全文获取类型
收费全文 | 26550篇 |
免费 | 2080篇 |
国内免费 | 2172篇 |
出版年
2024年 | 67篇 |
2023年 | 387篇 |
2022年 | 946篇 |
2021年 | 1562篇 |
2020年 | 1072篇 |
2019年 | 1326篇 |
2018年 | 1181篇 |
2017年 | 918篇 |
2016年 | 1236篇 |
2015年 | 1774篇 |
2014年 | 2087篇 |
2013年 | 2084篇 |
2012年 | 2476篇 |
2011年 | 2135篇 |
2010年 | 1358篇 |
2009年 | 1127篇 |
2008年 | 1258篇 |
2007年 | 1054篇 |
2006年 | 951篇 |
2005年 | 771篇 |
2004年 | 665篇 |
2003年 | 579篇 |
2002年 | 536篇 |
2001年 | 473篇 |
2000年 | 409篇 |
1999年 | 389篇 |
1998年 | 269篇 |
1997年 | 233篇 |
1996年 | 216篇 |
1995年 | 188篇 |
1994年 | 161篇 |
1993年 | 128篇 |
1992年 | 153篇 |
1991年 | 132篇 |
1990年 | 121篇 |
1989年 | 84篇 |
1988年 | 63篇 |
1987年 | 69篇 |
1986年 | 42篇 |
1985年 | 36篇 |
1984年 | 23篇 |
1983年 | 26篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Gastrointestinal motility may be impaired after intestinal surgery. Epidural morphine is effective in controlling postoperative pain, but can further reduce gastrointestinal motility. Here, we aimed to investigate the effects of epidural dexmedetomidine on gastrointestinal motility in patients undergoing colonic resection. Seventy-four patients undergoing colonic resection were enrolled in this clinical trial and allocated randomly to treatment with dexmedetomidine (D group) or morphine (M group). The D group received a loading dose epidural administration of 3 ml dexmedetomidine (0.5 μg kg-1) and then a continuous epidural administration of 80 μg dexmedetomidine in 150 ml levobupivacaine (0.125%) at 3 ml h-1 for two days. The M group received a loading dose epidural administration of 3 ml morphine (0.03 mg kg-1) and then a continuous epidural administration of 4.5 mg morphine in 150 ml levobupivacaine at 3 ml h-1 for two days. Verbal rating score (VRS), postoperative analgesic requirements, side effects related to analgesia, the time to postoperative first flatus (FFL) and first feces (FFE) were recorded. VRS and postoperative analgesic requirements were not significantly different between treatment groups. In contrast, the time to FFL and time to FFE were significant longer in M group in comparison to D group (P < 0.05). Moreover, patients in M group had a significantly higher incidence of nausea, vomiting, and pruritus (P < 0.05). No patients showed neurologic deficits in either group. In comparison to morphine, epidural dexmedetomidine is safe and beneficial for the recovery of gastrointestinal motility after colonic resection when used as an adjunct with levobupivacaine for postoperative pain control.
Trial Registration
Chinese Clinical Trial Registry ChiCTR-TRC-14004644 相似文献952.
953.
Kuan-Fu Chen Chung-Hsien Chaou Jing-Yi Jiang Hsueh-Wen Yu Yu-Hsiang Meng Wei-Chen Tang Chin-Chieh Wu 《PloS one》2016,11(4)
IntroductionLipopolysaccharide-binding protein (LBP) is widely reported as a biomarker to differentiate infected from non-infected patients. The diagnostic use of LBP for sepsis remains a matter of debate. We aimed to perform a systematic review and meta-analysis to assess the diagnostic accuracy of serum LBP for sepsis in adult patients.MethodsWe performed a systematic review and meta-analysis to assess the accuracy of LBP for sepsis diagnosis. A systematic search in PubMed and EMBASE for studies that evaluated the diagnostic role of LBP for sepsis through December 2015 was conducted. We searched these databases for original, English language, research articles that studied the diagnostic accuracy between septic and non-septic adult patients. Sensitivity, specificity, and other measures of accuracy, such as diagnostic odds ratio (DOR) and area under the receiver operating characteristic curve (AUC) of LBP were pooled using the Hierarchical Summary Receiver Operating Characteristic (HSROC) method.ResultsOur search returned 53 reports, of which 8 fulfilled the inclusion criteria, accounting for 1684 patients. The pooled sensitivity and specificity of LBP for diagnosis of sepsis by the HSROC method were 0.64 (95% CI: 0.56–0.72) and 0.63 (95% CI: 0.53–0.73), respectively. The value of the DOR was 3.0 (95% CI: 2.0–4.0) and the AUC was 0.68 (95% CI: 0.64–0.72). Meta-regression analysis revealed that cut-off values accounted for the heterogeneity of sensitivity and sample size (> = 150) accounted for the heterogeneity of specificity.ConclusionsBased on the results of our meta-analysis, LBP had weak sensitivity and specificity in the detection of sepsis. LBP may not be practically recommended for clinical utilization as a single biomarker. 相似文献
954.
Fengge Zhang Xiaohui Meng Chenglong Feng Wei Ran Guanghui Yu Yingjun Zhang Qirong Shen 《PloS one》2016,11(3)
Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g−1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application. 相似文献
955.
Zhuo Huang Xiao-Juan Zhong Jiao He Si-Han Jin Han-Du Guo Xiao-Fang Yu Yu-Jue Zhou Xi Li Ming-Dong Ma Qi-Bing Chen Hai Long 《PloS one》2016,11(11)
Late embryogenesis abundant (LEA) proteins have been identified in a wide range of organisms and are believed to play a role in the adaptation of plants to stress conditions. In this study, we performed genome-wide identification of LEA proteins and their coding genes in Moso bamboo (Phyllostachys edulis) of Poaceae. A total of 23 genes encoding LEA proteins (PeLEAs) were found in P. edulis that could be classified to six groups based on Pfam protein family and homologous analysis. Further in silico analyses of the structures, gene amount, and biochemical characteristics were conducted and compared with those of O. sativa (OsLEAs), B. distachyon (BdLEAs), Z. mays (ZmLEAs), S. bicolor (SbLEAs), Arabidopsis, and Populus trichocarpa. The less number of PeLEAs was found. Evolutionary analysis revealed orthologous relationship and colinearity between P. edulis, O. sativa, B. distachyon, Z. mays, and S. bicolor. Analyses of the non-synonymous (Ka) and synonymous (Ks)substitution rates and their ratios indicated that the duplication of PeLEAs may have occurred around 18.8 million years ago (MYA), and divergence time of LEA family among the P. edulis-O. sativa and P. edulis–B. distachyon, P. edulis-S. bicolor, and P. edulis-Z. mays was approximately 30 MYA, 36 MYA, 48 MYA, and 53 MYA, respectively. Almost all PeLEAs contain ABA- and (or) stress-responsive regulatory elements. Further RNA-seq analysis revealed approximately 78% of PeLEAs could be up-regulated by dehydration and cold stresses. The present study makes insights into the LEA family in P. edulis and provides inventory of stress-responsive genes for further functional validation and transgenic research aiming to plant genetic improvement of abiotic stress tolerance. 相似文献
956.
Yan Guo Mary A. Johnson Zara Mehrabian Manoj K. Mishra Rangaramanujam Kannan Neil R. Miller Steven L. Bernstein 《PloS one》2016,11(4)
IntroductionPolyamidoamine dendrimer nanoparticles (~ 4 nanometers) are inert polymers that can be linked to biologically active compounds. These dendrimers selectively target and accumulate in inflammatory cells upon systemic administration. Dendrimer-linked compounds enable sustained release of therapeutic compounds directly at the site of damage. The purpose of this study was to determine if dendrimers can be used to target the optic nerve (ON) ischemic lesion in our rodent and nonhuman primate models of nonarteritic anterior ischemic optic neuropathy (NAION), a disease affecting >10,000 individuals in the US annually, and for which there currently is no effective treatment.MethodsNAION was induced in male Long-Evans rats (rNAION) and in one adult male rhesus monkey (pNAION) using previously described procedures. Dendrimers were covalently linked to near-infrared cyanine-5 fluorescent dye (D-Cy5) and injected both intravitreally and systemically (in the rats) or just systemically (in the monkey) to evaluate D-Cy5 tissue accumulation in the eye and optic nerve following induction of NAION.ResultsFollowing NAION induction, Cy-5 dendrimers selectively accumulated in astrocytes and circulating macrophages. Systemic dendrimer administration provided the best penetration of the ON lesion site when injected shortly after induction. Systemic administration 1 day post-induction in the pNAION model gave localization similar to that seen in the rats.ConclusionsDendrimers selectively target the ischemic ON lesion after induction of both rNAION and pNAION. Systemic nanoparticle-linked therapeutics thus may provide a powerful, targeted and safe approach to NAION treatment by providing sustained and focused treatment of the cells directly affected by ischemia. 相似文献
957.
958.
Guo-ye Guo Sheng-hua Wang Ying Xu Lin Tang Mao-qun Yu Fang Chen 《Genes & genomics.》2016,38(6):557-566
The genus Jatropha (Euphorbiaceae) contains species that are of significant economic and ornamental value. However, Jatropha breeding material is rather limited due to incomplete information regarding phylogenetic relationships among germplasm resources. Phylogenetic analyses were performed based on the internal transcribed spacer of nuclear ribosomal DNA (nrDNA ITS), two chloroplast regions (trnL-F and rbcL), and the combined (ITS+trnL-F+rbcL) dataset among twenty-five specimens representing six key Jatropha species. Phylogenetic relationships of Jatropha were well resolved between subgenus Curcas and subgenus Jatropha, and demonstrated the intermediate position of section Polymorphae among sections of both subgenera. Jatropha curcas and J. integerrima demonstrated a close phylogenetic relationship. The molecular data agreed with the morphological classification that recognized J. multifida and J. podagrica in sec. Peltatae. The distinct intraspecific divergence that occurred in J. curcas could be attributed to restricted gene flow caused by geographical isolation and different ecological conditions. Phylograms produced with trnL-F and rbcL sequence data suggested slow rates of sequence divergence among Jatropha spp., while the ITS gene tree had good resolution suggesting high genetic variation of ITS among Jatropha species. 相似文献
959.
Qianqian Sun Shuangshuang Nie Lingxiao Wang Fan Yang Zhangming Meng Hengyi Xiao Bing Xiang Xiujun Li Xianghui Fu Shuang Wang 《PloS one》2016,11(3)
Aging may be a risk factor for type 2 diabetes in the elderly. Dietary intervention can affect glucose tolerance in adults, which may be due to body composition and islet cell autophagy. The aim of this study was to determine the effects of various dietary interventions on islet cell autophagy. Pancreatic tissue and blood samples were collected from Sprague Dawley rats (14–16 months old, n = 15 for each group) that received a normal diet (ND), a high-fat diet (HFD), or a calorie-restricted diet (CRD). The body weight (BW), visceral fat, serum lipid levels, fasting serum glucose, insulin levels, and β/α cell area were determined in 14-16-(0-w), 16-18-(8-w), and 18-20(16-w)-month-old rats. Pancreatic islet autophagy (LC3B and LAMP2), AP (Acid Phosphatase) and apoptosis (apoptosis index, AI (TUNEL assay) and cleaved caspase-3) were detected using immunohistochemistry, ELISA and western blot. At 16 weeks, the expressions of LC3B, LAMP2 and AP markedly increased in both the HFD (P<0.01) and CRD (P<0.05) groups; however, an increase in the AI (P<0.05), cleaved caspase-3 and Beclin1 expression and a decrease in the expressions of BCL2 and BCLXL (P<0.05) were observed in only the HFD group. FFA, triglyceride levels, HOMA-IR, insulin levels and glucagon levels were significantly increased in the HFD group but decreased in the CRD group at 16 weeks (P<0.05). The degree of islet cell autophagy was potentially regulated by the levels of FFA and islet cell insulin and glucagon, which may have been due to the effects of Beclin1/BCL2. 相似文献
960.
Yumei Zhang Yu Pan Zhixiang Bian Peihua Chen Shijian Zhu Huiyi Gu Liping Guo Chun Hu 《PloS one》2016,11(1)
Here, we studied the underlying mechanism of aldosterone (Aldo)-induced vascular endothelial cell damages by focusing on ceramide. We confirmed that Aldo (at nmol/L) inhibited human umbilical vein endothelial cells (HUVEC) survival, and induced considerable cell apoptosis. We propose that ceramide (mainly C18) production might be responsible for Aldo-mediated damages in HUVECs. Sphingosine-1-phosphate (S1P), an anti-ceramide lipid, attenuated Aldo-induced ceramide production and following HUVEC damages. On the other hand, the glucosylceramide synthase (GCS) inhibitor PDMP or the ceramide (C6) potentiated Aldo-induced HUVEC apoptosis. Eplerenone, a mineralocorticoid receptor (MR) antagonist, almost completely blocked Aldo-induced C18 ceramide production and HUVEC damages. Molecularly, ceramide synthase 1 (CerS-1) is required for C18 ceramide production by Aldo. Knockdown of CerS-1 by targeted-shRNA inhibited Aldo-induced C18 ceramide production, and protected HUVECs from Aldo. Reversely, CerS-1 overexpression facilitated Aldo-induced C18 ceramide production, and potentiated HUVEC damages. Together, these results suggest that C18 ceramide production mediates Aldo-mediated HUVEC damages. MR and CerS-1 could be the two signaling molecule regulating C18 ceramide production by Aldo. 相似文献