, a simplified modeling approach grounded in sound scientific fundamentals that utilizes relatively easy to obtain input parameters is needed. In this paper a simplified modeling approach that utilizes microbial growth kinetics was developed for predicting effluent concentrations in secondary biological wastewater treatment systems. Receiving water predicted exposure concentrations (PEC) are assessed by using a dilution factor. One advantage of this approach is that it allows for wastewater treatment plant effluent concentrations, and therefore receiving water exposure levels, to be predicted with a minimum amount of experimental data. It also provides quantitative data that can be used to assess the relative biodegradability of different chemicals for use in regulatory and risk assessment activities. 相似文献
95.
Twenty de novo patients with Parkinson's disease (Hoehn-Yahr stages I, II, III) were studied in a double blind trial after introducing (--)-deprenyl monotherapy. The parkinsonian symptoms were assessed by a novel graded clinical rating scale, by UPDRS and by the North Western self-rating scale. A significant change was observed in motor behaviour and daily activity (UPDRS) after 3 weeks of treatment with (--)-deprenyl at 10 mg/day. The total scores using UPDRS and the North Western ratings were changed significantly after 4 weeks. The greatest changes observed were in walking and in hypokinesia. Rigidity was not modified by (--)-deprenyl. 相似文献
96.
97.
98.
Phytochromes and cryptochromes in the entrainment of the Arabidopsis circadian clock 总被引:4,自引:0,他引:4
Circadian clocks are synchronized by environmental cues such as light. Photoreceptor-deficient Arabidopsis thaliana mutants were used to measure the effect of light fluence rate on circadian period in plants. Phytochrome B is the primary high-intensity red light photoreceptor for circadian control, and phytochrome A acts under low-intensity red light. Cryptochrome 1 and phytochrome A both act to transmit low-fluence blue light to the clock. Cryptochrome 1 mediates high-intensity blue light signals for period length control. The presence of cryptochromes in both plants and animals suggests that circadian input pathways have been conserved throughout evolution. 相似文献
99.
100.
Recognition that self-representation includes both social and personal identities raises questions about the cognitive organization of these elements. Two models of identity structure are compared: (a) a segregation model (D. Trafimow, H. C. Triandis, & S. G. Goto; see record 1991-24271-001), which assumes that (social) identities and (personal) attributes are two distinct categories, and (b) an integration model (K. Deaux, 1992), which proposes that identities and attributes often coexist in a limited set of cognitive structures. Clustering of self-relevant information in free recall was used to assess cognitive organization in a sample of 57 students. Identities and attributes clustered separately at greater-than-chance rates, consistent with the segregation model. More detailed analysis of recall data, in which individual patterns of association between identities and attributes were considered, provides stronger support for an integration model of self-representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献